SKIN MICROBIOME GLOSSARY

The microorganisms living on our skin make up the skin microbiome. These microorganisms are essential for your skin health and their diversity is key. Keep reading to learn more about different the types of bacteria, fungi, and viruses you may find in your Skin Microbiome Test results.

Brevundimonas intermedia/nasdae/vesicularis:

Brevundimonas vesicularis is an opportunistic bacteria that causes problems for people who have underlying medical conditions (1). Brevundimonas vesicularis has been isolated from the eye, wound cultures, central nervous system, and cervical specimens (1). In scientific literature, there has only been 35 cases of infection due to B. vesicularis. B. vesicularis role in the skin microbiome is unknown.

References: 

1. Ryan MP, Pembroke JT. Brevundimonas spp: Emerging global opportunistic pathogens. Virulence. Published online February 27, 2018. Accessed January 12, 2021. https://www-tandfonline-com.silk.library.umass.edu/doi/abs/10.1080/21505594.2017.1419116

2. Photo: Brevundimonas vesicularis. Accessed January 19, 2021. https://microbe-canvas.com/Bacteria.php?p=494

Candida parapsilosis:

Candida parapsilosis is a type of yeast (1), which is part of the normal skin flora of both healthy skin and diseased skin (2). It is most commonly found in the oral cavity and vulvovaginal and urinary tracts (2). Candida parapsilosis is also present in systemic fungal nosocomial infections — infections that occur in hospitals. This usually happens when biofilms form on medically implanted devices, and this can cause infections in patients that have undergone invasive treatments (1). Candida parapsilosis is also the second most isolated species from blood cultures (2). It is currently unclear what the role of Candida parapsilosis is on the skin.

References: 

1. Tóth, R., Nosek, J., Mora-Montes, H. M., Gabaldon, T., Bliss, J. M., Nosanchuk, J. D., . . . Gácser, A. (2019). Candida parapsilosis: From Genes to the Bedside. Clinical Microbiology Reviews, 32(2). doi:10.1128/cmr.00111-18

2. Silva, S., Negri, M., Henriques, M., Oliveira, R., Williams, D. W., & Azeredo, J. (2012). Candida glabrata, Candida parapsilosisandCandida tropicalis: Biology, epidemiology, pathogenicity and antifungal resistance. FEMS Microbiology Reviews, 36(2), 288-305. doi:10.1111/j.1574-6976.2011.00278.x

3. Photo: Parandekar, Prashant K. (2012). Candida parapsilosis- Pink colored colonies on Hicrome agar. Research Gate. https://www.researchgate.net/figure/Candida-parapsilosis-Pink-colored-colonies-on-Hicrome-agar_fig2_255173809

Cladosporium sp:

Cladosporium sp are saprobic and dematiaceous fungi meaning that they colonize around rotting wood and dead organic matter and have a melanin pigment (1). Cladosporium sp are one of the most common fungal species on the planet, and they can be isolated from almost any environment and geographic location (1). They are most commonly found in soil and plant material (1). Cladosporium sp are associated with human and animal opportunistic infections, but these infections are extremely rare (1). Right now it is unclear what the role of Cladosporium sp is on the skin microbiome.

References: 

1. Sandoval-Denis, M., Sutton, D. A., Martin-Vicente, A., Cano-Lira, J. F., Wiederhold, N., Guarro, J., & Gené, J. (2015). Cladosporium Species Recovered from Clinical Samples in the United States. Journal of Clinical Microbiology, 53(9), 2990-3000. doi:10.1128/jcm.01482-15

2. Photo: (2016). Antifungal Susceptibility: Cladosporium species. Mycology Online https://mycology.adelaide.edu.au/descriptions/hyphomycetes/cladosporium/

Corynebacterium pseudogenitalium/tuberculostearicum:

Corynebacterium tuberculostearicum is a commensal bacterium that is commonly found on the human skin. C. tuberculostearicum can colonize different skin environments which include dry, moist, and sebaceous environments (1). C. tuberculostearicum has been associated with inflammatory breast disease, surgical site infections, and skin inflammation (1). It has also been associated with body odor (2). Mechanisms for these conditions are still poorly understood. For skin inflammation, there has been evidence to suggest that C. tuberculostearicum is able to upregulate proinflammatory molecules like cytokines in keratinocytes (1).

References: 

1. Altonsy MO, Kurwa HA, Lauzon GJ, et al. Corynebacterium tuberculostearicum, a human skin colonizer, induces the canonical nuclear factor-κB inflammatory signaling pathway in human skin cells. Immun Inflamm Dis. 2020;8(1):62-79. doi:https://doi.org/10.1002/iid3.284 

2. Troccaz M, Gaïa N, Beccucci S, et al. Mapping axillary microbiota responsible for body odours using a culture-independent approach. Microbiome. 2015;3(1):3. doi:10.1186/s40168-014-0064-3 

3. Photo: Corynebacterium tuberculostearicum a potential pathogen in breast abscess- A case report. IP Int J Med Microbiol Trop Dis. 2018;4(1):42-44. doi:10.18231/2455-6807.2018.0009

Cutibacterium Acnes:

Cutibacterium acnes is found in the normal skin flora and is involved in maintaining healthy skin. Cutibacterium acnes are mostly found in the sebaceous site of the skin. The sebaceous site is made up of glands attached to hair follicles, and they release sebum (oils) onto the skin that help to protect the skin from moisture. Cutibacterium acnes also plays a role in preventing harmful pathogens from colonizing the skin. It is also found in the intestine, stomach, lungs, mouth, conjunctiva, prostate and urinary tract (1). Cutibacterium acnes can also act as an opportunistic pathogen and researchers hypothesize that it is an important factor in acne, but it does not cause acne itself. It is currently not clearly understood how Cutibacterium acnes is involved in acne (1).

References:

1. Dréno, B., Pécastaings, S., Corvec, S., Veraldi, S., Khammari, A., & Roques, C. (2018). Cutibacterium acnes (Propionibacterium acnes) and acne vulgaris: A brief look at the latest updates. Journal of the European Academy of Dermatology and Venereology, 32(S2), 5–14. https://doi.org/10.1111/jdv.15043

2. Photo: May, Brandon. (2019). Dermatology Advisor. https://www.dermatologyadvisor.com/home/topics/acne/topical-cutibacterium-acnes-may-reduce-comedones-and-noninflamed-lesions-in-mild-to-moderate-acne/

Fungi sp:

Fungi species are found in the natural skin microbiome along with bacteria, archaea and host eukaryotic cells (human cells). Fungi species are also found in the gastrointestinal (GI) tract along with other microbes (1). The GI tract has its own nervous system, which is called the enteric nervous system. It communicates with the central nervous system to help keep the normal functions of the human organs. The richness and diversity of the microbiome in the GI tract play an important role in maintaining the normal metabolic and immunological functions of tissues and organs (1).

References: 

1. Belizário, J. E., Faintuch, J., & Garay-Malpartida, M. (2018). Gut Microbiome Dysbiosis and Immunometabolism: New Frontiers for Treatment of Metabolic Diseases. Mediators of Inflammation, 2018, 1-12. doi:10.1155/2018/2037838 

2. Photo: (2015). Stereum sp. Foxes Lair. https://www.foxeslair.org/resupinate-fungi.html

Geotrichum Bryndzae/candidum:

Geotrichum bryndzae/candidum are a type of yeast. It is typically found in Bryndza cheese and it has also been found is Asia in the cow rumen microbiota and in Chinese koji (1). It is also known to cause contamination in the production of white-brined cheese (2). It is still unclear what the role of Geotrichum bryndzae/candidum is in the skin microbiome.

 References: 

1. Sulo, P., Laurencik, M., Polakova, S., Minarik, G., & Slavikova, E. (2009). Geotrichum bryndzae sp. nov., a novel asexual arthroconidial yeast species related to the genus Galactomyces. International Journal Of Systematic And Evolutionary Microbiology, 59(9), 2370-2374. doi:10.1099/ijs.0.008938-0

2. Geronikou, A., Srimahaeak, T., Rantsiou, K., Triantafillidis, G., Larsen, N., & Jespersen, L. (2020). Occurrence of Yeasts in White-Brined Cheeses: Methodologies for Identification, Spoilage Potential and Good Manufacturing Practices. Frontiers in Microbiology, 11. doi:10.3389/fmicb.2020.582778

3. Photo: (2020). Geotrichum candidum. Wikipedia. https://en.wikipedia.org/wiki/Geotrichum

Lawsonella clevlandensis:

Lawsonella clevelandensis is typically found in the oral microbiome, and researchers also predict that it is also found in the skins and the bowel (1). It is rarely the cause of human infection, and there have only been 8 cases of infection that have been reported in literature (1). Lawsonella clevelandensis causes abscesses in the abdominal cavity, breast, and spine in immunocompromised patients (1). It is currently unclear what role Lawsonella clevelandensis is in the skin.

References

1. Zamora, J. A., Alvarez, M. R., Henry, Z., Baracco, G. J., Dickinson, G., & Lichtenberger, P. (2020). Liver abscess caused by Lawsonella clevelandensis in a patient with rheumatoid arthritis: A case report and literature review. IDCases, 20. doi:10.1016/j.idcr.2020.e00734

2. Photo: 

Navas, Maria E. Jump, Robin. Canaday, David H. Wnek, Maria D. SenGupta, Dhruba J. McQuiston, John R. Bell, Melissa. (2016). Microbiology Society. https://www.microbiologyresearch.org/content/journal/jmmcr/10.1099/jmmcr.0.005036?crawler=true

Lentinula novae/zelandiae:

Lentinula novae-zelandiae is a fungus native to New Zealand. L. novae-zelandiae is in the same genus as Lentinula edodes or better known as shiitake mushroom (1). Currently, it’s role on the skin, if any at all, is unclear.

References: 

1. Home - Lentinula novae-zelandiae TMI-1172 v1.0. JGI. Accessed January 6, 2021. https://mycocosm.jgi.doe.gov/Lennov1/Lennov1.home.html

2. Lentinula novae-zelandiae. Accessed January 19, 2021. http://www.hiddenforest.co.nz/fungi/family/omphalotaceae/lenti01.htm

Malassezia arunalokei:

Malassezia arunalokei is a yeast that colonize on the skin of warm-blooded animals (1). In humans, M. arunalokei can typically be found on the scalp. Like other species in the genus Malassezia, it has been associated with seborrheic dermatitis. Seborrheic dermatitis is an inflammatory skin disease that does not cause death (2). However, it does have potential in lowering quality of life of people who are affected by it. M. arunalokei was first isolated and identified in 2016 and not much is known about its role in seborrheic dermatitis. It’s closest relative is Malassezia restricta, a known causative agent of seborrheic dermatitis (1).

References:

1. Honnavar P, Prasad GS, Ghosh A, Dogra S, Handa S, Rudramurthy SM. Malassezia arunalokei sp. nov., a Novel Yeast Species Isolated from Seborrheic Dermatitis Patients and Healthy Individuals from India. J Clin Microbiol. 2016;54(7):1826-1834. doi:10.1128/JCM.00683-16 

2. Tucker D, Masood S. Seborrheic Dermatitis. In: StatPearls. StatPearls Publishing; 2020. Accessed January 4, 2021. http://www.ncbi.nlm.nih.gov/books/NBK551707/ 

3. Photo: Honnavar P, Prasad GS, Ghosh A, Dogra S, Handa S, Rudramurthy SM. Malassezia arunalokei sp. nov., a Novel Yeast Species Isolated from Seborrheic Dermatitis Patients and Healthy Individuals from India. J Clin Microbiol. 2016;54(7):1826-1834. doi:10.1128/JCM.00683-16

Malassezia globosa:

Malassezia globosa is a yeast that is normally found on the sebaceous sites of human skin and is mostly non-pathogenic. M. globosa is one of the commonly isolated Malassezia species from human skin (1). M. globosa has been identified as the predominate Malassezia species in many skin conditions such as pityriasis versicolor, Malassezia folliculitis, seborrheic dermatitis, psoriasis and atopic dermatitis (2). It has also been linked with onycomycosis, papillomatosis and acne (2). However, evidence for these three dermatological disorders linked with M. globosa are speculative. The presence of M. globosa alone cannot explain the development of a disease, as the environment and individual susceptibility are also important factors in pathogenicity (1). Studies have shown that M. globosa may have a positive role in maintaining a healthy skin microbiome. Many microbes on the skin can form biofilms, such as Staphylococcus aureus (3). In a study by Li et al., they found that certain proteases secreted by M. globosa may prevent S. aureus biofilm formation (1), maintaining the skin microbiome and preventing pathogenicity of S. aureus. This suggests that while M. globose has been associated with certain skin diseases, it also contributes to the overall health of the skin.

References: 

1. Li H, Goh BN, Teh WK, et al. Skin Commensal Malassezia globosa Secreted Protease Attenuates Staphylococcus aureus Biofilm Formation. J Invest Dermatol. 2018;138(5):1137-1145. doi:10.1016/j.jid.2017.11.034 

2. Prohic A, Jovovic Sadikovic T, Krupalija-Fazlic M, Kuskunovic-Vlahovljak S. Malassezia species in healthy skin and in dermatological conditions. Int J Dermatol. Published online December 1, 2015:n/a-n/a. doi:10.1111/ijd.13116

3. Ianiri G, Heitman J, Scheynius A. The Skin Commensal Yeast Malassezia globosa Thwarts Bacterial Biofilms to Benefit the Host. J Invest Dermatol. 2018;138(5):1026-1029. doi:10.1016/j.jid.2018.01.008 

4. Photo: Erchiga VC, Martos AO, Casaño AV, Erchiga AC, Fajardo FS. Malassezia globosa as the causative agent of pityriasis versicolor. Br J Dermatol. 2000;143(4):799-803.

Malassezialia restricta:

As of today, there have not been many studies done on Malassezia restricta, so there is not much information about what role it plays in the skin microbiome. So far researchers have discovered that Malassezia restricta along with other Malassezia species plays a role in causing dandruff, seborrheic dermatitis and pityriasis versicolor (1). These conditions are correlated with high levels of sebum on the skin. When these conditions improve it is usually correlated with a reduction of scalp Malassezia (1).

References: 

1. Dawson, T. L. (2007). Malassezia globosa and restricta: Breakthrough Understanding of the Etiology and Treatment of Dandruff and Seborrheic Dermatitis through Whole-Genome Analysis. Journal of Investigative Dermatology Symposium Proceedings, 12(2), 15-19. doi:10.1038/sj.jidsymp.5650049

2. Photo: Bosshard, Philipp. (2015). Microscopic image of a Malassezia spp. culture. Methylene blue Staining. Research Gate. https://www.researchgate.net/figure/Microscopic-image-of-a-Malassezia-spp-culture-Methylene-blue-staining_fig1_277982147

Malassezia sloofiae:

Malassezia sloofiae is typically found naturally on the skin along with other Malassezia species. It is most commonly found in the external ear canals, but it can also be found in other places on the skin, just in lower concentrations (2). Under some conditions Malassezia sloofiae causes an infection of the external ear canal (otitis externa) (2). This is usually triggered if there is a lot of water in the external ear canal, which encourages fungus and other bacteria to grow because they grow the best in moist environments. It is currently unclear what mechanisms Malassezia sloofiae uses to work with other microbes to cause this infection. Along with other Malassezia species, Malassezia sloofiae plays a role in causing dandruff, seborrheic dermatitis and pityriasis versicolor (1). It is currently unclear what its exact role is in causing these infections.

References: 

1. Dawson, T. L. (2007). Malassezia globosa and restricta: Breakthrough Understanding of the Etiology and Treatment of Dandruff and Seborrheic Dermatitis through Whole-Genome Analysis. Journal of Investigative Dermatology Symposium Proceedings, 12(2), 15-19. doi:10.1038/sj.jidsymp.5650049 

2. Kaneko, T., Shiota, R., Shibuya, S., Watanabe, S., Umeda, Y., Takeshita, K., . . . Makimura, K. (2010). Human external ear canal as the specific reservoir ofMalassezia slooffiae. Medical Mycology, 48(6), 824-827. doi:10.3109/13693780903514880

3. Photo: Nakamura, Yuka. (2007). Research Gate.  https://www.researchgate.net/figure/Colony-characteristics-of-M-furfur-M-japonica-and-M-slooffiae-on-CHROM-were_fig1_5960712

Malassezia sympodialis:

Malassezia sympodialis is a common commensal yeast found on the skin of warm blooded animals (1,2). M. sympodialis is one of the most abundant yeast on human skin, in both healthy individuals and in patients with skin problems (3). M. sympodialis has been found in sebum-rich areas of the skin (4) and it has been linked with Melassezia folliculitis, psoriasis, and more commonly to atopic dermatitis (1). While M. sympodialis’ role in Melassezia folliculitis and psoriasis are unclear, there has been research done in linking its potential role in the development of atopic dermatitis. M. sympodialis is able to release allergens, like Mala s 1 and Mala s 7, which can react to immune cells, leading to inflammation and sensitization of the skin (3). Free fatty acids because of M. sympodialis breaking down sebaceous lipids may also contribute to the development of many skin conditions (2). These allergens and fatty acids and a combination of genetics and environmental factors plays a role in the pathogenicity of M. sympodialis on the skin (4).

References: 

1. Prohic A, Jovovic Sadikovic T, Krupalija-Fazlic M, Kuskunovic-Vlahovljak S. Malassezia species in healthy skin and in dermatological conditions. Int J Dermatol. Published online December 1, 2015:n/a-n/a. doi:10.1111/ijd.13116 

2. Johansson HJ, Vallhov H, Holm T, et al. Extracellular nanovesicles released from the commensal yeast Malassezia sympodialis are enriched in allergens and interact with cells in human skin. Sci Rep. 2018;8(1):9182. doi:10.1038/s41598-018-27451-9

3. Vallhov H, Johansson C, Veerman RE, Scheynius A. Extracellular Vesicles Released From the Skin Commensal Yeast Malassezia sympodialis Activate Human Primary Keratinocytes. Front Cell Infect Microbiol. 2020;10. doi:10.3389/fcimb.2020.00006

4. Gioti A, Nystedt B, Li W, et al. Genomic Insights into the Atopic Eczema-Associated Skin Commensal Yeast Malassezia sympodialis. mBio. 2013;4(1). doi:10.1128/mBio.00572-12

5. Photo: Malassezia sympodialis - an overview | ScienceDirect Topics. Accessed January 19, 2021. https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/malassezia-sympodialis

Malasseziales sp:

The Malassezia species are a type of yeast that are normally found on the human skin and also on other warm blooded animals (3). There are also Malassezia species that are found in the gut along with other fungal species (2). Malasseia is typically found on healthy skin usually on the scalp, but it can also play a role in causing skin diseases. They play a role in causing dandruff, seborrheic dermatitis and pityriasis versicolor (1). The mechanisms that these Malassezia species use to cause these skin diseases is still being investigated.

References: 

1. Dawson, T. L. (2007). Malassezia globosa and restricta: Breakthrough Understanding of the Etiology and Treatment of Dandruff and Seborrheic Dermatitis through Whole-Genome Analysis. Journal of Investigative Dermatology Symposium Proceedings, 12(2), 15-19. doi:10.1038/sj.jidsymp.5650049 

2. Nash, A. K., Auchtung, T. A., Wong, M. C., Smith, D. P., Gesell, J. R., Ross, M. C., . . . Petrosino, J. F. (2017). The gut mycobiome of the Human Microbiome Project healthy cohort. Microbiome, 5(1). doi:10.1186/s40168-017-0373-4

3. Prohic, A., Sadikovic, T. J., Krupalija-Fazlic, M., & Kuskunovic-Vlahovljak, S. (2015). Malasseziaspecies in healthy skin and in dermatological conditions. International Journal of Dermatology, 55(5), 494-504. doi:10.1111/ijd.13116 

4. Photo: (2021). Malassezia furfur in skin scale from a patient with tinea versicolor. Wikipedia. https://en.wikipedia.org/wiki/Malassezia

Micrococcus aloeverae/luteus:

Micrococcus aloeverae and Micrococcus luteus are both typically found in the skin, and they are normally harmless (1). They can cause infections in immunocompromised people (1) such as septic arthritis, meningitis and prosthetic valve endocarditis (3). Micrococcus aloeverae is also found in the plant aloe vera (2). Both Micrococcus aloeverae and Micrococcus luteus are both closely related on the evolutionary tree (2). It is currently what specific roles these species play on the skin microbiome.

 

References: 

1. Song, S. H., Choi, H. S., Ma, S. K., Kim, S. W., Shin, J., & Bae, E. H. (2019). Micrococcus aloeverae - A Rare Cause of Peritoneal Dialysis-Related Peritonitis Confirmed by 16S rRNA Gene Sequencing. Journal of Nippon Medical School, 86(1), 55-57. doi:10.1272/jnms.jnms.2019_86-10

2. Prakash, O., Nimonkar, Y., Munot, H., Sharma, A., Vemuluri, V. R., Chavadar, M. S., & Shouche, Y. S. (2014). Description of Micrococcus aloeverae sp. nov., an endophytic actinobacterium isolated from Aloe vera. International Journal of Systematic and Evolutionary Microbiology, 64(Pt_10), 3427-3433. doi:10.1099/ijs.0.063339-0

3. Miltiadous, G., & Elisaf, M. (2011). Native valve endocarditis due to Micrococcus luteus: A case report and review of the literature. Journal of Medical Case Reports, 5(1). doi:10.1186/1752-1947-5-251

4. Photo: Dr.E.I. (2014). Micrococcus luteus in tetrads arrangement. Medical-Labs. http://www.medical-labs.net/micrococcus-luteus-930/

Neurospora crassa:

Neurospora crassa is a fungus that can be found in subtropical and tropical regions (1). N. crassa can be found growing on recently burned vegetation (1). It is also known as the pink or red bread mold (2). It is also the organism that was responsible for contaminating bread with red mold in French bakeries; however, it did lead to a change in how people understand genetics and biochemical and molecular pathways in microorganisms (3). N. crassa is known as a model organism (2), but its role in the skin microbiome is still unknown.

References: 

1. Perkins DD, Turner BC. Neurospora from natural populations: Toward the population biology of a haploid eukaryote. Exp Mycol. 1988;12(2):91-131. doi:10.1016/0147-5975(88)90001-1

2. Maheshwari R. Circadian rhythm in the pink-orange bread mould Neurospora crassa: for what? J Biosci. 2007;32:1053-1058. doi:10.1007/s12038-007-0107-z

3. Roche, C. M., Loros, J. J., Mccluskey, K., & Glass, N. L. (2014). Neurospora crassa: Looking back and looking forward at a model microbe. American Journal of Botany, 101(12), 2022-2035. doi:10.3732/ajb.1400377 

4. Photo: Montenegro-Montero, Alejandro. Benchfly. https://www.benchfly.com/blog/the-almighty-fungi-the-revolutionary-neurospora-crassa/

Neurospora crassa/discreta:

Neurospora discreta is a fungus and is a common model organism in experiments. N. discrete can naturally be found in soil (1). Its role on the skin is currently unknown.

References: 

1. Allison, Steven D. et al. 2018. “Temperature Acclimation and Adaptation of Enzyme Physiology in Neurospora Discreta.” Fungal Ecology 35: 78–86.

2. Photo: The Ecology and Biogeography of Neurospora. Accessed January 19, 2021. http://www.fgsc.net/Neurospora/sectionB4.htm

Prevotella timonesis:

Scientists just started studying Prevotella species during the 1990s (1) and they are still discovering who makes up the Prevotella species and who they are related to on the evolutionary tree. Prevotella species are naturally found in the human microbiome, but they can sometimes cause disease (1). They have been found on the oral cavity, upper respiratory tract and urogenital tract, and they have also been found in the rumen and hindgut of other mammals (1). In the case of infections caused by Prevotella it can lead to liver and spleen abscesses, cervical abscess, meningitis and sometimes endocarditis (1). It is currently unclear what role Prevotella timonensis has on the skin microbiome, and also what mechanisms it uses to cause these infections.

References: 

1. Glazunova, O. O., Launay, T., Raoult, D., & Roux, V. (2007). Prevotella timonensis sp. nov., isolated from a human breast abscess. International Journal of Systematic and Evolutionary Microbiology, 57(4), 883-886. doi:10.1099/ijs.0.64609-0

2. Photo: Tall, M.L. Ndongo, S. Ngom, I. Delerce, J. Khelaifia. S, Racult, D. Fournier, P.-E. Levasseur, A (2020). Semantic Scholar. https://www.semanticscholar.org/paper/Massilistercora-timonensis-gen.-nov.%2C-sp.-nov.%2C-a-Tall-Ndongo/b6d1781632e21d4b48c94c85791c08c6a2bd97ad

Pseudomonas fluorescens:

Pseudomonas fluorescens is most commonly found in water, moist soil and vegetation (1). It has also been found in clinical samples from the mouth, stomach and lungs of humans (2). Pseudomonas fluorescens rarely causes infections, but it does cause catheter-related bloodstream infections in cancer patients (1). This is usually caused by contamination of the blood products during transfusion, or using contaminated equipment during transfusions (2). It is currently unclear what the role of Pseudomonas fluorescens is on the skin.

References: 

1. Nishimura, T., Hattori, K., Inoue, A., Ishii, T., Yumoto, T., Tsukahara, K., . . . Nakayama, S. (2017). Bacteremia or pseudobacteremia? Review of pseudomonas fluorescens infections. World Journal of Emergency Medicine, 8(2), 151. doi:10.5847/wjem.j.1920-8642.2017.02.013

2. Scales, B. S., Dickson, R. P., Lipuma, J. J., & Huffnagle, G. B. (2014). Microbiology, Genomics, and Clinical Significance of the Pseudomonas fluorescens Species Complex, an Unappreciated Colonizer of Humans. Clinical Microbiology Reviews, 27(4), 927-948. doi:10.1128/cmr.00044-1

3. Photo: Boresi, Morgan.(2009). Missouri S &T. http://web.mst.edu/~djwesten/MoW/BIO221_2009/P_fluorescens.html

Rothia mucilaginosa:

Rothia mucilaginosa, formerly known as Stomatococcus mucilaginosus, is a bacteria often mistaken as corynebacterium or staphylococci due to their similar morphology (1). R. mucilaginosa is naturally found as part of the oral and upper respiratory flora and is typically non-pathogenic (2). It has been observed that many microbes found in the oral cavity have also been found on the human face. In immunocompromised individuals, R. mucilaginosa is known to cause disease in rare cases. Some of these diseases include dental diseases, endocarditis, bacteremia, meningitis, prosthetic joint infection, endophthalmitis, skin and soft tissue infections (2). Skin and soft tissue infections caused by R. mucilaginosa are rare. Usually, skin infection caused by R. mucilaginosa is indirectly caused by not taking antibiotics as instructed after an oral procedure, and there has only been one case study when this occured (3). Infections caused by R. mucilaginosa are usually treatable with antibiotics. It is unclear what the role of R. mucilaginosa is on the skin.

References: 

1. Droz S, Zbinden R. Rothia dentocariosa - Infectious Disease and Antimicrobial Agents. antimicrobe. Accessed January 1, 2021. http://www.antimicrobe.org/b230.asp 

2. Poyer F, Friesenbichler W, Hutter C, et al. Rothia mucilaginosa bacteremia: A 10-year experience of a pediatric tertiary care cancer center. Pediatr Blood Cancer. 2019;66(7):e27691. doi:https://doi.org/10.1002/pbc.27691

3. Rothia mucilaginosa, rarely isolated pathogen as an etiological factor of i. Accessed January 1, 2021. https://phmd.pl/resources/html/article/details?id=55242&language=en

4. Photo: Yamane K, Nambu T, Yamanaka T, et al. Complete Genome Sequence of Rothia mucilaginosa DY-18: A Clinical Isolate with Dense Meshwork-Like Structures from a Persistent Apical Periodontitis Lesion. Sequencing. doi:https://doi.org/10.1155/2010/457236

Staphylococcus capitis:

Staphylococcus capitis is a commensal bacterium, often found in the human scalp and forehead (1). They are also abundant in sebaceous and moist sites (2). S. capitis can also naturally be found in the environment and in the digestive tract (3). S. capitis is known as an opportunistic pathogen, causing disease if the host immunity is low. Some of these include endocarditis, tissue infection, prosthetic joint infection, osteomyelitis, and bloodstream infections (3). S. capitis is normally found on the surface of human skin, but when medical devices are inserted, some of the bacteria may enter the body with the device, causing infection. However, this is rare since S. capitis is known to have poor adherence on non-human skin surfaces (1). On the human skin, S. capitis has been observed to secrete anti-microbial molecules, which prevents competition from other microbes and prevents skin infection caused by pathogen colonization (2).

References: 

1. Tchana-Sato V, Hans G, Frippiat F, et al. Surgical management of Staphylococcus capitis prosthetic valve infective endocarditis: Retrospective review of a 10-year single center experience and review of the literature. J Infect Public Health. 2020;13(11):1705-1709. doi:10.1016/j.jiph.2020.09.010 

2. Kumar R, Jangir PK, Das J, Taneja B, Sharma R. Genome Analysis of Staphylococcus capitis TE8 Reveals Repertoire of Antimicrobial Peptides and Adaptation Strategies for Growth on Human Skin. Sci Rep. 2017;7. doi:10.1038/s41598-017-11020-7

3. Ding L, Li P, Yang Y, Lin D, Xu X. The epidemiology and molecular characteristics of linezolid-resistant Staphylococcus capitis in Huashan Hospital, Shanghai. J Med Microbiol. 2020;69(8):1079-1088. doi:10.1099/jmm.0.001234

4. Photo: Staphylococcus capitis. In: Wikipedia. ; 2020. Accessed January 19, 2021. https://en.wikipedia.org/w/index.php?title=Staphylococcus_capitis&oldid=962297781

Staphylococcus caprae:

Staphylococcus caprae is a commensal bacterium that has been found on animals and humans. In humans, S. caprae has been isolated from the skin, nasal mucosa, and nails (1). It is known as an opportunistic pathogen, causing disease after a patient underwent medical care and occurring frequently in healthcare settings (2). S. caprae has been found to be able to form biofilms, which is a virulence factor that is common with other Staphylococcus species (1). Its role on the skin is undefined.

References: 

1. Gowda A, Pensiero AL, Packer CD. Staphylococcus caprae: A Skin Commensal with Pathogenic Potential. Cureus. 10(10). doi:10.7759/cureus.3485  

2. Watanabe S. Complete genome sequencing of three human clinical isolates of Staphylococcus caprae reveals virulence factors similar to those of S. epidermidis and S. capitis. BMC 2018. 19:1-17. doi:10.1186/s12864-018-5185-9

3. Photo: Staphylococcus caprae. Accessed January 19, 2021. https://microbe-canvas.com/Bacteria.php?p=1147

Staphylococcus epidermis:

Staphylococcus epidermidis is found in the normal skin flora and is usually not harmful to humans at all. Not only does it colonize on the skin, it also colonizes on mucus membranes. (1) Staphylococcus epidermidis can become an opportunistic pathogen when it invades the human body. This usually happens with medical devices and prosthetic devices, when bacteria from the human skin colonize on the device and enter the bloodstream. (2) Researchers are beginning to think that acne may be caused by an unbalanced equilibrium between Cutibacterium acnes and Staphylococcus epidermidis. This is because they predict that Staphylococcus epidermidis might control the imbalance that might be caused by Cutibacterium acnes, which might reduce the severity of acne. (3)

References: 

1. Otto, M. (2009). Staphylococcus epidermidis — the 'accidental' pathogen. Nature Reviews Microbiology, 7(8), 555-567. doi:10.1038/nrmicro2182

2. Lee, E., & Anjum, F. (2020). Staphylococcus Epidermidis. StatPearls Publishing. doi:https://www.ncbi.nlm.nih.gov/books/NBK563240/

3. Claudel, J., Auffret, N., Leccia, M., Poli, F., Corvec, S., & Dréno, B. (2019). Staphylococcus epidermidis: A Potential New Player in the Physiopathology of Acne? Dermatology, 235(4), 287-294. doi:10.1159/000499858

4. Photo: Collins, Francis. (2017). Scanning electron microscopic image of Staphylococcus aureus bacteria. NIH Director’s Blog.             https://directorsblog.nih.gov/tag/staphylococcus-epidermidis/.

Streptococcus mitis:

Streptococcus mitis is a commensal bacteria that is found on the skin, mucous membrane and in the oral cavity (1,2). While usually non-pathogenic on the skin and widely accepted as normal flora in humans (3), S. mitis can become pathogenic in certain cases. Endocarditis is a condition caused by inflammation of the heart lining. The severity of this condition includes the virulence of the organism, such as S. mitis. Certain conditions such as prosthetic valves and drug use may increase a person’s chances in developing endocarditis (4). In this condition, the most common dermatological presentation is purpura, which are purple spots on the skin (4). Osler’s nodes, which are painful and raised lesions, and Janeway lesions found on the palms or soles can also develop (4). Certain metals can cause S. mitis to secrete molecules that can lead to skin sensitization. In a study where reconstructed human skin and gingiva were exposed to metals such as nickel and titanium, S. mitis strongly enhanced the immune response in the presence of nickel on the skin, but the response was low in gingiva (2). Titanium on the other hand, did not show an increased immune response in the skin or the gingiva, which suggested titanium metal was not sensitizing when in contact with the skin (2). Other types of conditions associated with S. mitis are certain oral infections and in rare cases, S. mitis can become respiratory pathogens (1).

References: 

1. Streptococcus mitis - microbewiki. Accessed December 31, 2020. https://microbewiki.kenyon.edu/index.php/Streptococcus_mitis 

2. Shang L, Deng D, Roffel S, Gibbs S. Differential influence of Streptococcus mitis on host response to metals in reconstructed human skin and oral mucosa. Contact Dermatitis. 2020;83(5):347-360. doi:10.1111/cod.13668

3. Shelburne SA, Sahasrabhojane P, Saldana M, et al. Streptococcus mitis Strains Causing Severe Clinical Disease in Cancer Patients. Emerg Infect Dis. 2014;20(5):762-771. doi:10.3201/eid2005.130953

4. Degheim G, Hiner E, Berry A, Foster N. Dermatologic Conundrum: A Cardiac Condition Masqueraded as a Dermatologic Distraction. Case Reports in Infectious Diseases. doi:https://doi.org/10.1155/2020/5314503  

5. Photo: DM Lab 15 - Gram Stain Results. Accessed January 19, 2021. https://www.medschool.lsuhsc.edu/Microbiology/DMIP/ostrep.htm

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