Purpose: To determine the antibiotic resistance profiles and biofilm formation of E. coli isolates prevailing in farm environments in Northeast Mexico.
Methods: One hundred and seventy-two isolates of E. coli were obtained from tomato and jalapeño farm environments (produce, farmworkers’ hands, soil and water). The Kirby Bauer diffusion disc method was used to determine antibiotic resistance against nalidixic acid (30 μg), tetracycline (30 μg), gentamicin (10 μg), ciprofloxacin (5 μg), ampicillin (10 μg), trimethoprim/sulfamethoxazole (25 μg), cefotaxime (30 μg), ceftazidime (30 μg) and chloramphenicol (30 μg). Biofilm formation was quantified in microplates with broth after staining with crystal violet and measured spectrophotometrically. The biofilm formed was classified as strong, moderate or weak.
Results: A higher percentage of antibiotic resistance of isolates was observed against ampicillin (25% of isolates), and tetracycline (24% of isolates), followed by ceftazidime (21%), chloramphenicol (13%), cefotaxime (12%), nalidixic acid (10%), gentamicin (9%) and trimethoprim/sulfamethoxazole (7%). All strains were sensitive to ciprofloxacin. Higher resistance was observed in strains isolated from tomato, 38% of these isolates were resistant to ampicillin, whereas the isolates from jalapeño pepper were more resistant to tetracycline (23%). Biofilm production was observed by most strains (approximately 70%), 40% of the isolates produced a strong biofilm.
Significance: Information about antibiotic resistance or sensitivity and biofilm formation of wild E. coli strains is important for the establishment of control measures and for administration of appropriate antibiotics by health institutions.