Cell surface‐associated aggregation‐promoting factor from L actobacillus gasseri SBT 2055 facilitates host colonization and competitive exclusion of C ampylobacter jejuni

Summary C ampylobacter jejuni , one of the most common causes of gastroenteritis worldwide, is transmitted to humans through poultry. We previously reported that L actobacillus gasseri   SBT 2055 ( LG 2055) reduced C . jejuni infection in human epithelial cells in vitro and inhibited pathogen colonization of chickens in vivo . This suggested that the LG 2055 adhesion and/or co‐aggregation phenotype mediated by cell‐surface aggregation‐promoting factors ( APFs ) may be important for the competitive exclusion of C . jejuni . Here, we show that cell surface‐associated APF 1 promoted LG 2055 self‐aggregation and adhesion to human epithelial cells and exhibited high affinity for the extracellular matrix component fibronectin. These effects were absent in the apf1 knockout mutant, indicating the role of APF 1 in LG 2055‐mediated inhibition of C . jejuni in epithelial cells and chicken colonization. Similar to APF 1, APF 2 promoted the co‐aggregation of LG 2055 and C . jejuni but did not inhibit C . jejuni infection. Our data suggest a pivotal role for APF 1 in mediating the interaction of LG 2055 with human intestinal cells and in inhibiting C . jejuni colonization of the gastrointestinal tract. We thus provide new insight into the health‐promoting effects of probiotics and mechanisms of competitive exclusion in poultry. Further research is needed to determine whether the probiotic strains reach the epithelial surface.