Mannheimia haemolytica (M. haemolytica) is a gram negative bacterium which can infect humans and animals. It's commensal as a normal flora of the nasopharynx and tonsils in cattle, sheep and goats, pneumonic pasteurellosis is one of the most economically important infectious disease in goats worldwide prevalence. This study aimed to investigate the incidence of M. haemolytica by bacteriological and molecular characterization in goats. One hundred nasopharyngeal swabs were collected from apparently healthy field goats, seven lung tissue specimens and five nasal mucus swabs from slaughtered goats in Baghdad. All samples were cultured on Blood and MacConky agars. Biochemical tests and EPI20E kit were used for identification of the suspected colonies. 5 (4.46%) isolates of M. haemolytica were identified phenotypicaly and confirmed diagnosis by polymerase chain reaction (PCR) technique using two primers 16s rRNA and 12s rRNA genes .The results of this study concluded that identification of M. haemolytica by PCR was in accordance with those of phenotypic tests and it providing the basis for effective preventative strategies through epidemiological studies performance.

Citrobacter freundii (C. freundii) is responsible for a number of significant opportunistic infections. The present research was aimed to estimate the immune response of rabbits immunized with whole cell sonicated antigen (WCSA), lipopolysaccharide (LPS), and DNA antigens (Ag) extracted from C. freundii. Twenty-four Albino rabbits of both sexes, with 2-3 kg body weight, were divided randomly into four groups (6 rabbits for each). Two types of tests were performed including ELISA and skin test (delayed type hypersensitivity, DTH)). The 1st group was immunized with WCSA (1000 μg/mL). The 2nd group was immunized with LPS Ag at the same dose. The 3rd group was immunized with DNA extracted Ag (0.083 μg/mL). The 4th group (negative control) was injected with 1 mL PBS (pH 7.2) subcutaneously. After 14 days, rabbits were given booster doses of same Ag. The immunized animals showed significant increase of IgG and IL-6 concentration (P<0.05) following 28, 32, 46, 50 and 60 days of immunization in comparison with the negative control group. Concerning DTH, it showed an increase in the means of induration and erythema, with significant differences (P˂0.05) exerted by the concentrated antigens in all immunized groups after 24 h and 48 h compared with diluted Ag and negative control group. In conclusion, WCSA and LPS Ag, in comparison to DNA Ag, were observed to promote stronger humoral (IgG) and cellular (DTH and IL-6) immune responses. DNA Ag, on the other hand, elicited a weaker humoral and cellular immune response than other Ag.

Mannheimia haemolytica together with Pasteurella multocida represents as a major bacterial causative agent of cattle, sheep and goats respiratory diseases and its one of the most important causes for economic losses to these animals .Commercially available vaccines were used to prevent infections caused by P. multocida and M. haemolytica. Thus, the aim of the present study was to evaluate the cross protection efficacy of two vaccines to protect mice against M.haemolytica, studying humeral immunity, using Enzyme-Linked Immunosorbent Assay. Forty five mice were divided into three equal groups, group one and two were inoculated subcutaneously  4μl\JOVAPAST® and 1μl of Al-kindy vaccines respectively, while the third group was with 0.5 ml sub cutaneous PBS. LD50for M.haemolytica was estimated as 2× 106 cfu \ml and challenge test was conducted by dropping 0.05 ml 2× 106 cfu \ml intranasally after three weeks of immunization for the three groups. The results of Enzyme-Linked Immunosorbent Assay, showed significant increase of antibody titters at (P<0.01) in (group 1 and 2) after first and second weeks post immunization, in comparison with control group. Also, the re-isolation of M.haemolytica from lungs tissue of all groups after challenged were positive with significant difference between control and immunized group, control group was 4× 108 cfu ∕ml which was higher than immunized group one and group two,which were 2.5×104 cfu∕ml and 3,5×105 cfu∕ml respectively after 24 hour of vaccine. In conclusion, the two commercial vaccines showed good cross protection efficacy against M. haemolytica, but JOVAPAST® vaccine showed higher efficacy than Alkindy vaccine, as that it contain  two  heterologous  killed strains and providing the basis for production a vaccine from the two  pathogen of local strains.