Stenotrophomonas maltophilia is a gram-negative bacterium. Hospitals can be a source of S. maltophilia because it adheres to nonliving surfaces and forms a biofilm. This study was performed to investigate the clonal relationship between S. maltophilia isolates obtained from kidney stone samples. Samples of kidney stones taken from patients and surrogate samples from nephroscopes, cleaning solution, disinfectant solution were included in the study. The clonal relationship between isolates was determined by PFGE. S. maltophilia was isolated from 34 of 94 kidney stone samples sent from the urology operating room between July 2017 and January 2018. A total of 26 S. maltophilia strains (21 from kidney stone samples, three from nephroscopes, and two from urine culture) were isolated. PFGE showed that the 21 kidney stone isolates and the 3 S. maltophilia isolates obtained from the nephroscope belonged to the same clone. The two urine culture isolates showed no clonal relationship to the outbreak isolates and were considered sporadic. Molecular typing confirmed that this pseudo-outbreak was attributed to inadequate disinfection of the nephroscopes. After disinfection protocols were reviewed and revised as needed, especially regarding the removal of organic material from nephroscopes after use, no further bacterial growth was detected from kidney stone specimens obtained with nephroscopes.
Stenotrophomonas maltophilia, pseudo-outbreak, inadequate sterilization, molecular typing, clonal relationship