Microbial ecology of Propionibacterium acnes in patients undergoing treatment with isotretinoin

Ryan-Kewley, Angela E. (2011) Microbial ecology of Propionibacterium acnes in patients undergoing treatment with isotretinoin. PhD thesis, University of Lincoln.

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Item Type:Thesis (PhD)
Item Status:Live Archive


Following failure to respond to antibiotic therapy, 56 patients (mean age 22yrs; range 15-46yrs) with recorded active Acne vulgaris were treated with a standard course of isotretinoin (1mg/kg body weight for 16 weeks).

This study investigated the recovery and analysis of skin surface organisms from several skin sites at the start of treatment, 8 weeks into treatment, at the end of the course and 1 month post treatment.

The number of anaerobic isolates - presumptive Propionibacterium acnes and also aerobic isolates recovered by appropriate media from each of three specific sites per patient were compared with age-matched controls of healthy volunteers. Patients and controls exhibited similar total numbers of organisms on the cheek, nares and toe web before treatment. Following treatment with isotretinoin the majority of patients had a significant reduction in bacterial numbers (1-2 orders of magnitude) on the cheek. Numbers in the nares and toe web did not show this reduction. Isotretinoin has no antibacterial activity in vitro or in vivo so the observed reduction would strongly suggest that the effect is mediated through alteration of the skin nutritional micro-environment.

The clinic-based patients demonstrated high levels of isolates with antibiotic resistance from the outset; the resistance status of each patients’ skin microbiota was determined before, during and after treatment and the dynamics of the population from these sites was investigated.

Previous studies of the nature of skin organisms and of the complex multifactorial mechanisms that lead to the eruption of acne have shown that P. acnes play a significant but as yet poorly explained role in the pathogenesis of the disease although it is traditionally the target organism for anti-acne therapy.

The clinical samples were cultured using conventional methods to confirm the presence of P. acnes and staphylococci. Novel modifications of PCR amplification methodology were developed to enhance the detection of specific organisms. New protocols for comprehensive and detailed RAPD-PCR analysis of whole cell PCR were developed and employed to profile recovered isolates from individual patients before and after clinical treatment.

RAPD-PCR proved to be a useful tool to survey changing bacterial profiles within the cohort. Isolates from some patients were highly similar to each other at the outset, but displayed increased diversity by the end of therapy. Interestingly, other studies have linked clonal populations of bacteria with high pathogenicity.

Some patients appear to have acquired a strain which was not evident at their original sampling, but was present in other patients attending the same clinic. P. acnes persist in the environment and may be found on many inanimate objects, from where they could become a source for transmission. As there is some evidence of acquisition of strains from the environment, this is of considerable significance to the management of dermatology clinics throughout the country.

Keywords:Acne, acne vulgaris
Subjects:C Biological Sciences > C180 Ecology
C Biological Sciences > C440 Molecular Genetics
C Biological Sciences > C500 Microbiology
Divisions:College of Science > School of Life Sciences
ID Code:6073
Deposited On:24 Aug 2012 13:19

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