Prevalence, Prediction, and Clonality of Methicillin-ResistantStaphylococcus aureusCarriage at Admission to Medical Units in Hong Kong, China

Abstract

Objective.To determine the prevalence, risk factors, and molecular epidemiology of methicillin-resistantStaphylococcus aureus(MRSA) colonization at the time of admission to acute medical units and to develop a cost-effective screening strategy.Methods.Nasal and groin screening cultures were performed for patients at admission to 15 acute medical units in all 7 catchment regions in Hong Kong. All MRSA isolates were subjected tospatyping.Results.The overall carriage rate of MRSA was 14.3% (95% confidence interval [CI], 13.5–15.1). MRSA history within the past 12 months (adjusted odds ratio [OR], 4.60 [95% CI, 3.28–6.44]), old age home residence (adjusted OR, 3.32 [95% CI, 2.78–3.98]), and bedbound state (adjusted OR, 2.19 [95% CI, 1.75–2.74]) were risk factors selected as MRSA screening criteria that provided reasonable sensitivity (67.4%) and specificity (81.8%), with an affordable burden (25.2%).spatyping showed that 89.5% (848/948) of the isolates were clustered into the 4spaclonal complexes (CCs):spaCC1081,spaCC032,spaCC002, andspaCC4677. Patients colonized with MRSAspatypes t1081 (OR, 1.77 [95% CI, 1.49–2.09]) and t4677 (OR, 3.09 [95% CI, 1.54–6.02]) were more likely to be old age home residents.Conclusions.MRSA carriage at admission to acute medical units was prevalent in Hong Kong. Our results suggest that targeted screening is a pragmatic approach to increase the detection of the MRSA reservoir. Molecular typing suggests that old age homes are epicenters in amplifying the MRSA burden in acute hospitals. Enhancement of infection control measures in old age homes is important for the control of MRSA in hospitals.