Abstract

Staphylococcus aureus is considered one of the most important pathogens causing septic arthritis in poultry with significant economic losses. This study aimed to evaluate the efficacy of a locally prepared S. aureus vaccine against staphylococcal arthritis in poultry. Out of 78 samples collected from infected chickens showing clinical signs bumble foot, 10 field isolates were detected and confirmed phenotypically by culturing, Gram staining, biochemical and molecular identification to be S. aureus in prevalence of 12.82%. Molecular identification of clumping factor A (ClfA) and blaZ genes of S. aureus isolates revealed that the PCR amplification with ClfA and blaZspecific primers conducted with genomic DNA resulted in products of approximate size 638 bp and 833 bp, respectively. Phylogenetic tree for S. aureus ClfA virulence gene partial sequences was generated using maximum likelihood, neighbour joining and maximum parsimony in MEGA6. It showed clear clustring of Egyptian isolated strain (S. aureus ASM strain) and different S. aureus strains uploaded from GenBank. Sequence identities between the Egyptian isolated strain (S. aureus ASM strain)and different S. aureus strains uploaded from GenBank revealed 99.5% to 100% homology. Also, there was identity and homology in S. aureusblaZgene nucleotide sequence in the Egyptian isolated strain (S. aureus ASM strain)and the different S. aureus strains uploaded from GenBank revealed 96.1% to 98.9% homology. Phylogenetic tree for S. aureusblaZβ-lactamases resistant gene partial sequences showed clear clustring of the Egyptian isolated strain (S. aureus ASM strain)and different S. aureus strains uploaded from GenBank. The results of humoral immune response revealed that the geometric mean antibody values against locally prepared S. aureus vaccine measured by indirect hemagglutination test increased from 1st week post vaccination gradually till reached maximum level (322.5) at 6th week post boostering. The results showed an increased humoral antibody production in vaccinated group that was capable of preventing establishment of new S. aureus infection in vaccinated group compared to control group. The mortality rates in unvaccinated group was higher than that of vaccinated group were (42.5%, vs. 7.5%) at 1st and 2nd week post challenge (39.1% vs. 5.4%). The protection % in challenge assay of the prepared S. aureus vaccine was (92.5% and 87.5%) at 1st and 2nd week post challenge respectively. It could be concluded that the prepeared vaccine was safe, potent and protect birds against S. aureus infection.