Mortality of S. aureus bacteremia and infectious diseases specialist consultation – A study of 521 patients in Germany

Summary

Objectives

To evaluate the relationship between mortality of bloodstream infection due to Staphylococcus aureus and infectious diseases specialist consultation and other factors potentially associated with outcomes.

Methods

A 6-year cohort study was conducted at a 1600-bed university hospital. Consecutive adult patients with S. aureus bacteremia were assessed using a standardised data collection and review form. A new infectious diseases service increased its consultations for S. aureus bacteremia from 33% of cases in 2002 to >80% in 2007. Infectious disease consultation and other factors potentially associated with in-hospital mortality were analysed by multivariate logistic regression.

Results

A total of 521 patients were studied. All-cause in-hospital mortality was 22%, 90-day mortality was 32%. Factors significantly associated with in-hospital mortality in multivariate analysis were ICU admission (OR 5.8, CI 3.5–9.7), MRSA (OR 2.6, CI 1.4–4.9), age ≥60 years (OR 2.4, CI 1.4–4.2), a diagnosis of endocarditis (OR 2.8, CI 1.4–5.7), a non-fatal underlying disease/comorbidity according to the McCabe classification (OR 0.2, CI 0.1–0.4), and infectious disease specialist consultation (OR 0.6, CI 0.4–1.0).

Conclusions

These data suggest that outcome of S. aureus bacteremia may be improved by an expert consultation service.

Introduction

Staphylococcus aureus is a major pathogen causing both community- and hospital-acquired bloodstream infection with substantial morbidity and mortality.²⁴ The incidence of S. aureus bacteremia has been estimated to be 20–35 cases annually per 100,000 population. Recent studies from different parts of the world indicate increasing incidence rates, particularly due to the emergence of methicillin-resistant S. aureus (MRSA) bacteremia in hospitals and the community.4, 22, 32

S. aureus bacteremia (SAB) carries a high risk of complications such as metastatic disease with deep-seated foci of infection, endocarditis, severe sepsis or recurrences.9, 10, 18 The reported in-hospital mortality has remained surprisingly high over the last decades, ranging between 20% and >30% in the more recent studies.1, 8, 28, 32 Several factors have been reported to be associated with a poor outcome of SAB. Among these are community acquisition, unknown portal of entry, inadequate treatment, MRSA, persistent bacteremia and failure to remove intravascular devices.3, 6, 14, 19, 20, 21

Infectious disease (ID) specialist consultation has been investigated as a strategy to improve the quality of care for SAB patients. Better adherence to diagnostic guidelines and management/treatment standards such as removal of catheters or use of echocardiography after ID consultation has been shown in a few studies.11, 17 Nevertheless, whether survival of patients with SAB can be improved by ID consultation has remained unclear.

In 2002, a new ID service was established in our hospital. Initially, ID specialist consultations for SAB were performed on request of the primary physician only. In 2005, we started the policy to offer routine ID specialist consultations for all patients with SAB, and increased the proportion of cases with SAB seen by an ID expert. In the present paper we evaluated the epidemiology, clinical characteristics and outcomes of SAB admitted to our institution between 2002 and 2007 with a focus on the impact of ID specialist consultation on mortality of this highly prevalent and severe cross-specialty infection.