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Scott A McConnell,1 Dharmik N Desai,1 Sejal P Faldu,1 Marjie L Hard,2 Angela Y Wehr,3 Peter J Weiden,1 Lisa von Moltke3 1Medical Affairs, Alkermes, Inc., Waltham, MA, 2Nuventra Pharma Sciences, Durham, NC, 3Clinical Research, Alkermes, Inc., Waltham, MA, USAThe recent publication by Salzman et al1 compared pharmacokinetic (PK) data from population PK (popPK) models for two long-acting antipsychotic formulations: aripiprazole once-monthly 400 mg (AOM 400) and aripiprazole lauroxil (AL). We would like to address a few major concerns. The AL popPK model has been well described in a peer-reviewed publication.2 However, Salzman et al omitted publishing information regarding the development and validation of the AOM popPK model, including any critical discussion of the covariates, other key characteristics, assumptions and limitations of the AOM model. Thus, a reader cannot objectively assess the simulated values for AOM reported in the publication.View the original paper by Salzman and colleagues.

The use of decision trees and artificial neural networks (ANNs) in health-care research is widespread, as they enable health-care providers with the tools they need to make better medical decisions with their patients. ANNs specifically are extremely helpful in predictive research as they can provide investigators with knowledge about future trends and patterns. However, a major downside to ANNs is their lack of interpretability. Understandability of the model is important as it ensures the outcomes are true to the dataset’s original labels and are not impacted by algorithmic bias. In comparison, decision trees map out their entire process before providing the results, which leads to a higher level of trust in the model and the conclusions it supplies the investigators with. This is essential as many historical datasets lack equal and fair representation of all races and sexes, which might directly correlate to a lesser treatment given to females and individuals in minority groups. Here, we review existing work around the differences and connections between ANNs and decision trees with implications for research in health care.

Twelve healthy volunteers were enrolled in an open-label, randomized, crossover study. Subjects received single doses of theophylline (t mg/kg) alone and after a 10 day course of dirithromycin (two 250 mg tablets od). The study phases were separated by a 3 week washout period. Serum samples were collected before and for 24 h after theophylline doses. Serum theophylline concentrations were measured via a validated immunoassay system and the data were modelled via noncompartmental analysis. When the control phase (i.e. no dirithromycin) was compared with the treatment phase (i.e. with dirithromycin), theophylline exposures as measured by AUC0→∞ were not significantly different: 141.7 ± 25.9 and 136.4 ± 33.1 mg[sdot ]h/L respectively (P = 0.16). No significant changes in other theophylline pharmacokinetic parameters were evident. These results indicate that theophylline can be safely co-administered with dirithromycin, [ABSTRACT FROM PUBLISHER]

Constant domains in antibody molecules at the level of the Fab (C H 1 and C L ) have long been considered to be simple scaffolding elements that physically separate the paratope-defining variable (V) region from the effector function-mediating constant (C) regions. However, due to recent findings that C domains of different isotypes can modulate the fine specificity encoded in the V region, elucidating the role of C domains in shaping the paratope and influencing specificity is a critical area of interest. To dissect the relative contributions of each C domain to this phenomenon, we generated antibody fragments with different C regions omitted, using a set of antibodies targeting capsular polysaccharides from the fungal pathogen, Cryptococcus neoformans. Antigen specificity mapping and functional activity measurements revealed that V region-only antibody fragments exhibited poly-specificity to antigenic variants and extended to recognition of self-antigens, while measurable hydrolytic activity of the capsule was greatly attenuated. To better understand the mechanistic origins of the remarkable loss of specificity that accompanies the removal of C domains from identical paratopes, we performed molecular dynamics simulations which revealed increased paratope plasticity in the scFv relative to the corresponding Fab. Together, our results provide insight into how the remarkable specificity of immunoglobulins is governed and maintained at the level of the Fab through the enforcement of structural restrictions on the paratope by C H 1 domains., Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Antibodies play a vital role in the immune response to infectious diseases and can be administered passively to protect patients. In the case of Cryptococcus neoformans , a WHO critical priority fungal pathogen, infection results in antibodies targeting capsular glucuronoxylomannan (GXM). These antibodies yield protective, non-protective, and disease-enhancing outcomes when administered passively. However, it was unknown how these distinct antibodies recognized their antigens at the molecular level, leading to the hypothesis that they may target different GXM epitopes. To test this hypothesis, we constructed a microarray containing 26 glycans representative of those found in highly virulent cryptococcal strains and utilized it to study 16 well-characterized monoclonal antibodies. Notably, we found that protective and non-protective antibodies shared conserved reactivity to the M2 motif of GXM, irrespective of the strain used in infection or GXM-isolated to produce a conjugate vaccine. Here, only two antibodies, 12A1 and 18B7, exhibited diverse trivalent GXM motif reactivity. IgG antibodies associated with protective responses showed cross-reactivity to at least two GXM motifs. This molecular understanding of antibody binding epitopes was used to map the antigenic diversity of two Cryptococcus neoformans strains, which revealed the exceptional complexity of fungal capsular polysaccharides. A multi-GXM motif vaccine holds the potential to effectively address this antigenic diversity. Collectively, these findings underscore the context-dependent nature of antibody function and challenge the classification of anti-GXM epitopes as either "protective" or "non-protective".

One of the standard assays for the fungal pathogen Cryptococcus neoformans is the glucuronoxylomannan (GXM) ELISA. This assay utilizes monoclonal antibodies targeted against the critical virulence factor, the polysaccharide (PS) capsule. GXM ELISA is one of the most used assays in the field used for diagnosis of cryptococcal infection, quantification of PS content, and determination of binding specificity for antibodies. Here we present three variations of the GXM ELISA used by our group-indirect, capture, and competition ELISAs. We have also provided some history, perspective, and notes on these methods, which we hope will help the reader choose, and implement, the best assay for their research.While it has long been referred to as the GXM ELISA, we also suggest a name update to better reflect our updated understanding of the polysaccharide antigens targeted by this assay. The Cryptococcal PS ELISA is a more accurate description of this set of methodologies and the antigens they measure. Finally, we discuss the limitations of this assay and put forth future plans for expanding the antigens assayed by ELISA., (© 2024. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

Many species of pathogenic gram-positive bacteria display covalently crosslinked protein polymers (called pili or fimbriae) that mediate microbial adhesion to host tissues. These structures are assembled by pilus-specific sortase enzymes that join the pilin components together via lysine-isopeptide bonds. The archetypal SpaA pilus from Corynebacterium diphtheriae is built by the Cd SrtA pilus-specific sortase, which crosslinks lysine residues within the SpaA and SpaB pilins to build the shaft and base of the pilus, respectively. Here, we show that Cd SrtA crosslinks SpaB to SpaA via a K139(SpaB)-T494(SpaA) lysine-isopeptide bond. Despite sharing only limited sequence homology, an NMR structure of SpaB reveals striking similarities with the N-terminal domain of SpaA ( N SpaA) that is also crosslinked by Cd SrtA. In particular, both pilins contain similarly positioned reactive lysine residues and adjacent disordered AB loops that are predicted to be involved in the recently proposed "latch" mechanism of isopeptide bond formation. Competition experiments using an inactive SpaB variant and additional NMR studies suggest that SpaB terminates SpaA polymerization by outcompeting N SpaA for access to a shared thioester enzyme-substrate reaction intermediate., (© 2023 Wiley Periodicals LLC.)

Understanding the mechanisms of antibody-mediated neutralization of SARS-CoV-2 is critical in combating the COVID-19 pandemic. Based on previous reports of antibody catalysis, we investigated the proteolysis of spike (S) by antibodies in COVID-19 convalescent plasma (CCP) and its contribution to viral neutralization. Quenched fluorescent peptides were designed based on S epitopes to sensitively detect antibody-mediated proteolysis. We observed epitope cleavage by CCP from different donors which persisted when plasma was heat-treated or when IgG was isolated from plasma. Further, purified CCP antibodies proteolyzed recombinant S domains, as well as authentic viral S. Cleavage of S variants suggests CCP antibody-mediated proteolysis is a durable phenomenon despite antigenic drift. We differentiated viral neutralization occurring via direct interference with receptor binding from that occurring by antibody-mediated proteolysis, demonstrating that antibody catalysis enhanced neutralization. These results suggest that antibody-catalyzed damage of S is an immunologically relevant function of neutralizing antibodies against SARS-CoV-2., Competing Interests: Declaration of interests None declared., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

A pet cockatoo was the suspected source of Cryptococcus neoformans recovered from an immunocompromised patient with cryptococcosis based on molecular analyses available in 2000. Here, we report whole genome sequence analysis of the clinical and cockatoo strains. Both are closely related MATα strains belonging to the VNII lineage, confirming that the human infection likely originated from pet bird exposure. The two strains differ by 61 single nucleotide polymorphisms, including eight nonsynonymous changes involving seven genes. To ascertain whether changes in these genes are selected for during mammalian infection, we passaged the cockatoo strain in mice. Remarkably, isolates obtained from mouse tissue possess a frameshift mutation in one of the seven genes altered in the human sample (LQVO5_000317), a gene predicted to encode an SWI-SNF chromatin-remodeling complex protein. In addition, both cockatoo and patient strains as well as mouse-passaged isolates obtained from brain tissue had a premature stop codon in a homologue of ZFC3 (LQVO5_004463), a predicted single-zinc finger containing protein, which is associated with larger capsules when deleted and reverted to a full-length protein in the mouse-passaged isolates obtained from lung tissue. The patient strain and mouse-passaged isolates show variability in virulence factors, with differences in capsule size, melanization, rates of nonlytic expulsion from macrophages, and amoeba predation resistance. Our results establish that environmental strains undergo genomic and phenotypic changes during mammalian passage, suggesting that animal virulence can be a mechanism for genetic change and that the genomes of clinical isolates may provide a readout of mutations acquired during infection.

Microbial polysaccharide characterization requires purification that often involves detergent precipitation and lyophilization. Here we examined physicochemical changes following lyophilization of Cryptococcus neoformans exopolysaccharide (EPS). Solution 1 H Nuclear Magnetic Resonance (NMR) reveals significant anomeric signal attenuation following lyophilization of native EPS while 1 H solid-state Nuclear Magnetic Resonance (ssNMR) shows few changes, suggesting diminished molecular motion and consequent broadening of 1 H NMR polysaccharide resonances. 13 C ssNMR, dynamic light scattering, and transmission electron microscopy show that, while native EPS has rigid molecular characteristics and contains small, loosely packed polysaccharide assemblies, lyophilized and resuspended EPS is disordered and contains larger dense aggregates, suggesting that structural water molecules in the interior of the polysaccharide assemblies are removed during extensive lyophilization. Importantly, mAbs to C. neoformans polysaccharide bind native EPS more strongly than lyophilized EPS. Together, these observations argue for caution when interpreting the biological and immunological attributes of polysaccharides that have been lyophilized to dryness., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The polysaccharide capsule of fungal pathogen Cryptococcus neoformans is a critical virulence factor that has historically evaded complete characterization. Cryptococcal polysaccharides are known to either remain attached to the cell as capsular polysaccharides (CPSs) or to be shed into the extracellular space as exopolysaccharides (EPSs). While many studies have examined the properties of EPS, far less is known about CPS. In this work, we detail the development of new physical and enzymatic methods for the isolation of CPS which can be used to explore the architecture of the capsule and isolated capsular material. We show that sonication or Glucanex enzyme cocktail digestion yields soluble CPS preparations, while use of a French pressure cell press or Glucanex digestion followed by cell disruption removed the capsule and produced cell wall-associated polysaccharide aggregates that we call "capsule ghosts", implying an inherent organization that allows the CPS to exist independent of the cell wall surface. Since sonication and Glucanex digestion were noncytotoxic, it was also possible to observe the cryptococcal cells rebuilding their capsule, revealing the presence of reducing end glycans throughout the capsule. Finally, analysis of dimethyl sulfoxide-extracted and sonicated CPS preparations revealed the conservation of previously identified glucuronoxylomannan motifs only in the sonicated CPS. Together, these observations provide new insights into capsule architecture and synthesis, consistent with a model in which the capsule is assembled from the cell wall outward using smaller polymers, which are then compiled into larger ones., Competing Interests: Conflict of interest The authors have no conflicts of interest to report., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Gram-positive bacteria assemble pili (fimbriae) on their surfaces to adhere to host tissues and to promote polymicrobial interactions. These hair-like structures, although very thin (1 to 5 nm), exhibit impressive tensile strengths because their protein components (pilins) are covalently crosslinked together via lysine-isopeptide bonds by pilus-specific sortase enzymes. While atomic structures of isolated pilins have been determined, how they are joined together by sortases and how these interpilin crosslinks stabilize pilus structure are poorly understood. Using a reconstituted pilus assembly system and hybrid structural biology methods, we elucidated the solution structure and dynamics of the crosslinked interface that is repeated to build the prototypical SpaA pilus from Corynebacterium diphtheriae We show that sortase-catalyzed introduction of a K190-T494 isopeptide bond between adjacent SpaA pilins causes them to form a rigid interface in which the LPLTG sorting signal is inserted into a large binding groove. Cellular and quantitative kinetic measurements of the crosslinking reaction shed light onto the mechanism of pilus biogenesis. We propose that the pilus-specific sortase in C. diphtheriae uses a latch mechanism to select K190 on SpaA for crosslinking in which the sorting signal is partially transferred from the enzyme to a binding groove in SpaA in order to facilitate catalysis. This process is facilitated by a conserved loop in SpaA, which after crosslinking forms a stabilizing latch that covers the K190-T494 isopeptide bond. General features of the structure and sortase-catalyzed assembly mechanism of the SpaA pilus are likely conserved in Gram-positive bacteria., Competing Interests: The authors declare no competing interest.

Classic antibody functions include opsonization, complement activation, and enhancement of cellular antimicrobial function. Antibodies can also have catalytic activity, although the contribution of catalysis to their biological functions has been more difficult to establish. With the ubiquity of catalytic antibodies against glycans virtually unknown, we sought to advance this knowledge. The use of a glycan microarray allowed epitope mapping of several monoclonal antibodies (mAbs) against the capsule of Cryptococcus neoformans From this, we designed and synthesized two glycan-based FRET probes, which we used to discover antibodies with innate glycosidase activity and analyze their enzyme kinetics, including mAb 2H1, the most efficient identified to date. The validity of the FRET assay was confirmed by demonstrating that the mAbs mediate glycosidase activity on intact cryptococcal capsules, as observed by a reduction in capsule diameter. Furthermore, the mAb 18B7, a glycosidase hydrolase, resulted in the appearance of reducing ends in the capsule as labeled by a hydroxylamine-armed fluorescent (HAAF) probe. Finally, we demonstrate that exposing C. neoformans cells to catalytic antibodies results in changes in complement deposition and increased phagocytosis by macrophages, suggesting that the antiphagocytic properties of the capsule have been impaired. Our results raise questions over the ubiquity of antibodies with catalytic activity against glycans and establish the utility of glycan-based FRET and HAAF probes as tools for investigating this activity., Competing Interests: The authors declare no competing interest.

Opioid use disorder imposes great societal harm in the United States and in countries worldwide. Animal models that accurately capture motivational changes that occur in opioid dependence are critical to studying this disorder. The present study used a model of opioid vapor self-administration combined with a behavioral economics approach to determine whether rats would be more motivated to "work" to defend their baseline intake of fentanyl (i.e., more inelastic demand) following sufficiently frequent, intense, and chronic exposure to self-administered vaporized fentanyl. Male rats were allowed to respond for deliveries of 1.5-s of vaporized 10 mg/ml fentanyl solution. Following 15 sessions of short access (ShA; 1 h) vs. long access (LgA; 12 h) to self-administration, we conducted a between-sessions demand curve procedure, and observed significantly more inelastic demand for fentanyl (Essential Value; EV), and increased maximal response output (O max ) in LgA compared with ShA rats. In a subsequent phase, the unit-dose was doubled to 3 s of fentanyl vaporization. After seven ShA vs. LgA sessions, we assessed demand again and found that LgA rats, contrasted to ShA rats, demonstrated significantly higher baseline intake or "hedonic setpoint" (Q 0 ), in addition to significantly increased EV and O max . These results demonstrate that extended access to self-administration of a vaporized opioid causes changes in behavioral economic metrics consistent with development of an addiction-like state in rats. The combination of the vapor model with a translationally relevant behavioral economics framework opens new avenues to study dysregulated motivational processes in substance use disorders., (Published by Elsevier Ltd.)

Site-specifically modified protein bioconjugates have important applications in biology, chemistry, and medicine. Functionalizing specific protein side chains with enzymes using mild reaction conditions is of significant interest, but remains challenging. Recently, the lysine-isopeptide bond forming activity of the sortase enzyme that builds surface pili in Corynebacterium diphtheriae ( Cd SrtA) has been reconstituted in vitro . A mutationally activated form of Cd SrtA was shown to be a promising bioconjugating enzyme that can attach Leu-Pro-Leu-Thr-Gly peptide fluorophores to a specific lysine residue within the N-terminal domain of the SpaA protein ( N SpaA), enabling the labeling of target proteins that are fused to N SpaA. Here we present a detailed analysis of the Cd SrtA catalyzed protein labeling reaction. We show that the first step in catalysis is rate limiting, which is the formation of the Cd SrtA-peptide thioacyl intermediate that subsequently reacts with a lysine ε-amine in N SpaA. This intermediate is surprisingly stable, limiting spurious proteolysis of the peptide substrate. We report the discovery of a new enzyme variant ( Cd SrtA Δ ) that has significantly improved transpeptidation activity, because it completely lacks an inhibitory polypeptide appendage ("lid") that normally masks the active site. We show that the presence of the lid primarily impairs formation of the thioacyl intermediate and not the recognition of the N SpaA substrate. Quantitative measurements reveal that Cd SrtA Δ generates its cross-linked product with a catalytic turnover number of 1.4 ± 0.004 h -1 and that it has apparent K M values of 0.16 ± 0.04 and 1.6 ± 0.3 mM for its N SpaA and peptide substrates, respectively. Cd SrtA Δ is 7-fold more active than previously studied variants, labeling >90% of N SpaA with peptide within 6 h. The results of this study further improve the utility of Cd SrtA as a protein labeling tool and provide insight into the enzyme catalyzed reaction that underpins protein labeling and pilus biogenesis.

The functions of enzymes can be strongly affected by their higher-order spatial arrangements. In this study we combine multiple new technologies-designer protein cages and sortase-based enzymatic attachments between proteins-as a novel platform for organizing multiple enzymes (of one or more types) in specified configurations. As a scaffold we employ a previously characterized 24-subunit designed protein cage whose termini are outwardly exposed for attachment. As a first-use case, we test the attachment of two cellulase enzymes known to act synergistically in cellulose degradation. We show that, after endowing the termini of the cage subunits with a short "sort-tag" sequence (LPXTG) and the opposing termini of the cellulase enzymes with a short polyglycine sequence tag, addition of sortase covalently attaches the enzymes to the cage with good reactivity and high copy number. The doubly modified cages show enhanced activity in a cellulose degradation assay compared to enzymes in solution, and compared to a combination of singly modified cages. These new engineering strategies could be broadly useful in the development of enzymatic material and synthetic biology applications.

Oxytocin administration has been reported to decrease consumption, withdrawal, and drug-seeking associated with several drugs of abuse and thus represents a promising pharmacological approach to treat drug addiction. We used an established rat model of alcohol dependence to investigate oxytocin's effects on dependence-induced alcohol drinking, enhanced motivation for alcohol, and altered GABAergic transmission in the central nucleus of the amygdala (CeA). Intraperitoneal oxytocin administration blocked escalated alcohol drinking and the enhanced motivation for alcohol in alcohol-dependent but not nondependent rats. Intranasal oxytocin delivery fully replicated these effects. Intraperitoneal administration had minor but significant effects of reducing locomotion and intake of non-alcoholic palatable solutions, whereas intranasal oxytocin administration did not. In dependent rats, intracerebroventricular administration of oxytocin or the oxytocin receptor agonist PF-06655075, which does not cross the blood-brain barrier (i.e., it would not diffuse to the periphery), but not systemic administration of PF-06655075 (i.e., it would not reach the brain), decreased alcohol drinking. Administration of a peripherally restricted oxytocin receptor antagonist did not reverse the effect of intranasal oxytocin on alcohol drinking. Ex vivo electrophysiological recordings from CeA neurons indicated that oxytocin decreases evoked GABA transmission in nondependent but not in dependent rats, whereas oxytocin decreased the amplitude of spontaneous GABAergic responses in both groups. Oxytocin blocked the facilitatory effects of acute alcohol on GABA release in the CeA of dependent but not nondependent rats. Together, these results provide converging evidence that oxytocin specifically and selectively blocks the enhanced motivation for alcohol drinking that develops in alcohol dependence likely via a central mechanism that may result from altered oxytocin effects on CeA GABA transmission in alcohol dependence. Neuroadaptations in endogenous oxytocin signaling may provide a mechanism to further our understanding of alcohol use disorder., Competing Interests: The authors have declared that no competing interests exist.

Aims: The development of novel and more effective medications for alcohol use disorder (AUD) is an important unmet medical need. Drug repositioning or repurposing is an appealing strategy to bring new therapies to the clinic because it greatly reduces the overall costs of drug development and expedites the availability of treatments to those who need them. Probenecid, p-(di-n-propylsulfamyl)-benzoic acid, is a drug used clinically to treat hyperuricemia and gout due to its activity as an inhibitor of the kidneys' organic anion transporter that reclaims uric acid from urine. Probenecid also inhibits pannexin1 channels that are involved in purinergic neurotransmission and inflammation, which have been implicated in alcohol's effects and motivation for alcohol. Therefore, we tested the effects of probenecid on alcohol intake in rodents., Methods: We tested the effects of probenecid on operant oral alcohol self-administration in alcohol-dependent rats during acute withdrawal as well as in nondependent rats and in the drinking-in-the-dark (DID) paradigm of binge-like drinking in mice., Results: Probenecid reduced alcohol intake in both dependent and nondependent rats and in the DID paradigm in mice without affecting water or saccharin intake, indicating that probenecid's effect was selective for alcohol and not the result of a general reduction in reward., Conclusions: These results raise the possibility that pannexin1 is a novel therapeutic target for the treatment of AUD. The clinical use of probenecid has been found to be generally safe, suggesting that it can be a candidate for drug repositioning for the treatment of AUD., (© The Author(s) 2019. Medical Council on Alcohol and Oxford University Press. All rights reserved.)

Proteins that are site-specifically modified with peptides and chemicals can be used as novel therapeutics, imaging tools, diagnostic reagents and materials. However, there are few enzyme-catalyzed methods currently available to selectively conjugate peptides to internal sites within proteins. Here we show that a pilus-specific sortase enzyme from Corynebacterium diphtheriae ( Cd SrtA) can be used to attach a peptide to a protein via a specific lysine-isopeptide bond. Using rational mutagenesis we created Cd SrtA 3M , a highly activated cysteine transpeptidase that catalyzes in vitro isopeptide bond formation. Cd SrtA 3M mediates bioconjugation to a specific lysine residue within a fused domain derived from the corynebacterial SpaA protein. Peptide modification yields greater than >95% can be achieved. We demonstrate that Cd SrtA 3M can be used in concert with the Staphylococcus aureus SrtA enzyme, enabling dual, orthogonal protein labeling via lysine-isopeptide and backbone-peptide bonds.

Covalently cross-linked pilus polymers displayed on the cell surface of Gram-positive bacteria are assembled by class C sortase enzymes. These pilus-specific transpeptidases located on the bacterial membrane catalyze a two-step protein ligation reaction, first cleaving the LPXTG motif of one pilin protomer to form an acyl-enzyme intermediate and then joining the terminal Thr to the nucleophilic Lys residue residing within the pilin motif of another pilin protomer. To date, the determinants of class C enzymes that uniquely enable them to construct pili remain unknown. Here, informed by high-resolution crystal structures of corynebacterial pilus-specific sortase (SrtA) and utilizing a structural variant of the enzyme (SrtA 2M ), whose catalytic pocket has been unmasked by activating mutations, we successfully reconstituted in vitro polymerization of the cognate major pilin (SpaA). Mass spectrometry, electron microscopy, and biochemical experiments authenticated that SrtA 2M synthesizes pilus fibers with correct Lys-Thr isopeptide bonds linking individual pilins via a thioacyl intermediate. Structural modeling of the SpaA-SrtA-SpaA polymerization intermediate depicts SrtA 2M sandwiched between the N- and C-terminal domains of SpaA harboring the reactive pilin and LPXTG motifs, respectively. Remarkably, the model uncovered a conserved TP(Y/L)XIN(S/T)H signature sequence following the catalytic Cys, in which the alanine substitutions abrogated cross-linking activity but not cleavage of LPXTG. These insights and our evidence that SrtA 2M can terminate pilus polymerization by joining the terminal pilin SpaB to SpaA and catalyze ligation of isolated SpaA domains in vitro provide a facile and versatile platform for protein engineering and bio-conjugation that has major implications for biotechnology., Competing Interests: The authors declare no conflict of interest.

One major difference between limb and extraocular muscles (EOM) is the presence of an enriched population of Pitx2-positive myogenic precursor cells in EOM compared to limb muscle. We hypothesize that retinoic acid regulates Pitx2 expression in EOM myogenic precursor cells and that its effects would differ in leg muscle. The two muscle groups expressed differential retinoic acid receptor (RAR) and retinoid X receptor (RXR) levels. RXR co-localized with the Pitx2-positive cells but not with those expressing Pax7. EOM-derived and LEG-derived EECD34 cells were treated with vehicle, retinoic acid, the RXR agonist bexarotene, the RAR inverse agonist BMS493, or the RXR antagonist UVI 3003. In vitro, fewer EOM-derived EECD34 cells expressed desmin and fused, while more LEG-derived cells expressed desmin and fused when treated with retinoic acid compared to vehicle. Both EOM and LEG-derived EECD34 cells exposed to retinoic acid showed a higher percentage of cells expressing Pitx2 compared to vehicle, supporting the hypothesis that retinoic acid plays a role in maintaining Pitx2 expression. We hypothesize that retinoic acid signaling aids in the maintenance of large numbers of undifferentiated myogenic precursor cells in the EOM, which would be required to maintain EOM normalcy throughout a lifetime of myonuclear turnover., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Many species of Gram-positive bacteria use sortase enzymes to assemble long, proteinaceous pili structures that project from the cell surface to mediate microbial adhesion. Sortases construct highly stable structures by catalyzing a transpeptidation reaction that covalently links pilin subunits together via isopeptide bonds. Most Gram-positive pili are assembled by class C sortases that contain a "lid", a structurally unique N-terminal extension that occludes the active site. It has been hypothesized that the "lid" in many sortases is mobile and thus capable of readily being displaced from the enzyme to facilitate substrate binding. Here, we show using NMR dynamics measurements, in vitro assays, and molecular dynamics simulations that the lid in the class C sortase from Streptococcus pneumoniae (SrtC1) adopts a rigid conformation in solution that is devoid of large magnitude conformational excursions that occur on mechanistically relevant time scales. Additionally, we show that point mutations in the lid induce dynamic behavior that correlates with increased hydrolytic activity and sorting signal substrate access to the active site cysteine residue. These results suggest that the lid of the S. pneumoniae SrtC1 enzyme has a negative regulatory function and imply that a significant energetic barrier must be surmounted by currently unidentified factors to dislodge it from the active site to initiate pilus biogenesis.

Purpose: The goal of this study was to describe the outcomes associated with daptomycin treatment of documented gram-positive infections in patients with neutropenia., Methods: All patients with neutropenia (≤500 cells/m(3)) and at least one documented gram-positive culture from 2006-2009 were identified from a retrospective, multicenter, and observational registry (Cubicin(®) Outcome Registry and Experience (CORE(®))). Investigators assessed patient outcome (cured, improved, failed, nonevaluable) at the end of daptomycin therapy. All patients were included in the safety analysis., Results: The efficacy population had 186 patients; 159 (85 %) patients had either cure (n = 108, 58 %) or improved (n = 51, 27 %) as an outcome. Success rates (cure plus improved) by the lowest WBC during daptomycin were 98/116 (84 %) for ≤100 cells/m(3) and 61/70 (87 %) for 101-499 cells/m(3), P = 0.6. Most patients had cancer; 135/186 (73 %) had hematological malignancy; 26/186 (14 %) had solid tumors, and 9 (5 %) had both. One hundred fifty-six (84 %) patients received other antibiotics before daptomycin treatment; 82 % vancomycin, of which 31 % failed vancomycin. The most common infections were bacteremia (78 %), skin and skin structure infections (8 %), and urinary tract infections/pyelonephritis (6 %). The most common pathogens were vancomycin-resistant Enterococcus faecium (47 %), methicillin-resistant Staphylococcus aureus (20 %), and coagulase-negative staphylococci (19 %). The median (min, max) initial daptomycin dose was 6 mg/kg (3.6, 8.3). The median (min, max) daptomycin duration of therapy was 14 days (1, 86). Possibly related adverse events occurred in 12/209 patients (6 %), and 13 patients (6 %) discontinued daptomycin due to adverse event., Conclusions: The results suggest that daptomycin appeared useful and well tolerated in neutropenic patients, and the degree of neutropenia did not affect daptomycin success rates. Comparative clinical trials are needed to confirm these findings.

Background: Daptomycin is a rapidly bactericidal agent with broad coverage against Gram-positive organisms, including Staphylococcus aureus, the most frequent cause of osteomyelitis. The objective of this study was to describe the clinical outcome of patients with non-hardware associated osteomyelitis, and the safety profile of daptomycin in the treatment of these infections., Methods: All patients with osteomyelitis, excluding concurrent orthopedic foreign body infections, treated with daptomycin and identified between 2007-2008 in a retrospective, multicenter, observational registry, were included. Investigators assessed patient outcome (cured, improved, failed, non-evaluable) at the end of daptomycin therapy. Patients with a successful outcome at the end of daptomycin therapy were reassessed in 2009. All patients were included in the safety analysis; evaluable patients were included in the efficacy analysis. Data was assessed using descriptive statistics. A Kaplan Meier analysis was used to assess time to clinical failure., Results: Two-hundred and nine osteomyelitis patients successfully completed daptomycin therapy in 2007-2008, 71 of which (34%) had a follow-up visit in 2009 and had an evaluable clinical outcome. The median (min, max) daptomycin dose and duration were 6 mg/kg (4, 10) and 42 days (1, 88), respectively. Of the 52 patients with a documented pathogen, S. aureus was the most common (42%); primarily methicillin-resistant S. aureus. All patients were included in the safety analysis; evaluable patients were included in the efficacy analysis. Clinical resolution was reported in 94% (CI - 86.2%, 98.44%) of patients. A Kaplan Meier analysis of time to clinical failure showed that approximately 85% (CI - 64%, 95%) of patients had a continued successful outcome at the time of re-evaluation. Eighteen patients (25%) in the safety population experienced an adverse event; 13 patients (18%) had an adverse event that was possibly-related to daptomycin treatment., Conclusions: Daptomycin appears to be an effective therapeutic choice with an acceptable safety profile in the management of osteomyelitis that does not involve hardware.

Clinical data for daptomycin in the treatment of neutropenic cancer patients with documented gram-positive infections are limited. For this study, neutropenic patients were identified from an ongoing retrospective registry (Cubicin Outcome Registry and Experience [CORE]; 2006 program year). Clinical outcomes included cure, improved, failed, and nonevaluable response, and were assessed at the end of daptomycin therapy. Patients who had a nonevaluable clinical response were only included in the safety analysis. Eighty-four patients were identified, of which 72 (86%) were clinically evaluable. Thirty-four (47%) evaluable patients had severe neutropenia (less than 100 cells/mm(3)). Hematologic malignancies were most common (82%). Bacteremia was the most common infection (76%), and vancomycin-resistant enterococci (50%), coagulase-negative staphylococci (24%), and Staphylococcus aureus (11%) were the most common pathogens isolated. Sixty-three patients (88%) received prior antibiotics, including vancomycin (83%), cefepime (17%), and linezolid (16%). The overall success rate (cure + improved) was 90%. Success rates stratified by degree of neutropenia were 85% for patients with less than 100 cells/mm(3), 93% for those with 100-499 cells/mm(3), and 100% for those with 500-1,000 cells/mm(3). The median final daptomycin dose was 6 mg/kg (range, 3-8) and the median duration of therapy was 13 days (range, 1-86). Of the 84 patients analyzed for safety, 24 (29%) developed 44 adverse events; only 5 (6%) patients had adverse events possibly related to daptomycin. The results suggest that daptomycin may be useful for specific cases involving neutropenic patients, and comparative clinical trials are feasible.

The pharmacokinetics and safety of extended-interval dosing of prophylactic liposomal amphotericin B (L-AMB) in peripheral stem cell transplant recipients were evaluated. The patients received L-AMB daily at 1 mg/kg of body weight or weekly at 7.5 mg/kg or received L-AMB as a single dose (15 mg/kg). The buccal mucosal tissue concentrations of L-AMB were measured. Of the 24 patients enrolled, 5 withdrew after the initial dose due to an infusion-related reaction (n = 2) or significant increases in the serum creatinine (Scr) levels (n = 3). Weekly L-AMB dosing (7.5 mg/kg) produced mean plasma concentrations of >0.300 microg/ml for the first 7 days and >0.220 microg/ml for 7 days after the second dose. A single L-AMB dose (15 mg/kg) produced mean plasma concentrations of >0.491 microg/ml for at least 7 seven days. These concentrations are within the range of the MICs reported in the literature for susceptible strains of Candida and are at the lower limits of the MICs for Aspergillus spp. Extended-interval dosing produced buccal mucosal tissue concentrations well in excess of the MICs reported in the literature for susceptible strains of Candida and Aspergillus spp. Infusion-related reactions occurred in 24% of the patients. Baseline and end-of-study Scr, electrolyte (K+, Mg2+, PO4), and serum transaminase levels were similar across the dosage groups. Five (31%) patients met the nephrotoxicity definition prior to completion of the study. Patients in the weekly or single-dose groups experienced nephrotoxicity significantly faster than the patients in the daily dosing cohort. A weekly L-AMB dose (7.5 mg/kg) or a single L-AMB dose (15 mg/kg) produced sufficient concentrations in plasma and highly vascular tissue to warrant further studies of the safety, efficacy, and practicality of the weekly prophylactic administration of L-AMB.

Antibiotic safety is a major determinant in osteomyelitis therapy. Limited data is available describing the long-term safety and efficacy of daptomycin. the safety population was drawn from CORE 2005 and 2006, a retrospective, observational, multicenter study. Clinically evaluable patients received >3 days of daptomycin appropriately adjusted for renal function. three hundred twenty-seven patients were evaluated for safety; 188 (57%) >or=6 mg/kg, 139 (43%) <6 mg/kg. Thirty-one (10%) patients experienced adverse events possibly related to daptomycin and the incidence was similar regardless of dose. No difference was observed in the rate of creatine phosphokinase elevations by dose. A trend toward higher improved rates was noted in patients receiving a final dose of >or=6mg/kg (96% vs. 90%, P=0.08). Daptomycin appeared well-tolerated at doses of 6 mg per kg or greater which were associated with greater clinical improvement. These results require verification via a prospective clinical trial.

Objective: To explore whether sex-related differences in intestinal itraconazole metabolism exist in healthy adults using grapefruit juice (GFJ) as a selective enteric cytochrome P450 3A4 (CYP3A4) inhibitor., Methods: Twenty (ten female) subjects received 240 mL bottled water or single-strength GFJ from a frozen concentrate three times daily for 2 days. On day 3, the subjects received an itraconazole oral solution 200 mg with 240 mL of beverage followed 2 h later by 240 mL of the same beverage. Serial blood sampling for itraconazole and hydroxyitraconazole serum concentrations was performed over a 72-h period. After a 20-day washout, the subjects crossed over and repeated the study., Results: Among the female subjects, GFJ reduced itraconazole weight-adjusted apparent oral clearance (Cl/F) (19%, p = 0.006) and increased AUC(0-infinity) (30%, p = 0.01), but produced no significant change in hydroxyitraconazole pharmacokinetics. In males, GFJ produced no significant change in either itraconazole, or hydroxyitraconazole pharmacokinetics. Grapefruit juice also significantly reduced the metabolite:parent AUC(0-infinity) ratio (12%, p = 0.047), in females, but not males. Itraconazole weight-adjusted oral Cl/F was significantly higher in females than males when itraconazole was administered with water (56%, p = 0.009), and although the extent to which GFJ altered itraconazole weight-adjusted oral CL/F was greater in females, it did not differ significantly between the sexes (p = 0.085)., Results: The influence of GFJ on the presystemic metabolism of itraconazole was greater in females than males. Repeated ingestion of GFJ significantly reduced itraconazole weight-adjusted oral CL/F and significantly increased exposure in females, but it produced no significant change among males. Although itraconazole weight-adjusted oral Cl/F was much higher in females than in males, the extent to which GFJ altered itraconazole weight-adjusted oral CL/F did not differ significantly between the sexes.

Significant controversy surrounds the usefulness of central venous catheters (CVCs) impregnated with antimicrobial agents (A-CVCs) for the prevention of catheter-related bloodstream infections (CRBSIs). In a recent issue of Clinical Infectious Diseases, we reviewed 11 published trials of A-CVCs versus uncoated CVCs, and we concluded that there is a lack of solid evidence to support a benefit of A-CVCs in reducing the rate of CRBSIs. A response to our review was recently published in Clinical Infectious Diseases. In this response, our colleagues assert that there is a large body of evidence that demonstrates a powerful decrease in the risk of infection, and they conclude that we should not waste precious resources while we perform additional research to confirm what we have already found to be true. Although these authors agree with us on the significant shortcomings of the studies used to support the use of A-CVCs, they dismiss the need for additional trials to demonstrate that the use of A-CVCs does reduce infections. This dismissal, however, cannot be justified, because of the existence of an ongoing, federally supported, multicenter, prospective, placebo-controlled trial, led by our colleagues, that compares the rate of CRBSIs among patients randomized to receive either an A-CVC or a "placebo" uncoated CVC. That our colleagues are leading a trial that assesses the efficacy of A-CVCs versus placebo uncoated CVCs supports our viewpoint that the truth regarding the protective role of A-CVCs has yet to be determined. Because of the significant cost, potential toxicity, and risk of increased antimicrobial resistance associated with the use of A-CVCs, and until the results of the important trial conducted by our colleagues convincingly demonstrate that A-CVCs reduce the rate of clinically significant events (not just catheter colonization), we recommend that the use of A-CVCs be limited to investigational settings.

Study Objective: To evaluate the effect of repeated ingestion of grapefruit juice on the systemic availability of itraconazole (ITZ) and hydroxyitraconazole (OHITZ) serum concentrations in subjects administered hydroxypropyl-beta-cyclodextrin-ITZ (HP-beta-CD ITZ) oral solution., Design: Randomized, two-period, crossover study., Setting: College of pharmacy research unit., Subjects: Twenty healthy, adult volunteers (10 men, 10 women)., Intervention: Subjects received 240 ml of regular-strength grapefruit juice from frozen concentrate or bottled purified water 3 times/day for 2 days. On the third day they received a single dose of HP-beta-CD ITZ oral solution 200 mg (20 ml) with 240 ml of the beverage. Two hours after dosing they received another 240 ml of the beverage., Measurements and Main Results: Repeated blood samples were drawn for 72 hours after dosing. After a 14-day washout period, subjects were crossed over to the beverage they had not received previously and the above procedure was repeated. There was no difference in peak ITZ concentration (Cmax) or time to Cmax (Tmax). Coadministration of grapefruit juice reduced OHITZ Cmax nearly 10%, but this difference was not statistically significant. It produced a statistically significant increase in ITZ area under the concentration-time curves from 0-48 hours (AUC(0-48)) (17%) and from time zero extrapolated to infinity (AUC(0-infinity)) (19.5%). Apparent oral clearance of ITZ was significantly reduced (14%). Significant changes in OHITZ exposure were not observed; however, grapefruit juice coadministration produced statistically significant decreased mean OHITZ:ITZ AUC(0-48) and AUC(0-infinity) ratios. Grapefruit juice also decreased the mean OHITZ:ITZ Cmax ratio, but the difference was not statistically significant., Conclusion: Repeated grapefruit juice consumption moderately affects ITZ systemic availability in subjects administered HP-beta-CD ITZ oral solution. Unlike previous findings with ITZ capsules, changes in the disposition of ITZ and OHITZ after repeated grapefruit juice consumption are consistent with grapefruit juice inhibition of intestinal cytochrome P450 3A4.

Controversy surrounds the role of central venous catheters (CVCs) impregnated with antimicrobial agents in the prevention of catheter-related bloodstream infection (CRBSI). We reviewed the current literature to evaluate the efficacy of antimicrobial-impregnated CVCs for preventing CRBSI. Eleven randomized studies published in article form were identified that included a control group that received nonimpregnated CVCs. We evaluated study methodologies, inclusion of key patient characteristics, use of clinically relevant end points, and molecular-relatedness studies. Review of these 11 trials revealed several methodological flaws, including inconsistent definitions of CRBSI, failure to account for confounding variables, suboptimal statistical and epidemiological methods, and rare use of clinically relevant end points. This review also failed to demonstrate any significant clinical benefit associated with the use of antimicrobial-impregnated CVCs for the purpose of reducing CRBSI or improving patient outcomes. More rigorous studies are required to support or refute the hypothesis that antimicrobial-impregnated CVCs reduce the rate of or prevent CRBSI.

A potential cytokine-drug interaction between interleukin 6 (IL-6) and itraconazole (ITZ) was studied using human hepatocytes in primary culture. Cultures from 5 adult males (mean age 42 +/- 15 years) who had not received any medicines known to interact with CYP3A4 were studied. Cultures were exposed to ITZ 500 ng/ml, and the effects of 120 microg/ml cimetidine, 50 ng/ml human IL-6, or IL-6 plus IL-6 receptor antagonist were analyzed for 2, 4, 8, and 12 h. Intracellular ITZ and hydroxyitraconazole concentrations were measured using HPLC and normalized to total cellular protein. Mean intracellular concentrations between groups were compared using one-way Anova (f test; p < 0.10) and corresponding Bonferroni versus control test for multiple comparisons (p < 0.02). Mean intracellular ITZ concentrations between the groups were similar at all time points. Human hepatocytes in primary culture can metabolize ITZ. However, IL-6 did not inhibit hydroxyitraconazole formation, but it may inhibit its subsequent metabolism., (Copyright 2003 S. Karger AG, Basel)

Study Objective: To characterize amphotericin B-associated nephrotoxicity and to determine the variables associated with it that can be used to identify, a priori, at-risk patients., Design: Retrospective analysis., Setting: University hospital., Patients: A homogeneous population of 69 recipients of a bone marrow (BMT) or peripheral blood stem cell transplant (PBSCT) with multiple myeloma and who received at least two doses of amphotericin B deoxycholate from January 1, 1992-January 1, 1995., Intervention: Data on demographics, prior and concomitant nephrotoxic drug therapy, daily laboratory values, and amphotericin B dosing were collected serially from medical and pharmacy records., Measurements and Main Results: Forward stepwise logistic regression analysis was performed on the data from the first day of therapy to characterize and determine variables related to amphotericin B-associated nephrotoxicity. Nephrotoxicity occurred in 30 patients (43%) and developed rapidly Patients who developed nephrotoxicity were similar to those who did not in many aspects associated with their treatment. However, baseline estimated creatinine clearance, cyclosporine therapy, nephrotoxic drug therapy within 30 days of starting amphotericin B, and the number of concomitant nephrotoxic drugs were significant predictors of amphotericin B-associated nephrotoxicity., Conclusion: Recipients of a BMT or PBSCT who have multiple myeloma and are receiving cyclosporine or multiple nephrotoxic drugs at the start of amphotericin B therapy should be considered at high risk for developing amphotericin B-associated nephrotoxicity. Also, because amphotericin B-associated nephrotoxicity develops rapidly, clinicians should be aware of the rapid changes in serum creatinine and electrolyte levels that can occur.

The purpose of this retrospective study was to assess cross-hypersensitivity between imipenem/cilastatin and penicillin in patients with reported penicillin allergies. Medical records of febrile neutropenic, penicillin-allergic bone marrow transplant recipients who received imipenem/cilastatin treatment were retrospectively reviewed. The findings of this study indicate the incidence of cross-reactivity between imipenem/cilastatin and penicillin among patients with a history of penicillin allergy may be lower than previously reported.

In order to develop procedures to label the main bovine leucocyte populations in paraffin embedded sections, the immunoreactivity of 25 monoclonal antibodies (mAbs) to different leucocyte antigens was assessed with formal dichromate (FD5) and 10% formalin fixation, a battery of antigen retrieval (AR) methods, and the biotin-tyramide amplification system. All the leucocyte populations investigated (CD2+, CD4+, CD8+, WC1+ T lymphocytes, B cells and macrophages) were strongly and specifically detectable under an appropriate combination of mAb, AR method and signal amplification system. CD4 and CD8 required the most stringent conditions and could only be demonstrated in FD5 fixed sections. For detection of CD2, WC1+ T lymphocytes, B cells and macrophages, all the mAbs produced immunoreactivity in FD5 or formalin fixed tissues. The need to check a range of different AR methods is stressed, as the method of choice varied for each individual mAb. The incorporation of the signal amplification system was necessary to observe a strong signal and the complete distribution of CD4, CD8 and B cells. Fixation by FD5 proved to be better than formalin for the preservation of surface antigens but it was inferior for the detection of markers which were found to show cytoplasmic immunoreactivity, such as the macrophage marker MAC387 or the B cell markers BAQ155 or IL-A59.

Recent findings on the epidemiology and treatment of funguria are reviewed. Funguria, or candiduria, is a common nosocomial condition and may develop as early as the first two weeks of hospitalization. Risk factors include antibacterial therapy, an indwelling urinary catheter, urologic procedures, female sex, diabetes, and immunosuppressive therapy. Candida albicans is the species most commonly isolated from the urine of infected patients. Spontaneous resolution of funguria is relatively infrequent. Furthermore, although nonpharmacologic measures, such as removing unnecessary antibacterials and changing or removing indwelling urinary catheters, may be beneficial, they are often inadequate without additional, pharmacologic therapy. The most serious complication of untreated asymptomatic funguria is candidemia. Bladder irrigations with amphotericin B have been the standard of therapy for many years; recently, the optimal concentration and method of irrigation (continuous versus intermittent) have been debated. Studies indicate that intravesical amphotericin B and oral fluconazole therapy are each effective in clearing funguria. Intravesical amphotericin B appears to act more rapidly; however, the effect of systemic fluconazole therapy often persists longer than that of amphotericin B irrigation, and oral therapy is more convenient and less expensive. Oral fluconazole appears to have a more delayed but more lasting effect on funguria than amphotericin B bladder irrigation. Studies are needed to determine whether intravesical amphotericin B still has a role in the treatment of funguria and to refine strategies involving fluconazole.

We reviewed English-language clinical studies, abstracts, and review articles identified from MEDLINE searches from January 1966-August 1998, and bibliographies of identified articles to compare advanced-generation macrolides dirithromycin and clarithromycin and their use for respiratory tract infections. Both agents have superior adverse effect profiles compared with erythromycin, the original macrolide. Both have broad antibacterial coverage, but clarithromycin usually has a lower MIC90 to susceptible organisms than dirithromycin; for most isolates this difference is not clinically significant. Clarithromycin has better in vitro coverage of Haemophilus influenzae, but this activity varies with formation of its bioactive metabolite, 14-hydroxyclarithromycin. Neither agent is ideal for H. influenzae eradication. The agents differ markedly in terms of pharmacokinetics, pharmacodynamics, metabolism, and cost, and thus with respect to drug interaction profiles and dosages. Dirithromycin's drug interaction profile is markedly better than clarithromycin's. Clarithromycin is dosed twice/day; dirithromycin's pharmacokinetics allow once/day dosing. Dirithromycin is less expensive with regard to both cost/day and cost/treatment regimen. Clarithromycin has been studied and approved for administration to children. In adults with respiratory tract infections who are receiving drugs that would interact with clarithromycin, and in those with renal dysfunction with or without coexisting hepatic dysfunction, dirithromycin appears to be superior in terms of safety and equivalent to clarithromycin in terms of efficacy.

Background: Video-assisted thoracoscopic surgery (VATS) is now the generally preferred surgical treatment for spontaneous pneumothorax but is more difficult once pleural adhesions have developed. To test the hypothesis that VATS is under-used because of prolonged pleural intubation, we have audited the effect of preoperative management on subsequent surgical outcome., Method: Data are expressed as median (range). A prospective audit of clinical outcome in 42 consecutive patients (30 male, 12 female, aged 39 [19-81] years) referred to a Regional Unit for non-elective pneumothorax surgery. VATS was attempted whenever possible., Results: VATS was successful in 32 patients (group V) but 10 (24%) patients (group T) required thoracotomy and decortication of an empyema thoracis. Only seven (17%) patients were operated upon within 7 days of presentation, and 10 patients (24%) waited for more than 21 days. The delay from presentation to operation was significantly longer in group T (22 days vs. 10 days, P < 0.05, Wilcoxon). There were significantly more preoperative pleural interventions in patients in group T than in group V (P < 0.05, Wilcoxon). Postoperative stay was longer in group T (7 days vs. 3 days, P < 0.05) and there was a significant overall correlation between preoperative delay and postoperative stay (r = 0.64)., Conclusion: Delayed referral for pneumothorax surgery and multiple pleural interventions predispose to pleural sepsis and preclude VATS detrimentally affecting clinical outcome. Changes in referral practice are advocated.