Piliated Lactobacillus rhamnosus (pLR) strains have attracted much attention owing to their excellent mucus adhering capacity and immunomodulatory effects. Here, we aimed to develop a rapid, sensitive method for isolating pLR strains in complex ecosystems using immunomagnetic separation (IMS) with colony immunoblotting (CIB).Methods and Results:
Magnetic nanobeads (diameter: 180 nm) conjugated with anti-pLR SpaA pilin antibodies (anti-SpaA) were prepared and used to preconcentrate pLR strains in samples, followed by confirmation with anti-SpaA-based CIB analysis. Under optimized experimental conditions, IMS-CIB selectively recovered pLR strains from 107 CFU ml−1 of faecal microbiota samples spiked with 2·9 × 101 to 2·4 × 106 CFU ml−1 of pLR strains. No positive colonies were detected in samples without addition of pLR strains. The detection limit of IMS-CIB was 29 CFU pLR ml−1 of faecal microbiota, which is much lower than that of CIB without IMS preconcentration (2·0 × 104 CFU ml−1).Conclusions:
IMS-CIB allowed selective preconcentration of pLR strains in highly heterogeneous bacterial suspensions and direct detection of pLR colonies, which remained readily available for subsequent isolation.Significance and Impact of the Study:
Our findings established an effective method for selective enrichment and detection of pLR strains.