Mycoplasma hominis

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Mycoplasma hominis
Scientific classification edit
Domain: Bacteria
Phylum: Mycoplasmatota
Class: Mollicutes
Order: Mycoplasmatales
Family: Mycoplasmataceae
Genus: Mycoplasma
M. hominis
Binomial name
Mycoplasma hominis
(Freundt 1953) Edward 1955

Mycoplasma hominis is a species of bacteria in the genus Mycoplasma. M. hominis has the ability to penetrate the interior of human cells.[1] Along with ureaplasmas, mycoplasmas are the smallest free-living organisms known.

They have no cell wall and therefore do not Gram stain.[2]

Mycoplasma hominis is associated with pelvic inflammatory disease[3][4] and bacterial vaginosis.[5] It is also associated with male infertility.[6] This species causes a sexually transmitted disease.[7] It is susceptible to the antibiotic clindamycin.[8]

Growth of "fried egg" colonies on glucose agar medium within 24–48 hours is a characteristic of Mycoplasma hominis.[citation needed]

This pathogen may latently infect the chorionic villi tissues of pregnant women, thereby impacting pregnancy outcome.[9]

Biology and biochemistry

Mycoplasma hominis colonies

Type and morphology

Mycoplasma hominis is an opportunistic human mycoplasma species residing in the lower urogenital tract.[10] It is a common human urogenital Mycoplasma species that lacks a cell wall. Due to the absence of the cell wall, M. hominis is innately resistant to β-lactams and to all antibiotics which target the cell wall.[11] Additionally, it is the simplest self-replicating microorganism known.[12] This reaps consequences such as a lack of detection by light microscopy, and complex nutritional requirements.[11] Due to the fact that it does not have a cell wall, Mycoplasma hominis does not gram stain[2] although it is surprisingly often described as gram-negative.

The morphology is quite variable and seems to depend, in part, on the age of the culture as the smallest form observed, coming from the elementary body, is 80mµ to 100mµ wide in diameter.[13] Different cell forms have been observed varying from coccoid cells to filaments and irregularly shaped structures with coccoid forms and ring- or disc-shaped cells reigning predominant.[14] Coccal forms of the species are associated with binary fission while fragmentary filaments, and budding cells were also encountered.  This fact along with the fact that in different labs, the same strains grew at different rates, leads to the conclusion that cultural conditions have influenced the rate of division and cellular morphology in this species.[15]

The internal components of the much larger cells in the species are also variable. These cells can contain different structures such as ribosome-like granules, nuclear areas of netlike strands, dense cytoplasmic bodies and large vacuoles. These observations indicate multiple modes of reproduction for this organism.[13]


Analysis of the M. hominis PG21 genome sequence shows that this organism is the second smallest genome among self-replicating free living organisms.[10] Due to their minimal genomes, M. hominis have reduced metabolic capabilities which are characterized by distinct energy-generating pathways.[10] Three energy pathways that M. hominis is capable of going through is Embden-Meyerhoff-Parnas (EMP), arginine dihydrolase and Riboflavin metabolism.[10]

Culture growth

Cells of M. hominis prepared from batch cultures show uniform exponential growth and appear to divide through the process of binary fission with pleomorphic forms appearing upon further incubation.[16] Similar behavior was demonstrated by another laboratory-adapted strain and by three other clinical isolates, making this seem characteristic of the species.[16] M. hominis grows in a variety of defined laboratory media, such as arginine broth and can also be cultivated in water.[17] Growth in this species, as well as all species of mycoplasmas, is driven by anaerobic respiration.[18]

Role in disease

Site of localization

The primary sites of localization for M. hominis is the oropharynx and the genitourinary tract with positive pathogenicity.[19] It is capable of infecting human beings as well as non-human primates.[20]

Mycoplasma hominis is more than likely implicated in many different diseases, but its role is unclear for most of them. M. hominis is implicated in pelvic inflammatory disease, which may cause ectopic pregnancy.[20] It prospers in the environment created by other gram negative bacteria implicated in bacterial vaginosis and may be a cause of preterm delivery and miscarriage. It is also implicated in postpartum fever, because it may be a cause of endometritis. M. hominis is also suspected to be the cause of neonatal infections such as conjunctivitis, respiratory distress, fever, meningitis, abscesses, and congenital pneumonia.[20] In adults, M. hominis may be implicated in pharyngitis, septicaemia, lung infections, central nervous system infections, other respiratory tract infections, joint infection, and wound infections. M. hominis infections are usually not seen in healthy adults.[20]

Incubation period

The incubation period of M. hominis is unknown.[citation needed]


Many antibiotics kill bacteria by weakening those walls but since mycoplasma bacteria don't have them, some antibiotics, like penicillin, won't work against them.[21]

Oral tetracyclines have historically been the drugs of choice for use against urogenital and systemic infections due to M. hominis.[11] In locations and patient populations where tetracycline resistance or treatment failures are common, other drugs such as fluoroquinolones should be considered guided by in vitro susceptibility data when possible.[11]

Some infections may be treated by a single antibiotic.[11] In other cases such as severe M. hominis infections occurring in immunocompromised patients, combination of drugs usually active against the mycoplasmas have been recommended. In those cases, guidelines for optimal therapy remain to be established. Current therapeutic considerations are based only upon case reports.[11]


The bacterium is often passed through sex, so to help keep this infection away, safe sex practices should be used.[21]

Genome studies

DNA sequence data is incomplete for M. hominis. M. hominis uses an atypical type of energy metabolism, dependent upon the degradation of arginine. Other mycoplasmas lack this characteristic. Determining the genome will provide information that would facilitate the understanding of metabolic reconstitutions.[22]

See also


  1. "Mycoplasma hominis PG21". Site du Genoscope. 2013-10-19. Archived from the original on 2015-09-23. Retrieved 2015-08-30.
  2. 2.0 2.1 "Gram Staining Rules". Archived from the original on 2021-02-17. Retrieved 2020-08-02.
  3. Taylor-Robinson, D (Oct 1996). "Infections due to species of Mycoplasma and Ureaplasma: an update". Clin Infect Dis. 23 (4): 671–82. doi:10.1093/clinids/23.4.671. PMID 8909826.
  4. Ljubin-Sternak, Suncanica; Mestrovic, Tomislav (2014). "Review: Chlamydia trachomatis and Genital Mycoplasmias: Pathogens with an Impact on Human Reproductive Health". Journal of Pathogens. 2014 (183167): 183167. doi:10.1155/2014/183167. PMC 4295611. PMID 25614838.
  5. Mastromarino, Paola; Vitali, Beatrice; Mosca, Luciana (2013). "Bacterial vaginosis: a review on clinical trials with probiotics" (PDF). New Microbiologica. 36 (3): 229–238. PMID 23912864. Archived (PDF) from the original on 2015-05-18. Retrieved 2022-09-22.
  6. C. Huang; H.L. Zhu; K.R. Xu; S.Y. Wang; L.Q. Fan; W.B. Zhu (September 2015). "Mycoplasma and ureaplasma infection and male infertility: a systematic review and meta-analysis". Andrology. 3 (5): 809–816. doi:10.1111/andr.12078. PMID 26311339. S2CID 39834287.
  7. Sternak, p. 1.
  8. "Clindamycin" (PDF). FA Davis Company. 2017. Archived from the original (PDF) on 14 November 2017. Retrieved 15 December 2017.
  9. Contini C, Rotondo JC, Magagnoli F, Maritati M, Seraceni S, Graziano A, Poggi A, Capucci R, Vesce F, Tognon M, Martini F (2018). "Investigation on silent bacterial infections in specimens from pregnant women affected by spontaneous miscarriage". J Cell Physiol. 234 (1): 100–9107. doi:10.1002/jcp.26952. PMID 30078192.
  10. 10.0 10.1 10.2 10.3 Pereyre, Sabine; Sirand-Pugnet, Pascal; Beven, Laure; Charron, Alain; Renaudin, Hélène; Barré, Aurélien; Avenaud, Philippe; Jacob, Daniel; Couloux, Arnaud; Barbe, Valérie; de Daruvar, Antoine (October 2009). "Life on arginine for Mycoplasma hominis: clues from its minimal genome and comparison with other human urogenital mycoplasmas". PLOS Genetics. 5 (10): e1000677. doi:10.1371/journal.pgen.1000677. ISSN 1553-7404. PMC 2751442. PMID 19816563.
  11. 11.0 11.1 11.2 11.3 11.4 11.5 Pereyre, Sabine. “Mycoplasma Hominis, M. Genitalium and Ureaplasma Spp.” Mycoplasma Species (M. Hominis, M. Genitalium, M. Fermentans) - Infectious Disease and Antimicrobial Agents, 2002,
  12. Shyh-Ching Lo, Richard Y.-H. Wang, Teresa Grandinetti, Nianxiang Zou, Christine L.-D. Haley, Michael M. Hayes, Douglas J. Wear, James W.-K. Shih, Mycoplasma hominis Lipid-Associated Membrane Protein Antigens for Effective Detection of M. hominis-Specific Antibodies in Humans, Clinical Infectious Diseases, Volume 36, Issue 10, 15 May 2003, Pages 1246–1253,
  13. 13.0 13.1 Anderson, D. R.; Barile, M. F. (July 1965). "Ultrastructure of Mycoplasma hominis". Journal of Bacteriology. 90 (1): 180–192. doi:10.1128/JB.90.1.180-192.1965. ISSN 0021-9193. PMC 315612. PMID 16562016.
  14. Bredt, W. 1971. Cellular Morphology of Newly Isolated Mycoplasma hominis Strains. Journal of Bacteriology 105:1 449. <>.
  15. Robertson, J & Alfa, Michelle & Boatman, E. (1983). Morphology of the cells and colonies of Mycoplasma hominis. Sexually transmitted diseases. 10. 232-9.
  16. 16.0 16.1 Robertson, J.; Gomersall, M.; Gill, P. (November 1975). "Mycoplasma hominis: growth, reproduction, and isolation of small viable cells". Journal of Bacteriology. 124 (2): 1007–1018. doi:10.1128/JB.124.2.1007-1018.1975. ISSN 0021-9193. PMC 235991. PMID 1102522.
  17. Ball, H. J.; Neill, S. D.; Reid, L. R. (January 1982). "Use of arginine aminopeptidase activity in characterization of arginine-utilizing mycoplasmas". Journal of Clinical Microbiology. 15 (1): 28–34. doi:10.1128/JCM.15.1.28-34.1982. ISSN 0095-1137. PMC 272017. PMID 6764773.
  18. Mayer, Gene. Mycoplasma and Ureaplasma, The MicrobeLibrary, mycoplasmas are facultative anaerobes,pear shaped and even filamentous.
  19., incubation period is two,for years in hypogammaglobulinemic patients.
  20. 20.0 20.1 20.2 20.3 “Mycoplasma Hominis.” MSDSonline,
  21. 21.0 21.1 Felson, Sabrina. “Mycoplasma Infections: Symptoms, Treatment, and Prevention.” WebMD, WebMD, 28 Mar. 2020,
  22. "Mycoplasma hominis PG21". Site du Genoscope. 2013-10-19. Archived from the original on 2015-09-23. Retrieved 2015-08-30.

Further reading

  • Song, Tiejun; Ye, Aiqing; Xie, Xinyou; Huang, Jun; Ruan, Zhi; Kong, Yingying; Song, Jingjuan; Wang, Yue; Chen, Jianzhong; Zhang, Jun (September 2014). "Epidemiological investigation and antimicrobial susceptibility analysis of ureaplasma species and Mycoplasma hominis in outpatients with genital manifestations". Journal of Clinical Pathology. 67 (9): 817–820. doi:10.1136/jclinpath-2014-202248. PMID 24982440. S2CID 6089358.
  • Hasebe, Akira; Mu, Hong-Hua; Cole, Barry C (September 2014). "A Potential Pathogenic Factor from Mycoplasma hominisis a TLR2-Dependent, Macrophage-Activating, P50-Related Adhesin". American Journal of Reproductive Immunology. 72 (3): 285–295. doi:10.1111/aji.12279. hdl:2115/59366. PMID 24938999. S2CID 206987133.
  • Pignanelli S, Pulcrano G, Schiavone P, Iula VD, Catania MR. In vitro antimicrobial susceptibility of Mycoplasma hominis genital isolates. Indian J Dermatol Venereol Leprol. 2015 May-Jun;81(3):286-8. doi: 10.4103/0378-6323.153520.

External links