Pilot Study- Comparing two surgical preparations Chlorhexidine 2% and Chlorhexidine 2% with Benzyol peroxide 5% for reduction of Propionobacterium acnes in the shoulder region.

Participants who choose to enrol in the study will be scheduled a time to come into hospital to a theatre room. The participant is required to complete a health questionnaire and is allocated a research number. This number will be used to label and track swabs without identifying the participant. The participant is then prepared in the same manner as for shoulder joint surgery. Each shoulder region of the participant is assigned a different preparation/treatment through a randomisation process. The intervention is the Bezoyl peroxide 5% followed by Chlorhexidine 2%. The comparison is two applications of Chlorhexidine 2%. One swab will be taken from each anterior deltoid and central axilla. This is done by drawing a line from the corocoid process to the axillary fold. The anterior deltoid swab is taken from the midpoint of this line and the axillary swab from the axillary end of the line. A 5x5 cm area of skin at each site for sampling (two per shoulder) is marked out. The pre skin prep swab is taken using a standard bacterial swab with Amies transport medium without charcoal. Care is taken to avoid anything touching the tip or lower shaft of the swab, the swab is moistened in the transport medium and then swabbed over the marked area of skin. This will be done by rolling the swab horizontally in a zig-zag motion from the top left hand corner of the marked area downwards and then covering the same area again by going in the reverse direction. Downward pressure should be applied to the swab whilst rolling. The swab is then placed in the transport medium and labelled with the appropriate blinded study number. The shoulder region in the interventional group will then be prepped with Bezoyl peroxide wash 5%. This is left to dry for two minutes, then Chlorhexidine 2% is applied over top and left to dry for a further two minutes. The comparison group will be prepared with two applications of Chlorhexidine 2% two minutes apart. Once the preparation has dried in both groups repeat swabs are to be taken from the above outlined anterior deltoid and central axillar areas in the same manner as described above. The swabs are then sent to the laboratory for processing as soon as possible. All initial swab processing is performed in the class II biosafety cabinet taking care not to touch the swab tip or shaft. The swab is plated onto a Columbia Heavy Fill Blood Agar plate in the standard semi-quantitative fashion, using the swab to create a primary inoculum over the lower ¼ of the plate ensuring that all sides of the swab have been inoculated. The primary inoculum is then streaked out using a disposable plastic loop in the standard fashion using 3 streak lines. The loop should be turned over between each streak using a fresh side of the loop. The plate is labelled with the appropriate blinded study number and the date of processing. Plates are then placed into an airtight container with an anaerobic gas pack along with an anaerobic indicator strip. The container is then to be placed into an incubator at 35-37C. Plates will be read at 7 days, where the anaerobic indicator strip checked and result recorded. Suspect colonies will be confirmed by MALDI-TOF MS as P. acnes. P. acnes colonies are quantified using the standard scanty, light, moderate, heavy scoring system. If no growth at 7 days, plates are re-incubated in same conditions for a further 7 days and then read in the same way.