[Antibiotic resistance and plasmids analysis in Staphylococcus aureus].

A total of 62 clinical strains of Staphylococcus aureus collected from Kaohsiung Medical College were examined for susceptibility of several antimicrobial agents and underwent plasmid analysis. The results of the antibiotic susceptibility test revealed that 33.9% were resistant to methicillin and 9.7% were resistant to gentamicin, whereas, resistance to heavy metal ions such as arsenic and cadmium were as high as 95% and 76% respectively. Antibiotic multiresistant isolates of S. aureus were also found. Multiresistance to nalidixic acid-tetracycline, ampicillin-nalidixic acid-tetracycline, and ampicillin-chloramphenicol-kanamycin-streptomycin- tetracycline were most frequently encountered. The phage typing results indicated that type 52 was predominant in 27%, followed by 11% of 52/83A and most strains fell into group I and a mixed group of I & III. In addition, these types expressed were highly correlated with a resistance to ampicillin, chloramphenicol, streptomycin, nalidixic acid, kanamycin and methicillin. Plasmid DNA profiles from these isolates exhibited different patterns. The plasmid of mol wt. 27 x 10(6) was associated with resistant to ampicillin and kanamycin, whereas, a plasmid of mol wt. 30 x 10(6) effected resistance to ampicillin, kanamycin and streptomycin. The determinant which conferred resistance to chloramphenicol was carried by a plasmid of mol wt. 3 x 10(6), and tetracycline resistance was encoded on a plasmid of mol wt. 2.8 x 10(6) or 28 x 10(6) in different isolated strains. Analysis of plasmids by HindIII digestion showed that plasmids of different molecular weight but with similar phenotypic characteristics often share common fragments.