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The human gut presents a complex ecosystem harboring trillions of microorganisms living in close association with each other and the host body. Any perturbation or imbalance of the normal gut microbiota may prove detrimental to human health. Enteric infections and treatment with antibiotics pose major threats to gut microbiota health. Recent genomics-driven research has provided insights into the transmission and evolutionary dynamics of major enteric pathogens such as Escherichia coli, Klebsiella pneumoniae, Vibrio cholerae, Helicobacter pylori and Salmonella spp. Studies entailing the identification of various dominant lineages of some of these organisms based on artificial intelligence and machine learning point to the possibility of a system for prediction of antimicrobial resistance (AMR) as some lineages have a higher propensity to acquire virulence and fitness advantages. This is pertinent in the light of emerging AMR being one of the immediate threats posed by pathogenic bacteria in the form of a multi-layered fitness manifesting as phenotypic drug resistance at the level of clinics and field settings. To develop a holistic or systems-level understanding of such devastating traits, present methodologies need to be advanced with the high throughput techniques integrating community and ecosystem/niche level data across different omics platforms. The next major challenge for public health epidemiologists is understanding the interactions and functioning of these pathogens at the community level, both in the gut and outside. This would provide new insights into the dimensions of enteric bacteria in different environments and niches and would have a plausible impact on infection control strategies in terms of tackling AMR. Hence, the aim of this review is to discuss virulence and AMR in Gram-negative pathogens, the spillover of AMR and methodological advancements aimed at addressing it through a unified One Health framework applicable to the farms, the environment, different clinical settings and the human gut., Competing Interests: Declaration of competing interest Given his role as Guest Editor, Prof. Niyaz Ahmed had no involvement in the peer review of this article which was fully delegated to Dr. Fernando Gonzalez Candelas., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

The survival and virulence of Gram-negative bacteria require proper biogenesis and maintenance of the outer membrane (OM), which is densely packed with β-barrel OM proteins (OMPs). Before reaching the OM, precursor unfolded OMPs (uOMPs) must cross the whole cell envelope. A network of periplasmic chaperones and proteases maintains unfolded but folding-competent conformations of these membrane proteins in the aqueous periplasm while simultaneously preventing off-pathway aggregation. These periplasmic proteins utilize different strategies, including conformational heterogeneity, oligomerization, multivalency, and kinetic partitioning, to perform and regulate their functions. Redundant and unique characteristics of the individual periplasmic players synergize to create a protein quality control team capable responding to changing environmental stresses., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024. Published by Elsevier Ltd.)

Currently, multidrug-resistant bacteria are rapidly increasing worldwide because of the misuse or overuse of antibiotics. In particular, few options exist for treating infections caused by long-persisting oxacillin-resistant strains and recently proliferating carbapenem-resistant strains. Therefore, alternative treatments are urgently needed. The antimicrobial peptide (AMP) Lycosin-II is a peptide consisting of 21 amino acids isolated from the venom of the spider Lycosa singoriensis. Lycosin-II showed strong antibacterial activity and biofilm inhibition effects against gram-positive and gram-negative bacteria including oxacillin-resistant Staphylococcus aureus (S. aureus) and meropenem-resistant Pseudomonas aeruginosa (P. aeruginosa) isolated from patients. In addition, Lycosin-II was not cytotoxic against human foreskin fibroblast Hs27 or hemolytic against sheep red blood cells at the concentration of which exerted antibacterial activity. The mechanism of action of Lycosin-II involves binding to lipoteichoic acid and lipopolysaccharide of gram-positive and gram-negative bacterial membranes, respectively, to destroy the bacterial membrane. Moreover, Lycosin-II showed anti-inflammatory effects by inhibiting the expression of pro-inflammatory cytokines that are increased during bacterial infection in Hs27 cells. These results suggest that Lycosin-II can serve as a therapeutic agent against infections with multidrug-resistant strains., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The occult pulmonary infection is the most common complications in elderly patients with type 2 diabetes mellitus (T2DM). Since its etiological characteristics has not been clarified, infection control remains a serious problem for public health. To investigate the prevalence and clinical significance of occult pulmonary infection in elderly T2DM patients, in this study, 573 elderly patients cochallenged with T2DM and community-acquired pulmonary infection from January 2018 to December 2020 were selected in the hospitals and divided into occult pneumonia group (OP, n = 249) and nonoccult pneumonia group (NOP, n = 324) according to the nature of infection. Clinical medical records were analyzed retrospectively to summarize the infection characteristics of elderly diabetics with occult pneumonia. The prevalence of the cases (278/324, 85.8%) in NOP group was not higher than that in OP group (206/249, 82.7%; P > 0.05). Also, there was not significant difference in the distribution of isolated pathogens among the positive patients. The length of hospitalization and mortality of OP patients were significantly higher than those NOP patients. Multivariate logistic regression showed that advanced age, comorbidities, hypothyroidism, senile dementia, and prolonged bed rest were independent risk factors for occult pneumonia in elderly diabetic patients. Therefore, the results demonstrated that the pulmonary infection in elderly patients with diabetes mellitus is often occult. Gram-negative bacteria are the predominant pathogens and cause poor prognosis. Advanced age, comorbidities (senile dementia, hypothyroidism), and prolonged bed rest are the independent risk factors for occult pneumonia., Competing Interests: The authors declare no conflict of interests., (Copyright © 2021 Jian Hua et al.)

Lipids are complex organic compounds made up of carbon, oxygen, and hydrogen. These play a diverse and intricate role in cellular processes like membrane trafficking, protein sorting, signal transduction, and bacterial infections. Both Gram-positive bacteria ( Staphylococcus sp., Listeria monocytogenes, etc .) and Gram-negative bacteria ( Chlamydia sp., Salmonella sp., E. coli , etc.) can hijack the various host-lipids and utilize them structurally as well as functionally to mount a successful infection. The pathogens can deploy with various arsenals to exploit host membrane lipids and lipid-associated receptors as an attachment for toxins' landing or facilitate their entry into the host cellular niche. Bacterial species like Mycobacterium sp. can also modulate the host lipid metabolism to fetch its carbon source from the host. The sequential conversion of host membrane lipids into arachidonic acid and prostaglandin E2 due to increased activity of cPLA-2 and COX-2 upon bacterial infection creates immunosuppressive conditions and facilitates the intracellular growth and proliferation of bacteria. However, lipids' more debatable role is that they can also be a blessing in disguise. Certain host-lipids, especially sphingolipids, have been shown to play a crucial antibacterial role and help the host in combating the infections. This review shed light on the detailed role of host lipids in bacterial infections and the current understanding of the lipid in therapeutics. We have also discussed potential prospects and the need of the hour to help us cope in this race against deadly pathogens and their rapidly evolving stealthy virulence strategies.

Broad antibacterial spectrum, high oral bioavailability and excellent tissue penetration combined with safety and few, yet rare, unwanted effects, have made the quinolones class of antimicrobials one of the most used in inpatients and outpatients. Initially discovered during the search for improved chloroquine-derivative molecules with increased anti-malarial activity, today the quinolones, intended as antimicrobials, comprehend four generations that progressively have been extending antimicrobial spectrum and clinical use. The quinolone class of antimicrobials exerts its antimicrobial actions through inhibiting DNA gyrase and Topoisomerase IV that in turn inhibits synthesis of DNA and RNA. Good distribution through different tissues and organs to treat Gram-positive and Gram-negative bacteria have made quinolones a good choice to treat disease in both humans and animals. The extensive use of quinolones, in both human health and in the veterinary field, has induced a rise of resistance and menace with leaving the quinolones family ineffective to treat infections. This review revises the evolution of quinolones structures, biological activity, and the clinical importance of this evolving family. Next, updated information regarding the mechanism of antimicrobial activity is revised. The veterinary use of quinolones in animal productions is also considered for its environmental role in spreading resistance. Finally, considerations for the use of quinolones in human and veterinary medicine are discussed.

Objective: To identify risk factors for functional decline after hospitalization for Gram-negative bacteremia., Patients and Methods: A prospective cohort study based on a randomized controlled trial conducted between January 1, 2013 and August 31, 2017 in Israel and Italy. Hospitalized patients with Gram-negative bacteremia who survived until day 90 and were not bedridden at baseline were included. The primary end point was functional decline at 90 days., Results: Five hundred and nine patients were included. The median age of the cohort was 71 years (interquartile range [IQR], 60-80 years), 46.4% (236/509) were male and 352 of 509 (69%) patients were independent at baseline. Functional decline at 90 days occurred in 24.4% of patients (124/509). In multivariable analysis; older age (odds ratio [OR], 1.03; for an one-year increment, 95% confidence interval [CI] 1.01-1.05), functional dependence in instrumental activities of daily living at baseline (OR, 4.64; 95% CI 2.5-8.6), low Norton score (OR, 0.87; 95% CI 0.79-0.96) and underlying comorbidities: cancer (OR, 2.01; 95% CI 1.14-3.55) and chronic pulmonary disease (OR, 2.23 95% CI 1.12-4.42) and longer length of hospital stay (OR 1.09; for one-day increment, 95% CI 1.04-1.15) were associated with functional decline. Appropriate empirical antibiotic treatment was associated with lower rates of functional decline within 90 days (OR, 0.4; 95% CI 0.21-0.78)., Conclusions: Patients surviving bloodstream infections have poor long term trajectories after clinical recovery and hospital discharge. This has vast implications for patients, their family members and health policy makers., Competing Interests: The authors have declared that no competing interests exist.

All bacteria produce secreted vesicles that carry out a variety of important biological functions. These extracellular vesicles can improve adaptation and survival by relieving bacterial stress and eliminating toxic compounds, as well as by facilitating membrane remodeling and ameliorating inhospitable environments. However, vesicle production comes with a price. It is energetically costly and, in the case of colonizing pathogens, it elicits host immune responses, which reduce bacterial viability. This raises an interesting paradox regarding why bacteria produce vesicles and begs the question as to whether the benefits of producing vesicles outweigh their costs. In this review, we discuss the various advantages and disadvantages associated with Gram-negative and Gram-positive bacterial vesicle production and offer perspective on the ultimate score. We also highlight questions needed to advance the field in determining the role for vesicles in bacterial survival, interkingdom communication, and virulence., (© 2021 The Authors.)

Background: Peripheral venous catheter (PVC) is the most used vascular access device in medicine, allowing administration of intravenous fluids and medications. Known complications associated with PVC include extravasation, phlebitis and rarely bloodstream infection (BSI). Data regarding PVC-related BSI in children are lacking. Our aim was to evaluate the epidemiology, clinical and microbiologic characteristics of pediatric inpatients with PVC-related BSI., Methods: A retrospective study was conducted in a pediatric tertiary care center. Children with BSI, admitted to general pediatric departments during 2010-2019, were identified and their medical records examined. Patients with BSI and phlebitis were further characterized and included in the analysis. We excluded patients with central venous catheters, other identified source of infection and with BSI upon admission. Data collected included patients' demographics and clinical and microbiologic characteristics., Results: Twenty-seven children with PVC-related BSI were identified and included in the study, consisting of 0.2% of the total BSI cases. Patient's median age was 24 (range, 1.5-213) months, 14/27 (52%) were female and 6 (22%) were previously healthy while 21 (78%) had prior medical conditions. Sixteen (59.3%) patients had Gram-negative BSI and 6 (22.2%) Gram-positive bacteria. Polymicrobial infection occurred in 4 (14.8%) patients and Candida albicans in 1 (3.7%) patient. The most common isolated bacteria were Klebsiella spp and Staphylococcus aureus. Longer dwell-time was a predictor of Gram-negative bacteria., Conclusions: PVC-related BSI due to Gram-negative bacteria was more common than to Gram-positive bacteria. Clinicians should consider an initial broad-spectrum antibiotic coverage for PVC-related BSI in hospitalized pediatric patients., Competing Interests: The authors have no conflicts of interest to disclose., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Male genitourinary tract (MGT) bacterial infections are considered responsible for 15% of male infertility, but the mechanisms underlying decreased semen quality are poorly known. We evaluated in vitro the effect of strains of Gram-negative uropathogenic species (two E.coli strains, three K. pneumoniae strains, P. aeruginosa and E. cloacae) on motility, viability, mitochondrial oxidative status, DNA fragmentation and caspase activity of human spermatozoa. All strains, except P. aeruginosa, reduced significantly sperm motility, with variable effects. Sperm Immobilizing Factor (SIF) was largely responsible for deteriorating effects on sperm motility of E. coli strains since they were completely reverted by knockout of SIF coding recX gene. Sequence alignment for RecX showed the presence of high homologous sequences in K. pneumoniae and E. cloacae but not in P. aeruginosa. These results suggest that, in addition to E.coli, other common uropathogenic Gram-negative bacteria affect sperm motility through RecX products. In addition to sperm motility, the E. coli strain ATCC 35218 also affected sperm viability, and induced caspase activity, oxidative stress and DNA fragmentation suggesting an interspecies variability in the amount and/or type of the produced spermatotoxic factors. In general, our results highlight the need for a careful evaluation of semen infections in the diagnostic process of the infertile man., (© 2021. The Author(s).)

Bacterial flagella are cell surface protein appendages that are critical for motility and pathogenesis. Flagellar filaments are tubular structures constructed from thousands of copies of the protein flagellin, or FliC, arranged in helical fashion. Individual unfolded FliC subunits traverse the filament pore and are folded and sorted into place with the assistance of the flagellar capping protein complex, an oligomer of the FliD protein. The FliD filament cap is a stool-like structure, with its D2 and D3 domains forming a flat head region, and its D1 domain leg-like structures extending perpendicularly from the head towards the inner core of the filament. Here, using an approach combining bacterial genetics, motility assays, electron microscopy and molecular modeling, we define, in numerous Gram-negative bacteria, which regions of FliD are critical for interaction with FliC subunits and result in the formation of functional flagella. Our data indicate that the D1 domain of FliD is its sole functionally important domain, and that its flexible coiled coil region comprised of helices at its extreme N- and C-termini controls compatibility with the FliC filament. FliD sequences from different bacterial species in the head region are well tolerated. Additionally, head domains can be replaced by small peptides and larger head domains from different species and still produce functional flagella.

This study is to determine the incidence and outcome of neonatal gram-negative bacilli (GNB) sepsis in Stockholm, Sweden, and describe bacterial characteristics. This is a retrospective cohort study. All infants with GNB-sepsis between 2006 and 2016 were included and matched with two control groups, with suspected sepsis and uninfected neonates, respectively. Outcome was death before discharge, risk of death within 5 days after sepsis onset, and morbidity. The resistance pattern from all GNB was collected, and all available isolates were subjected to genome typing. All neonates with GNB-sepsis (n = 107) were included, and the cumulative GNB-sepsis incidence was 0.35/1000 live born. The in-hospital mortality was 30/107 (28%). GNB late-onset sepsis (LOS) was associated with an increase in mortality before discharge compared to uninfected controls (OR = 3.9; CI 1.6-9.4) but not versus suspected sepsis. The suspected LOS cases did not statistically differ significantly from uninfected controls. The case fatality rate (CFR) at 5 days was 5/33 (15%) in GNB early-onset sepsis (EOS) and 25/74 (34%) in GNB-LOS. The adjusted hazard for 5 days CFR was higher in GNB-LOS versus uninfected controls (HR = 3.7; CI 1.2-11.2), but no significant difference was seen in GNB-LOS versus suspected sepsis or in suspected sepsis versus controls. ESBL production was seen in 7/107 (6.5%) of the GNB isolates. GNB-LOS was associated with a higher 5 days CFR and in-hospital mortality compared to uninfected controls but not versus suspect sepsis. The incidence of both GNB-EOS and GNB-LOS was lower than previously reported from comparable high-income settings. The occurrence of antibiotic resistance was low., (© 2021. The Author(s).)

Background: Neonatal sepsis accounts for a large proportion of neonatal deaths in sub-Saharan Africa. The lack of access to diagnostic testing and excessively long turnaround times to result contributes to delays in sepsis identification and initiation of appropriate treatment. This study aims to evaluate the novel InTrays COLOREX Screen and extended-spectrum beta-lactamase for rapid identification of bacterial pathogens causing sepsis and detection of resistance., Methods: Neonates with suspected sepsis admitted to the Harare Central Hospital were prospectively enrolled. One blood culture was collected and incubated using the BacT/ALERT automated system. Positive blood cultures with potential pathogens identified by Gram stain were inoculated on the InTray COLOREX Screen and extended-spectrum beta-lactamase culture plates., Results: A total of 216 neonates with suspected sepsis were recruited. Pathogens were isolated from blood cultures in 56 (25.9%) neonates of which 54 were Klebsiella pneumoniae. All K. pneumoniae were resistant to ceftriaxone and 53 (98%) were resistant to gentamicin. Sensitivity and specificity for ceftriaxone-resistant K. pneumoniae detection using InTrays were 100%. InTrays results were interpretable as early as 5-10 hours (median 7 hours, interquartile range 7-7) post blood culture positivity enabling rapid identification and notification of result and leading to a 60% reduction in time to result from blood culture collection., Conclusions: This study shows that the implementation of a novel culture method was feasible and reduced turnaround times for results by 60% compared with standard microbiologic techniques. An impact on patient outcomes and cost-effectiveness of this method needs to be demonstrated., Competing Interests: The authors have no conflicts of interest to disclose., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Iron is an essential element for all microorganisms. Siderophores are low-weight, high-affinity iron chelating molecules produced in response to iron deficiency by Gram-positive and Gram-negative bacteria which also known as essential virulence factors of bacteria. Several studies have indicated that defective production and/or function of these molecules as well as iron acquisition systems in pathogens are associated with a reduction in pathogenicity of bacteria. Because of their potential role in various biological pathways, siderophores have been received special attention as secondary metabolites. Siderophores can detect iron levels in a variety of environments with a biosensor function. In medicine, siderophores are used to deliver antibiotics (Trojan horse strategy) to resistant bacteria and to treat diseases such as cancer and malaria. In this review, we discuss the iron acquisition pathways in Gram-positive and -negative bacteria, importance of siderophore production in pathogenesis of bacteria, classification of siderophores, and main applications of siderophores in medicine and industry., (Copyright © 2021 Elsevier GmbH. All rights reserved.)

Bloodstream infections (BSI) are often caused by drug-resistant pathogens, and novel antimicrobials are needed. We examined the activity of imipenem/relebactam against BSI pathogens from US and Canada: >99% of non-Morganellaceae Enterobacterales, including 100% of MDR isolates, and >94% of Pseudomonas aeruginosa were imipenem/relebactam-susceptible. Imipenem/relebactam could provide an important treatment option., Competing Interests: Declaration of competing interest SHL, MAH, and DFS work for IHMA, which receives funding from Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA for the SMART surveillance program. KY and MRM are employees of Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA, and own stock and options in Merck & Co., Inc., Kenilworth, NJ, USA. The IHMA authors do not have personal financial interests in the sponsor of this manuscript (Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA)., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Biofilms, the predominant growth mode of microorganisms, pose a significant risk to human health. The protective biofilm matrix, typically composed of exopolysaccharides, proteins, nucleic acids, and lipids, combined with biofilm-grown bacteria's heterogenous physiology, leads to enhanced fitness and tolerance to traditional methods for treatment. There is a need to identify biofilm inhibitors using diverse approaches and targeting different stages of biofilm formation. This review discusses discovery strategies that successfully identified a wide range of inhibitors and the processes used to characterize their inhibition mechanism and further improvement. Additionally, we examine the structure-activity relationship (SAR) for some of these inhibitors to optimize inhibitor activity.

Genito-urinary tract infections have a high incidence in the general population, being more prevalent among women than men. These diseases are usually treated with antibiotics, but very frequently, they are recurrent and lead to the creation of resistance and are associated with increased morbidity and mortality. For this reason, it is necessary to develop new compounds for their treatment. In this work, our objective is to review the characteristics of the compounds of a new formulation called Itxasol© that is prescribed as an adjuvant for the treatment of UTIs and composed of β-arbutin, umbelliferon and n-acetyl cysteine. This formulation, based on biomimetic principles, makes Itxasol© a broad-spectrum antibiotic with bactericidal, bacteriostatic and antifungal properties that is capable of destroying the biofilm and stopping its formation. It also acts as an anti-inflammatory agent, without the adverse effects associated with the recurrent use of antibiotics that leads to renal nephrotoxicity and other side effects. All these characteristics make Itxasol© an ideal candidate for the treatment of UTIs since it behaves like an antibiotic and with better characteristics than other adjuvants, such as D-mannose and cranberry extracts.

Introduction: Hepcidin is the systemic master regulator of iron metabolism as it degrades the cellular iron exporter ferroportin. In bacterial infections, hepcidin is upregulated to limit circulating iron for pathogens, thereby increasing iron retention in macrophages. This mechanism withholds iron from extracellular bacteria but could be of disadvantage in infections with intracellular bacteria. We aimed to understand the role of hepcidin in infections with intra- or extracellular bacteria using different hepcidin inhibitors., Methods: For the experiments LDN-193189 and oversulfated heparins were used, which interact with the BMP6-SMAD pathway thereby inhibiting hepcidin expression. We infected male C57BL/6N mice with either the intracellular bacterium Salmonella Typhimurium or the extracellular bacterium Escherichia coli and treated these mice with the different hepcidin inhibitors., Results: Both inhibitors effectively reduced hepcidin levels in vitro under steady state conditions and upon stimulation with the inflammatory signals interleukin-6 or lipopolysaccharide. The inhibitors also reduced hepcidin levels and increased circulating iron concentration in uninfected mice. However, both compounds failed to decrease liver- and circulating hepcidin levels in infected mice and did not affect ferroportin expression in the spleen or impact on serum iron levels. Accordingly, both BMP-SMAD signaling inhibitors did not influence bacterial numbers in different organs in the course of E.coli or S.Tm sepsis., Conclusion: These data indicate that targeting the BMP receptor or the BMP-SMAD pathway is not sufficient to suppress hepcidin expression in the course of infection with both intra- or extracellular bacteria. This suggests that upon pharmacological inhibition of the central SMAD-BMP pathways during infection, other signaling cascades are compensatorily induced to ensure sufficient hepcidin formation and iron restriction to circulating microbes., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Hoffmann, de Souza, Seifert, von Raffay, Haschka, Grubwieser, Grander, Mitterstiller, Nairz, Poli and Weiss.)

Activation of cell-autonomous defense by the immune cytokine interferon-γ (IFN-γ) is critical to the control of life-threatening infections in humans. IFN-γ induces the expression of hundreds of host proteins in all nucleated cells and tissues, yet many of these proteins remain uncharacterized. We screened 19,050 human genes by CRISPR-Cas9 mutagenesis and identified IFN-γ-induced apolipoprotein L3 (APOL3) as a potent bactericidal agent protecting multiple non-immune barrier cell types against infection. Canonical apolipoproteins typically solubilize mammalian lipids for extracellular transport; APOL3 instead targeted cytosol-invasive bacteria to dissolve their anionic membranes into human-bacterial lipoprotein nanodiscs detected by native mass spectrometry and visualized by single-particle cryo-electron microscopy. Thus, humans have harnessed the detergent-like properties of extracellular apolipoproteins to fashion an intracellular lysin, thereby endowing resident nonimmune cells with a mechanism to achieve sterilizing immunity., (Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Quorum sensing (QS) is a method of inter-cellular communication that permits bacteria to dispense information about cell density and to synchronize the gene expression accordingly. Gram-positive and Gram-negative bacteria utilize distinct quorum sensing mechanisms for effective pathogenesis. Virulence factor production by pathogenic bacteria is one of the important traits that is under the control of QS. A growing body of evidence has indicated the role of the nutritional environment notably by carbohydrates in dictating the QS-associated virulence gene regulation. The modulation of QS by carbohydrates mitigates the survival and establishment of the pathogen within its host which in turn leads to an increase in morbidity and mortality. This mini-review throws light on the predilection of pathogenic bacteria to rapidly regulate its QS-linked virulence gene expression based on the changing nutrient levels that assist them in prospering within diverse niches.

Gram-negative pathogens are a rapidly increasing threat to human health worldwide due to high rates of antibiotic resistance and the lack of development of novel antibiotics. The protective cell envelope of gram-negative bacteria is a major permeability barrier that contributes to the problem by restricting the uptake of antibiotics. On the other hand, its unique architecture also makes it a suitable target for antibiotic interference. In particular, essential multiprotein machines that are required for biogenesis of the outer membrane have attracted attention in antibacterial design strategies. Recently, significant progress has been made in the development of inhibitors of the β-barrel assembly machine (BAM) complex. Here, we summarize the current state of drug development efforts targeting the BAM complex in pursuit of new antibiotics., (© The Author(s) 2021. Published by Oxford University Press on behalf of FEMS. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Bacterial processes necessary for adaption to stressful host environments are potential targets for new antimicrobials. Here, we report large-scale transcriptomic analyses of 32 human bacterial pathogens grown under 11 stress conditions mimicking human host environments. The potential relevance of the in vitro stress conditions and responses is supported by comparisons with available in vivo transcriptomes of clinically important pathogens. Calculation of a probability score enables comparative cross-microbial analyses of the stress responses, revealing common and unique regulatory responses to different stresses, as well as overlapping processes participating in different stress responses. We identify conserved and species-specific 'universal stress responders', that is, genes showing altered expression in multiple stress conditions. Non-coding RNAs are involved in a substantial proportion of the responses. The data are collected in a freely available, interactive online resource (PATHOgenex).

Iron is an indispensable metabolic cofactor in both pro- and eukaryotes, which engenders a natural competition for the metal between bacterial pathogens and their human or animal hosts. Bacteria secrete siderophores that extract Fe 3+ from tissues, fluids, cells, and proteins; the ligand gated porins of the Gram-negative bacterial outer membrane actively acquire the resulting ferric siderophores, as well as other iron-containing molecules like heme. Conversely, eukaryotic hosts combat bacterial iron scavenging by sequestering Fe 3+ in binding proteins and ferritin. The variety of iron uptake systems in Gram-negative bacterial pathogens illustrates a range of chemical and biochemical mechanisms that facilitate microbial pathogenesis. This document attempts to summarize and understand these processes, to guide discovery of immunological or chemical interventions that may thwart infectious disease.

The present study examined the chemical composition and antimicrobial and gastrointestinal activity of the essential oils of Elettaria cardamomum (L.) Maton harvested in India (EC-I) and Guatemala (EC-G). Monoterpenes were present in higher concentration in EC-I (83.24%) than in EC-G (73.03%), whereas sesquiterpenes were present in a higher concentration in EC-G (18.35%) than in EC-I (9.27%). Minimum inhibitory concentrations (MICs) of 0.5 and 0.25 mg/mL were demonstrated against Pseudomonas aeruginosa in EC-G and EC-I, respectively, whereas MICs of 1 and 0.5 mg/mL were demonstrated against Escherichia coli in EC-G and EC-I, respectively. The treatment with control had the highest kill-time potential, whereas the treatment with oils had shorter kill-time. EC-I was observed to be more potent in the castor oil-induced diarrhea model than EC-G. At 100 and 200 mg/kg, P.O., EC-I exhibited 40% and 80% protection, respectively, and EC-G exhibited 20% and 60% protection, respectively, in mice, whereas loperamide (10 mg/kg, i.p., positive control) exhibited 100% protection. In the in vitro experiments, EC-I inhibited both carbachol (CCh, 1 µM) and high K + (80 mM)-induced contractions at significantly lower concentrations than EC-G. Thus, EC-I significantly inhibited P. aeruginosa and E. coli and exhibited more potent antidiarrheal and antispasmodic effects than EC-G.

Many gram-negative bacteria use type IV secretion systems to deliver effector molecules to a wide range of target cells. These substrate proteins, which are called type IV secreted effectors (T4SE), manipulate host cell processes during infection, often resulting in severe diseases or even death of the host. Therefore, identification of putative T4SEs has become a very active research topic in bioinformatics due to its vital roles in understanding host-pathogen interactions. PSI-BLAST profiles have been experimentally validated to provide important and discriminatory evolutionary information for various protein classification tasks. In the present study, an accurate computational predictor termed iT4SE-EP was developed for identifying T4SEs by extracting evolutionary features from the position-specific scoring matrix and the position-specific frequency matrix profiles. First, four types of encoding strategies were designed to transform protein sequences into fixed-length feature vectors based on the two profiles. Then, the feature selection technique based on the random forest algorithm was utilized to reduce redundant or irrelevant features without much loss of information. Finally, the optimal features were input into a support vector machine classifier to carry out the prediction of T4SEs. Our experimental results demonstrated that iT4SE-EP outperformed most of existing methods based on the independent dataset test.

Antimicrobial resistance in neonatal sepsis is rising, yet mechanisms of resistance that often spread between species via mobile genetic elements, ultimately limiting treatments in low- and middle-income countries (LMICs), are poorly characterized. The Burden of Antibiotic Resistance in Neonates from Developing Societies (BARNARDS) network was initiated to characterize the cause and burden of antimicrobial resistance in neonatal sepsis for seven LMICs in Africa and South Asia. A total of 36,285 neonates were enrolled in the BARNARDS study between November 2015 and December 2017, of whom 2,483 were diagnosed with culture-confirmed sepsis. Klebsiella pneumoniae (n = 258) was the main cause of neonatal sepsis, with Serratia marcescens (n = 151), Klebsiella michiganensis (n = 117), Escherichia coli (n = 75) and Enterobacter cloacae complex (n = 57) also detected. We present whole-genome sequencing, antimicrobial susceptibility and clinical data for 916 out of 1,038 neonatal sepsis isolates (97 isolates were not recovered from initial isolation at local sites). Enterobacterales (K. pneumoniae, E. coli and E. cloacae) harboured multiple cephalosporin and carbapenem resistance genes. All isolated pathogens were resistant to multiple antibiotic classes, including those used to treat neonatal sepsis. Intraspecies diversity of K. pneumoniae and E. coli indicated that multiple antibiotic-resistant lineages cause neonatal sepsis. Our results will underpin research towards better treatments for neonatal sepsis in LMICs.

Previous studies have shown that ELAVL1 plays multiple roles, but its overall biological function remains ill-defined. Here we clearly demonstrated that zebrafish ELAVL1a was a lipoteichoic acid (LTA)- and LPS-binding protein abundantly stored in the eggs/embryos of zebrafish. ELAVL1a acted not only as a pattern recognition receptor, capable of identifying LTA and LPS, as well as bacteria, but also as an effector molecule, capable of inhibiting the growth of Gram-positive and -negative bacteria. Furthermore, we reveal that the C-terminal 62 residues of ELAVL1a positioned at 181-242 were indispensable for ELAVL1a antibacterial activity. Additionally, site-directed mutagenesis revealed that the hydrophobic residues Val192/Ile193, as well as the positively charged residues Arg203/Arg204, were the functional determinants contributing to the antimicrobial activity of rELAVL1a. Importantly, microinjection of rELAVL1a into embryos markedly promoted their resistance against pathogenic Aeromonas hydrophila challenge, and this pathogen-resistant activity was considerably reduced by co-injection of anti-ELAVL1a antibody or by knockdown with morpholino for elavl1a. Collectively, our results indicate that ELAVL1a is a maternal immune factor that can protect zebrafish embryos from bacterial infection. This work also provides another angle for understanding the biological roles of ELAVL1a.

Rhamnose is an important 6-deoxy sugar present in many natural products, glycoproteins, and structural polysaccharides. Whilst predominantly found as the l-enantiomer, instances of d-rhamnose are also found in nature, particularly in the Pseudomonads bacteria. Interestingly, rhamnose is notably absent from humans and other animals, which poses unique opportunities for drug discovery targeted towards rhamnose utilizing enzymes from pathogenic bacteria. Whilst the biosynthesis of nucleotide-activated rhamnose (NDP-rhamnose) is well studied, the study of rhamnosyltransferases that synthesize rhamnose-containing glycoconjugates is the current focus amongst the scientific community. In this review, we describe where rhamnose has been found in nature, as well as what is known about TDP-β-l-rhamnose, UDP-β-l-rhamnose, and GDP-α-d-rhamnose biosynthesis. We then focus on examples of rhamnosyltransferases that have been characterized using both in vivo and in vitro approaches from plants and bacteria, highlighting enzymes where 3D structures have been obtained. The ongoing study of rhamnose and rhamnosyltransferases, in particular in pathogenic organisms, is important to inform future drug discovery projects and vaccine development., (© 2021 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.)

Green synthesis of nanoparticles using citrus peel extracts is known to be environmentally friendly and non-toxic when compared to chemical methods. In this study, different citrus peel extracts obtained with the solvents acetone and distilled water were used to synthesize copper oxide nanoparticles (CuONPs). The nanoparticles were characterized using cyclic voltammetry, ultraviolet-visible spectroscopy, energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). The absorption spectrum of CuONPs prepared with acetone exhibited characteristic peaks at the wavelengths between 280-293 nm, while those with distilled water had peaks at 290 nm. The acetone-synthesized CuONPs were spherical while those produced using distilled water were rod-shaped. Based on EDS, the analysis revealed a trace spectrum of CuO nanoparticles with different weight compositions that varied with the type of citrus peel and solvent used. FTIR measurements were carried out in the range of 500-4000 cm -1 for citrus peel extract mediated CuONPs. The spectra had five vibrations occurring at approximately 473, 477, 482, 607 and 616 cm -1 for all samples, which can be attributed to the vibrations of CuO, validating the formation of highly pure CuONPs.

It is predicted that the antibiotic resistance crisis will result in an annual death rate of 10 million people by the year 2050. To grapple with the challenges of the impending crisis, there is an urgent need for novel and rapid diagnostic tools. In this study, we developed a novel monoclonal antibody-named mAb-EspB-B7-that targets the EspB protein, a component within the bacterial type 3 secretion system (T3SS), which is mainly expressed in Gram-negative pathogens and is essential for bacterial infectivity. We found that mAb-EspB-B7 has high affinity and specificity toward recombinant and native EspB proteins; is stable over a range of pH levels, temperatures, and salt concentrations; and retains its functionality in human serum. We identified the epitope for mAb-EspB-B7 and validated it by competitive enzyme-linked immunosorbent assay (ELISA). Since this epitope is conserved across several T3SS-harboring pathogens, mAb-EspB-B7 holds great potential for development as an active component in precise and rapid diagnostic tools that can differentiate between commensal and pathogenic bacterial strains. To this end, we integrated the well-characterized monoclonal antibody into an electrochemical biosensor and demonstrated its high specificity and sensitivity capabilities in detecting pathogenic bacterial T3SS-associated antigens as well as intact bacteria. We foresee that in the near future it will be possible to design and develop a point-of-care biosensor with multiplexing capabilities for the detection of a panel of pathogenic bacteria.

Background: Patients with sickle cell disease are at higher risk of infections with encapsulated bacteria due to immature immune responses and functional asplenia. We aimed to study our patient population for the emergence of gram-negative organisms other than Salmonella as the cause of osteomyelitis and document a vast decrease in Streptococcus pneumoniae bacteremia rates., Methods: We conducted a retrospective chart review of 158 patients with sickle cell disease registered at our hospital. Over a period of 13 years, every patient presenting to the emergency department (ED) with fever had their medical record reviewed for blood cultures, wound cultures, and magnetic resonance imaging results for osteomyelitis., Results: The number of patients presenting to the ED with fever was 105, with 581 febrile episodes and 893 blood cultures. Among those, no culture grew Streptococcus pneumoniae, 14 grew coagulase-negative staphylococci (1.5%), one grew Salmonella enterica Paratyphi B, and three grew Salmonella enterica group C (in the same patient). The total number of osteomyelitis episodes in patients with sickle cell disease presenting with fever and documented by imaging was nine (1.5%). In patients with osteomyelitis, organisms were isolated in four patients (44%), including Enterobacter cloacae, Bacteroides, Pseudomonas aeruginosa, and Salmonella enterica group C., Conclusions: Immunization against Streptococcus pneumoniae and the use of prophylactic penicillin has virtually eliminated pneumococcal bacteremia among our patients. We observed the emergence of gram-negative organisms other than Salmonella as the cause of osteomyelitis in patients with sickle cell disease., (© 2020 Wiley Periodicals LLC.)

Chronic wound biofilm infections are a threat to the population with respect to morbidity and mortality. The presence of multidrug-resistant bacterial pathogens in chronic wound renders the action of antibiotics and antibiofilm agents difficult. Therefore an alternative therapy is essential for reducing bacterial biofilm burden. In this scenario, the peptide-based antibiofilm therapy for chronic wound biofilm management seeks more attention. A synthetic peptide with a broad range of antibiofilm activity against preformed and established biofilms, having the ability to kill multispecies bacteria within biofilms and possessing combinatorial activity with other antimicrobial agents, provides significant insights. In this review, we portray the possibilities and difficulties of peptide-mediated treatment in chronic wounds biofilm management and how it can be clinically translated into a product., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Increasing antibiotic resistance in multidrug-resistant (MDR) Gram-negative bacteria (MDR-GNB) presents significant health problems worldwide, since the vital available and effective antibiotics, including; broad-spectrum penicillins, fluoroquinolones, aminoglycosides, and β-lactams, such as; carbapenems, monobactam, and cephalosporins; often fail to fight MDR Gram-negative pathogens as well as the absence of new antibiotics that can defeat these "superbugs". All of these has prompted the reconsideration of old drugs such as polymyxins that were reckoned too toxic for clinical use. Only two polymyxins, polymyxin E (colistin) and polymyxin B, are currently commercially available. Colistin has re-emerged as a last-hope treatment in the mid-1990s against MDR Gram-negative pathogens due to the development of extensively drug-resistant GNB. Unfortunately, rapid global resistance towards colistin has emerged following its resurgence. Different mechanisms of colistin resistance have been characterized, including intrinsic, mutational, and transferable mechanisms.In this review, we intend to discuss the progress over the last two decades in understanding the alternative colistin mechanisms of action and different strategies used by bacteria to develop resistance against colistin, besides providing an update about what is previously recognized and what is novel concerning colistin resistance.

Objectives Severe or critical COVID-19 is associated with intensive care unit admission, increased secondary infection rate, and would lead to significant worsened prognosis. Risks and characteristics relating to secondary infections in severe COVID-19 have not been described. Methods Severe and critical COVID-19 patients from Shanghai were included. We collected lower respiratory, urine, catheters, and blood samples according to clinical necessity and culture and mNGS were performed. Clinical and laboratory data were archived. Results We found 57.89% (22/38) patients developed secondary infections. The patient receiving invasive mechanical ventilation or in critical state has a higher chance of secondary infections ( P <0.0001). The most common infections were respiratory, blood-stream and urinary infections, and in respiratory infections, the most detected pathogens were gram-negative bacteria (26, 50.00%), following by gram-positive bacteria (14, 26.92%), virus (6, 11.54%), fungi (4, 7.69%), and others (2, 3.85%). Respiratory Infection rate post high flow, tracheal intubation, and tracheotomy were 12.90% (4/31), 30.43% (7/23), and 92.31% (12/13) respectively. Secondary infections would lead to lower discharge rate and higher mortality rate. Conclusion Our study originally illustrated secondary infection proportion in severe and critical COVID-19 patients. Culture accompanied with metagenomics sequencing increased pathogen diagnostic rate. Secondary infections risks increased after receiving invasive respiratory ventilations and intravascular devices, and would lead to a lower discharge rate and a higher mortality rate.

Objective: Silver nanoparticles synthesized using Rhodomyrtus tomentosa leaf extract and silk sericin were used to functionalize carbopol 940 gel for topical applications., Results: UV-vis spectra presented surface plasmon resonance at 426 nm, transmission electron microscopy revealed that nanoparticles were spherical with an average size of 25-50 nm. X-ray diffraction presented crystalline silver nanoparticles with zeta potential of ≈ - 30 mV. FTIR spectra showed a reduction of silver nitrate indicated by the shift in -OH at 2958 cm -1 . The silver nanoparticle demonstrated broad-spectrum antimicrobial activity against Gram-positive, Gram-negative and fungi with MIC ranging between 0.26 and 2.10 μg mL -1 , respectively. MIC of hydrogel ranged between 1.05-2.10 μg mL -1 with cell viability of 89%. Spreadability and extrudability of gel were 9.3 ± 0.85 s and 19.85 ± 0.03%, respectively with first order of fickian diffusion., Conclusions: The silver nanoparticle gel exhibited an effective antimicrobial property, hence can be exploited for topical applications.

Sensing of microbes activates the innate immune system, depending on functional mitochondria. However, pathogenic bacteria inhibit mitochondrial activity by delivering toxins via outer membrane vesicles (OMVs). How macrophages respond to pathogenic microbes that target mitochondria remains unclear. Here, we show that macrophages exposed to OMVs from Neisseria gonorrhoeae, uropathogenic Escherichia coli and Pseudomonas aeruginosa induce mitochondrial apoptosis and NLRP3 inflammasome activation. OMVs and toxins that cause mitochondrial dysfunction trigger inhibition of host protein synthesis, which depletes the unstable BCL-2 family member MCL-1 and induces BAK-dependent mitochondrial apoptosis. In parallel with caspase-11-mediated pyroptosis, mitochondrial apoptosis and potassium ion efflux activate the NLRP3 inflammasome after OMV exposure in vitro. Importantly, in the in vivo setting, the activation and release of interleukin-1β in response to N. gonorrhoeae OMVs is regulated by mitochondrial apoptosis. Our data highlight how innate immune cells sense infections by monitoring mitochondrial health.

Background: Poor oral health is an independent risk factor for upper aerodigestive tract cancers, including esophageal squamous cell carcinoma (ESCC). The pattern recognition receptor Toll-like receptor 4 (TLR4) recognizes lipopolysaccharide in the cell walls of Gram-negative periodontal pathogens associated with the development and progression of ESCC. It is, therefore, plausible that TLR4 plays a crucial role in the pathogenesis of ESCC., Methods: We used an ESCC tissue microarray to confirm expression of TLR4 in patients with ESCC and to determine whether TLR4 expression status correlates with the clinicopathological features of these patients or their prognosis after esophagectomy. We also tested whether the combined expression statuses of TLR4 and TLR3 better correlate with prognosis in these patients than either parameter alone., Results: Clinical ESCC samples from all 177 patients tested showed expression of TLR4. Moreover, high TLR4 expression (3 + and 2 +) correlated with poorer 5-year overall survival after esophagectomy than lower TLR4 expression (1 +) (p = 0.0491). Patients showing high TLR4 expression tended to have a poorer prognosis whether treated with surgery alone or with surgery and adjuvant chemotherapy. Univariate and multivariate analyses showed TLR4 expression status to be an independent prognostic factor affecting 5-year overall survival. Patients exhibiting high TLR4 expression with low TLR3 expression had a much poorer prognosis than other patients (p = < 0.0001)., Conclusion: High TLR4 expression predicts a poor prognosis in advanced thoracic ESCC patients after esophagectomy.

Background: Studies have investigated risk factors for infections by specific species of carbapenem-resistant Gram-negative bacilli (CR-GNB), but few considered the group of GNB species and most of them were performed in the setting of bacteremia or hospital infection. This study was implemented to identify risk factors for sepsis by CR- and carbapenem-susceptible (CS) GNB in intensive care unit (ICU) patients to improve management strategies for CR-GNB sepsis., Methods: We developed a case-case-control study from a prospective cohort of patients with systemic inflammatory response syndrome (SIRS), sepsis-2 or sepsis-3 criteria in which blood and other sample cultures were collected and antimicrobial therapy was instituted, in an adult clinical-surgical ICU, at tertiary public hospital in Rio de Janeiro, from August 2015 through March 2017., Results: Among the total of 629 ICU admissions followed by 7797 patient-days, after applying inclusion and exclusion criteria we identified 184 patients who developed recurrent or single hospital-acquired sepsis. More than 90% of all evaluable cases of sepsis and 87% of control group fulfilled the modified sepsis-3 definition. Non-fermenting bacilli and ventilator-associated pneumonia predominated as etiology and source of CR-GNB sepsis. While Enterobacteriaceae and intra-abdominal surgical site plus urinary-tract infections prevailed in CS-GNB than CR-GNB sepsis. Carbapenemase production was estimated in 76% of CR-GNB isolates. Multivariate logistic regression analysis revealed previous infection (mostly hospital-acquired bacterial infection or sepsis) (OR = 4.28; 95% CI 1.77-10.35), mechanical ventilation (OR = 4.21; 95% CI 1.17-15.18), carbapenem use (OR = 3.42; 95% CI 1.37-8.52) and length of hospital stay (OR = 1.03; 95% CI 1.01-1.05) as independent risk factors for sepsis by CR-GNB. While ICU readmission (OR = 6.92; 95% CI 1.72-27.78) and nosocomial diarrhea (OR = 5.32; 95% CI 1.07-26.45) were factors associated with CS-GNB sepsis., Conclusions: The investigation of recurrent and not only bacteremic episodes of sepsis was the differential of this study. The results are in agreement with the basic information in the literature. This may help improve management strategies and future studies on sepsis by CR-GNB.

Background: Extended-spectrum beta-lactamase (ESBL)-producing Gram-negative bacteria have become a serious threat to global health. Their rapid spread is associated with high mortality due to ineffective antibiotic treatment. To date a regular surveillance of multidrug-resistant (MDR) pathogens in Ethiopia is not established. For this report, published data regarding ESBL-producing bacteria in different health facilities of Ethiopia were reviewed., Methods: This study collates data from published information on the rates and clinical implications of infection with ESBL-producing Gram-negative bacteria in Ethiopia. A systematic literature search was conducted using PubMed, PubMed Central, Medline, Science Direct and Google scholar from October 2018 to March 2019. Eligible studies were identified by applying quality criteria. The pooled proportion of ESBL-producing Gram-negative bacteria was estimated based on a random effect model. The publication bias and the variation in proportion estimates attributed to heterogeneity were assessed., Results: Fourteen studies with relevant data were included in the review. In total, 1649 Gram-negative bacteria isolated from 5191 clinical samples were included. The pooled proportion estimate of ESBL-producing Gram-negative bacteria was 50% (95% CI: 47.7-52.5%. Data showed a high level of heterogeneity (I 2  = 95%, P <  0.01). ESBL rates varied by species; 65.7% (263/400) in Klebsiella spp., 48.4% (90/186) in Salmonella spp., and 47.0% (383/815) in E. coli. ESBL-encoding genes were reported in 81 isolates: 67 isolates harbored the CTX-M-1 group and 14 isolates TEM. The mortality associated with infections by bacteria resistant to third generation cephalosporins has rarely been investigated. However, two studies reported a mortality of 33.3% (1/3) and 100% (11/11)., Conclusions: In this meta-analysis, the pooled prevalence of ESBL-producing pathogens is alarmingly high. Data on mortality rates is scarce. This highlights the need for establishing and upgrading clinical microbiology laboratories in Ethiopia for routine antibiotic susceptibility testing and extended surveillance of multidrug resistance.

Antimicrobial peptides (AMPs) selectively kill bacteria by disrupting their cell membranes, and are promising compounds to fight drug-resistant microbes. Biophysical studies on model membranes have characterized AMP/membrane interactions and the mechanism of bilayer perturbation, showing that accumulation of cationic peptide molecules in the external leaflet leads to the formation of pores ("carpet" mechanism). However, similar quantitative studies on real cells are extremely limited. Here, we investigated the interaction of the dansylated PMAP23 peptide (DNS-PMAP23) with a Gram-positive bacterium, showing that 10 7 bound peptide molecules per cell are needed to kill it. This result is consistent with our previous finding for Gram-negative strains, where a similar high threshold for killing was determined, demonstrating the general relevance of the carpet model for real bacteria. However, in the case of the Gram-positive strain, this number of molecules even exceeds the total surface available on the bacterial membrane. The high affinity of DNS-PMAP23 for the anionic teichoic acids of the Gram-positive cell wall, but not for the lipopolysaccharides of Gram-negative bacteria, provides a rationale for this finding. To better define the role of anionic lipids in peptide/cell association, we studied DNS-PMAP23 interaction with E. coli mutant strains lacking phosphatidylglycerol and/or cardiolipin. Surprisingly, these strains showed a peptide affinity similar to that of the wild type. This finding was rationalized by observing that these bacteria have an increased content of other anionic lipids, thus maintaining the total membrane charge essentially constant. Finally, studies of DNS-PMAP23 association to dead bacteria showed an affinity an order of magnitude higher compared to that of live cells, suggesting strong peptide binding to intracellular components that become accessible after membrane perturbation. This effect could play a role in population resistance to AMP action, since dead bacteria could protect the surviving cells by sequestering significant amounts of peptide molecules. Overall, our data indicate that quantitative studies of peptide association to bacteria can lead to a better understanding of the mechanism of action of AMPs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The present work investigated the effect of camel's fetal fluids on a variety of bacterial and fungal pathogens. Ten samples of camel's amniotic and allantoic fluids were collected aseptically during parturition and their antimicrobial activities were evaluated by disc diffusion method and minimum inhibitory concentration (MIC) assay. The majority of tested pathogens were inhibited by both fluids up to 25% concentration. The fluids showed zones of inhibition ranging from 8 to 30 mm. The most pronounced inhibition was detected for Staphylococcus aureus, Listeria monocytogenes, Klebsiella pneumonia, and Aspergillus niger but the weak inhibition was obtained for Enterococcus faecalis, Bacillus subtilis, and Candida albicans. Also, the MIC values of amniotic fluids (0.25-2 μg/ml) against Gram-positive bacteria and yeast were lower than the values of allantoic fluids (2-8 μg/ml). But in Gram-negative bacteria and molds, the MIC values of allantoic fluids (0.5-2 μg/ml) were the lowermost. Mucor circinelloides was the only pathogen that resisted both fluids. Analysis of fluid samples revealed the presence of several factors that are known to act as antimicrobial. All tested camel's fetal fluids harbored immunoglobulins, complements, and transferrin. Lysozyme was present in only one of 10 examined samples. We firstly report the prevalence of a profound in-vitro antimicrobial activity of camel's fetal fluids. This activity encourages their use as therapeutic alternative agents to overcome multidrug resistance problems.

All antibiotics have to engage bacterial amphiphilic barriers such as the lipopolysaccharide-rich outer membrane or the phospholipid-based inner membrane in some manner, either by disrupting them outright and/or permeating them and thereby allow the antibiotic to get into bacteria. There is a growing class of cyclic antibiotics, many of which are of bacterial origin, that exhibit activity against Gram-negative bacteria, which constitute an urgent problem in human health. We examine a diverse collection of these cyclic antibiotics, both natural and synthetic, which include bactenecin, polymyxin B, octapeptin, capreomycin, and Kirshenbaum peptoids, in order to identify what they have in common when they interact with bacterial lipid membranes. We find that they virtually all have the ability to induce negative Gaussian curvature (NGC) in bacterial membranes, the type of curvature geometrically required for permeation mechanisms such as pore formation, blebbing, and budding. This is interesting since permeation of membranes is a function usually ascribed to antimicrobial peptides (AMPs) from innate immunity. As prototypical test cases of cyclic antibiotics, we analyzed amino acid sequences of bactenecin, polymyxin B, and capreomycin using our recently developed machine-learning classifier trained on α-helical AMP sequences. Although the original classifier was not trained on cyclic antibiotics, a modified classifier approach correctly predicted that bactenecin and polymyxin B have the ability to induce NGC in membranes, while capreomycin does not. Moreover, the classifier was able to recapitulate empirical structure-activity relationships from alanine scans in polymyxin B surprisingly well. These results suggest that there exists some common ground in the sequence design of hybrid cyclic antibiotics and linear AMPs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier B.V.)

Background: Pneumonia is a major complication leading to death after stroke. The risk factors of pneumonia in convalescent patients who have experienced stroke remain poorly defined., Methods: To identify the risk factors of pneumonia, we applied logistic regression as a statistical method using SPSS23.0 statistical software, based on a sample of 380 patients. And statistical description method was used to analyze pathogens' characteristics and drug resistance., Results: Ultimately, the obtained logistic model has statistical significance (χ 2 (13) = 91.560, P <0.0005). The sensitivity of the model is 41.7%, the specificity is 97.6%, the positive predictive value is 76.9%, and the negative predictive value is 89.8%. The Barthel index (BI) (OR=1.97, 95% CI: 1.01-3.87), basic lung diseases (OR=4.24, 95% CI: 1.02-17.61), trachea ventilation (OR=6.56, 95% CI: 1.18-36.34), feeding tube (OR=6.06, 95% CI: 2.59-14.18), and hypoproteinemia (OR=3.97, 95% CI: 1.56-10.10) were statistically significant (P<0.05). Among patients who have pneumonia, the proportion of gram-positive bacteria, gram-negative bacteria and fungal infection is 10.00%, 54.29%, 5.71% respectively. The study most frequently isolated Pseudomonas aeruginosa (18.57%), followed by Acinetobacter baumannii (10.00%,) and Klebsiella pneumoniae (10.00%). The drug resistance rate of Pseudomonas aeruginosa, Acinetobacter baumannii and Klebsiella pneumoniae to different antibiotics ranged from 0.00-37.77%, 0.00-85.71% and 0.00-57.14%, respectively., Conclusions: The lower BI scores, basic lung diseases, trachea ventilation, tube feeding, and hypoproteinemia are independent risk factors of pneumonia among convalescent patients with stroke. The main pathogens that caused pneumonia were gram-negative bacteria, and such organisms have different degrees of resistance to drugs., Competing Interests: Declaration of Competing Interest We declare there to be no conflicts of interest., (Copyright © 2020. Published by Elsevier Inc.)

Antimicrobial peptides (AMPs) play an important role in the host defense against various microbes. One of the most efficient human AMPs is the human beta defensin-3 (hBD-3) which is produced by, e.g. keratinocytes and lung epithelial cells. However, the structure-function relationship for AMPs and in particular for defensins with their typical three disulfide bonds is still poorly understood. In this study the importance of the three disulfide bonds for the activity of the AMPs is investigated with biological assays and with biophysical experiments utilizing different membrane reconstitution systems. The activities of natural hBD-3, hBD-3-c (cyclic variant with one disulfide bond), and hBD-3-l (linear variant without disulfide bonds) and fragments thereof were tested against specific Gram-negative bacteria. Furthermore, hemolytic and cytotoxic activities were analyzed as well as the potency to neutralize immune cell stimulation of lipopolysaccharide (LPS). Experiments using reconstituted lipid matrices composed of phospholipids or LPS purified from the respective Gram-negative bacteria, showed that the membrane activity of all three hBD-3 peptides is decisive for their capability to kill bacteria and to neutralize LPS. In most of the test systems the linear hBD-3-l showed the highest activity. It was also the only peptide significantly active against polymyxin B-resistant Proteus mirabilis R45. However, the stability of hBD-3 against protease activity decreases with decreasing number of disulfide bonds. This study demonstrates that the refining of AMP structures can generate more active compounds against certain strains., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The par pAD1 locus was the first type I toxin-antitoxin (TA) system described in Gram-positive bacteria and was later determined to be the founding member of a widely distributed family of plasmid- and chromosomally encoded TA systems. Indeed, homology searches revealed that the toxin component, Fst pAD1 , is a member of the Fst/Ldr superfamily of peptide toxins found in both Gram-positive and Gram-negative bacteria. Regulation of the Fst and Ldr toxins is distinct in their respective Gram-positive and Gram-negative hosts, but the effects of ectopic over-expression are similar. While, the plasmid versions of these systems appear to play the canonical role of post-segregational killing stability mechanisms, the function of the chromosomal systems remains largely obscure. At least one member of the family has been suggested to play a role in pathogenesis in Staphylococcus aureus , while the regulation of several others appear to be tightly integrated with genes involved in sugar metabolism. After a brief discussion of the regulation and function of the foundational par pAD1 locus, this review will focus on the current information available on potential roles of the chromosomal homologs.

Objective: Lack of ideal mathematical models to qualify and quantify both pathogenicity, and virulence is a dreadful setback in development of new antimicrobials and vaccines against resistance pathogenic microorganisms. Hence, the modified arithmetical formula of Reed and Muench has been integrated with other formulas and used to determine bacterial colony forming unit/viral concentration, virulence and immunogenicity., Results: Microorganisms' antigens tested are Staphylococcus aureus, Streptococcus pneumoniae, Pseudomonas aeruginosa in mice and rat, Edwardsiella ictaluri, Aeromonas hydrophila, Aeromonas veronii in fish, New Castle Disease virus in chicken, Sheep Pox virus, Foot-and-Mouth Disease virus and Hepatitis A virus in vitro, respectively. The LC 50 s for the pathogens using different routes of administrations are 1.93 × 10 3 (sheep poxvirus) and 1.75 × 10 10 for Staphylococcus aureus (ATCC29213) in rat, respectively. Titer index (TI) equals N log 10 LC 50 and provides protection against lethal dose in graded fashion which translates to protection index. N is the number of vaccine dose that could neutralize the LC 50 . Hence, parasite inoculum of 10 3 to 10 11 may be used as basis for determination of LC 50 and median bacterial concentrations (BC 50 ).Pathogenic dose for immune stimulation should be sought at concentration about LC 10 .

In diagnostics of infectious diseases, matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS) can be applied for the identification of pathogenic microorganisms. However, to achieve a trustworthy identification from MALDI-TOF MS data, a significant amount of biomass should be considered. The bacterial load that potentially occurs in a sample is therefore routinely amplified by culturing, which is a time-consuming procedure. In this paper, we show that culturing can be avoided by conducting MALDI-TOF MS on individual bacterial cells. This results in a more rapid identification of species with an acceptable accuracy. We propose a deep learning architecture to analyze the data and compare its performance with traditional supervised machine learning algorithms. We illustrate our workflow on a large data set that contains bacterial species related to urinary tract infections. Overall we obtain accuracies up to 85% in discriminating five different species.

The capacity of pathogenic microorganisms to adhere to host cells and avoid clearance by the host immune system is the initial and most decisive step leading to infections. Bacteria have developed different strategies to attach to diverse host surface structures. One important strategy is the adhesion to extracellular matrix (ECM) proteins (e.g., collagen, fibronectin, laminin) that are highly abundant in connective tissue and basement membranes. Gram-negative bacteria express variable outer membrane proteins (adhesins) to attach to the host and to initiate the process of infection. Understanding the underlying molecular mechanisms of bacterial adhesion is a prerequisite for targeting this interaction by "anti-ligands" to prevent colonization or infection of the host. Future development of such "anti-ligands" (specifically interfering with bacteria-host matrix interactions) might result in the development of a new class of anti-infective drugs for the therapy of infections caused by multidrug-resistant Gram-negative bacteria. This review summarizes our current knowledge about the manifold interactions of adhesins expressed by Gram-negative bacteria with ECM proteins and the use of this information for the generation of novel therapeutic antivirulence strategies.

Adhesion is the initial step in the infection process of gram-negative bacteria. It is usually followed by the formation of biofilms that serve as a hub for further spread of the infection. Type V secretion systems engage in this process by binding to components of the extracellular matrix, which is the first step in the infection process. At the same time they provide protection from the immune system by either binding components of the innate immune system or by establishing a physical layer against aggressors. Trimeric autotransporter adhesins (TAAs) are of particular interest in this family of proteins as they possess a unique structural composition which arises from constraints during translocation. The sequence of individual domains can vary dramatically while the overall structure can be very similar to one another. This patchwork approach allows researchers to draw conclusions of the underlying function of a specific domain in a structure-based approach which underscores the importance of solving structures of yet uncharacterized TAAs and their individual domains to estimate the full extent of functions of the protein a priori. Here, we describe recent advances in understanding the translocation process of TAAs and give an overview of structural motifs that are unique to this class of proteins. The role of BpaC in the infection process of Burkholderia pseudomallei is highlighted as an exceptional example of a TAA being at the centre of infection initiation.

Introduction : The emergence of multi- and pan-drug-resistant bacteria represents a global crisis that calls for the development of alternative anti-infective strategies. These comprise anti-virulence approaches, which target pathogenicity without exerting a bacteriostatic or bactericidal effect and are claimed to reduce the development of resistance. Because in many pathogens, quorum-sensing (QS) systems control the expression of virulence factors, interference with QS, or quorum-quenching, is often proposed as a strategy with a broad anti-virulence effect. Areas covered : We discuss the role and regulatory targets of QS control in selected Gram-positive and Gram-negative bacteria, focusing on those with clinical importance and QS control of virulence. We present the components of QS systems that form possible targets for the development of anti-virulence drugs and discuss recent research on quorum-quenching approaches to control bacterial infection. Expert opinion : While there has been extensive research on QS systems and quorum-quenching approaches, there is a paucity of in-vivo research using adequate animal models to substantiate applicability. In-vivo research on QS blockers needs to be intensified and optimized to use clinically relevant setups, in order to underscore that such drugs can be used effectively to overcome problems associated with the treatment of severe infections by antibiotic-resistant pathogens.