Evaluation of the Synergistic Antimicrobial activity of Amikacin with Norfloxacin against Pseudomonas aeruginosa isolated from buffaloes clinical mastitis

Abstract

Mastitis is a serious and economically problem commonly prevalent in most dairy cattle and buffaloes herds. Pseudomonas aeruginosa (P. aeruginosa) is opportunistic pathogens implicated 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. 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 proved to be 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). In conclusion, 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.