Mannose inhibition as a significant marker for differentiating among novobiocin-resistant staphylococci of relevance in clinical microbiology.

A specific method for the identification of Staphylococcus saprophyticus among novobiocin-resistant species isolated from man is described. The test is based on novobiocin resistance, non-fermentation of D-mannose and early inhibition with late secondary growth on glucose/mannose + novobiocin agar plates. On this medium novobiocin-resistant Staphylococcus cohnii showed a confluent, continuous and homogeneous growth after 24 h which remained unchanged at 48 h whether or not it fermented D-mannose, whereas novobiocin-resistant Staphylococcus xylosus fermented D-mannose. These results are discussed in relation to a possible causal role of PTS enzymes and phosphomannose isomerase deficiency in mannose inhibition.