Survival of Stenotrophomonas maltophilia following exposure to concentrations of tobramycin used in aerosolized therapy for cystic fibrosis patients.

The use of aerosolized tobramycin is an important component in the management of patients with cystic fibrosis, particularly those with chronic Pseudomonas aeruginosa infection. Clinicians have been concerned that long-term therapy with aerosolized tobramycin may increase the risk of colonization with multi-resistant bacteria, including Stenotrophomonas maltophilia. The ability of five strains (three clinical, two environmental) of S. maltophilia to survive exposure to 16000 microg/mL tobramycin, a concentration commonly found inside the atomization chamber of nebulizers used to deliver aerosolized therapy, was studied. Under a variety of different growth conditions, all five strains were able to survive exposure to 16000 microg/mL of tobramycin. Post-exposure recovery was enhanced at 20 degrees C and 30 degrees C in comparison with 37 degrees C under all test conditions. The importance of these findings in relation to the epidemiology of S. maltophilia in patients with cystic fibrosis is discussed.