Experiences with the typing of coagulase-negative staphylococci and micrococci.

Strains of coagulase-negative staphylococci and micrococci from many sources were biotyped and tested with a set of 20 phages, 19 of which were described by Dean et al. Strains resistant to many antibiotics were generally untypable with these phages. Nearly 50% of untypable strains could be typed by "reverse" typing--the characterisation of strains by the pattern of lysis given by their supernates on the propagating strains for the typing phages. This method was also used to clarify the relationship between isolates from an outbreak of septicaemia in a cardiac unit.