Difference between revisions of "Ureaplasma parvum"
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Latest revision as of 19:16, 19 August 2010
A Microbial Biorealm page on the genus Ureaplasma parvum
Higher order taxa
cellular organisms; Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Ureaplasma; Ureaplasma parvum
Description and significance
In 1954 Maurice C. Shepard described tiny mycoplasmas he found within the human urogenital tract. Denys K. Ford in 1962 confirmed these mycoplasmas as being self replicating entities that grew at a low pH. Growing in colonies resembling fried eggs they were put in the Ureaplasma genus. The cells were either spherical or coccobacillary shaped Gram-positive microbes that cannot be seen with the naked eye. The cell diameter ranges from 0.1 to 1.0 µm. Its type strain is T960. Named in 1974 by Shepard with its official name Ureaplasma urealyticum there were 14 identified serotypes (servars). A few of them were associated with diseases. Within these serotypes two distinct groups were recognized. Separated depending on their phenotypic markers such as clustering of antigenic types, polypeptide patterns of whole cell preparations, differential inhibition by manganese, and polymorphism among their ureases, pyrophosphatases and diaphorases. They were known as biovar 1 and biovar 2. After long debates in 2002 they were separated into two distinct species: Ureaplasma parvum and Ureaplasma urealyticum. Serovars 1,3,6 and 14 were designated as U. parvum (previously U. urealyticum biovar 1) due to their slightly smaller genome size.
Ureaplasma parvum is a pathogenic ureolytic mollicute (mycoplasma) commonly found in healthy and diseased humans. It is one of the smallest free living organisms known. Linked to many neonatal, male, and female specific diseases there has been research recently in the medical field to determine how it causes diseases. In 2000 the full genome of Ureaplasma parvum biovar 3 was sequenced with a GenBank accession no. NC_002162.
Ureaplasma parvum has a circular chromosome consisting of 751,719 base pairs. Its chromosome encodes 605 Open Reading Frames and 38 RNA genes. The G+C content is 25% which is relatively low compared to other species. Having a reduced genome it has a fast evolutionary rate. It does not have the LexA repressor which suppresses the SOS response genes. The SOS response genes are used in DNA repair. Its fast evolutionary rate may account for the lack of LexA genes and mutant genes. The tuf DNA sequence is the same within serovars of Ureaplasma parvum. It was used to differentiate within the species and at times reflects a better phenotypic relationship than 16S rRNA gene sequencing does.
Cell structure and metabolism
The mycoplasma has very low biosynthetic capacity meaning it must import many important nutrients from other bacteria. Retaining a spherical or coccobacillary shape it is on the diameter of 0.1 to 1.0 µm. It is a sterol requiring non obligate anaerobe which makes it sensitive to digitonin. Growing in low pH between 6.0 and 6.5 it does not use glucose, carbohydrates, or arginine to generate ATP. Using a urea hydrolase it hydrolyses urea to generate ATP through a chemiosmotic mechanism. Even though it is part of the Gram-positive bacteria, it lacks a bacterial cell wall which means when put through a Gram stain it takes on the color of the counter stain rather than the crystal violet. Ureaplasma parvum is unique in the fact that it expresses the human immunoglobulin A1 protease.
The species prefers to grow in acidic pH between 6.0-6.5. It colonizes the human urinary and genital tracts causing a variety of diseases that are discussed in the pathology section. Growing in colonies it can reach roughly 108 organisms per ml but due to the small cellular mass it does not cause much disturbance. Many of the colonies are described as “fried-egg” colonies. Mutations within the 23Sr RNA and ribosomal proteins L4 and L22 have caused macrolide resistance within Ureaplasma parvum. This has allowed it to survive in environments normally hostile to other microbes such as the urinary-genital tract and resistant to antimicrobial drugs.
Ureaplasma parvum has been associated with the cause of various diseases. Being a human pathogen it is not a natural pathogen for other animals such as rodents. It has been categorized as a mucosal parasite living within the genito-urinary tracts. It is a mycoplasma and pathogenic ureolytic mollicute which can cause male urethritis, supperative arthritis, adverse pregnancy outcomes, chorioamnionitis, surgical wound infections, neonatal meningitis, pelvic inflammatory diseases, pyelonephritis, and neonatal disease. Ureaplasma parvum can cause infertility via placental inflammation and infection of the amniotic sac during early pregnancies causing abnormal outcomes during pregnancy. Infection of the lower lung can cause chronic lung disease in premature babies and/or broncohpulmonary dysplasia. Lower respiratory infection can also cause infants with low birth weights leading to congenital pneumonia, meningitis, and even death. Many preterm infants with chronic lung disease have had Ureaplasma parvum isolated from their respiratory secretions. It has also been found in infants with Respiratory Distress Syndrome. RDS (respiratory distress syndrome) is a major factor in the high mortality of preterm infants from pulmonary diseases. During delivery of a baby, if the mother is infected with Ureaplasma parvum, it may be spread to the CNS or respiratory tract of the infant leading to pneumonia, meningitis, and septicemia. Isolates of U. parvum have been found in maternal blood, umbilical cord blood, and neo-natal blood. Strangely 20% of newborn infants have a Ureaplasma parvum infection while most preterm infants harbor the organism, yet by 3 months of age U. parvum colonization has declined drastically.
Application to Biotechnology
A better understanding of Ureaplasma parvum and Ureaplasma urealyticum may give us better knowledge of what diseases it causes. By understanding the microbe’s mechanisms it may be possible to link the microbes to a specific disease and develop antibiotics to counter them. The knowledge of Ureaplasma parvum as the only one expressing human immunoglobulin A1 protease or its mechanisms for macrolide resistance may further the development of improved macrolides or other antimicrobial drugs. Currently the research being down is not towards the biotechnology applications but research towards understanding the microbe as seen in the current research section.
1) Recent PCR sequencing in China and France has found Fluoroquinolone resistance in Ureaplasma parvum. The resistance is linked to a change in amino acid 83 of UU467 (parC) and at amino acid 112 of UU082 (gyrA). The serine at amino acid 83 was replaced with leucine and the amino acid at 112 was replaced with glutamic acid. The resistance has made treatment for vaginal infection difficult and many times prolonged antimicrobial therapy is required. Along with the increase in Fluoroquinolone resistance, 45% of the Ureaplasma parvum species were found to have tetracycline resistance and contained tet(M). An increasing resistance to multiple drug classes seems to be the general trend.
2) To determine Ureaplasma parvum involvement in certain diseases rats were used as test subjects. It is not a natural pathogen for rodents however it can be induced by infection in the urinary tract. Diverse infections were discovered from these tests and the rats developed mild inflammation to pyelonephritis and urolithiasis. The susceptibility to urinary infection and struvite stone formation from Ureaplasma parvum was also investigated and found to be linked.
3) With a wide variety of diseases occurring from infection with Ureaplasma parvum, the study set out to determine which part of the U. parvum DNA was responsible for the outcome of the infection. Ten Ureaplasma parvum strains were analyzed through genome DNA macroarrays and 538 core genes were discovered. 79% of the genome was of unknown function while a newly identified pathogenicity island (UU145-UU170) was found. The UU145-UU170 island was determined to likely be a putative PAI determined the virulence of the microbe.
4) It has been found that Nuceloside diphosphate kinase (NDK) is missing in Mollicutues such as Ureaplasma parvum. The enzyme is involved in housekeeping functions as well as the synthesis of NTP’s and dNTPs. To determine how they make NTPs and dNTPs the nucleoside monophosphate kinase in Ureaplasma was studied. Using tritium labeled dNTP’s the catalytic rate for NMPK could be determined and calculated. “AdK, CMPK, and UMPK phosphorylated both ribos- respective deoxyribos- forms of nucleotides efficiently.” While TMPK was specific for dTMP and only “dUMP had some activity.” The NMPKs were found to be able to convert (d)NMPs to (d)NTPs and were base specific. The results of the experiment strongly supported the conclusion that NMPKs could fulfill the NDK role that was missing “in vivo.”
Cultrera, Rosario. et al. “Molecular evidence of Ureaplasma urealyticum and Ureaplasma parvum colonization in preterm infants during respiratory distress syndrome.” November 21, 2006. Volume 6. P.166.
Daubin, Vincent. et al. “Bacterial Molecular Phylogeny Using Supertree Aproach.” Genome Informatics. 2001. Volume 12. P.155-164.
Duffy, Lynn. et al. “Fluoroquinolone Resistance in Ureaplasma parum in the United States.” Journal of Clinical Microbiology. April 2006. P.1590-1591.
Katz, Brenda. et al. “Characterization of Ureaplasmas Isolated from Preterm Infants with and without Bronchopulmonary Dysplasia.” September 2005. Volume 43. Number 9. P.4852-4854.
Kong, Fanrong. et al. “Species Identificaiton and Subtyping of Ureaplasma parvum and Ureaplasma urealyticum Using PCR-Based Assays.” March 2000. Volume 38. Number 3. P.1175-1179.
Kong, Fanrong. Gilbert, Gwendolyn L.. “Postgenomic taxonomy of human ureaplasmas – a case study based on multiple gene sequences.” International Journal of Systematic and Evolutionary Microbiology. 2004. Volume 54. P.1815-1821.
Momynaliev, Kuvat. et al. “Comparitive genome analysis of Ureaplasma parvum clinical isolates.” Research in Microbiology. 2007. Volume 158. P.371-378.
Pereyre, S. et al. “Characterisation of in vitro-selected mutants of Ureaplasma parvum resistant to macrolides and related antibiotics.” International Journal of Antimicrobial Agents. Volume 29. P.207-211.
Reyes, Leticia. et al. “Rat Strains Differ in Susceptibility to Ureaplasma parvum-Induced Urinary Tract Infection and Struvite Stone Formation.” Infection and Immunity. December 2006. Volume 74. Number 12. P.6656-6664.
Robertson, Janet A.. et al. “Proposal of Ureaplasma parvum sp. Nov. and emended description of Ureaplasma urealyticum (Shepard et al. 1974) Robertson et al. 2001.” International Journal of Systematic and Evolutionary Microbiology. 2002. Volume 52. P.587-597.
Waites, Ken B. “Ureaplasma Infection.” WebMD. January 5, 2007.
Wang, Liya. “The role of Ureaplasma nucleoside monophosphate kinases in the synthesis of nucleoside triphosphates.” The FEBS Journal. 2007. Volume 274. P.1983-1990.
Yoshida, Takashi. et al. “Rapid Detection of Mycoplasma genitalium, Mycoplasma hominis, Ureaplasma parvum, and Ureaplasma urealyticum Organisms in Genitourinary Samples by PCR-Microtiter Plate Hybridization Assay.” Journal of Clinical Microbiology. May 2003. Volume 41. Number 5. P.1850-1855.
Edited by student Chris Katsura of Rachel Larsen and Kit Pogliano