Antimicrobial pressure in healthy breeding dogs vs household animals assessed through the resistance profile of Escherichia coli and coagulase positive Staphylococci

Antimicrobials are sometimes inappropriately administered in dog breeding facilities in an attempt to improve fertility or reduce neonatal losses, but these practices lead to an increased prevalence of resistant bacteria. The aim of this study was to assess antibiotic use intensity in breeding kennels by comparing the resistance profiles of Escherichia coli and coagulase positive Staphylococci isolated from breeding bitches and from household animals. A rectal and a perivulvar swab were collected from 80 healthy bitches, half of which were housed in breeding kennels and the other half in domestic environments. The resistance of Escherichia coli, Staphylococcus pseudintermedius and S.aureus to a range of antimicrobials was evaluated through the Minimum Inhibitory Concentration test. Antibiotic resistance rates, the percentage of Extended Spectrum Beta-Lactamase (ESBL)-producing E.coli strains, the percentage of mecA positive methicillin-resistant Staphylococci and of Multi-Drug Resistant (MDR) isolates were compared between breeding bitches and privately owned ones using Fisher's exact test. The percentage of resistance to the antimicrobials tested was generally higher in dogs from breeding kennels than in owned animals, with statistically significant differences in E.coli for cefazolin (p < 0.0001), third-generation cephalosporins (p = 0.0015), tetracycline (p = 0.0079), kanamycin (p = 0.0291) and trimethoprim-sulfamethoxazole (p = 0.0007). Furthermore, the prevalence of ESBL E.coli was significantly higher in breeding dogs (p = 0.0002). 38.5 % of breeding bitches and 12.5 % of household dogs carried methicillin-resistant mecA positive S.pseudintermedius strains. S.aureus was only isolated from household animals, and one of the three isolates was mecA positive and MDR. Our data indicate a higher exposure of kennel dogs to antimicrobials. The pattern of antibiotic resistance, particularly to aminopenicillins but also to amoxicillin-clavulanic acid, suggests a large use of these agents. The results confirm that healthy dogs can harbour commensal bacteria that have acquired antimicrobial resistances, which may be exchanged between hosts; the potential role of the two dog typologies as reservoirs for resistance genes was demonstrated. The risk of household dogs being exposed to resistant bacteria, probably of human origin, was also observed. Our study reveals a generally high exposure of dogs to antimicrobials and highlights the need to sensitise veterinarians and breeders to better antibiotic stewardship.