Antimicrobial Resistance in Escherichia coli Isolates from Swine and Wild Small Mammals in the Proximity of Swine Farms and in Natural Environments in Ontario, Canada

Abstract

Wild animals not normally exposed to antimicrobial agents can acquire antimicrobial agent-resistant bacteria through contact with humans and domestic animals and through the environment. In this study we assessed the frequency of antimicrobial resistance in generic Escherichia coli isolates from wild small mammals (mice, voles, and shrews) and the effect of their habitat (farm or natural area) on antimicrobial resistance. Additionally, we compared the types and frequency of antimicrobial resistance in E. coli isolates from swine on the same farms from which wild small mammals were collected. Animals residing in the vicinity of farms were five times more likely to carry E. coli isolates with tetracycline resistance determinants than animals living in natural areas; resistance to tetracycline was also the most frequently observed resistance in isolates recovered from swine (83%). Our results suggest that E. coli isolates from wild small mammals living on farms have higher rates of resistance and are more frequently multiresistant than E. coli isolates from environments, such as natural areas, that are less impacted by human and agricultural activities. No Salmonella isolates were recovered from any of the wild small mammal feces. This study suggests that close proximity to food animal agriculture increases the likelihood that E. coli isolates from wild animals are resistant to some antimicrobials, possibly due to exposure to resistant E. coli isolates from livestock, to the resistance genes of these isolates, or to antimicrobials through contact with animal feed.

Antimicrobial Susceptibility of Escherichia coli Isolates from Wild Mice in a Forest of a Natural Park in Hokkaido, Japan

“…The percentage of wild mice with antimicrobial-resistant E. coli isolates in this investigation (3.7%, 3/81) was as low as that among small wild mammals living in natural areas (10%, 2/20) [10]. It has been reported that the proximity of wild animals to human settlements and the livestock industry increases antimicrobial-resistance among E. coli isolates from wild animals [7,10].…”

“…The usage of antimicrobial agents is considered the most important factor in the selection and dissemination of antimicrobial-resistant bacteria. Although antimicrobial agents are not generally administered to wild animals, the prevalence of antimicrobial-resistant Escherichia coli isolates was determined in some wild animals [4,5,7,10,12,13]. The source of antimicrobial-resistant bacteria among wild animals is still debatable.…”

“…Using MacConkey agar plates, E. coli was isolated from 40 of 109 voles (36.7%), 34 of 52 large Japanese field mice (65.4%) and seven of 19 small Japanese field mice (36.8%, reported a low detection frequency of E. coli isolates (48.8%) from wild mice, voles and shrews even though enrichment for E. coli was performed [10]. The distribution of intestinal bacterial flora including E. coli might differ between wild mice and livestock.…”

“…DNA from the isolates was extracted with an InstaGene Matrix (Bio-Rad Laboratories Inc., Tokyo, Japan). The genes encoding TEM, SHV and CMY-2 β-lactamase were tested in ampicillin-and/or cefazolin-resistant isolates by multiplex PCR [10]. The strA, strB and aadA genes were tested in dihydrostreptomycinresistant isolates [11].…”

“…For detection of the strA and strB genes, the following primer pairs were used: strA-F, TGA CTG GTT GCC TGT CAG AG; strA-R, AAT TGC CGT TAT CAC CAA GC; strB-F, ACG TTT CGC AAC CTG TTC TC; and strB-R; AGG TTT CAA TCC CTT GAC GA. The aphA1 and aphA2 genes were tested in kanamycin-resistant isolates by multiplex-PCR [10]. The tetA and tetB genes were tested in oxytetracycline-resistant isolates [14].…”