Isolation and Identification of Aerobic Bacterial Flora in Nasopharyngeal Passageways of Apparently Healthy and Clinically Sick Sheep at Gondar University Veterinary Clinic

A cross sectional study was conducted from November, 2010 to April, 2011 with the aim of isolating and identifying aerobic bacterial flora in nasopharyngeal passageways of apparently healthy and clinically sick sheep at Gondar University Veterinary Clinic. Samples were collected aseptically from the nasal cavity of 142 investigated sheep and standard microbiological techniques were used for isolation and identification of bacterial species. From the total of 142 specimens (74 healthy and 68 clinically sick sheep) collected for bacteriological examination, 136 contained bacteria. A total of 152 bacteria were recovered in which 77 and 75 of them were from apparently healthy and clinically sick, respectively. The isolation rates of frequently identified isolates recovered from healthy sheep include; S. epidermidis (15.6%), E. coli (14.3%), C. pseudotuberculosis (11.7%) and S. aureus and M. luteus (9.1% each),. On the other hand, isolation rates of most frequently identified species among the 75 bacterial isolates include; S. aureus (17.3%), S. epidermidis (13.3%), and M. haemolytica and M.luteus (10.7% each).The majority of the isolates which colonize the nasal cavity of apparently healthy sheep were also recovered from clinically sick sheep with the exception of A. pyogenes and P. aeruginosa. In conclusion, most of the isolated bacteria commonly act as primary pathogens; however, Pasteurella and Mannhaemia spp, are recognized as opportunistic pathogens capable of causing disease if they pass the normal defenses of the host.