BMC Microbiol. 2026 Jan 29. doi: 10.1186/s12866-026-04786-2. Online ahead of print.
ABSTRACT
BACKGROUND: Antimicrobial resistance (AMR) is a global threat. Escherichia coli is an important reservoir of resistance genes, and the coexistence of mcr with class 1 integron (intI1) is alarming, mcr confers resistance to colistin, a last-resort antibiotic, while intI1 often carries multiple transferable resistance determinants. Although colistin use in livestock is banned in Bangladesh, data on colistin-resistant E. coli in food animals, particularly cattle, remain scarce. This study investigated multidrug-resistance patterns, biofilm formation, and the prevalence of intI1 and its association with mcr and other resistance determinants in E. coli from Bangladeshi cattle.
METHODS: A total of 254 samples (feces, rectal swabs, soil, and water) were collected from cattle farms across three divisions of Bangladesh (Dhaka, Sylhet, and Barisal). E. coli isolates were identified using culture methods and confirmed with the VITEK-2 system and PCR. Antimicrobial susceptibility testing was performed using VITEK-2 system following CLSI guidelines. The presence of class 1 integron and mcr (mcr-1 to mcr-5) genes was detected by PCR. Biofilm formation was assessed using the crystal violet assay. Statistical analysis was conducted in R using Chi-square exact test, with significance set at p < 0.05.
RESULTS: E. coli was detected in 76.4% of samples, with the highest prevalence in feces (86.8%). Antimicrobial testing revealed complete sensitivity to several antibiotics, but resistance occurred to cefuroxime (33%), ciprofloxacin (26.8%), and amoxicillin-clavulanic acid (22.2%), with all isolates showing intermediate response to colistin. Overall, 29.4% of isolates were MDR, though no XDR or PDR were detected. Class 1 integron was present in 52.6% and the mcr-1 gene in 21.7%, both significantly associated with MDR (p < 0.001). Water isolates showed the highest proportion of strong biofilm producers (25.5%).
CONCLUSION: This study reveals a high prevalence of class 1 integron and the mcr-1 gene in MDR E. coli from food animals in Bangladesh, highlighting their role in resistance dissemination and the public health risk of colistin resistance. The strong association of integron with MDR and mcr-1 underscores the need for prudent antibiotic use, routine surveillance, and stronger antimicrobial stewardship in livestock to limit the spread of resistance to humans.
PMID:41612201 | DOI:10.1186/s12866-026-04786-2
