The Journal of Medical Microbiology, Vol 30, Issue 4 253-266, Copyright © 1989 by Society for General Microbiology
Is resistance to novobiocin a reliable test for confirmation of the identification of Staphylococcus saprophyticus?
L. A. McTaggart and T. S. Elliott
Department of Clinical Microbiology, Queen Elizabeth Hospital, Edgbaston, Birmingham.
Staphylococcus saprophyticus, a coagulase-negative staphylococcus (CNS),
causes acute urinary tract infection predominantly in young women (15-30
years). In the clinical microbiology laboratory identification and
differentiation of S. saprophyticus from other CNS usually depends solely
upon the demonstration of resistance to the antimicrobial agent novobiocin.
Phenotypic characteristics of 36 novobiocin-resistant CNS isolated from the
urine of patients with acute urinary tract infections were further analysed
and the homogeneity of the isolates assessed. The organisms were speciated
by the API STAPH identification system. Twenty-one isolates were S.
saprophyticus (p greater than or equal to 97%), and there was one strain
each of S. epidermidis, S. hominis and S. simulans (p greater than or equal
to 97%). Of the remainder, three isolates were unidentifiable and a further
nine had the characteristics associated with more than one species of CNS.
Additional tests, including carbohydrate fermentation, antibiotic
sensitivity and fluorogenic substrate utilisation, were performed on all
isolates. Computer analysis of the results confirmed that testing for
resistance to novobiocin selects a heterogeneous group of CNS composed of
several different species.
