***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: BACKGROUND Propionibacterium acnes is a gram-positive anaerobe that can lead to devastating postoperative shoulder infections . The objective of this study was to investigate whether a benzoyl peroxide and clindamycin preoperative skin preparation reduces the incidence of P. acnes colonization during shoulder arthroscopy . METHODS Sixty-five shoulder arthroscopy patients were prospect ively enrolled . A skin culture specimen was taken at the preoperative visit from st and ard arthroscopic portal sites . Topical benzoyl peroxide 5 % and clindamycin 1.2 % ( BPO/C ) gel was applied to the shoulder every night before surgery . Skin culture was repeated in the operating room before preparation with chlorhexidine gluconate . Shoulder arthroscopy proceeded , with final culture specimens obtained from within the shoulder . RESULTS P. acnes skin colonization remained similar to prior studies at 47.7 % ( 31 of 65 patients . ) With > 1 application , BPO/C was 78.9 % ( 15 of 19 patients ) effective in eliminating P. acnes superficial colonization . With 1 application , it was 66.7 % ( 8 of 12 patients ) effective in eliminating superficial colonization . Deep colonization was reduced to 3.1 % ( 2 of 65 patients ) compared with previous studies of 15 % to 20 % ( P = .006 ) . BPO/C was 100 % effective at decreasing deep colonization with > 1 application . CONCLUSIONS P. acnes skin colonization is high at arthroscopic shoulder portals , especially in men . Despite st and ard skin preparation and prophylactic antibiotics , the rate of joint inoculation is much higher than the rate of infection reported in the literature . BPO/C effectively reduces P. acnes colonization in shoulder arthroscopy . It should be considered for use before shoulder procedures with a time-related trend of > 1 application PURPOSE To examine the contamination rate of the anchor-suture and to determine the efficacy of 2 different surgical skin preparation solutions with or without a plastic adhesive drape from suture contamination in arthroscopic rotator cuff repair . METHODS A prospect i ve r and omized study was undertaken to evaluate 126 consecutive patients undergoing arthroscopic rotator cuff repair .  Each shoulder was prepared with one of 2 r and omly selected solutions according to an assigned envelope that indicated the procedure to be used : chlorhexidine-alcohol ( 1 % chlorhexidine gluconate and 70 % isopropyl alcohol ) or povidone-iodine . Then , each group was further divided according to the usage of a plastic drape . The first cut-tails of the anchor-suture after cuff fixation were su bmi tted to aerobic and anaerobic cultures . RESULTS The overall rate of Propionibacterium acnes-positive cultures was 47 % ( 14 of 31 cases ) in the povidone-iodine group , 33 % ( 11 of 33 cases ) in the povidone-iodine with a drape group , 33 % ( 10 of 30 cases ) in the chlorhexidine-alcohol group , and 9.3 % ( 3 of 32 cases ) in the chlorhexidine-alcohol with a drape group . The positive culture rate in the chlorhexidine-alcohol with a drape group was lower than that in the povidone-iodine group ( relative risk , 0.2 ; 95 % confidence interval : 0.064 - 0.63 ; number needed to treat , 2.7 ; P < .0001 ) . Coagulase-negative staphylococci were isolated in the povidone-iodine with a drape ( 1 case ) and chlorhexidine-alcohol with a drape group ( 2 cases ) . No other bacteria were isolated , and no infections occurred in any of the patients treated in this study during the minimum 12-month follow-up period . CONCLUSIONS Chlorhexidine-alcohol solution with an adhesive plastic drape was more effective than chlorhexidine-alcohol without a plastic drape and povidone-iodine with/without a plastic drape in eliminating P acnes suture contamination . However , the usage of a plastic drape slightly increased the risk of coagulase-negative Staphylococcus proliferation . LEVEL OF EVIDENCE Level I , therapeutic , prospect i ve , r and omized trial HYPOTHESIS Deep infection after shoulder surgery is a rare but devastating problem . This study tested the hypothesis that the home application of a 2 % chlorhexidine gluconate cloth before shoulder surgery would be more efficacious than a st and ard shower of soap and water at decreasing the preoperative cutaneous levels of pathogenic bacteria on the shoulder . MATERIAL S AND METHODS This r and omized , prospect i ve study evaluated 100 consecutive patients undergoing shoulder surgery . Patients were r and omly assigned to use 2 % chlorhexidine gluconate-impregnated cloths ( treatment group ) or to shower with soap and water before surgery ( control group ) . Cutaneous cultures were taken from the patients ' shoulders in the preoperative holding area . Patients were monitored for 2 months postoperatively for clinical signs of infection . RESULTS In the treatment group vs the control group , the overall positive culture rate was 66 % vs 94 % ( P = .0008 ) , and the positive culture rate for coagulase-negative Staphylococcus was 30 % vs 70 % ( P = .0001 ) . The positive culture rate for Propionibacterium acnes was 46 % in the treatment group vs 58 % in the control group ( P = .32 ) . No infections occurred in any patients at a minimum of 2-months after surgery . DISCUSSION The use of the 2 % chlorhexidine cloth was effective at decreasing overall bacterial culture rates before shoulder surgery and was particularly effective at decreasing the quantity of coagulase-negative Staphylococcus , a known causative agent of postoperative shoulder infections . CONCLUSION Use of chlorhexidine impregnated cloths prior to shoulder surgery may be a useful adjunct to presently used infection prevention strategies BACKGROUND : Benzoyl peroxide and clindamycin are the two most widely prescribed topical antimicrobials in the treatment of acne . AIM : To compare the antimicrobial efficacy , in vivo , of benzoyl peroxide and clindamycin against Propionibacterium acnes . METHODS : Two groups of 10 subjects each , with comparable mean P. acnes baseline counts of log 5.75 to 5.85 , underwent twice daily application of  benzoyl peroxide or clindamycin  for 14 days . RESULTS : The results of quantitatively sampling P. acnes after 3 , 7 and 14 days of treatment showed that TriazA 6 % benzoyl peroxide special gel produced faster and significantly greater reductions in P. acnes than did the 1 % clindamycin phosphate in Cleocin-TA lotion ( p < 0.01 ) . These results were paralleled by the greater reductions produced by Triaz versus Cleocin ( p < 0.05 ) in P. acnes fluorescence . CONCLUSION : Benzoyl peroxide formulations suppress the follicular population of P. acnes more rapidly and to a greater degree than topical antibiotics such as clindamycin BACKGROUND Propionibacterium acnes has arisen as the most common microorganism identified at the time of revision shoulder arthroplasty . There is limited evidence to suggest how frequently false-positive cultures occur . The purpose of this prospect i ve controlled study was to evaluate culture growth from specimens obtained during open shoulder surgery . METHODS Patients undergoing an open deltopectoral approach to the shoulder were prospect ively enrolled . Patients with a history of shoulder surgery or any concern for active or previous shoulder infection were excluded . Three pericapsular soft-tissue sample s were taken from the shoulder for bacterial culture and were incubated for fourteen days . A sterile sponge was also analyzed in parallel with the tissue cultures . In addition , similar cultures were obtained from patients who had undergone previous shoulder surgery . RESULTS Overall , 20.5 % of surgeries ( twenty-four of 117 ) yielded at least one specimen removed for culture that was positive for bacterial growth , and 13.0 % of sterile control specimens ( seven of fifty-four ) had positive culture growth ( p = 0.234 ) . P. acnes represented 83.0 % of all positive cultures ( thirty-nine of forty-seven ) at a median incubation time of fourteen days . Among the subjects who had not undergone previous surgery , 17.1 % ( fourteen of eighty-two ) had at least one positive P. acnes culture . Male sex was univariably associated with a greater likelihood of bacterial growth ( p < 0.01 ) , and patients who had not undergone previous surgery and had received two or more preoperative corticosteroid injections had a higher likelihood of bacterial growth ( p = 0.047 ) . CONCLUSIONS The clinical importance of positive P. acnes cultures from specimens obtained from open shoulder surgery remains uncertain . Male sex and preoperative corticosteroid injections were associated with a higher likelihood of bacterial growth on culture and are risk factors that merit further investigation . Previously reported incidences of positive P. acnes culture results from specimens from primary and revision shoulder arthroplasty may be overestimated because of a substantial level of culture contamination . CLINICAL RELEVANCE P. acnes is isolated via culture at a substantial rate from shoulders undergoing a deltopectoral approach . The clinical importance of culture growth by this low-virulence organism still remains uncertain . Further study is necessary to more specifically characterize culture growth by P. acnes as an infection , commensal presence , or contaminant PURPOSE To document the skin colonization and deep tissue inoculation rates associated with  arthroscopic shoulder surgery  and how these rates differ with procedural and demographic factors . METHODS We prospect ively recruited outpatient shoulder arthroscopy patients who agreed to participate and met the inclusion criteria from February 2013 to May 2014 . All patients received routine antibiotic prophylaxis intravenously . Initial cultures were obtained before the skin preparation by swabbing the skin at the 3 st and ard portal sites : posterior , anterosuperior , and anterolateral . The skin preparation used 4 % chlorhexidine scrub and 2 % chlorhexidine gluconate/70 % isopropyl alcohol paint applied to the entire shoulder . After completion of the arthroscopic procedure , a second culture was obtained through a cannula at the surgical site . All cultures were plated for 21 days using Brucella medium . RESULTS We enrolled 51 patients over a 15-month period . Cultures showed a 72.5 % Propionibacterium acnes superficial colonization rate : 46.1 % of female and 81.6 % of male patients ( P = .027 ) . We identified a deep culture-positive inoculation rate of 19.6 % , all with positive P acnes skin colonization . No correlation could be made concerning diagnosis , procedure , suture anchor use , age , or sex . CONCLUSIONS The rate of skin colonization with P acnes is high at arthroscopic portals , especially in men . Despite st and ard skin preparation and prophylactic antibiotics , the rate of deep tissue inoculation with P acnes in shoulder arthroscopy is much higher than the rate of infection reported in the literature . CLINICAL RELEVANCE Shoulder arthroscopy introduces a significant amount of P acnes into the deep tissues BACKGROUND To examine the rates and predictors of deep periprosthetic infections after  shoulder hemiarthroplasty .  METHODS We used prospect ively collected institutional registry data on all primary shoulder hemiarthroplasty patients from 1976 - 2008 . We estimated survival free of deep periprosthetic infections using Kaplan-Meier survival curves . Using univariate Cox regression analyses , we examined the association of patient-related factors ( age , sex , body mass index ) , comorbidity ( Deyo-Charlson index ) , American Society of Anesthesiologists grade , underlying diagnosis , and implant fixation with the risk of infection . RESULTS A total of 1,349 patients , with a mean age of 63 years ( SD , 16 years ) , 63 % of whom were women , underwent 1,431 primary shoulder hemiarthroplasties .  Mean follow-up was 8 years ( SD , 7 years ) . Fourteen deep periprosthetic infections occurred during the follow-up , confirmed by medical record review . The most common organisms were Staphylococcus aureus , coagulase-negative Staphylococcus , and Propionibacterium acnes , each accounting for 3 cases ( 21 % each ) . The 5- , 10- , and 20-year prosthetic infection-free rates were 98.9 % ( 95 % confidence interval [ CI ] , 98.3%-99.5 % ) , 98.7 % ( 95 % CI , 98.1%-99.4 % ) , and 98.7 % ( 95 % CI , 98.1%-99.4 % ) , respectively . None of the factors evaluated were significantly associated with risk of prosthetic infection after primary shoulder hemiarthroplasty , except that an underlying diagnosis of trauma was associated with a significantly higher hazard ratio of 3 
    Output:
    
The application of a topical benzoyl peroxide antibiotic in the days leading up to surgery in combination with preoperative antibiotic prophylaxis significantly reduces the prevalence of C acnes in shoulder arthroscopy patients