Cohort study of congenital complete heart block among preterm neonates: a single-center experience over a 15-year period.

Congenital complete heart block (CCHB) is a very rare condition, with high risk of mortality. Prematurity is associated with immaturity of the cardiovascular system. Morbidity related to CCHB and prematurity has never been described. We describe a tertiary perinatal center experience over a 15-year period on CCHB management and complications in preterm infants. This is a single-center observational cohort study. All neonates admitted to neonatal intensive care unit with a diagnosis of isolated CCHB between January 2006 and January 2021 were identified. All preterm neonates (< 37 weeks) were compared with a control cohort of term neonates (≥ 37 weeks). Antenatal data, complications of prematurity, medical, and surgical management of CCHB were recorded. Twenty-four neonates with isolated CCHB (16 preterm and 8 term) were born during the study period, including 5 very preterm (< 32 weeks) and 11 preterm (32 to 37 weeks). All very preterm were born via emergency caesarian section without antenatal steroid administration. They had multiple severe morbidities including chronic lung disease, necrotizing enterocolitis, grades 3-4 intraventricular hemorrhage, cystic periventricular leukomalacia, and longer periods of mechanical and non-invasive ventilatory support than preterm. Thirteen out of sixteen preterm infants had permanent pacemakers inserted, compared to 1/8 for term newborns. All babies born before 35-week gestation were either paced or died.Conclusion: Premature neonates with CCHB have high risk of mortality and morbidity especially if undiagnosed and born by unnecessary emergency caesarian section without antenatal steroids. Prematurity below 35 weeks may be associated with death or pacemaker insertion. This supports better antenatal screening to avoid induced prematurity. What is Known: • Congenital complete heart block is a very rare condition associated with high morbidity and mortality. • Antenatal risk factors for poor outcome include fetal hydrops, low ventricular rate (HR <55 beats per minute), and congenital heart defect. What is New: • Infants born <32 weeks with CCHB had no antenatal steroid administration, and sustained high burden of morbidity (chronic lung disease, intraventricular hemorrhage, and cystic periventricular leukomalacia). • Birth <35 weeks is strongly associated with requiring pacing prior to discharge or death.

Desertibacillus haloalkaliphilus gen. nov., sp. nov., isolated from a saline desert.

Two Gram-stain-positive, rod-shaped and endospore-forming bacteria that represent a single species, designated strains KJ1-10-99T and KJ1-10-93, were isolated from a saline desert of Little Rann of Kutch, Gujarat, India. Analysis of 16S rRNA gene sequences revealed that the isolates belonged to the family Bacillaceae and were closely related to each other with 16S rRNA gene sequence similarity of 99.9 %. However, these two isolates formed a novel phylogenetic branch within this family. Both strains were aerobic, catalase and oxidase positive, and could grow optimally at 37 °C and pH 9. Further, strains KJ1-10-99T and KJ1-10-93 grew optimally at a NaCl concentration of 7.5 and 15 % (w/v), respectively. Both strains shared highest sequence similarity with Fermentibacillus polygoni IEB3T (96.90 %) followed by Bacillus nanhaiisediminis NH3T (96.3 %) and Bacillus alkalinitrilicus ANL-iso4T (96.3 %). The major cellular fatty acids were anteiso-C15 : 0, anteiso-C17:0, C16 : 0, and iso-C15 : 0. The major polar lipids were diphosphatidylglycerol and phosphatidylglycerol in both strains. The predominant isoprenoid quinone was MK-7 in both the strains. The peptidoglycan contained meso-diaminopimelic acid (meso-DAP) as the diagnostic diamino acid. The DNA G+C content of strains KJ1-10-99T and KJ1-10-93 were 48.7 and 48.9 mol% respectively. Both strains could be distinguished from closest phylogenetic neighbours based on a number of phenotypic properties. On the basis of polyphasic taxonomic analysis and phylogenetic data, we conclude that the strains KJ1-10-99T (=LMG 29918T=KCTC 33878T) and KJ1-10-93 (=LMG 29919=KCTC 33877) represent a novel species of a new genus in the family Bacillaceae, order Bacillales, for which the name Desertibacillus haloalkaliphilus gen. nov., sp. nov. is proposed.