Ureaplasma urealyticum is a bacterium belonging to the genus Ureaplasma and the family Mycoplasmataceae[1] 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.
The six recognised Ureaplasma species have a GC content of 27 to 30 percent and a genome size ranging from 0.76 to 1.17 million base pairs, and cholesterol is required for growth.[2] A defining characteristic of the genus is that they perform urea hydrolysis, which creates ammonia as a product. Some strains originally classified as U. urealyticum should be treated as a new species, U. parvum. Both strains of Ureaplasma urealyticum have had their DNA sequenced, using a PCR amplification and dideoxy termination method.[3] Their sequences can be accessed through public records and databases. Most of the16S rDNA sequence of the two strains constitute the exact same nucleotides bases (97.3% homology), yet small differences have been acknowledged. Due to the direct similarity and the increased variation in other species of Ureaplasma, it is thought that the two strains of Ureaplasma urealyticum (T960 and 27) have evolutionary diverged together. In the same study conducted, using the same 16s rDNA aligned sequences, they concluded all the mammalian strains diverged and coevolved with their corresponding species (canine, feline, human, bovine) during the Cretaceous period. It was found that the most closely related species strain of Ureaplasma to Ureaplasma urealyticum was Ureaplasma diversum (isolated from bovine).
U. urealyticum represents one of the 14 distinct types within the Ureaplasma genus. Classified within the Mollicutes class, Ureaplasma species have undergone significant evolutionary adaptations from their Gram-positive bacterial ancestors, a phenomenon termed degenerative evolutions (Kallapur, Suhas G, et al 2013). This evolutionary trajectory has resulted in the loss of the peptidoglycan cell wall, a hallmark characteristic of Gram-positive bacteria. Despite this evolutionary divergence, instances have been reported where U. urealyticum, upon gram staining, exhibited the same characteristics as Gram-negative bacteria. Notably, despite such staining outcomes, it is imperative to recognize that the U. urealyticum remains a Gram-Positive bacterium, This discrepancy underscores the importance of discerning between staining outcomes and bacterial classification (“Ureaplasma Urealyticum.” Microbewiki).
As stated previously, since these bacteria are still considered Gram-positive, and lack a cell wall, the most versatile antibiotic that can’t be used is penicillin. Since these antibiotics attack the cell wall of a bacterium, they can not be used for this type of infection. The reason that many individuals get this infection can be damage to the uterus wall lining, causing the bacteria to thrive in a carbon-rich environment.
Unfortunately, it was found from trials that many of the antibiotics that we utilize on a day-to-day basis for urinary tract infections do not affect the bacteria due to lacking a cell wall. Yet, the types of antibiotics that can be used are quinolones, tetracyclines, and macrolides, since they affect a large part of the mycoplasma family of bacteria where U. urealyticum falls under.
Yet, it is not recommended to be used a lot because these bacteria can develop resistance to these antibiotics fairly fast. Secondly, other drugs that have β-lactamases are infective to treat infection because of how fast the bacteria's circular genome can mutate (Fan et al. 2023). However, there are new movements to use Azithromycin to treat these infections. This is a therapeutic that can be taken orally, once ingested our macrophages, which are part of our immune system, take up the antibiotic and deliver it to the sites of infection (Fan et al. 2023[4]). This helps control the infection where the bacteria grows, additionally, it is also a great alternative to when a mother is pregnant so it does not cause harm to the fetus since It's using our immune system to help defend the fetus and the mother's body.
To test for this bacterium, an agar plate, which is 10B broth, should be used on U. urealyticum. Since these bacteria love to grow in mostly acidic places, the bacteria should go under microdilution MIC dilution to get a pH color change. If the dilution color changes to red it indicates that there is presence of U. urealyticum in the sample. After this, it should be transferred to the 10B Broth, where once placed it will turn yellow, but then slowly change the color to pink. This helps to indicate the growth of the bacterium(Waites, Ken B, et al 2012[5]). The reason it can grow on this 10B Broth is because it has a lot of nutrients that let the bacteria grow from heart infusion to yeast extract, yet, it also has urea to help the bacteria to hydrolyze it and with hydrolyzing it causes the release of ammonia that causes the broth to change to a pink color (10B Broth - Thermo Fisher Scientific). The reason for this is that it loves to live in urea-rich environments. It's the same reason why in clinics, they take urine samples or vaginal swabs to be sent to the labs to run this test on 10B broth.
Ureaplasma urealyticum can cause urethritis and may cause bacterial vaginosis.[6] Infection can occur in extragenital sites.[7] A common symptom associated with these infections is the "fishy" smell that is created due to the production of ammonia by the hydrolysis of urea. Patients should confirm diagnosis with a doctor. The bacterium has high correlations with the Human Papillomavirus (HPV). It has also been linked to infertility in both males and females. In addition, this pathogen may latently infect the chorionic villi tissues of pregnant women, thereby impacting pregnancy outcome.[8] Issues that arise from Ureaplasma urealyticum infections during pregnancy include preterm birth and impacted embryonic development. Some patients have given birth to children subjected to bronchopulmonary dysplasia, Intraventricular hemorrhage, and necrotizing enterocolitis.[9] Patients can evolve resistances to normal antibiotic treatments due to the distinctive physiology of these organisms. In the Western World, approximately 40% of Ureaplasma species are resistant to fluoroquinolones (i.e. ciprofloxacin).[10] Patients who are pregnant have further limitations on the treatment course of a Ureaplasma urealyticum infection, making it far harder to successfully cure.