Research Publications (Food Safety)

We take advantage of an historic collection of 133 Staphylococcus aureus strains accessioned between 1924 and 2016, whose genomes have been long-read sequenced as part of a major National Collection of Type Cultures (NCTC) initiative, to conduct a gene family-wide computational analysis of enterotoxin genes. We identify two novel Staphylococcal enterotoxin (pseudo)genes (sel29p and sel30), the former of which has not been observed in any contemporary strain to date.

The bacterium Listeria monocyctogenes ubiquitously occurs in the environment, but can cause severe invasive disease in susceptible individuals when ingested. We recently identified the L. monocytogenes genes lieAB and lftRS, encoding a multi drug resistance ABC transporter and a regulatory module, respectively. These genes jointly mediate resistance against aurantimycin, an antibiotic produced by the soil-dwelling species Streptomyces aurantiacus, and thus contribute to survival of L.

Integrative and conjugative elements (ICEs) are mobile genetic elements capable of transferring their own and other DNA. They contribute to the spread of antibiotic resistances and other important traits for bacterial evolution. Exclusion is a mechanism used by many conjugative plasmids and a few ICEs to prevent their host cell from acquiring a second copy of the cognate element.

Under conditions of glucose excess, aerobically growing bacteria predominantly direct carbon flux towards acetate fermentation, a phenomenon known as overflow metabolism or the bacterial ‘Crabtree effect’. Numerous studies of the major acetate-generating pathway, the Pta-AckA, revealed its important role in bacterial fitness through the control of central metabolism to sustain balanced growth and cellular homeostasis.

Coxiella burnetii strains carry one of four large, conserved, autonomously replicating plasmids (QpH1, QpRS, QpDV, and QpDG) or a QpRS-like chromosomally integrated sequence of unknown function. Here we report the characterization of the QpH1 plasmid of C. burnetii Nine Mile phase II by making QpH1-deficient strains. A shuttle vector pQGK containing the CBUA0036-0039a region (predicted as being required for the QpH1 maintenance) was constructed.

Large clostridial toxins (LCTs) are secreted virulence factors found in several species, including Clostridioides difficile, Clostridium perfringens, Paeniclostridium sordellii, and Clostridium novyi. LCTs are large toxins that lack a secretion signal sequence and studies by others have shown the LCTs of C. difficile, TcdA and TcdB, require a holin-like protein, TcdE, for secretion. The TcdE gene is located on the PaLoc pathogenicity locus of C.

Clostridium perfringens Type G strains cause necrotic enteritis (NE) in poultry, an economically important disease that is a major target of in-feed antibiotics. NE is a multifactorial disease, involving not only the critically-important NetB toxin, but also additional virulence and virulence-associated factors. We previously identified a C. perfringens chromosomal locus (VR-10B) associated with disease-causing strains that is predicted to encode a sortase-dependant pilus.

Intestinal mucus is the first line of defense against intestinal pathogens. It acts as a physical barrier between epithelial tissues and the lumen that enteropathogens must overcome to establish a successful infection. We investigated the motile behavior of two V. cholerae strains (El Tor C6706 and Classical O395) in mucus using single cell tracking in unprocessed porcine intestinal mucus. We determined that V.

The function of cvpA, a bacterial gene predicted to encode an inner membrane protein, is largely unknown. Early studies in E. coli linked cvpA to Colicin V secretion and recent work revealed that it is required for robust intestinal colonization by diverse enteric pathogens. In enterohemorrhagic E. coli (EHEC), cvpA is required for resistance to the bile salt deoxycholate (DOC).

The Yersinia genus comprises pathogens that are able to adapt to an environmental life cycle stage as well as to mammals. Yersinia enterocolitica strain W22703 exhibits both insecticidal and nematocidal activity conferred by the tripartite toxin complex (Tc) that is encoded on the 19 kb pathogenicity island Tc-PAIYe. All tc genes follow a strict temperature regulation in that they are silenced at 37°C, but activated at lower temperatures.

FliA is a broadly conserved factor that directs transcription of genes involved in flagellar motility. We previously identified FliA-transcribed genes in Escherichia coli and Salmonella enterica serovar Typhimurium, and we showed that E. coli FliA transcribes many unstable, non-coding RNAs from intragenic promoters. Here, we show that FliA in S.

Lysozyme is an important component of the innate immune system. It functions by hydrolysing the peptidoglycan (PG) layer of bacteria. The human pathogen Listeria monocytogenes is intrinsically lysozyme resistant. The peptidoglycan N-deacetylase PgdA and O-acetyltransferase OatA are two known factors contributing to its lysozyme resistance. Furthermore, it was shown that the absence of components of an ABC transporter, here referred to as EslABC, leads to reduced lysozyme resistance.

Vibrio parahaemolyticus rapidly colonizes surfaces using swarming motility. Surface contact induces the surface sensing regulon including lateral flagellar genes, spurring dramatic shifts in physiology and behavior. The bacterium can also adopt a sessile, surface-associated lifestyle and form robust biofilms. These alternate colonization strategies are influenced reciprocally by the second messenger c-di-GMP. Although V.

To initiate their life cycle, phages must specifically bind to the surface of their bacterial hosts. Long-tailed phages often interact with the cell surface using fibers, which are elongated intertwined trimeric structures. The folding and assembly of these complex structures generally requires the activity of an intra- or intermolecular chaperone protein.

An essential feature of the pathogenesis of Salmonella enterica serovar Enteritidis (S. Enteritidis; wild type (WT)) is its ability to survive in diverse micro-environmental stress conditions such as encountering antimicrobial peptides (AMPs), glucose and micronutrient starvation. These stress factors trigger virulence genes encoded on Salmonella pathogenicity islands (SPIs) and determine the efficiency of enteric infection.

Cyclic-di-AMP (c-di-AMP) is an essential and ubiquitous second messenger among bacteria. C-di-AMP regulates many cellular pathways through direct binding to several molecular targets in bacterial cells. C-di-AMP depletion is well known to destabilize the bacterial cell wall, resulting in increased bacteriolysis and enhanced susceptibility to cell wall targeting antibiotics.

Shigella flexneri is a major causative agent of bacillary dysentery in developing countries where serotype 2a2 is the prevalent strain. To date, approximately 30 serotypes have been identified for S. flexneri and the major contribution to the emergence of new serotypes is chemical modifications of the lipopolysaccharide (LPS) component O antigen (Oag). Glucosylation, O-acetylation and phosphoethanolamine (PEtN) modifications increase the Oag diversity providing benefits to S. flexneri.

Members of the small multidrug resistant (SMR) efflux pump family known as SugE (more recently renamed to Gdx) are known for their narrow substrate selectivity to small guanidinium (Gdm+) compounds and disinfectant quaternary ammonium compounds (QACs). Gdx members have been identified on multidrug resistant plasmids in Gram-negative bacilli, but their functional role remains unclear as few have been characterized.

Pathogenic Vibrios use many different approaches to subvert, attack, and undermine the host response. The toxins they produce are often responsible for the devastating effects associated with their diseases. These toxins target a variety of host proteins, which leads to deleterious effects including dissolution of cell organelle integrity and inhibition of protein secretion. Becoming increasingly prevalent as co-factors for Vibrio toxins are proteins of the small GTPase families.

YggS (COG0325) is a pyridoxal 5'-phosphate (PLP)-binding protein proposed to be involved in homeostasis of B6 vitamers. In Salmonella enterica, lack of yggS resulted in phenotypes that were distinct, and others that were similar, to those of a yggS mutant of Escherichia coli. Like other organisms, yggS mutants of S. enterica accumulate endogenous pyridoxine 5'-phosphate (PNP). Data herein show that strains lacking YggS accumulated ~10-fold more PLP in growth medium than a parental strain.

Phenotypic testing for drug susceptibility of Mycobacterium tuberculosis is critical to basic research and managing the evolving problem of antimicrobial resistance in tuberculosis management, but remains a specialized technique to which access is severely limited. Here, we report on the development and validation of an improved phage-mediated detection system for M. tuberculosis.

Motility is required for many bacterial pathogens to reach and colonize target sites. Vibrio cholerae traverses a thick mucus barrier coating the small intestine to reach the underlying epithelium. We screened a transposon library in motility media containing mucin to identify factors that influence mucus transit. Lesions in structural genes of the Type VI Secretion System (T6SS) were among those recovered.

The Gram-negative enterobacterium Erwinia amylovora causes fire blight disease in apple and pear trees. Lipopolysaccharides and the exopolysaccharide amylovoran are essential E. amylovora virulence factors. We found that mutations to rfbX disrupted amylovoran production and virulence in apple fruits and tree shoots, and that deletion of yibD suppressed the rfbX mutant phenotype. Expression of yibD was about ten-fold higher in rfbX compared to wild-type.

Fluctuations in osmolarity are one of the most prevalent stresses to which bacteria must adapt, both hypo- and hyper-osmotic conditions. Most bacteria cope with high osmolarity by accumulating compatible solutes (osmolytes) in the cytoplasm to maintain the turgor pressure of the cell.

To adapt to changing and potentially hostile environments, bacteria can activate the transcription of genes under the control of alternative sigma factors, such as SigB, a master regulator of the general stress response in several Gram-positive species. Bacillus thuringiensis is a Gram-positive spore-forming invertebrate pathogen whose lifecycle includes a variety of environments, including plants, insect hemocoel or gut. Here we assessed the role of SigB during the infectious cycle of B.