MVSc

A study was undertaken to isolate the bacteria associated with respiratory tract infections in rabbits. In this study, isolation, identification and antibiotic susceptibility of the isolates as well as determination of their pathogenicity to mice were carried out. Samples were collected from ailing and dead rabbits. Nasal swabs from the ailing rabbits showing clinical signs such as nasal discharge and respiratory distress, tracheal and lung samples of the dead rabbits with post mortem lesions such as pneumonia, congestion of lungs and haemorrhages of trachea were collected for the isolation trials. These samples were collected from rabbit farm attached to Kerala Agricultural University, commercial farms in Malapuram district, dead rabbits brought to Centre of Excellence in Pathology for post mortem and ailing animals brought for microbiological examination to the Department of Veterinary Microbiology. A total of 62 samples were collected, comprising of 30 nasal swabs, 25 lung samples and 7 tracheal swabs, for the isolation of the organisms.

Brain Heart Infusion Agar (BHIA) and Blood Agar were used for the primary isolation of the organisms. In the present study 32 isolates were obtained in which Staphylococcus sp. contributed 59.56 per cent of the total isolates, E. coli contributed 25 per cent, Klebsiella sp. 9.43 per cent, Streptococcus uberis 3.31 per cent and Pasteurella multocida 3.13 per cent. The bacteria were isolated and identified based on morphology, cultural and biochemical tests. In Staphylococcus sp. 19 isolates were obtained, comprising of Staphylococcus aureus-11, Staphylococcus scuri -2 , Staphylococcus xylosus- 1, Staphylococcus intermedius-2, Staphylococcus cohnii -2 and Staphylococcus lentus- 1. Other isolates were Streptococcus uberis -1, Pasteurella multocida -1, E. coli -8, Klebsiella pneumoniae -2 and Klebsiella ozaenae-1.

Most of the Staphylococcus sp. showed resistance to sulphadiazine, polymyxin B, co-trimoxazole, amoxycillin and oxytetracycline. The antimicrobial susceptibility pattern shown by the isolates exhibited multi-drug resistance. Multi drug resistance was also observed for E. coli isolates to amoxycillin, cefuroxime, gentamicin, carbenicillin, methicillin, chloramphenicol, enrofloxacin, oxytetracycline, penicillin G, nitrofurantoin, cefotaxime, oxacillin, streptomycin and erythromycin. Klebsiella sp. only showed sensitivity to enrofloxacin, gentamicin, cefotaxime, streptomycin and ciprofloxacin and highly resistant to amoxycillin, carbenicillin, methicilin, oxytetracycline, co-trimoxazole, penicillin G, nitrofurantoin, sulphadiazine, polymyxin B, bacitracin, erythromycin and ciprofloxacin.

On pathogenicity testing in mice only four isolates of S. aureus, five isolates of E. coli, two isolates of K. pneumoniae and one isolate of Pasteurella multocida caused death of the mice. The other isolates of S. aureus didn’t cause death of mice but could be re-isolated from the sacrificed mice after completion of the observation period. The S.scuri, S. xylosus, S. intermedius, S. cohnii and S. lentus isolates didn’t cause death in mice and the organisms were not re -isolated from lungs, liver, spleen and heart of the mice on sacrifice after 14 days observation period. The Streptococcus uberis isolate also didn’t cause death in mice and the organisms could not be re-isolated from lungs, liver, spleen and heart of the sacrificed mice.