Intranasal Bacterial Therapeutics Reduce Colonization by the Respiratory Pathogen Mannheimia haemolytica in Dairy Calves.

ABSTRACT: Six Lactobacillus strains originating from the nasopharyngeal microbiota of cattle were previously characterized in vitro and identified as candidate bacterial therapeutics (BTs) for mitigating the bovine respiratory pathogen Mannheimia haemolytica In the present study, these BT strains were evaluated for their potential to (i) reduce nasal colonization by M. haemolytica, (ii) modulate the nasal microbiota, and (iii) stimulate an immune response in calves experimentally challenged with M. haemolytica. Twenty-four Holstein bull calves (1 to 3 weeks old) received either an intranasal BT cocktail containing 6 Lactobacillus strains (3?×?109 CFU per strain; BT + Mh group) 24?h prior to intranasal M. haemolytica challenge (3?×?108 CFU) or no BTs prior to challenge (Mh, control group). Nasal swab, blood, and transtracheal aspiration samples were collected over the course of 16?days after BT inoculation. Counts of M. haemolytica were determined by culturing, and the nasal and tracheal microbiotas were evaluated using 16S rRNA gene sequencing. Serum cytokines (interleukin-6 [IL-6], IL-8, and IL-10) were quantified by enzyme-linked immunosorbent assay (ELISA). Administration of BT reduced nasal colonization by M. haemolytica (P?=?0.02), modified the composition and diversity of the nasal microbiota, and altered interbacterial relationships among the 10 most relatively abundant genera. The BT + Mh calves also had a lower relative abundance of Mannheimia in the trachea (P?

SUBMITTER: Amat S 

PROVIDER: S-EPMC7055656 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature