Mechanisms of antimicrobial resistance and genetic relatedness among enterococci isolated from dogs and cats in the United States.
OBJECTIVE
In this study, mechanisms of antimicrobial resistance and genetic relatedness among resistant enterococci from dogs and cats in the United States were determined.


RESULTS
Enterococci resistant to chloramphenicol, ciprofloxacin, erythromycin, gentamicin, kanamycin, streptomycin, lincomycin, quinupristin/dalfopristin 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 approx. 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 pulsed-field gel electrophoresis (PFGE), isolates clustered according to enterococcal species, source and antimicrobial gene content and indistinguishable patterns were observed for some isolates from dogs and cats.


CONCLUSIONS
Enterococci from dogs and cats may be a source of antimicrobial resistance genes.


CONCLUSIONS
Dogs and cats may act as reservoirs of antimicrobial resistance genes that can be transferred from pets to people. Although host-specific ecovars of enterococcal species have been described, identical PFGE patterns suggest that enterococcal strains may be exchanged between these two animal species.
Jackson
C R
CR
Bacterial Epidemiology and Antimicrobial Resistance Research Unit, USDA-ARS Russell Research Center, Athens, GA 30605, USA. charlene.jackson@ars.usda.gov
Fedorka-Cray
P J
PJ
Davis
J A
JA
Barrett
J B
JB
Brousse
J H
JH
Gustafson
J
J
Kucher
M
M
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002415:Cats / Q000382:microbiology*; D004285:Dogs / Q000382:microbiology*; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D016983:Enterococcus / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D005798:Genes, Bacterial; D014644:Genetic Variation; D008826:Microbial Sensitivity Tests; D057805:Pets / Q000382:microbiology; D014481:United States
D000900:Anti-Bacterial Agents