Propionibacterium acnes

Acne is a disease related to the skin that affects almost 80 percent of adolescents and young adults. Propionibacterium acnes are bacterium known as the responsible for the development of acne. This bacterium is usually found in the pilosebaceous follicle (Figure 1). However, there is an obstacle to confirm that in fact P. acne is the responsible for cause acne. There is a difficulty in applying Koch’s postulates to the disease. In order word, it is an issue to isolating in pure culture these bacteria. For example, P. acne can be isolated from both acne and normal skin, which makes harder to identify and determine the role of this pathogen.

Figure 1. Normal pilosebaceous follicle. Notice the presence of the sebum which is secreted by the sebaceous gland. Source: http://www.niams.nih.gov

Characteristics of P. acne

These microorganisms are tolerant, anaerobic, gram-positive, commensal and nonmotile bacteria found in skin sites with high numbers of follicles secretors of sebum, including face, chest, and thorax. Considering the fact that our skin is constantly exposed to extreme conditions such as solar radiation, fluctuation of temperature, and deficit of water, the gram-positive cell wall (Figure 2) is an important advanced for these microorganisms. The cell wall provides them high structural stability and protection against the physical factors of the skin, which are responsible for the control of the bacteria colonization. The control of the growth of bacterium in the skin is due physical factors such as number and functions of follicles and glands, secretions, pH, and equilibrium of substance concentrations. For example, a secretion by the sweat glands, dermicidin, is active against gran-positive and negative bacterium. Another characteristic of these bacterial is that they are chemoorganotrophs, which means that their energy production is basically realized by the oxidation of organic nutrients found in the skin environment. Finally, these bacteria can performed fermentation metabolism. 

Figure 2. The gram positive cell envelope. Notice the dense layer of peptidoglycan and teichoic acids. Source: http://deltabiology.com

Epidemiology

Even if the uncertainty about the relationship between P. acne and acne disease, it is known that the presence of these microorganisms initiates the process of inflammation, which is one of the main symptoms of acne. In addition, the development of the other symptoms such as chronic inflammation (Figure 3), ductal hypercornification, and excessive sebum production are also known as a result of microbial action. Finally, the successful treatment of acne by using antibiotics such as erythromycin and clindamycin is another support to the hypothesis that microorganisms are involved in the development of acne.

Figure 3. Chronic inflammation of the skin of a teenager. Source: http://dermnetnz.org

These huge nodules are resulted first from small lesions called microcomedo, which are result from the increase in the secretion of sebum and the uncontrolled proliferation of keratinocytes. After, the continuous accumulation of sebum and keratinocytes, as well as the increase of the follicle cause the formation of comedones. Finally, the presence of colonies of P. acnes in the normal skin leads to an immune response which results in the process of inflammation of the comedones to a nodule (Figure 4).

Figure 4. Cycle of acne lesion. Note the pathway of the immune response that result in the process of inflammation. Diagram created by the student Jailson Santos, 2014.

Curiosity

Propionibacterium has an economic importance which is resulted from the participation of this bacterium in the industry of cheese. In other words, Propionibacterium is involved in the production of the Swiss cheese whose flavor derives from propionate, a product of fermentation which is a metabolism pathway performed by the bacterium.

References

Bojar, R. A., Holland, K. T. (2004). Acne and Propionibacterium Acnes. Elsevier, Clinics in Dermatology, 22:375–379.

Levy, P., Fenollar, F., Stein, A., Borrione, F., Cohen, E., Lebail, B., & Raoult, D. (2008). Propionibacterium acnes Postoperative Shoulder Arthritis: An Emerging Clinical Entity. Clinical Infectious Diseases, (12). 1884.

Schaeverbeke, T., Lequen, L., Barbeyrac, B., Labbe, L., Bebear, C. M., Morrter, Y., Bannwarth, B., Bebear, C., Dehats, J. (1998). Propionibacterium Acnes Isolated from Synovial Tissue Fluid in a Patient with Oligoarthrttis Associated with Acne and Pulstulosis. Arthritis and Rheumatisms. Vol. 41, No. 10. Octohcr 1998. pp 1889-1893

TANGHETTI, E. A. (2013). The Role of Inflammation in the Pathology of Acne. Journal of Clinical & Aesthetic Dermatology, 6(9), 27-35.