Mycoplasma genitalium | |
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3D whole cell model of a Mycoplasma genitalium cell. Note this model does not include the terminal attachment organelle. | |
Scientific classification | |
Domain: | Bacteria |
Phylum: | Mycoplasmatota |
Class: | Mollicutes |
Order: | Mycoplasmoidales |
Family: | Mycoplasmoidaceae |
Genus: | Mycoplasmoides |
Species: | M. genitalium |
Binomial name | |
Mycoplasmoides genitalium (Tully et al. 1983) Gupta et al. 2018 [1] | |
Synonyms | |
Mycoplasma genitalium Tully et al. 1983 [2] |
Mycoplasma genitalium (also known as MG [3] ,Mgen, or since 2018, Mycoplasmoides genitalium [1] ) is a sexually transmitted, [4] small and pathogenic bacterium that lives on the mucous epithelial cells of the urinary and genital tracts in humans. [5] Medical reports published in 2007 and 2015 state that Mgen is becoming increasingly common. [6] [7] Resistance to multiple antibiotics, including the macrolide azithromycin, which until recently was the most reliable treatment, is becoming prevalent. [6] [8] The bacterium was first isolated from the urogenital tract of humans in 1981, [9] and was eventually identified as a new species of Mycoplasma in 1983. [2] It can cause negative health effects in men and women. It also increases the risk for HIV spread [10] with higher occurrences in those previously treated with the azithromycin antibiotics. [6] [11]
Mgen is a bacterium recognized for causing urethritis in both men and women along with cervicitis and pelvic inflammation in women. [12] It presents clinically similar symptoms to that of Chlamydia trachomatis infection and has shown higher incidence rates, compared to both Chlamydia trachomatis and Neisseria gonorrhoeae infections in some populations. [13]
Infection with Mgen can be symptomatic or asymptomatic. Both men and women may experience inflammation in the urethra (urethritis), characterized by mucopurulent discharge in the urinary tract, and burning while urinating. In women, it causes cervicitis and pelvic inflammatory diseases (PID), including endometritis and salpingitis. [12] Women may also experience bleeding after sex and it is also linked with tubal factor infertility. [5] [14] [15] For men, the most common signs are painful urination or a watery discharge from the penis. [16]
There is a consistent association of M. genitalium infection and female reproductive tract syndromes. M. genitalium infection was significantly associated with increased risk of preterm birth, spontaneous abortion, cervicitis, and pelvic inflammatory disease. In addition, this pathogen may latently infect the chorionic villi tissues of pregnant women, thereby impacting pregnancy outcome. [17] Infertility risk is also strongly associated with infection with M. genitalium, although evidence suggests it is not associated with male infertility. [18] When M. genitalium is a co-infectious agent risk associations are stronger and statistically significant. [19]
Polymerase chain reaction analyses indicated that it is a cause of acute non-gonococcal urethritis (NGU) and probably chronic NGU. It is strongly associated with persistent and recurring non-gonococcal urethritis (NGU), responsible for 15 percent to 20 percent of symptomatic NGU cases in men. [20] Unlike other mycoplasmas, the infection is not associated with bacterial vaginosis. [21] It is highly associated with the intensity of HIV infection. [22] Some scientists are performing research to determine if Mgen could play a role in the development of prostate and ovarian cancers and lymphomas in some individuals. These studies have yet to find conclusive evidence to suggest a link. [23]
The genome of M. genitalium strain G37T consists in one circular DNA molecule of 580,070 base pairs. [24] Scott N. Peterson and his team at the University of North Carolina at Chapel Hill reported the first genetic map using pulsed-field gel electrophoresis in 1991. [25] They performed an initial study of the genome using sequencing in 1993, by which they found 100,993 nucleotides and 390 protein-coding genes. [26] Collaborating with researchers at The Institute for Genomic Research (TIGR; now the J. Craig Venter Institute), which included Craig Venter, they made the complete genome sequence in 1995 using shotgun sequencing. [24] Only 470 predicted coding regions were identified in 1995, including genes required for DNA replication, transcription and translation, DNA repair, cellular transport, and energy metabolism. It was the second complete bacterial genome ever sequenced, after Haemophilus influenzae . [24] Later data from KEGG reports 476 protein-coding genes and 43 RNA genes, totaling 519. [27] It is unclear where the "525" gene count for the G37T stems from and what gene calling procedure was used. [28]
In 2006, the team at the J. Craig Venter Institute reported that only 382 genes are essential for biological functions. [29] The small genome of M. genitalium made it the organism of choice in The Minimal Genome Project, a study to find the smallest set of genetic material necessary to sustain life. [30]
There is limited divergence among clinical strains of M. genitalium. All strains retain the small genome size. [31]
Recent research shows that prevalence of Mgen is currently higher than other commonly occurring sexually transmitted infections (STIs). [32] Mgen is a fastidious organism with prolonged growth durations. This makes detection of the pathogen in clinical specimens and subsequent isolation extremely difficult. [33] Lacking a cell wall, Mycoplasma remains unaffected by commonly used antibiotics. [34] The absence of specific serological assays leaves nucleic acid amplification tests (NAAT) as the only viable option for detection of Mgen DNA or RNA. [35] However, samples with positive NAAT for the pathogen should be tested for macrolide resistance mutations, which are strongly correlated to azithromycin treatment failures, owing to rapid rates of mutation of the pathogen. [6] Mutations in the 23S rRNA gene of Mgen have been linked with clinical treatment failure and high level in vitro macrolide resistance. [36] Macrolide resistance mediating mutations have been observed in 20-50% of cases in the UK, Denmark, Sweden, Australia, and Japan. [6] Resistance is also developing towards the second-line antimicrobials like fluoroquinolone. [37]
According to the European guidelines, the indication for commencement of diagnosis for Mgen infection are: [35]
Screening for Mgen with a combination of detection and macrolide resistance mutations will provide the adequate information required to develop personalised antimicrobial treatments, in order to optimise patient management and control the spread of antimicrobial resistance (AMR). [35] [38]
Owing to the widespread macrolide resistance, samples that are positive for Mgen should ideally be followed up with an assay capable of detecting mutations that mediate antimicrobial resistance. The European Guideline on Mgen infections recommend complementing the molecular detection of Mgen with an assay capable of detecting macrolide resistance-associated mutations. Furthermore, molecular assays for quinolone resistance-associated mutations are available at specialised laboratories in suspected treatment failure due to treatment with moxifloxacin. [39]
The U.S. Centers for Disease Control and Prevention recommends a step-wise treatment approach for Mycoplasma genitalium with doxycycline for seven days followed immediately by a seven-day course of moxifloxacin as the preferred therapy due to high rates of macrolide resistance. [40] [41] [42] If resistance assay testing is available, and the Mgen is sensitive to macrolides, the CDC recommends a seven-day course of doxycycline followed by a four-day course of azithromycin. [40] Although the majority of M. genitalium strains are sensitive to moxifloxacin, resistance has been reported, and potential for serious, adverse side effects should be considered with this regimen. [43] Floroquinolones, including moxifloxacin, have been associated with disabling and potentially irreversible serious adverse reactions that have occurred together including:[ citation needed ]
and other serious side effects detailed in the FDA black box warning. Moxifloxacin/Avelox should be reserved for use when patients have no other treatment options. [44]
In settings without access to resistance testing, or if moxifloxacin cannot be used, the CDC recommends as an alternative regimen: seven days of doxycycline followed by the four-day course of azithromycin, with a test of cure 21 days after treatment being required due to the high rate of macrolide resistance. Beta lactam antibiotics are not effective against Mgen as the organism lacks a cell wall. [42]
In the UK the British Association for Sexual Health and HIV (BASHH) guidelines for treatment are: [45]
Treatment of Mycoplasma genitalium infections is becoming increasingly difficult due to rapidly growing antimicrobial resistance. [46] Diagnosis and treatment is further hampered by the fact that Mycoplasma genitalium infections are not routinely tested. [47] Studies have demonstrated that a 5-day course of azithromycin has a superior cure rate compared to a single, larger dose. Further, a single dose of azithromycin can lead to the bacteria becoming resistant to azithromycin. [48] Among Swedish patients, doxycycline was shown to be relatively ineffective (with a cure rate of 48% for women and 38% for men); and treatment with a single dose of azithromycin is not prescribed due to it inducing antimicrobial resistance. The five-day treatment with azithromycin showed no development of antimicrobial resistance. [49] Based on these findings, UK doctors are moving to the 5-day azithromycin regimen. Doxycycline is also still used, and moxifloxacin is used as a second-line treatment in case doxycyline and azithromycin are not able to eradicate the infection. [50] [51] In patients where doxycycline, azithromycin and moxifloxacin all failed, pristinamycin has been shown to still be able to eradicate the infection. [50]
Mycoplasma genitalium was originally isolated in 1980 from urethral specimens of two male patients with non-gonococcal urethritis in the genitourinary medicine (GUM) clinic at St Mary's Hospital, Paddington, London. [52] [53] It was reported in 1981 by a team led by Joseph G. Tully. [9] Under electron microscopy, it appears as a flask-shaped cell with a narrow terminal portion that is crucial for its attachment to the host cell surfaces. [54] The bacterial cell is slightly elongated somewhat like a vase, and measures 0.6–0.7 μm in length, 0.3–0.4 μm at the broadest region, and 0.06–0.08 μm at the tip. The base is broad while the tip is stretched into a narrow neck, which terminates with a cap. The terminal region has a specialised region called nap, which is absent in other mycoplasmas. Serological tests indicated that the bacterium was not related to known species of Mycoplasma. The comparison of genome sequences with other urinogenital bacteria, such as M. hominis and Ureaplasma parvum , revealed that M. genitalium is significantly different, especially in the energy-generating pathways, although it shared a core genome of ~250 protein-encoding genes. [55]
In 2018, Gupta et al. proposed to change the name of Mycoplasma genitalium to Mycoplasmoides genitalium on phylogenetic grounds, reflecting the existing knowledge that M. genitalium is not very related to other Mycoplasma. [1] The change became correct name under the International Code of Nomenclature of Prokaryotes (ICNP, "Code") with Validation List 184, published by the ICSP ("Committee"). [56] Mycoplasmaologists working in the field generally oppose this renaming. In 2019, they published an opinion paper arguing that even though the phylogenetic methods are valid, Gupta's renaming scheme causes too many changes, which is impractical and confusing. [57] They cite some essential principles of the Code, such as "no unnecessary new names", "aim at stability of names", and "avoid or reject the use of names which may cause error or confusion". [57] However, the 2019 argument for preserving old names was rejected by the Committee in Opinion 122 of 2022, [58] where it was ruled that the argument incorrectly cited the Code. [56] The Opinion emphasizes that use of an older validly published name remains acceptable under the Code. [58]
On 6 October 2007, Craig Venter announced that a team of scientists led by Nobel laureate Hamilton Smith at the J. Craig Venter Institute had successfully constructed synthetic DNA with which they planned to make the first synthetic genome. Reporting in The Guardian , Venter said that they had stitched together a DNA strand containing 381 genes, consisting of 580,000 base pairs, based on the genome of M. genitalium. [59] On 24 January 2008, they announced the successful creation of a synthetic bacterium, which they named Mycoplasma genitalium JCVI-1.0 (the name of the strain indicating J. Craig Venter Institute with its specimen number). [60] They synthesised and assembled the complete 582,970-base pair genome of the bacterium. The final stages of synthesis involved cloning the DNA into the bacterium E. coli for nucleotide production and sequencing. This produced large fragments of approximately 144,000 base pairs or 1/4th of the whole genome. Finally, the products were cloned inside the yeast Saccharomyces cerevisiae to synthesize the 580,000 base pairs. [61] [62] The molecular size of the synthetic bacterial genome is 360,110 kilodaltons (kDa). Printed in 10-point font, the letters of the genome cover 147 pages. [63]
On 20 July 2012, Stanford University and the J. Craig Venter Institute announced successful simulation of the complete life cycle of a Mycoplasma genitalium cell, in the journal Cell . [64] The entire organism is modeled in terms of its molecular components, integrating all cellular processes into a single model. Using object oriented programming to model the interactions of 28 categories of molecules, including DNA, RNA, proteins, and metabolites, and running on a 128 computer Linux cluster, the simulation takes 10 hours for a single M. genitalium cell to divide once—about the same time the actual cell takes—and generates half a gigabyte of data. [65]
The discovery of Protein M, a protein produced by M. genitalium, was announced in February 2014. [66] The protein was identified during investigations on the origin of multiple myeloma, a B-cell hematologic neoplasm. To understand the long-term Mycoplasma infection, it was found that antibodies from multiple myeloma patients' blood were recognised by M. genitalium. The antibody reactivity was due to a protein, designated Protein M, that is chemically responsive to all types of human and nonhuman antibodies available. The protein is about 50 kDa in size, and composed of 556 amino acids. [67]
Mgen evolved from a gram-positive ancestor that was clostridium-like but has lost the genes to code for the enzymes involved in de novo nucleic acid synthesis, amino acid synthesis, and synthesis of fatty acids. [68] This means that Mgen needs the host's growth factors to keep reproducing. Although Mgen has abilities that help it adhere to cells, it is still unknown how the bacteria can maintain an infection inside the epithelial cells of the ectocervix and vagina when shedding of the apical layer of cells occur. The organism's ability to have adhesion to host cells relies of two proteins, P110 and P140. Adhesion is an important step in beginning an infection in a cell and Mgen can adhere to spermatozoa, erythrocytes, and epithelial cells. The terminal organelle relies on these proteins as well because without them the organelle was not present. The segmented pair plates of Mgen [ vague ] is a core of dense electrons which is anchored to the cell membrane. The end of this core is in contact with the wheel complex and the wheel complex contains the proteins MG219, MG200, MG386, and MG491 which aid in the gliding motility of the bacteria. Although Mgen lacks secreted virulence factors, the protein MG186 degrades host nucleic acids due to it being a calcium-dependent membrane-associated nuclease.[ citation needed ]
Macrolides are a class of mostly natural products with a large macrocyclic lactone ring to which one or more deoxy sugars, usually cladinose and desosamine, may be attached. The lactone rings are usually 14-, 15-, or 16-membered. Macrolides belong to the polyketide class of natural products. Some macrolides have antibiotic or antifungal activity and are used as pharmaceutical drugs. Rapamycin is also a macrolide and was originally developed as an antifungal, but has since been used as an immunosuppressant drug and is being investigated as a potential longevity therapeutic.
Urethritis is the inflammation of the urethra. The most common symptoms include painful or difficult urination and urethral discharge. It is a commonly treatable condition usually caused by infection with bacteria. This bacterial infection is often sexually transmitted, but not in every instance; it can be idiopathic, for example. Some incidence of urethritis can appear asymptomatic as well.
Neisseria gonorrhoeae, also known as gonococcus (singular) or gonococci (plural), is a species of Gram-negative diplococci bacteria isolated by Albert Neisser in 1879. It causes the sexually transmitted genitourinary infection gonorrhea as well as other forms of gonococcal disease including disseminated gonococcemia, septic arthritis, and gonococcal ophthalmia neonatorum.
Mycoplasma is a genus of bacteria that, like the other members of the class Mollicutes, lack a cell wall, and its peptidoglycan, around their cell membrane. The absence of peptidoglycan makes them naturally resistant to antibiotics such as the beta-lactam antibiotics that target cell wall synthesis. They can be parasitic or saprotrophic. Several species are pathogenic in humans, including M. pneumoniae, which is an important cause of "walking" pneumonia and other respiratory disorders, and M. genitalium, which is believed to be involved in pelvic inflammatory diseases. Mycoplasma species are among the smallest organisms yet discovered, can survive without oxygen, and come in various shapes. For example, M. genitalium is flask-shaped, while M. pneumoniae is more elongated, many Mycoplasma species are coccoid. Hundreds of Mycoplasma species infect animals.
Nongonococcal urethritis (NGU) is inflammation of the urethra that is not caused by gonorrheal infection.
Chlamydia trachomatis is a gram negative, anaerobic bacterium that causes chlamydia and trachoma. C. trachomatis exists in two forms, an extracellular infectious body and an intracellular non-infectious body. There are currently 18 serovars that correlate with medical conditions including: trachoma, lymphogranuloma venereum, nongonococcal urethritis, cervicitis, salpingitis, pelvic inflammatory disease.C. trachomatis is the most common infectious cause of blindness and the most common sexually transmitted bacterium.
Haemophilus ducreyi are fastidious gram-negative coccobacilli bacteria.
Mycoplasma hominis is a species of bacteria in the genus Mycoplasma. M. hominis has the ability to penetrate the interior of human cells. Along with ureaplasmas, mycoplasmas are the smallest free-living organisms known.
Oxytetracycline is a broad-spectrum tetracycline antibiotic, the second of the group to be discovered.
Doxycycline is a broad-spectrum antibiotic of the tetracycline class used in the treatment of infections caused by bacteria and certain parasites. It is used to treat bacterial pneumonia, acne, chlamydia infections, Lyme disease, cholera, typhus, and syphilis. It is also used to prevent malaria. Doxycycline may be taken by mouth or by injection into a vein.
Azithromycin, sold under the brand names Zithromax and Azasite, is an antibiotic medication used for the treatment of a number of bacterial infections. This includes middle ear infections, strep throat, pneumonia, traveler's diarrhea, and certain other intestinal infections. Along with other medications, it may also be used for malaria. It is administered by mouth, into a vein, or into the eye.
Ureaplasma urealyticum is a bacterium belonging to the genus Ureaplasma and the family Mycoplasmataceae in the order Mycoplasmatales. This family consists of the genera Mycoplasma and Ureaplasma. Its type strain is T960. There are two known biovars of this species; T960 and 27. These strains of bacteria are commonly found as commensals in the urogenital tracts of human beings, but overgrowth can lead to infections that cause the patient discomfort. Unlike most bacteria, Ureaplasma urealyticum lacks a cell wall making it unique in physiology and medical treatment.
Rickettsia rickettsii is a Gram-negative, intracellular, coccobacillus bacterium that was first discovered in 1902. Having a reduced genome, the bacterium harvests nutrients from its host cell to carry out respiration, making it an organoheterotroph. Maintenance of its genome is carried out through vertical gene transfer where specialization of the bacterium allows it to shuttle host sugars directly into its TCA cycle.
Mycoplasma pneumonia is a form of bacterial pneumonia caused by the bacterium Mycoplasma pneumoniae.
Mycoplasmataceae is a family of bacteria in the order Mycoplasmatales. This family consists of the genera Mycoplasma and Ureaplasma.
Ureaplasma parvum is a species of Ureaplasma, a genus of bacteria belonging to the family Mycoplasmataceae.
Neisseria gonorrhoeae, the bacterium that causes the sexually transmitted infection gonorrhea, has developed antibiotic resistance to many antibiotics. The bacteria was first identified in 1879.
Protein M is an immunoglobulin-binding protein originally found on the cell surface of the human pathogenic bacterium Mycoplasma genitalium. It is presumably a universal antibody-binding protein, as it is known to be reactive against all antibody types tested so far. It is capable of preventing the antigen-antibody interaction due to its high binding affinity to any antibody. The Scripps Research Institute announced its discovery in 2014. It was detected from the bacterium while investigating its role in patients with a cancer, multiple myeloma.
The exact role of Mycoplasma hominis in regards to a number of conditions related to pregnant women and their (unborn) offspring is controversial. This is mainly because many healthy adults have genitourinary colonization with Mycoplasma, published studies on pathogenicity have important design limitations and the organisms are very difficult to detect. The likelihood of colonization with M. hominis appears directly linked to the number of lifetime sexual partners Neonatal colonization does occur, but only through normal vaginal delivery. Caesarean section appears protective against colonization and is much less common. Neonatal colonization is transient.
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