Prevalence, identification of virulence genes, and antibiotic resistance properties of Shiga-toxin producing Escherichia coli (STEC) strains isolated from ice cream and juice in sales centers.

OBJECTIVE

Contaminated food with Shiga-toxin producing Escherichia coli (STEC) can cause diarrhea and severe diseases in consumers. This study aimed to assess the phenotypic and genotypic characteristics of virulence and antibiotic resistance genes in STEC strains isolated from various types of ice cream and fruit juice sold in Isfahan, Iran.

METHODS

From March 2023 to March 2024, 500 samples-including traditional ice cream (100), industrial ice cream (100), frozen ice cream (100), traditional juice (100), and industrial juice (100)-were collected. Samples were analyzed using biochemical and molecular methods for STEC detection. Antibiotic sensitivity was evaluated using the disc diffusion method against 14 antibiotics. Specific primers were used to identify antibiotic resistance and virulence genes.

RESULTS

Among the 500 samples, 52 (10.42%) were E. coli positive, with the highest prevalence found in traditional juice (20%) and traditional ice cream (15%). The pathogenic subtype, particularly enterohemorrhagic E. coli (EHEC), was most common in traditional juice (75% of positive samples) and traditional ice cream (66.66%). High antibiotic resistance rates were observed against ampicillin (86.53%), tetracycline (76.92%), and sulfamethoxazole (73.07%), while the lowest resistance was recorded for imipenem (7.69%). The most frequently detected antibiotic resistance genes were aadA1 (76.92%), tetA (57.69%), and sul1 (55.76%). Key virulence genes included stx1, stx2, and eaeA.

CONCLUSION

These findings emphasize the public health risks associated with STEC contamination in food products and the need for stricter food safety measures and antibiotic stewardship programs. These findings highlight the public health risks of STEC contamination in food products, particularly traditional ice cream and juice. Localized studies are essential to understand specific risks and inform targeted interventions. Strategies such as improved hygiene practices, stringent food safety regulations, and effective antibiotic stewardship programs are critical to mitigating the threat posed by STEC in food products.