Antibiotic resistance conferred by conjugative plasmid in Escherichia coli isolated from community ponds of Kathmandu Valley.

Bacteria can develop a variety of cellular mechanisms for acquiring resistance against antibiotics, including genetic mechanisms. Both commensal and pathogenic bacteria become resistant to every new antibiotic within few years of introduction. In recent years, antibioticresistant bacteria are being widely spread in nature. This can be due to the irrational use of sub-lethal concentrations of antibiotics in animal feeds and abuse of these substances in medical practice. The presence of antibiotic-resistant species of the Enterobacteraceae family in aquatic animal and human environments has given rise to considerable concern over the recent years. Faecally-contaminated natural water systems have revealed the presence of enteric micro-organisms with genetic factors, which control antibiotic resistance. Of them, enteric bacteria with plasmids are a growing public health concern. Conjugative and transductional transfer (R plasmid) of these factors among microbial strains in the aquatic environment has already been demonstrated (1,2,3).