Epidemiological typing of Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is increasingly recognized as a cause of hospital-acquired infection and respiratory tract colonization in cystic fibrosis patients. A number of methods have been described for the typing of strains in epidemiological studies. Pulsed-field gel electrophoresis (PFGE) of total chromosomal DNA cleaved by low-frequency restriction site endonucleases (XbaI, SpeI) is highly discriminatory and defines populations at the strain level. Other molecular methods such as ribotyping with restriction endonucleases (BamHI, ClaI, BelI, EcoRI) can be used to subdivide the species but with reduced discrimination compared with PFGE. Polymerase chain reaction (PCR) fingerprinting techniques utilizing random primers or those directed against repeat motifs (ERIC, REP) are rapid and offer high discrimination for the study of outbreaks. A consistent finding from a number of incidents is the high diversity of strain types of S. maltophilia identified and the low incidence of cross-infection between patients.