Distribution and characterization of Stenotrophomonas maltophilia isolates from environmental and clinical samples in Thailand.

BACKGROUND: Stenotrophomonas maltophilia has emerged as an important opportunistic pathogen, especially in patients who are immunocompromised, suffering from malignancy or have been hospitalized for a prolonged period. Information of this bacterium in Thailand has not been elucidated.

AIMS: To investigate the phenotype and genotype of environmental and clinical isolates of S. maltophilia in Songklanagarind Hospital, southern Thailand.

METHODS: Isolates of S. maltophilia were collected from various environmental sources on three hospital wards and clinical samples from seven wards. Antibiotic susceptibility and minimum inhibitory concentration (MIC) testing were performed using disk diffusion and E-test, respectively. Isolates were genotyped by pulsed-field gel electrophoresis.

FINDINGS: The majority of S. maltophilia environmental isolates were from sink drains (67.5%), followed by drinking water (18.7%) and tap water (7.5%). Clinical isolates of the bacterium mainly originated from sputum samples (56.2% of all isolates). Antibiotic resistance was more common in clinical isolates than in environmental isolates; resistance to co-trimoxazole was associated with the presence of the sul1 gene. The MIC values for ciprofloxacin and co-trimoxazole correlated closely with the results obtained from disk diffusion assay. DNA profile analysis revealed seven clusters with high diversity among the isolates.

CONCLUSION: No genotypic relationship was detected between isolates from environmental and clinical samples. As such, acquisition of this bacterium may occur outside the hospital.