Risk factors for emergence of Stenotrophomonas maltophilia in cystic fibrosis

The number of patients with cystic fibrosis (CF) whose sputum culture has y ielded Stenotrophomonas maltophilia has increased in the last 5 years at St . Christopher's Hospital for Children. We conducted a case-control study to determine risk factors for recovery of S. maltophilia in respiratory secre tions from patients with CF. We reviewed the outpatient and inpatient recor ds of patients colonized with S. maltophilia between 1993 and 1997, and of age-matched (at time of initial recovery of S. maltophilia) control patient s with CF who had never had a positive sputum culture for S. maltophilia. V ariables included age at time of CF diagnosis, gender, severity of CF (base d on Shwachman-Kulczycki (S-K) scores and spirometry), frequency of hospita lizations, use of oral, intravenous, or inhaled antibiotics, and use of ora l or inhaled corticosteroids in the 2 years prior to the first isolation of S. maltophilia from respiratory secretions, Statistical methods included s tepwise logistic regression to determine risk factors for acquisition of S. maltophilia. During the study period, 58 patients with CF had a positive sputum or deep throat culture for S. maltophilia. The distribution of S. maltophilia acqui sition by year increased from 7 patients in 1993 (incidence, 2.8%) to 18 in 1997 (incidence, 6.2%). Patients positive for S. maltophilia were found to have significantly worse growth parameters, S-K score, and spirometric val ues than S. maltophilia-negative CF controls (P < 0.05). Stepwise logistic regression demonstrated that treatment with long-term antibiotics (P = 0.00 16) and number of days of intravenous antibiotic therapy (P = 0.035) were s ignificant risk factors for S. maltophilia colonization in our group of CF patients. We conclude that patients with CF whose respiratory secretions yield S. mal tophilia have an overall worse clinical status at the time of initial S. ma ltophilia isolation than noncolonized patients, and that preceding treatmen t with antibiotics may have predisposed them to the acquisition of this bac terium in their respiratory secretions. (C) 2000 Wiley-Liss, Inc.