Major article
Risk factors and mortality in patients with nosocomial Staphylococcus aureus bacteremia

https://doi.org/10.1016/j.ajic.2007.02.005Get rights and content

Background

Infections due to methicillin-resistant Staphylococcus aureus have become increasingly common in hospitals worldwide. S aureus continues to be a cause of nosocomial bacteremia.

Methods

We analyzed the clinical significance (mortality) of MRSA and methicillin-susceptible S aureus bacteremia in a retrospective cohort study in a 2900-bed tertiary referral medical center. Survival and logistic regression analyses were used to determine the risk factors and prognostic factors of mortality.

Results

During the 15-year period, 1148 patients were diagnosed with nosocomial S aureus bacteremia. After controlling potential risk factors for MRSA bacteremia on logistic regression analysis, service, admission days prior to bacteremia, age, mechanical ventilator, and central venous catheter (CVC) were independent risk factors for MRSA. The crude mortality rate of S aureus bacteremia was 44.1%. The difference between the mortality rates of MRSA (49.8%) and MSSA bacteremia (27.6%) was 22.2% (P < .001). Upon logistic regression analysis, the mortality with MRSA bacteremia was revealed to be 1.78 times higher than MSSA (P < .001). The other predicted prognostic factors included age, neoplasms, duration of hospital stay after bacteremia, presence of mechanical ventilator, and use of CVC.

Conclusions

Resistance to methicillin was an important independent prognostic factor for patients with S aureus bacteremia.

Section snippets

Hospital and patients

From 1990 to 2004, a retrospective cohort study was performed to determine and compare mortality of nosocomial MRSA and MSSA bacteremia. The study took place in a 2900-bed tertiary referral medical center. Each episode of nosocomial infection was defined as one that had at least one S aureus–positive blood culture at least 48 hours after admission according to standard definitions proposed by the Centers for Disease Control and Prevention. Only the first S aureus bacteremia was recorded for

Results

During the 15-year study period, a total of 1148 patients were diagnosed with nosocomial S aureus bacteremia. Of these, 506 patients died during the course of treatment, representing a crude mortality rate of 44.1%. Of the diagnosed patients, 851 (74.1%) presented with MRSA bacteremia with a crude mortality rate of 49.8% (424/851), and 297 patients (25.9%) presented with MSSA bacteremia with a crude mortality rate of 27.6% (82/297). The rate difference of mortality was 22.2% with statistical

Discussion

Methicillin resistance in Staphylococcus was first reported in 1961. Since then, methicillin-resistant Staphylococcus had become a significant problem in medical facilities worldwide, with MRSA now accounting for 40%-86% of nosocomial S aureus bacteremia.5, 9, 10, 11 Confirming this clinical significance, the present 15-year study involving 1148 patients documented that MRSA accounted for 74.1% of all nosocomial S aureus bacteremia in a large tertiary care hospital.

Risk factors for acquiring

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None of the authors has any commercial or other association that might pose a conflict of interest.

This study was supported by a research grant from Taipei Veterans General Hospital, Taipei, Taiwan.

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