Novobiocin resistance and virulence of strains of Staphylococcus saprophyticus isolated from urine and skin.

A method was developed to study virulence of coagulase-negative staphylococci. Our results showed that coagulase-negative staphylococci injected into adult mice by the intracerebral route did not give rise to lethal infections, whereas mice aged 2 days were much more susceptible. Novobiocin-resistant strains of Staphylococcus saprophyticus were more virulent than strains of Staphylococcus epidermidis. Strains of S. saprophyticus biotype 3 of Baird-Parker's classification varied in virulence according to novobiocin sensitivity. In the classification of Kloos and Schleifer, S. saprophyticus biotype 3 can be subdivided into four distinct staphylococcal species, namely S. saprophyticus , S.cohnii, S.haemolyticus and S.warneri. S. chonii and S. saprophyticus were equally virulent for mice aged 2 days, but novobiocinsensitive S. haemolyticus was less virulent. On epidemiological grounds, however, it would seem that S. saprophyticus has some undefined advantage in invading the urinary tract.