ABSTRACT
Objective: To determine the incidence of Coagulase - negative S. aureus in 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. aureus was 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