β-Lactam Resistance Response Triggered by Inactivation of a Nonessential Penicillin-Binding Protein

It has long been recognized that the modification of penicillin-binding proteins (PBPs) to reduce their affinity for β-lactams is an important mechanism (target modification) by which Gram-positive cocci acquire antibiotic resistance. Among Gram-negative rods (GNR), however, this mechanism has been considered unusual, and restricted to clinically irrelevant laboratory mutants for most species. Using as a model Pseudomonas aeruginosa, high up on the list of pathogens causing life-threatening infections in hospitalized patients worldwide, we show that PBPs may also play a major role in β-lactam resistance in GNR, but through a totally distinct mechanism. Through a detailed genetic investigation, including whole-genome analysis approaches, we demonstrate that high-level (clinical) β-lactam resistance in vitro, in vivo, and in the clinical setting is driven by the inactivation of the dacB-encoded nonessential PBP4, which behaves as a trap target for β-lactams. The inactivation of this PBP is shown to determine a highly efficient and complex β-lactam resistance response, triggering overproduction of the chromosomal β-lactamase AmpC and the specific activation of the CreBC (BlrAB) two-component regulator, which in turn plays a major role in resistance. These findings are a major step forward in our understanding of β-lactam resistance biology, and, more importantly, they open up new perspectives on potential antibiotic targets for the treatment of infectious diseases

Arp2/3- and Cofilin-coordinated Actin Dynamics Is Required for Insulin-mediated GLUT4 Translocation to the Surface of Muscle Cells

Insulin increases GLUT4 at the muscle cell surface, and this process requires actin remodeling. We show that a dynamic cycle of actin polymerization and severing is induced by insulin, governed by Arp2/3 and dephosphorylation of cofilin, respectively. The cycle is self-perpetuating and is essential for GLUT4 translocation

Modelling Survival and Mortality Risk to 15 Years of Age for a National Cohort of Children with Serious Congenital Heart Defects Diagnosed in Infancy

Congenital heart defects (CHDs) are a significant cause of death in infancy. Although contemporary management ensures that 80% of affected children reach adulthood, post-infant mortality and factors associated with death during childhood are not well-characterised. Using data from a UK-wide multicentre birth cohort of children with serious CHDs, we observed survival and investigated independent predictors of mortality up to age 15 years. Methods Data were extracted retrospectively from hospital records and death certificates of 3,897 children (57% boys) in a prospectively identified cohort, born 1992–1995 with CHDs requiring intervention or resulting in death before age one year. A discrete-time survival model accounted for time-varying predictors; hazards ratios were estimated for mortality. Incomplete data were addressed through multilevel multiple imputation. Findings By age 15 years, 932 children had died; 144 died without any procedure. Survival to one year was 79.8% (95% confidence intervals [CI] 78.5, 81.1%) and to 15 years was 71.7% (63.9, 73.4%), with variation by cardiac diagnosis. Importantly, 20% of cohort deaths occurred after age one year. Models using imputed data (including all children from birth) demonstrated higher mortality risk as independently associated with cardiac diagnosis, female sex, preterm birth, having additional cardiac defects or non-cardiac malformations. In models excluding children who had no procedure, additional predictors of higher mortality were younger age at first procedure, lower weight or height, longer cardiopulmonary bypass or circulatory arrest duration, and peri-procedural complications; non-cardiac malformations were no longer significant. Interpretation We confirm the high mortality risk associated with CHDs in the first year of life and demonstrate an important persisting risk of death throughout childhood. Late mortality may be underestimated by procedure-based audit focusing on shorter-term surgical outcomes. National monitoring systems should emphasise the importance of routinely capturing longer-term survival and exploring the mechanismsThis work was supported by a British Heart Foundation project grant (reference PG/02/065/13934). RLK was awarded an MRC Special Training Fellowship in Health of the Public and Health Services Research (reference G106/1083). HG and the Centre for Paediatric Epidemiology and Biostatistics benefited from Medical Research Council funding support to the MRC Centre of Epidemiology for Child Health (reference G04005546). Great Ormond St Hospital for Children NHS Trust and the UCL Institute of Child Health receives a proportion of funding from the Department of Health's NIHR Biomedical Research Centres schem

Smoking during pregnancy: a significant cause of neonatal thyroid enlargement.

The influence of maternal smoking during pregnancy on the function and the echographic volume of the neonatal thyroid gland was examined in an area of borderline iodine intake (median maternal urinary iodine: 315 range 79-1558 nmol/l). There was a positive correlation (P less than 0.001) between cord serum thiocyanate (SCN) concentrations used as an index of maternal smoking and the maternal smoking habits. The thyroid volume/birthweight ratio increased significantly as a function of SCN values (P less than 0.005): this increase was secondary to a decrease in birthweight as well as to an increase in thyroid volume. There was also a positive correlation between cord serum thyroglobulin (Tg) and SCN levels (P = 0.001). Serum thyroid-stimulating hormone (TSH) and free thyroxine (FT4) values remained within the normal range for age in all newborn infants and were not significantly correlated with SCN values. These results show that smoking during pregnancy in areas with borderline iodine intake may be a significant cause of thyroid enlargement in the newborn.Journal ArticleSCOPUS: ar.jinfo:eu-repo/semantics/publishe