ABSTRACT
Ninety nine strains of Escherichia coli isolated from clinical urine specimens in Taegu area were tested for the antimicrobial susceptibility to 20 drugs and studies for molecular and genetic characterization of R-plasmid. All strains were susceptible to amikacin (Ak), moxalactam(Mx), norfloxacin(Nf), ciprofloxacin(Cf) and ofloxacin(Of). One-6.1% of the strains were resistant to tobramycin(To). nalidixic acid(Na), enoxacin(Ex), pefloxacin(Pf) and rifampin(Rf), 17.2-31.3% to gentamicin(Gm), cephalothin(Ct) and cephamandole(Cfm), and 59.6-84.4% to kanamycin (Km), streptomycin(Sm), a.mpicillin(Ap), chloramphenicol(Cm), tetracycline(Tc), sulfisomidine (Su) and trimethoprime(Tp). MIC90 of Ak, Mx, Ex, Nf, Cf, Of and Pf were below the aritimicrobial concentration tested. In multiple drug resistance patterns, resistance to 7 drugs (CmTcSmSuAp TpKm) were most frequently encountered. Except Na and Rf in 66.4 % of resistant strains, most or drug resistance were co-transferred to recipient E.coli RG488 or RG176, indicating that multiple drug resistance was R-plasmid mediated phenomenon. Plasmid profiles for molecular characterization of R-plasmids from B. coli strains were studied through the methods of alkaline SDS lysis and agarose gel electrophoresis. R-plasmids were 40.9-122.3 mega dalton in molecular size. Pst I restriction enzyme digestion patterns of R-plasmid DNAs were examined. R-plasmids with different molecular weights and phenotype markers showed different restriction patterns. pDE9l58 and pDE 9055, which have same molecular weight and phenotype marker except Cfm, showed identical restriction pattern.