Evaluation of crAssphage as a human-specific microbial source-tracking marker in the Republic of Korea

CrAssphage is a novel and by far the most abundant bacteriophage in the human gut and has been proposed as a human-specific microbial source tracking (MST) marker. However, its global use as a human-specific MST marker requires validation in more extensive regions. The purpose of this study was to evaluate the specificity and abundance of the human-specific MST marker crAssphage with PCR and RT-PCR assays in human and animal feces in Korea. The prevalence of crAssphage was confirmed in 94 human feces samples (subjects: 19 to 45 years old) and 56 animal feces samples (from birds, raccoons, squirrels, weasels, deer, wild boars, hares, cats, and dogs). CrAssphage showed sensitivity of 0.39 and specificity of 1.00 in Korea, with a sequencing analysis showing that genotype II was dominant at 71.9%. The quantitative analysis showed that crAssphage is sufficiently abundant in human feces given the high concentration range of 4.26 to 8.25 log gene copies (GC)/ng in human feces. In conclusion, this study confirmed the crAssphage as a specific and abundant MST marker with which to identify human fecal contamination in Korea.