Bacteriophage analysis of staphylokinase-negative Staphylococcus aureus strains isolated from people

Staphylokinase is one of virulence factors produced by Staphylococcus aureus strains. Producing it is associated with the presence of prophage in a bacterial cell which carries the sak gene. In this study, we examined the ability to produce staphylokinase by 257 S. aureus strains isolated from the inpatient and the outpatients (carriers) and the fact whether there is a correlation between sensitivity to bacteriophages and the lack of producing staphylokinase by strains. The results of this study showed, that staphylokinase-negative strains of S.aureus are widely common inpatients and among outpatients and their percentage does not usually exceed 20% of staphylococci. All staphylokinase-negative S. aureus strains were negative for sak gene. The correlations between a type of clinical material and the frequency of occurrence of staphylokinase-negative strains has not been stated. Typing with the use of the basic set of phages has shown that these strains do not constitute a homogenous group and they belong to different phage types. The same phage patterns occur both in staphylokinase-negative strains and in staphylokinase-positive strains, and the differences in phage types have the quantitative character. S.aureus not producing staphylokinase are more frequently common in the phage group II than other phage groups (p < 0.0001) and are typed mainly by 3C and 55 phages. Staphylokinase-negative strains of S. aureus do not occur among the phage group II of strains sensitive to phage 71.