[Prevalence of markers characteristic for penicillinase plasmids in clinical strains of straphylococci].

Occurrence of the markers of penicillin and erythromycin resistance in the clinical strains of Staph. aureus, as well as their connection with the determinants of resistance to the heavy metal salts and sodium arsenate was studied. 79 per cent of Staph. aureus were resistant to penicillin and 47 per cent to erythromycin. All erythromycin resistant strains were also resistant to penicillin. More than a half of the strains of Staph. aureus of the phage groups I, III and the mixed phage group had a set of markers: pen, asa, cad, mer, ego. The rate of elimination of the above markers with ethidium bromide was high. The presence of the penicillinase plasmid determining a rather low level of resistance to erythromycin (20--50 gamma/ml) was characteristic of the strains belonging to the phage group I. The presence of the plasmid determining a high level of resistance to that drug (500--1000 gamma/ml) was characteristic of the phage group III and the mixed phage group. The erythromycin sensitive strains of Staph. aureus were almost always sensitive to mercuric ions.