Frequency of antimicrobial resistance and plasmid profiles of Escherichia coli strains isolated from milk

Abstract

Susceptibility to eight commonly used antimicrobial agents and plasmid profile analysis was done on forty one Escherichia coli strains isolated from milk. Most (95%) of the strains were resistant to sulphamethoxazole with a relatively low rate of resistance to the other antimicrobial agents. Twenty nine per cent of the isolates showed multiple resistance. The number of plasmids carried per strain was between 1 and 5, while plasmid sizes ranged between 107 and 1.0 megadaltons (MDa). There was no relationship between carriage of plasmids and antimicrobial resistance patterns.