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Distinguishable epidemics of multidrug-resistant Salmonella Typhimurium DT104 in different hosts.

ABSTRACT: The global epidemic of multidrug-resistant Salmonella Typhimurium DT104 provides an important example, both in terms of the agent and its resistance, of a widely disseminated zoonotic pathogen. Here, with an unprecedented national collection of isolates collected contemporaneously from humans and animals and including a sample of internationally derived isolates, we have used whole-genome sequencing to dissect the phylogenetic associations of the bacterium and its antimicrobial resistance genes through the course of an epidemic. Contrary to current tenets supporting a single homogeneous epidemic, we demonstrate that the bacterium and its resistance genes were largely maintained within animal and human populations separately and that there was limited transmission, in either direction. We also show considerable variation in the resistance profiles, in contrast to the largely stable bacterial core genome, which emphasizes the critical importance of integrated genotypic data sets in understanding the ecology of bacterial zoonoses and antimicrobial resistance.

SUBMITTER: Mather AE

PROVIDER: S-EPMC4012302 | biostudies-literature | 2013 Sep

REPOSITORIES: biostudies-literature

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Distinguishable epidemics of multidrug-resistant Salmonella Typhimurium DT104 in different hosts.

Mather A E AE Reid S W J SW Maskell D J DJ Parkhill J J Fookes M C MC Harris S R SR Brown D J DJ Coia J E JE Mulvey M R MR Gilmour M W MW Petrovska L L de Pinna E E Kuroda M M Akiba M M Izumiya H H Connor T R TR Suchard M A MA Lemey P P Mellor D J DJ Haydon D T DT Thomson N R NR

Science (New York, N.Y.) 20130912 6153

The global epidemic of multidrug-resistant Salmonella Typhimurium DT104 provides an important example, both in terms of the agent and its resistance, of a widely disseminated zoonotic pathogen. Here, with an unprecedented national collection of isolates collected contemporaneously from humans and animals and including a sample of internationally derived isolates, we have used whole-genome sequencing to dissect the phylogenetic associations of the bacterium and its antimicrobial resistance genes ...[more]

PMID: 24030491

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Project description:Salmonella spp. are estimated to cause 1.2 million cases of human foodborne illness each year in the United States, and pigs can often be asymptomatically colonized with Salmonella spp. (>50% of farms). Recent reports state that 18.3% of Salmonella enterica serovar Typhimurium isolates are resistant to ≥3 antimicrobial classes, and multidrug-resistant (MDR) strains are associated with an increased hospitalization rate and other complications. Chlortetracycline is commonly used in swine production to prevent/treat various diseases; therefore, chlortetracycline treatment of pigs unknowingly colonized with MDR Salmonella may have collateral effects on Salmonella spp. (and other gut bacteria). In this study, we determined the effect of in-feed chlortetracycline (400 g/ton) on shedding and colonization of pigs challenged with the MDR S Typhimurium strain DT104 (n = 11/group). We also assessed the impact on the fecal microbiota over the 12-day experimental period and on the ileum, cecum, and tonsil microbiota at 7 days postinoculation (dpi). In MDR S Typhimurium-inoculated pigs, chlortetracycline administration significantly increased fecal shedding at 2 dpi (+1.4 log10 CFU/g; P < 0.001) and enhanced tonsil colonization (+3.1 log10 CFU/g; P < 0.001). There were few major alterations detected in the gut or tonsillar microbiota of pigs treated with MDR S Typhimurium and/or chlortetracycline. The tonsillar transcriptome was largely unaffected despite increased colonization by MDR S Typhimurium following inoculation of the chlortetracycline-treated pigs. These results highlight the idea that chlortetracycline administration can enhance shedding and colonization of MDR S Typhimurium in pigs, which could increase the risk of environmental dissemination of MDR Salmonella strains.IMPORTANCESalmonella spp. are an important cause of foodborne illness in North America, and pork products are associated with sporadic cases and outbreaks of human salmonellosis. Isolates of Salmonella may be resistant to multiple antibiotics, and infections with multidrug-resistant (MDR) Salmonella spp. are more difficult to treat, leading to increased hospitalization rates. Swine operations commonly use antimicrobials, such as chlortetracycline, to prevent/treat infections, which may have collateral effects on pig microbial populations. Recently, we demonstrated that chlortetracycline induces the expression of genes associated with pathogenesis and invasion in MDR Salmonella enterica serovar Typhimurium in vitro In our current study, we show increased tonsillar colonization and fecal shedding of the MDR S Typhimurium strain DT104 from pigs administered chlortetracycline. Therefore, pigs unknowingly colonized with multidrug-resistant Salmonella spp. and receiving chlortetracycline for an unrelated infection may be at a greater risk for disseminating MDR Salmonella spp. to other pigs and to humans through environmental or pork product contamination.

Dataset Information

Distinguishable epidemics of multidrug-resistant Salmonella Typhimurium DT104 in different hosts.

Publications

Distinguishable epidemics of multidrug-resistant Salmonella Typhimurium DT104 in different hosts.

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