Outbreak of nosocomial infection/colonisation caused by Stenotrophomonas maltophilia with mucoid phenotype

The Gram-negative bacillus Stenotrophomonas maltophilia (SM) has emerged as an important pathogen associated with significant case/fatality ratio [1,2] SM is a potentially dangerous organism because of its resistance to many antibiotics. We present here an outbreak of mucoid phenotype SM pneumonia (four cases) and respiratory tract colonisation (three cases). Our review of literature revealed only one case report of pneumonia characterised as mucoid phenotype [2]. The outbreak was caused following admission of a 65-year-old male patient with respiratory distress, fever, leukocytosis (24000/µl) in the ICU. Chest X-ray showed an infiltrative shadow in the right lower lobe and bilateral pleural effution was detected on CT. Sputum cultures obtained before admission to ICU and subsequent days yielded mucoid phenotype SM. Treatment with ticarcilline plus clavulonic acid to which the isolates was susceptible was initiated. One-day later chest X-ray showed diffuse bilateral pneumonic infiltrates and the patient's condition rapidly deteriorated. Ciprofloxacine was added to the treatment. Subsequent SM isolates rapidly developed antimicrobial resistance to antibiotics. Four patients in the ICU were lost with SM pneumonia within 7-10 days. SM isolates were identified by standard Analytical Profile Index procedure (API 20E and API 20 NE). A significant number of both infected and colonised patients had severe systemic diseases and tracheotomy, they were mechanically ventilated and receiving broad spectrum antibiotics before isolation of SM. SM is emerging as an important nosocomial pathogen in critically ill ICU patients and should no longer be regarded as a harmless bacillus in ICU.