Analysis of Plasmids of Clinically Isolated Serratia marcescens-Relation of Plasmids and Drug Resistance and Biochemical Characters

Abstract

Existence of the plasmid (s) in strains of Serratia marcescens isolated from urinary andrespiratory tract were examined. Thirty four strains (69%) of 62 strains isolated from urinary tractwere proved to be the plasmid-bearing strains but 26 strains (35%) of 74 strains isolatedfrom reapiratory tract were the plasmid-bearing strains. The numbers of plasmids detected in one strain was distributedfrom one to six plasmids in a strain depending on strains used. Their approximate molecularweight were fallen in the range of 2.5 to more than 60 megadaltons. The examination of drug sensitivityof S. marcescens with Tridisk method revealed that most of strains isolated from urinary tract werefully resistant to antibiotics such as erythromycin, cephaloridine, ampicilin and sulfisoxasole and partially to knanamycin, tetracycline, gentamycin, cephoxytin and nalidixic acid. However the strains isolated from respiratory tract were sensitive to most of these drugs except erythromycin, cephaloridineand sulfisoxasole which showed full resistant to these strains.
By transformation method with isolated plasmid DNA from urinary tract isolates some of these characters of drug resistance were transfered to Escherichia coli. Although plasmid DNAs isolated from about 60% of urinary tract strains could transfered the ability of resistance toantibiotics, ampicilin, kanamycin and gentamycin, to E. coli, only one plasmid DNA isolatedfrom respiratory tract strains could transfered the ability of resistance to ampicilin to E. coli. These resultssuggested that there was remarkable difference on drug resistance between strains isolated from urinary and respiratory tract and in strains isolated from urinary tract some of this drugresistance dependedof the existence of plasmids.