Partial tetrasomy 18 mosaicism: Pre and postnatal diagnosis of a unique pattern.

OBJECTIVE: To present prenatal diagnosis and cytogenetic characterization of a unique pattern of partial tetrasomy 18 mosaicism. CASE REPORT: A 34-year-old woman underwent amniocentesis at 25 weeks of gestation due to anomalies detected in obstetric ultrasound. It revealed a de novo supernumerary partial isochromosome 18 in 11 of 37 metaphases of cultured amniocytes. The karyotype was 47,XX,+idic(18) (q12.3)[11]/46,XX[26]. Elective cesarean section was performed at 33 weeks of gestational age due to anhydramnios. A female symmetric small for gestational age baby with dysmorphic features and an Apgar score of 9/10/10 was born. She had a good clinical outcome during hospitalization. Postnatal peripheral blood karyotype was normal. Interphase fluorescence in situ hybridization in a sample of the oral mucosa confirmed the prenatal diagnosis. At three months of corrected age she had a normal psychomotor development. CONCLUSION: To the best of our knowledge, this is the first reported case of mosaic partial tetrasomy 18 including segments of the long arm. This newborn's relatively mild phenotype highlights the challenges of prenatal genetic counselling in mosaic cases with fetal anomalies.

CC17 group B Streptococcus exploits integrins for neonatal meningitis development.

Group B Streptococcus (GBS) is the major cause of human neonatal infections. A single clone, designated CC17-GBS, accounts for more than 80% of meningitis cases, the most severe form of the infection. However, the events allowing blood-borne GBS to penetrate the brain remain largely elusive. In this study, we identified the host transmembrane receptors α5ß1 and αvß3 integrins as the ligands of Srr2, a major CC17-GBS-specific adhesin. Two motifs located in the binding region of Srr2 were responsible for the interaction between CC17-GBS and these integrins. We demonstrated in a blood-brain-barrier cellular model that both integrins contributed to the adhesion and internalization of CC17-GBS. Strikingly, both integrins were overexpressed during the postnatal period in the brain vessels of the blood-brain barrier and blood-cerebrospinal fluid barrier and contributed to juvenile susceptibility to CC17 meningitis. Finally, blocking these integrins decreased the ability of CC17-GBS to cross into the CNS of juvenile mice in an in vivo model of meningitis. Our study demonstrated that CC17-GBS exploits integrins in order to cross the brain vessels, leading to meningitis. Importantly, it provides host molecular insights into neonate's susceptibility to CC17-GBS meningitis, thereby opening new perspectives for therapeutic and prevention strategies of GBS-elicited meningitis.