Monday, June 26, 2017

Propionibacterium, benzoyl peroxide and clindamycin

Benzoyl peroxide and clindamycin topical skin preparation decreases Propionibacterium acnes colonization in shoulder arthroscopy

These authors enrolled 65 patients  in a study to investigate whether a benzoyl peroxide and clindamycin preoperative skin preparation reduces the incidence of P. acnes colonization in shoulder arthroscopy. A skin culture specimen was taken at the preoperative visit from standard 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. Final cultures were obtained from within the shoulder after the arthroscopic procedure.

All culture specimens were plated for a full 21 days on Brucella blood agar medium and reported to 21 days.

Initial culture specimens taken before treatment with topical BPO/C were positive for P. acnes in 31 of 65 patients (47.7%). Men (80.6%, 25 of 31 patients) were more often colonized than women (19.4%, 6 of 31 patients) (P = .001).

With 1 application of BPO/C,  4 of 12 (33%) patients were culture positive in the OR prior to skin preparation with chlorhexidine gluconate. 

4 of 19 (21%) patients having >1 application of BPO/C were culture positive in the OR prior to skin preparation with chlorhexidine gluconate. 

The positivity  of the deep cultures were associated with the number of applications; 0% of patients with 2 or more applications had a positive deep culture. 

The two patients had a positive deep culture had fewer than 2 applications of BPO/C . Interestingly, 4 patients who initially had negative skin cultures for P. acnes demonstrated positive skin cultures after topical BPO/C was used. These patients all had negative deep cultures.

Clinical follow-up was documented for all 65 patients for a minimum of 3 months and mean of 6 months postoperatively. There were no signs or symptoms of a clinical infection. Patients with positive deep P. acnes cultures were provided oral antibiotic treatment with doxycycline 100 mg daily for 3 weeks. The topical skin preparation was safe, with only 1 skin reaction (1.5% of patients.) There was no erythema or desquamation in this patient but rather a mild dermatitis. The reaction resolved promptly without treatment, and surgical timing did not need to be altered.

In a prior study, these authors reported on the prevalence of deep colonization of P. acnes in patients undergoing shoulder arthroscopy finding a 72.5% superficial culture rate and 19.6% deep inoculation rate. All positive deep cultures had positive superficial skin cultures.

Comment:  In their discussion, the authors state that "benzoyl peroxide is a powerful topical antimicrobial agent destroying both surface and ductal bacterial organisms and yeasts. Its lipophilic properties permit penetration of the pilosebaceous duct. Once applied to the skin, benzoyl peroxide decomposes to release free oxygen radicals, which have potent bactericidal activity in the sebaceous follicles and an antiinflammatory action. Treatment with BPO/C has demonstrated the added benefit of inhibiting the emergence of antibioticresistant strains of P. acnes."

There may be a downside to the use of BPO/C; the authors point out that "The application of the antibiotic gel in our study revealed positive skin cultures for P. acnes in 3 patients who initially had negative skin cultures. This may be secondary to the dual functions that benzoyl peroxide possesses. Benzoyl peroxide is a direct topical bactericidal agent that is also lipophilic. It penetrates pilosebaceous follicles to break down to benzoic acid and hydrogen peroxide, which releases free oxygen radicals that can oxidize proteins in bacterial cell membranes. Benzoyl peroxide is also known to act as a comedolytic and it is likely that this chemical exfoliating action on the epidermal layer of skin exposes the pathogen for culture."

This study would have been stronger if concurrent rather than historical controls were used (note the apparent difference in superficial culture results for the historical controls (72.5%) vs 47.7% in this study. "Because of changes in contracts, the laboratory used for the cultures had to be changed midway through the study for 16 patients. The second laboratory had a lower overall P. acnes –positive superficial culture incidence (6.3%) than expected from previous studies."

Nevertheless, the article is of interest in its proposal of a prophylactic regimen with BPO/C  as well as a proposal for using post operative doxclyline for patients with positive deep cultures (although these culture results were not finalized until 3 weeks after surgery so it appears that the antibiotics would not be started until these results were known). 

We are left with the thought that some patients may benefit from BPO/C prophylaxis before shoulder surgery. The questions that remain are (1) which patients are appropriate for BPO/C  treatment? (2) how many BPO/C  treatments are indicated? (3) if a patient has a skin reaction to BPO/C, how should that affect proceeding with elective surgery and  (4) when cultures are obtained before and at surgery, how should the results of these cultures inform the use of extraordinary antibiotic prophylaxis? 

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