Isolation, Identification and Antimicrobial Resistance Analysis of Canine Oral and Intestinal Escherichia coli Resistant to Colistin

In recent years, the antimicrobial resistance in Escherichia coli has gradually developed into a global problem. These resistant bacteria could be transmitted to humans through animal feces in the environment or direct contact with pets, leading to a problem in bacterial treatment for humans and animals. Now, the antibiotic resistance of oral and intestinal microbiota from dog origins remains unclear in China. Therefore, this study first analyzed the current colistin resistance of oral and intestinal microbiota from dog origins in mainland China. A total of 536 samples were collected from dogs in mainland China and, respectively, cultured on the SS and MacConkey agar plate containing colistin (4 μg/mL) to obtain bacteria, and the antibiotic-resistance phenotype of Escherichia coli was investigated for nine antibiotics. Results showed that a total of 2259 colistin-resistant bacteria were isolated from samples and identified, and among them, the isolated rate of Escherichia coli (34.01%, 769/2259) was relatively higher than that of other bacteria. Subsequently, it was found that the resistance of these Escherichia coli was very severe by exploring its resistance to different antibiotics, particularly to three common antibiotics in a clinic which were ceftriaxone, ampicillin and trimethoprim/sulfamethoxazole, with the resistance rates of 60.60% (466/769), 57.22% (440/769), and 53.06% (408/769), respectively. Moreover, the simultaneous resistance of Escherichia coli to one or more antibiotics was determined, and 69.96% (538/769) strains have defined the resistance to both two or more antibiotics, and even 13 of Escherichia coli strains that were resistant to all nine antibiotics, indicating that the Escherichia coli from dog origins has severe antibiotic resistance in the clinic. In conclusion, this study guided the use of antibiotics and could draw attention to antibiotic resistance in veterinary clinical treatment for animals in the future.