|Fricke, W. Florian|
|Leclerc, J. Eugene|
Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/22/2009
Publication Date: 9/1/2009
Citation: Fricke, W., Mcdermott, P.F., Mammel, M.K., Zhao, S., Johnson, T.J., Rasko, D.A., Cray, P.J., Pedroso, A., Wichard, J.M., Leclerc, J., White, D.G., Cebula, T.A., Ravel, J. 2009. Antimicrobial resistance-conferring plasmids with similarity to virulence plasmids from avian pathogenic Escherichia coli strains in Salmonella enterica serovar Kentucky isolates from poultry. Applied and Environmental Microbiology. 75(18):5963-5971. Interpretive Summary: Salmonella enterica, a leading cause of food-borne gastroenteritis worldwide, may be found in any raw food of animal, vegetable, or fruit origin. There are over 2500 different serovars of Salmonella. Salmonella enterica serovar Kentucky, though often found in the food supply and in particular from chickens, is less commonly isolated from ill humans. Although treatment of gastroenteritis typically does not require antimicrobials, when they are needed it is critically important that they work as intended and stop the infection. Bacteria, including Salmonella, harbor small pieces of genetic material that enables them to acquire resistance to common antimicrobials. These pieces of genetic material, plasmids, can acquire enough resistance genes which can limit treatment options. We studied plasmids in S. Kentucky and discovered that they not only harbored genetic material making them resistant to killing with certain antimicrobials but they also had specific genes responsible for making them particularly prone to cause disease (virulent). Additional research is needed in order to examine the prevalence and spread of combined virulence and resistance plasmids in bacteria in agricultural, environmental, and clinical settings.
Technical Abstract: Salmonella enterica, a leading cause of food-borne gastroenteritis worldwide, may be found in any raw food of animal, vegetable, or fruit origin. Salmonella serovars differ in distribution, virulence, and host specificity. Salmonella enterica serovar Kentucky, though often found in the food supply, is less commonly isolated from ill humans. The multidrug-resistant isolate S. Kentucky CVM29188, isolated from a chicken breast sample in 2003, contains three plasmids (146,811 bp, 101,461 bp, and 46,121 bp), two of which carry resistance determinants (pCVM29188-146 [strAB and tetRA] and pCVM29188-101 [bla CMY-2 and sugE]). Both resistance plasmids were transferable by conjugation, alone or in combination, to S. Kentucky, Salmonella enterica serovar Newport, and Escherichia coli recipients. pCVM29188-146 shares a highly conserved plasmid backbone of 106 kb (>90% nucleotide identity) with two virulence plasmids from avian pathogenic Escherichia coli strains (pAPEC-O1-ColBM and pAPEC-O2-ColV). Shared avian pathogenic E. coli (APEC) virulence factors include iutA iucABCD, sitABCD, etsABC, iss, and iroBCDEN. PCR analyses of recent (1997 to 2005) S. Kentucky isolates from food animal, retail meat, and human sources revealed that 172 (60%) contained similar APEC-like plasmid backbones. Notably, though rare in human- and cattle-derived isolates, this plasmid backbone was found at a high frequency (50 to 100%) among S. Kentucky isolates from chickens within the same time span. Ninety-four percent of the APEC-positive isolates showed resistance to tetracycline and streptomycin. Together, our findings of a resistance-conferring APEC virulence plasmid in a poultry-derived S. Kentucky isolate and of similar resistance/virulence plasmids in most recent S. Kentucky isolates from chickens and, to lesser degree, from humans and cattle highlight the need for additional research in order to examine the prevalence and spread of combined virulence and resistance plasmids in bacteria in agricultural, environmental, and clinical settings.