A new strain of Acinetobacter baumannii and characterization of its ghost as a candidate vaccine

Abstract

Background: Human infection by Acinetobacter baumannii has been increased due to its resistance against most of the antibiotics. Therefore, the present study aimed to design a candidate vaccine against A. baumannii infection. Methods: The protein and DNA contents of A. baumannii Ali190 were extracted using different critical concentrations of hydrogen peroxide, sodium hydroxide and sodium carbonate leading to the ghost of A. baumannii Ali190. Transmission and scanning electron microscope showed that it retained the 3D structure of its cell membrane. The ghost injected to rats via different routes of administrations including oral, subcutaneous, intramuscular, intraperitoneal, subcutaneous with adjuvant, and intramuscular with adjuvant. Results: β-Lactamase OXA-51 gene, is a predominant gene in all Acinetobacter strains, the gene was partially sequenced. The DNA sequence of OXA-51 gene showed 98% homology with A. baumannii isolate 6077/12 and also showed less homology percentage with other strains of Acinetobacter. A new strain of Acinetobacter has been deposited in Gene Bank under accession number MG062776. All routes of ghost administration showed full protection against live bacteria except oral administration showed 67% protection. On the other hand, all non-vaccinated rats did not survive after infection with live bacteria. SDS-gel electrophoresis of protein patterns of both A. baumannii and its ghost showed common protein bands with molecular weights 70, 60, and 23 kDa which were detected using western immunoblotting after raising the primary antibodies against A. baumannii ghost. The levels of INF-γ were significantly increased in all vaccinated groups, particularly in subcutaneous and subcutaneous with adjuvant compared to the control group. Conclusion: With the exception of oral administration, all vaccinated rats via different routes of ABG administration showed full protection (100%) against live A. baumannii. However, 100% mortality rate was observed in non-vaccinated rats. Therefore, ABG could be useful as a candidate vaccine against A. baumannii infection. Keywords: A. baumannii ghosts, Cellular immunity, Vaccine candidate, Humoral immunity