Prevalence of Virulence Determinants in Staphylococcus Epidermidis from ICU Patients in Kampala; Uganda

ABSTRACT

Introduction: Staphylococcus epidermidis is often considered a non-pathogenic organism but it causes nosocomial infections. To distinguish invasive strains; comparative studies of patient and community isolates may offer some clues. We investigated the distribution of virulence determinants in patient isolates from Uganda. Methodology: S. epidermidis isolates were identified with the Staph API ID 32 kit. Antimicrobial susceptibility; biofilm formation and hemolysis were detected with standard procedures. Genes associated with virulence (aap; atlE; bhp; hla; hld; ica; IS256; sdrE; sea; tsst) and antimicrobial resistance (aac(6')-Ie-aph(2'')-Ia; aph(3')-IIIa; ant(4')-Ia; blaZ; mecA; vanA/vanB1) were detected by PCR. Results: S. epidermidis grew in 30 (30/50; 60) ICU samples and 20 (20/60; 33) community samples (one isolate per sample per patient/person). All ICU isolates (30/30; 100) were IS256 and hld positive; 22 (22/30; 73) were biofilm/ica positive; 21 (21/30; 70) were hemolytic on blood agar; nine (9/30; 30) contained atlE gene; six (6/30; 20) hla gene; five (5/30; 17) aap gene; and three (3/30; 10) bhp gene. A gene encoding an aminoglycoside-modifying enzyme; aph(3')-IIIa; was highly prevalent (28/30; 93); while blaZ (2/30; 7); mecA (3/30; 10); vanA (3/30; 10) and vanB1 (3/30; 10) were less prevalent. Of the community isolates; one (1/20; 5) was ica positive; two (2/20; 10) formed biofilms; and three (3/20; 15) possessed the atlE gene. bhp; aap; IS256; hld and antimicrobial resistance genes were not detected in community isolates. Conclusions: S. epidermidis from ICU patients in Mulago Hospital is potentially virulent and could be a reservoir for antimicrobial resistant genes