A DNA VACCINE FOR PREVENTION OF STAHYLOCOCCUS AUREUS INFECTION IN ORTHOPAEDIC INFECTION

Abstract

Introduction and Aims: A phenotypic and proteomic approach has identified novel targets for the development of a DNA vaccine to prevent Staphylococcus aureus infection in orthopaedics.

Approximately 1% of joint replacement operations are complicated by infection. Thirty percent of these infections are due to S.aureus, which is often difficult to treat because of antibiotic resistance. As treatment of these infections is challenging, prevention with a vaccine is a very attractive option.

Method: To infect a joint replacement, bacteria must first adhere to its surface. This adherence is mediated by specific adhesion proteins; the expression of which is controlled by virulence regulator genes within the bacterial cell. A DNA vaccine is being developed which targets this regulatory apparatus, thus preventing bacterial adhesion, allowing the immune system to rapidly clear any potential S.aureus infection.

Results: Mutations of the agr,sar and sae virulence regulator genes have been made. Their properties have been explored using a flow cell system, which uses a scanning confocal laser microscope and image analysis software to accurately provide quantitative data in real-time of biofilm formation. We have shown that the sae mutant does not form biofilm in the same was as wild-type S.aureus. We have also shown that it does not adhere to steel as well as its wild-type counterpart.

Conclusion: For such a dramatic difference in biofilm forming properties to be evident, there must be a difference in the adhesion proteins produced by the wild-type and the mutant bacteria. Gel-electrophoresis has compared protein expression of sae mutant and wild-type bacteria and identified differences. Those proteins which are not expressed in the non-biofilm-forming mutant are sequenced and from the protein sequences, DNA sequences are identified that will form part of the candidate DNA vaccine.