Long-term outcome of invasive Staphylococcus aureus infections

Abstract

Background: Short-term mortality from invasive Staphylococcus aureus infections (ISA) is high. Death rates from 20% to 60% are reported. Long-term outcome has not been investigated. Studies of other critical illnesses have demonstrated incremental health effects that persist after hospital discharge. Several researchers have proposed that evaluation of mortality secondary to sepsis should take place after 1 y. Methods: We performed an observational, prospective, population-based study of long-term mortality and recurrence in a cohort of ISA patients during 2 y. Results: One hundred and fifty-seven patients were included. All-cause mortality after 1 y was 37.6% and after 3 y was 45.5%. The multivariate survival analysis explored different independent factors for short-term compared to long-term mortality. Age, comorbidity, and place of acquisition were the determinants of long-term outcome. In contrast, infection-related factors such as disease severity and systolic blood pressure determined short-term mortality. The relapse–reinfection rate was 11.2% (16 in 143 episodes in 127 patients living 4 weeks after inclusion). Predictive factors for relapse–reinfection in a univariate analysis were joint prosthesis (28.6%, p = 0.027), haemodialysis (27.8%, p = 0.017), kidney disease (22.2%, p = 0.015), and healthcare- and nosocomial-related infection (18.3%, p = 0.029). No association to length of antibiotic therapy and relapse–reinfection rate was observed, nor any sex differences. The majority of relapses–reinfections (11 of 16) occurred during the first 11 months after the initial episode. Conclusion: Patients with ISA infections, irrespective of age, suffer a high long-term mortality and recurrence rate.

Keywords::

• Long-term outcome
• Staphylococcus aureus
• invasive infections
• mortality
• recurrence

Declaration of interest: The study was supported by a grant from the Research Fund at Skaraborg Hospital. No conflict of interest.

Appendix

Criteria for hypotension, hypoperfusion, or organ dysfunction for the diagnosis of severe sepsis based on the 2001 SCCM/ESICM/ACCP/ATS/SIS International Sepsis Definitions Conference.

A. Hypotension

Systolic blood pressure ≤ 90 mmHg or mean arterial pressure (MAP) ≤ 70 mmHg.

B. Hypoperfusion

Plasma lactate > 3 mmol or > 1 mmol above the upper normal range.

C. Organ dysfunction

• Respiratory: PaO₂ ≤ 7.0 or PaO₂/FiO₂ ≤ 33, if no diagnosis of pneumonia, or PaO₂ ≤ 5.7 or PaO₂/FiO ≤ 27, if diagnosis of pneumonia.

• Central nervous system: acute change of mental status.

• Renal: oliguria < 0.5 ml/kg/h for at least 2 h, or increase of plasma creatinine ≥ 45 mmol.

• Haematological: platelets < 100 × 10⁹, or international normalized ratio (INR) ≥ 1.5, or activated partial thromboplastin time (APTT) ≥ 60 s.

• Hepatic: plasma bilirubin ≥ 45 μmol.