Extended-spectrum beta-lactamase - positive Escherichia coli in the feces of healthy people in Esfarvarin, Iran

Extended-Spectrum beta-Lactamase (ESBL) producing bacteria that can colonize the gut are often multi-drug resistant. The aim of this study was to determine ESBL-producing Escherichia coli (E. coli) isolated from the feces of healthy people in a small town of Iran. A total of 150 fecal samples from healthy humans were investigated in the community. These isolates were screened for ESBL production by the double disk synergy test. Susceptibility of isolated beta-lactamase producing E. coli to 12 antimicrobial agents was tested by the disk diffusion method. The PCR was applied to detect CTX-M, SHV and TEM genes in ESBL-positive strains. Fifty-two out of 150 (34.6%) isolates were ESBL-producers. The majority of ESBL-producing isolates were resistant to co-trimoxazole, tetracycline and nalidixic acid. The CTX-M, SHV, and TEM genotypes were found in 86.5%, 9.6%, and 3.8% of ESBL-positive E. coli, respectively. The CTX-M1 is the most prevalent (80.7%) beta-lactamase gene, followed by the SHV-12 and CTX-M14, TEM-116, CTX-M15, SHV-1 and CTX-M9. More than one-third of the E. coli isolates were ESBL producers. The high frequency of the CTX-M1 gene among E. coli isolates from the feces of healthy people is alarming. So, it is important to monitor ESBL-producing E. coli in order to avoid spread of resistant isolates in the community.