Food-associated Salmonella challenges: Pathogenicity and antimicrobial resistance

National Farm Medicine Center, Marshfield Clinic Research Foundation, Marshfield, WI 54449, USA.
Journal of Animal Science (Impact Factor: 2.11). 05/2008; 86(14 Suppl):E173-87. DOI: 10.2527/jas.2007-0447
Source: PubMed


Salmonellosis is a worldwide health problem; Salmonella infections are the second leading cause of bacterial foodborne illness in the United States. Approximately 95% of cases of human salmonellosis are associated with the consumption of contaminated products such as meat, poultry, eggs, milk, seafood, and fresh produce. Salmonella can cause a number of different disease syndromes including gastroenteritis, bacteremia, and typhoid fever, with the most common being gastroenteritis, which is often characterized by abdominal pain, nausea, vomiting, diarrhea, and headache. Typically the disease is self-limiting; however, with more severe manifestations such as bacteremia, antimicrobial therapy is often administered to treat the infection. Currently, there are over 2,500 identified serotypes of Salmonella. A smaller number of these serotypes are significantly associated with animal and human disease including Typhimurium, Enteritidis, Newport, Heidelberg, and Montevideo. Increasingly, isolates from these serotypes are being detected that demonstrate resistance to multiple antimicrobial agents, including third-generation cephalosporins, which are recommended for the treatment of severe infections. Many of the genes that encode resistance are located on transmissible elements such as plasmids that allow for potential transfer of resistance among strains. Plasmids are also known to harbor virulence factors that contribute to Salmonella pathogenicity. Several serotypes of medical importance, including Typhimurium, Enteritidis, Newport, Dublin, and Choleraesuis, are known to harbor virulence plasmids containing genes that code for fimbriae, serum resistance, and other factors. Additionally, many Salmonella contain pathogenicity islands scattered throughout their genomes that encode factors essential for bacterial adhesion, invasion, and infection. Salmonella have evolved several virulence and antimicrobial resistance mechanisms that allow for continued challenges to our public health infrastructure.

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    • "In pigs, S. Typhimurium causes enterocolitis and frequently exits in a subclinical carrier state, in which infected animal will intermittently or continuously shed bacteria organisms in their feces for very prolonged periods of time, making elimination of the infection difficult (Gopinath et al., 2012). In humans, S. Typhimurium is the second serovar most frequently reported in the EU and infection by this pathogen is mostly associated with the consumption of contaminated pork (Foley and Lynne, 2008). Although the gastrointestinal tract is considered to be their biological niche, Salmonella preferentially colonize ileum, caecun and colon (Darwin and Miller, 1999; Boyen et al., 2008). "
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    ABSTRACT: The enteropathogen Salmonella Typhimurium (S. Typhimurium) is the most commonly non-typhoideal serotype isolated in pig worldwide. Currently, one of the main sources of human infection is by consumption of pork meat. Therefore, prevention and control of salmonellosis in pigs is crucial for minimizing risks to public health. The aim of the present study was to use isobaric tags for relative and absolute quantification (iTRAQ) to explore differences in the response to Salmonella in two segment of the porcine gut (ileum and colon) along a time course of 1, 2, and 6 days post infection (dpi) with S. Typhimurium. A total of 298 proteins were identified in the infected ileum samples of which, 112 displayed significant expression differences due to Salmonella infection. In colon, 184 proteins were detected in the infected samples of which 46 resulted differentially expressed with respect to the controls. The higher number of changes in protein expression was quantified in ileum at 2 dpi. Further biological interpretation of proteomics data using bioinformatics tools demonstrated that the expression changes in colon were found in proteins involved in cell death and survival, tissue morphology or molecular transport at the early stages and tissue regeneration at 6 dpi. In ileum, however, changes in protein expression were mainly related to immunological and infection diseases, inflammatory response or connective tissue disorders at 1 and 2 dpi. iTRAQ has proved to be a proteomic robust approach allowing us to identify ileum as the earliest response focus upon S. Typhimurium in the porcine gut. In addition, new functions involved in the response to bacteria such as eIF2 signaling, free radical scavengers or antimicrobial peptides (AMP) expression have been identified. Finally, the impairment at of the enterohepatic circulation of bile acids and lipid metabolism by means the under regulation of FABP6 protein and FXR/RXR and LXR/RXR signaling pathway in ileum has been established for the first time in pigs. Taken together, our results provide a better understanding of the porcine response to Salmonella infection and the molecular mechanisms underlying Salmonella-host interactions.
    Frontiers in Cellular and Infection Microbiology 09/2015; 5:64. DOI:10.3389/fcimb.2015.00064 · 3.72 Impact Factor
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    • "Many studies have focused on the epidemiology, resistance and virulence of non-typhoid serovars that are commonly involved in human and animal infections (Foley and Lynne, 2008). In contrast, rarely detected serovars such as S. Eppendorf have received little attention (Bisi-Johnson et al., 2011; Shilangale et al., 2012; Karou et al., 2013). "
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    ABSTRACT: Salmonella enterica subsp. enterica serovar Eppendorf, with antigenic formula 1,4,12,[27]:d:1,5, is an infrequent serovar. However, 14% (20 out of 142) of the isolates recovered during June-July, 2012 in chicken farms in Tunisia belonged to S. Eppendorf. These isolates were analyzed for resistance and virulence profiles. None of them were susceptible to all antimicrobials tested, while 70%, 60%, 50%, 50%, 20% and 5% were resistant to sulfonamides (sul1, sul2 and sul3), streptomycin (aadA1-like), trimethoprim (dfrA1-like), nalidixic acid (GyrA Asp87→Asn and not identified), gentamicin (not identified) and ampicillin (blaTEM). 30% of the isolates showed decreased susceptibility to ciprofloxacin, and carried the qnrB gene. 65% of the isolates were multidrug resistant, and contained class 1 integrons with sul1 or sul3 in the 3’ conserved segment. The orgA, ssaQ, mgtC, siiD and sopB virulence genes located on SPI1 to SPI5 and the fimbrial bcfC gene were present in all isolates; the sopE1 and sodC1 carried by prophages were variably detected; while the prophage gipA gene and the spvC gene of serovar-specific virulence plasmids were absent. Altogether, ten resistance and three virulence profiles were identified. Typing of the isolates with XbaI- and BlnI-PFGE supports a close relationship, although they appear to be evolving under selective pressure probably caused by antimicrobial use in chicken husbandry. As far as we know, this is the first study investigating the molecular bases of antimicrobial drug resistance, the virulence gene content, and the PFGE profiles of S. Eppendorf. The epidemiological surveillance of this serovar would be necessary to evaluate its possible impact in human health, particularly in Tunisia and other African countries where it was already reported. Keywords: Salmonella enterica serovar Eppendorf, antimicrobial drug resistance, qnrB, class 1 integrons, virulence genes, PFGE
    Zoonoses and Public Health 09/2015; DOI:10.1111/zph.12234 · 2.37 Impact Factor
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    • "The spread of antimicrobial resistance through the food chain is regarded as a major public health issue (Threlfall 2002; Lynch et al., 2006; Foley and Lynne 2008; Le Hello et al., 2011). The emergence of both plasmid mediated antibiotic resistant against conventional antimicrobials and chromosomal resistance to quinolones and fluoroquinolones has reduced therapeutic options for Salmonella septicemia in humans (Foley and Lynne 2008). Furthermore, infections with such drug-resistant Salmonella species are associated with increased morbidity and mortality . "
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    ABSTRACT: Evaluation of human and animal health surveillance programs is currently lacking in most developing countries including sub-Saharan Africa. To evaluate the burden of salmonellosis and antimicrobial resistance status in developing countries, we need to identify the sources, serovar distribution and the prevalence of Salmonella to guide in the formulation of control program. This study was undertaken to determine the prevailing Salmonella serovars, the occurrence and the antimicrobial susceptibility patterns of Salmonella enterica subspecies enterica recovered from fish. Stratified random sampling was carried out in 2009 on 200 fish samples. All the isolates were biochemically characterized and presumptive Salmonella isolates were serotyped using standard procedure and tested for antimicrobial susceptibility by minimum inhibitory concentration (MIC). A total of 23 isolates were positive for Salmonella out of the 200 samples (11.5%) analyzed, three different serovars comprising Salmonella serovars Hadar, 47: mt:-, and Eko were obtained. Generally, the antimicrobial resistance profile was low; however Salmonella Hadar showed a high level of resistance to the antimicrobial agents. Salmonella serovars; Hadar, 47: mt:- and Eko are the pathogens associated with fish contamination in Maiduguri, North eastern Nigeria and constitute serious health risks for the human population and need to be controlled by targeted interventions.
    Egyptian Journal of Aquatic Research 12/2014; 40(1). DOI:10.1016/j.ejar.2014.01.003
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