Plasmid profile analysis and antimicrobial susceptibility patterns of Shigella isolates from Nigeria

In an epidemiological survey, plasmid profiles and antimicrobial susceptibility testing of 100 shigella isolates in Lagos, Nigeria was done. All the isolates were sensitive to nalidixic acid, nitrofurantoin and ciprofloxacin. The commonest antimicrobial susceptibility pattern was resistance to ampicillin, colistin sulphate, co-trimoxazole, streptomycin and tetracycline. All but 4 of 100 isolates screened contained one or more plasmids. Plasmid profile analysis distinguished more strains than did antimicrobial susceptibility patterns. A total of 36 isolates was able to transfer resistance plasmids to Escherichia coli K-12 by conjugation. Using in vitro transformation, seven isolates transferred resistance. These plasmids specified resistance to tetracycline, streptomycin, sulphonamide, trimethoprim and ampicillin.