CRYSTAL VIOLET REACTIONS OF COAGULASE-NEGATIVE STAPHYLOCOCCI

Twenty four reference strains and 112 clinical isolates of coagulase n egative staphylococci (CNS) were examined for their reactions in the c rystal violet test. Some species gave a white reaction and others a pu rple reaction. Results were consistent and reproducible and each speci es gave only one pattern of crystal violet reaction. Within the limite d variety of species represented in the clinical isolates, Staphylococ cus saprophyticus and S haemolyticus gave crystal violet purple reacti ons, in contrast to S epidermidis, which always gave a white reaction. Investigations suggested that the mechanism of the crystal violet tes t in S haemolyticus may be similar to that previously described in S a ureus. Further work is needed to characterise the ability of crystal v iolet to modify S epidermidis and other central nervous system species . The crystal violet reaction, which has strong associations with inva siveness, phage group susceptibilities, colonisation persistence abili ties, and nosocomial origin in S aureus may also be useful in studies of CNS disease.