Search

For decades now, DNA fingerprinting by means of pulsed-field gel electrophoresis (PFGE) continues to be the most widely used to separate large DNA molecules and distinguish between different strains in alternating pulses. This is done by isolating intact chromosomal DNA and using restriction enzymes with specific restriction sites to generate less than 30 restriction fragments from 50 Kb to 10 Mbp. These results make clone-specific band profiles easy to compare. Specialized equipment is required for the optimization of DNA separation and resolution, among which a contour-clamped homogeneous electric field (CHEF) apparatus is the most commonly used. As a result, the PFGE analysis of a bacterial genome provides useful information in terms of epidemiological investigations of different bacterial pathogens. For Staphylococcus aureus subtyping, despite its limitations and the emergence of alternative methods, PFGE analysis has proven to be an adequate choice and the gold standard for determining genetic relatedness, especially in outbreak detection and short-term surveillance in the veterinary field. [ABSTRACT FROM AUTHOR]

Antimicrobial resistance is a global health threat and efforts to mitigate it is warranted, thus the need for local antibiograms to improve stewardship. This study highlights the process that was used to develop an antibiogram to monitor resistance at a secondary-level health facility to aid empirical clinical decision making in a sub-Saharan African county. This retrospective cross-sectional descriptive study used 3 years of cumulative data from January 2016 to December 2018. Phenotypic data was manually imputed into WHONET and the cumulative antibiogram constructed using standardized methodologies according to CLSI M39-A4 guidelines. Pathogens were identified by standard manual microbiological methods and antimicrobial susceptibility testing was performed using Kirby-Bauer disc diffusion method according to CLSI M100 guidelines. A total of 14,776 non-duplicate samples were processed of which 1163 (7.9%) were positive for clinically significant pathogens. Among the 1163 pathogens, E. coli (n = 315) S. aureus (n = 232), and K. pneumoniae (n = 96) were the leading cause of disease. Overall, the susceptibility for E. coli and K. pneumoniae from all samples were: trimethoprim-sulfamethoxazole (17% and 28%), tetracycline (26% and 33%), gentamicin (72% and 46%), chloramphenicol (76 and 60%), and ciprofloxacin (69% and 59%), and amoxicillin/clavulanic (77% and 54%) respectively. Extended spectrum beta-lactamase (ESBL) resistance was present in 23% (71/315) vs. 35% (34/96) respectively. S. aureus susceptibility for methicillin was 99%. This antibiogram has shown that improvement in combination therapy is warranted in The Gambia. [ABSTRACT FROM AUTHOR]

Newborns are highly susceptible to infections; however, the underlying mechanisms that regulate the anti-microbial T-helper cells shortly after birth remain incompletely understood. To address neonatal antigen-specific human T-cell responses against bacteria, Staphylococcus aureus (S. aureus) was used as a model pathogen and comparatively analyzed in terms of the polyclonal staphylococcal enterotoxin B (SEB) superantigen responses. Here, we report that neonatal CD4 T-cells perform activation-induced events upon S. aureus/APC-encounter including the expression of CD40L and PD-1, as well as the production of Th1 cytokines, concomitant to T-cell proliferation. The application of a multiple regression analysis revealed that the proliferation of neonatal T-helper cells was determined by sex, IL-2 receptor expression and the impact of the PD-1/PD-L1 blockade. Indeed, the treatment of S. aureus-activated neonatal T-helper cells with PD-1 and PD-L1 blocking antibodies revealed the specific regulation of the immediate neonatal T-cell responses with respect to the proliferation and frequencies of IFNγ producers, which resembled in part the response of adults' memory T-cells. Intriguingly, the generation of multifunctional T-helper cells was regulated by the PD-1/PD-L1 axis exclusively in the neonatal CD4 T-cell lineage. Together, albeit missing memory T-cells in neonates, their unexperienced CD4 T-cells are well adapted to mount immediate and strong anti-bacterial responses that are tightly controlled by the PD-1/PD-L1 axis, thereby resembling the regulation of recalled memory T-cells of adults. [ABSTRACT FROM AUTHOR]

Vat photopolymerization (VPP) is an additive manufacturing process commonly used in medical applications. This work aims, for the first time in the literature, to extend and enhance the performance of a commercial medical-grade resin for the VPP process, with the development of nanocomposites, using Copper (Cu) nanoparticles as the additive at two different concentrations. The addition of the Cu nanoparticles was expected to enhance the mechanical properties of the resin and to enable biocidal properties on the nanocomposites since Cu is known for its antibacterial performance. The effect of the Cu concentration was investigated. The nanocomposites were prepared with high-shear stirring. Specimens were 3D printed following international standards for mechanical testing. Their thermal and spectroscopic response was also investigated. The morphological characteristics were examined. The antibacterial performance was evaluated with an agar well diffusion screening process. The experimental results were analyzed with statistical modeling tools with two control parameters (three levels each) and eleven response parameters. Cu enhanced the mechanical properties in all cases studied. 0.5 wt.% Cu nanocomposite showed the highest improvement (approximately 11% in tensile and 10% in flexural strength). The antibacterial performance was sufficient against S. aureus and marginal against E. coli. [ABSTRACT FROM AUTHOR]

Antimicrobial resistance is one of the major clinical concerns, making the discovery of new antimicrobial drugs desirable. Moringin (MOR), the major isothiocyanate produced from Moringa oleifera seeds, could represent an alternative therapeutic strategy to commonly used antibiotics. The aim of our study was to investigate the antimicrobial effect of MOR conjugated with α-cyclodextrin (MOR/α-CD), a complex with an improved solubility and stability in aqueous solutions. Our data demonstrated that MOR/α-CD was able to exert antimicrobial activity against the S. aureus reference strains (ATCC 25923, ATCC 6538, and ATCC BAA-977). Moreover, MOR/α-CD showed bacteriostatic effects (MIC = minimum inhibitory concentration = 0.5 mg/mL) and bactericidal properties (MBC = minimum bactericidal concentration = 1 mg/mL) against the overall assessed strains. In addition, MOR/α-CD showed bactericidal activity against the S. aureus strain ATCC BAA-977 after treatment with erythromycin (Ery), which induced clindamycin-resistance on the erm (A) gene. This evidence led us to assume that MOR/α-CD could be a promising antimicrobial agent against strains with the clindamycin-resistant phenotype (CC-resistant). [ABSTRACT FROM AUTHOR]

Globally, prematurity is the leading cause of neonatal mortality (babies in the first four weeks of life) and now the second leading cause of mortality after pneumonia in children under age five. The neonatal gut microbial colonization is crucial in the human life cycle. Placental microbiota transmits from the gut microbiota plays a significant role in association with kinship. Simultaneously, this transition is being made from mother to infant. This comparative study explored the diversity of microbiota associated with term and preterm neonates by evaluating the placental samples. The study found that 16/68 (23.5%) full-term placental samples were positive for S. aureus; on the other hand, 4/16 (25%) preterm placental samples confirmed culture growth for S. aureus. Antimicrobial susceptibility patterns showed that Staphylococcusaureus (S. aureus) isolates from both types of samples were resistant to Ofloxacin, Trimethoprim-sulfamethoxazole, Oxacillin, and Cefoxitin. However, Methicillin-Resistant Staphylococcus aureus (MRSA) detection was 43.75% in full-term and 75% in preterm placental samples. Moreover, two isolates were positive for both mecA and PVL virulent genes, and the rest were positive only for the mecA gene. Interestingly few isolates lacked both characteristic MRSA genes, mecA and PVL. Notably, resistances were more inclined towards preterm samples for antimicrobial susceptibility and MRSA screening. It may be concluded that there is a significant presence of S. aureus in the placenta of mothers with term and preterm deliveries which might be responsible for preterm deliveries. Therefore, judicious use of antibiotics during pregnancies may help prevent preterm births. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus is a vital bovine mastitis pathogen causing huge economic losses to the dairy industry worldwide. In our previous studies, leukotoxin ED (LukED) was detected in most S. aureus strains isolated from bovine mastitis. Here, four single-chain fragment variables (scFvs) (ZL8 and ZL42 targeting LukE, ZL22 and ZL23 targeting LukD) were obtained using purified LukE and LukD proteins as the antigens after five rounds of bio-panning. The complementarity-determining region 3 (CDR3) of the VH domain of these scFvs exhibited significant diversities. In vitro, the scFvs significantly decreased LukED-induced cell killing by inhibiting the binding of LukED to chemokine receptors (CCR5 and CXCR2) and reduced the death rates of bovine neutrophils and MAC-T cells caused by LukED and S. aureus (p < 0.05). In an S. aureus-induced mouse mastitis model, histopathology and MPO results revealed that scFvs ameliorated the histopathological damages and reduced the infiltration of inflammatory cells (p < 0.05). The ELISA and qPCR assays showed that scFvs reduced the transcription and expression levels of Tumor Necrosis Factor-alpha (TNF-α), interleukin-1β (IL-1β), IL-6, IL-8 and IL-18 (p < 0.05). The overall results demonstrated the protective anti-inflammatory effect of scFvs in vitro and in vivo, enlightening the potential role of scFvs in the prevention and treatment of S. aureus-induced mastitis. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus is a causative agent of bovine mastitis, capable of causing significant economic losses to the dairy industry worldwide. This study focuses on obtaining single-chain fragment variables (scFvs) against the virulence factors of S. aureus and evaluates the protective effect of scFvs on bovine mammary epithelial (MAC-T) cells and mice mammary gland tissues infected by S. aureus. After five rounds of bio-panning, four scFvs targeting four virulence factors of S. aureus were obtained. The complementarity-determining regions (CDRs) of these scFvs exhibited significant diversities, especially CDR3 of the VH domain. In vitro, each of scFvs was capable of inhibiting S. aureus growth and reducing the damage of MAC-T cells infected by S. aureus. Preincubation of MAC-T cells with scFvs could significantly attenuate the effect of apoptosis and necrosis compared with the negative control group. In vivo, the qPCR and ELISA results demonstrated that scFvs reduced the transcription and expression of Tumor Necrosis Factor alpha (TNF-α), interleukin-1β (IL-1β), IL-6, IL-8, and IL-18. Histopathology and myeloperoxidase (MPO) results showed that scFvs ameliorated the histopathological damages and reduced the inflammatory cells infiltration. The overall results demonstrated the positive anti-inflammatory effect of scFvs, revealing the potential role of scFvs in the prevention and treatment of S. aureus infections. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus is a vital bovine mastitis pathogen causing huge economic losses to the dairy industry worldwide. In our previous studies, leukotoxin ED (LukED) was detected in most S. aureus strains isolated from bovine mastitis. Here, four single-chain fragment variables (scFvs) (ZL8 and ZL42 targeting LukE, ZL22 and ZL23 targeting LukD) were obtained using purified LukE and LukD proteins as the antigens after five rounds of bio-panning. The complementarity-determining region 3 (CDR3) of the VH domain of these scFvs exhibited significant diversities. In vitro , the scFvs significantly decreased LukED-induced cell killing by inhibiting the binding of LukED to chemokine receptors (CCR5 and CXCR2) and reduced the death rates of bovine neutrophils and MAC-T cells caused by LukED and S. aureus ( p < 0.05). In an S. aureus -induced mouse mastitis model, histopathology and MPO results revealed that scFvs ameliorated the histopathological damages and reduced the infiltration of inflammatory cells ( p < 0.05). The ELISA and qPCR assays showed that scFvs reduced the transcription and expression levels of Tumor Necrosis Factor-alpha (TNF-α), interleukin-1β (IL-1β), IL-6, IL-8 and IL-18 ( p < 0.05). The overall results demonstrated the protective anti-inflammatory effect of scFvs in vitro and in vivo, enlightening the potential role of scFvs in the prevention and treatment of S. aureus -induced mastitis.

Nonthermal, biocompatible plasma (NBP) is a promising unique state of matter that is effective against a wide range of pathogenic microorganisms. This study focused on a sterilization method for bacteria that used the dielectric barrier discharge (DBD) biocompatible plasma cabinet sterilizer as an ozone generator. Reactive oxygen species play a key role in inactivation when air or other oxygen-containing gases are used. Compared with the untreated control, Escherichia coli(E. coli), Staphylococcus aureus (S. aureus), and Salmonella typhimurium (sepsis) were inhibited by approximately 99%, or were nondetectable following plasma treatment. Two kinds of plasma sterilizers containing six- or three-chamber cabinets were evaluated. There was no noticeable difference between the two configurations in the inactivation of microorganisms. Both cabinet configurations were shown to be able to reduce microbes dramatically, i.e., to the nondetectable range. Therefore, our data indicate that the biocompatible plasma cabinet sterilizer may prove to be an appropriate alternative sterilization procedure. [ABSTRACT FROM AUTHOR]

Toll-like receptor (TLR) signaling is an indispensable factor in immune cells activation. Many TLR ligands have been identified, and were characterized the immunological functions such as inflammatory cytokine production in immune cells. However, the anti-inflammatory response in TLR ligand-mediated manner is poorly understood. In this report, we show that bacterial lipoteichoic acid (LTA), which is a TLR2 ligand from gram-positive bacteria including Staphylococcus aureus (S. aureus), suppresses TLR-mediated inflammatory response in dendritic cells (DCs). The TLR ligand-induced Tumor Necrosis Factor-alpha (TNF-α) production was suppressed in the bone marrow derived dendritic cells (BMDCs) by co-treatment of LTA. The cellular activation, which was characterized as upregulations of CD80, CD86 and major histocompatibility complex II (MHC II) expression, was also suppressed in the TLR ligand stimulated BMDCs in the presence of LTA. While LTA itself didn't induced both TNF-α production and upregulation of cell surface markers. The LTA mediated immunosuppressive function was abolished by TLR2 blocking in lipopolysaccharide (LPS)-stimulated BMDCs. Furthermore, LTA also showed the immunosuppressive function in the generation of IFN-γ+CD4+ T (Th1) cells by attenuation of antigen presenting activity in the BMDCs. In the imiquimod (IMQ)-induced acute skin inflammation, LTA suppressed the inflammation by downregulation of the activation in skin accumulated DCs. Thus, LTA is a TLR2 dependent immunological suppressor against inflammatory response induced by other TLR ligands in the DCs. [ABSTRACT FROM AUTHOR]