Association of Ureaplasma urealyticum colonization with chronic lung disease of prematurity: results of a metaanalysis

Detection of microorganisms in the tracheal aspirates of preterm infants by polymerase chain reaction: association of adenovirus infection with bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is recognized as an important cause of morbidity and mortality in preterm infants. Because the role of congenital infections in BPD has been debated, the purpose of this study was to test the hypothesis that detection of infectious agents in tracheal aspirate samples was associated with the development of BPD. Tracheal aspirate samples were obtained within the 1st week of life and screened by polymerase chain reaction for adenovirus, cytomegalovirus, parvovirus, enteroviruses, Ureaplasma urealyticum, Mycoplasma hominis, Mycoplasma pneumoniae, and Chlamydia species. BPD was defined as persistent oxygen dependence at 28 d of age and 36 wk postconceptional age (PCA). Infants that expired before these time points were excluded from statistical analysis. Out of 89 infants studied, at 28 d of life, 13 had expired, 45 had BPD, and 31 had no BPD (controls). At 36 wk PCA, 15 infants expired, 39 still had BPD, and 35 did not. A significant increase in the frequency of adenovirus genome was identified in BPD patients compared with controls, both at 28 d of life (12/45 = 27% versus 1/31 = 3%: p< or =0.01) and at 36 wk PCA (10/39 = 29% versus 2/35 = 6%: p = 0.01). Other microorganisms were rarely detected and not associated with the development of BPD. This is the first study reporting the frequency of detection of adenovirus DNA in tracheal aspirate samples obtained during the 1st week of life from infants with BPD and suggests that prenatal acquisition may be important in the development of BPD.

Role of ureaplasma urealyticum in lung disease of prematurity

AIM

To examine the role of Ureaplasma urealyticum colonisation or infection in neonatal lung disease.

METHODS

Endotracheal aspirates from ventilated infants less than 28 weeks of gestation were cultured for U urealyticum and outcomes compared in infants with positive and negative cultures.

RESULTS

U urealyticum was isolated from aspirates of 39 of 143 (27%) infants. Respiratory distress syndrome (RDS) occurred significantly less often in colonised, than in non-colonised infants (p=0.002). Multivariate logistic regression analysis showed that in singleton infants, ureaplasma colonisation was the only independent (negative) predictor of RDS (OR 0.36; p=0. 02). Both gestational age (OR 0.46; p=0.006) and isolation of U urealyticum (OR 3.0; p=0.05) were independent predictors of chronic lung disease (CLD), as defined by requirement for supplemental oxygen at 36 weeks of gestational age. Multiple gestation was also a major independent predictor of RDS and CLD.

CONCLUSIONS

Colonisation or infection with ureaplasma apparently protects premature infants against the development of RDS (suggesting intrauterine infection). However, in singleton infants, it predisposes to development of CLD, independently of gestational age. Treatment of affected infants after birth is unlikely to significantly improve the outcome and methods are required to identify and treat the women with intrauterine ureaplasmal infection, before preterm delivery occurs.

Mechanisms initiating lung injury in the preterm

Bronchopulmonary dysplasia (BPD)/chronic lung disease occurs primarily in very low birth weight infants (VLBW) often without antecedent severe respiratory distress syndrome. The BPD in these VLBW infants results in less fibrosis than the traditional BPD but the normal process of alveolarization seems to be disrupted. This review develops the thesis that BPD in VLBW infants results from inflammatory mediators interfering with the signaling required for normal late gestational lung development. Proinflammatory mediators may be elevated because of fetal exposure, postnatal infection or by release from preterm lungs ventilated at either low or high lung volumes. The preterm lung is highly susceptible to injury during resuscitation or more chronic mechanical ventilation because the gas volumes/kg body weight of the lungs are small. An understanding of what causes cytokine release and how cytokines influence lung development is necessary to develop targeted therapies to minimize BPD. However, care strategies that minimize inflammation and ventilator-induced lung injury should help decrease BPD.

Genital mycoplasmas stimulate tumor necrosis factor-alpha and inducible nitric oxide synthase production from a murine macrophage cell line

Ureaplasma urealyticum and Mycoplasma hominis, two genital mycoplasmas, are the most common organisms isolated in the perinatal period and both either cause or are associated with poor perinatal outcomes. We speculate that these microbes could increase inflammation by stimulating macrophages to produce tumor necrosis factor-alpha (TNF-alpha) and inducible nitric oxide synthase because of their propensity to interact with the host's immune system. To test this hypothesis, RAW 264.7 cells, a murine macrophage cell line, were coincubated for 16 h with either U. urealyticum or M. hominis, and LPS and sterile broth were used as controls. Lipopolysaccharide (LPS) and both mycoplasmas induced TNF-alpha production, which was concentration-dependent, whereas sterile broth had little effect. TNF-alpha production was not inhibited by the addition of polymyxin B, excluding the possibility of contaminating endotoxin in this effect. Inducible nitric oxide synthase was produced only in the presence of recombinant inteferon-gamma. We conclude that both viable and nonviable U. urealyticum and M. hominis are capable of TNF-alpha induction from murine macrophages and that LPS is not involved in this event. Also, the genital mycoplasmas are capable of stimulating inducible nitric oxide synthase production from murine macrophages. We speculate that the genital mycoplasmas produce perinatal disease by producing proinflammatory mediators by their interaction with inflammatory cells and either induce or act as a catalyst and augment inflammation which in turn leads to a poor pregnancy outcome.

Impact of erythromycin on respiratory colonization of Ureaplasma urealyticum and the development of chronic lung disease in extremely low birth weight infants

BACKGROUND

Chronic lung disease (CLD) is a significant cause of neonatal morbidity and mortality despite advances in neonatal care. Ureaplasma urealyticum colonization of the lower respiratory tract has been associated with CLD, particularly in extremely low birth weight infants. Despite numerous studies demonstrating the pathogenicity of this organism, treatment remains controversial. This study examines neonates colonized with U. urealyticum in the lower respiratory tract and treated with erythromycin, as compared with noncolonized neonates.

METHODS

A prospective cohort study of 124 neonates weighing <1000 g at birth, requiring endotracheal intubation and ventilation. Endotracheal aspirates were cultured for U. urealyticum and conventional bacteria twice weekly for the duration of endotracheal intubation. Infants colonized with U. urealyticum were treated with intravenous erythromycin. Maximal ventilatory requirements, CLD at Day 28 and 36 weeks postconception, duration of ventilation, oxygen dependency and hospital stay were documented.

RESULTS

Twenty-two infants (18%) were identified as being U. urealyticum colonized in endotracheal aspirates. Colonization was significantly associated with younger maternal age, prolonged rupture of membranes, premature labor and vaginal delivery. Of colonized neonates 14% were delivered by cesarean section, with intact membranes. As compared with noncolonized infants, there were no statistically significant differences in chronic lung disease, duration of oxygen therapy or time to discharge.

CONCLUSIONS

Seven published cohort studies of similar high risk populations where U. urealyticum-colonized infants did not receive erythromycin therapy, show a consistent association with CLD (pooled relative risk + 5.21; 95% confidence interval, 2.93 to 9.64). This association was not demonstrated in the current study and adds further weight to the need for a randomized controlled trial to be performed to evaluate this treatment regimen.

Ureaplasma urealyticum and chronic lung disease in very low birth weight infants during the exogenous surfactant era

BACKGROUND

An association between recovery of Ureaplasma urealyticum from the respiratory tract of very low birth weight (VLBW) infants (< or =1500 g) and later chronic lung disease (CLD) was reported by several authors before the routine use of exogenous surfactant (SURF). We sought to assess whether this relation persists in the era of routine SURF.

METHODS

We prospectively studied a cohort of 105 VLBW infants who required mechanical ventilation at < 12 h of age. Tracheal aspirates for U. urealyticum culture were obtained before administration of SURF or antibiotics. Clinicians were unaware of U. urealyticum status. Chest radiographs at 28 days were reviewed by a single pediatric radiologist, blinded to U. urealyticum status. Sample size was predetermined to detect a 30% increase in CLD among those with U. urealyticum recovery from tracheal culture (U. urealyticum-positive) with alpha <0.05 and beta <0.20.

RESULTS

Of the study infants 22 were U. urealyticum-positive and 83 were U. urealyticum-negative. No differences were found between the groups for birth weight, gestational age, gender, inborn, antenatal or postnatal steroid use, SURF therapy, non-U. urealyticum infection, necrotizing enterocolitis, patent ductus arteriosus, intraventricular hemorrhage or cystic periventricular leukomalacia. At 28 days U. urealyticum-positive patients were significantly more likely to have CLD than U. urealyticum-negative [15 of 22 (68%) vs. 30 of 83 (36%); P < 0.02]. The U. urealyticum-positive patients also required significantly longer courses of supplemental oxygen and mechanical ventilation. No significant differences were found for CLD at 36 weeks postconception or duration of hospitalization, although type II error could not be excluded for these secondary endpoints.

CONCLUSIONS

Respiratory U. urealyticum at or shortly after birth remains associated with CLD at 28 days despite routine use of SURF. Controlled trials of anti-Ureaplasma therapy in U. urealyticum-positive VLBWs as soon after birth as possible may determine whether CLD, duration of respiratory support and attendant costs can be decreased.

Respiratory tract colonization with mycoplasma species increases the severity of bronchopulmonary dysplasia

There is controversy regarding the role of mycoplasmas (MP) colonizing the neonatal respiratory tract in the development of bronchopulmonary dysplasia (BPD). To determine the association of respiratory MP colonization and BPD. Retrospective analysis of neonates (26-32 weeks of gestation) intubated for respiratory insufficiency. Tracheal aspirate cultures were obtained for MP if the lung disease was not improving by 7-10 days or there were radiographic changes suggestive of inflammation. Of 63 infants who had tracheal aspirates sent, 17 had positive MP cultures. We found no significant difference in the gestational ages (27.6 +/- 0.4 vs 27.8 +/- 0.2 weeks) or birth weights (1097 +/- 86 vs 997 +/- 42 grams) in MP positive vs negative infants. No differences were noted in antenatal or postnatal steroid use, gender, race, sepsis, RDS, PDA, air leaks, NEC, GER, days on positive pressure ventilation or days on oxygen. There were significantly (p = 0.04) more infants with severe BPD (defined as oxygen requirement at 36 weeks corrected post menstrual age) among MP positive (n = 14; 82%) versus MP negative (n = 25; 54%) infants. Presence of MP in the tracheal aspirates is associated with an increased likelihood of developing severe BPD.

Detection of Ureaplasma urealyticum in endotracheal tube aspirates from neonates by PCR

A PCR-based test was optimized for the detection of Ureaplasma urealyticum from neonatal respiratory specimens, with primers directed against the multiple-banded antigen gene (L. J. Teng, X. Zheng, J. I. Glass, H. Watson, J. Tsai, and G. H. Cassell, J. Clin. Microbiol. 32:1464-1469, 1994). Endotracheal tube aspirates (225) from 103 low-birth-weight neonates (<1,250 g) were taken, when possible, at days 0, 4, and 14 after birth and examined by culture and by PCR. Of 77 specimens positive by either method, 73 were detected by PCR and 60 were detected by culture. Overall, 36% of the neonates were positive for U. urealyticum by either method. Of 16 patients with PCR-positive-culture-negative results, 13 had positive cultures at another sampling point, and one additional patient had a twin with positive cultures. Of 11 patients with day 0 specimens positive by PCR alone, 9 subsequently became culture positive, demonstrating the utility of this test in early detection. Multiple serovars were present in over 50% of positive specimens, with serovars 3 and 14 in combination being most prevalent. The amplicon size generated from the specimen by PCR correctly predicted the biovars isolated in over 85% of positive specimens. Thus, this PCR test was valuable in allowing early detection of U. urealyticum in neonatal respiratory specimens, as well as in providing biovar information.

Ureaplasma urealyticum respiratory tract colonization is associated with an increase in interleukin 1-beta and tumor necrosis factor alpha relative to interleukin 6 in tracheal aspirates of preterm infants

OBJECTIVE

To determine whether Ureaplasma urealyticum respiratory tract colonization in very low birth weight infants during the first week of life is associated with changes in tracheal aspirate concentrations of the cytokines interleukin 1-beta (IL-1-beta), tumor necrosis factor alpha (TNF-alpha) and IL-6.

METHODS

Infants with birth weights < or =1250 g were prospectively enrolled. Samples were obtained from the endotracheal tube or nasopharynx on Day 1 and again between Days 7 and 10 for U. urealyticum culture. The concentrations of IL-1-beta, TNF-alpha and IL-6 were measured in tracheal aspirate samples by enzyme-linked immunosorbent assay.

RESULTS

There were 18 positive cultures for U. urealyticum from 15 of 96 infants (15.6%). IL-1-beta in tracheal aspirates expressed as concentration per volume or as a ratio of IL-1-beta to IL-6 were 7- and 14.9-fold higher, respectively, in Ureaplasma-positive infants than in Ureaplasma-negative infants (P < 0.05). The TNF-alpha/IL-6 ratio was 18.9 and 15.5 times higher in the Ureaplasma-positive aspirates than in the Ure aplasma-negative aspirates on Day 1 and Days 7 to 10 (P < 0.05). Concentrations of IL-1-beta and TNF-alpha were significantly correlated on Day 1 and Days 7 to 10. Although there was no clinical association demonstrated between U. urealyticum colonization and the development of bronchopulmonary dysplasia (BPD) in this study, infants who developed BPD had significantly higher IL-1-beta concentrations and ratios of IL-1-beta to IL-6 in Day 1 aspirates than infants who did not develop BPD. Conclusions. Isolation of U. urealyticum from the respiratory tract is associated with increased IL-1-beta concentrations and IL-1-beta-IL-6 ratios on Day 1 and increased TNF-alpha-IL-6 ratios on Days 1 and 7 to 10 in tracheal aspirates of colonized infants. Infants who developed BPD had higher IL-1-beta concentrations and IL-1-beta-IL-6 ratios, suggesting that these may be early markers of lung inflammation.

Vaginal Ureaplasma urealyticum colonization: influence on pregnancy outcome and neonatal morbidity

The effects of Ureaplasma urealyticum colonization on pregnancy and neonatal outcome was prospectively studied in women with impending term or preterm delivery. One hundred and seventy women colonized with U. urealyticum as the only pathogenic microorganism and 83 women with negative cultures were enrolled for study. Compared to the controls, U. urealyticum colonization was associated with a significantly increased rate of amnionitis (2% vs 35%; p < 0.001), chorioamnionitis (0% vs 10%; p < 0.05), premature rupture of membranes (12% vs 35%; p < 0.001) and preterm delivery (10% vs 41%; p < 0.001). The rate of vertical transmission ranged from 38% in term infants to 95% in very low birth weight infants. U. urealyticum colonization at birth was associated with an increased risk for the development of respiratory distress syndrome (9% vs 51%), intraventricular hemorrhage (1% vs 7%) and bronchopulmonary dysplasia (4% vs 17%) in very low birth weight infants (< 1500 g). It is concluded that maternal U. urealyticum colonization is associated with amnionitis, chorioamnionitis and preterm delivery, and that tracheal colonization with U. urealyticum increases the risk for respiratory and neurological complications in very low birth weight infants.

Ureaplasma urealyticum and pulmonary outcome in a neonatal intensive care population

OBJECTIVE

To determine whether the presence of Ureaplasma urealyticum in the respiratory tracts of very low birth weight infants is associated with increased risk of pneumonia, radiographic evidence of severe bronchopulmonary dysplasia during the second or third week of life (precocious) and oxygen dependency at 36 weeks of corrected postnatal gestational age.

METHODS

From October, 1993, to January, 1996, all infants who met the following entry criteria were enrolled in the study: birth weights < or = 1500 g; admission to the NICU within 24 h after birth; evidence on admission of respiratory distress; and no prior antibiotic treatment. Infants were cultured for mycoplasmas, viruses, chlamydiae and aerobic and anaeroic bacteria.

RESULTS

Ninety-four critically ill newborns constituted our study cohort. Within 7 days of birth more infants with U. urealyticum infection showed radiographic features of pneumonia (53.1%, 25 of 47) than infants without U. urealyticum infection (21.2%, 10 of 47). Infants with U. urealyticum were more likely to have radiographic evidence of precocious bronchopulmonary dysplasia than those without this isolate (22.5%, 9 of 40 vs. 2.3%, 1 of 42). The relative risk of oxygen dependency at 36 weeks of corrected age in U. urealyticum-positive infants was 11.0 times that in U. urealyticum-negative infants (95% confidence interval, 1.6 to 75.5). Association of U. urealyticum and chronic lung disease at this age was not weakened after adjustments were made in a multivariate analysis for other significant risk factors including gestational age and presence of a patent ductus arteriosus.

CONCLUSIONS

Isolation of U. urealyticum from respiratory tracts is associated with radiographic changes compatible with pneumonia within 7 days of birth, precocious bronchopulmonary dysplasia and severe pulmonary outcome.

Role of Ureaplasma urealyticum and Chlamydia trachomatis in development of bronchopulmonary dysplasia in very low birth weight infants

OBJECTIVE

To investigate the relationship between Ureaplasma urealyticum and Chlamydia trachomatis colonization of the very low birth weight infant and the development of bronchopulmonary dysplasia (BPD).

METHODS

Endotracheal and/or nasopharyngeal aspirates and clinical data were obtained prospectively from 108 infants with a birth weight of < 1501 g and analyzed for U. urealyticum and C. trachomatis by culture and polymerase chain reaction (PCR).

RESULTS

U. urealyticum was detected by culture in 40 (37%) infants and by PCR in 49 (45%) infants on at least one occasion. BPD was present at 28 days in 26 of 40 (65%) U. urealyticum culture-positive infants and 39 of 68 (57%) culture-negative infants (relative risk (RR) 1.13, 95% confidence interval 0.83 to 1.54; P = 0.538). BPD was present at 28 days in 34 of 49 (69%) U. urealyticum PCR-positive infants and in 31 of 59 (53%) PCR-negative infants (RR 1.32, 95% confidence interval 0.97 to 1.79; P = 0.135). At 36 weeks postconceptional age culture-positive or PCR-positive infants were at no greater risk of BPD than infants with negative results (RR = 1.02, P = 0.92 and RR = 1.2, P = 0.523, respectively). In addition the presence of U. urealyticum was not associated with any significant difference in the length of hospital stay, days of ventilation, days of oxygen supplementation, birth weight or gestational age. C. trachomatis was detected in only 2 infants.

CONCLUSION

C. trachomatis was found infrequently in the airways of premature very low birth weight infants. U. urealyticum was frequently detected but its presence was not significant with regard to development of BPD, duration of ventilatory support, oxygen dependency and length of hospital stay.

Neonatal airway colonization with gram-negative bacilli: association with severity of bronchopulmonary dysplasia

BACKGROUND

Airway colonization with Gram-negative bacilli (GNB) and Gram-positive cocci (GPC) is common in mechanically ventilated neonates. Whether GNB are related to nosocomial bloodstream infection (BSI) and/or to the severity of bronchopulmonary dysplasia (BPD) is unknown.

METHODS

We prospectively examine this relationship using a cohort design. Data from 260 < or = 1250-g birth weight inborn infants (1991 to 1995) intubated > or = 2 weeks included 917 serial tracheal cultures and 583 blood cultures. The severity of BPD was assessed by duration of mechanical ventilation, oxygen dependency at 36 weeks of postconceptional age and the use of home oxygen supplementation.

RESULTS

After 2 weeks of ventilation, 80% of the infants were colonized with GPC (Staphylococus epidermidis and Staphylococcus haemolyticus in 90% of the cases). Superimposed on 36% of these infants was GNB airway colonization with Klebsiella pneumoniae (25%), Enterobacter cloacae (25%), Escherichia coli (25%), Pseudomonas aeruginosa (10%), Serratia marcescen (10%), Acinetobacter baumannii and Haemophilus influenzae (5%). Comparison between 174 GPC- and 86 GNB-colonized infants showed that demographics, birth weight, gestational age, perinatal risk factors and mortality were similar. Fifteen percent of GNB-colonized infants developed BSI caused by GNB and 14% developed BSI caused by GPC. No significant temporal relationship between airway colonization and BSI was noted. GNB infants were ventilated longer and required oxygen at 36 weeks of postconceptional age and home oxygen supplementation twice as often as infants colonized only with GPC. GNB colonization was a predictor of severe BPD after controlling for ventilation. Ureaplasma colonization occurred in 28% of GNB-colonized and 33% of noncolonized infants and was not a predictor of BPD severity.

CONCLUSION

GNB airway colonization creates a moderate risk for BSI. Antibiotic treatment does not regularly eradicate GNB. GNB airway colonization is associated with severe BPD, but further studies will be necessary before therapeutic efforts to eradicate GNB from the airways should be undertaken.

Randomized controlled trials and systematic reviews: a foundation for evidence-based perinatal medicine

The objective of this paper is to introduce the reader to clinical research methodologies and to illustrate how randomized controlled trials (RCTs) and systematic reviews provide a solid foundation for evidence-based perinatal practice. Relevant references were critically appraised for validity and usefulness. Random allocation is of utmost importance to avoid bias. There are thousands of reported perinatal RCTs. Systematic review techniques allow clinicians to assess the effectiveness of perinatal interventions. The application of the results of systematic reviews to perinatal practice is increasing. RCTs and systematic reviews provide the most valid results on which to build an evidence-based perinatal practice. A major challenge for perinatal researchers is the development of innovative means of communication. This assures that the evidence for an effective intervention is timely implemented. Consumers of care should be encouraged to actively participate in the design, execution and dissemination of perinatal research.