American-Eurasian Journal of Scientific Research 7 (6): 232-237, 2012 ISSN 1818-6785 © IDOSI Publications, 2012 DOI: 10.5829/idosi.aejsr.2012.7.6.66145 Corresponding Author: Mersha Chanie, Department of Veterinary Paraclinical Studies, Faculty of Veterinary Medicine, University of Gondar, P.O. Box, 196, Gondar Ethiopia. 232 Isolation and Identification of Aerobic Bacterial Flora in Nasopharyngeal Passageways of Apparently Healthy and Clinically Sick Sheep at Gondar University Veterinary Clinic Aden Omer, Ayalew Berhanu, Mersha Chanie and Tewodros Fentahun 1 1 1 2 Department of Veterinary Paraclinical Studies, Faculty of Veterinary Medicine, 1 University of Gondar, P.O.Box, 196, Gondar Ethiopia Department of Basic Veterinary Science, Faculty of Veterinary Medicine, 2 University of Gondar, P.O.Box, 196, Gondar Ethiopia Abstract: 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. Key words: Aerobic %Bacteria %Nasopharyngeal %Sheep %Nasal Swaps %Gondar INTRODUCTION Although a single agent may be the primary invader, Respiratory diseases of various etiologies have been presence of secondary or opportunistic invaders [3]. described in different domestic animals. However, the When the local resistance of respiratory mucus is problem is more common in sheep due to the fact that the lowered, bacteria growing in the nose and throat extend ratio of the alveolar surface to metabolic weight is very down wards, usually producing multiple bacterial low in sheep compared to other species [1]. Many specific infections [4]. Besides, most of the infectious agents that primary pathogens have been implicated sheep cause respiratory disease are ubiquitous in nature and are pneumonia. The most common bacterial causes of normal inhabitants of the nasopharynx of normal animals. pneumonia in sheep include pasteurella spp., This often creates difficulty with the interpretation of Mannheimia haemolytica, Actinomyces pyogenes and microbiological findings in outbreaks of respiratory several mycoplasma species. P. multocida and diseases [5]. m.haemolytica are important contributory pathogens in There are several studies conducted on both healthy enzootic or primary pneumonia in sheep, although their and pathological respiratory tracts of cattle, camel and pathogenic effects are enhanced when sheep are infected small ruminants in different regions of the country with viruses [2]. [6, 12]. However, their works, particularly in sheep, were most respiratory infections are complicated by the