Mastitis is a serious and economically problem commonly prevalent in most dairy cattle and buffaloes herds. Pseudomonas aeruginosa (P. aeruginosa) is opportunistic pathogens involved in veterinary disorders including clinical mastitis in buffaloes. This study aimed to investigate the antibiogram pattern and synergistic effect of amikacin and norfloxacin against resistant P. aeruginosa isolates from mastitis origin. In addition, detection of some virulence and antibiotics resistance genes. Two hundred buffaloes were examined and sixty mastitis milk samples were collected from clinical cases from the period from October 2021 until March 2022. The acute mastitis sings were assessed according to cardinal signs of inflammation and milk abnormalities. Out of two hundred buffaloes, sixty (30%) were diagnosed as clinical mastitis according to inflammatory signs and the culture results reveled only 5 (8.3%) were P. aeruginosa. Most of P. aeruginosa exhibited resistance to most antimicrobials classes. Meanwhile, the minimal inhibitory concentration (MIC) for amikacin and norfloxacin is significantly reduced from 64 µg/mL to 1 µg/mL and from 256 µg/mL to 8µg/mL respectively with frictional inhibitory concentration (FIC) index 0.25. Therefore, the FIC index recognized a synergistic activity between amikacin and norfloxacin against all P. areuginosa isolates. The mPCR was an efficient tool for detection of virulence genes (exoT, toxA, oprL, and isaI) at 152, 396, 504, 606 bp respectively. In addition, all the P. aeruginosa were found to carry the resistance genes (qnrS, qnrA, aadB). The combination of norfloxacin plus amikacin suppressed the resistance pattern P. aeruginosa isolates. Therefore, their combination showed synergistic bacterial potential antimicrobial activity in treatment of mastitis due to P. aeruginosa infection and help in reducing the resistance problem.
Keywords | Amikacin, P. areuginosa, mPCR, Norfloxacin, Virulence, Resistance, Mastitis