Abbreviated scheme for presumptive identification of Staphylococcus saprophyticus from urine cultures

Phosphatase-novobiocin-mannose-inhibition test (PNMI-test) for routine identification of the coagulase-negative staphylococcal urinary tract pathogens S. epidermidis and S. saprophyticus

A modified Kloos/Schleifer-scheme proved to be useful in identifying coagulase-negative staphylococci isolated from urine. S. epidermidis (44.2%) and S. saprophyticus (21.5%) were the most frequent species. Analysis of patients confirmed both species as urinary pathogens. Using an abbreviated scheme of 6 characteristics, S. saprophyticus was mis-classified in 19.5% of cases. A Phosphatase-Novobiocin-Mannose-Inhibition Test (PNMI-Test) together with a high NaCl concentration (10%) in combination with a coagulase test seems to be an acceptable compromise for routine identification of the three most important staphylococcal urinary tract pathogens, S. aureus, S. epidermidis, and S. saprophyticus. The technical and financial expenditure can be reduced considerably, because an extended identification has to be applied only to strains which cannot be identified by the PNMI-Test.

Recognition of Staphylococcus saprophyticus in urine cultures by screening colonies for production of phosphatase

Phenolphthalein diphosphate was incorporated into a primary blood agar medium for use in performing quantitative urine cultures. Phosphatase-negative staphylococci, such as Staphylococcus saprophyticus, were differentiated from phosphatase-positive species, such as Staphylococcus epidermidis, by spot testing colonies on filter paper saturated with 1 N NaOH. Phosphatase-positive colonies turned pink within seconds, and phosphatase-negative colonies showed no color. None of 55 S. saprophyticus isolates showed production of phosphatase on this medium. Of 193 consecutive coagulase-negative staphylococci isolated from the urine of 190 adolescent female patients, 84% were phosphatase positive, non-S. saprophyticus species; 16% were phosphatase-negative and indicated S. saprophyticus (22), Staphylococcus haemolyticus (4), Staphylococcus simulans (2), Staphylococcus warneri (1), and Staphylococcus hominis (1). Phosphatase activity was variable in the other flora encountered in the urine cultures. Mixtures of phosphatase-positive and -negative organisms did not cause false-positive reactions.