Cortico-striatal beta oscillations as a reward-related signal.

The value associated with reward is sensitive to external factors, such as the time between the choice and reward delivery as classically manipulated in temporal discounting tasks. Subjective preference for two reward options is dependent on objective variables of reward magnitude and reward delay. Single neuron correlates of reward value have been observed in regions, including ventral striatum, orbital, and medial prefrontal cortex. Brain imaging studies show cortico-striatal-limbic network activity related to subjective preferences. To explore how oscillatory dynamics represent reward processing across brain regions, we measured local field potentials of rats performing a temporal discounting task. Our goal was to use a data-driven approach to identify an electrophysiological marker that correlates with reward preference. We found that reward-locked oscillations at beta frequencies signaled the magnitude of reward and decayed with longer temporal delays. Electrodes in orbitofrontal/medial prefrontal cortex, anterior insula, ventral striatum, and amygdala individually increased power and were functionally connected at beta frequencies during reward outcome. Beta power during reward outcome correlated with subjective value as defined by a computational model fit to the discounting behavior. These data suggest that cortico-striatal beta oscillations are a reward signal correlated, which may represent subjective value and hold potential to serve as a biomarker and potential therapeutic target.

Phase coherence-A time-localized approach to studying interactions.

Coherence measures the similarity of progression of phases between oscillations or waves. When applied to multi-scale, nonstationary dynamics with time-varying amplitudes and frequencies, high values of coherence provide a useful indication of interactions, which might otherwise go unnoticed. However, the choice of analyzing coherence based on phases and amplitudes (amplitude-weighted phase coherence) vs only phases (phase coherence) has long been seen as arbitrary. Here, we review the concept of coherence and focus on time-localized methods of analysis, considering both phase coherence and amplitude-weighted phase coherence. We discuss the importance of using time-localized analysis and illustrate the methods and their practicalities on both numerically modeled and real time-series. The results show that phase coherence is more robust than amplitude-weighted phase coherence to both noise perturbations and movement artifacts. The results also have wider implications for the analysis of real data and the interpretation of physical systems.

Incidence of chikungunya virus infections among Kenyan children with neurological disease, 2014-2018: A cohort study.

BACKGROUND: Neurological complications due to chikungunya virus (CHIKV) infection have been described in different parts of the world, with children being disproportionately affected. However, the burden of CHIKV-associated neurological disease in Africa is currently unknown and given the lack of diagnostic facilities in routine care it is possible that CHIKV is an unrecognized etiology among children with encephalitis or other neurological illness. METHODS AND FINDINGS: We estimated the incidence of CHIKV infection among children hospitalized with neurological disease in Kilifi County, coastal Kenya. We used reverse transcriptase polymerase chain reaction (RT-PCR) to systematically test for CHIKV in cerebrospinal fluid (CSF) samples from children aged <16 years hospitalized with symptoms of neurological disease at Kilifi County Hospital between January 2014 and December 2018. Clinical records were linked to the Kilifi Health and Demographic Surveillance System and population incidence rates of CHIKV infection estimated. There were 18,341 pediatric admissions for any reason during the 5-year study period, of which 4,332 (24%) had CSF collected. The most common clinical reasons for CSF collection were impaired consciousness, seizures, and coma (47%, 22%, and 21% of all collections, respectively). After acute investigations done for immediate clinical care, CSF samples were available for 3,980 admissions, of which 367 (9.2%) were CHIKV RT-PCR positive. Case fatality among CHIKV-positive children was 1.4% (95% CI 0.4, 3.2). The annual incidence of CHIKV-associated neurological disease varied between 13 to 58 episodes per 100,000 person-years among all children <16 years old. Among children aged <5 years, the incidence of CHIKV-associated neurological disease was 77 per 100,000 person-years, compared with 20 per 100,000 for cerebral malaria and 7 per 100,000 for bacterial meningitis during the study period. Because of incomplete case ascertainment due to children not presenting to hospital, or not having CSF collected, these are likely minimum estimates. Study limitations include reliance on hospital-based surveillance and limited CSF sampling in children in coma or other contraindications to lumbar puncture, both of which lead to under-ascertainment of incidence and of case fatality. CONCLUSIONS: In this study, we observed that CHIKV infections are relatively more common than cerebral malaria and bacterial meningitis among children hospitalized with neurological disease in coastal Kenya. Given the wide distribution of CHIKV mosquito vectors, studies to determine the geographic extent of CHIKV-associated neurological disease in Africa are essential.

Proteasome inhibition for treatment of leishmaniasis, Chagas disease and sleeping sickness.

Chagas disease, leishmaniasis and sleeping sickness affect 20 million people worldwide and lead to more than 50,000 deaths annually. The diseases are caused by infection with the kinetoplastid parasites Trypanosoma cruzi, Leishmania spp. and Trypanosoma brucei spp., respectively. These parasites have similar biology and genomic sequence, suggesting that all three diseases could be cured with drugs that modulate the activity of a conserved parasite target. However, no such molecular targets or broad spectrum drugs have been identified to date. Here we describe a selective inhibitor of the kinetoplastid proteasome (GNF6702) with unprecedented in vivo efficacy, which cleared parasites from mice in all three models of infection. GNF6702 inhibits the kinetoplastid proteasome through a non-competitive mechanism, does not inhibit the mammalian proteasome or growth of mammalian cells, and is well-tolerated in mice. Our data provide genetic and chemical validation of the parasite proteasome as a promising therapeutic target for treatment of kinetoplastid infections, and underscore the possibility of developing a single class of drugs for these neglected diseases.

Guide Swap enables genome-scale pooled CRISPR-Cas9 screening in human primary cells.

CRISPR-Cas9 screening allows genome-wide interrogation of gene function. Currently, to achieve the high and uniform Cas9 expression desirable for screening, one needs to engineer stable and clonal Cas9-expressing cells-an approach that is not applicable in human primary cells. Guide Swap permits genome-scale pooled CRISPR-Cas9 screening in human primary cells by exploiting the unexpected finding that editing by lentivirally delivered, targeted guide RNAs (gRNAs) occurs efficiently when Cas9 is introduced in complex with nontargeting gRNA. We validated Guide Swap in depletion and enrichment screens in CD4+ T cells. Next, we implemented Guide Swap in a model of ex vivo hematopoiesis, and identified known and previously unknown regulators of CD34+ hematopoietic stem and progenitor cell (HSPC) expansion. We anticipate that this platform will be broadly applicable to other challenging cell types, and thus will enable discovery in previously inaccessible but biologically relevant human primary cell systems.

Associations between oral health and general health: a surveywide association study of the NHANES.

OBJECTIVE: This proof of concept study uses data from the National Health and Nutrition Examination Survey (NHANES) to explore potential associations between oral and systemic health in a survey-wide association study (SWAS). BASIC RESEARCH DESIGN: Data from n=9,971 records in the 2015-2016 NHANES survey were used to evaluate associations between self-rated oral health and the various systemic health conditions that are included in the survey. Associations were estimated using survey-weighted linear regression models adjusted for age, sex, race, and smoking status. RESULTS: Substantial associations with self-rated oral health were evident after correction for multiple comparisons. The study revealed associations in categories of mental health, cardiovascular disease, and diabetes adding to the body of evidence. The study also suggested associations with physical functioning, vision, hearing, genitourinary symptoms, and the prevalence of hepatitis. CONCLUSIONS: The SWAS method demonstrated the ability to identify associations between oral health and systemic health. Suggested associations should be investigated further investigated with emphasis on both biologic and societal mechanisms. The noteworthy associations with mental health, physical activity, and cardiovascular disease in this study inform clinicians from each of these disciplines that they may benefit from collaborations with oral health care providers to promote whole-person health.

Mutations Reducing In Vitro Susceptibility to Novel LpxC Inhibitors in Pseudomonas aeruginosa and Interplay of Efflux and Nonefflux Mechanisms.

Upregulated expression of efflux pumps, lpxC target mutations, LpxC protein overexpression, and mutations in fabG were previously shown to mediate single-step resistance to the LpxC inhibitor CHIR-090 in P. aeruginosa Single-step selection experiments using three recently described LpxC inhibitors (compounds 2, 3, and 4) and mutant characterization showed that these mechanisms affect susceptibility to additional novel LpxC inhibitors. Serial passaging of P. aeruginosa wild-type and efflux pump-defective strains using the LpxC inhibitor CHIR-090 or compound 1 generated substantial shifts in susceptibility and underscored the interplay of efflux and nonefflux mechanisms. Whole-genome sequencing of CHIR-090 passage mutants identified efflux pump overexpression, fabG mutations, and novel mutations in fabF1 and in PA4465 as determinants of reduced susceptibility. Two new lpxC mutations, encoding A214V and G208S, that reduce susceptibility to certain LpxC inhibitors were identified in these studies, and we show that these and other target mutations differentially affect different LpxC inhibitor scaffolds. Lastly, the combination of target alteration (LpxCA214V) and upregulated expression of LpxC was shown to be tolerated in P. aeruginosa and could mediate significant decreases in susceptibility.

Defects in Efflux (oprM), ß-Lactamase (ampC), and Lipopolysaccharide Transport (lptE) Genes Mediate Antibiotic Hypersusceptibility of Pseudomonas aeruginosa Strain Z61.

Antibiotic hypersensitive bacterial mutants (e.g., Escherichia coliimp) are used to investigate intrinsic resistance and are exploited in antibacterial discovery to track weak antibacterial activity of novel inhibitor compounds. Pseudomonas aeruginosa Z61 is one such drug-hypersusceptible strain generated by chemical mutagenesis, although the genetic basis for hypersusceptibility is not fully understood. Genome sequencing of Z61 revealed nonsynonymous single-nucleotide polymorphisms in 153 genes relative to its parent strain, and three candidate mutations (in oprM, ampC, and lptE) predicted to mediate hypersusceptibility were characterized. The contribution of these mutations was confirmed by genomic restoration of the wild-type sequences, individually or in combination, in the Z61 background. Introduction of the lptE mutation or genetic inactivation of oprM and ampC genes alone or together in the parent strain recapitulated drug sensitivities. This showed that disruption of oprM (which encodes a major outer membrane efflux pump channel) increased susceptibility to pump substrate antibiotics, that inactivation of the inducible ß-lactamase gene ampC contributed to ß-lactam susceptibility, and that mutation of the lipopolysaccharide transporter gene lptE strongly altered the outer membrane permeability barrier, causing susceptibility to large antibiotics such as rifampin and also to ß-lactams.

Target (MexB)- and Efflux-Based Mechanisms Decreasing the Effectiveness of the Efflux Pump Inhibitor D13-9001 in Pseudomonas aeruginosa PAO1: Uncovering a New Role for MexMN-OprM in Efflux of ß-Lactams and a Novel Regulatory Circuit (MmnRS) Controlling MexMN Expression.

Efflux pumps contribute to antibiotic resistance in Gram-negative pathogens. Correspondingly, efflux pump inhibitors (EPIs) may reverse this resistance. D13-9001 specifically inhibits MexAB-OprM in Pseudomonas aeruginosa Mutants with decreased susceptibility to MexAB-OprM inhibition by D13-9001 were identified, and these fell into two categories: those with alterations in the target MexB (F628L and ΔV177) and those with an alteration in a putative sensor kinase of unknown function, PA1438 (L172P). The alterations in MexB were consistent with reported structural studies of the D13-9001 interaction with MexB. The PA1438L172P alteration mediated a >150-fold upregulation of MexMN pump gene expression and a >50-fold upregulation of PA1438 and the neighboring response regulator gene, PA1437. We propose that these be renamed mmnR and mmnS for MexMN regulator and MexMN sensor, respectively. MexMN was shown to partner with the outer membrane channel protein OprM and to pump several ß-lactams, monobactams, and tazobactam. Upregulated MexMN functionally replaced MexAB-OprM to efflux these compounds but was insusceptible to inhibition by D13-9001. MmnSL172P also mediated a decrease in susceptibility to imipenem and biapenem that was independent of MexMN-OprM. Expression of oprD, encoding the uptake channel for these compounds, was downregulated, suggesting that this channel is also part of the MmnSR regulon. Transcriptome sequencing (RNA-seq) of cells encoding MmnSL172P revealed, among other things, an interrelationship between the regulation of mexMN and genes involved in heavy metal resistance.

Polymorphism in a lincRNA Associates with a Doubled Risk of Pneumococcal Bacteremia in Kenyan Children.

Bacteremia (bacterial bloodstream infection) is a major cause of illness and death in sub-Saharan Africa but little is known about the role of human genetics in susceptibility. We conducted a genome-wide association study of bacteremia susceptibility in more than 5,000 Kenyan children as part of the Wellcome Trust Case Control Consortium 2 (WTCCC2). Both the blood-culture-proven bacteremia case subjects and healthy infants as controls were recruited from Kilifi, on the east coast of Kenya. Streptococcus pneumoniae is the most common cause of bacteremia in Kilifi and was thus the focus of this study. We identified an association between polymorphisms in a long intergenic non-coding RNA (lincRNA) gene (AC011288.2) and pneumococcal bacteremia and replicated the results in the same population (p combined = 1.69 × 10(-9); OR = 2.47, 95% CI = 1.84-3.31). The susceptibility allele is African specific, derived rather than ancestral, and occurs at low frequency (2.7% in control subjects and 6.4% in case subjects). Our further studies showed AC011288.2 expression only in neutrophils, a cell type that is known to play a major role in pneumococcal clearance. Identification of this novel association will further focus research on the role of lincRNAs in human infectious disease.

Multicentre evaluation of Erytra Eflexis®, a benchtop fully automated analyser with a compact design for routine use in blood transfusion laboratory.

OBJECTIVES: Evaluation of the compact benchtop Erytra Eflexis® automated analyser was performed at three health centres representing a range of routine transfusion workload. BACKGROUND: Automation instruments with the simplicity and flexibility adequate for small- to mid-sized blood transfusion services are an unmet need. METHODS: Performance in pre-transfusion testing (2109 ABO/D, 382 Rh/K phenotype, 2001 antibody screening, 113 antibody identification, 151 DAT, 88 extended phenotype; 655 cross matching) in comparison to Erytra® as reference device was assessed. Throughput [time to first result (TTFR), final turn-around time (TAT), processing rate] was calculated; usability and adaptability in laboratory practice under routine and with emergency samples were surveyed. RESULTS: Agreement between systems was 99·8% (11/5499 test discrepancies, all due to weak/doubtful positive reactions). Erytra Eflexis produced six true positives (two Rh/D, two B positives, two screening), four false positives (three screening and one cross matching) and one false negative (screening). Processing of eight routine samples with the Erytra Eflexis for ABO/Rh(D) and screening took 34-38 min and 32-37 min, respectively, independent of the simultaneous processing of a STAT sample, whether or not the incubator for STAT was reserved. In this scenario, a STAT sample requested within 2 min after the routine load was processed in 14-26 min. Processing rate tended to stabilise and optimise in the larger workloads, particularly in ABO/Rh(D)/K cards (16·7, 18 and 19·5 results/h for 10, 15 and 24 specimens, respectively). CONCLUSION: Erytra Eflexis analyser was found to be reliable and suitable for pre-transfusion routine tests performed in a small-/medium-sized blood transfusion laboratory.

Pathogenicity of the bacterium New Zealand rickettsia-like organism (NZ-RLO2) in Chinook salmon Oncorhynchus tshawytscha smolt.

Farmed New Zealand Chinook salmon Oncorhynchus tshawytscha Walbaum have been found to be infected by rickettsia-like organisms (NZ-RLO). While these Gram-negative intra-cellular bacteria are closely related to Piscirickettsia salmonis, a significant pathogen for farmed salmon globally, the pathogenicity of NZ-RLO is unknown. The aim of the present study was to determine if one strain, NZ-RLO2, causes disease in Chinook salmon. Post-smolt salmon were inoculated with NZ-RLO2 by intraperitoneal injection at high, medium and low doses and observed for 30 d. All fish in the high and medium dosed groups died by the end of the study and 63% of the low dose group died within 30 d of inoculation. Necropsy revealed the fish inoculated with NZ-RLO2 had internal multifocal haemorrhages. The most consistent histological finding in fish inoculated with NZ-RLO2 was neutrophilic and necrotizing pancreatitis and steatitis with intra-cytoplasmic organisms often visible within areas of inflammation. Other histological lesions included multifocal hepatic necrosis, haematopoietic cell necrosis and splenic and renal lymphoid depletion. The presence of NZ-RLO2 within the inoculated fish was confirmed by replication in cell culture and qPCR. The results suggest NZ-RLO2 can cause disease in Chinook salmon and therefore could be a significant pathogen in farmed Chinook salmon.

How many squat-stand manoeuvres to assess dynamic cerebral autoregulation?

PURPOSE: Squat-stand manoeuvres (SSMs) have been used to induce blood pressure (BP) changes for the reliable assessment of dynamic cerebral autoregulation. However, they are physically demanding and thus multiple manoeuvres can be challenging for older subjects. This study aimed to determine the minimum number of SSMs required to obtain satisfactory coherence, thus minimising the subjects' workload. METHOD: 20 subjects performed SSMs at a frequency of 0.05 Hz. End-tidal CO2, cerebral blood flow velocity, heart rate, continuous BP and the depth of the squat were measured. 11 subjects returned for a repeat visit. The time points at which subjects had performed 3, 6, 9, 12 and 15 SSMs were determined. Transfer function analysis was performed on files altered to the required length to obtain estimates of coherence and the autoregulation index (ARI). RESULTS: After three SSMs, coherence (0.05 Hz) was 0.93 ± 0.05, and peaked at 0.95 ± 0.02 after 12 manoeuvres. ARI decreased consecutively with more manoeuvres. ARI was comparable across the two visits (p = 0.92), but coherence was significantly enhanced during the second visit (p < 0.01). The intra-subject coefficients of variation (CoV) for ARI remained comparable as the number of manoeuvres varied. CONCLUSIONS: This analysis can aid those designing SSM protocols, especially where participants are unable to tolerate a standard 5-min protocol or when a shorter protocol is needed to accommodate additional tests. We emphasise that fewer manoeuvres should only be used in exceptional circumstances, and where possible a full set of manoeuvres should be performed. Furthermore, these results need replicating at 0.10 Hz to ensure their applicability to different protocols.

Validity of an ultra-wideband local positioning system to measure locomotion in indoor sports.

The validity of an Ultra-wideband (UWB) positioning system was investigated during linear and change-of-direction (COD) running drills. Six recreationally-active men performed ten repetitions of four activities (walking, jogging, maximal acceleration, and 45º COD) on an indoor court. Activities were repeated twice, in the centre of the court and on the side. Participants wore a receiver tag (Clearsky T6, Catapult Sports) and two reflective markers placed on the tag to allow for comparisons with the criterion system (Vicon). Distance, mean and peak velocity, acceleration, and deceleration were assessed. Validity was assessed via percentage least-square means difference (Clearsky-Vicon) with 90% confidence interval and magnitude-based inference; typical error was expressed as within-subject standard deviation. The mean differences for distance, mean/peak speed, and mean/peak accelerations in the linear drills were in the range of 0.2-12%, with typical errors between 1.2 and 9.3%. Mean and peak deceleration had larger differences and errors between systems. In the COD drill, moderate-to-large differences were detected for the activity performed in the centre of the court, increasing to large/very large on the side. When filtered and smoothed following a similar process, the UWB-based positioning system had acceptable validity, compared to Vicon, to assess movements representative of indoor sports.

Utilizing Chemical Genomics to Identify Cytochrome b as a Novel Drug Target for Chagas Disease.

Unbiased phenotypic screens enable identification of small molecules that inhibit pathogen growth by unanticipated mechanisms. These small molecules can be used as starting points for drug discovery programs that target such mechanisms. A major challenge of the approach is the identification of the cellular targets. Here we report GNF7686, a small molecule inhibitor of Trypanosoma cruzi, the causative agent of Chagas disease, and identification of cytochrome b as its target. Following discovery of GNF7686 in a parasite growth inhibition high throughput screen, we were able to evolve a GNF7686-resistant culture of T. cruzi epimastigotes. Clones from this culture bore a mutation coding for a substitution of leucine by phenylalanine at amino acid position 197 in cytochrome b. Cytochrome b is a component of complex III (cytochrome bc1) in the mitochondrial electron transport chain and catalyzes the transfer of electrons from ubiquinol to cytochrome c by a mechanism that utilizes two distinct catalytic sites, QN and QP. The L197F mutation is located in the QN site and confers resistance to GNF7686 in both parasite cell growth and biochemical cytochrome b assays. Additionally, the mutant cytochrome b confers resistance to antimycin A, another QN site inhibitor, but not to strobilurin or myxothiazol, which target the QP site. GNF7686 represents a promising starting point for Chagas disease drug discovery as it potently inhibits growth of intracellular T. cruzi amastigotes with a half maximal effective concentration (EC50) of 0.15 µM, and is highly specific for T. cruzi cytochrome b. No effect on the mammalian respiratory chain or mammalian cell proliferation was observed with up to 25 µM of GNF7686. Our approach, which combines T. cruzi chemical genetics with biochemical target validation, can be broadly applied to the discovery of additional novel drug targets and drug leads for Chagas disease.

Fecal metabolomics in pediatric spondyloarthritis implicate decreased metabolic diversity and altered tryptophan metabolism as pathogenic factors.

We have previously shown alterations in the composition of the gut microbiota in children with enthesitis-related arthritis (ERA). To explore the mechanisms by which an altered microbiota might predispose to arthritis, we performed metabolomic profiling of fecal samples of children with ERA. Fecal samples were collected from two cohorts of children with ERA and healthy control subjects. Nano-liquid chromatography-mass spectroscopy (LC-MS) was performed on the fecal water homogenates with identification based upon mass: charge ratios. Sequencing of the 16S ribosomal DNA (rDNA) on the same stool specimens was performed. In both sets of subjects, patients demonstrated lower diversity of ions and under-representation of multiple metabolic pathways, including the tryptophan metabolism pathway. For example, in the first cohort, out of 1500 negatively charged ions, 154 were lower in ERA patients, compared with only one that was higher. Imputed functional annotation of the 16S ribosomal DNA sequence data demonstrated significantly fewer microbial genes associated with metabolic processes in the patients compared with the controls (77 million versus 58 million, P=0.050). Diminished metabolic diversity and alterations in the tryptophan metabolism pathway may be a feature of ERA.

Disruption of mGluR5 in parvalbumin-positive interneurons induces core features of neurodevelopmental disorders.

Alterations in glutamatergic transmission onto developing GABAergic systems, in particular onto parvalbumin-positive (Pv(+)) fast-spiking interneurons, have been proposed as underlying causes of several neurodevelopmental disorders, including schizophrenia and autism. Excitatory glutamatergic transmission, through ionotropic and metabotropic glutamate receptors, is necessary for the correct postnatal development of the Pv(+) GABAergic network. We generated mutant mice in which the metabotropic glutamate receptor 5 (mGluR5) was specifically ablated from Pv(+) interneurons postnatally, and investigated the consequences of such a manipulation at the cellular, network and systems levels. Deletion of mGluR5 from Pv(+) interneurons resulted in reduced numbers of Pv(+) neurons and decreased inhibitory currents, as well as alterations in event-related potentials and brain oscillatory activity. These cellular and sensory changes translated into domain-specific memory deficits and increased compulsive-like behaviors, abnormal sensorimotor gating and altered responsiveness to stimulant agents. Our findings suggest a fundamental role for mGluR5 in the development of Pv(+) neurons and show that alterations in this system can produce broad-spectrum alterations in brain network activity and behavior that are relevant to neurodevelopmental disorders.

Identification of a small molecule with activity against drug-resistant and persistent tuberculosis.

A cell-based phenotypic screen for inhibitors of biofilm formation in mycobacteria identified the small molecule TCA1, which has bactericidal activity against both drug-susceptible and -resistant Mycobacterium tuberculosis (Mtb) and sterilizes Mtb in vitro combined with rifampicin or isoniazid. In addition, TCA1 has bactericidal activity against nonreplicating Mtb in vitro and is efficacious in acute and chronic Mtb infection mouse models both alone and combined with rifampicin or isoniazid. Transcriptional analysis revealed that TCA1 down-regulates genes known to be involved in Mtb persistence. Genetic and affinity-based methods identified decaprenyl-phosphoryl-ß-D-ribofuranose oxidoreductase DprE1 and MoeW, enzymes involved in cell wall and molybdenum cofactor biosynthesis, respectively, as targets responsible for the activity of TCA1. These in vitro and in vivo results indicate that this compound functions by a unique mechanism and suggest that TCA1 may lead to the development of a class of antituberculosis agents.

Fitness costs of rifampicin resistance in Mycobacterium tuberculosis are amplified under conditions of nutrient starvation and compensated by mutation in the ß' subunit of RNA polymerase.

Rifampicin resistance, a defining attribute of multidrug-resistant tuberculosis, is conferred by mutations in the ß subunit of RNA polymerase. Sequencing of rifampicin-resistant (RIF-R) clinical isolates of Mycobacterium tuberculosis revealed, in addition to RIF-R mutations, enrichment of potential compensatory mutations around the double-psi ß-barrel domain of the ß' subunit comprising the catalytic site and the exit tunnel for newly synthesized RNA. Sequential introduction of the resistance allele followed by the compensatory allele in isogenic Mycobacterium smegmatis showed that these mutations respectively caused and compensated a starvation enhanced growth defect by altering RNA polymerase activity. While specific combinations of resistance and compensatory alleles converged in divergent lineages, other combinations recurred among related isolates suggesting transmission of compensated RIF-R strains. These findings suggest nutrient poor growth conditions impose larger selective pressure on RIF-R organisms that results in the selection of compensatory mutations in a domain involved in catalysis and starvation control of RNA polymerase transcription.

Evolving practice: X-linked agammaglobulinemia and lung transplantation.

X-linked agammaglobulinemia (XLA) is a rare primary humoral immunodeficiency syndrome characterized by agammaglobulinemia, recurrent infections and bronchiectasis. Despite the association with end-stage bronchiectasis, the literature on XLA and lung transplantation is extremely limited. We report a series of 6 XLA patients with bronchiectasis who underwent lung transplantation. Short-term outcomes were excellent however long-term outcomes were disappointing with a high incidence of pulmonary sepsis and chronic lung allograft dysfunction (CLAD).