Routine contact between human beings and companion animals may allow transmission of pathogenic and antimicrobial resistant bacteria between species. The goal of this study was to determine antimicrobial susceptibilities of E. coli isolates from healthy dogs and their owners.
Fecal swabs were collected from 61 healthy dog and human owner pairs and a control group of non-dog-owners. Volunteers were excluded if they had received antimicrobial therapy within 2 weeks. Three representative E. coli colonies were isolated from each sample. Susceptibilities were determined using a disc diffusion method for 17 antimicrobials included in the National Antimicrobial Resistance Monitoring System.
In all groups, lowest percent susceptibility was to cephalothin (48% susceptibility in dogs, 59% in owners, 60% in controls), ampicillin (67% in dogs, 61% in owners, 50% in controls), and amoxicillin-clavulanic acid (80% in dogs, 87% in owners, 80% in controls). Imipenem was the only antimicrobial to which all isolates were susceptible. Susceptibility patterns of isolates from dog owners and controls, and from paired dog owners and dogs, were compared using Chi-square and McNemar Chi-square analyses, respectively, and no significant differences were found between groups or within households. Multiple drug resistance (MDR), defined as resistance to 3 or more antimicrobial agents, was seen in 4/61 (7%) dogs, 10/61 (16%) owners, and 5/30 (17%) controls; differences between groups were not significant (P=0.10).
In conclusion, antimicrobial resistance, including MDR, was common among fecal E. coli isolates from healthy dogs and human beings. Dog ownership did not increase risk of harboring resistant fecal E. coli.