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Effect of photodynamic therapy on the microbiology of acne

Shaheen, Babar 2014. Effect of photodynamic therapy on the microbiology of acne. MD Thesis, Cardiff University.
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Light-based therapies, including photodynamic therapy (PDT), for acne are gaining popularity in dermatology. Based largely upon in vitro data, their beneficial outcome in acne is thought to be related to their bactericidal effects on Propionibacterium acnes. This randomised controlled study sought to determine the efficacy and tolerability of 610-950 nm IPL (administered as IPL-Placebo) and IPL-assisted methyl aminolaevulinate PDT (IPL-MAL) vs. adapalene 0.1% gel in the treatment of acne and to identify their mode of action, looking specifically at the effect on surface density of P. acnes. Thirty seven patients (31% of target due to slow recruitment) with mild to moderate facial acne were randomly allocated to IPL-MAL treatment, IPL-Placebo or adapalene. Both IPL groups received four treatments to the whole face, 2 weeks apart, while the third group was given adapalene nightly for 12 weeks. Assessments performed at baseline and weeks 8, 11, and 16 included inflamed, noninflamed and total lesion counts, Leeds grading, follicular porphyrin fluorescence, the Family Dermatology Life Quality Index and Dermatology Life Quality Index scores, and patient’s perspective of clinical improvement by the visual analogue scale (VAS). Cutaneous microflora was collected from all patients at similar intervals. Of the 37 patients randomised, only 30 completed the trial (10 in each group) and were included in the final analyses. Adapalene was found to be significantly superior to IPL-MAL and IPL-Placebo in reducing the noninflamed (adapalene 37.6% vs. IPL-MAL 3.4% vs. IPL-Placebo −9.7%) and total lesion counts (adapalene 35.7% vs. IPL-MAL 4.3% vs. IPL-Placebo −8.4%) at week 16. This was accompanied by a significant decrease (52.9%) in the DLQI score in this group (p = 0.031). The maximum improvement in inflamed lesion counts from baseline was seen at week 11 in the IPL-MAL (20.7%) and IPL-Placebo (13.4%) groups but occurred at week 16 in the adapalene group (26.5%). Statistical significance, however, was not reached in any group. There was no significant difference within or between the groups in the VAS, Leeds, FDLQI and porphyrin fluorescence results pre- and post- treatment. A significant increase in the density of propionibacteria (p = 0.021) and xxi coagulase-negative staphylococci (p = 0.039) was seen in the IPL-Placebo and IPL- MAL groups at week 16 and week 8, respectively; however, there was no significant difference between the groups. All the treatments were well tolerated. Adapalene remains an effective first line treatment in mild to moderate facial acne. However, the present study has remained indecisive (due to being underpowered) in drawing any firm conclusions regarding the efficacy of IPL and IPL-MAL on inflamed acne lesions. Further research is therefore warranted before their use can be advocated for acne treatment. An alternative mode of action for IPL and IPL-assisted MAL-PDT other than photodynamic destruction of P. acnes is suggested from the results of this study.

Item Type: Thesis (MD)
Status: Unpublished
Schools: Medicine
Subjects: R Medicine > RL Dermatology
Last Modified: 19 Mar 2016 23:52

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