Staphylococcus aureus bacteraemia at two academic hospitals in Johannesburg

Staphylococcus aureus bacteraemia (SAB) remains a major problem worldwide. A retrospective study of patients with SAB seen from November 1999 to October 2002 was conducted at two academic hospitals in Johannesburg to determine mortality rates (death within 14 days of submission of blood culture) in patients bacteraemic with methicillin-sensitive (MSSA) and resistant S. aureus (MRSA) and to identify risk factors associated with mortality.

Of 449 patients with SAB, 104 (23.2%) died within 14 days of clinically suspected SAB. Of the 204 patients who acquired SAB in hospital, 6 patients died within 2 days, 39 between 2 and 14 days, and 41 more than 14 days after onset of SAB. One hundred and five patients (23.4%) had MRSA bacteraemia, 21 (20%) originating from the community. The MRSA bacteraemia rate among patients with hospital-acquired infection was 41.1%, significantly higher (p < 0.0001) than the 10.3% community-acquired MRSA bacteraemia. Thirty-five (33.3%) of the 105 patients with MRSA bacteraemia died within 14 days, compared with 69 (20.1%) of 344 MSSA patients (p = 0.0048). Admission to the intensive care unit (ICU) was significantly associated with mortality (p < 0.001)--30 of 79 patients admitted to ICU died (38%). Among 222 patients whose HIV status was known, 117 (52.7%) were positive, and of these 32 died (27.4%), a rate not significantly higher than that among HIV-seronegative patients (18 of 105 patients, p = 0.69).

Compared with MSSA, MRSA was shown to be significantly associated with mortality. Stay in ICU and infection with strains resistant to oxacillin, ofloxacin and rifampicin were highly significant predictors for mortality.