Stenotrophomonas maltophilia strains isolated from a university hospital in Japan: genomic variability and antibiotic resistance

The diversity within the genetic and antibiotic resistance profiles and the production of virulence-associated enzymic activities of 66 Stenotrophomonas maltophilia strains collected from a university hospital in Japan in 2005 were studied. PFGE analysis of the collection indicated that a variety of profiles were present. MLST analysis of nine selected strains showed that four of the six sequence types identified were novel. These results indicated that there was a high degree of genetic diversity between the strains and that S. maltophilia strains isolated in Japan might be genetically divergent from those in Europe. The majority of strains were resistant to piperacillin (93.9 %), ceftazidime (84.8 %), imipenem (100 %), aztreonam (98.5 %), gentamicin (81.8 %), amikacin (87.9 %), ciprofloxacin (84.8 %), tetracycline (97.0 %) and chloramphenicol (78.8 %), although levofloxacin was effective against 77.3 % of the strains. Most of the strains showed multidrug resistance and carried the class 1 integron, but no strain showed transmission of antibiotic resistance by conjugation. Although haemolytic activity was not detected in any of the strains, protease and lipase activities were detected in 86.4 % and 31.8 % of the strains, respectively.