Characterization of coagulase-negative staphylococci from urinary tract specimens

Abstract

Species of coagulase-negative staphylococci isolated from urine specimens submitted from inpatients and outpatients to the clinical microbiology laboratory of a teaching hospital were identified with a biotyping system; species were correlated by clinical features and antimicrobial susceptibility. Of 145 isolates, 102 (70%) were S. epidermidis, 24 (17%) were S. saprophyticus, 7 (4.7%) were S. haemolyticus, 4 (2.8%) were S. hominis, 3 (2.1%) were S. simulans and 5 (3.4%) were other species. Features peculiar to persons with S. saprophyticus bacteriuria as compared to those with bacteriuria caused by other staphylococcal species included female sex (95% vs. 52%), young age (median age 22 yr vs. 61 yr), ambulatory status (hospital outpatients, 86% vs. 23%), and absence of indwelling catheters (4.5% vs. 49%). All other coagulase-negative staphylococci were isolated in a setting suggesting nosocomial acquisition, more frequently resistant to common antimicrobial agents (42% multiply resistant vs. 4.2% of S. saprophyticus) and were not distinguished by clinical features. Novobiocin susceptibility, with a sensitivity of 100% and specificity of 96%, provided a simple and reliable test for differentiation of S. saprophyticus from other coagulase-negative staphylococci and should be routinely used for urinary tract specimens in the clinical laboratory.