Extended-spectrum ß-lactamase-producing Enterobacterales in diverse foodstuffs: a prospective, longitudinal study in the city of Basel, Switzerland.

Background: The involvement of non-human-to-human transmission of extended-spectrum ß-lactamase-producing Enterobacterales (ESBL-PE) remains elusive. Foodstuffs may serve as reservoirs for ESBL-PE and contribute to their spread. Aim: We aimed to systematically investigate the presence and spatiotemporal distribution of ESBL-PE in diverse unprocessed foodstuffs of different origin purchased in a central European city. Methods: Chicken and green (herbs, salad, sprouts, vegetables) samples were collected monthly for two consecutive years, from June 2017 to June 2019, from large supermarket chains and small local food retailers, representing all ten postcode areas of the City of Basel (Switzerland), and the kitchen of the University Hospital Basel (Basel, Switzerland). After enrichment, presumptive ESBL-PE were isolated by selective culture methods and identified by Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. ESBL production was confirmed by phenotypic testing. Results: Among 947 food samples, 14.8% were positive for ESBL-PE isolate/s belonging to eight different ESBL-producing bacterial species. Escherichia coli and Serratia fonticola were predominant across samples (9 and 2%, respectively). Higher ESBL-PE prevalence was observed in chicken (25.9%) than in green (3.8%) samples (p < 0.001). Among greens, ESBL-PE were most frequently isolated from sprouts (15.2%). High ESBL-PE species diversity was observed among chicken samples, with E. coli as predominant (17.6%). ESBL-producing Enterobacter cloacae was detected among different greens. Yet, ESBL-producing Klebsiella pneumoniae was predominant in sprouts (12.1%). In total, 20.5% of samples from organic farming and 14.2% of samples from conventionally raised animals harbored an ESBL-producing isolate. Detection of ESBL-PE across samples differed between organic and non-organic when stratified by food source (p < 0.001), particularly among greens (12.5% organic, 2.4% conventional). High proportion of organic chicken samples was positive for ESBL-E. coli (33.3%), while the detection of several species characterized the conventional chicken samples. No significant differences in ESBL-PE frequences were detected between national (13.4%) and international samples (8.0%) (p = 0.122). Instead, differences were observed between regions of food production and countries (p < 0.001). No significant differences were found when comparing the proportion of ESBL-PE positive samples across districts, shop sizes and the hospital kitchen. The percentage of ESBL-PE positive samples did not differ monthly across the two-year sampling period (p = 0.107). Conclusion: Our findings indicate moderate dissemination of ESBL-PE in foodstuffs, especially between chicken products and sprouts. Chicken meat represents a source for several ESBL-producing Enterobacterales, especially E. coli, while greens are more prone to carry ESBL-K. pneumoniae and E. cloacae. We disclose the importance of food type, food production system and production origin when assessing the risk of contamination with different ESBL-PE species.

Within-host genetic diversity of extended-spectrum beta-lactamase-producing Enterobacterales in long-term colonized patients.

Despite recognition of the immediate impact of infections caused by extended-spectrum beta-lactamase (ESBL)-producing Enterobacterales (ESBL-PE) on human health, essential aspects of their molecular epidemiology remain under-investigated. This includes knowledge on the potential of a particular strain to persist in a host, mutational events during colonization, and the genetic diversity in individual patients over time. To investigate long-term genetic diversity of colonizing and infecting ESBL-Klebsiella pneumoniae species complex and ESBL-Escherichia coli in individual patients over time, we performed a ten-year longitudinal retrospective study and extracted clinical and microbiological data from electronic health records. In this investigation, 76 ESBL-K. pneumoniae species complex and 284 ESBL-E. coli isolates were recovered from 19 and 61 patients. Strain persistence was detected in all patients colonized with ESBL-K. pneumoniae species complex, and 83.6% of patients colonized with ESBL-E. coli. We frequently observed isolates of the same strain recovered from different body sites associated with either colonization or infection. Antimicrobial resistance genes, plasmid replicons, and whole ESBL-plasmids were shared between isolates regardless of chromosomal relatedness. Our study suggests that patients colonized with ESBL-producers may act as durable reservoirs for ongoing transmission of ESBLs, and that they are at prolonged risk of recurrent infection with colonizing strains.

Spatiotemporal dissemination of ESBL-producing Enterobacterales in municipal sewer systems: a prospective, longitudinal study in the city of Basel, Switzerland.

Background: The contribution of community and hospital sources to the transmission of extended-spectrum ß-lactamase producing Enterobacterales (ESBL-PE) remains elusive. Aim: To investigate the extent of community dissemination and the contribution of hospitals to the spread of ESBL-PE by exploring their spatiotemporal distribution in municipal wastewater of the central European city of Basel. Methods: Wastewater samples were collected monthly for two consecutive years throughout Basel, Switzerland, including 21 sites across 10 postcode areas of the city collecting either community wastewater (urban sites, n = 17) or community and hospital wastewater (mixed sites, n = 4). Presumptive ESBL-PE were recovered by selective culture methods. Standard methodologies were applied for species identification, ESBL-confirmation, and quantification. Results: Ninety-five percent (477/504) of samples were positive for ESBL-PE. Among these isolates, Escherichia coli (85%, 1,140/1,334) and Klebsiella pneumoniae (11%, 153/1,334) were most common. They were recovered throughout the sampling period from all postcodes, with E. coli consistently predominating. The proportion of K. pneumoniae isolates was higher in wastewater samples from mixed sites as compared to samples from urban sites, while the proportion of E. coli was higher in samples from urban sites (p = 0.003). Higher numbers of colony forming units (CFUs) were recovered from mixed as compared to urban sites (median 3.2 × 102 vs. 1.6 × 102 CFU/mL). E. coli-counts showed moderate correlation with population size (rho = 0.44), while this correlation was weak for other ESBL-PE (rho = 0.21). Conclusion: ESBL-PE are widely spread in municipal wastewater supporting that community sources are important reservoirs entertaining the spread of ESBL-PE. Hospital-influenced abundance of ESBL-PE appears to be species dependent.

Systematic screening on admission for SARS-CoV-2 to detect asymptomatic infections.

The proportion of asymptomatic carriers of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains elusive and the potential benefit of systematic screening during the SARS-CoV-2-pandemic is controversial. We investigated the proportion of asymptomatic inpatients who were identified by systematic screening for SARS-CoV-2 upon hospital admission. Our analysis revealed that systematic screening of asymptomatic inpatients detects a low total number of SARS-CoV-2 infections (0.1%), questioning the cost-benefit ratio of this intervention. Even when the population-wide prevalence was low, the proportion of asymptomatic carriers remained stable, supporting the need for universal infection prevention and control strategies to avoid onward transmission by undetected SARS-CoV-2-carriers during the pandemic.

Identification of a Cluster of Extended-spectrum Beta-Lactamase-Producing Klebsiella pneumoniae Sequence Type 101 Isolated From Food and Humans.

We report a cluster of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae sequence type 101, derived from 1 poultry and 2 clinical samples collected within the setting of a prospective study designed to determine the diversity and migration of ESBL-producing Enterobacterales between humans, foodstuffs, and wastewater.

Multicenter Prevalence Study Comparing Molecular and Toxin Assays for Clostridioides difficile Surveillance, Switzerland.

Public health authorities in the United States and Europe recommend surveillance for Clostridioides difficile infections among hospitalized patients, but differing diagnostic algorithms can hamper comparisons between institutions and countries. We compared surveillance based on detection of C. difficile by PCR or enzyme immunoassay (EIA) in a nationwide C. difficile prevalence study in Switzerland. We included all routinely collected stool samples from hospitalized patients with diarrhea in 76 hospitals in Switzerland on 2 days, 1 in winter and 1 in summer, in 2015. EIA C. difficile detection rates were 6.4 cases/10,000 patient bed-days in winter and 5.7 cases/10,000 patient bed-days in summer. PCR detection rates were 11.4 cases/10,000 patient bed-days in winter and 7.1 cases/10,000 patient bed-days in summer. We found PCR used alone increased reported C. difficile prevalence rates by <80% compared with a 2-stage EIA-based algorithm.

Transmission of ESBL-producing Enterobacteriaceae and their mobile genetic elements-identification of sources by whole genome sequencing: study protocol for an observational study in Switzerland.

INTRODUCTION: Extended-spectrum beta-lactamases (ESBL)-producing Enterobacteriaceae were first described in relation with hospital-acquired infections. In the 2000s, the epidemiology of ESBL-producing organisms changed as especially ESBL-producing Escherichia coli was increasingly described as an important cause of community-acquired infections, supporting the hypothesis that in more recent years ESBL-producing Enterobacteriaceae have probably been imported into hospitals rather than vice versa. Transmission of ESBL-producing Enterobacteriaceae is complicated by ESBL genes being encoded on self-transmissible plasmids, which can be exchanged among the same and different bacterial species. The aim of this research project is to quantify hospital-wide transmission of ESBL-producing Enterobacteriaceae on both the level of bacterial species and the mobile genetic elements and to determine if hospital-acquired infections caused by ESBL producers are related to strains and mobile genetic elements predominantly circulating in the community or in the healthcare setting. This distinction is critical in prevention since the former emphasises the urgent need to establish or reinforce antibiotic stewardship programmes, and the latter would call for more rigorous infection control. METHODS AND ANALYSIS: This protocol presents an observational study that will be performed at the University Hospital Basel and in the city of Basel, Switzerland. ESBL-producing Enterobacteriaceae will be collected from any specimens obtained by routine clinical practice or by active screening in both inpatient and outpatient settings, as well as from wastewater samples and foodstuffs, both collected monthly over a 12-month period for analyses by whole genome sequencing. Bacterial chromosomal, plasmid and ESBL-gene sequences will be compared within the cohort to determine genetic relatedness and migration between humans and their environment. ETHICS AND DISSEMINATION: This study has been approved by the local ethics committee (Ethikkommission Nordwest-und Zentralschweiz) as a quality control project (Project-ID 2017-00100). The results of this study will be published in peer-reviewed medical journals, communicated to participants, the general public and all relevant stakeholders.

Cognitive impairment in heart failure: results from the Trial of Intensified versus standard Medical therapy in Elderly patients with Congestive Heart Failure (TIME-CHF) randomized trial.

AIMS: Up to 50% of patients with heart failure (HF) may suffer from severe cognitive impairment (SCI), but longitudinal studies are sparse, and effects of changes in HF severity on cognitive function are unknown. Therefore, we assessed the prevalence of SCI in HF patients, its relationship with HF severity, its effects on morbidity and mortality, and the relationship between changes in HF severity and cognitive function. METHODS AND RESULTS: We included 611 patients from the Trial of Intensified versus standard Medical therapy in Elderly patients with Congestive Heart Failure (TIME-CHF) and assessed cognitive function [Hodkinson Abbreviated Mental Test (AMT)] in relation to severity of HF (NYHA class, NT-proBNP) at baseline and 18 months (n = 382) and effects on hospitalization-free survival and mortality. SCI (i.e. AMT score ≤ 7) was present in 9.2% of patients at baseline, but only 20% of them had a diagnosis of dementia. Prevalence of SCI remained stable during follow-up. SCI was present at baseline more often in NYHA IV patients compared with NYHA II [odds ratio 2.94; 95% confidence interval (CI) 1.15-7.51, P = 0.025], but it was not related to NT-proBNP levels. SCI was related to higher mortality (hazard ratio 1.53, 95% CI 1.02-2.30, P = 0.04), but not hospitalization-free survival. Changes in HF severity were not significantly related to changes in cognitive function. CONCLUSION: SCI is a frequent, but often unrecognized finding in HF patients, but the influence of HF severity and its changes on cognitive function were less than hypothesized. Trial registration ISRCTN43596477.

Why and how do elderly patients with heart failure die? Insights from the TIME-CHF study.

AIMS: Specific causes and modes of death (COD and MOD) of patients with heart failure (HF) are not well described, particularly in those with preserved ejection fraction >45% (HFPEF) and at old age. Thus, using the database of the TIME-CHF study, patients with HFPEF were compared with those with reduced ejection fraction ≤45% (HFREF), and patients ≥75 with those 60-74 years of age to identify MOD and COD, predictors of death, and event rates before death as compared with survivors. METHODS AND RESULTS: During the 18-month follow-up, 132/622 patients (21%) died, with similar rates in patients with HFPEF and HFREF and a trend to higher rates in patients aged ≥75 years (24% vs. 17%, P = 0.06). COD and MOD (ACME system) were not different in the age groups. COD was more often non-cardiovascular in HFPEF patients than in HFREF patients (33% vs. 16%, P < 0.05) and cardiac MOD were more frequent in HFREF patients (75% vs. 56%, P < 0.05), mainly due to more sudden deaths (25% vs. 7%, P < 0.05). Patients who died experienced a median of four adverse events (interquartile range 1-7) and one (0-1) hospitalization within 60 days prior to death compared with 0.7 (0.4-1.4) and 0.1 (0.0-0.2) during a randomly selected 60 days in survivors (all P < 0.0001). CONCLUSION: Despite similar 18-month mortality in patients with HFREF and those with HFPEF, important differences in COD and MOD were found which were not observed between the two age groups. A high rate of adverse events and hospitalizations preceded death. These observations may be relevant for the management of HF patients.

End-of-life preferences of elderly patients with chronic heart failure.

AIMS: Elderly heart failure (HF) patients are assumed to prefer improved quality of life over longevity, but sufficient data are lacking. Therefore, we assessed the willingness to trade survival time for quality-of-life (QoL) and the preferences for resuscitation. METHODS AND RESULTS: At baseline and after 12 and 18 months, 622 HF patients aged ≥60 years (77 ± 8 years, 74% NYHA-class ≥III) participating in the Trial of Intensified vs. standard Medical therapy in Elderly patients with Congestive Heart Failure had prospective evaluation of end-of-life preferences by answering trade-off questions (willingness to accept a shorter life span in return for living without symptoms) and preferences for resuscitation if necessary. The time trade-off question was answered by 555 patients (89%), 74% of whom were not willing to trade survival time for improved QoL. This proportion increased over time (Month 12: 85%, Month 18: 87%, P < 0.001). In multivariable analysis, willingness to trade survival time increased with age, female sex, a reduced Duke Activity Status Index, Geriatric Depression Score, and history of gout, exercise intolerance, constipation and oedema, but even combining these variables did not result in reliable prediction. Of 603 (97%) patients expressing their resuscitation preference, 51% wished resuscitation, 39% did not, and 10% were undecided, with little changes over time. In 430 patients resuscitation orders were known; they differed from patients' preferences 32% of the time. End-of-life preferences were not correlated to 18-month outcome. CONCLUSION: Elderly HF patients are willing to address their end-of-life preferences. The majority prefers longevity over QoL and half wished resuscitation if necessary. Prediction of individual preferences was inaccurate.

Detection of intake of nonsteroidal anti-inflammatory drugs in elderly patients with heart failure. How to ask the patient?

PRINCIPLES: Heart failure hospitalisations may be related to non-steroidal anti-inflammatory drug (NSAID) use. Since NSAIDs are usually prescribed by general practitioners or taken without prescription, their use may be largely underestimated. Therefore, we assessed the impact of a focussed analgesic medication history as compared to a usual medication history on detection of NSAID intake in elderly heart failure patients and the potential effect of medical advice on discontinuation of this therapy in a non-controlled study design. METHODS: A structured and stepwise history of analgesic intake (firstly open questioning about medication intake, secondly with a focus on analgesic intake, finally focussing on behaviour in case of pain) was done in 197 elderly heart failure patients taking part in the TIME-CHF study at baseline and up to 3 follow-up visits. All participants were informed about the potential hazardous effects of NSAIDs and alternative analgesic therapy was proposed in case of NSAID intake. Patients were aged 60 years or older with clinical signs of heart failure NYHA > or =II, elevated NT-BNP, and had been hospitalised due to heart failure within the last year. Details of this study have been described previously. RESULTS: At baseline, 43 patients (22%) were taking NSAID. Almost half (n = 19) taking NSAID reported the use only after specific questioning. Therefore, a focussed analgesic medication history was superior as compared to a usual medication history to detect patients taking NSAIDs (22% vs 12%; p <0.001). After instruction and proposal of alternative analgesic therapy, NSAID intake dropped from 22% to 7% (p <0.001). No risk factor for continuous use was identified. CONCLUSIONS: NSAID use in heart failure patients is relatively common. Specific questioning may help to increase detection of NSAID intake and information on its hazardous effects to decrease NSAID use.

BNP-guided vs symptom-guided heart failure therapy: the Trial of Intensified vs Standard Medical Therapy in Elderly Patients With Congestive Heart Failure (TIME-CHF) randomized trial.

CONTEXT: It is uncertain whether intensified heart failure therapy guided by N-terminal brain natriuretic peptide (BNP) is superior to symptom-guided therapy. OBJECTIVE: To compare 18-month outcomes of N-terminal BNP-guided vs symptom-guided heart failure therapy. DESIGN, SETTING, AND PATIENTS: Randomized controlled multicenter Trial of Intensified vs Standard Medical Therapy in Elderly Patients With Congestive Heart Failure (TIME-CHF) of 499 patients aged 60 years or older with systolic heart failure (ejection fraction < or = 45%), New York Heart Association (NYHA) class of II or greater, prior hospitalization for heart failure within 1 year, and N-terminal BNP level of 2 or more times the upper limit of normal. The study had an 18-month follow-up and it was conducted at 15 outpatient centers in Switzerland and Germany between January 2003 and June 2008. INTERVENTION: Uptitration of guideline-based treatments to reduce symptoms to NYHA class of II or less (symptom-guided therapy) and BNP level of 2 times or less the upper limit of normal and symptoms to NYHA class of II or less (BNP-guided therapy). MAIN OUTCOME MEASURES: Primary outcomes were 18-month survival free of all-cause hospitalizations and quality of life as assessed by structured validated questionnaires. RESULTS: Heart failure therapy guided by N-terminal BNP and symptom-guided therapy resulted in similar rates of survival free of all-cause hospitalizations (41% vs 40%, respectively; hazard ratio [HR], 0.91 [95% CI, 0.72-1.14]; P = .39). Patients' quality-of-life metrics improved over 18 months of follow-up but these improvements were similar in both the N-terminal BNP-guided and symptom-guided strategies. Compared with the symptom-guided group, survival free of hospitalization for heart failure, a secondary end point, was higher among those in the N-terminal BNP-guided group (72% vs 62%, respectively; HR, 0.68 [95% CI, 0.50-0.92]; P = .01). Heart failure therapy guided by N-terminal BNP improved outcomes in patients aged 60 to 75 years but not in those aged 75 years or older (P < .02 for interaction) CONCLUSION: Heart failure therapy guided by N-terminal BNP did not improve overall clinical outcomes or quality of life compared with symptom-guided treatment. TRIAL REGISTRATION: isrctn.org Identifier: ISRCTN43596477.

Influence of acute and chronic mineralocorticoid excess on endothelial function in healthy men.

Aldosterone has rapid nongenomic effects in the human vasculature. However, data are not uniform and little is known about chronic effects of aldosterone. Therefore, we investigated acute and chronic effects of elevated aldosterone levels on endothelial function in the forearm vasculature of healthy men. In a first crossover study, the effects of arterial aldosterone infusion in ascending doses (3.3 to 55 pmol/min per 1000 mL forearm volume) on forearm blood flow were investigated in 8 healthy men (26+/-2 years). In a second study, endothelium-dependent (acetylcholine; 0.08, 0.275, and 2.75 micromol/min per 1000 mL) and endothelium-independent (sodium nitroprusside 0.02 micromol/min per 1000 mL) vasodilation and basal nitric oxide formation (forearm blood flow response to blockade by N(G)-monomethyl-l-arginine 8 micromol/min per 1000 mL) were tested in 10 healthy men (age 30+/-5 years) at baseline, during infusion of 55 pmol/1000 mL per min aldosterone (acute effects), and after 0.3 mg/d oral fludrocortisone for 2 weeks (chronic effects) on separate days. Forearm blood flow was assessed by venous occlusion plethysmography. No change in forearm blood flow was seen with aldosterone infusion alone. Acute coinfusion of aldosterone increased vasodilation to sodium nitroprusside by 93% (P<0.01) and to acetylcholine by 60% (P=0.14). Response to N(G)-monomethyl-l-arginine did not change. After 2 weeks of oral fludrocortisone, response to acetylcholine was enhanced by 72% compared with baseline (P=0.03). Additionally, response to N(G)-monomethyl-l-arginine was enhanced by 80% compared with baseline (P=0.05). Aldosterone acutely enhances vasodilation to exogenous nitric oxide whereas mineralocorticoid excess for 2 weeks enhances basal nitric oxide bioactivity and improves endothelium dependent, nitric oxide-mediated vasodilation in the forearm vasculature of healthy men.

Management of elderly patients with congestive heart failure--design of the Trial of Intensified versus standard Medical therapy in Elderly patients with Congestive Heart Failure (TIME-CHF).

BACKGROUND: Little is known about the management of elderly patients with congestive heart failure (CHF) although they represent the majority of the CHF population. Therefore, the TIME-CHF study was set up (1) to evaluate the medical management of very old patients (> or = 75 years) with CHF compared with younger patients (60-74 years), (2) to compare an intensified with a standard treatment approach, and (3) to differentiate between systolic and diastolic dysfunction (ejection fraction < or = 45% vs > 45%). METHODS: In a prospective single-blinded multicenter trial, 824 symptomatic patients, CHF hospitalization within the last year and elevated NT-BNP, are randomized to an intensified versus a standard medical therapy. Treatment strategies follow the published guidelines with the aim to reduce symptoms to NYHA class < or = II (standard) or, additionally, NT-BNP levels below twice the upper limit of normal (intensified). The primary end points are 18-month hospitalization-free survival and quality of life. RESULTS: By the end of 2004, 297 patients have been included, 147 randomized to intensified and 150 to standard therapy. Mean age in the older age group was 82 +/- 4 years (n = 174) and 69 +/- 4 years in the younger group (n = 123), respectively. Ejection fraction was > 45% in 26% and 10%, respectively. Significant comorbidities were present in 93% of patients. CONCLUSION: TIME-CHF will be the first prospective randomized trial to comprehensively study the management of elderly patients with CHF. It will provide unique information comparing two treatment strategies in two age groups irrespective of ejection fraction regarding prognosis, quality of life, as well as resource utilization and costs.

Systemic endothelial dysfunction in adults with cyanotic congenital heart disease.

BACKGROUND: Secondary erythrocytosis results in increased shear stress in cyanotic congenital heart disease (CCHD), which may modify the balance between vasodilators and vasoconstrictors and affect systemic endothelial function. Because no data are available on systemic vasomotion, systemic endothelial function and nitric oxide (NO) availability were investigated in CCHD patients. METHODS AND RESULTS: Responses to arterial endothelium-dependent (acetylcholine [Ach]) and -independent (sodium nitroprusside [SNP]) vasodilation, NO synthase blockade (NG-monomethyl-L-arginine [L-NMMA]), endothelin-1 (ET-1), and ET-1 receptor blockade by BQ-123 in 11 CCHD patients (O2 saturation <90%; mean+/-SD, 79+/-1%; mean+/-SD age, 39+/-2 years) were compared with those in 10 age-matched healthy referents by using forearm venous occlusion plethysmography. Resting forearm blood flow (FBF) was lower in CCHD patients than in referents (2.4+/-0.2 versus 3.5+/-0.4 mL.min(-1).100 mL(-1) of forearm volume [FAV], P<0.05). Although the response to SNP was similar in both groups (CCHD, 2.0+/-0.3 to 8.3+/-1.0; referents, 3.6+/-0.7 to 11.9+/-1.2 mL.min(-1).100 mL(-1) of FAV; P>0.1), the response to Ach was markedly reduced in CCHD (maximal increase in FBF, 2.8+/-0.8 versus 37.5+/-4.4 mL.min(-1).100 mL(-1) of FAV; P<0.0001). l-NMMA was less effective in CCHD (decrease in FBF, 25+/-6% versus 40+/-4%; P<0.05). ET-1 caused less vasoconstriction in the CCHD group (-25+/-9% versus -51+/-7%, P<0.05), but the response to BQ-123 was similar in both groups (32+/-9% versus 27+/-9%). CONCLUSIONS: Systemic endothelial dysfunction is evident in CCHD patients as shown by strikingly reduced endothelial vasodilation to Ach. The response to exogenous ET-1 is reduced, possibly because of elevated endogenous ET-1 levels, but the effects of endogenous ET-1 on arterial tone are not enhanced, as indicated by the similar response to ET-1 blockade.

Vascular effects of natriuretic peptides in healthy men.

BACKGROUND: Most effects of atrial (ANP) and B-type natriuretic peptide (BNP) result from stimulation of the guanylyl-cyclase type A receptor. Chronic elevation causes hyporesponsiveness to ANP, whereas BNP effects tend to be preserved, implying an additional pathway of action. We, therefore, investigated the hemodynamic effects of co-infusion of ANP, BNP, and, as a positive control acting on type B receptor, C-type natriuretic peptide (CNP). Furthermore, vascular responses to short and prolonged infusions were compared to investigate rapid hyporesponsiveness of guanylyl-cyclase type A receptor. METHODS: In 11 healthy volunteers, arterial response to continuous intra-arterial infusion of ANP (60 pmol/100 mL forearm tissue volume [FAV]/min) was assessed by venous occlusion plethysmography. Then, co-infusion of a similar dose of ANP, BNP, or CNP was administered in randomized order. Each infusion phase was followed by a washout period. Then, ANP was restarted, followed by co-infusion of one of the natriuretic peptides not yet infused. After a further washout period, ANP was restarted, followed by co-infusion of the natriuretic peptide not yet co-infused. In 6 subjects, infusion time was adjusted to plasma half-lives (5 times), and in the other 5 subjects, infusion time was 5 minutes. RESULTS: ANP alone caused the expected vasodilation from 2.7 +/- 0.3 mL/min/100 mL FAV to 6.0 +/- 0.9 mL/min/100 mL FAV (P < .004). This response remained unchanged in the group that received short-term infusions (6.2 +/- 0.8 mL/min/100 mL FAV to 6.6 +/- 1.1 mL/min/100mL FAV) but was reduced over time in the group receiving longer-term infusions (6.5 +/- 1.2 mL/min/100 mL FAV to 4.5 +/- 0.7 mL/min/100mL FAV, P < .05; difference between groups P < .05). Co-infusions of ANP, BNP, and CNP caused minor additional vasodilation (mean 0.8 +/- 0.2 mL/min/100ml FAV, P < .01), which did not differ between the different co-infused natriuretic peptides. CONCLUSION: Our data provide evidence for rapid desensitization of the guanylyl-cyclase type A receptor in humans, but do not support the presence of a BNP-specific receptor.

Interaction of sildenafil with cAMP-mediated vasodilation in vivo.

Sildenafil inhibits cGMP breakdown by phosphodiesterase 5. In vitro, increased cGMP levels inhibit cAMP breakdown by phosphodiesterase 3. It is uncertain, however, whether sildenafil increases biological effects of interventions increasing cAMP levels in vivo. The objective of the present study in 40 healthy male volunteers was to determine the existence and extent of interactions with sildenafil and vasodilators acting via cGMP or cAMP or independently from these mediators on the arterial tone of the human forearm. Forearm blood flow (FBF) responses (plethysmography) to brachial artery infusions of 3 doses each of nitroglycerin, which increases cGMP levels; of isoprenaline and milrinone, which increase cAMP levels; and of verapamil as a control were assessed at baseline and 80 minutes after 50 mg oral sildenafil in 10 volunteers each. Sildenafil increased FBF (2.5+/-0.1 to 3.5+/-0.2 mL/min per 100 mL, P<0.001; n=40). At equipotent vasodilator dosages, sildenafil increased FBF from 7.5+/-1.0 to 9.8+/-1.2 mL/min per 100 mL for nitroglycerin, from 8.3+/-1.0 to 10.4+/-1.4 mL/min per 100 mL for isoprenaline, and from 8.1+/-1.0 to 10.3+/-1.2 mL/min per 100 mL for milrinone and slightly decreased FBF from 7.7+/-1.3 to 7.1+/-1.2 mL/min per 100 mL for verapamil. ANOVA for repeated measures revealed a significant interaction between sildenafil and the type of vasodilator on FBF (P<0.01). The responses of FBF to nitroglycerin, milrinone, and isoprenaline after sildenafil were similarly increased compared with the response to verapamil (P<0.01). Sildenafil markedly enhanced the arterial vasodilator response to nitroglycerin, milrinone, and isoprenaline. The response to milrinone and isoprenaline is compatible with an interaction between cGMP and phosphodiesterase 3 or an enhancement of the NO component of cAMP-mediated vasodilation, and raises the possibility of enhanced biological effects of interventions leading to increases of cAMP in the presence of sildenafil.