Primary and Secondary Immune Response to Formalin Inactivated Local Isolates of Staphylococcus aureus Type 8 and Type 5 in RabbitsAuthor(s): Subhashchandra M.Gaddad, Sandeep S. Angadi, Girish C. Math, H. Usha and Shivannavar CT
Background and Objectives: Staphylococcus aureus is a major cause of nosocomial and community acquired infections, the control of which has become difficult due to origin ofmultidrug resistantMRSA(MDR-MRSA). Development of an effective vaccine, especially against a surface antigen is considered to be an effective alternative for dealing with MDR-MRSA. In order to evolve an effective vaccine candidate it is mandatory to evaluate the antigenicity of the effective vaccine candidate in laboratory animals so that an optimum antigenic dose of these organisms could be determined. The present study was designed to evaluate the primary and secondary immune response to formalin inactivated local isolates of S.aureus type 8 and type 5 whole cell antigens in rabbits. Methods: A total of 150 S.aureus clinical isolates were obtained and were subjected for biochemical characterization and capsular typing. Primary and secondary immune response to formalin inactivated local isolates of S.aureus type 8 and type 5 strains in rabbits was determined. Serum specificity of both type 8 and type 5 antisera were determined to assess the cross reactivity between the two sera. Results: Of the 150 S.aureus isolates, 90(60%) isolates were found to be type8, 37(25%) were found to be type5 and 23(15%) isolates were non typeable. The antibody titers were found to be similar in case of both type8 and type5 in immunized rabbits with a peak primary immune response of 2560 on day 21 and remained constant up to 45 days.Asharp decline in titer was found between day 45 and day 60 and a vigorous secondary immune response of 2560 by 75th day was observed after a booster dose on day 60 which remained constant till 120th day.