The bovine ocular microbiome: a multi-approach study of composition and antimicrobial activity

Area of Science:

• Veterinary Microbiology
• Animal Health
• Bovine Ophthalmology

Background:

• Infectious bovine keratoconjunctivitis (IBK), or pinkeye, is a growing concern in North American beef cattle operations.
• The ocular microbiome's role in mitigating IBK is under investigation.
• Current treatments like antimicrobials and vaccines have limitations.

Purpose of the Study:

• To characterize the ocular microbiome of cattle with and without IBK.
• To assess the in vitro inhibitory potential of commensal bacteria against IBK pathogens (Moraxella spp.).
• To identify specific bacterial species associated with healthy versus IBK-affected cattle.

Main Methods:

• Collected ocular swabs from 143 beef cattle (102 IBK-affected, 41 healthy).
• Utilized culture-based methods and shotgun metagenomic sequencing for microbiome characterization.
• Sequenced genomes of key bacterial isolates, including Moraxella spp. and commensals.
• Screened 52 commensal isolates for inhibition of Moraxella spp. in vitro.

Main Results:

• Identified 351 bacterial isolates across 61 genera; Bacillus, Streptococcus, Staphylococcus, and Moraxella were dominant.
• Shotgun metagenomics revealed significant differences in microbial composition between healthy and IBK-affected cattle.
• Eight species were more abundant in healthy cattle (e.g., Bifidobacterium globosum), while Arthrobacter luteus was enriched in IBK cases.
• Seventeen commensal isolates inhibited Moraxella spp., with Weizmannia coagulans, Lentilactobacillus buchneri, and Paenibacillus polymyxa showing strong activity.

Conclusions:

• The bovine ocular surface harbors a diverse microbiome.
• Several commensal bacterial strains demonstrate potential as therapeutics to inhibit IBK pathogens.
• Understanding the ocular microbiome may lead to novel strategies for managing pinkeye in cattle.