Influence of the temperature and selected nutrients on the isolation of salmonela from clinical specimens

Abstract

This study aimed to review the use of enrichment media for different sample types and to clarify which is the best medium and temperature of incubation processing for the isolation of Salmonella. Isolation is divided in five steps: pre–enrichment, selective enrichment, plating, biochemical identification and serotyping. The most common enrichment media are Selenite Cystine (SC), Tetrathionate (TT), Rappaport - Vassiliadis (RV) broths, and their derivatives, withthe addition or not of Novobiocin. TT broth presents a good efficiency in fecal samples of experimentally inoculated birds when incubated between 35 and 45°C, except when there is a low concentration of Salmonella. SC broth presents a good performance with fecal samples and chicken carcasses cultivated in a temperature varying between 37 and 43 ºC, as well as to identify samples withlow cell concentrations. The RV broth when used in samples of rectal swabs from cattle are not effective, however, when used withsamples of chicken or turkey carcasses, and analysis on eggs, or with samples with elevated microbial load, at a temperature of 42^oC,present great results. The choice of the most suitable enrichment medium and the incubation temperature of the broth for isolation of Salmonella will directly depend on the type of sample to be processed, since each medium will provide better accuracy in different circumstances.