Propionibacterium acnes: Current Researches
1. Classification
Domain: Bacteria Phylum: Actinobacteria Class: Actinobacteria Order: Actinomycetales Family: propionibacteriaceae Species: propionibacterium acnes
2. Description and significance
Propionibacterium acnes is a non-pathogenic, commensal bacterium that can be found in various locations of the body and in food such as dairy and cheese. P. acnes is a Gram-positive anaerobic bacillus that is slow-growing in nature, requiring a minimum of 6 days of culture growth (2). While P. acnes is most commonly associated with the inflammatory skin infection acne vulgaris, a skin condition commonly known as acne, research studies have demonstrated that it also plays a significant role in many other diseases such as in the lungs and lymph nodes and delayed surgical and implantation infections (3). However, due to its slow growth, P. acnes continues to be an under-recognized cause of diseases other than acne vulgaris and failure to diagnose can lead to serious consequences including mortality (3). Because of P. acnes’ broad association with a variety of disease, treatment options can vary. In most cases, P. acnes is susceptible to antibiotics or through a combination of either antibiotics and/or surgical option (3,4). Although a wide variety of research has been conducted on P. acnes, many questions are unanswered such as its symbiotic relationship in humans, and its antibiotic resistance role. Future research interest includes expanding on treatment options, novel diagnoses criteria specific to P. acnes in relation to different diseases, and its role as a disease-causing agent to further prevent infections and morbidity.
3. Genome structure
P. acnes stores its genetic information in a single circular chromosome. The chromosome encodes for approximately 2333 genes, with a 60% guanine-cytosine nucleotide ratio, containing various enzymes and proteins (6). For instance, P. acnes’ genes code for the Christie-Atkins-Munch-Petersen (CAMP) factors that act as toxins creating pores and allowing entry in the host’s membranes. The CAMP factors, along with enzymes that degrade body tissues, can ultimately lead to tissue inflammation. Moreover, the genome of P. acnes also encodes for proteins such as adhesins, heat shock proteins, and those that contribute in the formation of biofilms (6).
4. Cell structure and Metabolic Processes
P. acnes is a Gram-positive, non-spore forming, bacillus, or rod-like, bacterium. As a bacillus, P. acnes can be found living as individuals or in chains. In addition, as an aerotolerant anaerobic bacterium, the bacterium does not utilize oxygen for electron source, but is able to tolerate the presence of oxygen in the environment (3,4). Since P. acnes is an anaerobic microorganism, it can perform metabolic processes such as Embden-Meyerhof pathway and the pentose phosphate pathway, which allows for metabolization of sugars such as glucose, ribose, and mannose (5). Through the process of fermentation, P. acnes can also utilize lactose to produce propionic acid (4).
6. Ecology and Biofilm
P. acnes is a commensal bacterium found dominantly on the human skin at an optimal temperature of 37°C, particularly within the lipid-rich sebaceous skins and glands (6). These sebaceous sites are located along the neck, head, shoulders, and the armpit areas. P. acnes can also inhabit within the respiratory and intestinal tract as well as the auditory canal (3). Furthermore, along the skins and through the formation of biofilms, P. acnes can be found living in micro-colonies with other cutaneous adhering bacteria such as Staphylococcus, Streptococcus, and Pseudomonas (4). To synthesize biofilms, P. acnes performs quorum sensing to search for nutrient rich surfaces and other skin bacteria before secreting extracellular polysaccharides to form micro-colonies. Through biofilm formation, P. acnes plays a critical role as an opportunistic bacterium in causing implant-associated infections such as orthopedic implants, breast implants, and cerebrovascular and cardiovascular devices (4). In addition to protecting the bacterium from phagocytosis by macrophages, biofilms also allow for horizontal gene transfer, or the transferring of genetic information between different bacterial species, which can lead to increase in antimicrobial agent resistance (3, 6).
7. Pathology
Although P. acnes is considered a low virulent commensal bacterium, there are still some infections associated with the bacterium. Due to horizontal gene transfer inside biofilms, P. acnes can transform from being a commensal bacterium to an opportunistic bacterium. Thus, the pathogenicity of P. acnes as an opportunistic bacterium can be seen in cases such as endocarditis, sarcoidosis, and in joint infections among patients who underwent shoulder surgeries (6). Nevertheless, P. acnes cannot be confirmed as the primary source of inflammation because even when antimicrobial treatments were used to reduce the growth and concentration of P. acnes, recurrence of inflammation was still seen (4).
7. Key microorganisms
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8. Current Research
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9. References
It is required that you add at least five primary research articles (in same format as the sample reference below) that corresponds to the info that you added to this page. [Sample reference] Faller, A., and Schleifer, K. "Modified Oxidase and Benzidine Tests for Separation of Staphylococci from Micrococci". Journal of Clinical Microbiology. 1981. Volume 13. p. 1031-1035.
