Evaluation of two real time PCR assays for the detection of bacterial DNA in amniotic fluid

Changing Laboratory Practice for Early Detection of a Fetal Inflammatory Response: A Contemporary Approach

Neonates born with the fetal inflammatory response (FIR) are at risk of complications such as early-onset neonatal sepsis, meningitis, and pneumonia. Providing an early histopathological diagnosis of FIR is important to guide management but can be a challenge in busy laboratories. This is a retrospective cross-sectional study over a four-month duration recruiting all placental cases with histological chorioamnionitis in our institution. The diagnostic performance of the umbilical cord (UC) section in identifying FIR, relative to the corresponding subsequent placental sections, was assessed. Clinical predictors of umbilical cord FIR were also investigated. A total of 390 UC sections were analyzed, of which 206 (52.8%) were found positive for FIR: 111 cases (53.9%) stage 1, 87 (42.2%) stage 2, and 8 (3.9%) stage 3. Our data revealed a good diagnostic sensitivity, specificity, positive predictive value, and accuracy of 76.2% (95%CI: 68.6-82.7%), 82.4% (95%CI: 65.5-93.2%), 95.0% (95%CI: 90.2-97.6%), and 77.3% (95%CI: 70.6-83.1%) respectively, in cases when clinical chorioamnionitis, fever and/or prolonged rupture of membrane (PROM) were suspected, with the area under the curve of 0.793. A maternal inflammatory response (MIR) was correlated with FIR (p < 0.001). Multivariate logistic regression analysis indicated that the higher the gestational age, clinical suspicion of chorioamnionitis, fever, and/or PROM, and the higher the stage of MIR significantly increased the odds of FIR (p < 0.001). UC section diagnosis of FIR is reasonably accurate in cases with clinical chorioamnionitis, fever, and/or PROM. Changing current laboratory practice to rapid processing of UC ahead of the rest of the other placental sections can be recommended in busy pathology departments.

Optimization and validation of two multiplex qPCR assays for the rapid detection of microorganisms commonly invading the amniotic cavity

Microbial invasion of the amniotic cavity (MIAC) leading to infection is strongly associated with adverse pregnancy and neonatal outcomes. Limitations of current diagnostic assays to detect MIAC rapidly and accurately have hindered the ability of obstetricians to identify and treat intra-amniotic infections. We developed, optimized, and validated two multiplex quantitative polymerase chain reaction (qPCR) assays for the simultaneous detection and quantification of microbial taxa commonly associated with MIAC. The first assay allows for the quantification of general bacterial and fungal loads in amniotic fluid and includes a human reference gene to allow for assessing the integrity of clinical samples and the DNA extraction process. The second assay allows for the detection and quantification of four specific bacterial taxa commonly associated with MIAC: Ureaplasma spp., Mycoplasma hominis, Streptococcus agalactiae, and Fusobacterium nucleatum. The qPCR assays were validated by using both microbial isolates and clinical amniotic fluid samples. The assays were further validated by comparing qPCR amplification results to those from the microbial culture and bacterial 16S rRNA gene sequencing of amniotic fluid. Both assays demonstrated high reproducibility and are sensitive and specific to their intended targets. Therefore, these assays represent promising molecular diagnostic tools for the detection of MIAC. Most importantly, these assays may allow for administration of timely and targeted antibiotic interventions to reduce adverse perinatal outcomes attributed to intra-amniotic infections.

Validation of the loop-mediated isothermal amplification method for rapid and sensitive detection of Ureaplasma species in respiratory tracts of preterm infants

Introduction

A simple and rapid diagnosis of Ureaplasma spp. is required for the choice of the appropriate antibiotic. However, an ideal detection method has not been available. This study examines the efficacy of the loop-mediated isothermal amplification (LAMP) assay, which provides rapid and sensitive results, to detect Ureaplasma spp. in respiratory tract samples of preterm infants.

Methods

The study included preterm infants born before 32 weeks of gestation admitted Kagoshima City Hospital from June 2018 to March 2020. Nasopharyngeal swabs and/or tracheal aspirates were obtained in the first seven postnatal days. One hundred sixty-seven nasopharyngeal swabs and 101 tracheal aspirates were analyzed by LAMP, culture, and quantitative real-time polymerase chain reaction.

Results

All 167 infants had a median (range) gestational age of 28.7 weeks (22.3–30.9) and birthweight 1030g (322–1828). One hundred sixty-seven nasopharyngeal swabs and 101 tracheal aspirates were obtained. In the results of nasopharyngeal swabs, the sensitivity and specificity of LAMP were 73.9% (17/23) and 97.2% (140/144), whereas those of quantitative real-time polymerase chain reaction were 73.9% (17/23) and 95.8% (138/144), compared to culture. In the results of tracheal aspirates, the sensitivity and specificity of LAMP were 89.5% (17/19) and 92.7% (76/82), whereas those of quantitative real-time polymerase chain reaction were 89.5% (17/19) and 93.9% (77/82), compared to culture.

Conclusions

The LAMP assay showed similar sensitivity and specificity with quantitative real-time polymerase chain reaction in the respiratory tracts of preterm infants including extremely preterm infants during the immediate postnatal period. Therefore, the LAMP is a practical alternative for the early detection so that appropriate antibiotics can be administered for preventing BPD.

The value of amniotic fluid analysis in patients with suspected clinical chorioamnionitis

Objective To assess the value of incorporating amniotic fluid (AF) analysis in the management of patients with clinical chorioamnionitis. Methods This was a retrospective cohort study of all women carrying a singleton fetus and managed at our center between 2000 and 2009. We included only those women suspected of chorioamnionitis based on one or more of the following: (1) uterine tenderness, (2) maternal fever, (3) maternal and/or fetal tachycardia and (4) purulent discharge. The management was deemed to be justified if (1) pregnancy was terminated <24 weeks and histology confirmed chorioamnionitis; (2) delivery was performed expeditiously after initial assessment and histology confirmed chorioamnionitis; (3) delivery was delayed for 2-7 days and the patient completed a course of antenatal steroids before 34 weeks; and (4) delivery was delayed ≥7 days and histology was not indicative of chorioamnionitis, or delivery occurred after 37 weeks. Univariate and logistic regression analyses were used as appropriate. Results Of the 77 women with suspected chorioamnionitis, AF analysis was performed in 43 (55.8%) cases, and the management was justified in 63 (81.8%) cases based on the aforementioned criteria. Stepwise regression analysis confirmed AF analysis as a predictor of justified management. The rates of composite morbidity, neonatal sepsis, neonatal death and admissions to neonatal intensive care unit were lower in the justified management group. Conclusion Incorporation of AF analysis into clinical assessment does improve the management of suspected chorioamnionitis.

Comparison of two identification and susceptibility test kits for Ureaplasma spp and Mycoplasma hominis in amniotic fluid of patients at high risk for intra-amniotic infection

Objective: Ureaplasma urealyticum and Mycoplasma hominis are the most common microorganisms found in the amniotic fluid of patients at risk for preterm delivery. However, culture techniques for genital mycoplasms require special conditions, are barely considered as part of the evaluation of suspected intra-amniotic infection (IAI) and the results are available within 2 and 7 days. The objectives of this study are to validate the use of two commercially available kits (Mycoplasma IES y MYCOFAST^® RevolutioN) for the identification of Ureaplasma spp. and Mycoplasma hominis in amniotic fluid, to compare the results of these kits with those obtained by culture and real-time polymerase chain reaction (qPCR) and to report the antibiotic sensitivity profile of the genital mycoplasms identified.Methods: This is a prospective cohort study including women with singleton and twin gestations between 16 and 36 weeks. Patients were admitted to perform an amniocentesis due to pregnancy complications considered at high risk for IAI (e.g. preterm labor with intact membranes, preterm prelabour rupture of membranes, short cervix, etc.), treatment of polyhydramnios, and for the assessment of fetal death and fever without a focus.Results: Overall, 93 patients underwent amniocentesis and 63 had results available for all tests. The prevalence of a positive culture was 6% (4/63). There were four cases of Ureaplasma spp. and none of Mycoplasma hominis. The qPCR identified one case as Ureaplasma spp., one case as Ureaplasma parvum and two cases as Ureaplasma urealyticum. For all tests, the diagnostic performance was as follows: sensitivity 100% [95% CI (39.8-100%)], specificity 100% [95% CI (93.9-100%)], positive predictive value 100% [95% CI (39.8-100%)] and negative predictive value 100% [95% CI (93.9-100%)]. In this cohort, Ureaplasma spp. showed low resistance to erythromycin, but a high resistance to clindamycin and clarithromycin that may change according to the antibiotic concentration.Conclusions: To our knowledge, this is the first study that validates the use of the Mycoplasma IES and MYCOFAST^® RevolutioN kits for the identification of genital mycoplasmas in amniotic fluid. The results of these kits are mostly available within 24 hours, have an excellent correlation with those from broth cultures and qPCR and characterize the antibiotic sensitivity profile of the genital mycoplasms identified, providing an opportunity for specific treatment in cases of IAI. Further validation studies in other populations are needed.