When collecting a fecal sample, it should be preserved with which of the following?

When collecting a fecal sample for analysis, preservation is crucial to ensure the sample remains intact and that test results reflect the true state of the sample without degradation or contamination. Sodium thiosulfate is commonly used as a preservative in the collection of fecal samples because it effectively neutralizes chlorine and other disinfectants that might be present in the water, which could otherwise interfere with the analysis of the sample.

Using sodium thiosulfate helps maintain the viability of microbial organisms within the sample, enabling accurate assessments of contaminants such as fecal coliforms, E. coli, and other pathogens. This preservation is particularly important for the microbiological testing of fecal samples, as it prevents the death of the bacteria that would otherwise skew the results.

Other substances like chlorine or alcohol would negatively affect the sample by killing the organisms that need to be analyzed, while glycerin does not serve as an ideal preservative for microbial testing. Therefore, sodium thiosulfate is the best choice for preserving fecal samples to maintain their integrity for subsequent analysis.