Prevalence and determinants of antibiotic exposure in infants: A population-derived Australian birth cohort study.

AIM: The aim of this study was to describe antibiotic exposure in Australian infants during the first year of life, focusing on antibiotic class, indication, risk factors associated with exposure and comparison with international counterparts. METHODS: The Barwon Infant Study is a birth cohort study (n = 1074) with an unselected antenatal sampling frame from a large regional centre in Victoria, Australia. Longitudinal data on infection and medication were collected at 1, 3, 6, 9 and 12 months by parental questionnaire and from general practitioner and hospital records. Predictors of questionnaire non-completion were identified. A total of 660 infants with complete serial data were comprehensively examined. Antibiotic exposure was calculated as (i) antibiotic prescriptions and (ii) antibiotic days-exposed per person-year. RESULTS: Mean antibiotic prescription rate was 0.92 prescriptions (95% confidence interval (CI), 0.83-1.02) per person-year, with the highest rates in those aged <1 month (1.50 (95% CI, 1.09-1.91) per person-year). A total of 50.0% of infants were exposed to at least one antibiotic in their first year of life. Increasing number of siblings was associated with increased antibiotic exposure. Penicillin with extended spectrum (365 of 661 antibiotic prescriptions, 52.6%) and cephalosporins (12.0%) were the most frequently prescribed antibiotics. One fifth of antibiotics were prescribed for respiratory tract infections and bronchiolitis. CONCLUSION: Australian infants in this large population-based study are exposed to considerably more antibiotics than the majority of their international counterparts. Interventions aimed at addressing avoidable prescribing by medical practitioners and modifiable risk factors associated with antibiotic exposure may reduce antibiotic use.

Engraftment of nonintegrating neural stem cells differentially perturbs cortical activity in a dose-dependent manner.

Neural stem cell (NSC) therapy represents a potentially powerful approach for gene transfer in the diseased central nervous system. However, transplanted primary, embryonic stem cell- and induced pluripotent stem cell-derived NSCs generate largely undifferentiated progeny. Understanding how physiologically immature cells influence host activity is critical to evaluating the therapeutic utility of NSCs. Earlier inquiries were limited to single-cell recordings and did not address the emergent properties of neuronal ensembles. To interrogate cortical networks post-transplant, we used voltage sensitive dye imaging in mouse neocortical brain slices, which permits high temporal resolution analysis of neural activity. Although moderate NSC engraftment largely preserved host physiology, subtle defects in the activation properties of synaptic inputs were induced. High-density engraftment severely dampened cortical excitability, markedly reducing the amplitude, spatial extent, and velocity of propagating synaptic potentials in layers 2-6. These global effects may be mediated by specific disruptions in excitatory network structure in deep layers. We propose that depletion of endogenous cells in engrafted neocortex contributes to circuit alterations. Our data provide the first evidence that nonintegrating cells cause differential host impairment as a function of engrafted load. Moreover, they emphasize the necessity for efficient differentiation methods and proper controls for engraftment effects that interfere with the benefits of NSC therapy.

Ex vivo gene therapy using patient iPSC-derived NSCs reverses pathology in the brain of a homologous mouse model.

Neural stem cell (NSC) transplantation is a promising strategy for delivering therapeutic proteins in the brain. We evaluated a complete process of ex vivo gene therapy using human induced pluripotent stem cell (iPSC)-derived NSC transplants in a well-characterized mouse model of a human lysosomal storage disease, Sly disease. Human Sly disease fibroblasts were reprogrammed into iPSCs, differentiated into a stable and expandable population of NSCs, genetically corrected with a transposon vector, and assessed for engraftment in NOD/SCID mice. Following neonatal intraventricular transplantation, the NSCs engraft along the rostrocaudal axis of the CNS primarily within white matter tracts and survive for at least 4 months. Genetically corrected iPSC-NSCs transplanted post-symptomatically into the striatum of adult Sly disease mice reversed neuropathology in a zone surrounding the grafts, while control mock-corrected grafts did not. The results demonstrate the potential for ex vivo gene therapy in the brain using human NSCs from autologous, non-neural tissues.