A metagenomic prospective cohort study on gut microbiome composition and clinical infection in small bowel transplantation

Two-thirds of small-bowel transplantation (SBT) recipients develop bacteremia, with the majority of infections occurring within 3 months post-transplant. Sepsis-related mortality occurs in 31% of patients and is commonly caused by bacteria of gut origin, which are thought to translocate across the implanted organ. Serial post-transplant surveillance endoscopies provide an opportunity to study whether the composition of the ileal and colonic microbiota can predict the emergence as well as the pathogen of subsequent clinical infections in the SBT patient population. Five participants serially underwent aspiration of ileal and colonic bowel effluents at transplantation and during follow-up endoscopy either until death or for up to 3 months post-SBT. We performed whole-metagenome sequencing (WMS) of 40 bowel effluent samples and compared the results with clinical infection episodes. Microbiome composition was concordant between participants and timepoint-matched ileal and colonic samples. Four out of five (4/5) participants had clinically significant infections thought to be of gut origin. Bacterial translocation from the gut was observed in 3/5 patients with bacterial infectious etiologies. In all three cases, the pathogens had demonstrably colonized the gut between 1-10 days prior to invasive clinical infection. Recipients with better outcomes received donor grafts with higher alpha diversity. There was an increase in the number of antimicrobial resistance genes associated with longer hospital stay for all participants. This metagenomic study provides preliminary evidence to support the pathogen translocation hypothesis of gut-origin sepsis in the SBT cohort. Ileal and colonic microbiome compositions were concordant; therefore, fecal metagenomic analysis could be a useful surveillance tool for impeding infection with specific gut-residing pathogens.

Gender equity of authorship in pulmonary medicine over the past decade

BACKGROUND

Gender disparity in authorship broadly persists in medical literature, little is known about female authorship within pulmonary medicine.

METHODS

A bibliometric analysis of publications from 2012 to 2021 in 12 journals with the highest impact in pulmonary medicine was conducted. Only original research and review articles were included. Names of the first and last authors were extracted and their genders were identified using the Gender-API web. Female authorship was described by overall distribution and distribution by country/region/continent and journal. We compared the article citations by gender combinations, evaluated the trend in female authorship, and forecasted when parity for first and last authorship would be reached. We also conducted a systematic review of female authorship in clinical medicine.

RESULTS

14,875 articles were included, and the overall percentage of female first authors was higher than last authors (37.0% vs 22.2%, p<0.001). Asia had the lowest percentage of female first (27.6%) and last (15.2%) authors. The percentages of female first and last authors increased slightly over time, except for a rapid increase in the COVID-19 pandemic periods. Parity was predicted in 2046 for the first authors and 2059 for the last authors. Articles with male authors were cited more than articles with female authors. However, male-male collaborations significantly decreased, whereas female-female collaborations significantly increased.

CONCLUSIONS

Despite the slow improvement in female authorship over the past decade, there is still a substantial gender disparity in female first and last authorship in high-impact medical journals in pulmonary medicine.

The rapid detection of respiratory pathogens in critically ill children

PURPOSE

Respiratory infections are the most common reason for admission to paediatric intensive care units (PICU). Most patients with lower respiratory tract infection (LRTI) receive broad-spectrum antimicrobials, despite low rates of bacterial culture confirmation. Here, we evaluated a molecular diagnostic test for LRTI to inform the better use of antimicrobials.

METHODS

The Rapid Assay for Sick Children with Acute Lung infection Study was a single-centre, prospective, observational cohort study of mechanically ventilated children (> 37/40 weeks corrected gestation to 18 years) with suspected community acquired or ventilator-associated LRTI. We evaluated the use of a 52-pathogen custom TaqMan Array Card (TAC) to identify pathogens in non-bronchoscopic bronchoalveolar lavage (mini-BAL) samples. TAC results were compared to routine microbiology testing. Primary study outcomes were sensitivity and specificity of TAC, and time to result.

RESULTS

We enrolled 100 patients, all of whom were tested with TAC and 91 of whom had matching culture samples. TAC had a sensitivity of 89.5% (95% confidence interval (CI₉₅) 66.9-98.7) and specificity of 97.9% (CI₉₅ 97.2-98.5) compared to routine bacterial and fungal culture. TAC took a median 25.8 h (IQR 9.1-29.8 h) from sample collection to result. Culture was significantly slower: median 110.4 h (IQR 85.2-141.6 h) for a positive result and median 69.4 h (IQR 52.8-78.6) for a negative result.

CONCLUSIONS

TAC is a reliable and rapid adjunct diagnostic approach for LRTI in critically ill children, with the potential to aid early rationalisation of antimicrobial therapy.

Development and implementation of a customised rapid syndromic diagnostic test for severe pneumonia

Background: The diagnosis of pneumonia has been hampered by a reliance on bacterial cultures which take several days to return a result, and are frequently negative. In critically ill patients this leads to the use of empiric, broad-spectrum antimicrobials and compromises good antimicrobial stewardship. The objective of this study was to establish the performance of a syndromic molecular diagnostic approach, using a custom TaqMan array card (TAC) covering 52 respiratory pathogens, and assess its impact on antimicrobial prescribing. Methods: The TAC was validated against a retrospective multi-centre cohort of broncho-alveolar lavage samples. The TAC was assessed prospectively in patients undergoing investigation for suspected pneumonia, with a comparator cohort formed of patients investigated when the TAC laboratory team were unavailable. Co-primary outcomes were sensitivity compared to conventional microbiology and, for the prospective study, time to result. Metagenomic sequencing was performed to validate findings in prospective samples. Antibiotic free days (AFD) were compared between the study cohort and comparator group. Results: 128 stored samples were tested, with sensitivity of 97% (95% confidence interval (CI) 88-100%). Prospectively, 95 patients were tested by TAC, with 71 forming the comparator group. TAC returned results 51 hours (interquartile range 41-69 hours) faster than culture and with sensitivity of 92% (95% CI 83-98%) compared to conventional microbiology. 94% of organisms identified by sequencing were detected by TAC. There was a significant difference in the distribution of AFDs with more AFDs in the TAC group (p=0.02). TAC group were more likely to experience antimicrobial de-escalation (odds ratio 2.9 (95%1.5-5.5)). Conclusions: Implementation of a syndromic molecular diagnostic approach to pneumonia led to faster results, with high sensitivity and impact on antibiotic prescribing.

Development and implementation of a customised rapid syndromic diagnostic test for severe pneumonia

Background: The diagnosis of pneumonia has been hampered by a reliance on bacterial cultures which take several days to return a result, and are frequently negative. In critically ill patients this leads to the use of empiric, broad-spectrum antimicrobials and compromises good antimicrobial stewardship. The objective of this study was to establish the performance of a syndromic molecular diagnostic approach, using a custom TaqMan array card (TAC) covering 52 respiratory pathogens, and assess its impact on antimicrobial prescribing. Methods: The TAC was validated against a retrospective multi-centre cohort of broncho-alveolar lavage samples. The TAC was assessed prospectively in patients undergoing investigation for suspected pneumonia, with a comparator cohort formed of patients investigated when the TAC laboratory team were unavailable. Co-primary outcomes were sensitivity compared to conventional microbiology and, for the prospective study, time to result. Metagenomic sequencing was performed to validate findings in prospective samples. Antibiotic free days (AFD) were compared between the study cohort and comparator group. Results: 128 stored samples were tested, with sensitivity of 97% (95% confidence interval (CI) 88-100%). Prospectively, 95 patients were tested by TAC, with 71 forming the comparator group. TAC returned results 51 hours (interquartile range 41-69 hours) faster than culture and with sensitivity of 92% (95% CI 83-98%) compared to conventional microbiology. 94% of organisms identified by sequencing were detected by TAC. There was a significant difference in the distribution of AFDs with more AFDs in the TAC group (p=0.02). TAC group were more likely to experience antimicrobial de-escalation (odds ratio 2.9 (95%1.5-5.5)). Conclusions: Implementation of a syndromic molecular diagnostic approach to pneumonia led to faster results, with high sensitivity and impact on antibiotic prescribing.

Development and implementation of a customised rapid syndromic diagnostic test for severe pneumonia

Background: The diagnosis of pneumonia has been hampered by a reliance on bacterial cultures which take several days to return a result, and are frequently negative. In critically ill patients this leads to the use of empiric, broad-spectrum antimicrobials and compromises good antimicrobial stewardship. The objective of this study was to establish the performance of a syndromic molecular diagnostic approach, using a custom TaqMan array card (TAC) covering 52 respiratory pathogens, and assess its impact on antimicrobial prescribing. Methods: The TAC was validated against a retrospective multi-centre cohort of broncho-alveolar lavage samples. The TAC was assessed prospectively in patients undergoing investigation for suspected pneumonia, with a comparator cohort formed of patients investigated when the TAC laboratory team were unavailable. Co-primary outcomes were sensitivity compared to conventional microbiology and, for the prospective study, time to result. Metagenomic sequencing was performed to validate findings in prospective samples. Antibiotic free days (AFD) were compared between the study cohort and comparator group. Results: 128 stored samples were tested, with sensitivity of 97% (95% confidence interval (CI) 88-100%). Prospectively, 95 patients were tested by TAC, with 71 forming the comparator group. TAC returned results 51 hours (interquartile range 41-69 hours) faster than culture and with sensitivity of 92% (95% CI 83-98%) compared to conventional microbiology. 94% of organisms identified by sequencing were detected by TAC. There was a significant difference in the distribution of AFDs with more AFDs in the TAC group (p=0.02). TAC group were more likely to experience antimicrobial de-escalation (odds ratio 2.9 (95%1.5-5.5)). Conclusions: Implementation of a syndromic molecular diagnostic approach to pneumonia led to faster results, with high sensitivity and impact on antibiotic prescribing.

Phenotypic whole-cell screening identifies a protective carbohydrate epitope on Klebsiella pneumoniae

The increasing global occurrence of recalcitrant multi-drug resistant Klebsiella pneumoniae infections warrants the investigation of alternative therapy options, such as the use of monoclonal antibodies (mAbs). We used a target-agnostic phage display approach to K. pneumoniae bacteria lacking bulky, highly variable surface polysaccharides in order to isolate antibodies targeting conserved epitopes among clinically relevant strains. One antibody population contained a high proportion of unique carbohydrate binders, and biolayer interferometry revealed these antibodies bound to lipopolysaccharide (LPS). Antibodies that bound to O1 and O1/O2 LPS were identified. Antibodies were found to promote opsonophagocytic killing by human monocyte-derived macrophages and clearance of macrophage-associated bacteria when assessed using high-content imaging. One antibody, B39, was found to protect mice in a lethal model of K. pneumoniae pneumonia against both O1 and O2 strains when dosed therapeutically. High-content imaging, western blotting and fluorescence-activated cell sorting were used to determine binding to a collection of clinical K. pneumoniae O1 and O2 strains. The data suggests B39 binds to D-galactan-I and D-galactan-II of the LPS of O1 and O2 strains. Thus, we have discovered an mAb with novel binding and functional activity properties that is a promising candidate for development as a novel biotherapeutic for the treatment and prevention of K. pneumoniae infections.

An age-stratified serosurvey against purified Salmonella enterica serovar Typhi antigens in the Lao People´s Democratic Republic

The epidemiology of typhoid fever in Lao People`s Democratic Republic is poorly defined. Estimating the burden of typhoid fever in endemic countries is complex due to the cost and limitations of population-based surveillance; serological approaches may be a more cost-effective alternative. ELISAs were performed on 937 serum samples (317 children and 620 adults) from across Lao PDR to measure IgG antibody titers against Vi polysaccharide and the experimental protein antigens, CdtB and HlyE. We measured the significance of the differences between antibody titers in adults and children and fitted models to assess the relationship between age and antibody titers. The median IgG titres of both anti-HylE and CdtB were significantly higher in children compared to adults (anti-HylE; 351.7 ELISA Units (EU) vs 198.1 EU, respectively; p<0.0001 and anti-CdtB; 52.6 vs 12.9 EU; p<0.0001). Conversely, the median anti-Vi IgG titer was significantly higher in adults than children (11.3 vs 3.0 U/ml; p<0.0001). A non-linear trend line fitted to the anti-CdtB and anti-HlyE IgG data identified a peak in antibody concentration in children <5 years of age. We identified elevated titers of anti-HlyE and anti-CdtB IgG in the serum of children residing in Lao PDR in comparison to adults. These antigens are associated with seroconversion after typhoid fever and may be a superior measure of disease burden than anti-Vi IgG. This approach is scalable and may be developed to assess the burden of typhoid fever in countries where the disease may be endemic, and evidence is required for the introduction of typhoid vaccines.

Typhoid fever is a serious bloodstream infection caused by the bacterium Salmonella Typhi. Estimating the burden of typhoid fever is complex due to the limitations, cost, and scalability of current diagnostic surveillance methods. The detection of specific antibody responses against the organism may be a more sustainable manner of measuring exposure and disease burden in endemic location. We measured antibody (IgG) in 937 serum samples (317 children and 620 adults) from across the Lao People`s Democratic Republic against a polysaccharide (Vi) and two experimental protein antigens, CdtB and HlyE, that may more appropriate markers of disease exposure. We measured the significance of the differences between antibody titers in adults and children and fitted models to assess the relationship between age and antibody titers. The median IgG titres against HylE and CdtB were significantly higher in children than adults. Conversely, the median IgG titres against Vi was significantly higher in adults than children. We identified a significant association between a peak in IgG titres against CdtB and HlyE in children aged under 5 years. These data are indicative of high level of typhoid fever exposure in children under 5 years of age in Lao PDR and we surmise that IgG titres against HylE and CdtB may be a superior measure of typhoid disease burden than IgG titres against Vi. Our approach is scalable and can be further validated to assess the burden of typhoid fever in countries where the disease may be endemic, and evidence is required for the introduction of typhoid vaccines.

Rapid Assay for Sick Children with Acute Lung infection Study (RASCALS): diagnostic cohort study protocol

INTRODUCTION

Lower respiratory tract infection (LRTI) is the most commonly treated infection in critically ill children. Pathogens are infrequently identified on routine respiratory culture, and this is a time-consuming process. A syndromic approach to rapid molecular testing that includes a wide range of bacterial and fungal targets has the potential to aid clinical decision making and reduce unnecessary broad spectrum antimicrobial prescribing. Here, we describe a single-centre prospective cohort study investigating the use of a 52-pathogen TaqMan array card (TAC) for LRTI in the paediatric intensive care unit (PICU).

METHODS AND ANALYSIS

Critically ill children with suspected LRTI will be enrolled to this 100 patient single-centre prospective observational study in a PICU in the East of England. Samples will be obtained via routine non-bronchoscopic bronchoalveolar lavage which will be sent for standard microbiology culture in addition to TAC. A blood draw will be obtained via any existing vascular access device. The primary outcomes of the study will be (1) concordance of TAC result with routine culture and 16S rRNA gene sequencing and (2) time of diagnostic result from TAC versus routine culture. Secondary outcomes will include impact of the test on total antimicrobial prescriptions, a description of the inflammatory profile of the lung and blood in response to pneumonia and a description of the clinical experience of medical and nursing staff using TAC.

ETHICS AND DISSEMINATION

This study has been approved by the Yorkshire and the Humber-Bradford Leeds Research Ethics Committee (REC reference 20/YH/0089). Informed consent will be obtained from all participants. Results will be published in peer-reviewed publications and international conferences.

TRIAL REGISTRATION NUMBER

NCT04233268.

Ventilator-associated pneumonia in critically ill patients with COVID-19

BACKGROUND

Pandemic COVID-19 caused by the coronavirus SARS-CoV-2 has a high incidence of patients with severe acute respiratory syndrome (SARS). Many of these patients require admission to an intensive care unit (ICU) for invasive ventilation and are at significant risk of developing a secondary, ventilator-associated pneumonia (VAP).

OBJECTIVES

To study the incidence of VAP and bacterial lung microbiome composition of ventilated COVID-19 and non-COVID-19 patients.

METHODS

In this retrospective observational study, we compared the incidence of VAP and secondary infections using a combination of microbial culture and a TaqMan multi-pathogen array. In addition, we determined the lung microbiome composition using 16S RNA analysis in a subset of samples. The study involved 81 COVID-19 and 144 non-COVID-19 patients receiving invasive ventilation in a single University teaching hospital between March 15th 2020 and August 30th 2020.

RESULTS

COVID-19 patients were significantly more likely to develop VAP than patients without COVID (Cox proportional hazard ratio 2.01 95% CI 1.14-3.54, p = 0.0015) with an incidence density of 28/1000 ventilator days versus 13/1000 for patients without COVID (p = 0.009). Although the distribution of organisms causing VAP was similar between the two groups, and the pulmonary microbiome was similar, we identified 3 cases of invasive aspergillosis amongst the patients with COVID-19 but none in the non-COVID-19 cohort. Herpesvirade activation was also numerically more frequent amongst patients with COVID-19.

CONCLUSION

COVID-19 is associated with an increased risk of VAP, which is not fully explained by the prolonged duration of ventilation. The pulmonary dysbiosis caused by COVID-19, and the causative organisms of secondary pneumonia observed are similar to that seen in critically ill patients ventilated for other reasons.

Identification of Natural Mutations Responsible for Altered Infection Phenotypes of Salmonella enterica Clinical Isolates by Using Cell Line Infection Screens

The initial steps of Salmonella pathogenesis involve adhesion to and invasion into host epithelial cells. While well-studied for Salmonella enterica serovar Typhimurium, the factors contributing to this process in other, host-adapted serovars remains unexplored. Here, we screened clinical isolates of serovars Gallinarum, Dublin, Choleraesuis, Typhimurium, and Enteritidis for adhesion to and invasion into intestinal epithelial cell lines of human, porcine, and chicken origins. Thirty isolates with altered infectivity were used for genomic analyses, and 14 genes and novel mutations associated with high or low infectivity were identified. The functions of candidate genes included virulence gene expression regulation and cell wall or membrane synthesis and components. The role of several of these genes in Salmonella adhesion to and invasion into cells has not previously been investigated. The genes dksA (encoding a stringent response regulator) and sanA (encoding a vancomycin high-temperature exclusion protein) were selected for further analyses, and we confirmed their roles in adhesion to and invasion into host cells. Furthermore, transcriptomic analyses were performed for S Enteritidis and S Typhimurium, with two highly infective and two marginally infective isolates for each serovar. Expression profiles for the isolates with altered infection phenotypes revealed the importance of type 3 secretion system expression levels in the determination of an isolate's infection phenotype. Taken together, these data indicate a new role in cell host infection for genes or gene variants previously not associated with adhesion to and invasion into the epithelial cells.IMPORTANCESalmonella is a foodborne pathogen affecting over 200 million people and resulting in over 200,000 fatal cases per year. Its adhesion to and invasion into intestinal epithelial cells represent one of the first and key steps in the pathogenesis of salmonellosis. Still, around 35 to 40% of bacterial genes have no experimentally validated function, and their contribution to bacterial virulence, including adhesion and invasion, remains largely unknown. Therefore, the significance of this study is in the identification of new genes or gene allelic variants previously not associated with adhesion and invasion. It is well established that blocking adhesion and/or invasion would stop or hamper bacterial infection; therefore, the new findings from this study could be used in future developments of anti-Salmonella therapy targeting genes involved in these key processes. Such treatment could be a valuable alternative, as the prevalence of antibiotic-resistant bacteria is increasing very rapidly.

Pathogenic Escherichia coli Possess Elevated Growth Rates under Exposure to Sub-Inhibitory Concentrations of Azithromycin

Antimicrobial resistance (AMR) has been identified by the World Health Organization (WHO) as one of the ten major threats to global health. Advances in technology, including whole-genome sequencing, have provided new insights into the origin and mechanisms of AMR. However, our understanding of the short-term impact of antimicrobial pressure and resistance on the physiology of bacterial populations is limited. We aimed to investigate morphological and physiological responses of clinical isolates of E. coli under short-term exposure to key antimicrobials. We performed whole-genome sequencing on twenty-seven E. coli isolates isolated from children with sepsis to evaluate their AMR gene content. We assessed their antimicrobial susceptibility profile and measured their growth dynamics and morphological characteristics under exposure to varying concentrations of ciprofloxacin, ceftriaxone, tetracycline, gentamicin, and azithromycin. AMR was common, with all organisms resistant to at least one antimicrobial; a total of 81.5% were multi-drug-resistant (MDR). We observed an association between resistance profile and morphological characteristics of the E. coli over a three-hour exposure to antimicrobials. Growth dynamics experiments demonstrated that resistance to tetracycline promoted the growth of E. coli under antimicrobial-free conditions, while resistance to the other antimicrobials incurred a fitness cost. Notably, antimicrobial exposure heterogeneously suppressed bacterial growth, but sub-MIC concentrations of azithromycin increased the maximum growth rate of the clinical isolates. Our results outline complex interactions between organism and antimicrobials and raise clinical concerns regarding exposure of sub-MIC concentrations of specific antimicrobials.

A blueprint for the implementation of a validated approach for the detection of SARS-Cov2 in clinical samples in academic facilities

The COVID-19 pandemic is expanding at an unprecedented rate. As a result, diagnostic services are stretched to their limit, and there is a clear need for the provision of additional diagnostic capacity. Academic laboratories, many of which are closed due to governmental lockdowns, may be in a position to support local screening capacity by adapting their current laboratory practices. Here, we describe the process of developing a SARS-Cov2 diagnostic workflow in a conventional academic Containment Level 2 laboratory. Our outline includes simple SARS-Cov2 deactivation upon contact, the method for a quantitative real-time reverse transcriptase PCR detecting SARS-Cov2, a description of process establishment and validation, and some considerations for establishing a similar workflow elsewhere. This was achieved under challenging circumstances through the collaborative efforts of scientists, clinical staff, and diagnostic staff to mitigate to the ongoing crisis. Within 14 days, we created a validated COVID-19 diagnostics service for healthcare workers in our local hospital. The described methods are not exhaustive, but we hope may offer support to other academic groups aiming to set up something comparable in a short time frame.

A novel therapeutic antibody screening method using bacterial high-content imaging reveals functional antibody binding phenotypes of Escherichia coli ST131

The increase of antimicrobial resistance (AMR), and lack of new classes of licensed antimicrobials, have made alternative treatment options for AMR pathogens increasingly attractive. Recent studies have demonstrated anti-bacterial efficacy of a humanised monoclonal antibody (mAb) targeting the O25b O-antigen of Escherichia coli ST131. To evaluate the phenotypic effects of antibody binding to diverse clinical E. coli ST131 O25b bacterial isolates in high-throughput, we designed a novel mAb screening method using high-content imaging (HCI) and image-based morphological profiling to screen a mAb targeting the O25b O-antigen. Screening the antibody against a panel of 86 clinical E. coli ST131 O25:H4 isolates revealed 4 binding phenotypes: no binding (18.60%), weak binding (4.65%), strong binding (69.77%) and strong agglutinating binding (6.98%). Impaired antibody binding could be explained by the presence of insertion sequences or mutations in O-antigen or lipopolysaccharide core biosynthesis genes, affecting the amount, structure or chain length of the O-antigen. The agglutinating binding phenotype was linked with lower O-antigen density, enhanced antibody-mediated phagocytosis and increased serum susceptibly. This study highlights the need to screen candidate mAbs against large panels of clinically relevant isolates, and that HCI can be used to evaluate mAb binding affinity and potential functional efficacy against AMR bacteria.

A blueprint for the implementation of a validated approach for the detection of SARS-Cov2 in clinical samples in academic facilities

The COVID-19 pandemic is expanding at an unprecedented rate. As a result, diagnostic services are stretched to their limit, and there is a clear need for the provision of additional diagnostic capacity. Academic laboratories, many of which are closed due to governmental lockdowns, may be in a position to support local screening capacity by adapting their current laboratory practices. Here, we describe the process of developing a SARS-Cov2 diagnostic workflow in a conventional academic Containment Level 2 laboratory. Our outline includes simple SARS-Cov2 deactivation upon contact, the method for a quantitative real-time reverse transcriptase PCR detecting SARS-Cov2, a description of process establishment and validation, and some considerations for establishing a similar workflow elsewhere. This was achieved under challenging circumstances through the collaborative efforts of scientists, clinical staff, and diagnostic staff to mitigate to the ongoing crisis. Within 14 days, we created a validated COVID-19 diagnostics service for healthcare workers in our local hospital. The described methods are not exhaustive, but we hope may offer support to other academic groups aiming to set up something comparable in a short time frame.

Resistance mechanisms and population structure of highly drug resistant Klebsiella in Pakistan during the introduction of the carbapenemase NDM-1

Klebsiella pneumoniae is a major threat to public health with the emergence of isolates resistant to most, if not all, useful antibiotics. We present an in-depth analysis of 178 extended-spectrum beta-lactamase (ESBL)-producing K. pneumoniae collected from patients resident in a region of Pakistan, during the period 2010–2012, when the now globally-distributed carbapenemase bla-NDM-1 was being acquired by Klebsiella. We observed two dominant lineages, but neither the overall resistance profile nor virulence-associated factors, explain their evolutionary success. Phenotypic analysis of resistance shows few differences between the acquisition of resistance genes and the phenotypic resistance profile, including beta-lactam antibiotics that were used to treat ESBL-positive strains. Resistance against these drugs could be explained by inhibitor-resistant beta-lactamase enzymes, carbapenemases or ampC type beta-lactamases, at least one of which was detected in most, but not all relevant strains analysed. Complete genomes for six selected strains are reported, these provide detailed insights into the mobile elements present in these isolates during the initial spread of NDM-1. The unexplained success of some lineages within this pool of highly resistant strains, and the discontinuity between phenotypic resistance and genotype at the macro level, indicate that intrinsic mechanisms contribute to competitive advantage and/or resistance.

Identification of 11 polymorphic simple sequence repeat loci in the phytopathogenic fungus Fusarium pseudograminearum as a tool for genetic studies

Simple sequence repeat (SSR) markers for Fusarium pseudograminearum with 2 to 3 bp repeat motifs were identified by screening the genome database of the related species Fusarium graminearum. Twelve SSRs amplified single loci in both F. graminearum and F. pseudograminearum. Forty F. pseudograminearum and six F. graminearum individual isolates were screened to determine levels of polymorphism, with all SSRs displaying three to 14 alleles across all isolates. Eleven SSRs were polymorphic across F. pseudograminearum isolates tested proving the usefulness of genome databases of closely related species in identifying genetic markers.

First Report of a 16SrII-D Subgroup Phytoplasma Associated with Pale Purple Coneflower Witches'-Broom Disease in Australia

Pale purple coneflower, Echinacea pallida (Nutt.) Nutt., is an herbaceous perennial cultivated for its ornamental and medicinal properties. In 2005, phytoplasma-like symptoms, including virescence, phyllody, and chlorotic leaves, were first observed in coneflower fields in northern Tasmania, Australia. During the 2010-2011 growing season, the incidence of affected plants was estimated to be 12% within a single field. Total DNA was extracted from symptomatic plants with a DNeasy Plant Mini Kit (QIAGEN Inc., Valencia, CA) according to the manufacturer's instructions. DNA was also extracted, as described above, from asymptomatic coneflower seedlings obtained by germinating surface-sterilized seed on water agar. DNA was amplified via a nested PCR using universal primer pairs P1/P7 followed by R16F2n/R16R2 to detect putative phytoplasmas (2). Amplifications yielded expected products of 1.8 and 1.2 kb, respectively, only from symptomatic samples. Subsequently, PCR products from six arbitrarily selected samples were used for sequencing (Genome Lab Dye Terminator Cycling Sequence with Quick Start Chemistry) and read in a CEQ8000 sequencer (Beckman Coulter Inc., Brea, CA). Sequence homology indicated 100% similarity between isolates designated EWB1 to EWB4 (GenBank Accession Nos. JF340075 and JF340077 to JF340079) and between EWB5 and EWB6 (JF340076 and JF40080). Sequence homology between the two observed groups was 99.7%, resulting from a 4-bp difference in the R16F2n primer region. Blast search revealed isolates EWB1 to EWB4 were 100% homologous with Catharanthus roseus phytoplasma (EU096500.1), Tomato big bud phytoplasma (EF193359.1), Scaevola witches'-broom phytoplasma (AB257291.1), and Mollicutes sp. (Y10097.1 and Y10096.1). Moreover, isolates EWB5 and EWB6 shared 99% sequence identity with the above isolates. iPhyClassifier (4) was used to perform sequence similarity and generate virtual restriction fragment length polymorphism (RFLP) profiles. The 16S rDNA sequence of isolates EWB1 to EWB4 and EWB5 to EWB6 shared 100 and 99.7% similarity, respectively, to the 'Candidatus Phytoplasma australasiae' reference strain (Y10097). RFLP profiles from all isolates suggested that they belonged to the 16SrII-D subgroup. To our knowledge, this is the first report of a 16SrII-D subgroup phytoplasma infecting E. pallida in Australia. Aster yellow phytoplasmas (16SrI-C subgroup) infections of E. purpurea have been recorded in Slovenia (3) and southern Bohemia (1). References: (1) J. Franova et al. Eur. J. Plant Pathol. 123:85, 2009. (2) I. M. Lee et al. Int. J. Syst. Bacteriol. 48:1153, 1998. (3) S. Radišek et al. Plant Pathol. 58:392, 2009. (4) Y. Zhao et al. Int. J. Syst. Evol. Microbiol. 59:2582, 2009.

A laboratory and clinical evaluation of single-use instruments for tonsil and adenoid surgery

OBJECTIVES

To compare the quality and consistency of single-use adenotonsillectomy instruments available in the UK with reusable instruments and examine their performance in a clinical setting.

DESIGN

A laboratory assessment of each reusable instrument created a detailed specification for the respective single-use equivalent. A surveillance system monitored the performance of a selected set of specified single-use instruments.

SETTING

Single-use instruments were withdrawn shortly after their introduction in 2001. Persisting concerns from the Spongiform Encephalopathy Advisory Committee led to an investigation into the feasibility of continuing to use such instruments.

MAIN OUTCOME MEASURES

The numbers of instruments from each set judged as unacceptable or as good as the original. The number and cause of instrument failure during clinical surveillance.

RESULTS

Between 40% and 93% of the instruments on each set were as good as the original and between 0% and 40% of the instruments were unacceptable from six sets of steel and one set of polymer instruments. 4151 procedures were monitored between 1 February 2003 and 31 March 2004 using a total of 41 376 instruments. Problems were reported with 335 (0.8%) instruments, 46% attributable to instrument design, 14% to poor design control and 13% to instruments escaping quality control systems. Following correction of the faults, between 1 January 2004 and 31 March 2004 the problem rate fell to 0.4%.

CONCLUSIONS

High quality single-use instruments for tonsil and adenoid surgery are available in the UK. Some companies offered inferior instruments not fit for their purpose. The procurement, introduction and subsequent clinical approval of single-use instruments requires a radically different approach to that currently applied to the purchase of reusable surgical equipment. Careful monitoring of their introduction is essential.

Spatiotemporal analysis of epiphytotics of downy mildew of oilseed poppy in tasmania, australia

Downy mildew, caused by Peronospora arborescens, has become the major disease affecting oilseed poppy (Papaver somniferum) since its first record in Tasmania in 1996. Two field trials conducted in 2000 and 2001 studied the progression and spatial distribution of downy mildew epiphytotics. The logistic and exponential models best described the progression of disease incidence and severity, respectively. Incidence and severity increased rapidly following canopy closure. In 2001, incidence increased from 0.16%, prior to canopy closure, to 100% at late flowering (40 days). Spatial analyses of epiphytotics were conducted by fitting the beta-binomial and binomial distributions, median runs analysis, and the spatial analysis by distance indices. All analyses demonstrated that the distribution of incidence and severity was strongly spatially aggregated from canopy closure until at least late flowering. These results suggest that secondary spread from a few primary infections is the major factor in epiphytotics.

Surgical treatment and long-term outcome of ferrets with bilateral adrenal tumors or adrenal hyperplasia: 56 cases (1994-1997)

OBJECTIVE

To determine signalment, clinical signs, concurrent diseases, response to surgical treatment, and long-term outcome of ferrets with bilateral adrenal tumors or adrenal hyperplasia.

DESIGN

Retrospective study.

ANIMALS

56 ferrets with bilateral adrenal tumors or adrenal hyperplasia confirmed histologically following subtotal bilateral adrenalectomy.

PROCEDURE

Medical records of all ferrets with bilateral adrenal tumors or hyperplasia examined between 1994 and 1997 were reviewed. Ferrets underwent a subtotal bilateral adrenalectomy or a unilateral adrenalectomy initially, followed by a unilateral subtotal adrenalectomy when tumors or hyperplasia later developed on the contralateral adrenal gland. A long-term follow-up of a minimum of 18 months after final adrenal gland surgery was obtained by examination of medical records and follow-up telephone conversations.

RESULTS

Clinical signs of hyperadrenocorticism included bilaterally symmetric alopecia, return to male sexual behavior in castrated male ferrets, or swollen vulva in spayed female ferrets. Surgical treatment of bilateral adrenal disease by subtotal bilateral adrenalectomy (or unilateral adrenalectomy followed by contralateral unilateral subtotal adrenalectomy) was effective with a mortality rate of < 2%. Only 3 (5%) ferrets required glucocorticoid or mineralocorticoid replacement following subtotal bilateral adrenalectomy. Recurrence after bilateral adrenalectomy was 15% with a mean long-term follow-up period of 30 months.

CONCLUSIONS AND CLINICAL RELEVANCE

Bilaterally symmetric alopecia, return to male sexual behavior in castrated male ferrets, or swollen vulva in spayed female ferrets are indicative of adrenal tumors or adrenal hyperplasia in ferrets. Surgical treatment of bilateral adrenal disease by subtotal bilateral adrenalectomy is effective, with a low rate of complications and postoperative recurrence rate.

Improved efficacy of calculus removal in furcations using ultrasonic diamond-coated inserts

Dentsply Cavitron Diamond Inserts provide improved efficacy in removing calculus from furcations. A total of 60 extracted human mandibular molar teeth had artificial calculus applied to the furcations, then were randomly treated with either sharp universal Gracey curettes (HAND), a plain ultrasonic TFI-10 tip in a cavitron instrument (CAV), or one of 2 diamond-coated cavitron instruments (TFI-10 fine-grit (FIN) and TFI-10 medium-grit (MED)) When the time needed to completely clean the furcations was evaluated, MED was the fastest, followed by FIN, CAV, and HAND, respectively. All of the powered instruments were faster than hand curettes with regard to effective in vitro calculus removal in furcations. The use of these types of instruments would reduce the time required to perform periodontal surgery and might improve regenerative therapy.

Multi-center clinical evaluation of combination anorganic bovine-derived hydroxyapatite matrix (ABM)/cell binding peptide (P-15) as a bone replacement graft material in human periodontal osseous defects. 6-month results

A synthetic cell-binding peptide (P-15) combined with anorganic bovine-derived hydroxyapatite bone matrix (ABM) was compared to demineralized freeze-dried bone allograft (DFDBA) and open flap debridement (DEBR) in human periodontal osseous defects in a controlled, monitored, multi-center trial. Following appropriate initial preparation procedures, flap surgery with defect and root debridement was performed. Three osseous defects per patient were treated randomly with one of three procedures after surgical preparation. Appropriate periodontal maintenance schedules were followed, and at 6 to 7 months re-entry flap surgery was performed for documentation and finalization of treatment. Analysis of variation (ANOVA) and t test analyses of patient mean values from 31 patients revealed that the combination ABM/P-15 grafts demonstrated significantly better mean defect fill of 2.8 +/- 1.2 mm (72.3%) versus a mean defect fill of 2.0 +/- 1.4 mm (51.4%) for defects treated with DFDBA (P <0.05) and a mean defect fill of 1.5 +/- 1.3 mm (40.3%) (P <0.05) for defects treated with DEBR. Other hard tissue findings showed similar clinically superior results with the use of ABM/P-15. Relative defect fill results showed 87% positive (50% to 100% defect fill) responses with ABM/P-15, 58% positive responses with DFDBA, and 41% positive responses with DEBR. There were 8 to 9 times more failures (minimal response) with DFDBA and DEBR (26% to 29% frequency) than with ABM/P-15. Soft tissue findings showed no significant differences among treatments except for greater clinical attachment level gain with ABM/P-15 compared to DEBR. These results suggest that the use of the P-15 synthetic cell-binding peptide combined with ABM yields better clinical results than either DFDBA or DEBR. Further studies are needed to determine the relative roles of the ABM and/or the P-15 in these improved results.

Clinical evaluation of the speed and effectiveness of subgingival calculus removal on single-rooted teeth with diamond-coated ultrasonic tips

Several studies have found incomplete calculus removal during periodontal treatment with traditional hand curets, sonic, and ultrasonic instruments. This study evaluated the speed and effectiveness of subgingival calculus removal with new diamond-coated ultrasonic tips on single-rooted teeth. Single session subgingival scaling and root planing was performed on 80 teeth with 5 to 12 mm probing depths in 15 patients. Each patient provided groups of 4 teeth that were randomly treated with either hand curets (HAND); standard smooth ultrasonic tip (US); or fine grit (FINDIAM) or medium grit (MEDDIAM) diamond-coated ultrasonic tips. The time taken to reach the therapeutic endpoint of a clean, smooth root surface in a defined region on each tooth with each instrument by the 3 therapists with differing experience levels was recorded. The teeth were then atraumatically extracted, stored in a surfactant, photographed at 10X, and the percent of calculus present in the area of the pocket or on a comparable control surface calculated by histometric point counting. ANOVA and paired t tests showed that mean percent remaining calculus on treated versus control surfaces was HAND 4.6 +/- 5.3 versus 57.5 +/- 28.2, US 4.7 +/- 6.4 versus 54.4 +/- 25.9, FINDIAM 4.3 +/- 5.2 versus 37.5 +/- 22.1, and MEDDIAM 3.4 +/- 4.2 versus 50.7 +/- 20.1, respectively (all P < 0.01). The mean time in seconds to reach the clinical endpoint ranged from HAND 289 +/- 193, US 194 +/- 67, FINDIAM 167 +/- 71, to MEDDIAM 147 +/- 92. All powered instruments were significantly faster than HAND (P < 0.05), but did not differ from each other. On a 0 = "smooth" to 3 = "rough" scale, most often HAND resulted in "smooth" surfaces (10/20), the powered tips of all types "slight" surface roughness (10/20 each), and US the most "moderate" roughness (7/20). There were no differences in percent calculus remaining, surface roughness, or time spent among the 3 treating clinicians despite their varying experience levels. The results of this study showed that percent calculus remaining was <5% with all the instruments given time ad libitum on a given root surface. Root roughness was generally slightly greater with all 3 powered tips. All of the powered instruments took significantly less time than the HAND. Both DIAM tips took less time than US. Diamond-coated ultrasonic tips appeared to be much more efficient than HAND or US in removing calculus in moderate-deep probing depths on single-rooted teeth in vivo.

Clinical comparison of desired versus actual amount of surgical crown lengthening

The actual length of clinically exposed tooth structure between planned restoration margin and alveolar crest ("biologic width") obtained during surgical crown elongation procedures was compared to the textbook goal of 3.0 mm. Sixteen (16) patients with 21 teeth requiring surgical crown lengthening for restoration placement participated. Oral hygiene instructions were given and optimal plaque control was mandatory. At each clinician's discretion, surgical techniques consisted of either gingivectomy or an apically positioned flap with and without osseous resection. Utilizing a reference stent, measurements were obtained at the facial, mesial-facial, lingual, and distal-lingual of the treated teeth both before and after osseous reduction. Parameters evaluated were gingival margin position, probing depth, mucogingival junction position, alveolar crest location, mobility, plaque index, and gingival index. These measurements were again recorded 8 weeks after surgery with the exception of alveolar crest. Statistical analysis with the paired t-test and linear correlation showed no significant change from baseline or among operators with varying experience in any of these parameters. Overall the results showed that the default objective of 3 mm between planned restoration margin and alveolar crest was not routinely achieved (mean 2.4 +/- 1.4 mm). The post-treatment distance from the planned restoration margin to the alveolar crest was greatest at the facial aspect of the teeth (mean 2.6 +/- 1.2 mm) and least at the distal-lingual (mean 2.2 +/- 1.7 mm). In addition, although more experienced periodontists removed a larger amount of bone, the amount of root surface exposed was still short of the initially desired biologic width.(ABSTRACT TRUNCATED AT 250 WORDS)

Rapidly Polymerized Collagen Gel as a Smoothing Agent in Excimer Laser Photoablation

BACKGROUND

Excimer laser photoablation effectively and precisely removes corneal tissue but may not smooth irregularities on the anterior corneal surface. An even surface might be obtained by applying a smoothing substance that fills in irregularities and ablates at the same rate as corneal tissue. Evaluation of collagen gel as a smoothing agent is reported.

METHODS

Pure, type I collagen solutions were prepared to remain soluble at physiological pH and to spontaneously gel when exposed to cationic buffers. Collagen gels were formed on the surface of enucleated porcine corneas and on human donor corneas and exposed to varying pulses of 193-nanometer excimer laser energy. Effects of collagen gel on ablation depth, corneal surface smoothness, and smoothing of roughened cornea were evaluated by examining scanning electron micrographs of control and treated specimens.

RESULTS

Collagen gels formed from 5 mg/ml collagen solutions dramatically altered the depth of photoablation. Photoablation of roughened cornea with collagen gels produced smooth corneal surfaces, whereas control eyes remained roughened and irregular. The smoothness of photoablated cornea surfaces improved when collagen gels were applied prior to photoablation.

CONCLUSIONS

The rapidly gelling collagen solution appears to exhibit the functional properties required for an effective smoothing agent for excimer laser photoablation. The substance has low viscosity when applied to the corneal surface and forms a rigid gel when exposed to cationic buffer solution. In addition, the concentration of the collagen gel can be adjusted to provide different ablation rates.

Effect of equilibration zones on stability, uniformity, and homogeneity profiles of vapors and aerosols in the ADG nose-only inhalation exposure system

A commercially available, inexpensive, nose-only exposure chamber was modified to include removable equilibration zones, and the effect of these zones on chamber performance was determined. Since limited performance data were available concerning this unit, a more extensive characterization was performed. EPA limit concentrations (greater than or equal to 5 mg/liter) of toluene vapor or corn oil aerosol, and relatively low concentrations of uranine aerosol (less than or equal to 50 micrograms/liter) were produced by standard techniques. The presence or absence of equilibration zones did not affect the stability or uniformity of toluene vapor atmospheres, with the coefficient of variation (CV) not exceeding 3.33% in all experiments. In contrast, the presence of two equilibration zones was found to progressively enhance the uniformity of the inhalable test aerosols in the animal exposure zone (CV less than or equal to 3.16%). Matrix sampling revealed that in both uranine and corn oil experiments, the center matrix point concentration was consistently lower than samples taken in the actual animal breathing zone. Equilibration zones markedly reduced the difference between breathing zone and center point concentrations. These performance data indicated that the modified ADG nose-only exposure system performed exceptionally well with the materials that were studied. Results were comparable to those describing whole-body chamber performance. The ready availability of this inexpensive prototype lends itself to standardization of techniques between laboratories.

Effects of brain hypoxia on pulmonary hemodynamics

The effects of acute brain hypoxia on pulmonary hemodynamics were investigated in anesthetized dogs with the vagus and carotid sinus nerves intact and cut. Following ligation of collateral vessels, brain hypoxia was induced by pumping arterial blood through a ventilated extracorporeal lung to the external carotid arteries for 5 min. In the intact-nerve group brain hypoxia caused no change in pulmonary and systemic vascular pressures and resistances. In the cut-nerve group brain hypoxia caused an increase in mean pulmonary artery, left atrial, pulmonary artery pulse, and mean aortic pressures. Cardiac output, dP/dt, central blood volume, and total peripheral resistance increased but pulmonary vascular resistance and lung extravascular thermal volume were unchanged. It is concluded that acute brain hypoxia does not increase pulmonary vascular resistance but may increase pulmonary blood volume resulting from increased left ventricular afterload.

Effects of histamine on lung water and hemodynamics after beta-blockade

The effects of 90 min intravenous histamine (10 micrograms base . kg-1 . min-1) with and without beta (propranolol)-receptor blockade on lung water and hemodynamics were studied. In anesthetized dogs cold 3% saline was used as the indicator to determine cardiac index, central blood volume, and lung extravascular thermal volume. Propranolol alone decreased stroke volume and cardiac index but increased central blood volume, total peripheral resistance, and mean pulmonary arterial and pulmonary arterial wedge pressures. Pulmonary vascular resistance, mean arterial pressure, and lung extravascular thermal volume were not changed. Histamine with propranolol further reduced stroke volume and cardiac index, whereas mean pulmonary arterial and pulmonary arterial wedge pressures returned to control values. Mean arterial pressure, central blood volume, and total peripheral resistance decreased, pulmonary vascular resistance increased, and lung extravascular thermal volume remained unchanged. In all experiments postmortem extravascular lung water-to-dry weight ratio was unchanged. We conclude that histamine does not increase lung water content and that beta-receptor blockade does not modify this response.

Local vasoactivity of oxygen and carbon dioxide in the right coronary circulation of the dog and pig

1. Eight mongrel dogs were anaesthetized with sodium thiamylal and chloralose-urethane, ventilated, vagotomized and heparinized. Five Poland-China pigs were anaesthetized with sodium thiamylal and nitrous oxide, ventilated, vagotomized and heparinized. 2. Extracorporeal perfusion of the right coronary artery at constant pressure (100 mmHg) was instituted. A lung from a donor animal was interposed in the coronary perfusion circuit to effect changes in CO2 and O2 tensions in the coronary arterial blood while systemic blood gases were maintained at normal levels. 3. Local hypoxia (PO2 range 17-22 mmHg) produced a 25-75% decrease in coronary vascular resistance (P less than 0.05) and a 0-24% (not significant) decrease in right ventricular dP/dt. 4. Local changes in PCO2 over the range 8-105 mmHg were associated with a 17-58% decrease in coronary vascular resistance (P less than 0.05), a 19-24% decrease in right ventricular dP/dt (P less than 0.05) with no change in right ventricular end-diastolic pressure, and a 1-18% (not significant) decrease in heart rate. 5. These studies suggest that local decreases in O2 or increases in CO2 tensions produce decreases in right coronary vascular resistance that are in the opposite direction to those that would be expected from the observed changes in heart rate and contractility (two primary determinants of myocardial oxygen consumption). 6. These data support the hypothesis that CO2 and O2 are locally vasoactive in the coronary circulation.

Central blood volume and lung extravascular thermal volume in dogs with dirofilariasis

Central blood volume, lung extravascular thermal volume, cardiac output, and pulmonary and systemic vascular pressures were measured in clinically normal and heartworm-infected dogs. Central blood volume and cardiac output were significantly (P less than 0.05) decreased in heartworm-infected dogs compared with the in normal dogs. Pulmonary vascular resistance, total peripheral resistance, mean pulmonary artery, pulmonary artery wedge, and pulse pressures were significantly increased in heartworm-infected dogs compared with that in normal dogs. Significant differences between normal and heartworm-infected dogs were not found in lung extravascular thermal volume, pulmonary extravascular tissue weight, or extravascular lung water to extravascular dry-weight ratio. Lung extravascular thermal volume overestimated gravimetric pulmonary extravascular tissue weight by approximately 16%. A significant correlation (R = 0.83) existed between pulmonary extravascular tissue weight and lung extravascular thermal volume for all dogs.

Vascular response of the chicken hindlimb to vasoactive agents, asphyxia, and exercise

Previous studies in live chickens have measured heart rate, blood pressure, and cardiac output during drug administration or asphyxia and made assumptions concerning the peripheral vasculature. The present study employs a constant-flow, isolated hindlimb perfusion technique to measure directly changes in skeletal muscle vascular resistance induced either by local intra-arterial (i.a.) bolus, or continuous i.a. infusion, of various vasoactive substances. Prostaglandin E1 (0.5 microgram, bolus) produced arteriolar vasodilation lasting 10 min, as indicated by a fall ian perfusion pressure. Bolus injection of histamine (10 microgram diphosphate) or adenosine (5 and 10 microgram) produced vasodilation of less than 2-min duration. Theophylline infusion (5 microM infused at 1 mL/min, i.a.) blocked the effect of adenosine. Norepinephrine (1 microgram) produced vasoconstriction which was reduced 60% by systemic alpha-adrenergic blockade with phenoxybenzamine (7.5-10 mg/kg). Tracheal occlusion produced intense vasoconstriction which was reduced 70% by alpha-adrenergic blockade. Electrical stimulation of the peripheral end of the cut sciatic nerve (6 Hz) produced an immediate vasodilation lasting several minutes.

Flow through collapsible tubes at high Reynolds numbers

The pressure-flow relationships of collapsible tubes were studied utilizing the Starling resistor model. Reynolds numbers much higher than previously reported were used to simulate high cardiac output states. Alterations which occur in vivo, including longitudinal tension, stretch, tubing diameter, length, and outflow resistance were also simulated and systematically investigated. The pressure-flow curves showed an initial rising phase, a plateau phase, as well as a late-rising phase which has not been reported previously. Self-induced oscillations occurred during the plateau phase and persisted throughout the late-rising phase. These perturbations were markedly increased by longitudinal tension and stretch, but were attenuated by increased diameter, length, and outflow pressure. These instabilities may prove to be an explanation for the "venous hum."

Carotid sinus reflex vasoconstriction in right coronary circulation of dog and pig

This study was designed to evaluate the effects of the sympathetic nervous system on right ventricular and right coronary hemodynamics in the anesthetized vagotomized dog and pig during constant-pressure coronary perfusion. Carotid occlusion in the dog resulted in an increase in heart rate, aortic pressure, right ventricular dP/dt, and a sustained 13% decrease in right coronary artery blood flow and a 14% increase in coronary vascular resistance. This coronary vasoconstriction was not modified during beta-blockade with propranolol but was prevented by alpha- blockade with phentolamine. Similar hemodynamic data was obtained in the pig and, in addition, it was found that the O2 consumption of the right ventricle is low (4.8 +/- 0.4 ml O2.min-1.100 g-1) and is only slightly increased (5.l5 +/- 0.8 ml.min-1.100 g-1) during carotid occlusion. These data suggest that baroreflex-mediated sympathetic stimulation to the heart evokes only a minor increase in metabolic activity in the right ventricular myocardium so that the direct neural (alpha-vasoconstrictor) effect predominates over the metabolic vasodilator mechanism.

Systemic and digital vascular effects of intravenous histamine in the pony

The effects of a 60-minute IV infusion of histamine (0.5 mg of histamine base/minute) on the systemic, pulmonary, and digital vasculature were investigated in mature ponies. Immediately after the start of histamine infusion, there were a transient decrease in systemic pressure lasting less than 1 minute and then a brief period of systemic hypertension. Systemic pressure then returned to preinfusion levels for the remainder of the infusion period. Pulmonary arterial pressure increased transiently coincident with systemic hypotension. Histamine increased cardiac output and decreased both total peripheral and pulmonary vascular resistances. In the digit, blood flow increased for the duration of the systemic hypertension, but was otherwise unchanged. Digital lymph flow and protein concentration were unchanged by histamine. Hematocrit increased significantly after 60 minutes of histamine infusion, but plasma and blood volumes were unchanged. Histamine caused cyanosis, hyperpnea, and sweating in all ponies. The effects of histamine given IV do not mimic the systemic and digital vascular effects of acute alimentary laminitis.

Vascular and hematologic effects of hemorrhage in the chicken

Chickens have been reported to have a rate of posthemorrhagic fluid mobilization twice that of mammals and lack a phase of shock irreversible to transfusion. In the present study we measured several hemodynamic and hematologic parameters in chickens subjected to sustained hemorrhagic hypotension. Total peripheral resistance was unaffected or fell slightly and skeletal muscle vascular resistance judged from changes in gastrocnemius resistance was not affected by hemorrhage. Blood compositional changes included a progressive hyperkalemia, hyperglycemia, and hemodilution as evidenced by linear falls in hematocrit, hemoglobin, and plasma total protein concentration. Plasma sodium and osmolality were unchanged, as were arterial pH and oxygen tension; however, there was a fall in carbon dioxide tension. These studies demonstrate that fluid mobilization in the chicken after hemorrhage does not require an increase in precapillary resistance and suggest that, because the chicken does not exhibit intense precapillary constriction, it is spared some of the deleterious effects of inadequate tissue perfusion. Thus, the findings tend to incriminate the peripheral action of the sympathetic nervous system as a major contributor to the development of irreversibility in other species.

Effect of pulmonary venous pressure on steady-stage collateral resistance

Steady-state collateral resistance (Rcoll), residual volume (RV), and lung pressure-volume (PV) relations were determined in an isolated perfused dog lung as pulmonary venous pressure (Ppv) was increased. Increased Ppv had no effect on the lung PV curve except for a significant increase in RV when Ppv equaled or exceeded 20 Torr. When compared to the value at Ppv = 5 Torr, significant decreases in Rcoll occurred when Ppv was raised to 15 Torr or above at transpulmonary pressure, PL = 0 cmH2O, to 20 Torr or above when PL = 2 cmH2O, and to 25 Torr or above when PL = 4 cmH2O. In most dogs the decrease in Rcoll with increased Ppv could be explained by increased lung volume.

Flow through collapsible tubes at low Reynolds numbers. Applicability of the waterfall model

The applicability of the waterfall model was tested using the Starling resistor and different viscosities of fluids to vary the Reynolds number. The waterfall model proved adequate to describe flow in the Starling resistor model only at very low Reynolds numbers (Reynolds number less than 1). Blood flow characterized by such low Reynolds numbers occurs only in the microvasculature. Thus, it is inappropriate to apply the waterfall model indiscriminately to flow through large collapsible veins.

Evidence from bioassay studies indicating a role for adenosine in cardiac ischemic and hypoxic dilation in the dog

Previous studies using bioassay demonstrated the presence of a vasoactive substance or substances in coronary sinus blood during myocardial reactive hyperemia which had, on bioassay, characteristics of adenosine and/or AMP. In the present studies, specific blockers were applied to an improved bioassay system to define more precisely the nature of the substance or substances and to determine whether it also appears during local cardiac hypoxia. In the anesthetized dog, coronary sinus blood was bioassayed in an isolated autologous kidney during reactive and hypoxic dilation. During reactive dilation, the bioassay kidney responded with a large resistance increase which was blocked by theophylline and adenosine deaminase and converted to a decrease by adenosine autoblockade. The same was true for hypoxic dilation, except in this instance, only adenosine deaminase reduced the response (40%). Theophylline and adenosine autoblockade eliminated responses of the bioassay organ to both exogenous adenosine and exogenous AMP, but adenosine deaminase was specific for adenosine. These results confirm that one or more vasoactive substances appear in sinus blood in vasoactive quantities during cardiac reactive dilation, and that the peak concentration correlates roughly with the peak flow. In addition, they show that this also is the case for hypoxic dilation. More importantly, they demonstrate that the substance almost certainly is adenosine in the case of reactive dilation, and that increased adenosine levels also are present during hypoxic dilation, but in addition, suggest that AMP sometimes appears in coronary sinus blood during severe cardiac hypoxia in the dog heart.

Cardiovascular, acid-base, electrolyte, and plasma volume changes in ponies developing alimentary laminitis

Twelve Shetland ponies were fed a high-starch ration. Seven ponies which had a transitory metabolic acidosis developed laminitis 56 hours (+/- 3.5, SEM) after overfeeding. These ponies also developed persistent hypokalemia, hyperthermia, and increased heart rate 24 hours before the onset of lameness. Serum sodium, serum chloride, hematocrit, plasma volume, and blood volume were unchanged. At the onset of clinical signs of laminitis, cardiac output and blood pressure increased, but total peripheral resistance was unchanged. None of the measured or calculated values predicted the onset of laminitis. Hypertension appeared to be a response to, rather than a cause of, lameness. Three of the remaining ponies apparently died of shock 29.3 +/- 2.7 hours after overfeeding. All 3 had severe metabolic acidosis; decreased cardiac output, systemic arterial pressure, and plasma volume; and increased hematocrit, total peripheral resistance, and pulmonary vascular resistance. The 11th pony was unaffected and the 12th pony was euthanatized.

Antagonism of histamine edema formation by catecholamines

Histamine (4 microgram base/min) infused into the brachial artery for 60 min greatly increases skin lymph flow and lymph protein concentration in forelimbs perfused either naturally or at constant inflow. In contrast, the simultaneous intrabrachial infusion of histamine and norepinephrine (4 microgram base/min of each) or histamine and isoproterenol (4 microgram base/min and 3 microgram/min, respectively) for 60 min failed to alter lymph protein concentration in forelimbs perfused either naturally or at constant inflow. The edema in forelimbs naturally perfused by histamine (4 microgram base/min) infused into the brachial artery for 60 min was also greatly reduced by the simultaneous histamine-catecholamine infusions. Phentolamine (in concentrations that antagonize the vascular actions of norepinephrine) failed to prevent the antagonism of histamine protein efflux by norepinephrine. Hence, it must be concluded that catecholamines antagonize the protein efflux by locally infused histamine, independent of alpha-adrenergic receptor activity.

An extracorporeal shunt for the measurement of coronary flow in the closed-chest dog

An extracorporeal shunt circuit interposed between the left carotid artery and the left coronary ostium employs an electromagnetic flowmeter to measure coronary blood flow in the closed-chest anesthetized dog. Flow may be measured with the animal's arterial pressure as the driving force; introduction of a roller pump, or a roller pump and a negative feedback pressure controller allows for constant flow or constant pressure modes. During occlusion of the circuit or cessation of pump flow, retrograde coronary blood flow can be collected for measurement. The construction of the circuit is relatively simple and inexpensive, using common laboratory materials and a commercially available electromagnetic flowmeter and probe.

Effects of systemically infused histamine on transvascular fluid and protein transfer

Histamine (4-64 microgram base/min) infused into the brachial artery clearly promotes edema formation in forelimbs perfused at natural flow. In contrast, intravenously administered histamine, even in blood concentrations exceeding those achieved by local infusion, not only fails to promote edema formation, but rather causes net extravascular fluid reabsorption. In this study, high concentrations of histamine were infused into the left ventricular chamber to bypass the pulmonary circuit. Histamine (400-800 microgram base/min) infused into the left ventricle of the heart for 90 min produced marked hypotension and only very slight increases in forelimb skin lymph flow and lymph protein concentration and failed to produce visible signs of edema. Thus the differential actions of local and intravenous histamine on lymph flow, protein efflux, and fluid fluxes cannot be explained by uptake or destruction of histamine in the lung during intravenous infusions of this agent. It seems more likely that they result from different actions on microvascular pressure, surface area, and/or permeability to plasma proteins. Prior hypotension produced either by acetylcholine, systemically infused histamine, or arterial hemorrhage almost completely prevents the increase in skin lymph flow and lymph protein concentration by histamine infused locally into the brachial artery, even in forelimbs perfused at constant flow.