Antibiotic-mediated expression analysis of Shiga toxin 1 and 2 in multi-drug-resistant Shiga toxigenic Escherichia coli.

Shiga toxin-producing Escherichia coli (STEC) is an important foodborne pathogens, known to cause enteric infections especially diarrhea, mainly attributed to Shiga toxins (Stxs). The use of certain antibiotics for treating this infection is controversial, owing to an increased risk for producing Stxs (Stx 1 and Stx 2). Increased antibiotic resistance is also thought to be involved in the pathogenesis of STEC diseases. The purpose of this study was to analyze the effects of antibiotics on induction of Stx 1 and Stx 2 in clinical STEC isolates and to investigate the relationships between increased resistance and Stx production. Fifteen clinical isolates were treated with sub minimum inhibitory concentrations (Sub MIC) of clinically used antibiotics (ciprofloxacin, fosfomycin, tigecycline, and meropenem), and the changes in expression levels of stx1 and stx2 genes were estimated using qRT-PCR. The expressions of Shiga toxins were found to be increased up to 6.5- and eightfold under ciprofloxacin and tigecycline Sub MIC, respectively. Fosfomycin had weak induction effect of up to twofold, whereas meropenem had the weakest influence on such expression. Resistant isolates were found to be more prone to increased expression of toxins.