Acne and propionibacterium acnes
Section snippets
Characteristics of cutaneous propionibacteria
The cutaneous propionibacteria (P. acnes, P. avidum, P. granulosum, P. propionicum, and P. lymphophilum) are found as commensals on human skin and other keratinized epithelia. Over the years, they have been variously classified as Bacillus spp, Corynebacterium spp, anaerobic diphtheroids, and Propionibacterium spp, and this must be borne in mind when surveying the literature. They are gram-positive and nonmotile, and when first isolated exhibit a typical coryneform appearance under the
The microflora of human skin
As a habitat for microorganisms, the human skin is open to contamination by microbial species from the environment, and yet it is not particularly suitable for colonization due to the environmental conditions resulting from its physical structure. Normal skin supports colonization by a limited number of resident microbial types, mainly gram-positive species able to tolerate the stresses associated with the physical environment. The stable microbial ecosystem is controlled partly by the physical
Control of microbial colonization of the skin
Physical factors controlling colonization are mainly functions of the skin structure and include the number and size of follicles and glands, gland function (eg, sebum, sweat, apocrine), the flow of secretions (which determines nutrient availability and hydration levels), the integrity of barrier function, skin pH, and osmotic potential. Biochemical analysis of the skin surface environment has revealed a vast array of chemical compounds derived from sebum, sweat, and the metabolic activity of
Classification and identification
Although much of the literature refers to P. acnes as an anaerobe, the cutaneous propionibacteria are not strictly anaerobic, and, although anaerobic conditions are used for primary isolation, all species will tolerate the presence of oxygen.15 After incubation on agar growth media, the colonies are characteristically dome-shaped and beige to pink in color. Because of the limited range of species found on human skin, most isolates can be speciated using a limited number of biochemical tests (
Epidemiology
The link between P. acnes and the development of acne is generally regarded as fact by most dermatologists and has by and large even become accepted by the general public through advertising for acne products. However, there is no formal proof linking P. acnes with acne, and the presence of propionibacteria is not a prerequisite for the development of acne.17 If P. acnes is involved in acne, whether its presence initiates certain features of the disease, such as inflammation, or whether it
Antibiotics and propionibacteria
The hypothesis that microorganisms are involved in acne is supported in part by the successful treatment of acne with antibiotics, such as erythromycin and clindamycin, and the reduced efficacy of these treatments when antibiotic-resistant propionibacteria are present.19 Although propionibacteria are susceptible to a range of other antibiotics, including penicillins and cephalosporins,20 the antibiotics of therapeutic value in acne are generally limited to lipid-soluble compounds. Extensive use
Future directions
A key objective for research is to define in detail the interactions of P. acnes with human skin in both normal and acne states. Most likely, this will be achieved by developing living skin equivalent model systems colonized by P. acnes. Further progress will be possible once the genomic sequence of P. acnes has been elucidated; then the interaction between skin and P. acnes will be open to transcriptional analysis using DNA microarray technology.
References (27)
- et al.
Quantification of bacteria in isolated pilosebaceous follicles in normal skin
J Invest Dermatol
(1975) - et al.
Age-related changes in the resident bacterial flora of the human face
J Invest Dermatol
(1975) - et al.
Expression of natural peptide antibiotics in human skin
Lancet
(1997) - et al.
The microbial ecology of pilosebaceous units isolated from human skin
J Gen Microbiol
(1984) - et al.
Regional variations of cutaneous propionibacteria
Appl Environ Microbiol
(1978) - et al.
Transfer of Propionibacterium innocuum Pitcher and Collins 1991 to Propioniferax gen nov as Propioniferax innocua comb nov
Int J Syst Bacteriol
(1994) - et al.
Microbial interactions on the skin
- et al.
Inhibitors produced by propionibacteria and their possible roles in the ecology of skin bacteria
Proc R Soc Edinburgh (Biol)
(1980) - et al.
The role of bacteria in acne vulgarisa new approach
Clin Exp Dermatol
(1978) - et al.
The microbiology of acnea review
J Appl Bacteriol
(1981)