Immunomagnetic separation for isolation and enrichment of Lacticaseibacillus paracasei strain Shirota from human feces

Abstract

Probiotics are live microorganisms that, when consumed in adequate amounts, confer health benefits on the host. The beneficial effects of probiotics are believed to be exerted when the microbes reach the intestine alive and engage in metabolic activity. The number of ingested probiotics that are able to reach the intestine is much fewer than that of the commensal intestinal bacteria. This makes it difficult to characterize the physiological state of probiotics in vivo owing to interference by other bacteria. Here, we established and evaluated an immunomagnetic separation (IMS)-based approach using a strain-specific monoclonal antibody to isolate Lacticaseibacillus paracasei strain Shirota (LcS) from human feces. Six healthy adults ingested a bottle of LcS-containing commercially available fermented milk each day for 4 consecutive days, and feces were collected after the final ingestion. Our approach successfully yielded a collection of more than 70 % of LcS from fecal samples in all subjects. Furthermore, the proportion of LcS among total bacteria, which initially stood at approximately 1 % before IMS, surged to over 70 % after IMS. This substantial increase signifies a concentration of LcS several-fold higher than the original fecal ratio. We conclude that LcS can be separated and enriched from human feces with acceptable level of efficiency and specificity by using our IMS approach.