Propionibacterium acnes

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Propionibacterium acnes
Propionibacterium acnes.jpg

Propionibacterium acnes

Systematics
Department : Actinobacteria
Class : Actinobacteria
Order : Actinomycetales
Family : Propionibacteriaceae
Genre : Propionibacteria ( Propionibacterium )
Type : Propionibacterium acnes
Scientific name
Propionibacterium acnes
( Gilchrist 1900) Douglas & Gunter 1946

Propionibacterium acnes is a slowly growing, gram-positive , anaerobic bacterium. The bacterium is part of the skin flora and commensal , but is also involved as a secondary factor in the pathogenesis of acne . It was formerly known as Bacillus acnes and Corynebacterium acnes . About 100 strains of the species Propionibacterium acnes areknown, the genome of numerous strains has already been completely sequenced . Research into which strains are pathogenic and e.g. B. are involved in the disease Acne vulgaris , is currently (as of 2013) not yet completed.

features

Appearance

Propionibacterium acnes is a gram-positive short, rod-shaped bacterium; ellipsoidal cell shapes are also found. A single cell is 0.4-0.5  µm (microns) wide and 0.8-0.9 µm long. In the light microscope image , cells are usually found in pairs that are not directly behind one another, but at an angle. With further cell divisions, this leads to the formation of V- or Y-shaped chains. The bacterium has no flagella for active movement and cannot form persistent forms such as endospores .

Round colonies form after four to five days on solid nutrient media that are incubated under anaerobic conditions . Viewed from the side, the colonies are raised, they appear smooth and shiny, their diameter is 1.5–4.0 mm. The colonies are white, but after several days of incubation in the nutrient medium they show a slight color to pink.

Growth and metabolism

Propionibacterium acnes is an anaerobic bacterium. Similar to lactic acid bacteria , it is considered to be aerotolerant, which means that although it grows in the presence of oxygen , it does not need it for its metabolism. However, studies on the cultivation of the bacterium show that the presence of oxygen has an inhibitory effect on growth. It has the enzyme catalase and can form cytochromes . The optimal temperature for cultivation is around 37 ° C. At 45 ° C no more growth occurs, at room temperature (approx. 20 ° C) growth occurs only very slowly. The optimal pH value of the nutrient medium is in the neutral range, i.e. around pH 7.0. Even under optimal conditions, growth is rather slow; colonies can only be observed after 4–5 days.

Propionibacterium acnes operates a chemoorganotrophic and heterotrophic metabolism , it uses organic compounds as an energy source and also to build up cellular substances. It can utilize various substrates for energy production in one fermentation . Since a main product of this fermentation is propionic acid , this metabolic pathway is called propionic acid fermentation . Other products of this fermentation are acetic acid and carbon dioxide (CO 2 ). As substrates of can Propionibacterium acnes different carbohydrates are used, for example, glucose , fructose , mannose and galactose . Also some sugar alcohols , e.g. B. Glycerin (glycerol) can be recycled. Propionibacterium species can usually also use lactate - the anion of lactic acid - as a substrate for propionic acid fermentation. This does not apply to Propionibacterium acnes .

Some enzymes that are used in the metabolism to break down certain substrates are detected as part of a " colorful series " in order to identify a bacterium. Propionibacterium acnes has catalase and also proteolytic enzymes with which it can break down gelatin , this is also known as gelatin liquefaction. The nitrate reductase enzyme (NADH) ( EC 1.7.1.1) is used to reduce nitrate . The formation of indole from tryptophan is not carried out by all strains, so the result of the indole test can be positive or negative. Beta hemolysis can be observed on culture media that contain an addition of blood (a so-called blood agar ) . However, this behavior is not typical for all tribes. Studies from 2010 show that strains assigned to group I in particular show the ability to hemolysis, while other strains do not.

genetics

The genome of numerous strains of the bacterium has already been completely sequenced . The first sequencing took place in 2004 on Propionibacterium acnes KPA171202. The genome is 2560 kilobase pairs (kb) in size , which is about 55% of the genome size of Escherichia coli . The strain investigated ( DSM 16379) was isolated from human skin as a commensal and classified as pathogenic because it was involved in the disease acne vulgaris . In the years that followed, other strains were genetically examined, with similar results in terms of genome size. The bacterial strains examined also originated from human skin. In this context, strains were also examined which came from test persons who were not suffering from acne; these strains were consequently classified as non-pathogenic.

The results of the sequencing show a GC content (the proportion of the nucleobases guanine and cytosine ) in the bacterial DNA of about 60 mol percent. This lies within the range of 53 to 68 mol percent, which is typical for the genus Propionibacterium , the representatives are therefore counted to the phylogenetic group of gram-positive bacteria with a high GC content.

Pathogenicity

Propionibacterium acnes is  assigned to risk group 2 by the Biological Agents Ordinance in conjunction with the TRBA ( Technical Rules for Biological Agents) 466 . Microorganisms in this risk group are defined in the Biological Agents Ordinance as "biological agents that can cause illness in humans and pose a risk to employees [...]". However, it is counted as a commensal to the normal skin flora . On the skin it is not only a harmless resident, but is also a causative agent of acne or can contribute to this disease. Research into which strains are to be considered pathogenic and which virulence factors can be detected in the genome is still ongoing (as of 2013) and is described in more detail in the Systematics section .

proof

A nutrient medium must have numerous nutrients so that Propionibacterium acnes can be cultivated on it. Ingredients commonly used include meat extract , peptone from casein , yeast extract , dipotassium hydrogen phosphate (KH 2 PO 4 ), cysteine , hemins , and some vitamins . During the preparation of the medium, inoculation and incubation, strict adherence to the anaerobic technique must be observed. It is incubated at a temperature of 37 ° C. Other recommended additives in the medium are glucose and thioglycolate .

Occurrence

The bacterium is part of the skin flora and commensal. Propionibacterium acnes lives primarily in the sebum of the hair follicle , but has also been found in the digestive tract . Up to 100,000 bacteria of this type can be isolated from one cm 2 of human skin.

Systematics

Phylogenetic tree of 57 sequence types from 210 isolates of Propionibacterium acnes .

Propionibacterium acnes is one of several species in the genus Propionibacterium . About 100 strains of bacteria are known of this species. Numerous strains of this can be detected on human skin without causing the disease acne vulgaris . On the other hand, there are increased numbers of these bacteria in patients with acne vulgaris . Studies on these pathogenic strains show that they trigger the production of cytokines and chemokines in the cells of the sebum glands (sebocytes) and thus contribute to an inflammatory process.

Serological tests on the various strains led to these being divided into groups, depending on whether and which factors were detectable. Groups I to III were identified and two subgroups IA (I-1) and IB (I-2). This division, based on phenotypic characteristics, is based on the distinction between the polysaccharide chains present in the bacterial cell wall and was supplemented by studies in which bacteriophages attach to cells in a host-specific manner ( lysotype ). This division into phenotypic groups was later followed by genetic studies. Since 2010, genetic testing has been carried out using a multi- locus sequence analysis (MLSA), in which only certain genes are examined. This sequence analysis was restricted to the detection of nine housekeeping genes (English housekeeping genes , non-regulated genes regardless of cell type, cell stage and external influences expressed are) and two genes (tly and camp5), which presumably encode virulence factors. The study includes 210 isolates of Propionibacterium acnes from patients with acne, patients with other infections in which it is involved, and from healthy people in whom it is part of the normal skin flora. As a result of the MLSA, the 210 isolates can be assigned to 57 sequence types, i.e. 57 different populations , with each sequence type showing the same result in the multi-locus sequence analysis.

With the help of this data from the MLSA, a phylogenetic tree can be created that confirms the division into the groups mentioned (see figure). Within a group of the family tree, the sequence types have a similar composition of the genes examined. If one compares the affiliation of the isolates with the patient's medical history, one finds the majority of the isolates from patients with severe acne (marked with a black point in the figure) in subgroup I-1. Only a few isolates are found in subgroup I-2 or group II and not a single one in group III. In contrast, isolates that are involved in other infections (marked with a red circle in the figure) belong to subgroup 1–2 or groups II and II rather than acne-associated subgroup I-1. These isolates come from blood , cerebrospinal fluid (CSF, Liquor cerebrospinalis ) and post-operative infections of the hip joints . In these cases it is assumed that an opportunistic infection with Propionibacterium acnes is present.

It is therefore likely that only a limited number of sequence types - and thus a limited number of bacterial strains - of Propionibacterium acnes are to be classified as pathogenic with regard to the disease acne vulgaris and that these strains are very closely related to one another. A database has been set up for further MLSA examinations, in which the results of all examinations carried out so far can be compared. The study on 285 isolates, which was completed in 2012, confirms the assumption that there is a kind of " lineage " of the pathogenic strains.

etymology

The generic name refers to the production of propionic acid in the fermentation of the same name, the species name to the involvement in the disease acne. Propionibacterium acnes was first described as Bacillus acnes in 1900 by John Dow Fisher Gilchrist . By David Hendricks Bergey et al. a. it was assigned to the genus Corynebacterium in 1923 . The investigations by Howard C. Douglas and Shirley E. Günter in 1946 led to the fact that it was placed in the genus Propionibacterium , mainly due to the evidence of propionic acid fermentation and anaerobic growth.

Medical importance

Acne vulgaris in a 14 year old boy

Propionibacterium acnes is involved as a secondary factor in the pathogenesis of acne and is particularly associated with acne vulgaris . It can multiply in the comedones because the conditions there tend to be anaerobic. It is in the sebum of the hair follicle , especially the sebaceous follicles to find. Since it has the enzyme lipase , it can break down components of the sebum of the sebum glands to produce energy and thus multiply. The resulting inflammation-promoting substances cause the accumulation of leukocytes in the tissue through chemotaxis , and when they die, pustules filled with pus develop, a symptom of acne.

In addition, P. acnes has been linked to cases of keratitis and sarcoid . As part of medical treatments, infections can occur postoperatively or after the use of equipment. Cases of discitis, spondylodiscitis , infections of the central nervous system, endocarditis , osteomyelitis , endophthalmitis and joint infections are documented. Circulating immune complexes, which were formed against Propionibacterium acnes antigen, are deposited on bones or joints and there cause an immune reaction, are suspected as the cause of the rheumatic symptoms in the context of SAPHO syndrome .

Individual evidence

  1. ↑ a b c d e f g h i j H. C. Douglas, SE Gunter: The taxonomic position of Corynebacterium acnes. In: Journal of bacteriology. Volume 52, July 1946, pp. 15-23, ISSN  0021-9193 . PMID 20994865 .
  2. ↑ a b Gunther Müller: Fundamentals of food microbiology . 6th edition. Steinkopff Verlag, Darmstadt 1986, ISBN 3-7985-0673-6 , p. 62 .
  3. ↑ a b c d e f Michael T. Madigan, John M. Martinko, Jack Parker: Brock Mikrobiologie. German translation edited by Werner Goebel. 1st edition. Spektrum Akademischer Verlag, Heidelberg / Berlin 2000, ISBN 3-8274-0566-1 , pp. 572-574, 578, 693, 866-867.
  4. ↑ a b c d H. B. Lomholt, M. Kilian: Population genetic analysis of Propionibacterium acnes identifies a subpopulation and epidemic clones associated with acne. In: PloS one. Volume 5, number 8, 2010, p. E12277, ISSN  1932-6203 . doi: 10.1371 / journal.pone.0012277 . PMID 20808860 . PMC 2924382 (free full text).
  5. ↑ a b H. Brüggemann, A. Henne et al .: The complete genome sequence of Propionibacterium acnes, a commensal of human skin. In: Science. Volume 305, Number 5684, July 2004, pp. 671-673, ISSN  1095-9203 . doi: 10.1126 / science.1100330 . PMID 15286373 .
  6. ↑ a b c Propionibacterium acnes KPA171202. In: Website Genomes Online Database (GOLD) . Retrieved November 17, 2013 .
  7. ↑ a b c J. Hunyadkürti, Z. Feltóti et al.: Complete genome sequence of Propionibacterium acnes type IB strain 6609. In: Journal of bacteriology. Volume 193, Number 17, September 2011, pp. 4561-4562, ISSN  1098-5530 . doi: 10.1128 / JB.05372-11 . PMID 21705602 . PMC 3165515 (free full text).
  8. ↑ Propionibacterium acnes 6609. In: Website Genomes Online Database (GOLD) . Retrieved November 17, 2013 .
  9. ↑ TRBA (Technical Rules for Biological Agents) 466: Classification of prokaryotes (Bacteria and Archaea) into risk groups. In: Website of the Federal Institute for Occupational Safety and Health (BAuA). April 25, 2012. Retrieved November 17, 2013 .
  10. ^ Text of the Biological Agents Ordinance - BioStoffV (2013) at juris. Retrieved November 17, 2013.
  11. ↑ Catalog of microorganisms. In: Website of the Leibniz Institute DSMZ - German Collection of Microorganisms and Cell Cultures GmbH . Retrieved November 17, 2013 .
  12. ↑ Sajeev Handa: Propionibacterium Infections. In: MedScape website . Burke A. Cunha, June 13, 2012, accessed November 17, 2013 .
  13. ↑ a b Herbert Hof, Rüdiger Dörries: Dual Series: Medical Microbiology . 3. Edition. Thieme Verlag, Stuttgart 2005, ISBN 978-3-13-125313-2 , p. 305, 335-336 .
  14. ^ A b Jean Euzéby, Aidan C. Parte: Genus Propionibacterium. (No longer available online.) In: List of Prokaryotic names with Standing in Nomenclature ( LPSN ). Archived from the original on October 23, 2013 ; Retrieved November 17, 2013 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.bacterio.net
  15. ^ Taxonomy Browser Propionibacterium acnes. In: National Center for Biotechnology Information (NCBI) website . Retrieved November 17, 2013 .
  16. ↑ I. Nagy, A. Pivarcsi et al: Propionibacterium acnes and lipopolysaccharide induce the expression of antimicrobial peptides and proinflammatory cytokines / chemokines in human sebocytes. In: Microbes and infection / Institut Pasteur. Volume 8, Number 8, July 2006, pp. 2195-2205, ISSN  1286-4579 . doi: 10.1016 / j.micinf.2006.04.001 . PMID 16797202 .
  17. ↑ Propionibacterium acnes MLST Databases. In: Website of the Public databases for molecular typing and microbial genome diversity (PubMLST) . Anna Gao, Andrew McDowell, accessed November 17, 2013 .
  18. ↑ A. McDowell, E. Barnard et al .: An expanded multilocus sequence typing scheme for propionibacterium acnes: investigation of 'pathogenic', 'commensal' and antibiotic resistant strains. In: PloS one. Volume 7, number 7, 2012, p. E41480, ISSN  1932-6203 . doi: 10.1371 / journal.pone.0041480 . PMID 22859988 . PMC 3408437 (free full text).
  19. ↑ JP Underdahl, GJ Florakis, RE Braunstein, DA Johnson, P. Cheung, J. Briggs, DM Meisler: Propionibacterium acnes as a cause of visually significant corneal ulcers. In: Cornea. 19 (4), Jul 2000, pp. 451-454. PMID 10928755 .
  20. ↑ B. Ovodenko, JA Seedor, DC Ritterband, M. Shah, R. Yang, RS Koplin: The prevalence and pathogenicity of Propionibacterium acnes keratitis. In: Cornea. 28 (1), Jan 2009, pp. 36-39. doi: 10.1097 / ICO.0b013e3181839b1a PMID 19092402 .
  21. ↑ a b A. L. Perry, PA Lambert: Propionibacterium acnes. In: Letters in applied microbiology. Volume 42, Number 3, March 2006, pp. 185-188, ISSN  0266-8254 . doi: 10.1111 / j.1472-765X.2006.01866.x . PMID 16478502 . (Review).
  22. ↑ Ralf Gutzmer, Rudolf A. Herbst, Alexander Kapp, Jürgen Weiß: The SAPHO syndrome - case description of three patients with acne conglobata and osteoarticular symptoms In: The dermatologist. 48, Springer-Verlag, 1997, pp. 186-190. PMID 9182090 .

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