Occurrence of Stenotrophomonas spp. in the Water Environment and Characteristics of Isolates

Abstract

Stenotrophomonas maltophilia has been increasingly recognized as an opportunistic pathogen that causes pneumonia and bloodstream infections. In spite of its clinical importance, literatures on the quantitative monitoring of Stenotrophomonas in the water environment are not available. In this study, Stenotrophomonas spp. contained in treated wastewater, pond water and river water were quantified by a selective agar medium. The numbers of blue colonies on VIA agar plates were in ranges of 1.9 to 24.7 CFU/mL for treated wastewater and 0.6 to 15.8 CFU/mL for other environmental samples. The species of 88 isolates with blue colonies on the VIA agar plates consisted of Stenotrophomonas spp. (85%) and others (15%) based on 16S rRNA sequencing and genus-specific PCR targeting 23S rRNA. The number of Stenotrophomonas spp. in the samples was roughly 1/50 level of the number of coliform group bacteria. Most Stenotrophomonas isolates (> 97%) were susceptible to both sulfamethoxazole/trimethoprim and levofloxacin.