Proteus mirabilis is known to be highly resistant to the action of polymyxin B (PB). However, the mechanism underlying PB resistance is not clear. In this study, we used Tn5 transposon mutagenesis to identify genes that may affect PB resistance in P. mirabilis. Two genes, ugd and galU, which may encode UDP-glucose dehydrogenase (Ugd) and UDP-glucose pyrophosphorylase (GalU), respectively, were identified. Knockout mutants of ugd and galU were found to be extremely sensitive to PB, presumably because of alterations in lipopolysaccharide (LPS) structure and cell surface architecture in these mutants. These mutants were defective in swarming, expressed lower levels of virulence factor hemolysin, and had lower cell invasion ability. Complementation of the ugd or galU mutant with the full-length ugd or galU gene, respectively, led to the restoration of wild-type phenotypic traits. Interestingly, we found that the expression of Ugd and GalU was induced by PB through RppA, a putative response regulator of the bacterial two-component system that we identified previously. Mutation in either ugd or galU led to activation of RpoE, an extracytoplasmic function sigma factor that has been shown to be activated by protein misfolding and alterations in cell surface structure in other bacteria. Activation of RpoE or RpoE overexpression was found to cause inhibition of FlhDC and hemolysin expression. To our knowledge, this is the first report describing the roles and regulation of Ugd and GalU in P. mirabilis.

Background: Feticide was suggested to avoid delivering children with abnormalities. Recently, twin pregnancies have increased. Selective feticide was proposed to achieve a good outcome of pregnancy. This study aimed to evaluate the performance of feticide in twin pregnancy with fetal anomaly. Methods: This was a retrospective study enrolled from 2009 to 2018. A total of 68 pregnancies with fetal anomalies received feticide. Potassium chloride was injected into the left ventricle to induce fetal asystole. Maternal and fetal characteristics of 16 dichorionic twins were documented to compare before and after 24th gestational week. Results: All pregnant women received feticide without any maternal or fetal complication. The reasons for choosing feticide were divided into four groups, including morphologic defect (61.8%), genetic-chromosomal abnormality (30.9%), obstetrical complication (5.9%), and maternal request (1.5%). Mean gestational age at delivery was significantly higher in dichorionic twins who underwent selective feticide before than after 24th gestational week (36.7 vs 33.4, p = 0.04). Conclusion: Intracardiac injection of potassium chloride was effective for feticide and safe for mothers and fetuses. Selective feticide served as an alternative approach for twin pregnancy with fetal anomaly after sufficient discussion.

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<b><i>Objective:</i></b> DiGeorge syndrome (DGS) is associated with microdeletions of chromosome 22q11. It is the second most common cause of congenital heart disease and is an important consideration whenever a conotruncal cardiac anomaly is identified. The availability of noninvasive prenatal testing (NIPT) is altering the practice of prenatal genetics and maternal-fetal medicine, resulting in a decline in invasive testing. Antenatal ultrasound and other biomarkers have their own limitation. NIPT was proposed to screen DGS with cell-free DNA in Taiwan. Here, we present our experience of prenatal diagnosis of DGS in our center. <b><i>Methods:</i></b> This was a retrospective study between November 1, 2019, and August 31, 2020, in Taiwan. Data were collected from 7,826 pregnant women self-referred for DGS screening with massive parallel shotgun sequencing-based NIPT. High-risk cases subsequently received amniocentesis for array comparative genomic hybridization (aCGH) to confirm the diagnosis. Characteristics of pregnancies were documented when participants received the test. Report of NIPT was completed 2 weeks after the test. Follow-up on high-risk cases was completed by telephone interview on January 30, 2021. <b><i>Results:</i></b> Thirteen cases showed high risk by NIPT, and 7 cases were confirmed by aCGH. The sensitivity and specificity were 100% (95% confidence interval [CI] 64.57–100.00%) and 99.92% (95% CI 99.83–99.96%). The prevalence of DGS was 1 in 1,118 pregnancies. The positive predictive rate was 53.85% (95% CI 29.14–76.79%). One true positive (TP) showed US anomaly, and 5 TPs selected termination. <b><i>Discussion/Conclusion:</i></b> NIPT demonstrated good performance in DGS screening. Detection of 22q11.2 deletion could be combined with routine screening to facilitate proper intervention.

Background With advanced diagnostic techniques, early identification of fetal anomaly becomes more accurate. However, certain diseases could only be diagnosed in late gestation. Feticide was suggested to avoid delivering children with abnormalities. Recently, twin pregnancies have increased gradually, and so have their complications. Selective feticide was considered to achieve good outcome of pregnancy. This study aimed to evaluate the performance of feticide in twin pregnancy with fetal anomaly. Methods This was a retrospective study enrolled from 2009 to 2018. A total of 68 pregnancies complicated with fetal anomalies received feticide were recorded. Potassium Chloride (KCl) was injected into left ventricle to induce fetal asystole. Monochorionic twin pregnancies were excluded, maternal and fetal characteristics of 16 dichorionic twins were documented to compare the effectiveness of feticide performed before and after 24th gestational week. Results All the pregnant women received feticide smoothly without any maternal complication. The reasons for choosing feticide were divided into four groups, including morphologic defect (61.8%), genetic-chromosomal abnormality (30.9%), obstetrical complication (5.9%) and maternal request (1.5%). Mean gestational age at delivery was significantly higher in dichorionic twins underwent selective feticide before and after 24th gestational week (36.7 vs 33.4, [p < .05]). No fetal loss in twin pregnancy demonstrated a high successful rate of selective feticide. Conclusion Intra-cardiac injection of KCl was effective for feticide and safe for mothers and fetuses. Selective feticide was beneficial to late gestation of dichorionic twin pregnancy. With sufficient discussion with patients, selective feticide served as an alternative approach for twin pregnancy with fetal anomaly.