Occurrence of antimicrobial-resistant bacteria from client-owned pets and their
raw meat-based diets
Advocates of raw-meat diets claim various health benefits for dogs, and while none of
the purported benefits have been validated, owners of raw meat-fed animals stand by
their convictions (1-4). In contrast, a 2-year study conducted by the US Food and Drug
Administration found that raw pet food is more likely than other types of pet food to carry
bacteria, including Salmonella and Listeria monocytogenes (5). The FDA issued a
public health warning about the risks of raw pet food diets and both the American
Animal Hospital Association and the American Veterinary Medical Association officially
recommend against feeding raw meat-based diets to dogs.
Numerous studies have validated the concerns associated with raw food diets (RFD),
but none has determined the prevalence of drug resistant bacteria (6-8). To address
this question, fecal specimens will be collected from animals fed a RFD. Samples will
also be collected from animals on a commercial diet, but also receiving antibiotics and
others considered antibiotic naïve. The survey focus will be on multidrug resistant
bacteria including vancomycin-resistant enterococci (VRE), carbapenemase-producing
bacteria and colistin resistant Enterobacteriaceae, but random enteric isolates will be
selected for testing for antimicrobial resistance.
Fecal samples will be submitted in Cary-Blair medium and inoculated onto imipenem
containing MacConkey agar to select for carbapenem-resistant bacteria. Lucie Bardet-
Jean Marc Rolain media will be utilized to select for colistin-resistant bacteria and VRE
(9). Conventional biochemical testing including the Vitek 2 Gram-positive and Gram-
negative ID cards (BioMerieux) will be utilized for bacterial identifications (10).
Antimicrobial susceptibility profiles will be determined by micro broth dilution (Sensititre®
automated system; Trek Diagnostics, Westlake, OH, USA) and will include
antimicrobials utilized in the National Antimicrobial Monitoring System. Isolates that are
ESBL positive will undergo multiplex qPCR for the extended spectrum beta lactamases
blaTEM, blaSHV, blaCTX-M and blaCMY-2 and sequencing to determine the variant
(11, 12). Multiplex qPCR platforms will be utilized to examine for plasmid mediated
colistin resistance genes: mcr-1 to-mcr-9 and tet (M), tet (L), cat, cmlA which confer
resistance to the tetracyclines and phenicols (13, 14).