Episomal virulence gene burden in coliform mastitis pathogens is linked to TLR4/CD-14/LRRK1 driven oxidative inflammatory signaling and systemic immunometabolic disturbances in Holstein dairy cows.

Virulence gene profiling combined with host biomarkers predicts mastitis progression to systemic disease in dairy cows.

This study investigated the relationship between virulence gene burden in coliform mastitis pathogens and the severity of acute coliform mastitis (ACM) in Holstein dairy cows, specifically examining how pathogen virulence drives systemic immunometabolic disturbances. Of 168 cows with ACM, 18 met inclusion criteria and were categorized into localized ACM (LACM, n=9) and systemic ACM (SACM, n=9), with 10 healthy controls. Causative organisms (Escherichia coli and Klebsiella pneumoniae) were identified via MALDI-TOF MS, serotyped, and evaluated for antimicrobial susceptibility and virulence determinants by PCR. SACM strains demonstrated extensively drug-resistant (XDR) phenotypes with high multiple antibiotic resistance (MAR) indices and harbored multiple virulence determinants (iss, ompT, iucD), while LACM strains carried only iss. SACM cows showed significantly greater elevation of antimicrobial peptides, acute-phase proteins, hepatobiliary, renal, and cardiac injury markers, and metabolic imbalances compared to LACM and controls. TLR4/CD-14/LRRK1-mediated inflammatory signaling and suppression of antioxidant defenses were markedly intensified in SACM. Correlation matrix and Mantel test analyses confirmed strong inter-organ biomarker associations and coordinated oxidative-inflammatory cascade networks in SACM (r>0.75, P≤0.01). These findings suggest that combining virulence profiling of causative pathogens with host-response biomarker assessment may improve prediction of mastitis progression toward systemic disease and guide more targeted clinical management strategies in dairy cattle.

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