PHAGE TYPING AND PHAGE INDUCTION IN CARRIER AND INVASIVE STAPHYLOCOCCUS-EPIDERMIDIS ISOLATES

Fifty-nine Staphylococcus epidermidis isolates (30 carrier and 29 invasive) were phage typed using the phage set developed by Pulverer. Poor results were obtained as only 24% of the invasive and 27% of the carrier isolates were typable, with no differences between these percentages (P > 0·05). Isolation of lysogenic phages present in the isolates was attempted by three different methods, induction being satisfactory only by overnight incubation with 0·1 mg l-1 mitomycin C and detection with 2,3,5-triphenyl-tetrazolium chloride. All isolates produced phages, and the lytic activity of these phages was expressed on more than 50% of the isolates in all cases (except one phage which lysed 10% of the carrier isolates and 13·8% of the invasive isolates). The percentages of isolates lysed in the two groups (carrier and invasive) were statistically different (P < 0·05) only for phages derived from four isolates. © 1991.