Diversity of CTX-M Extended-Spectrum β-Lactamases in Escherichia coli Isolates from Retail Raw Ground Beef: First Report of CTX-M-24 and CTX-M-32 in Algeria
Résumé
The aim of this study was to investigate the prevalence and molecular features of extended-spectrum cephalosporin
resistance in Escherichia coli isolates contaminating ground beef at retail in Algeria. Of 371 ground
beef samples, 27.5% were found to contain cefotaxime-resistant E. coli isolates distributed into A (24.5%), B1
(60.8%), and D (14.7%) phylogroups. A rate of 88.2% of isolates had a multidrug-resistance phenotype. All
strains were producers of CTX-M type extended-spectrum b-lactamases (ESBLs): CTX-M-1, CTX-M-3, CTXM-
14, CTX-M-15, CTX-M-24, or CTX-M-32. Conjugation assays allowed the transfer of blaCTX-M-1 in association
with IncI1 plasmids, blaCTX-M-15 with IncI1 and IncK+B/O plasmids, blaCTX-M-3 with IncK plasmids,
and blaCTX-M-14 with IncF1B or IncK plasmids. Sequence analysis of gyrA and parC genes showed mutations in
98.6% of ciprofloxacin-resistant isolates. The patterns ‘‘GyrA: S83L+D87N, ParC: S80I’’ (46.5%) and ‘‘ParC:
S80I’’ (42.3%) were predominant. qnrS1, qnrB, and aac(6¢)-Ib-cr were detected in 18.7% of isolates. The tet
genes, tetA, tetB, and tetA+tetB, were present in 95.7% of tetracycline-resistant isolates. The sul genes (sul1,
sul2, sul3, sul1+sul2, sul2+sul3, and sul1+sul3) and the dfr gene clusters (dfrA1, dfrA5, dfrA7, dfrA8, dfrA12,
dfrA5+dfrA12, dfrA1+dfrA5, dfrA7+dfrA12, dfrA5+dfrA7, and dfrA1+dfrA5+dfrA7) were found in 96.4% and
85.5% of sulfamethoxazole/trimethoprim-resistant isolates, respectively. Classes 1 and 2 integrons were detected
in 67.6% and 9.8% of isolates, respectively. This study highlighted the significant presence of resistance
genes, in particular those of CTXM ESBLs, in the beef meat, with the risk of their transmission to humans
through food chain.