ANLP-V3 peptide reduces bacterial load and inflammation in MDR S. aureus mastitis mouse model

Therapeutic intervention for bovine mastitis, a prevalent and costly disease in dairy farming, faces significant challenges due to the rise of antimicrobial resistance (AMR) and the formation of biofilms by causative agents like Staphylococcus aureus (S. aureus). Current antibiotics frequently fail against multidrug-resistant (MDR) strains, necessitating novel approaches. Antimicrobial peptides (AMPs) represent a promising alternative due to their broad-spectrum activity and distinct mechanisms that can circumvent traditional resistance pathways, offering a potential solution to this critical veterinary and public health issue.

Researchers evaluated the synthetic antimicrobial peptide, ANLP-V3, for its efficacy against mastitis induced by MDR S. aureus ATCC 700699. Initial Minimum Bactericidal Concentration (MBC) assays and time-dependent antibacterial activity were performed ex vivo in UHT milk. For in vivo assessment, 36 lactating Swiss albino mice were divided into 6 groups (n=6 per group) and infused via the intramammary route. Groups included normal saline, S. aureus ATCC 700699 infection, and ANLP-V3 (100 µg) alone. Treatment groups received ANLP-V3 (100 µg) either prior to infection, co-infused with infection, or post-infection. Primary endpoints included bacterial CFU counts and histopathological examination of mammary tissue.

In ex vivo studies, ANLP-V3 demonstrated bactericidal properties in MBC assays and time-dependent antibacterial activity in UHT milk. In vivo, all ANLP-V3 treatment regimens significantly reduced bacterial burden. Compared to the infection control group, all ANLP-V3 treated groups showed approximately 1 log10 reduction in bacterial CFU. This consistent reduction highlights the peptide's potent antimicrobial effect regardless of the timing of administration relative to infection. Furthermore, histopathological examination of mammary gland tissues from ANLP-V3 treated mice revealed markedly reduced inflammatory cell infiltration, mild pathological lesions, and lower bacterial counts compared to the severe inflammation and high bacterial loads observed in the infection control group. These findings collectively indicate a robust therapeutic potential for ANLP-V3.

ANLP-V3 treatment consistently achieved approximately 1 log10 reduction in bacterial CFU across all therapeutic regimens compared to untreated infection controls, alongside significant improvements in mammary tissue pathology.