Antimicrobial Activity Of Chitosan Combined With Antibiotics Against Mastitis Causing Pathogens

Abstract

Bovine mastitis, the most common dairy cattle disease, is a mammary gland infection that results in decreased milk production and quality. Antibiotics are the main treatment for this infection, however, with the excessive use of antibiotics, antibiotic resistance has become a major problem. Therefore, it is essential to find alternative treatments. Previous studies showed that chitosan has good antimicrobial activity and combination of chitosan and antibiotics can improve the treatment outcome. This research aimed to investigate the synergistic effect of chitosan and antibiotics (ampicillin, amoxicillin, oxacillin, and levofloxacin) against four common mastitis causing pathogens Staphylococcus epidermidis, Streptococcus agalactiae, Streptococcus uberis, and Pseudomonas sp. Minimum inhibitory concentration (MIC) was carried out to obtain the checkerboard testing ranges and checkboard assay was then used to assess the synergy of chitosan and antibiotics against the four bacteria by determining fraction inhibitory concentration (FIC). Results showed that the combination between chitosan and ampicillin, amoxicillin, oxacillin, and levofloxacin against mastitis-causing pathogens have some synergistic interactions with the FIC value ≥ 0.5 and ≤ 1. The effects, however, are not strong enough to conclude as strongly synergistic (FIC < 0.5). To conclude, though low, chitosan has antimicrobial activity and synergistic effects with antibiotics.