. Ureaplasma urealyticum Infections

Ureaplasma urealyticum Infections


 

Tara M. Randis and Adam J. Ratner


 

Initially referred to as T-strain (“tiny strain”) mycoplasma, these pleomorphic organisms measure less than 500 nm in diameter, lack a cell wall, and are classified as members of the family Mycoplasmatacea.2Ureaplasma differ from other Mycoplasmatacea in that they produce urease and therefore are capable of generating adenosine triphosphate from hydrolysis of urea. Ureaplasma urealyticum has historically been subtyped into 14 serovars. However, recent molecular characterization of these serovars has resulted in a reclassification of U urealyticum into 2 distinct species: U parvum (serovars 1, 3, 6, and 14) and U urealyticum (serovars 2, 4, 5, and 7–13).3


ImageEPIDEMIOLOGY


Ureaplasma spp are found on the cervical or vaginal mucosal surfaces of the majority of asymptomatic women and may therefore be considered commensal organisms of the adult female genital tract.4 Colonization of the male urethra has also been described, although it appears to occur less frequently. Although they may colonize in the absence of symptoms or pathology, there is ample evidence implicating Ureaplasma as the primary etiologic agent in a variety of urogenital diseases in both men and women.


Mucosal colonization with Ureaplasma occurs less commonly in adolescents and young children than in adults and increases in frequency with the onset of sexual activity. Vertical transmission of Ureaplasma with resulting mucosal colonization of the neonate occurs commonly (> 10% of births to colonized mothers), is increased in frequency in the setting of prolonged rupture of membranes and low birth weight, and may persist for several months postnatally.


Ureaplasma spp produce a number of virulence factors including immunoglobulin A protease, phospholipases A and C, hydrogen peroxide, NH3, and the more recently recognized hemolysins.4 Phospholipases may be of particular importance as they are hypothesized to play a role in the development of preterm labor in colonized, pregnant women by liberating arachidonic acid and increasing prostaglandin synthesis.


ImageCLINICAL FEATURES


Genitourinary Infection

Ureaplasma spp may cause urethritis in both men and women. Ureaplasma urealyticum in particular is frequently isolated from male adolescent and adult patients with nongonoccal urethritis. Epididymitis and prostatitis secondary to U urealyticum have also been described.5,6 The presence of Ureaplasma in the urinary tract has been linked to local formation of stones, possibly mediated by urease activity. Colonization and/or infection of the female genital tract are associated with numerous obstetrical complications including infertility, spontaneous abortion, chorioamnionitis, preterm labor, and postpartum endometritis.2,4,7 It is important to note that Ureaplasma are capable of invading the intrauterine space including the maternal–fetal membranes and are the most common organisms isolated from amniotic fluid, infected placentas, and neonatal cord blood.8,9


Neonatal Infection

Ureaplasma spp are now recognized to play an etiologic role in neonatal respiratory disease. The organism has been isolated from the lungs of stillborn infants with pneumonitis, from amniotic fluid, and from the lungs of neonates with histologic pneumonia at less than 24 hours after birth and with a concomitant increase in fetal Ureaplasma-specific IgM antibiodies.4,10,11Image Clinically, the manifestations of congenital Ureaplasma pneumonia may be difficult to distinguish from those of respiratory distress syndrome commonly seen in these infants.


Ureaplasma infection in the newborn is not limited to the respiratory tract, as these organisms have been isolated from both the blood and cerebral spinal fluid (CSF), particularly in preterm infants and those with positive endotracheal tube aspirates.4 A recent study demonstrated the presence of Ureaplasma by polymerase chain reaction (PCR) in the blood and/or CSF in 23% of very low birth weight infants.13 However, the clinical relevance and long-term implications of these findings remain unclear, as most PCR-positive infants were asymptomatic.


Chronic Lung Disease

The relationship between Ureaplasma respiratory tract colonization of preterm infants and the subsequent development of bronchopulmonary dysplasia (BPD) has been the subject of much investigation over the past several decades. The most recent meta-analysis examined 26 peer-reviewed clinical studies published from 1966 through 2004 involving infants with positive culture or polymerase chain reaction (PCR) analysis for the presence of Ureaplasma in the nasopharynx or tracheal aspirates and concluded that a positive correlation between Ureaplasma colonization and the development of BPD does exist.15


Other Infections

Although Ureaplasma pneumonia is exceedingly uncommon in older children and adolescents, it may be problematic for the immune-compromised host. Infectious arthritis secondary to Ureaplasma has been described, particularly in patients with hypogammaglobulinemia.19


ImageDIAGNOSTIC EVALUATION


Routine culture of the vagina and cervix is not indicated, owing to the large number of asymptomatically colonized adults. Similarly, a high rate of perinatal colonization argues against routine screening of asymptomatic newborns. However, evidence of respiratory compromise, pneumonia, sepsis, and/or meningitis in the absence of positive cultures for typical neonatal pathogens warrants consideration of Ureaplasma infection. Ureaplasma may be difficult to culture, and therefore careful attention must be given to specimen collection. For maximum yield, specimens must be inoculated into appropriate growth medium at the bedside and processed immediately.


Detection of Ureaplasma by polymerase chain reaction (PCR) based techniques may exhibit sensitivity superior to traditional culture techniques and has been described in the literature, although its clinical availability remains limited at this time.


ImageTREATMENT


Macrolides are the most widely used antimicrobial agents in treatment of Ureaplasma infections. Although the newer macrolides such as azithromycin are most frequently utilized in older children and adults, erythromycin is the treatment of choice for neonatal infections that do not involve the central nervous system. Of note, erythromycin therapy use in infants has been associated with the development of hypertrophic pyloric stenosis and should thus be used with care. Urea-plasma spp are generally susceptible to tetracyclines, although resistance has been reported to occur in as many as 10% of clinical isolates.4 The ability of tetracycline agents to penetrate the blood-brain barrier makes them a treatment option for infants with meningitis. However, tetracycline use in children under age 8 years is reserved for settings in which the benefits clearly outweigh the risks, as these agents may cause abnormal bone and tooth development in children.


Newer generation fluoroquinolones such as ofloxacin are active against Ureaplasma spp, although naturally occurring resistance has been documented in adult patients. Ureaplasma are universally resistant to β-lactam antibiotics as they lack a cell wall.


Despite the clear association of Ureaplasma colonization with spontaneous abortion, chorioamnionitis, and the onset of preterm labor, the efficacy of antimicrobial treatment both before and during pregnancy in preventing these outcomes remains unclear. Image A Cochrane Review concluded there was insufficient evidence to determine whether giving antibiotics to women with vaginal Ureaplasma colonization would prevent preterm birth.25


The association of Ureaplasma spp with the subsequent development of bronchopulmo-nary dysplasia (BPD) raises the possibility that early treatment and eradication of this organism in at-risk infants may be beneficial. To date, two small, randomized, prospective, and controlled studies have not shown a benefit for infants receiving erythromycin therapy with respect to rates or severity of BPD.26,27 It is possible that postnatal antimicrobial therapy for Ureaplasma-associated BPD may not be effective because the responsible inflammatory processes may be initiated in utero.


REFERENCES


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Jan 7, 2017 | Posted by in PEDIATRICS | Comments Off on . Ureaplasma urealyticum Infections

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