ROLE OF BACTERIOPHAGES IN GENOMIC VARIABILITY OF RELATED COAGULASE-NEGATIVE STAPHYLOCOCCI

DNA analysis using pulsed-field gel electrophoresis (PFGE) has emerged as one of the most sensitive epidemiological tools for the characteri zation of coagulase-negative staphylococci (CNST). The significance of some minor differences observed between the DNA restriction pulsed pa tterns of two CNST strains are difficult to interpret since they can t heoretically be due to minor chromosomal rearrangements or to phage DN A integration. The latter possibility was investigated by comparing DN A restriction patterns of Staphylococcus epidermidis strains with thos e of their lysogenized derivatives. In vitro lysogenisation was obtain ed by exposing the strains to phage 118II. The pulsed patterns of the lysogenized strains were compared to those of their parental strains, revealing a shift in size of approximately 50 kb in a single band whic h was shown by Southern blotting to contain prophage. One strain was l ysogenized ten times, revealing a potential preferred attachment site for phage 118II. These results confirm that chromosomal integration of a phage can be responsible for minor stable variations in DNA restric tion patterns.