Antimicrobial resistance patterns and plasmids of enteropathogenic Escherichia coli isolated in Nigeria

In an epidemiological study of enteropathogenic Escherichia coli, 102 strains were isolated from patients seen at the University Teaching Hospital in Lagos. The most common serotype encountered was 055 followed by 026. Antimicrobial susceptibility testing and plasmid profiling of the strains were done. All the strains were sensitive to colistin, nalidixic acid, nitrofurantoin, cefotaxime, amikacin, and augmentin. Of the 102 strains, 47 (46%) were resistant to one or more of the following antimicrobial agents: Co-trimoxazole, tetracycline, ampicillin, streptomycin, sulphonamide and a combination of ampicillin with sulbactam. All the strains that were resistant to any antimicrobial agents were also resistant to tetracycline. Seventy-two strains (70.6%) harbored plasmid whose molecular weights ranged from 0.8 to 120 x 10(6) daltons. The majority of the plasmid were smaller than 6 x 10(6); 90% of strains carrying plasmid ranging in size from 2 to 6 x 10(6) daltons and 50 to 70 x 10(6) daltons were resistant to one or more antimicrobial agents. Transformation and conjugation experiment showed that about 57% of the resistant strains carried R plasmid. Plasmid-determined resistance to tetracycline, ampicillin, streptomycin and sulphonamide was found.