0472 Characterization of bovine nasopharyngeal lactic acid bacteria and their in vitro antimicrobial activities against the respiratory pathogen Mannheimia haemolytica
Bibliographic record
Abstract
Most research on bacteria in the bovine nasopharynx has focused on pathogens implicated in respiratory disease. There is limited information on commensals, such as lactic acid bacteria (LAB), which are important to mucosal health and have been investigated as probiotics to inhibit pathogens. The purpose of this study was to characterize the bovine nasopharyngeal LAB and their in vitro antimicrobial activities against Mannheimia haemolytica. The diversity of nasopharyngeal LAB was investigated in two separate studies using DNA– or culture-based techniques. In the first study, nasopharyngeal samples were collected from calves (n = 14) on a farm before shipment to a feedlot (d 0), and then 2, 7, and 14 d after feedlot placement. Swabs were processed for DNA extraction and the 16S rRNA gene was PCR-amplified and sequenced using the MiSeq platform. In the second study, nasopharyngeal swabs were collected from calves (n = 70) sampled at feedlot entry and 60 d afterward. The swabs were processed for the isolation of LAB using selective media. A subset of LAB (n = 66) was identified by sequencing the full-length 16S rRNA gene and isolates were subsequently screened for inhibition of M. haemolytica using the agar slab method. From the first study, high–throughput sequencing showed that the total LAB (defined as the order Lactobacillales) constituted 4.2% of the nasopharyngeal bacterial microbiota and consisted of 23 genera. Within LAB, 6 different families were identified that included Streptococcaceae (49.2%), Carnobacteriaceae (23.9%), Aerococcaceae (16.0%), Enterococcaceae (5.6%), Lactobacillaceae (5.3%), and Leuconostocaceae (0.26%). The relative abundance of total LAB increased by 97% from d 0 to 2 and remained greater for the 14 d of feedlot placement, compared with d 0 (P < 0.05). Interestingly, however, the Lactobacillaceae family decreased (P < 0.05) from d 0 to 2, demonstrating that not all Lactobacillales members increased after feedlot arrival. Using culture–based methods, only 6 genera of LAB were isolated: Streptococcus (39.2%), Lactobacillus (37.1%), Enterococcus (10.3%), Aerococcus (9.3%), Corynebacterium (3.1%), and Pediococcus (1.0%). Among the screened LAB isolates, species within Lactobacillus exhibited the strongest inhibition against M. haemolytica, with zones of inhibition ranging between 16 and 23 mm. Our results show that the relative abundance of nasopharyngeal LAB can change after cattle are transported to a feedlot and that some LAB are able to inhibit the respiratory pathogen M. haemolytica. These LAB may have potential as nasal probiotics for the mitigation of bovine respiratory pathogens.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".