Antimicrobial susceptibility and plasmids from escherichia coli isolated from rats

OBJECTIVES: To determine if antimicrobial resistance occurs in E. coli isolated from rats and if this resistance is transferable via plasmids. METHODS: Sixty Escherichia coli isolates obtained from 215 rats trapped in and around Nairobi, Kenya, were analysed for antimicrobial susceptibility to eleven commonly used antimicrobials. Plasmid DNA analysis and in-vitro conjugation tests were conducted on twenty two resistant isolates. RESULTS: A total of 12 (20%) E. coli were resistant to at least one of the commonly used drugs including ampicillin, sulphamethoxazole and streptomycin. Eight (13.3%) isolates were multidrug resistant. The drug resistant E. coli fell into five plasmid profile groups with plasmids ranging between two and 98 megadaltons (Mda). Resistance to ampicillin was transferable. CONCLUSION: The results of this study show that rats from the study area may form an important reservoir for drug-resistant E. coli that could pose a public health hazard.