Abstract
Multiple-drug resistance bacteria containing antimicrobial resistance genes (ARGs) are a concern for public health. Integrons are bacterial genetic elements that can capture, rearrange, and express mobile gene cassettes responsible for the spread of ARGs. Few studies link genotype and phenotype of swine-related ARGs in the context of mobile gene cassette arrays among commensal Escherichia coli (E. coli) in nonclinical livestock isolates from intensive farms. In the present study, a total of 264 isolates were obtained from 330 rectal swabs to determine the prevalence and characteristics of antibiotic-resistant gene being carried by commensal E. coli in the healthy swine from four intensive farms at Anhui, Hebei, Shanxi, and Shaanxi, in China. Antimicrobial resistance phenotypes of the recovered isolates were determined for 19 antimicrobials. The E. coli isolates were commonly nonsusceptible to doxycycline (75.8%), tetracycline (73.5%), sulfamethoxazole-trimethoprim (71.6%), amoxicillin (68.2%), sulfasalazine (67.1%), ampicillin (58.0%), florfenicol (56.1%), and streptomycin (53.0%), but all isolates were susceptible to imipenem (100%). Isolates [184 (69.7%)] exhibited multiple drug resistance with 11 patterns. Moreover, 197 isolates (74.6%) were detected carrying the integron-integrase gene (intI1) of class 1 integrons. A higher incidence of antimicrobial resistance was observed in the intI1-positive E. coli isolates than in the intI1-negative E. coli isolates. Furthermore, there were 17 kinds of gene cassette arrays in the 70 integrons as detected by sequencing amplicons of variable regions, with 66 isolates (94.3%) expressing their gene cassettes encoding for multiple drug resistance phenotypes for streptomycin, neomycin, gentamicin, kanamycin, amikacin, sulfamethoxazole-trimethoprim, sulfasalazine, and florfenicol. Notably, due to harboring multiple, hybrid, and recombination cassettes, complex cassette arrays were attributed to multiple drug resistance patterns than simple arrays. In conclusion, we demonstrated that the prevalence of multiple drug resistance and the incidence of class 1 integrons were 69.7 and 74.6% in commensal E. coli isolated from healthy swine, which were lower in frequency than that previously reported in China.
Highlights
Antimicrobial-resistant bacteria, especially multiple drug-resistant (MDR) strains have caused many outbreaks of food-borne diseases and infectious diseases worldwide, threatening human and animal health (Paitan, 2018)
We investigated the prevalence of antimicrobial resistance in 264 E. coli isolates recovered from rectal swabs
A Lower and Still Challenging Prevalence of Antimicrobial Resistance E. coli in Anhui, Hebei, Shanxi, and Shaanxi
Summary
Antimicrobial-resistant bacteria, especially multiple drug-resistant (MDR) strains have caused many outbreaks of food-borne diseases and infectious diseases worldwide, threatening human and animal health (Paitan, 2018). Integrons located on either chromosome or mobile genetic elements (MGEs), such as plasmids and transposons, are considered responsible for the horizontal gene transfer of antimicrobial resistance (AMR; Stalder et al, 2012). Class 1 integrons in bacteria ubiquitously reside in gastrointestinal tracts of animals and humans, and their abundance and genetic diversity can readily change in response to environmental pressures (Alonso et al, 2017). Dynamic and diverse of E. coli populations exist in the swine intestinal microbiota and in the farm environment throughout the full production cycle, suggesting the potential for carriage of antimicrobial resistance and the presence of clinical integrons (Marchant and Morenoa, 2013; Van den Meersche et al, 2020)
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