Salmonella Enteritidis (SE) is one of the most common causes of bacterial food-borne illnesses in the world. Despite the SE’s ability to colonize and infect a wide-range of host, the most common source of infection continues to be the consumption of contaminated shell eggs and egg-based products. To date, the role of the source of SE infection has not been studied as it relates to SE pathogenesis and resulting disease. Using a streptomycin-treated mouse model of human colitis, this study examined the virulence of SE grown in egg yolk and Luria Bertani (LB) broth, and mouse feces collected from mice experimentally infected with SEE1 (SEE1 passed through mice). Primary observations revealed that the mice infected with SE grown in egg yolk displayed greater illness and disease markers than those infected with SE passed through mice or grown in LB broth. Furthermore, the SE grown in egg yolk achieved higher rates of colonization in the mouse intestines and extra-intestinal organs of infected mice than the SE from LB broth or mouse feces. Our results here indicate that the source of SE infection may contribute to the overall pathogenesis of SE in a second host. These results also suggest that reservoir-pathogen dynamics may be critical for SE’s ability to establish colonization and priming for virulence potential.

Nonfimbrial Adhesin Mutants Reveal Divergent Escherichia coli O157:H7 Adherence Mechanisms on Human and Cattle Epithelial Cells: Shiga toxin-producing, enterohemorrhagic Escherichia coli (EHEC) serotype O157:H7 is a major foodborne pathogen causing symptoms ranging from simple intestinal discomfort to bloody diarrhea and life-threatening hemolytic uremic syndrome in humans. Cattle can be asymptomatically colonized by O157:H7 predominantly at the rectoanal junction (RAJ). Colonization of the RAJ is highly associated with the shedding of O157:H7 in bovine feces. Supershedding (SS) is a phenomenon that has been reported in some cattle that shed more than 10⁴ colony-forming units of O57:H7 per gram of feces, 1001000 times more or greater than normal shedders. The unique bovine RAJ cell adherence model revealed that O157:H7 employs a LEE-independent mechanism of attachment to one of the RAJ cell types, the squamous epithelial (RSE) cells. Nine nonfimbrial adhesins were selected to determine their role in the characteristic hyperadherent phenotype of SS O157 on bovine RSE cells, in comparison with human HEp-2 cells. A number of single nucleotide polymorphisms (SNPs) were found amongst these nonfimbrial adhesins across a number of SS isolates. In human cells, deletion of yfaL reduced the adherence of both EDL933 and SS17. However, deletion of eae resulted in a significant loss of adherence in SS17 whereas deletion of wzzB and iha in EDL933 resulted in the same loss of adherence to HEp-2 cells. On RSE cells, none of these nonfimbrial deletion mutants were able to alter the adherence phenotype of SS17. In EDL933, deletion of cah resulted in mitigated adherence. Surprisingly, four nonfimbrial adhesin gene deletions were actually able to confer the hyperadherent phenotype on RSE cells. Overall, this study reveals that the contribution of nonfimbrial adhesins to the adherence mechanisms and functions of O157:H7 is both strain and host cell type dependent as well as indicates a possible role of these nonfimbrial adhesins in the SS phenotype exhibited on RSE cells.

Salmonella enterica serovar Enteritidis (S. Enteritidis) is one of the most common causes of bacterial foodborne infections worldwide. It has an extensive host range, including birds and humans, making it one of the most adaptable Salmonella serovars. This study aims to define the virulence gene profile of S. Enteritidis and identify genes critical to its host specificity. Currently, there is limited understanding of the molecular mechanisms that allow S. Enteritidis to continue as an important foodborne pathogen. To better understand the genes that may play a role in the host-specific virulence and/or fitness of S. Enteritidis, we first compiled a virulence gene profile-based genome analysis of sequenced S. Enteritidis strains isolated from shell eggs in our laboratory. This analysis was subsequently used to compare the representative genomes of Salmonella serovars with varying host ranges and S. Enteritidis genomes. The study involved a comprehensive and direct examination of the conservation of virulence and/or fitness factors, especially in a host-specific manner—an area that has not been previously explored. Key findings include the identification of 10 virulence-associated clusters of orthologous genes (COGs) specific to poultry-colonizing serovars and 12 virulence-associated COGs unique to human-colonizing serovars. Virulence/fitness-associated gene analysis identified more than 600 genes. The genome sequences of the two S. Enteritidis isolates were compared to those of the other serovars. Genome analysis revealed a core of 2817 COGs that were common to all the Salmonella serovars examined. Comparative genome analysis revealed that 10 virulence-associated COGs were specific to poultry-colonizing serovars, whereas 12 virulence-associated COGs were present in all human-colonizing serovars. Phylogenetic analyses further highlight the evolution of host specificity in S. Enteritidis. This study offers the first comprehensive analysis of genes that may be unique to and possibly essential for the colonization and/or pathogenesis of S. Enteritidis in various and specific hosts.

Neisseria gonorrhoeae is a bacterial pathogen responsible for the sexually transmitted infection, gonorrhea. Emergence of antimicrobial resistance (AMR) of N. gonorrhoeae worldwide has resulted in limited therapeutic choices for this infection. Men who seek treatment often have symptomatic urethritis; in contrast, gonococcal cervicitis in women is usually minimally symptomatic, but may progress to pelvic inflammatory disease. Previously, we reported the first analysis of gonococcal transcriptome expression determined in secretions from women with cervical infection. Here, we defined gonococcal global transcriptional responses in urethral specimens from men with symptomatic urethritis and compared these with transcriptional responses in specimens obtained from women with cervical infections, and of in vitro-grown N. gonorrhoeae isolates. This is the first comprehensive comparison of gonococcal gene expression in infected men and women. RNA sequencing analysis revealed that 9.4% of gonococcal genes showed increased expression exclusively in men and included genes involved in host immune cell interactions and 4.3% showed increased expression exclusively in women and included phage-associated genes. Infected men and women displayed comparable antibiotic resistant-genotypes and in vitro –phenotypes, but a 4-fold higher expression of the Mtr efflux pump-related genes was observed in men. These results suggest that expression of AMR genes is programmed genotypically, and also driven by sex-specific environments. Collectively, our results indicate that distinct N. gonorrhoeae gene expression signatures are detected during genital infection in men and women. We propose that therapeutic strategies could target sex specific differences in expression of antibiotic resistance genes.