Stenotrophomonas maltophilia infection and colonization in the intensive care units of two community hospitals:: A study of 143 patients

STUDY OBJECTIVE: To study the epidemiology of Stenotrophomonas maltophilia infections in the intensive care units (ICUs) of community general hospitals. DESIGN: Retrospective chart review of 143 patients with cultures positive for S.maltophilia over a 2-year period. SETTING: Intensive care units of 2 community general hospitals. RESULTS: Patients with S. maltophilia infection or colonization were elderly (mean age 62.4 years), intubated for a mean of 11.8 days, and had a mean Acute Physiology and Chronic Health Evaluation TI (APACHE II) score of 16.6. A tracheostomy was present in 22.4%, and underlying chronic respiratory disease and malignancy were found in 25.9% and 15.4%, respectively. Only 2 patients (1.4%) were neutropenic. Most isolates (89.5%) were from the respiratory tract and were part of a polymicrobial culture in 52.5% of patients. Only a slightly higher APACHE II score (mean = 18.0, SD 7.8 vs mean = 15.6, SD 6.2, P = 0.052) differentiated patients with infection from those with colonization. All but 2 patients were exposed to antibiotics before their positive culture. Crude mortality rate was 41.3% overall and was significantly higher in those with an APACHE II score of 15 or more (48.8% vs 30.5%, P = 0.028). CONCLUSION: S. maltophilia is emerging as an important cause of nosocomial infection, especially pneumonia, in ICUs of community general hospitals. Patients tend to be elderly, intubated for a mean of about 12 days, have high APACHE II scores, and frequently have a tracheostomy or underlying chronic respiratory disease. In contrast to earlier reports, neutropenia and underlying malignancy are uncommon in our ICU population. We found prior antibiotic exposure was almost universal and similar to previous reports, but use of imipenem was much less common in our community hospital patients. Patients with a high APACHE II score should be considered infected rather than colonized, but differentiation of infection from colonization remains problematic. Isolation of S. maltophilia from a patient carries a crude mortality rate of 41.3%, and patients with an APACHE II score of 15 or more have a significantly higher mortality rate than those with lesser scores, approaching 50%. Trimethoprim-sulfamethoxazole (TMP-SMX) remains the drug of choice for infections caused by S. maltophilia.