Background and Aim: Mannheimia haemolytica is a Gram-negative, non-motile, and non-spore-forming rod-shaped coccobacillus bacterium. On blood agar plate, it shows complete hemolysis. This bacterium constitutes a part of normal flora of the upper respiratory system of ruminants. It is considered as the opportunistic pathogen and the main factor of pneumonic pasteurellosis, which has caused a severe economic loss in sheep and cattle industries. Considering the prevalence of the disease in sheep and goat population in the dry and hot regions of the country in general and in Fars province in particular in the form of pneumonia, the purpose of this study was to isolate and identify the bacterium M. haemolytica from the lung tissues of sheep slaughtered in Shiraz abattoir through culturing and polymerase chain reaction (PCR) methods.

Materials and Methods: In this study, a total of 2500 sheep's lungs were evaluated for finding pneumonic effects. Then, 161 infected pneumonic samples of lung tissues were investigated by culture and PCR methods.

Results: After cultivation, purification, and DNA extraction, 38 samples were found positive for M. haemolytica by cultivation and then all the 38 isolates were confirmed by PCR and multiplex PCR (mPCR). Results of this study indicated that culture and PCR are both practical in identification and isolation of this bacterium though culture is more time-consuming. The utilized mPCR has been more successful in the identification of the bacteria since it requires less time and cost.

Conclusion: In this study, PCR as a superior method among other methods of bacteriology for fast examination of infectious diseases and mPCR, which is a valuable tool for identification of M. haemolytica in clinical samples of animals, was used.

Keywords: Mannheimia haemolytica, pneumonia, polymerase chain reaction, sheep, Shiraz.

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