[Minimal biochemical tests for interspecies identification in the Staphylococcus genus]

Abstract

A total of 50 different strains from clinical specimens and/or from experimental surgery were typified. The Staphylococcus genus was subdivided according to minimal test results for Staphylococcus genus differentiation into 3 groups: A. the coagulase-positive/novobiocin-susceptible species; B. the coagulase-negative/novobiocin-resistant species and C. the coagulase-negative/novobiocin-susceptible species. Species belonging to the different groups were differentiated by means of minimal biochemical tests readily available to all clinical bacteriology laboratories. To evaluate the predictive value of the procedure employed, the following strains were used as unknown: S. capitis, S. simulans, S. hominis, S. warneci, S. intermedius, S hyicus subsp. hycus, S hyicus subsp. chromogenes and S. haemolyticus. Results indicated that, for the coagulase-positive/novobiocin-susceptible group, the production of pigment and acetoin plus beta-galactosidase were sufficient for interspecies differentiation. For the coagulase-negative/novobiocin-resistant group, urease and phosphatase activity plus production of acid from xylose proved to be sufficient. The coagulase-negative/novobiocin-susceptible group required the greatest number of tests, due to phenotypical variability of species, including: reduction of nitrates; production of acetoin; use of arginine and the production of acid from maltose and/or trehalose. Preliminary findings justify routine application of these minimal tests for Staphylococcus genus differentiation.