Hospital-associated methicillin-resistant Staphylococcus aureus: A cross-sectional analysis of risk factors in South African tertiary public hospitals

Abstract

Introduction: Hospital-associated methicillin-resistant S. aureus (HA-MRSA) remains a significant cause of morbidity and mortality worldwide. We conducted a study to determine risk factors for HA-MRSA in order to inform control strategies in South Africa.

Methods: We used surveillance data collected from five tertiary hospitals in Gauteng and Western Cape provinces during 2014 for analysis. A case of HA-MRSA was defined as isolation of MRSA from a blood culture 48 hours after admission and/or if the patient was hospitalised in the six months prior to the current culture. Multivariable logistic regression modelling was used to determine risk factors for HA-MRSA.

Results: Of the 9971 patients with positive blood cultures, 7.7% (772) had S. aureus bacteraemia (SAB). The overall prevalence of MRSA among those with SAB was 30.9% (231/747; 95% confidence interval [CI] 27.6%- 34.3%). HA-MRSA infections accounted for 28.3% of patients with SAB (207/731; 95% CI 25.1%- 31.7%). Burns (adjusted odds ratio [aOR] 12.7; 95% CI 4.7-34.4), age ≤1 month (aOR 8.7; 95% CI 3.0-24.6), residency at a long-term care facility (aOR 5.2; 95% CI, 1.5-17.4), antibiotic use within two months of the current SAB episode (aOR 5.1; 95% CI 2.8-9.1), hospital stay of 13 days or more (aOR 2.8; 95% CI 1.3-5.6) and mechanical ventilation (aOR 2.2; 95% CI 1.07-4.6), were independent risk factors for HA-MRSA infection.

Conclusion: The prevalence of MRSA remains high in South African tertiary public hospitals. Several identified risk factors of HA-MRSA infections should be considered when instituting infection and prevention strategies in public-sector hospitals, including intensifying the implementation of antimicrobial stewardship programmes. There is an urgent need to strengthen infection prevention and control in burn wards, neonatal wards, and intensive care units which house mechanically ventilated patients.

Fig 1. The number of SAB cases at five hospitals in Gauteng and Western Cape during 2014.

AST, antimicrobial susceptibility testing results; SAB, S. aureus bacteraemia; CA, community-associated; HA, hospital-associated; MSSA, methicillin sensitive S. aureus; MRSA, methicillin-resistant S. aureus.