Positive surveillance blood culture is a predictive factor for secondary metastatic infection in patients with Staphylococcus aureus bacteraemia

Abstract

Purpose: Staphylococcus aureus bacteraemia (SAB) may be complicated by secondary metastatic infection such as endocarditis, osteomyelitis or septic arthritis. This cohort study aimed to assess the prognostic value of sustained bacteraemia for outcomes related to Staphylococcus aureus bacteraemia.

Subjects and methods: The study took place in three tertiary-care, university-affiliated hospitals. Patients were prospectively included if they agreed to participate and if the following data were available: (a). surveillance blood culture taken between 24 and 48 h after commencement of effective antibiotic therapy; (b). appropriate investigations (at least a TTE) performed as suggested by the infectious diseases consult service. Patients with sustained bacteraemia defined as persistent positive blood cultures more than 24 h after commencement of effective antibiotic therapy were compared to patients for whom the surveillance blood culture was negative.

Results: One hundred and four patients were enrolled, including 51 patients diagnosed with sustained bacteraemia. Sustained bacteraemia was significantly associated with a higher frequency of secondary metastatic infection (p<0.001) and with a higher frequency of CRP>100 mg/l. Frequency of acute complications due to infection, septic shock and death due to bacteraemia was higher for patients with sustained bacteraemia but this difference was not statistically significant. Using a Cox model, the risk for death associated with sustained SAB, controlling for Index of comorbidity and age (categorised as<or>or=70 years), was 1.2 (95% CI: (0.5, 3); p>0.05).

Conclusion: In conclusion, surveillance blood cultures, especially performed on effective antibiotic therapy, may be a simple and cost-effective way to select a population at risk for secondary metastatic infection from SAB.