Outcome and attributable mortality in critically Ill patients with bacteremia involving methicillin-susceptible and methicillin-resistant Staphylococcus aureus

Arch Intern Med. 2002 Oct 28;162(19):2229-35. doi: 10.1001/archinte.162.19.2229.

Abstract

Background: Staphylococcus aureus bacteremia carries high mortality rates. The clinical impact of methicillin resistance remains controversial: outcome comparisons between patients with bacteremia involving methicillin-susceptible (MSSA) and methicillin-resistant (MRSA) S aureus are difficult to perform because of important differences in severity of illness.

Methods: A retrospective cohort analysis and 2 independent case-control analyses were performed to determine and compare outcomes and attributable mortality rates of MSSA (n = 38) and MRSA bacteremia (n = 47) in critically ill patients. For the case-control studies, matching (1:2 ratio) was based on the APACHE (Acute Physiology and Chronic Health Evaluation) II classification: APACHE II score (+/-1 point) and diagnostic category.

Results: Patients with MRSA bacteremia had more acute renal failure and hemodynamic instability than patients with MSSA bacteremia. They had a longer intensive care unit stay and ventilator dependency. Patients with MRSA bacteremia had a higher 30-day mortality rate (53.2% vs 18.4%) and in-hospital mortality rate (63.8% vs 23.7%) (P<.05). Multivariate survival analysis demonstrated acute renal failure, length of mechanical ventilation, age, and methicillin resistance to be independently associated with mortality (P<.05). The attributable mortality rate for MSSA bacteremia was 1.3%: mortality rates for cases and controls were respectively 23.7% and 22.4% (P =.94). The attributable mortality rate for MRSA bacteremia was 23.4%: mortality rates for cases and controls were respectively 63.8% and 40.4% (P =.02). The difference (22.1%) between both attributable mortality rates was significant (95% confidence interval, 8.8%-35.3%).

Conclusion: In critically ill patients, after accurate adjustment for disease severity and acute illness, we found MRSA bacteremia to have a higher attributable mortality than MSSA bacteremia.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acute Kidney Injury / complications
  • Aged
  • Bacteremia / complications
  • Bacteremia / microbiology*
  • Bacteremia / mortality
  • Case-Control Studies
  • Cohort Studies
  • Cross Infection / complications
  • Cross Infection / microbiology*
  • Cross Infection / mortality
  • Humans
  • Length of Stay
  • Methicillin Resistance*
  • Middle Aged
  • Multivariate Analysis
  • Retrospective Studies
  • Staphylococcal Infections / complications
  • Staphylococcal Infections / microbiology*
  • Staphylococcal Infections / mortality
  • Staphylococcus aureus / drug effects*
  • Survival Rate