Conjugative plasmids among Antibiotic Resistance Escherichia Coli Isolates from Hospitals in Kerman, Iran

The emergence of multiple antibiotic resistance among Escherichia coli strains has created problems in the treatment of infections caused by this organism at hospitals. In this regard, transferring of the antibiotic resistance from resistant to sensitive strains by conjugation plays an important role in this phenemenon. In this research more than 50 strains of E.coli were isolated from different hospitals over one year (1999-2000) in Kerman. Among them, 10 strains which exhibited the highest level of the resistances to antibiotics were selected for further study. The sensitivity ofthe isolates to antibiotics were evaluated by the MIC and disc diffusion tests. Conjugation was done by the membrane filter technique and plasmids were isolated by the alkaline lysis method. 45% of the isolates were from faece, 35% from urine and 20% from blood. All the isolates had resistance to tetracycline, ampicillin and amoxycillin. Among the resistant strains, only the strain no. 3 was capable oftransfering Amp' and Arnox' [r = resistance] genes to the sensitive strain of E.coli K12 SG20030.1 (Rif f) by the conjugation process, Cotransfer study indicated that both Amox' and Amp' are transferred to recipient cells simultaneously. Agarose gel electrophoresis of the plasmids revealed that the strains 2, 3 and 7 contain plasmids, however only the strain 3 carried a conjugative one. Comparison between the growth phase of the doner and transconjugants did not show any differences. Only the lag phase was extended when the antibiotic was added. Based on the results, it can be concluded that conjugative plasm ids may playa role in the dessimination of antibiotic resistance genes in E.coli at hospitals.