Species Identification and Antibiotic Susceptibilities of Coagulase- Negative Staphylococci Isolated from Urinary Tract Infection Specimens.

OBJECTIVE To determine the incidence of Coagulase- negative S. aureusin urinary tract infections and sensitivities of these isolates to antimicrobial agents. STUDY DESIGN Cohort study. PLACE AND DURATION OF STUDY Dr. Essa Laboratory and Immunology and Infectious Disease Research Laboratory (IIDRL), Microbiology Department, University of Karachi, from January 2009 to January 2010. METHODOLOGY Urine specimens, suggestive of urinary tract infection (UTI), were identified. Speciation of isolates was done using API-20 Staph.system. Screening of extracellular products was done using SDS-PAGE electrophoresis and Hemolysin on blood-agar plates. Minimum inhibitory concentration (MICs) of antibiotics was estimated by microtiter well plate method. Frequency and percentages were determined and chi-square test was used for comparing proportions with significance at p < 0.05. RESULTS Coagulase - negative S. aureus(CONS) were the cause of urinary tract infection in 56 out of 1866 outpatient (3%) and 164 of 1261 inpatient (13%), urinary tract infections (p < 0.001). Two hundred and twenty CONS isolates were identified. The most common CONS identified was S. saprophyticus (31%, 68 strains). The relative frequency of Coagulase - negative S. aureuswas 6% (13 strains). All isolates were sensitive to Vancomycin and Linezolid. Resistance was 69% to Ampicillin, 53% to Methicillin, and 37.5% to Ciprofloxacin. CONCLUSION CONS are a potential uropathogens, with capability of slime production and resistance to common empirical prescriptions. This also warrants formulation of an appropriate antibiotic policy that covers CONS.