Abstract
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. 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. 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. S. epidermidis from ICU patients in Mulago Hospital is potentially virulent and could be a reservoir for antimicrobial resistant genes.
Highlights
Staphylococcus epidermidis is often considered a non-pathogenic organism but it causes nosocomial infections
We investigated the distribution of virulence determinants in patient isolates from Uganda
Okee et al - S. epidermidis virulence determinants intensive care units (ICU) are colonized/infected with nosocomial pathogens, those associated with the frequent use of support devices, we aimed to determine the prevalence of a collection of virulence and antimicrobial resistance determinants in S. epidermidis from ICU patients at Mulago Hospital in Kampala, Uganda
Summary
Staphylococcus epidermidis is often considered a non-pathogenic organism but it causes nosocomial infections. While there is limited data on the molecular epidemiology of S. epidermidis infections in subSaharan Africa, elsewhere many investigators elucidating the pathogenicity of the organism mainly focus on detection of biofilms and intercellular adhesion (ica) genes. The usefulness of these as virulence markers has been debated widely [6,7]. More genes implicated in biofilm production (i.e., bifunctional autolysin E, atlE; accumulation-associated protein, aap; and biofilm associated protein, bhp) have been elucidated [2,3,8] While they were demonstrated as useful in the detection of clinical strains [2], their prevalence has not been widely investigated.
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