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United States Department of Agriculture

Agricultural Research Service

Research Project: EPIDEMIOLOGY, ECOLOGY, AND MOLECULAR GENETICS OF ANTIMICROBIAL RESISTANCE IN PATHOGENIC AND COMMENSAL BACTERIA FROM FOOD ANIMALS Title: Mechanisms of antimicrobial resistance and genetic relatedness among enterococci isolated from dogs and cats in the United States

Authors
item Jackson, Charlene
item Cray, Paula
item Davis, Johnnie
item Barrett, John
item Brousse, Jr, James -
item Gustafson, Jennifer -
item Kucher, Monica -

Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 3, 2009
Publication Date: June 1, 2010
Citation: Jackson, C.R., Cray, P.J., Davis, J.A., Barrett, J.B., Brousse, Jr, J.H., Gustafson, J., Kucher, M. 2010. Mechanisms of antimicrobial resistance and genetic relatedness among enterococci isolated from dogs and cats in the United States. Journal of Applied Microbiology. 108(6):2171-2179.

Interpretive Summary: The contribution of dogs and cats as reservoirs of antimicrobial resistant enterococci remains largely undefined. This is increasingly important considering the possibility of transfer of bacteria from companion animals to the human host. In this study, antimicrobial resistant enterococci from dogs and cats from veterinary clinics were screened for the presence of resistance genes. Genetic relatedness among the isolates was also determined. Enterococci resistant to chloramphenicol, ciprofloxacin, erythromycin, gentamicin, kanamycin, streptomycin, lincomycin, Quinupristin/Dalfopristin (Q/D), and tetracycline were screened for the presence of 15 antimicrobial resistance genes. Five tetracycline resistance genes were detected with tet(M) accounting for approximately 60% (130/216) of tetracycline resistance; the erm(B) gene was also widely distributed among 96% (43/45) of the erythromycin resistant enterococci. Five aminoglycoside resistance genes were also detected among the kanamycin resistant isolates with the majority of isolates (25/36; 69%) containing aph(3”)-IIIa. The bifunctional aminoglycoside resistance gene, aac(6’)-Ie-aph(2”)-Ia, was detected in gentamicin resistant isolates and ant(6)-Ia in streptomycin resistant isolates. Using Pulsed-field Gel Electrophoresis (PFGE), isolates clustered according to enterococcal species, source and antimicrobial gene content. Results from this study indicate that healthy dogs and cats are a source of antimicrobial resistant enterococci that harbor resistance genes that can be transferred to the human host. This research will be useful to policy makers and researchers studying the role that companion animals have in the dissemination and persistence of antimicrobial resistance in humans which may impact human health.

Technical Abstract: Aims: In this study, mechanisms of antimicrobial resistance and genetic relatedness among resistant enterococci from dogs and cats in the United States were determined. Methods and Results: Enterococci resistant to chloramphenicol, ciprofloxacin, erythromycin, gentamicin, kanamycin, streptomycin, lincomycin, Quinupristin/Dalfopristin (Q/D), and tetracycline were screened for the presence of 15 antimicrobial resistance genes. Five tetracycline resistance genes [tet(M), tet(O), tet(L), tet(S) and tet(U)] were detected with tet(M) accounting for approximately 60% (130/216) of tetracycline resistance; erm(B) was also widely distributed among 96% (43/45) of the erythromycin resistant enterococci. Five aminoglycoside resistance genes were also detected among the kanamycin resistant isolates with the majority of isolates (25/36; 69%) containing aph(3”)-IIIa. The bifunctional aminoglycoside resistance gene, aac(6’)-Ie-aph(2”)-Ia, was detected in gentamicin resistant isolates and ant(6)-Ia in streptomycin resistant isolates. The most common gene combination among enterococci from dogs (n=11) was erm(B), aac(6')-Ie-aph(2")-Ia, aph(3")-IIIa, tet(M), while tet(O), tet(L) were most common among cats (n=18). Using PFGE, isolates clustered according to enterococcal species, source and antimicrobial gene content. Conclusion: Enterococci from dogs and cats may be a source of antimicrobial resistance genes. Significance and Impact of Study: Dogs and cats may act as reservoirs of antimicrobial resistance genes that can be transferred from pets to people.

Last Modified: 11/24/2014
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