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ABSTRACT Eggs, an important part of a healthy daily diet, can protect chicken embryo development due to the shell barrier and various antibacterial components within the egg white. Our previous study demonstrated that Salmonella Pullorum, highly adapted to chickens, can survive in the egg white and, therefore, be passed to newly hatched chicks. However, the survival strategy of Salmonella Pullorum in antibacterial conditions remains unknown. The overall transcripts in the egg white showed a large-scale shift compared to LB broth. The expression of common response genes and pathways, such as those involved in iron uptake, biotin biosynthesis, and virulence, was significantly changed, consistent with the other transovarial transmission serovar Enteritidis. Notably, membrane stress response, amino acid metabolism, and carbohydrate metabolism were specifically affected. Additional upregulated functionally relevant genes (JI728_13095, JI728_13100, JI728_17960, JI728_10085, JI728_15605, and nhaA) as mutants confirmed the susceptible phenotype. Furthermore, fim deletion resulted in an increased survival capacity in the egg white, consistent with the downregulated expression. The second-round RNA-Seq analysis of the Δfim mutant in the egg white revealed significantly upregulated genes compared with the wild type in the egg white responsible for energy metabolism located on the hyc and hyp operons regulated by FhlA, indicating the Δfim mutant cannot receive enough oxygen and switched to fermentative growth due to its inability to attach to the albumen surface. Together, this study provides a first estimate of the global transcriptional response of Salmonella Pullorum under antibacterial egg white and highlights the new potential role of fim deletion in optimizing energy metabolism pathways that may assist vertical transmission.IMPORTANCEPullorum disease, causing serious embryo death and chick mortality, results in substantial economic losses worldwide due to transovarial transmission. Egg-borne outbreaks are frequently reported in many countries. The present study has filled the knowledge gap regarding how the specific chicken-adapted pathogen Salmonella Pullorum behaves within the challenging environment of egg white. The deletion of the fim fimbrial system can increase survival in the albumen, possibly by reprogramming metabolism-related gene products, which reveals a new adaptive strategy of pathogens. Moreover, the comparison, including previous research on Salmonella Enteritidis, capable of vertical transmission, aims to provide diversified data sets in the field and further help to implement reasonable and effective measures to improve both food safety and animal health.

Abstract Infectious disease outbreaks transcend the medical and public health realms, triggering widespread panic and impeding socio-economic development. Considering that self-limiting diarrhoea of sporadic cases is usually underreported, the Salmonella outbreak (SO) study offers a unique opportunity for source tracing, spatiotemporal correlation, and outbreak prediction. To summarize the pattern of SO and estimate observational epidemiological indicators, 1,134 qualitative reports screened from 1949 to 2023 were included in the systematic review dataset, which contained a 506-study meta-analysis dataset. In addition to the dataset comprising over 50 columns with a total of 46,494 entries eligible for inclusion in systematic reviews or input into prediction models, we also provide initial literature collection datasets and datasets containing socio-economic and climate information for relevant regions. This study has a broad impact on advancing knowledge regarding epidemic trends and prevention priorities in diverse salmonellosis outbreaks and guiding rational policy-making or predictive modeling to mitigate the infringement upon the right to life imposed by significant epidemics.

Abstract Salmonella enterica has a wide diversity, with numerous serovars belonging to six different subspecies with dynamic animal-host tropism. The FimH protein is the adhesin mediating binding to various cells, and slight amino acid discrepancy significantly affects the adherence capacities. To date, the general function of FimH variability across different subspecies of Salmonella enterica has not been addressed. To investigate the biological functions of FimH among the six Salmonella enterica subspecies, the present study performed several assays to determine biofilm formation, Caenorhabditis elegans killing, and intestinal porcine enterocyte cell IPEC-J2 adhesion by using various FimH allele mutants. In general, allelic mutations in both the lectin and pilin domains of FimH could cause changes in binding affinity, such as the N79S mutation. We also observed that the N79S variation in Salmonella Dublin increased the adhesive ability of IPEC-J2 cells. Moreover, a new amino acid substitution, T260M, within the pilin domain in one subspecies IIIb strain beneficial to binding to cells was highlighted in this study, even though the biofilm-forming and Caenorhabditis elegans-killing abilities exhibited no significant differences in variants. Combined with point mutations being a natural tendency due to positive selection in harsh environments, we speculate that allelic variation T260M probably contributes to pathoadaptive evolution in Salmonella enterica subspecies IIIb.

Measurement(s) S. Gallinarum positive samples Technology Type(s) Serological test • Molecular method (PCR) • Plate culture and identification • Biochemical test Factor Type(s) biovar • time • geographic sampling site • reservoir of bacteria • chicken breed • raising mode • economic use • growth stage • gender Sample Characteristic - Organism Animal Sample Characteristic - Location world

Listeria species are exposed to various stressors throughout the food chain, which are crucial for microbe mitigation strategy in the food industry. However, the survival capabilities and development of antimicrobial resistance by Listeria spp. under different food processing environments (FPEs) stressors are not yet well understood. Hence, this study aims to determine the difference in survivability and antimicrobial susceptibility of L. monocytogenes (Lm) and other Listeria species (non-Lm) strains exposed to different FPEs stressors, including heat, acidic and alkaline pH, UV irradiation, and osmotic stress. For this, a collection of 11 Lm and 10 non-Lm strains were used to conduct experiments. This study showed that Lm strains were relatively more tolerant to environmental stresses than non-Lm strains (p > 0.05). Additionally, the evaluation of stress-induced resistance toward antimicrobials showed that anaerobic incubation, after exposition to environmental stresses, rendered Lm and non-Lm more resistant to antimicrobial agents than aerobic incubation. Furthermore, the study observed that different stressors induced an increase in minimum inhibitory concentrations (MICs) of certain antimicrobials. Specifically, heat stress persuaded an increase in MICs of tetracycline under aerobic incubation, and gentamicin and ciprofloxacin under anaerobic incubation. Acidic/alkaline pH induced an increase in MICs of gentamicin, ciprofloxacin, and trimethoprim-sulfamethoxazole, especially under anaerobic incubation. However, UV stress induced increase in MICs of tetracycline and trimethoprim-sulfamethoxazole under aerobic incubation and gentamicin, ciprofloxacin, and trimethoprim-sulfamethoxazole under anaerobic incubation. Additionally, osmotic stress induced an increase in MICs of tetracycline and ampicillin under aerobic incubation and gentamicin, tetracycline, and trimethoprim-sulfamethoxazole under anaerobic incubation. Collectively, this study highlights that stress tolerance may contribute to the predominance of Listeria species among FPEs and induce the development of antimicrobial resistance even without antibiotic selection pressure. The findings of this study may guide updated strategies to mitigate Listeria species in the food industry.

Pullorum disease, caused by the Salmonella enterica serovar Gallinarum biovar Pullorum, is a highly contagious disease in the poultry industry, leading to significant economic losses in many developing countries. Due to the emergence of multidrug-resistant (MDR) strains, immediate attention is required to prevent their endemics and global spreading. To mitigate the prevalence of MDR Salmonella Pullorum infections in poultry farms, it is urgent to develop effective vaccines. Reverse vaccinology (RV) is a promising approach using expressed genomic sequences to find new vaccine targets. The present study used the RV approach to identify new antigen candidates against Pullorum disease. Initial epidemiological investigation and virulent assays were conducted to select strain R51 for presentative and general importance. An additional complete genome sequence (4.7 Mb) for R51 was resolved using the Pacbio RS II platform. The proteome of Salmonella Pullorum was analyzed to predict outer membrane and extracellular proteins, and was further selected for evaluating transmembrane domains, protein prevalence, antigenicity, and solubility. Twenty-two high-scored proteins were identified among 4713 proteins, with 18 recombinant proteins successfully expressed and purified. The chick embryo model was used to assess protection efficacy, in which vaccine candidates were injected into 18-day-old chick embryos for in vivo immunogenicity and protective effects. The results showed that the PstS, SinH, LpfB, and SthB vaccine candidates were able to elicit a significant immune response. Particularly, PstS confers a significant protective effect, with a 75% survival rate compared to 31.25% for the PBS control group, confirming that identified antigens can be promising targets against Salmonella Pullorum infection. Thus, we offer RV to discover novel effective antigens in an important veterinary infectious agent with high priority.

Salmonella enterica, serovar Gallinarum, biovar Pullorum, is an avian-specific pathogen which has caused considerable economic losses to the poultry industry worldwide. Two-component systems (TCSs) play an essential role in obtaining nutrients, detecting the presence of neighboring bacteria and regulating the expression of virulence factors. The genome analysis of S. Pullorum strain S06004 suggesting the carriage of 22 pairs of TCSs, which belong to five families named CitB, OmpR, NarL, Chemotaxis and LuxR. In the CitB family, three pairs of TCSs, namely CitA-CitB, DcuS-DcuR and DpiB-DpiA, remain unaddressed in S. Pullorum. To systematically investigate the function of the CitB family in S. Pullorum, four mutants, ΔcitAB (abbreviated as Δcit), ΔdcuSR (Δdcu), ΔdpiBA (Δdpi) and ΔcitABΔdcuSRΔdpiBA (Δ3), were made using the CRISPR/Cas9 system. The results demonstrated that the CitB family did not affect the growth of bacteria, the results of biochemical tests, invasion and proliferation in chicken macrophage HD-11 cells and the expression of fimbrial protein. But the mutants showed thicker biofilm formation, higher resistance to antimicrobial agents, enhanced tolerance to inhibition by egg albumen and increased virulence in chicken embryos. Moreover, the deletion of Dpi TCS was detrimental to survival after exposure to hyperosmotic and oxidative environments, as well as the long-term colonization of the small intestine of chickens. Collectively, we provided new knowledge regarding the possible role of the CitB family involved in the pathogenic processes of S. Pullorum.