Search of streptomycin-resistant bacteria in creek water and application of MALDI-TOF MS to grouping of the isolated bacteria

Abstract

A search of streptomycin-resistant bacteria was carried out using ten creek water samples collected in Saga prefecture by spreading the sample water on an R2A medium containing 10 μg/ml of streptomycin. It was clarified that such streptomycin-resistant bacteria as Bacillus, Novosphigobium, Sphingopyxis and Oceanobacillus were distributed in the creek water. Further, 60% of the isolates didn' t form an inhibitory zone by the application of 700 μg/ml streptomycin solution in the cup method assay. Further, the effectiveness of the MALDI-TOF MS analysis for the grouping of the isolates was examined. The discriminating ability of MALDI-TOF MS analysis was higher than that of RFLP analysis and it was almost equal to that of sequence analysis using 16S rDNA. Considering the high-throughput ability of the MALDI-TOF MS instrument, MALDI-TOF mass spectral identification of bacteria will be a powerful method in the construction of a MALDI-TOF mass spectra database.