High prevalence of methicillin resistant Staphylococcus aureus in the surgical units of Mulago hospital in Kampala, Uganda

Abstract

Background: There is limited data on Methicillin resistant Staphylococcus aureus (MRSA) in Uganda where, as in most low income countries, the routine use of chromogenic agar for MRSA detection is not affordable. We aimed to determine MRSA prevalence among patients, healthcare workers (HCW) and the environment in the burns units at Mulago hospital, and compare the performance of CHROMagar with oxacillin for detection of MRSA.

Results: One hundred samples (from 25 patients; 36 HCW; and 39 from the environment, one sample per person/item) were cultured for the isolation of Staphylococcus aureus. Forty one S. aureus isolates were recovered from 13 patients, 13 HCW and 15 from the environment, all of which were oxacillin resistant and mecA/femA/nuc-positive. MRSA prevalence was 46% (41/89) among patients, HCW and the environment, and 100% (41/41) among the isolates. For CHROMagar, MRSA prevalence was 29% (26/89) among patients, HCW and the environment, and 63% (26/41) among the isolates. There was high prevalence of multidrug resistant isolates, which concomitantly possessed virulence and antimicrobial resistance determinants, notably biofilms, hemolysins, toxin and ica genes. One isolate positive for all determinants possessed the bhp homologue which encodes the biofilm associated protein (BAP), a rare finding in human isolates. SCCmec type I was the most common at 54% prevalence (22/41), followed by SCCmec type V (15%, 6/41) and SCCmec type IV (7%, 3/41). SCCmec types II and III were not detected and 10 isolates (24%) were non-typeable.

Conclusions: Hyper-virulent methicillin resistant Staphylococcus aureus is prevalent in the burns unit of Mulago hospital.

Figure 1

Representative images showing detection of virulence and antimicrobial resistance genes/determinants in MRSA isolates. Lanes: L, 100 bp DNA ladder; N, negative control (for all images). Panel A: 1 & 2, species confirmation of S. aureus by detection of the nuc gene; 3 & 4, ica; 5, bhp; 6 & 7, PVL. Panel B: 1 & 2, nuc; 3 & 4, tst1; 5 & 6, hla; 7 & 8, sdrE; 8, sea. Panel C: Detection of genes encoding aminoglycoside modifying enzymes (AMEs). 1 & 2, (aac(6')-Ie-aph(2'')-Ia); 3 & 4, (aph(3')-IIIa); 5 & 6, (ant(4')-Ia). Panel B. Graphical presentation of prevalence for selected determinants.