Molecular investigation of Streptococcus agalactiae isolates from environmental samples and fish specimens during a massive fish kill in Kuwait Bay.

This study was undertaken to identify and characterize bacterial isolates obtained simultaneously from dead fish samples during a massive fish kill in Kuwait Bay and sewage-water samples running into Kuwait Bay using conventional and molecular techniques. Of the 71 bacterial isolates studied; 66 were recovered from 7 different fish species and 5 strains were isolated from sewage samples. The species-specific identity of the isolates was established by phenotypic characteristics and by PCR amplification of 16S rRNA by using Streptococcus agalactiae-specific primers. The genotyping of 12 isolates from fish samples and all 5 isolates from sewage samples was performed by random amplification of polymorphic DNA (RAPD) analysis. Culture methods identified 44 of 66 (67%) and 4 of 5 (80%) isolates obtained from fish and sewage samples, respectively, as S. agalactiae. The PCR amplification of 16S rRNA not only confirmed the results of conventional methods but also resulted in additional identification of 14 of 66 (21%) isolates obtained from fish samples and the remaining isolate recovered from sewage sample, as S. agalactiae. A total of 9 RAPD patterns were observed among the 17 isolates studied; these RAPD patterns were grouped into three clusters. Interestingly, four of the isolates recovered from sewage samples produced nearly identical RAPD band patterns (85-100% similarity) with some of the S. agalactiae strains isolated from Mullet kidney and brain indicting the possibility of sewage being the source of infection.