Ascorbic acid enhances ciprofloxacin antibacterial activity in vitro against isolates of Escherichia coli from subclinical mastitis cases of buffaloes

Abstract

Escherichia coli is one of the major bacteria along with Staphylococcus aureus and Streptococci that are encountered in mastitic milk samples obtained from subclinical mastitis cases in India. Ciprofloxacin is an antimicrobial fluoroquinolone, which is effective against Escherichia coli. As antioxidants like selenium, vitamin, E and Vitamin C have become adjunct therapeutic agents in the cases of mastitis along with antibacterial agents, the present study was aimed to find out the in vitro pharmacodynamic interaction of ascorbic acid with ciprofloxacin against E. coli isolated from mastitis milk samples of buffaloes. E. coli were isolated from the milk from buffaloes of sub clinical mastitis cases after clinical diagnosis. Cultural and biochemical tests were performed to identify the isolated organisms as E. coli from milk. Further DNA template isolated from the organism is subjected for polymerized chain reaction (PCR) for the specific primers Eco 2083 and Eco 2745 to confirm the identity of the organism. Minimum inhibitory concentration (MIC) of ciprofloxacin, ascorbic acid alone and combination of both compounds in serial dilution against clinical isolates of E. coli was performed using microplate method. Ciprofloxacin alone has shown MIC of 0.03 µg.mL‑1 against E. coli whereas ascorbic acid alone has no antibacterial activity. MIC of ciprofloxacin has been reduced to two fold (0.015µg.mL-1) when it was diluted in 8:2 to 4:6 ratio with ascorbic acid (0.1mg/ml) and thus indicating ascorbic acid potentiating the antibacterial activity of ciprofloxacin.