''Mycoplasma hominis'' is a species of bacteria in the genus ''

Mycoplasma ''Mycoplasma'' is a genus of bacteria that, like the other members of the class ''Mollicutes'', lack a cell wall around their cell membranes. Peptidoglycan (murein) is absent. This characteristic makes them naturally resistant to antibiotics ...

''. ''M.hominis'' has the ability to penetrate the interior of human cells. Along with

ureaplasma ''Ureaplasma'' is a genus of bacteria belonging to the family Mycoplasmataceae. As the name imples, ''Ureaplasma'' is urease positive. Phylogeny The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenc ...

s, mycoplasmas are the smallest free-living organisms known. They have no cell wall and therefore do not

Gram stain In microbiology and bacteriology, Gram stain (Gram staining or Gram's method), is a method of staining used to classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria. The name comes from the Danish ...

. ''Mycoplasma hominis'' is associated with

pelvic inflammatory disease Pelvic inflammatory disease, also known as pelvic inflammatory disorder (PID), is an infection of the upper part of the female reproductive system, namely the uterus, fallopian tubes, and ovaries, and inside of the pelvis. Often, there may be no ...

and

bacterial vaginosis Bacterial vaginosis (BV) is a disease of the vagina caused by excessive growth of bacteria. Common symptoms include increased vaginal discharge that often smells like fish. The discharge is usually white or gray in color. Burning with urination ...

. It is also associated with male infertility. This species causes a sexually transmitted disease. It is susceptible to the antibiotic

clindamycin Clindamycin is an antibiotic medication used for the treatment of a number of bacterial infections, including osteomyelitis (bone) or joint infections, pelvic inflammatory disease, strep throat, pneumonia, acute otitis media (middle ear infec ...

. Growth of "fried egg" colonies on glucose agar medium within 24–48 hours is a characteristic of ''Mycoplasma hominis''. This pathogen may latently infect the

chorionic villi Chorionic villi are villi that sprout from the chorion to provide maximal contact area with maternal blood. They are an essential element in pregnancy from a histomorphologic perspective, and are, by definition, a product of conception. Branche ...

tissues of pregnant women, thereby impacting pregnancy outcome.

Biology and biochemistry

Type and morphology

''Mycoplasma hominis'' is an opportunistic human mycoplasma species residing in the lower urogenital tract. It is a common human

urogenital The genitourinary system, or urogenital system, are the organs of the reproductive system and the urinary system. These are grouped together because of their proximity to each other, their common embryological origin and the use of common pathwa ...

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.Pereyre, Sabine. “Mycoplasma Hominis, M. Genitalium and Ureaplasma Spp.” ''Mycoplasma Species (M. Hominis, M. Genitalium, M. Fermentans) - Infectious Disease and Antimicrobial Agents'', 2002, www.antimicrobe.org/m06.asp. Additionally, it is the simplest self-replicating microorganism known. This reaps consequences such as a lack of detection by light microscopy, and complex nutritional requirements. Due to the fact that it does not have a cell wall, ''Mycoplasma hominis'' does not

gram stain In microbiology and bacteriology, Gram stain (Gram staining or Gram's method), is a method of staining used to classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria. The name comes from the Danish ...

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. 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. 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. 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.

Metabolism

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

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. Similar behavior was demonstrated by another laboratory-adapted strain and by three other clinical isolates, making this seem characteristic of the species. ''M. hominis'' grows in a variety of defined laboratory media, such as arginine broth and can also be cultivated in water. Growth in this species, as well as all species of mycoplasmas, is driven by anaerobic respiration.

Role in disease

Site of localization

The primary sites of localization for M. hominis is the oropharynx and the genitourinary tract with positive pathogenicity. It is capable of infecting human beings as well as non-human primates.“Mycoplasma Hominis.” ''MSDSonline'', www.msdsonline.com/resources/sds-resources/free-safety-data-sheet-index/mycoplasma-hominis/. ''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. 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. 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.

Incubation period

The incubation period of ''M. hominis'' is unknown.

Treatment

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.Felson, Sabrina. “Mycoplasma Infections: Symptoms, Treatment, and Prevention.” ''WebMD'', WebMD, 28 Mar. 2020, www.webmd.com/a-to-z-guides/mycoplasma-infections#1. Oral tetracyclines have historically been the drugs of choice for use against urogenital and systemic infections due to ''M. hominis.'' 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. Some infections may be treated by a single antibiotic. 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.

Prevention

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

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.

References

External links

Ureaplasma Infection: eMedicine Infectious Diseases

Kenyon College Microbe Wiki
for some images of mycoplasmas
Type strain of ''Mycoplasma hominis'' at Bac''Dive'' - the Bacterial Diversity Metadatabase
{{Taxonbar, from=Q2616475 Sexually transmitted diseases and infections Pathogenic bacteria Infections with a predominantly sexual mode of transmission Bacterial vaginosis Bacteria described in 1955 hominis