Microbial invasion of the amniotic cavity at birth is associated with adverse short-term outcome of preterm infants

Chorioamnionitis induces changes in ovine pulmonary endogenous epithelial stem/progenitor cells in utero

BACKGROUND

Chorioamnionitis, an intrauterine infection of the placenta and fetal membranes, is a common risk factor for adverse pulmonary outcomes in premature infants including BPD, which is characterized by an arrest in alveolar development. As endogenous epithelial stem/progenitor cells are crucial for organogenesis and tissue repair, we examined whether intrauterine inflammation negatively affects these essential progenitor pools.

METHODS

In an ovine chorioamnionitis model, fetuses were intra-amniotically exposed to LPS, 2d or 7d (acute inflammation) before preterm delivery at 125d of gestation, or to intra-amniotic Ureaplasma parvum for 42d (chronic inflammation). Lung function, pulmonary endogenous epithelial stem/progenitor pools, and downstream functional markers were studied.

RESULTS

Lung function was improved in the 7d LPS and 42d Ureaplasma groups. However, intrauterine inflammation caused a loss of P63+ basal cells in proximal airways and reduced SOX-9 expression and TTF-1+ Club cells in distal airways. Attenuated type-2 cell numbers were associated with lower proliferation and reduced type-1 cell marker Aqp5 expression, indicative for impaired progenitor function. Chronic Ureaplasma infection only affected distal airways, whereas acute inflammation affected stem/progenitor populations throughout the lungs.

CONCLUSIONS

Acute and chronic prenatal inflammation improve lung function at the expense of stem/progenitor alterations that potentially disrupt normal lung development, thereby predisposing to adverse postnatal outcomes.

IMPACT

In this study, prenatal inflammation improved lung function at the expense of stem/progenitor alterations that potentially disrupt normal lung development, thereby predisposing to adverse postnatal outcomes. Importantly, we demonstrate that these essential alterations can already be initiated before birth. So far, stem/progenitor dysfunction has only been shown postnatally. This study indicates that clinical protocols to target the consequences of perinatal inflammatory stress for the immature lungs should be initiated as early as possible and ideally in utero. Within this context, our data suggest that interventions, which promote function or repair of endogenous stem cells in the lungs, hold great promise.

Association between maternal cervicovaginal swab positivity for Ureaplasma spp. or other microorganisms and neonatal respiratory outcome and mortality

OBJECTIVE

We investigated the association between maternal cervicovaginal cultures, its antibiotic treatment, and neonatal outcome.

STUDY DESIGN

This retrospective cohort study enrolled 480 neonates born prior to 32 weeks' gestation. They were divided into groups according to maternal cervicovaginal culture results. Multivariate logistic regression analysis was used to predict neonatal outcome based on maternal culture results, adjusted for perinatal risk factors and neonatal morbidities.

RESULT

Maternal cervicovaginal Ureaplasma colonization was independently associated with bronchopulmonary dysplasia at 36 weeks (BPD) (OR 8.34; 95% CI 1.21-57.45). In neonates with and without maternal cervicovaginal Ureaplasma colonization BPD occurred in 12.3% and 3.8%, respectively. Maternal colonization with other microorganisms was associated with a higher neonatal mortality (p = 0.002), lower gestational age (p = 0.026), and birth weight (p = 0.036).

CONCLUSIONS

This study underscores the role of the maternal cervicovaginal microbiome as a predictor of neonatal outcome. Cervicovaginal Ureaplasma colonization seems not to be an innocent bystander in the multifactorial etiology of BPD.

Prenatal infection with Mycoplasma pulmonis in rats exaggerates the angiotensin II pressor response in adult offspring

Exposure to different stressors in utero is linked to adult diseases such as obesity and hypertension. In this study, the impact of prenatal infection (PNI) on adult body weight and cardiovascular function was evaluated using a naturally occurring rodent pathogen, Mycoplasma pulmonis (MP). Pregnant Sprague-Dawley rats were infected with MP on gestational day 14 and gave birth naturally. Adult PNI offspring weighed more than controls, but resting mean arterial pressure (MAP) was unchanged. Subcutaneous injection of angiotensin II (10 μg/kg) elicited a rise in MAP that was greater in both male and female PNI offspring compared with controls (P < 0.03). The accompanying reflex bradycardia was similar to the controls, suggesting that PNI induced baroreflex dysfunction. Subcutaneous nicotine administration, a potent cardiorespiratory stimulus, also elicited a transient rise in MAP that was generally greater in the PNI group, but the change in MAP from baseline was only significant in the PNI females compared with controls (P < 0.03). Elevated body weight and cardiovascular reactivity in the PNI offspring was associated with an increase in the ratio of hypothalamic corticotrophin-releasing hormone receptors type 1 to type 2 gene expression in both sexes compared with controls. These findings support previous studies demonstrating that PNI induces alterations in cardiovascular function and body weight. Yet, unlike previous studies utilizing other models of PNI (e.g., endotoxin), MP PNI did not induce resting hypertension. Thus, our study provides a foundation for future studies evaluating the cardiovascular risks of offspring exposed to microbial challenges in utero.

The diagnostic performance of the beta-glucan assay in the detection of intra-amniotic infection with Candida species

INTRODUCTION

A bioassay based on the detection of beta-glucan, a constituent of the cell wall of fungi, has been successfully used to diagnose fungal infections in a variety of biological fluids but not yet in the amniotic fluid.

OBJECTIVE

To determine the diagnostic performance of a beta-glucan bioassay in the detection of Candida species in the amniotic fluid of women who either did or did not have an intrauterine contraceptive device (IUD) in place during an episode of spontaneous preterm parturition.

METHODS

The study population comprised women who had a singleton pregnancy without congenital or chromosomal abnormalities, who experienced preterm labor or preterm prelabor rupture of the fetal membranes, and who underwent a transabdominal amniocentesis for clinical indications. Samples of amniotic fluid were cultured for aerobic and anaerobic bacteria, genital mycoplasmas, and Candida species, and assayed for beta-glucan, using the (1→3)-beta-d-glucan-specific Limulus amebocyte lysate test (beta-glucan assay) in all cases. Amniotic fluid interleukin (IL)-6 assay results were also available for all cases. The beta-glucan assay takes about 1 hour to run: a concentration >80 pg/mL was considered positive for fungi. Sterile intra-amniotic inflammation of the amniotic cavity was defined by the presence of an amniotic fluid IL-6 concentration ≥2.6 ng/mL and a negative amniotic fluid culture.

RESULTS

(1) One hundred ninety-seven (197) women met the study criteria, of whom 58 (29.4%) had an IUD in place; (2) 20 (10.2%) women had a culture of proven intra-amniotic Candida species-related infection, 19 of whom had a positive beta-glucan assay [sensitivity, 95% (19/20; 95% confidence interval (CI): 75.1-99.9%)]; and (3) the specificity of the beta-glucan assay was 75.1% [133/177; 95% CI: 68.1-99.9%]. It was affected by the presence of nonfungal intra-amniotic infections and an IUD, but not by the presence of sterile intra-amniotic inflammation, and there was a significant interaction between the presence of an IUD and nonfungal intra-amniotic infections (estimated for the interaction effect = 2.1923, p value =.026). The assay's specificity was reduced when nonfungal intra-amniotic infections were diagnosed but only in women who did not have an IUD. Among women without an IUD, the assay's specificity was 91.4% (117/128); it was 93% (106/114) for those without intra-amniotic infection, and 78.6% (11/14) for those with a nonfungal intra-amniotic infection; the difference was not significant (p = .09). Among women with an IUD, the assay's specificity was 32.7% (16/49); 42.9% (9/21) for those with a nonfungal intra-amniotic infection; and 25% (7/28) for those without intra-amniotic infection; and the difference was significant (p = .03).

CONCLUSIONS

The beta-glucan assay is a sensitive, rapid, point-of-care test used to diagnose intra-amniotic Candida species-related infection, and it has a high specificity in pregnant women who did not have an IUD in place.

Impact of gestational nicotine exposure on intrauterine and fetal infection in a rodent model

We investigated the interaction between prenatal nicotine exposure and intrauterine infection using established rat models. Beginning at gestation day (GD) 6, dams were continuously infused with either saline or 6 mg/kg/day nicotine (Nic). At GD 14, dams received either sterile broth or 10⁵ colony-forming units Mycoplasma pulmonis (MP), resulting in four treatment groups: control (4 dams, 33 fetal units); MP only (5 dams, 55 fetal units); Nic only (5 dams, 61 fetal units), and Nic + MP (7 dams, 82 fetal units). At GD 18, nicotine exposure significantly increased (P ≤ 0.02) the percentage of amniotic fluids and fetuses infected by MP but did not impact colonization rates of maternal sites. Nicotine exposure significantly reduced the numbers of MP in the placenta required for high microbial loads (≥10⁴ color-changing units) in the amniotic fluid (P < 0.01). Fetal inflammatory response lesions were most extensive in the Nic only and Nic + MP groups (P < 0.0001). Control and MP only placentas were interleukin (IL)10-dominant, consistent with an M2/Th2 environment. Placentas exposed to nicotine shifted to a neutral environment, with equivalent levels of interferon gamma (IFNG) and IL10. Both IL6 and tumor necrosis factor (TNF) levels in amniotic fluid were highly elevated when both nicotine and infection were present. Our study suggests that prenatal exposure to nicotine increases the risk for intrauterine infection, lowers the infectious dose required to breach the placental barrier and infect the amniotic fluid and fetus, and alters the pathology and inflammatory profile associated with maternal and fetal sites.

The relationship between the intensity of intra-amniotic inflammation and the presence and severity of acute histologic chorioamnionitis in preterm gestation

OBJECTIVE

Acute histologic chorioamnionitis (HCA) is associated with an increased risk of perinatal mortality and morbidity. The purpose of this study was to determine the relationship between the intensity of intra-amniotic inflammation (IAI) and the severity of acute HCA in preterm gestation.

METHODS

The relationship between the intensity of IAI and the presence and severity of acute HCA was examined in 412 patients with singleton gestations who delivered within 120 h of transabdominal amniocentesis. The concentration of amniotic fluid (AF) matrix metalloproteinase (MMP)-8 was assayed to determine the presence and intensity of IAI. Acute HCA was defined as the presence of inflammatory change in any tissue samples according to the criteria previously reported. The total grade of acute HCA was used to determine the severity of HCA.

RESULTS

(1) Patients with IAI had a significantly higher rate of acute HCA than those without IAI [76.9% (133/173)] versus 20.9% (50/239), p < 0.001]. The AF MMP-8 concentration was significantly higher in patients with acute HCA than in those without acute HCA (median [range]; 188.3 ng/ml [0.3-6142.6] versus 1.8 ng/ml [0.3-2845.5], p < 0.001); (2) Of 183 patients with acute HCA, the AF MMP-8 concentration was positively correlated with the severity of acute HCA (p < 0.001).

CONCLUSIONS

AF MMP-8 concentration was not only a predictor of the presence of acute HCA, but its concentration also correlated with the severity of acute HCA. The higher the intensity of IAI, the worse the degree of acute HCA in preterm gestation.

Infection and smoking are associated with decreased plasma concentration of the anti-aging protein, α-klotho

OBJECTIVE

The objective of this study was to determine whether maternal plasma concentrations of soluble α-klotho are different between women with microbial invasion of the intra-amniotic cavity (MIAC) and those without MIAC among preterm labor and intact membranes (PTL) or preterm prelabor rupture of membranes (pPROM).

METHODS

A cross-sectional study was conducted to include women in the following groups: i) PTL with MIAC (n=14); ii) PTL without MIAC (n=79); iii) pPROM with MIAC (n=30); and iv) pPROM without MIAC (n=33). MIAC was defined as a positive amniotic fluid culture for microorganisms (aerobic/anaerobic bacteria or genital mycoplasmas). Amniotic fluid samples were obtained within 48 h of maternal blood collection. Plasma concentration of soluble α-klotho was determined by ELISA.

RESULTS

i) The median plasma concentration (pg/mL) of soluble α-klotho was significantly lower in patients with MIAC than in those without MIAC (787.0 vs. 1117.8; P<0.001). ii) Among patients with PTL, those with MIAC had a lower median plasma concentration (pg/mL) of soluble α-klotho than those without MIAC (787.0 vs. 1138.9; P=0.007). iii) Among patients with pPROM, those with MIAC had a lower median plasma concentration (pg/mL) of soluble α-klotho than those without MIAC (766.4 vs. 1001.6; P=0.045). iv) There was no significant difference in the median plasma concentration of soluble α-klotho between PPROM without MIAC and PTL without MIAC (1001.6 pg/mL vs. 1138.9 pg/mL, respectively; P=0.5). v) After adjustment for potential confounders (maternal age, tobacco use, gestational age at venipuncture), soluble α-klotho remained significantly associated with MIAC (P=0.02); and vi) Among patients without MIAC, smoking was significantly associated with a lower median plasma concentration soluble α-klotho than in non-smokers (794.2 pg/mL vs. 1382.0 pg/mL, respectively; P<0.001); however, this difference was not observed in patients with MIAC.

CONCLUSIONS

Intra-amniotic infection occurring at preterm gestations (regardless of membrane status) was associated with a decrease in maternal plasma concentrations of soluble α-klotho. Moreover, among patients without infection, the plasma concentration of α-klotho was lower in smokers.

In utero exposure to Ureaplasma spp. is associated with increased rate of bronchopulmonary dysplasia and intraventricular hemorrhage in preterm infants

AIMS

We determined the association between short-term neonatal morbidities, such as bronchopulmonary dysplasia (BPD) and intraventricular hemorrhage (IVH), and Ureaplasma spp. in amniotic fluid, placental and amniotic membrane of preterm infants.

METHODS

This study enrolled 257 patients who were born by cesarean section at <34 weeks' gestation. Patients were divided into two groups according to detection of Ureaplasma spp. by culture-based and/or polymerase chain reaction (PCR) techniques.

RESULTS

Significant differences were observed between both groups for all IVH (P=0.032) and IVH grades III or IV (P=0.013), as wells as for BPD [odds ratio (OR) 5.46, 95% confidence interval (CI) 2.02-14.77], oxygen requirement at 28 days postnatal age (OR 1.93, 95% CI 1.00-3.70), and for death between 28 days and 36 postmenstrual weeks or BPD (OR 4.20, 95% CI 1.77-9.96). Ureaplasma spp. was a significant predictor (P<0.001) of BPD after correcting for birth weight (P=0.003) and positive pressure ventilation (P=0.001).

CONCLUSIONS

In our study population Ureaplasma spp. was associated with BPD and IVH in preterm infants even after adjustment for multiple risk factors.

HISTOLOGICAL CHORIOAMNIONITIS: CURRENT CONCEPTS OF DIAGNOSIS, CLASSIFICATION AND CLINICAL SIGNIFICANCE

Interest in the clinical associations between maternal intrapartum fever and adverse neonatal outcome has been longstanding, with publications of a relationship between maternal fever and cerebral palsy dating from the 1950s. Further recognition of the associations between either clinically or histologically characterised chorioamnionitis, ascending infection and neonatal wellbeing followed, with numerous reports in the 1960s and 70s, particularly as the neonatal significance of group B streptococcal infections became apparent. Similarly, with the systematic introduction of diagnostic light microscopy into clinical medicine, chorioamnionitis (inflammation of the placental membranes) and funisitis (inflammation of the umbilical cord) were recognised as distinct histological entities, with increasing recognition that the aetiology was likely to be infective. There are numerous texts discussing in detail the pathogenesis and histological features of chorioamnionitis and funisitis. The aim of this review is to provide an overview of the salient associated issues for clinical practitioners and to highlight areas of ongoing uncertainty and recent developments in understanding.

Detection of Ureaplasma urealyticum and Ureaplasma parvum in amniotic fluid: association with pregnancy outcomes

OBJECTIVE

Ureaplasma urealyticum is one of the organisms most frequently isolated from the amniotic fluid of women with adverse pregnancy. The prevalence of U. urealyticum and U. parvum on samples of amniotic fluid from healthy asymptomatic pregnant women, and whether its detection is associated with P-PROM or preterm birth was investigated.

METHODS

Transabdominal amniotic fluid obtained from 121 asymptomatic women at 16-20 weeks of gestation were tested for the detection of Ureaplasma spp., using a selective culture media. A Multiplex-Polymerase Chain Reaction (PCR) method was used for the identification of U. parvum and U. urealyticum. Pregnancy outcomes were obtained after the completion of all testing.

RESULTS

Ureaplasma spp. was not identified by culture, but was identified by Multiplex-PCR in four subjects, two corresponding to U. parvum and two to U. urealyticum. The women positive to ureaplasmas had normal labor, and babies born from infected-ureaplasmas pregnant women had normal weight birth. Preterm birth with intact membranes was documented in four women, all negative to ureaplasmas, but associated with gestational hypertension, lost of liquids and low weight birth.

CONCLUSIONS

Multiplex-PCR method was more sensitive that culture in detecting ureaplasma organism in amniotic fluid. No association of ureaplasmas with pregnancy outcomes was found.

The bacterial load of Ureaplasma parvum in amniotic fluid is correlated with an increased intrauterine inflammatory response

Ureaplasma spp. are the most frequently isolated microorganisms inside the amniotic cavity and have been associated with spontaneous abortion, chorioamnionitis, premature rupture of the membranes (PROM), and preterm labor (PL). We analyzed 118 samples from amniotic fluid of preterm infants before 34 weeks of gestation by quantitative polymerase chain reaction (qPCR). Bacterial load, Ureaplasma biovar discrimination (Ureaplasma urealyticum and Ureaplasma parvum), and the level of inflammation were correlated with short-term clinical outcome. U. parvum was the predominant biovar, and increased bacterial load was significantly linked to histologic chorioamnionitis, PROM + PL, early-onset sepsis, and bronchopulmonary dysplasia. Furthermore, there was a positive correlation between the amount of U. parvum and the magnitude of inflammatory response inside the amniotic cavity observed by elevated interleukin 8 levels. We postulate that the bacterial load of Ureaplasma spp. measured by qPCR should be determined in studies investigating the potential clinical impact of intrauterine Ureaplasma spp. on the outcome of preterm infants.

Widespread microbial invasion of the chorioamniotic membranes is a consequence and not a cause of intra-amniotic infection

Acute chorioamnionitis is a response to amniotic fluid (AF) infection. However, it remains unclear whether substantial bacterial propagation in the chorioamniotic membranes (CAMs) precedes microbial invasion of the amniotic cavity (MIAC), which is inconsistent with characteristic 'amniotropic neutrophil migration' in acute chorioamnionitis. This study was performed to determine whether CAMs have widespread bacterial infection during MIAC and whether bacteria normally colonize CAMs. AF pellets and CAMs from the following groups were studied: group 1, patients with positive (n=18) or negative (n=22) AF cultures; group 2, patients with or without acute chorioamnionitis in which the amnion and chorion were studied separately (n=60); and group 3, patients at term who underwent a cesarean delivery (n=30). SYTO 9/propidium iodide fluorescent staining and fluorescent in situ hybridization for 16S rRNA were performed. Real-time quantitative PCR for 16S rDNA and PCR for genital mycoplasmas were also conducted. Bacteria were more frequently detected in AF than in CAMs of patients with positive AF culture (100 vs. 33%; P<0.0001). Bacteria were detected more frequently in CAMs as the severity of chorioamnionitis increased (P<0.01). The median 16S rRNA gene copy number in the amnion was significantly greater than in the chorion (group 2; P<0.0001). Bacteria were not detected in CAMs or AF in women at term before labor (group 3). A fraction of patients with chorioamnionitis or MIAC did not have bacteria in CAMs. Collectively, the findings herein indicate that MIAC does not follow widespread infection of CAMs, but precedes it. We propose a model of MIAC: the initial stage is intra-amniotic bacterial invasion through a discrete region of the CAMs, followed by intra-amniotic proliferation, and bacterial invasion of CAMs primarily extends from the amniotic fluid. This study emphasizes the importance of assessing the intra-amniotic compartment for diagnosis and treatment of preterm birth.

Perinatal correlates of Ureaplasma urealyticum in placenta parenchyma of singleton pregnancies that end before 28 weeks of gestation

OBJECTIVES

The purpose of this work was to examine the relationship between Ureaplasma urealyticum in the placenta and perinatal outcomes in extreme preterm deliveries and to explore the influence of bacteria coinfection on perinatal outcomes in U urealyticum-positive placentas.

METHODS

Under sterile conditions, a piece of chorion from 866 singleton deliveries before 28 weeks' gestation was obtained and flash frozen. The tissue was later homogenized and cultured for Ureaplasma and bacteria. Placentas were also examined histologically. Maternal and neonatal data were obtained prospectively. Each infant had 3 sets of cranial ultrasound scans between days 1 to 4, 5 to 14, and between day 15 and 40th week postconceptional age. Cranial ultrasound findings were by consensus of 2 or 2 of 3 sonologists.

RESULTS

U urealyticum was recovered from 6% and bacteria from 47%; 47% of placentas had no bacteria detectable. Sixty-seven percent of Ureaplasma-positive placentas also harbored bacteria. Placentas that harbored U urealyticum only were more likely than sterile placentas to be associated with a higher prevalence of preterm labor and preterm premature rupture of membranes, as well as umbilical cord, fetal vessel, membrane, and parenchymal inflammation and to predict intraventricular hemorrhage and echolucent brain lesions. Placentas that harbored U urealyticum only were similar to placentas that harbored bacteria only. Recovery of U urealyticum and bacteria from same placenta did not enhance the differences between placentas with U urealyticum alone and sterile placentas. Recovery of U urealyticum only was not associated with a higher risk of death before day 7 of life.

CONCLUSIONS

The presence of U urealyticum in placental parenchyma before 28 weeks is associated with increased risk of preterm labor and delivery, higher risk of fetal and maternal inflammation, and increased risk of intraventricular hemorrhage and echolucent brain lesions but not of early neonatal death.

Intrauterine infection with Ureaplasma species is associated with adverse neuromotor outcome at 1 and 2 years adjusted age in preterm infants

AIMS

To evaluate the association between the presence of bacterial pathogens in the amniotic cavity at the time of preterm delivery and neuromotor outcome at two years adjusted age in preterm infants born at < or =33 weeks' gestation.

METHODS

The cohort included 114 preterm infants, born at 23-33 weeks' gestation to mothers with amniotic cavity cultures taken during cesarean delivery who were subsequently evaluated at 24.0+/-1.1 months corrected age with the Bayley Scales of Infant Development II and a standardized neurologic examination.

RESULTS

A group of 67 infants with negative amniotic cavity cultures was compared to 47 infants with positive amniotic cavity cultures (Ureaplasma urealyticum (Uu) in 32 cases and other bacteria in 15 cases). Patients with positive amniotic cavity cultures had a significantly higher risk for an adverse psychomotor development index (PDI) score (OR 3.1, CI 1.3-7.1), an abnormal neurologic outcome (OR 4.8, CI 1.7-13.8), and a higher probability for diagnosis of cerebral palsy (OR 4.8, CI 1.4-16.4) at two years compared to patients with negative culture results. Isolation of Uu at birth was associated with a particular adverse outcome of preterm infants.

CONCLUSIONS

Isolation of pathogens from the amniotic cavity at birth is significantly associated with abnormal PDI and adverse neuromotor outcome in preterm infants, irrespective of gestational age and birthweight.

Hematogenous infection of Sprague-Dawley rats with Mycoplasma pulmonis: development of a model for maternal and fetal infection

OBJECTIVES

The specific objective of this study was to conduct a dose response experiment with Mycoplasma pulmonis in Sprague-Dawley rats to develop a reproducible animal model of maternal and fetal infection that would provide a versatile mechanism to address the innate fetal immune response during intrauterine infection.

STUDY DESIGN

Pregnant rats were infected intravenously at gestation day 14 with 0 (control), 10(1), 10(3), 10(5), and 10(7) colony forming units of M. pulmonis and necropsied at gestational day 18. Quantitative culture of maternal and fetal tissues as well as histopathologic examination of the placenta were performed.

RESULTS

We have characterized a rat model of maternal and fetal infection that can be manipulated by alteration of infectious dose. Colonization of Sprague-Dawley rat dam and fetal tissues by M. pulmonis occurred in a dose-dependent manner after intravenous inoculation (P < .001). Placental lesion severity increased with infection dose (P = .0001). The minimum threshold dose required to establish infection of the dam and fetus was at least 10(3) colony forming units, with consistent colonization of maternal and fetal tissues achieved only with 10(7) colony forming units. In some instances, rat fetal tissues could be colonized in the absence of concomitant amniotic fluid colonization. Interestingly, there appeared to be a predilection for colonization of the reproductive tissues.

CONCLUSIONS

In the Sprague-Dawley rat, the infection rate of both the dam and fetus can be controlled by the inoculum dose. Our data support the concept that hematogenous spread of M. pulmonis to the rat fetus can occur without amniotic fluid infection and suggest that the fetus itself can potentially seed the amniotic fluid with microorganisms. Importantly, manipulation of both the route of infection as well as infection dose provide a reproducible way to study both maternal and fetal immune response to infection during pregnancy.

Experimental amniotic fluid infection in sheep: effects of Ureaplasma parvum serovars 3 and 6 on preterm or term fetal sheep

OBJECTIVE

The objective of the study was to determine the effects in late gestation of Ureaplasma parvum serovar 3 colonization and the effects, preterm, of U. parvum serovar 6.

STUDY DESIGN

Ewes received an intraamniotic (i.a.) injection of U. parvum serovar 6 (20 x 10(6) colony-forming units [cfu]; n = 9), U. parvum serovar 3 (20 x 10(3) cfu; n = 6), vehicle (n = 10), or saline (n = 4) on day 80 of pregnancy (d). The lambs were delivered at 125 d (U. parvum serovar 6, n = 9; saline or media controls, n = 9) or 145 d (U. parvum serovar 3, n = 6; media controls, n = 5) for assessment of inflammation and lung maturation.

RESULTS

I.a. ureaplasmas caused histologic chorioamnionitis but not preterm delivery. Fetal lung epithelium was colonized with ureaplasmas at both gestational ages, and pulmonary interleukin-8 levels had doubled in the ureaplasma-colonized animals, compared with the controls at 145 d. Surfactant levels in bronchoalveolar lavage fluid had increased 8-fold and 2.5-fold at 125 and 145 d, respectively, after ureaplasma injection.

CONCLUSION

Fetal lung inflammation and altered development accompanies ureaplasma colonization, regardless of age at delivery.

Amnionitis with Ureaplasma urealyticum or other microbes leads to increased morbidity and prolonged hospitalization in very low birth weight infants

OBJECTIVE

To investigate the influence of culture proven intrauterine infection on preterm morbidity and to test the effect of antimicrobial treatment.

METHODS

Retrospective cohort study conducted between October 1997 and February 2001 in patients with preterm premature rupture of membranes or preterm labor. Vaginal swabs were sampled and amniocentesis for microbiologic culture of the amniotic fluid was performed. Patients with Ureaplasma urealyticum in the amniotic fluid were treated with josamycin. Infants were followed post partum according to birth weight, gestational age, APGAR score and infant morbidity.

RESULTS

In 49 eligible patients, 40% of cultures were positive, 22% for Ureaplasma urealyticum, 12% for other bacteria and 6% for candida. Children of mothers with positive amniotic fluid cultures had significantly lower gestational ages (26+4 weeks for Ureaplasma urealyticum [p=0.04] and 25+5 weeks for other microorganisms [p=0.0017] versus 28+6 weeks for mothers with negative amniotic fluid cultures) and lower birth weights (975 g [n.s.] and 828 g [p=0.0072] versus 1,041 g) but were appropriate for their gestational ages. 33.3% and 66.7% versus 24% of the children were mechanically ventilated [n.s.], duration of mechanical ventilation was 5.3 [p=0.02] and 10.1 days [p=0.04] versus 1.4 days, and prevalence of chronic lung disease was 38% and 33% versus 11% [n.s.]. Prevalence of severe intraventricular hemorrhage (12.5% [n.s.] and 33% [p=0.04] versus 3.4%) and nosocomial infections (50% for both groups of positive cultures versus 10.3% for negative cultures, p=0.02 and 0.03, respectively) was higher and median length of stay was significantly longer (121 [p=0.02] and 107 days [p=0.03] versus 60 days) in these patients. Maternal positive vaginal swab cultures were not associated with any of the above-mentioned factors. In none of the patients treated with macrolids for proven Ureaplasma urealyticum amnionitis could the microbes be eradicated.

CONCLUSION

Maternal positive amniotic fluid cultures have been associated with lower gestational age and lower birth weight. Rate of infant morbidity was higher and length of stay was significantly longer in this group. Positive vaginal swabs were not predictive for infant morbidity. Treatment of mothers showing positive amniotic fluid cultures with macrolids was not effective.

A comparative investigation of methods for logistic regression with separated or nearly separated data

In logistic regression analysis of small or sparse data sets, results obtained by classical maximum likelihood methods cannot be generally trusted. In such analyses it may even happen that the likelihood meets the convergence criteria while at least one parameter estimate diverges to +/-infinity. This situation has been termed 'separation', and it typically occurs whenever no events are observed in one of the two groups defined by a dichotomous covariate. More generally, separation is caused by a linear combination of continuous or dichotomous covariates that perfectly separates events from non-events. Separation implies infinite or zero maximum likelihood estimates of odds ratios, which are usually considered unrealistic. I provide some examples of separation and near-separation in clinical data sets and discuss some options to analyse such data, including exact logistic regression analysis and a penalized likelihood approach. Both methods supply finite point estimates in case of separation. Profile penalized likelihood confidence intervals for parameters show excellent behaviour in terms of coverage probability and provide higher power than exact confidence intervals. General advantages of the penalized likelihood approach are discussed.

Preterm histologic chorioamnionitis: impact on cord gas and pH values and neonatal outcome

OBJECTIVE

The purpose of this study was to further delineate the impact of preterm chorioamnionitis on a spectrum of neonatal outcomes using a large tertiary hospital population.

STUDY DESIGN

The perinatal/neonatal and placental pathology databases of St. Joseph's Health Care, London, Ontario, Canada, were used to obtain the umbilical cord gas and pH values, incidence of adverse neonatal outcomes, patient demographics, and placental pathology reports for all preterm (25 to 34 weeks of gestation), singleton, liveborn infants with no major anomalies who were delivered with spontaneous onset of labor or for suspected chorioamnionitis between November 1, 1995, and October 31, 2003. Patient groupings on the basis of placental inflammation and clinical chorioamnionitis were studied by a comparison of mean values and incidences for those neonatal outcomes that were available from the database with the use of linear and logistic regression analysis and controlling for potentially confounding variables.

RESULTS

There were 660 infants who met the inclusion criteria and had placental pathology available of whom 368 (56%) had no placental inflammation, 114 (17%) had placental chorioamnionitis, and 178 (27%) had placental funisitis. Umbilical cord partial pressure oxygen and base excess values were generally higher in the placental inflammation/clinical chorioamnionitis groups, in keeping with enhanced oxygen delivery and an overall decrease in the metabolic contribution to acidosis attributed to altered lactate metabolism in these infants. After adjusting for confounders (primarily differences in gestational age), the incidence of respiratory distress syndrome was significantly decreased in the placental inflammation/clinical chorioamnionitis groups, in keeping with cytokine-induced synthesis of surfactant proteins in these infants. Although the incidence of bronchopulmonary dysplasia, intraventricular hemorrhage, and periventricular leukomalacia was generally unchanged among the groups studied, that for intraventricular hemorrhage and periventricular leukomalacia was lowest in the placental inflammation/no clinical chorioamnionitis patients and highest in the placental inflammation/clinical chorioamnionitis patients, suggesting a differential effect of clinical chorioamnionitis for these outcomes.

CONCLUSION

Overall, infants born preterm with intrauterine infection were better oxygenated and showed less metabolic acidosis at birth and had incidences of respiratory distress syndrome and intraventricular hemorrhage, which were variably lower. Although there are likely threshold levels of inflammatory cytokines that do give rise to adverse outcome, a minimal level of cytokines may also be beneficial for the transition at birth from intrauterine to extrauterine existence when preterm pending the circumstances (ie, exposure to antenatal steroids) and emphasizing the complex relationship among preterm birth, infection, and adverse neonatal outcome.

Experimental intrauterine Ureaplasma infection in sheep

OBJECTIVE

Prenatal Ureaplasma spp exposure is associated with preterm birth and modulates the neonates' susceptibility to respiratory distress syndrome and bronchopulmonary dysplasia. We hypothesized that intra-amniotic ureaplasmas would cause lung inflammation and alter fetal lung development.

STUDY DESIGN

Pregnant ewes bearing singleton fetuses were given an intra-amniotic injection of 20 x 10 6 CFUs of U parvum (serovar 3) or vehicle, either 1, 3, 6, or 10 weeks before the delivery of preterm lambs at 124 days of gestation (n = 4-10 per group) for evaluation of inflammation and fetal lung maturation.

RESULTS

Ureaplasmas were recovered from amniotic and fetal lung fluids after intra-amniotic injection. Body weight and umbilical arterial pH were reduced by Ureaplasma exposure for 10 weeks ( P < .05). Ureaplasmas caused progressive lung inflammation and improvements in lung function that were associated with increased surfactant lipids (control, 0.13 +/- 0.02 micromol/kg; 10 weeks of Ureaplasma exposure, 7.43 +/- 3.0 micromol/kg; P < .001) and surfactant protein messenger RNA expression.

CONCLUSION

Long-term exposure to ureaplasmas in amniotic fluid alters ovine fetal development.

Amniotic cavity cultures, blood cultures, and surface swabs in preterm infants--useful tools for the management of early-onset sepsis?

AIMS

To evaluate the potential benefit of amniotic fluid and amniotic/placental membrane cultures for the management of early-onset sepsis in preterm infants.

METHODS

The results of amniotic cavity cultures obtained during cesarean section and of peripheral blood cultures and surface swabs obtained from the preterm infant at the time of admission were analyzed with respect to the diagnosis of clinical sepsis in 221 preterm infants <34 weeks of gestation.

RESULTS

136 (61.5%) patients had negative amniotic cavity culture results or growth of contaminants, 56 (25.3%) had growth of Ureaplasma urealyticum, and 29 (13.1%) of other pathogens. The corresponding numbers for surface swabs were 82.8%, 11.6%, and 5.6%. A positive blood culture was found in only two neonates. Fifty-four patients (24.4%) had clinical early-onset sepsis. Patients with amniotic cavity culture results that were positive for other pathogens were significantly more likely to experience clinical sepsis than patients with negative culture results (51.7% vs 15.1%, OR 6.1, p<0.0001). Regarding surface swabs, this correlation did not reach statistical significance.

CONCLUSION

The strong association between positive amniotic cavity culture results and clinical early-onset sepsis supports the existence of a causal relation and provides evidence for the potential value of amniotic and/or placental membrane sampling in the management of early-onset sepsis in preterm infants. Surface swabs add no additional information and hence should not be performed routinely.

Animal models of preterm birth

Preterm birth continues to pose a significant clinical dilemma and contributes to both acute and long-term neonatal morbidity. Despite efforts, the incidence of preterm birth has not decreased, partly because of our lack of understanding of the mechanisms that trigger parturition. Animal models are essential research tools for investigating the pathways that promote preterm parturition and for testing therapeutic interventions. Growing evidence correlates infection or inflammation with preterm birth. Consequently, many investigators have created animal models that reflect these findings. Current models of preterm parturition include diverse species, varying means of inducing an inflammatory or infectious state, and different routes of administration. Although each of these models can advance our knowledge, it is important to understand their advantages, disadvantages and unique characteristics. An understanding of such models will hopefully promote continued research that will ultimately lead to a decrease in preterm birth and an improvement in neonatal outcome.