Antibiotic Susceptibility and R-Plasmid Mediated Drug Resistance in Staphylococcus Aureus

A total of twenty-eight Staphylococcus aureus strains were isolated from skin lesion samples. Results of antibiotic susceptibility test showed that these twenty-eight Staphylococcus aureus strains were resistant to ampicillin (72%), amoxycillin (72%), penicillin (72%), cotrimoxazole (15%), cloxacillin (50%) tetracycline (11%), cephradine (22%), cephalexine (7%) and nalidixic acid (18%). To understand whether this drug resistance phenomenon was plasmid mediated or not, plasmids were isolated from a chosen strain of Staphylococcus aureus (S2) and a 23 KB plasmid was obtained. This 23 KB plasmid was then transferred to an antibiotic sensitive E. coli LE 392 and after which the sensitive E. coli LE 392 strain developed drug resistance. Plasmid analysis of the transformed E. coli LE 392 revealed that it contains a 23 KB plasmid corresponding to that of the donor Staphylococcus aureus strain which may harbor the gene(s) encoding multidrug resistance in the donor Staphylococcus aureus.