Comparison of modified semi - solid Rappaport - Vassiliadis to routine culture media for isolation of Salmonella from rectal swab specimens at Srinagarind Hospital

Abstract

Salmonella is an infectious agent of gastrointestinal disease. Rapid isolation and identification of this organism are important for early and effective treatment. Salmonella, as well as other enteric bacteria, shows similar growth and colonies on MacConkey agar and Salmonella-Shigella agar, which are commonly used for isolation of Salmonella in most clinical laboratories. For better isolation and differentiation of this organism from normal enteric flora, modified semi-solid Rappaport-Vassiliadis agar (MSRV) was compared with the routine culture media used in Clinical Microbiology Unit, Srinagarind Hospital. A total of 1,944 rectal swabs were cultured by both methods. It was found that 159 isolates (8.2%) of Salmonella were recovered in this study, 153 isolates (7.9%) from MSRV and 103 isolates (5.3%) from routine medium. Of these, 97 isolates (5.0%) were positive by both methods, 56 isolates (2.9%) were positive by MSRV only, while 6 isolates (0.3%) were positive by routine media only. This study showed that MSRV gave a better result than those of the routine culture media. Therefore, MSRV should be used as additional medium for efficiency of isolation of Salmonella from rectal swab in clinical microbiology laboratories.