Purpose: The objective of this study was to characterize antimicrobial resistance, genotypes, integrons, virulence genes, and plasmids in ESBL-producing E. coli isolates that were obtained from imported meat in Korea.
Methods: Antimicrobial susceptibility test, multilocus sequence typing (MLST), detection of integrons, β-lactamase, and virulence factors by PCR, plasmid replicon typing, and repetitive sequence-based PCR (rep-PCR) DNA fingerprinting were carried out.
Results: A total of twenty ESBL-producing E. coli strains were isolated from imported pork and chicken in Korea and they were resistant to ampicillin, cefazolin, cefepime, cefpodoxime, ceftriaxone, cephalothin, and gentamicin. Fifteen different MLST types and four CTX-M groups (1, 2, 8, and 9) were identified. PCR was carried out for the detection of integrase genes Int1, Int2 and Int3, integron-associated aadA1, aadA5, sulI, and qacEΔ1 genes, and β-lactamase genes blaOXA and blaCMY. Only three genes, int1, qacEΔ1 and blaOXA-1, were found in CC22 and EC12-5 strains. Among 31 tested virulence factor genes, P-fimbriae assembly (papC), P fimbria tip pilins (papEF), P fimbria adhesin (papG) allele II, type 1 fimbriae (fimH), aerobactin (lutA), O antigen polymerase (rfc), and serum resistance associated (traT) were detected in CC21, CC22, ES92, EC12-5, and EC12-6 isolates. The IncFIB plasmid replicons were present in all isolates, followed by IncI1 (80%), IncFIA (65%), IncHI1 (40%), and IncB/O (35%). IncA/C, IncFIC, IncFIIA, IncHI2, IncK/B, IncL/M, IncN, IncT, IncW, and IncX were not detected. The dendogram analysis of rep-PCR showed 4 major clusters for 80% similarity cut-off.
Significance: The presence of ESBL-producing E. coli harboring virulence factors in imported meat suggests that it could be a great public health concern.