Lactobacillus strain ecology and persistence within broiler chickens fed different diets: identification of persistent strains

Abstract

Lactobacilli are autochthonous residents in the chicken gastrointestinal tract, where they may potentially be used as probiotics, competitive exclusion agents, or delivery vehicles. The aim of this study was to use an in vivo model to investigate the effect of diet and competing lactic acid bacteria on the colonization of inoculated Lactobacillus strains, with the goal of identifying strains which can consistently colonize or persist for an extended period of several weeks. Chicken-derived Lactobacillus strains were genetically marked with rifampin resistance and administered on day 0 to chickens fed either a normal commercial diet or a specially formulated high-protein diet. Chickens fed the high-protein diet were also coinoculated with two different mixes of additional lactic acid bacteria. Enterobacterial repetitive intergenic consensus sequence-based PCR (ERIC-PCR) was used to identify rifampin-resistant isolates recovered from chickens. Three strains, belonging to the species Lactobacillus agilis, Lactobacillus crispatus, and Lactobacillus vaginalis, were commonly reisolated from the chickens on both diets at days 21 and 42. The ability of these strains to persist was confirmed in a second chicken trial. All three strains persisted throughout the production period in the chickens fed a commercial diet, while only the L. agilis and L. vaginalis strains persisted in the chickens fed the high-protein diet. In both in vivo trials, competing lactic acid bacteria modified representation of the strains recovered, with all three stains capable of competing in the presence of one or both mixes of coinoculated strains. The in vivo model successfully identified three persistent strains that will be characterized further.

FIG. 1.

Identification of Rif^r isolates in chicken trial 1. (A) Distribution of Lactobacillus, Enterococcus, and Pediococcus isolates in each isolator at day 21 and day 42; (B) distribution of Lactobacillus strains in each isolator at day 21 and day 42; (C) distribution of the identified Lactobacillus isolates in the inoculated and in-contact chickens in each isolator at day 21 and day 42. An asterisk indicates that the source of the strain may be Rif^r background LAB.

FIG. 2.

Identification of Rif^r isolates in chicken trial 2. (A) Distribution of Lactobacillus, Enterococcus, and Pediococcus isolates in each isolator at day 21 and day 42; (B) distribution of the Lactobacillus strains in each isolator at day 21 and day 42. An asterisk indicates that the source of the strain may be Rif^r background LAB.

FIG. 3.

Distribution of Lactobacillus strains within individual chickens and gut sections in trial 2. An asterisk indicates that data were not available for the following: in the commercial diet, the crops of chickens 2 and 3 and the jejunum of chicken 4; and in the high-protein diet, the ileum and crop of chickens 1 and 2, respectively.