Abstract
Mannheimiahaemolyticais the principal bacterial pathogen associated with bovine respiratory disease (BRD). As an opportunistic pathogen, M. haemolyticais also frequently isolated from the respiratory tract of healthy cattle. This study examined the incidence of M. haemolytica using deep nasal swabs from diseased cattle, buffaloes, sheep and goat as well as from their closely contact apparently normal animals (n = 225) and pneumonic lung tissues (n=90) then identification of the isolates by conventional culture method, biochemical and confimed by molecular tecqnique, finally assessment the genentic diversity between the confirmed isolates. Out of 315 samples examined, Mannheimia was isolated in 5% (4/75) ofcattlenasal and lung samples and 3.33%(3/90)of sheep samples. Identification of these isolates were confirmed by polymerase chain reaction (PCR) using species specific primer (PHSSA) derived from serotype specific antigen (ssa) gene. The amplification of genomic DNA obtained was corresponding to the anticipated size of 237bp.PCR was used to screen isolates for virulence outer membrane lipoprotein (gs60), O-sialoglycoproteinendopeptidase (gcp) and antimicrobial resistance (blaROB-1)genes. The virulence genes gs60 and gcp were present in all isolated M. haemolyticaat 329 and 227bp respectively, while antimicrobial resistant blaROB-1 gene was present in only two isolates at 685pb. Finally assessment the genetic differences among M. haemolytica isolates by partial genome sequencing of (gs60) gene blaROB-1 gene.

Key words: Mannheimiahaemolytica strains, bovine, respiratory, diseases