Antimicrobial Resistance, Extended-Spectrum β-Lactamase Productivity, and Class 1 Integrons in from Healthy Swine

Abstract

Administration of antimicrobials to food-producing animals increases the risk of higher antimicrobial resistance in the normal intestinal flora of these animals. The present cross-sectional study was conducted to investigate antimicrobial susceptibility and extended-spectrum β-lactamase (ESBL)-producing strains and to characterize class 1 integrons in Escherichia coli in healthy swine in Thailand. All 122 of the tested isolates had drug-resistant phenotypes. High resistance was found to ampicillin (98.4% of isolates), chloramphenicol (95.9%), gentamicin (78.7%), streptomycin (77.9%), tetracycline (74.6%), and cefotaxime (72.1%). Fifty-four (44.3%) of the E. coli isolates were confirmed as ESBL-producing strains. Among them, blaCTX-M (45 isolates) and blaTEM (41 isolates) were detected. Of the blaCTX-M-positive E. coli isolates, 37 carried the blaCTX-M-1 cluster, 12 carried the blaCTX-M-9 cluster, and 5 carried both clusters. Sequence analysis revealed blaTEM-1, blaTEM-135, and blaTEM-175 in 38, 2, and 1 isolate, respectively. Eighty-seven (71%) of the 122isolates carried class 1 integrons, and eight distinct drug-resistance gene cassettes with seven different integron profiles were identified in 43 of these isolates. Gene cassettes were associated with resistance to aminoglycosides (aadA1, aadA2, aadA22, or aadA23), trimethoprim (dfrA5, dfrA12, or dfrA17), and lincosamide (linF). Genes encoding β-lactamases were not found in class 1 integrons. This study is the first to report ESBL-producing E. coli with a class 1 integron carrying the linF gene cassette in swine in Thailand. Our findings confirm that swine can be a reservoir of ESBL-producing E. coli harboring class 1 integrons, which may become a potential health risk if these integrons are transmitted to humans. Intensive analyses of animal, human, and environmental isolates are needed to control the spread of ESBL-producing E. coli strains.

Antimicrobial Usage and Antimicrobial Resistance in Animal Production in Southeast Asia: A Review

“…In three publications, AMR was investigated in both E. coli and NTS isolates. The majority of publications included data from Thailand (20) [27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44] and Vietnam (15) [18,23,45,46,47,48,49,50,51,52,53,54,55]. One publication was found with data from each of Cambodia, Indonesia, Lao PDR and Malaysia [56,57,58,59].…”

“…Thirteen publications reported plasmid-mediated β -lactamase-encoding genes among E. coli and NTS isolates from pigs (11 publications) [32,36,39,46,48,101,102,103,104,105,106], poultry (8) [32,46,48,101,102,103,104,105], cattle (4) [46,48,49,104], and aquaculture (4) [46,101,104,105]. A total of nine different genes have been described in isolates from Thailand, Vietnam, Malaysia, Lao PDR, and Indonesia ( bla TEM , bla PSE-1 , bla CTX-M , bla SHV , bla OXA , tem A, tem B, MOX, and DHA).…”

“…CTX-M and TEM were the most common β -lactamase-encoding genes identified among ampicillin-resistant and/or ESBL-producing E. coli isolates [39,105]. CTX-M-1 and CTX-M-9 were the main CTX subgroups observed in E. coli isolates from chicken meat and pork (Vietnam) and healthy swine (Thailand) [39,105].…”

“…CTX-M-1 and CTX-M-9 were the main CTX subgroups observed in E. coli isolates from chicken meat and pork (Vietnam) and healthy swine (Thailand) [39,105]. In addition, CTX-M-55 was also found among colistin-resistant E. coli isolates from Vietnam [106].…”

“…In addition, CTX-M-55 was also found among colistin-resistant E. coli isolates from Vietnam [106]. PCR and sequence analysis revealed that extended spectrum beta-lactamase (ESBL)-positive E. coli isolated from healthy pigs in Thailand carried TEM-1, TEM-135, and TEM-176 subgroup genes [39]. To our knowledge, no studies have investigated the presence of ESBLs in NTS from meat or animals.…”