Inativação fotodinâmica para controle de agentes causadores da mastite bovina

Abstract

Bovine mastitis, an inflammation of the mammary gland in dairy cows, is frequently associated with bacterial infections, negatively impacting milk quality, animal welfare, and public health. The disease can manifest in clinical, subclinical, or chronic forms, causing substantial economic losses in dairy production due to reduced milk yield and product devaluation. Conventional treatment relies on antimicrobial use; however, excessive application of these drugs contributes to the emergence of bacterial resistance, threatening animal and human health. This study aimed to evaluate the efficacy of Antimicrobial Photodynamic Therapy (aPDT) using palladiummetalated porphyrins (Porf@DPPE, Porf@DPPP, Porf@DPPB, and Porf@DPPF) against bacteria isolated from mastitis cases. The photosensitizers were tested against Gram-positive and Gram-negative strains, with analysis of antimicrobial susceptibility and synergy with sulfonamides. Antimicrobial susceptibility testing demonstrated potential for optimizing therapeutic protocols to combat pathogenic resistance. Results revealed greater aPDT efficacy against Gram-positive bacteria, with significant inhibition at concentrations between 6.25–100 μM. The Porf@DPPP compound stood out for its broad-spectrum action, including activity against Gram-negatives (25–100 μM). The combination of aPDT and sulfonamides reversed the resistance exhibited by Escherichia coli against the antimicrobial after 30 minutes of irradiation, demonstrating a synergistic effect. DNA integrity analysis confirmed post-aPDT genomic damage, suggesting oxidative mechanisms as the basis for microbial inactivation. It is concluded that aPDT is effective against mastitis-associated pathogens and can be integrated with antimicrobials as a promising strategy for controlling resistant cases. Future studies should focus on evaluating in vivo toxicity, optimizing dosages, and integrating with preventive measures like strict milking hygiene and health management to enable practical application. This multifactorial approach, combined with responsible antimicrobial use, reinforces the promotion of One Health, connecting animal, human, and environmental health for sustainable and safe milk production.