Background: Stenotrophomonas maltophilia
is a non-fermentative gram-negative
which is widely recognised as an important nosocomial pathogen causing pneumonia,
blood-stream, wound and urinary tract infections, particularly in immunosuppressed patients. The
aim of this study was to evaluate a nosocomial outbreak of by S. maltophilia
in an intensive care
unit of a tertiary hospital and evaluate unexpected multiclonality.
A total of 11 isolates from respiratory cultures in intensive care unit of a 24 bed
tertiary hospital obtained over a one months period and one isolate obtained from the nebuliser
during environmental screening were investigated. The bacteria were identified by Phoenix 100
system. The clonal relatedness was evaluated by PFGE and semi-automated repetitive sequence-based
PCR. Genotyping tests were repeated for 10 serial subcultures.
PFGE and DiversiLab yielded 10 genotypic profiles for 12 isolates. Four to eight
different genotypes were observed from 10 subcultures of the same isolate.
We conclude that, high genetic diversity and supposed multiclonal
appearance of the outbreak isolates may be due to changing profiles during subcultures most
probably depending on hypermutation.