In-vitro susceptibility of three bacterial pathogens of catfish to 23 antimicrobial agents

Abstract

Three gram-negative bacterial pathogens isolated from diseased catfish Clarias batrachus and Heteropneustes fossilis were screened for susceptibility to twenty three antimicrobial agents by the Bauer disc diffusion method. Bacteria evaluated were Aeromonas hydrophila, Edwardsiella tarda and Haemophilus piscium. All bacteria were susceptible to ciprofloxacin, norfloxacin, oxytetracycline, tetracycline, chlorotetracycline, co-trimoxazole, gentamycin, trimethoprim and chloramphenicol. All three bacterial organisms were resistant to penicillin, clotrimazole, bacitracin, nitrofurazone, cloxacillin, amphotericin and erythromycin. Testing the pathogens against ciprofloxacin and norfloxacin gave larger zones of inhibition on diagnostic sensitivity test agar indicating their usefulness against common gram-negative bacterial disease outbreaks. The resistant potential of the bacteria against some of these antibiotics is discussed.