Ureaplasma urealyticum intrauterine infection: role in prematurity and disease in newborns

Small repeating units within the Ureaplasma urealyticum MB antigen gene encode serovar specificity and are associated with antigen size variation

Ureaplasma urealyticum is a common commensal of the female lower urogenital tract, yet it has been shown to be an important cause of chorioamnion infection, respiratory and central nervous system disease, and death in premature infants. It has been suggested that only certain serovars are capable of producing invasive disease. However, we previously showed that many serotypes are invasive and that perhaps antigen variability and host factors are more important determinants of ureaplasma infections than are different serotypes per se. The molecular characterization in this report describes a mechanism available to ureaplasmas for producing antigen variation. That antigen, designated MB and previously identified on U. urealyticum, contains serovar-specific and cross-reactive epitopes, is produced both in vitro and in vivo, is a predominant antigen recognized during ureaplasma infections of humans, undergoes a high rate of size variation in vitro, and is size variable on invasive ureaplasma isolates. In the present study, we cloned and sequenced the gene of the MB antigen from serovar 3, the serovar most commonly isolated from humans. The 3' two-thirds of the gene was shown to contain identical 18-nucleotide tandem repeats. PCR analysis and direct sequencing of two variants indicated that alterations within this repeat region are responsible for the size variation of the MB antigen. Intact recombinant serovar 3 MB antigen and truncated products, expressed by coupled in vitro transcription and translation of the cloned gene, were immunoprecipitated by both a serovar-specific monoclonal antibody and the serum of a U. urealyticum-infected patient, and these results identified the repeat region of the MB antigen as serovar defining. Resolution of the precise amino acids responsible for specific epitopes and characterization of similar genes in the other serovars should yield reagents useful in elucidating the role of antigen size variants in disease production and the role of specific antibody in protection from ureaplasma disease.

Ureaplasma urealyticum cervical colonization as a marker for pregnancy complications

OBJECTIVES

To determine the clinical significance of cervical colonization with (Ureaplasma urealyticum (Uu) and its possible relationship to pregnancy outcome.

METHODS

Cervical cultures for Uu and serum antibodies to Uu were determined in four groups of pregnant women: (1) 117 women who underwent mid-trimester amniocentesis; (2) 47 women with preterm labor and intact membranes; (3) 34 women with preterm premature rupture of membranes; and (4) a control group of 315 healthy women with normal pregnancies. Statistical methods used were the chi-square and Fisher's exact tests.

RESULTS

A significant increase in the cervical colonization rate with Uu was detected in all study groups (62%, 77% and 74%, respectively) when compared with the control group (42%). Women at mid-trimester of pregnancy with a positive cervical culture and high levels of antibodies, had a higher rate of pregnancy complications than those with a negative culture and absence of antibodies (62 vs. 28%, respectively; P = 0.0006).

CONCLUSION

Cervical colonization with Uu when associated with elevated titers of antibodies to Uu, may serve as a marker for the identification of a subpopulation of women who are at high risk for the development of pregnancy complications.

Ureaplasma urealyticum chorioamnionitis

Controversy reigns over the role of Ureaplasma urealyticum in determining pregnancy outcome. U. urealyticum infection of the chorioamnion is strongly associated with chorioamnionitis (1-3), premature birth (2-4), and perinatal morbidity (4-6). We present 4 cases of U. urealyticum chorioamnionitis and associated morbidity and mortality.

Ureaplasma urealyticum biovar specificity and diversity are encoded in multiple-banded antigen gene

Ureaplasma urealyticum is a commensal organism of the lower genital tract of females, but in a subpopulation of individuals, it can invade the upper genital tract. It is a significant cause of chorioamnionitis and neonatal morbidity and mortality. There are 14 recognized serovars of U. urealyticum; these can be divided into two distinct clusters or biovars. Biovar 1 is composed of serovars 1, 3, 6, and 14, Biovar 2 is composed of serovars 2, 4, 5, 7, 8, 9, 10, 11, 12, and 13. We previously identified a surface antigen, the multiple-banded (MB) antigen, which contains both serovar-specific and cross-reactive epitopes. Genotypic characterization of the C-terminal region of the MB antigen of serovar 3 indicates that serovar specificity and MB antigen size variation reside in that domain. In the present study, we used PCR analysis with primers derived from the serovar 3 MB antigen gene DNA sequence to determine if the MB antigen gene was present in the remaining 13 reference serovars as well as in invasive clinical isolates. The results indicated that not only was the MB antigen gene present in all serovars but that the genes' 5' regions were markers of biovar specificity and diversity. Further analysis of this region should reveal the phylogenetic relationship among serovars of U. urealyticum and, possibly, their invasive potential.

Frequency and significance of isolation of Ureaplasma urealyticum and Mycoplasma hominis from cerebrospinal fluid and tracheal aspirate specimens from low birth weight infants

To investigate the pathogenicity of Ureaplasma urealyticum and Mycoplasma hominis in preterm infants, we conducted a study to determine (1) frequency of isolation from cerebrospinal fluid and tracheal aspirate specimens and (2) clinical outcomes and effect of erythromycin treatment in ureaplasma-colonized infants. From the cerebrospinal fluid of 920 infants, U. urealyticum was isolated from 2 (0.2%) and M. hominis from none. From tracheal aspirate specimens from 224 infants, U. urealyticum was recovered from 37 (17%) and M. hominis from 4 (2%). Demographic characteristics and clinical outcomes were compared in very low birth weight infants (< 1500 gm) who were culture-positive or -negative for U. urealyticum. Although infants with positive results were less mature than their cohorts with negative results, there were no substantive differences in clinical outcomes between the two groups. Initiation of erythromycin treatment of infants with positive ureaplasma culture results at a mean age of 16.4 days did not appear to alter the clinical outcome. We conclude that in preterm infants (1) infection of the cerebrospinal fluid by U. urealyticum is infrequent, (2) ureaplasma organisms are frequently present in tracheal aspirate specimens but do not appear to be related to the presence or the subsequent development of respiratory disease, and (3) initiation of erythromycin treatment at 1 to 3 weeks of age does not alter the clinical course.

Identification of serotype 1-, 3-, and 6-specific antigens of Ureaplasma urealyticum by using monoclonal antibodies

Little is known about the antigens responsible for serotype specificity in Ureaplasma urealyticum. We produced monoclonal antibodies to U. urealyticum serotypes 1, 3, and 6, the serotypes most commonly found in pregnant women, and analyzed serotype-specific antigens for the three serotypes. Clinical isolates belonging to serotype 1, 3, or 6 were tested in immunoblots with these monoclonal antibodies. The immunoblot patterns of these isolates were, in most cases, different from each other as well as from those of the reference strains, indicating a high rate of antigenic variation among U. urealyticum strains.

Reappraisal of the role of endotoxin in the sepsis syndrome

There is strong evidence to implicate endotoxin released from gram negative bacteria in the pathogenesis of the sepsis syndrome and related conditions, but equally compelling data bring the role of endotoxin into doubt. Reappraisal of endotoxin and its release from gram negative bacteria suggests that it is not directly responsible for the complications of sepsis syndrome. Rather, release of endotoxin is a marker for the transition of gram negative organisms to cell-wall-deficient forms (L-forms) that may persist undetected despite antibiotic therapy directed against the parental form. This transition has two consequences in compromised patients: L-forms cause organ failure, and they serve as a sanctuary from which cell-wall-intact revertants may arise.