الفهرس 
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Abstract
Stenotrophomonas maltophilia is a globally emerging Gram-negative opportunistic pathogen, that can cause bacteremia, ocular infection, endocarditis and respiratory tract infection (RTI), wound infection, urinary tract infection (UTI) meningitis, skin, and soft tissue infections. Because of S. maltophilia intrinsic and acquired drug resistance potential, this microorganism has become increasingly resistant to several antibiotics such as (3-lactams, quinolones, aminoglycosides, tetracyclines. Developing strategies such as vaccination is crucial to tackling the increasing antibiotic resistance. Vaccination approach provides long term protection against infection, prevents the onset of the infection, can target several microbial antigens, and diminishes the antibiotic consumption, resulting in controlling antibiotic resistance.
Depending on the reverse vaccinology approach, the present study demonstrates a successful cloned potential of the antigen Ax21. Results were confirmed through DNA first- generation sequencing. To assess the potential immunogenicity, the Ax21 antigen was subjected to western blotting. Sera of previously S. maltophilia injected mice, were used as primary antibody and total IgG level was detected. The resulted blot revealed that, Ax21 might have a potential antigenicity and the protein would be subjected to the animal trials.
The animal experiments were conducted to assess the in vivo potential of Ax21 to vaccinate the mice against S. maltophilia induced infection. Ax21 injected groups have successfully shown protection in the kidney, liver, lung, and heart. ELISA for mice sera gave significant results upon measuring total IgG, IgGl, and IgG2a levels. The immunized mice antibodies were also able to neutralize and opsonize S. maltophilia in vitro. Moreover, Ax21 protein significantly diminished the liver histopathological signs upon S. maltophilia infection such as vacuolation, bile duct necrosis, fibrosis, and inflammation. In conclusion, Ax21 can be considered as a promising antigen that confers a high level of protection against S. maltophilia infection in mouse model.