The Pathway from Anatomy and Physiology to Diagnosis: A Developmental Perspective on Swallowing and Dysphagia.

Dysphagia results from diverse and distinct etiologies. The pathway from anatomy and physiology to clinical diagnosis is complex and hierarchical. Our approach in this paper is to show the linkages from the underlying anatomy and physiology to the clinical presentation. In particular, the terms performance, function, behavior, and physiology are often used interchangeably, which we argue is an obstacle to clear discussion of mechanism of pathophysiology. We use examples from pediatric populations to highlight the importance of understanding anatomy and physiology to inform clinical practice. We first discuss the importance of understanding anatomy in the context of physiology and performance. We then use preterm infants and swallow-breathe coordination as examples to explicate the hierarchical nature of physiology and its impact on performance. We also highlight where the holes in our knowledge lie, with the ultimate endpoint of providing a framework that could enhance our ability to design interventions to help patients. Clarifying these terms, and the roles they play in the biology of dysphagia will help both the researchers studying the problems as well as the clinicians applying the results of those studies.

Regional Variation in Contractile Patterns and Muscle Activity in Infant Pig Feeding.

At the level of the whole muscle, contractile patterns during activity are a critical and necessary source of variation in function. Understanding if a muscle is actively lengthening, shorting, or remaining isometric has implications for how it is working to power a given behavior. When feeding, the muscles associated with the tongue, jaws, pharynx, and hyoid act together to transport food through the oral cavity and into the esophagus. These muscles have highly coordinated firing patterns, yet also exhibit high levels of regional heterogeneity in both their timing of activity and their contractile characteristics when active. These high levels of variation make investigations into function challenging, especially in systems where muscles power multiple behaviors. We used infant pigs as a model system to systematically evaluate variation in muscle firing patterns in two muscles (mylohyoid and genioglossus) during two activities (sucking and swallowing). We also evaluated the contractile characteristics of mylohyoid during activity in the anterior and posterior regions of the muscle. We found that the posterior regions of both muscles had different patterns of activity during sucking versus swallowing, whereas the anterior regions of the muscles did not. Furthermore, the anterior portion of mylohyoid exhibited concentric contractions when active during sucking, whereas the posterior portion was isometric during sucking and swallowing. This difference suggests that the anterior portion of mylohyoid in infant pigs is functioning in concert with the tongue and jaws to generate suction, whereas the posterior portion is likely acting as a hyoid stabilizer during sucking and swallowing. Our results demonstrate the need to evaluate both the contractile characteristics and activity patterns of a muscle in order to understand its function, especially in cases where there is potential for variation in either factor within a single muscle.

The contractile patterns, anatomy and physiology of the hyoid musculature change longitudinally through infancy.

All mammalian infants suckle, a fundamentally different process than drinking in adults. Infant mammal oropharyngeal anatomy is also anteroposteriorly compressed and becomes more elongate postnatally. While suckling and drinking require different patterns of muscle use and kinematics, little insight exists into how the neuromotor and anatomical systems change through the time that infants suckle. We measured the orientation, activity and contractile patterns of five muscles active during infant feeding from early infancy until weaning using a pig model. Muscles not aligned with the long axis of the body became less mediolaterally orientated with age. However, the timing of activation and the contractile patterns of those muscles exhibited little change, although variation was larger in younger infants than older infants. At both ages, there were differences in contractile patterns within muscles active during both sucking and swallowing, as well as variation among muscles during swallowing. The changes in anatomy, coupled with less variation closer to weaning and little change in muscle firing and shortening patterns suggest that the neuromotor system may be optimized to transition to solid foods. The lesser consequences of aspiration during feeding on an all-liquid diet may not necessitate the evolution of variation in neuromotor function through infancy.

Preterm Birth Impacts the Timing and Excursion of Oropharyngeal Structures during Infant Feeding.

Swallowing in mammals requires the precise coordination of multiple oropharyngeal structures, including the palatopharyngeal arch. During a typical swallow, the activity of the palatopharyngeus muscle produces pharyngeal shortening to assist in producing pressure required to swallow and may initiate epiglottal flipping to protect the airway. Most research on the role of the palatopharyngeal arch in swallowing has used pharyngeal manometry, which measures the relative pressures in the oropharynx, but does not quantify the movements of the structures involved in swallowing. In this study, we assessed palatopharyngeal arch and soft palate function by comparing their movements in a healthy population to a pathophysiological population longitudinally through infancy (term versus preterm pigs). In doing so, we test the impact of birth status, postnatal maturation, and their interaction on swallowing. We tracked the three-dimensional (3D) movements of radiopaque beads implanted into relevant anatomical structures and recorded feeding via biplanar high-speed videofluoroscopy. We then calculated the total 3D excursion of the arch and soft palate, the orientation of arch movement, and the timing of maximal arch constriction during each swallow. Soft palate excursion was greater in term infants at both 7 and 17 days postnatal, whereas arch excursion was largely unaffected by birth status. Maximal arch constriction occurred much earlier in preterm pigs relative to term pigs, a result that was consistent across age. There was no effect of postnatal age on arch or soft palate excursion. Preterm and term infants differed in their orientation of arch movement, which most likely reflects both differences in anatomy and differences in feeding posture. Our results suggest that the timing and coordination of oropharyngeal movements may be more important to feeding performance than the movements of isolated structures, and that differences in the neural control of swallowing and its maturation in preterm and term infants may explain preterm swallowing deficits.

Modifiable healthcare factors affecting 28-day survival in bloodstream infection: a prospective cohort study.

BACKGROUND: Bloodstream infection is common in the UK and has significant mortality depending on the pathogen involved, site of infection and other patient factors. Healthcare staffing and ward activity may also impact on outcomes in a range of conditions, however there is little specific National Health Service (NHS) data on the impact for patients with bloodstream infection. Bloodstream Infections - Focus on Outcomes is a multicentre cohort study with the primary aim of identifying modifiable risk factors for 28-day mortality in patients with bloodstream infection due to one of six key pathogens. METHODS: Adults under the care of five NHS Trusts in England and Wales between November 2010 and May 2012 were included. Multivariable Cox regression was used to quantify the association between modifiable risk factors, including staffing levels and timing of appropriate therapy, and 28-day mortality, after adjusting for non-modifiable risk factors such as patient demographics and long-term comorbidities. RESULTS: A total of 1676 patients were included in the analysis population. Overall, 348/1676 (20.8%) died within 28 days. Modifiable factors associated with 28-day mortality were ward speciality, ward activity (admissions and discharges), movement within ward speciality, movement from critical care, and time to receipt of appropriate antimicrobial therapy in the first 7 days. For each additional admission or discharge per 10 beds, the hazard increased by 4% (95% CI 1 to 6%) in medical wards and 11% (95% CI 4 to 19%) in critical care. Patients who had moved wards within speciality or who had moved out of a critical care ward had a reduction in hazard of mortality. In the first 7 days, hazard of death increased with increasing time to receipt of appropriate antimicrobial therapy. CONCLUSION: This study underlines the importance of appropriate antimicrobials within the first 7 days, and the potential for ward activity and ward movements to impact on survival in bloodstream infection.

Oral antibiotics for infective endocarditis: a clinical review.

Current guidelines for management of infective endocarditis (IE) advise 4-6 weeks of IV antibiotics. This is based on historical data from animal models, which set a precedent for high peak serum antimicrobial levels, thought to be only achievable with IV therapy. However, there has been increasing recent interest in oral antibiotics as an alternative to prolonged parenteral therapy, not limited to treatment of IE. This review examines the theory behind parenteral antibiotic administration with reference to the MICs of relevant pathogens. By comparing published serum antimicrobial levels after oral and IV administration we suggest that safe levels of commonly used antibiotics can be achieved orally. We have then reviewed the literature to date on oral antibiotics for IE. The largest randomized controlled trial (RCT) in this area, the POET trial, concluded that oral therapy was non-inferior to prolonged IV therapy in stable patients with left-sided IE. Additionally, there have been two smaller RCTs published, as well as a number of observational studies over the last 50 years, utilizing a variety of different patient groups, methods and treatment strategies. This body of evidence gives weight to a potential shift in practice towards oral therapy, primarily as a step-down treatment. We conclude that pharmacological data offer theoretical reassurance for the safety of oral therapy. This is coupled with a growing evidence base for non-inferiority of oral antimicrobials compared with prolonged parenteral therapy in practice.

Impact of rapid microbial identification on clinical outcomes in bloodstream infection: the RAPIDO randomized trial.

OBJECTIVES: Bloodstream infection has a high mortality rate. It is not clear whether laboratory-based rapid identification of the organisms involved would improve outcome. METHODS: The RAPIDO trial was an open parallel-group multicentre randomized controlled trial. We tested all positive blood cultures from hospitalized adults by conventional methods of microbial identification and those from patients randomized (1:1) to rapid diagnosis in addition to matrix-assisted desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) performed directly on positive blood cultures. The only primary outcome was 28-day mortality. Clinical advice on patient management was provided to members of both groups by infection specialists. RESULTS: First positive blood culture samples from 8628 patients were randomized, 4312 into rapid diagnosis and 4136 into conventional diagnosis. After prespecified postrandomization exclusions, 2740 in the rapid diagnosis arm and 2810 in the conventional arm were included in the mortality analysis. There was no significant difference in 28-day survival (81.5% 2233/2740 rapid vs. 82.3% 2313/2810 conventional; hazard ratio 1.05, 95% confidence interval 0.93-1.19, p 0.42). Microbial identification was quicker in the rapid diagnosis group (median (interquartile range) 38.5 (26.7-50.3) hours after blood sampling vs. 50.3 (47.1-72.9) hours after blood sampling, p < 0.01), but times to effective antimicrobial therapy were no shorter (respectively median (interquartile range) 24 (2-78) hours vs. 13 (2-69) hours). There were no significant differences in 7-day mortality or total antibiotic consumption; times to resolution of fever, discharge from hospital or de-escalation of broad-spectrum therapy or 28-day Clostridioides difficile incidence. CONCLUSIONS: Rapid identification of bloodstream pathogens by MALDI-TOF MS in this trial did not reduce patient mortality despite delivering laboratory data to clinicians sooner.

In vitro effects of combined iron chelation, antibiotics and matrix disruption on clinical isolates of Pseudomonas aeruginosa.

OBJECTIVES: Pseudomonas aeruginosa is an important pathogen in chronic suppurative respiratory diseases, with adverse effects on severity, healthcare utilization and quality of life. Aerosolized combined biofilm disruption and iron chelators offer novel proof-of-concept for improving airway antimicrobial efficacy. Our aim was to assess the activity of desferrioxamine, Dornase alfa (DNase) and antibiotics on biofilm formation and against mature preformed biofilms of P. aeruginosa. METHODS: Fifty-six isolates of P. aeruginosa were screened for biofilm production and seven isolates with varying capacity to form biofilms were referred for further study. Three antibiotics (colistin, tobramycin and ciprofloxacin) as well as desferrioxamine and DNase were assessed for their ability to prevent biofilm formation using the crystal violet assay. The same method was used to assess their impact on mature biofilms. Each agent, as well as combinations of these agents, was also assessed for its effect on the metabolic activity and viability of preformed P. aeruginosa biofilm by the resazurin reduction assay and by performing viable counts. RESULTS: Antibiotics alone prevented the development of biofilms and partly reduced the viability of mature biofilms. Desferrioxamine and DNase did not reduce biofilm formation. For most isolates, desferrioxamine and DNase did not offer any clear advantage over the use of antibiotics alone with respect to reducing the viability of Pseudomonas biofilms. CONCLUSIONS: Colistin, tobramycin and ciprofloxacin prevented biofilm formation by P. aeruginosa and reduced the viability of mature biofilms. For most isolates, there was no clear advantage of combining these antimicrobials with desferrioxamine or DNase.

Outcomes of lung transplantation in adults with bronchiectasis.

BACKGROUND: Lung transplantation is a well-established treatment for end-stage non-cystic fibrosis bronchiectasis (BR), though information regarding outcomes of transplantation remains limited. Our results of lung transplantation for Br are reported here. METHODS: A retrospective review of case notes and transplantation databases was conducted for patients that had underwent lung transplantation for bronchiectasis at the Freeman Hospital between 1990 and 2013. RESULTS: Fourty two BR patients underwent lung transplantation, the majority (39) having bilateral sequential lung transplantation. Mean age at transplantation was 47.1 years. Pre-transplantation osteoporosis was a significant non-pulmonary morbidity (48%). Polymicrobial infection was common, with Pseudomonas aeruginosa infection frequently but not universally observed (67%). Forced expiratory volume in 1 second (% predicted) improved from a pre-transplantation mean of 0.71 L (22% predicted) to 2.56 L (79 % predicted) at 1-year post-transplantation. Our survival results were 74% at 1 year, 64% at 3 years, 61% at 5 years and 48% at 10 years. Sepsis was a common cause of early post-transplantation deaths. CONCLUSIONS: Lung transplantation for end-stage BR is a useful therapeutic option, with good survival and lung function outcomes. Survival values were similar to other bilateral lung transplants at our centre. Pre-transplantation Pseudomonas infection is common.

Whole-Genome Sequencing Reveals the Contribution of Long-Term Carriers in Staphylococcus aureus Outbreak Investigation.

Whole-genome sequencing (WGS) makes it possible to determine the relatedness of bacterial isolates at a high resolution, thereby helping to characterize outbreaks. However, for Staphylococcus aureus, the accumulation of within-host diversity during carriage might limit the interpretation of sequencing data. In this study, we hypothesized the converse, namely, that within-host diversity can in fact be exploited to reveal the involvement of long-term carriers (LTCs) in outbreaks. We analyzed WGS data from 20 historical outbreaks and applied phylogenetic methods to assess genetic relatedness and to estimate the time to most recent common ancestor (TMRCA). The findings were compared with the routine investigation results and epidemiological evidence. Outbreaks with epidemiological evidence for an LTC source had a mean estimated TMRCA (adjusted for outbreak duration) of 243 days (95% highest posterior density interval [HPD], 143 to 343 days) compared with 55 days (95% HPD, 28 to 81 days) for outbreaks lacking epidemiological evidence for an LTC (P = 0.004). A threshold of 156 days predicted LTC involvement with a sensitivity of 0.875 and a specificity of 1. We also found 6/20 outbreaks included isolates with differing antimicrobial susceptibility profiles; however, these had only modestly increased pairwise diversity (mean 17.5 single nucleotide variants [SNVs] [95% confidence interval {CI}, 17.3 to 17.8]) compared with isolates with identical antibiograms (12.7 SNVs [95% CI, 12.5 to 12.8]) (P < 0.0001). Additionally, for 2 outbreaks, WGS identified 1 or more isolates that were genetically distinct despite having the outbreak pulsed-field gel electrophoresis (PFGE) pulsotype. The duration-adjusted TMRCA allowed the involvement of LTCs in outbreaks to be identified and could be used to decide whether screening for long-term carriage (e.g., in health care workers) is warranted. Requiring identical antibiograms to trigger investigation could miss important contributors to outbreaks.

Successful outcome following pneumonectomy in a teenage boy with cystic fibrosis: a case report.

BACKGROUND: Cystic fibrosis lung disease is generally a diffuse process however rarely one lung may become particularly damaged through chronic collapse and consolidation resulting in end-stage bronchiectasis with relative sparing of the contralateral lung. This clinical situation is sometimes referred to as "destroyed lung". Lung resection surgery is seldom indicated in cystic fibrosis and the associated medical literature is relatively sparse. CASE PRESENTATION: A 14 year old boy was referred to our centre for lung transplantation assessment. He had a chronic history of complete collapse and consolidation of his entire right lung. This was causing severe morbidity in terms of a continuous requirement for intravenous antibiotics over the last year, poor exercise tolerance with forced expiratory volume in 1 s of 35-40% predicted and need for home tuition. He also had significant nutritional problems and gastrointestinal symptoms following a Nissen's fundoplication operation a year earlier. His nutritional status was firstly improved by the institution of jejunal feeding, which also greatly improved his distressing symptoms of nausea and wretching. After thorough multidisciplinary assessment the therapeutic option of performing a right pneumonectomy was considered due to relative sparing of the left lung, which demonstrated only mild bronchiectasis on computed tomography scan. This was performed uneventfully with a smooth peri-operative course. Targeted antimicrobials were used to treat the multiresistant organisms colonising his airways. Subsequently his quality of life, nutritional status and lung function all improved significantly and requirement for lung transplantation has been delayed. CONCLUSIONS: We report a successful outcome following pneumonectomy in a teenage boy with cystic fibrosis referred to our centre for lung transplantation assessment with chronic unilateral collapse and consolidation of his right lung. We believe that improvement of nutritional status pre-operatively and targeted antimicrobial therapy, all contributed to the smooth peri-operative course. Pneumonectomy can be a feasible option in this clinical situation in cystic fibrosis but the associated risks must be considered carefully on a case-by-case basis.

Application of a dense genetic map for assessment of genomic responses to selection and inbreeding in Heliothis virescens.

Adaptation of pest species to laboratory conditions and selection for resistance to toxins in the laboratory are expected to cause inbreeding and genetic bottlenecks that reduce genetic variation. Heliothis virescens, a major cotton pest, has been colonized in the laboratory many times, and a few laboratory colonies have been selected for Bacillus thuringiensis (Bt) resistance. We developed 350-bp double-digest restriction-site associated DNA-sequencing (ddRAD-seq) molecular markers to examine and compare changes in genetic variation associated with laboratory adaptation, artificial selection and inbreeding in this nonmodel insect species. We found that allelic and nucleotide diversity declined dramatically in laboratory-reared H. virescens as compared with field-collected populations. The declines were primarily a result of the loss of low frequency alleles present in field-collected H. virescens. A further, albeit modest decline in genetic diversity was observed in a Bt-selected population. The greatest decline was seen in H. virescens that were sib-mated for 10 generations, in which more than 80% of loci were fixed for a single allele. To determine which regions of the genome were resistant to fixation in our sib-mated line, we generated a dense intraspecific linkage map containing three PCR-based and 659 ddRAD-seq markers. Markers that retained polymorphism were observed in small clusters spread over multiple linkage groups, but this clustering was not statistically significant. Overall, we have confirmed and extended the general expectations for reduced genetic diversity in laboratory colonies, provided tools for further genomic analyses and produced highly homozygous genomic DNA for future whole genome sequencing of H. virescens.

One quantitative trait locus for intra- and interspecific variation in a sex pheromone.

Even though premating isolation is hypothesized to be a major driving force in speciation, its genetic basis is poorly known. In the noctuid moth Heliothis subflexa, one group of sex pheromone components, the acetates, emitted by the female, plays a crucial isolating role in preventing interspecific matings to males of the closely related Heliothis virescens, in which females do not produce acetates and males are repelled by them. We previously found intraspecific variation in acetates in H. subflexa: females in eastern North America contain significantly more acetates than females in Western Mexico. Here we describe the persistence of this intraspecific variation in laboratory-reared strains and the identification of one major quantitative trait locus (QTL), explaining 40% of the variance in acetate amounts. We homologized this intraspecific QTL to our previously identified interspecific QTL using restriction-associated DNA (RAD) tags. We found that a major intraspecific QTL overlaps with one of the two major interspecific QTL. To identify candidate genes underlying the acetate variation, we investigated a number of gene families with known or suspected acetyl- or acyltransferase activity. The most likely candidate genes did not map to our QTL, so that we currently hypothesize that a transcription factor underlies this QTL. Finding a single, large QTL that impacts variation in pheromone blends between and within species is, to our knowledge, the first such example for traits that have been demonstrated to affect premating isolation.

Comparison of two selective media for the recovery of Clostridium difficile from environmental surfaces.

Two culture media were compared for their ability to isolate Clostridium difficile from environmental sites within a UK hospital. The media were cefoxitin-cycloserine-egg yolk agar plus lysozyme (CCEY/L) and chromID C. difficile. A wide range of environmental surfaces was sampled using sterile sponges (Polywipes) and these were inoculated on to both media. C. difficile was recovered from 105 of 496 sites (21%) using a combination of both media. The sensitivity of chromID C. difficile was 87.6% compared with 26.6% for CCEY/L (P < 0.0001). chromID C. difficile performed significantly better than CCEY/L for the recovery of C. difficile from the environment.

Epidemiological survey of Clostridium difficile ribotypes in the North East of England during an 18-month period.

During an 18-month period, 1606 stool specimens from laboratory-confirmed cases of Clostridium difficile infection in the North East of England were ribotyped using unrestricted polymerase chain reaction. Of these, 87.6% grew C. difficile on culture; 70% had one of 10 recognizable ribotypes of which 001, 106 and 027 were the most prevalent. The proportions of ribotypes 002 and 015 declined during the study period, whereas ribotypes 016 and 023 increased. Ribotype 005 was significantly more numerous in males and ribotype 027 was associated with significantly higher mean age. Our findings differ from national data derived from more selective testing.

In vitro activity of S-(3,4-dichlorobenzyl)isothiourea hydrochloride and novel structurally related compounds against multidrug-resistant bacteria, including Pseudomonas aeruginosa and Burkholderia cepacia complex.

The aim of this study was to establish the antimicrobial activities of S-(3,4-dichlorobenzyl)isothiourea hydrochloride (A22) and a series of structurally related compounds against multidrug-resistant (MDR) bacteria. The minimum inhibitory concentrations (MICs) of 21 compounds were determined against 18 strains of pathogenic bacteria in addition to Pseudomonas aeruginosa (n=19) and Burkholderia cepacia complex (BCC) (n=20) isolated from the sputa of cystic fibrosis patients. Selected compounds were tested against further isolates, including P. aeruginosa (n=100), BCC (n=12) and Stenotrophomonas maltophilia (n=19). The interaction of S-(4-chlorobenzyl)isothiourea hydrochloride (C2) in combination with conventional antimicrobials was examined against 10 P. aeruginosa strains. Selected compounds were also tested against Enterobacteriaceae producing NDM-1 carbapenemase (n=64) and meticillin-resistant Staphylococcus aureus (MRSA) (n=37). Of the 21 compounds, 14 showed antimicrobial activity that was generally more pronounced against Gram-negative bacteria. Against P. aeruginosa, the most active compound was C2 [MIC for 50% of the organisms (MIC(50))=32µg/mL]. This compound was also the most active against BCC, with all isolates inhibited by 64µg/mL. For all ten strains of P. aeruginosa subjected to combination testing with C2 and conventional antimicrobials, a bactericidal effect was achieved with at least one combination. C2 and A22 both showed strong activity [MIC for 90% of the organisms (MIC(90))=4µg/mL] against Enterobacteriaceae that produced NDM-1 carbapenemase. Finally, S-(4-chlorobenzyl)-N-(2,4-dichlorophenyl)isothiourea hydrochloride showed good activity (MIC(90)=8µg/mL) against MRSA. This work establishes the activity of isothiourea derivatives against a broad range of clinically important MDR bacteria.

Guidelines for the diagnosis and antibiotic treatment of endocarditis in adults: a report of the Working Party of the British Society for Antimicrobial Chemotherapy.

The BSAC guidelines on treatment of infectious endocarditis (IE) were last published in 2004. The guidelines presented here have been updated and extended to reflect developments in diagnostics, new trial data and the availability of new antibiotics. The aim of these guidelines, which cover both native valve and prosthetic valve endocarditis, is to standardize the initial investigation and treatment of IE. An extensive review of the literature using a number of different search criteria has been carried out and cited publications used to support any changes we have made to the existing guidelines. Publications referring to in vitro or animal models have only been cited if appropriate clinical data are not available. Randomized, controlled trials suitable for the development of evidenced-based guidelines in this area are still lacking and therefore a consensus approach has again been adopted for most recommendations; however, we have attempted to grade the evidence, where possible. The guidelines have also been extended by the inclusion of sections on clinical diagnosis, echocardiography and surgery.

Assessing the impact of density dependence in field populations of Aedes aegypti.

Although many laboratory studies of intra-specific competition have been conducted with Ae. aegypti, there have been few studies in natural environments and none that examined density dependence in natural containers at normal field densities. Additionally, current mathematical models that predict Ae. aegypti population dynamics lack empirically-based functions for density-dependence. We performed field experiments in Tapachula, Mexico, where dengue is a significant public health concern. Twenty-one containers with natural food and water that already contained larvae were collected from local houses. Each container was divided in half and the naturally occurring larvae were apportioned in a manner that resulted in one side of the container (high density) having four times the density of the second side (low density). Larvae were counted and pupae were removed daily. Once adults emerged, wing span was measured to estimate body size. Density had a significant impact on larval survival, adult body size, and the time taken to transition from 4(th) instar to pupation. Increased density decreased larval survival by 20% and decreased wing length by an average of 0.19 mm. These results provide a starting point for a better understanding of density dependence in field populations of Ae. aegypti.