Antimicrobial use in pediatric oncology and hematology in Germany and Austria, 2020/2021: a cross-sectional, multi-center point-prevalence study with a multi-step qualitative adjudication process.

Background: Due to the high risk of severe infection among pediatric hematology and oncology patients, antimicrobial use is particularly high. With our study, we quantitatively and qualitatively evaluated, based on institutional standards and national guidelines, antimicrobial usage by employing a point-prevalence survey with a multi-step, expert panel approach. We analyzed reasons for inappropriate antimicrobial usage. Methods: This cross-sectional study was conducted at 30 pediatric hematology and oncology centers in 2020 and 2021. Centers affiliated to the German Society for Pediatric Oncology and Hematology were invited to join, and an existing institutional standard was a prerequisite to participate. We included hematologic/oncologic inpatients under 19 years old, who had a systemic antimicrobial treatment on the day of the point prevalence survey. In addition to a one-day, point-prevalence survey, external experts individually assessed the appropriateness of each therapy. This step was followed by an expert panel adjudication based upon the participating centers' institutional standards, as well as upon national guidelines. We analyzed antimicrobial prevalence rate, along with the rate of appropriate, inappropriate, and indeterminate antimicrobial therapies with regard to institutional and national guidelines. We compared the results of academic and non-academic centers, and performed a multinomial logistic regression using center- and patient-related data to identify variables that predict inappropriate therapy. Findings: At the time of the study, a total of 342 patients were hospitalized at 30 hospitals, of whom 320 were included for the calculation of the antimicrobial prevalence rate. The overall antimicrobial prevalence rate was 44.4% (142/320; range 11.1-78.6%) with a median antimicrobial prevalence rate per center of 44.5% (95% confidence interval [CI] 35.9-49.9). Antimicrobial prevalence rate was significantly higher (p < 0.001) at academic centers (median 50.0%; 95% CI 41.2-55.2) compared to non-academic centers (median 20.0%; 95% CI 11.0-32.4). After expert panel adjudication, 33.8% (48/142) of all therapies were labelled inappropriate based upon institutional standards, with a higher rate (47.9% [68/142]) when national guidelines were taken into consideration. The most frequent reasons for inappropriate therapy were incorrect dosage (26.2% [37/141]) and (de-)escalation/spectrum-related errors (20.6% [29/141]). Multinomial, logistic regression yielded the number of antimicrobial drugs (odds ratio, OR, 3.13, 95% CI 1.76-5.54, p < 0.001), the diagnosis febrile neutropenia (OR 0.18, 95% CI 0.06-0.51, p = 0.0015), and an existing pediatric antimicrobial stewardship program (OR 0.35, 95% CI 0.15-0.84, p = 0.019) as predictors of inappropriate therapy. Our analysis revealed no evidence of a difference between academic and non-academic centers regarding appropriate usage. Interpretation: Our study revealed there to be high levels of antimicrobial usage at German and Austrian pediatric oncology and hematology centers with a significant higher number at academic centers. Incorrect dosing was shown to be the most frequent reason for inappropriate usage. Diagnosis of febrile neutropenia and antimicrobial stewardship programs were associated with a lower likelihood of inappropriate therapy. These findings suggest the importance of febrile neutropenia guidelines and guidelines compliance, as well as the need for regular antibiotic stewardship counselling at pediatric oncology and hematology centers. Funding: European Society of Clinical Microbiology and Infectious Diseases, Deutsche Gesellschaft für Pädiatrische Infektiologie, Deutsche Gesellschaft für Krankenhaushygiene, Stiftung Kreissparkasse Saarbrücken.

Antimicrobial Use in Pediatric Oncology and Hematology: Protocol for a Multicenter Point-Prevalence Study With Qualitative Expert Panel Assessment.

BACKGROUND: Because infections are a major driver of morbidity and mortality in children with hematologic or oncologic diseases, antimicrobials are frequently prescribed in pediatric oncology practice. However, excess or inappropriate use of antimicrobials is directly linked to the emergence of antimicrobial resistance. Although point-prevalence studies have examined the extent of antimicrobial use, a comprehensive qualitative evaluation of individual antimicrobial prescriptions remains lacking. OBJECTIVE: The aim of this study is to identify appropriate versus inappropriate antimicrobial use among pediatric cancer patients in a point-prevalence study, followed by an expert panel adjudication process and a subsequent report of these findings to participating centers. This study also aims to improve the quality of patient care by informing centers about discrepancies between internal standards of care and national guidelines. METHODS: Our point-prevalence study is performed at pediatric cancer centers in Germany and Austria. All patients under 18 years old who are hospitalized at the time of the study are included. As a supplement to the point-prevalence study, an expert panel is qualitatively assessing each of the antimicrobial prescriptions at the participating centers to review local guidelines and compare them with national guidelines. RESULTS: As of December 2021, the point-prevalence survey has been conducted at 30 sites and expert panel adjudication for qualitative assessment of each antimicrobial use is ongoing. Results of the study are expected in 2022. CONCLUSIONS: This is the first point-prevalence study conducted among pediatric cancer centers with an integrated, multistep, qualitative approach that assesses each antimicrobial prescription. The results of this study will inform possible interventions for internal guidelines and antimicrobial stewardship programs implemented at pediatric cancer centers. In addition, local guidelines will be compared with national guidelines. Furthermore, this study will contribute to the overall integration of antimicrobial stewardship principles and initiatives in pediatric oncology and hematology, thereby improving safety and quality of care for children and adolescents with cancer and blood disorders. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/35774.

Non-Typhoidal Salmonella Infection in Children: Influence of Antibiotic Therapy on Postconvalescent Excretion and Clinical Course-A Systematic Review.

(1) Background: Although published recommendations are available, the use of antibiotics in non-typhoidal Salmonella (NTS) infections in children is still controversially debated in clinical practice. Patients might even be put at risk, with necessary antibiotic therapy being withheld due to the widespread concern of prolonged post-convalescent shedding. The authors conducted a systematic review to assess whether antibiotic treatment influences fecal excretion or the clinical course in children with NTS infection. (2) Methods: The review was carried out following the PRISMA guidelines. In a Medline database search, studies assessing the influence of antibiotic therapy on excretion and/or the clinical course of NTS infections were selected. Studies reporting on adults only were not considered. Out of 532 publications which were identified during the systematic literature search, 14 publications were finally included (3273 patients in total). Quality and bias assessment was performed using the Newcastle-Ottawa scale (NOS) or the Cochrane risk-of bias tool (ROB-2). (3) Results: Four early studies from decades ago demonstrated a prolongation of intestinal NTS excretion in children after antibiotic treatment, whereas most studies published more recently observed no significant influence, which might be due to having used more "modern" antibiotic regimes (n = 7 studies). Most studies did not describe significant differences regarding the severity and duration of symptoms between untreated patients and those treated with antibiotics. Quality and bias were mainly moderate (NOS) or variable (ROB-2), respectively. (4) Conclusions: There is no substantial evidence of prolonged excretion of NTS in pediatric patients after treatment with newer antimicrobials. Consequently, clinicians should not withhold antibiotics in NTS infection for children at risk, such as for very young children, children with comorbidities, and those with suspected invasive disease due to concerns about prolonged post-convalescent bacterial excretion. In the majority of cases with uncomplicated NTS diarrhea, clinicians should refrain from applying antibiotics.

Emergence of Macrolide-Resistant Mycoplasma pneumoniae during an Outbreak in a Primary School: Clinical Characterization of Hospitalized Children.

Mycoplasma pneumoniae (M. pneumoniae) is a common causative pathogen of community-acquired pneumonia. Here, we report the development of macrolide resistance during a school outbreak of severe M. pneumoniae infections in southwest Germany. We conducted a case series to assess the clinical and laboratory characteristics of hospitalized children with M. pneumonia infection and the prevalence of macrolide-resistant M. pneumoniae (MRMP) in this patient group. We retrospectively analyzed 23 children with serologically (19 patients) and/or PCR (eight patients) confirmed M. pneumoniae infection between October 2019 and December 2019. Most of the 15 hospitalized patients had lower respiratory tract infection (n = 10) and required oxygen therapy (83%). The median length of hospitalization was 7 days (range 3-10 days). In 8/15 patients (53.3%) azithromycin and in 4/15 (26.6%) clarithromycin treatment was applied. However, among the five patients for which extended molecular characterization was performed, sequencing of 23S rRNA revealed no mutation only in the first case, but development of macrolide resistance A2058G in four subsequent cases. Hence, we identified a cluster of hospitalized patients with emerging MRMP. Further studies are warranted to confirm a potential link between macrolide resistance and disease severity.

Expert panel diagnosis demonstrated high reproducibility as reference standard in infectious diseases.

OBJECTIVE: If a gold standard is lacking in a diagnostic test accuracy study, expert diagnosis is frequently used as reference standard. However, interobserver and intraobserver agreements are imperfect. The aim of this study was to quantify the reproducibility of a panel diagnosis for pediatric infectious diseases. STUDY DESIGN AND SETTING: Pediatricians from six countries adjudicated a diagnosis (i.e., bacterial infection, viral infection, or indeterminate) for febrile children. Diagnosis was reached when the majority of panel members came to the same diagnosis, leaving others inconclusive. We evaluated intraobserver and intrapanel agreement with 6 weeks and 3 years' time intervals. We calculated the proportion of inconclusive diagnosis for a three-, five-, and seven-expert panel. RESULTS: For both time intervals (i.e., 6 weeks and 3 years), intrapanel agreement was higher (kappa 0.88, 95%CI: 0.81-0.94 and 0.80, 95%CI: NA) compared to intraobserver agreement (kappa 0.77, 95%CI: 0.71-0.83 and 0.65, 95%CI: 0.52-0.78). After expanding the three-expert panel to five or seven experts, the proportion of inconclusive diagnoses (11%) remained the same. CONCLUSION: A panel consisting of three experts provides more reproducible diagnoses than an individual expert in children with lower respiratory tract infection or fever without source. Increasing the size of a panel beyond three experts has no major advantage for diagnosis reproducibility.

Human Norovirus Evolution in a Chronically Infected Host.

Typically, human noroviruses cause symptoms of acute gastroenteritis for 2 to 4 days. Often, the virions are shed in stool for several days after the symptoms recede, which in turn can lead to further contamination and transmission. Moreover, a number of reports have considered that chronic norovirus infections, i.e., lasting months and years, might even function as reservoirs for the generation of novel strains that can escape the herd immunity or have modified binding interactions with histo-blood group antigens (HBGAs). In this study, we analyzed noroviruses isolated from a patient who has presented a chronic infection for more than 6 years. We found that the isolated capsid sequences clustered into two main genetic types (termed A and B), despite a plethora of capsid quasi-sequences. Furthermore, the two genetic types corresponded well with distinct antigenicities. On the other hand, we showed that numerous amino acid substitutions on the capsid surface of genetic types A and B did not alter the HBGA binding profiles. However, divergent binding profiles for types A and B were observed with human milk oligosaccharides (HMOs), which structurally mimic HBGAs and may act as natural antivirals. Importantly, the isolated capsid sequences only had approximately 90% amino acid identity with other known sequences, which suggested that transmission of these chronic noroviruses could be limited. IMPORTANCE The norovirus genogroup II genotype 4 (GII.4) variants have approximately 5% divergence in capsid amino acid identity and have dominated over the past decade. The precise reason(s) for the GII.4 emergence and persistence in the human population is still unknown, but some studies have suggested that chronically infected patients might generate novel variants that can cause new epidemics. We examined GII.4 noroviruses isolated from an immunocompromised patient with a long-term infection. Numerous norovirus capsid quasi-species were isolated during the 13-month study. The capsid quasi-species clustered into two genetic and antigenic types. However, the HBGA binding profiles were similar between the two antigenic clusters, indicating that the amino acid substitutions did not alter the HBGA binding interactions. The isolated sequences represented two new GII.4 variants, but similar sequences were not found in the database. These results indicated that chronically infected patients might not generate novel noroviruses that cause outbreaks.

Prevalence of Multidrug-Resistant Organisms in Hospitalized Pediatric Refugees in an University Children's Hospital in Germany 2015-2016.

OBJECTIVE To determine the prevalence of multidrug-resistant organisms (MDROs) colonizing in pediatric refugees admitted to a University Children Hospital in Germany. DESIGN Retrospective observational study. SETTING General pediatric and pediatric surgery units. PATIENTS In Germany, recommendations for MDRO screening of pediatric refugees were recently published. According to these and institutional recommendations, all hospitalized pediatric refugees were screened for MDROs between October 2015 and March 2016. METHODS Using electronic surveillance data, we performed a chart review to identify the prevalence of MDROs among and the clinical diagnoses of pediatric refugees. RESULTS Among 325 patients hospitalized for various causes, most frequently gastroenteritis (30.9%), MDROs were detected in 33.8%. Most of these patients were colonized with multidrug-resistant Gram-negative (MRGN) bacteria (113 isolates), mostly 2MRGN/ESBL (87 isolates); some patients were colonized with methicillin-resistant Staphylococcus aureus (MRSA, 22 isolates); and 1 patient was colonized with vancomycin-resistant enterococci (VRE). Among 110 refugee patients, we detected single colonization with an MDRO in 84 patients (76.4%), co-colonization with 2 pathogens in 23 patients (20.9%), and triple colonization in 3 patients (2.7%). However, infections with MDROs occurred in only 3.6% of pediatric refugees. The peak of positive MDRO screening results in 2015 correlated with an increased hospitalization rate. CONCLUSION Implementation of infection control measures among pediatric refugees is challenging. Due to the high frequency of MDROs in these patients, current screening, isolation, and treatment strategies may have to be adapted. Infect Control Hosp Epidemiol 2016;1-5.

Structural Basis for Norovirus Inhibition by Human Milk Oligosaccharides.

Histo-blood group antigens (HBGAs) are important binding factors for norovirus infections. We show that two human milk oligosaccharides, 2'-fucosyllactose (2'FL) and 3-fucosyllactose (3FL), could block norovirus from binding to surrogate HBGA samples. We found that 2'FL and 3FL bound at the equivalent HBGA pockets on the norovirus capsid using X-ray crystallography. Our data revealed that 2'FL and 3FL structurally mimic HBGAs. These results suggest that 2'FL and 3FL might act as naturally occurring decoys in humans.

Anaphylaxis After Immunization of Children and Adolescents in Germany.

BACKGROUND: Anaphylaxis is a life-threatening event. The aim of this study was to estimate the annual frequency of anaphylaxis after immunization in individuals younger than 18 years in Germany leading to hospitalization. METHODS: All suspected cases of postvaccination anaphylaxis involving individuals aged 0-17 years reported to the German surveillance unit for rare pediatric diseases (Erhebungseinheit für seltene pädiatrische Erkrankungen in Deutschland) from June 2008 through May 2010, and all suspected cases of anaphylaxis as an adverse event following immunization in the same age group reported to the Paul-Ehrlich-Institut during the observational period were classified according to the Brighton collaboration case definition. Only hospitalized cases of anaphylaxis fulfilling Brighton collaboration case definition level 1-3 criteria were eligible. Estimates for the annual frequency were calculated by using capture-recapture methods. RESULTS: A total of 22 reports were eligible. Median age of the affected individuals (13 males, 9 females) was 7.0 years (range: 2 months to 17 years). Anaphylaxis occurred most frequently after administration of AS03 adjuvanted A/H1N1 pandemic influenza vaccine (n = 8). The annual frequency of anaphylaxis after vaccination (excluding pandemic influenza vaccine as well as monovalent measles and rubella vaccines) was estimated to be 6.8 (95% confidence interval: 6.1-10.9). The estimated incidence of anaphylaxis after administration of specific vaccines ranged from 0.4 to 127.6 cases per 1,000,000 doses administered. CONCLUSIONS: This study confirms that anaphylaxis after immunization in children and adolescents is a rare event. AS03 adjuvanted A/H1N1 pandemic influenza vaccine seems to be associated with a higher risk of anaphylaxis when compared with other vaccines.

Bioengineered 2'-fucosyllactose and 3-fucosyllactose inhibit the adhesion of Pseudomonas aeruginosa and enteric pathogens to human intestinal and respiratory cell lines.

Human milk oligosaccharides help to prevent infectious diseases in breastfed infants. Larger scale testing, particularly in animal models and human clinical studies, is still limited due to shortened availability of more complex oligosaccharides. The purpose of this study was to evaluate 2'-fucosyllactose (2'-FL) and 3-fucosyllactose (3-FL) synthesized by whole-cell biocatalysis for their biological activity in vitro. Therefore, we have tested these oligosaccharides for their inhibitory potential of pathogen adhesion in two different human epithelial cell lines. 2'-FL could inhibit adhesion of Campylobacter jejuni, enteropathogenic Escherichia coli, Salmonella enterica serovar fyris, and Pseudomonas aeruginosa to the intestinal human cell line Caco-2 (reduction of 26%, 18%, 12%, and 17%, respectively), as could be shown for 3-FL (enteropathogenic E coli 29%, P aeruginosa 26%). Furthermore, adherence of P aeruginosa to the human respiratory epithelial cell line A549 was significantly inhibited by 2'-FL and 3-FL (reduction of 24% and 23%, respectively). These results confirm the biological and functional activity of biotechnologically synthesized human milk oligosaccharides. Mass-tailored human milk oligosaccharides could be used in the future to supplement infant formula ingredients or as preventatives to reduce the impact of infectious diseases.

The role of prebiotics and probiotics in prevention and treatment of childhood infectious diseases.

Infant formulae and food products marketed for children have been increasingly supplemented with probiotics and/or prebiotics. A vast number of studies have accounted for the transit of probiotic use from alternative to more evidence-based medicine. Data support the use of certain probiotics for the adjunct treatment of acute viral gastroenteritis, and for prevention of gastrointestinal diseases. Further roles of prebiotics and probiotics are seen in the prevention of overall infectious diseases and respiratory infections. Data from well-conducted randomized-controlled trials support the therapeutic role for probiotics toward necrotizing enterocolitis in preterm infants. However, it is difficult to translate heterogeneous-based study results, which are mainly due to varying genera, strains, doses, study settings and measured outcomes, into evidence-based recommendations. This article focuses on the evidence of clinical benefits of prebiotics, probiotics and synbiotics toward prevention and treatment of pediatric infectious diseases.

Candidiasis caused by Candida kefyr in a neonate: case report.

BACKGROUND: Systemic Candidia infections are of major concern in neonates, especially in those with risk factors such as longer use of broad spectrum antibiotics. Recent studies showed that also term babies with underlying gastrointestinal or urinary tract abnormalities are much more prone to systemic Candida infection. We report a very rare case of candidiasis caused by Candida kefyr in a term neonate. CASE PRESENTATION: Renal agenesis on the left side was diagnosed antenatally and anal atresia postnatally. Moreover, a vesico-ureteral-reflux (VUR) grade V was detected by cystography. The first surgical procedure, creating a protective colostoma, was uneventful. Afterwards our patient developed urosepsis caused by Enterococcus faecalis and was treated with piperacillin. The child improved initially, but deteriorated again. A further urine analysis revealed Candida kefyr in a significant number. As antibiotic resistance data about this non-albicans Candida species are limited, we started liposomal amphotericin B (AMB), but later changed to fluconazole after receiving the antibiogram. Candiduria persisted and abdominal imaging showed a Candida pyelonephritis. Since high grade reflux was prevalent we instilled AMB into the child's bladder as a therapeutic approach. While undergoing surgery (creating a neo-rectum) a recto-vesical fistula could be shown and subsequently was resected. The child recovered completely under systemic fluconazole therapy over 3 months. CONCLUSIONS: Candidiasis is still of major concern in neonates with accompanying risk factors. As clinicians are confronted with an increasing number of non-albicans Candida species, knowledge about these pathogens and their sensitivities is of major importance.

Acute haematogenous osteomyelitis in children: is there any evidence for how long we should treat?

PURPOSE OF REVIEW: Despite diagnostic and therapeutic advances, acute haematogenous osteomyelitis in children continues to cause significant morbidity and disease burden. The molecular epidemiology of causal organisms has wide geographic variation, but regardless of cause children often require several weeks of inpatient parenteral antibiotic therapy. This review focuses on antibiotic treatment and length of antibiotic therapy. RECENT FINDINGS: Currently there is no international and little local consensus regarding the route or duration for antibiotic treatment of acute haematogenous osteomyelitis in children. Although there are encouraging data from review papers and case series, no randomized controlled trial has been conducted to show good evidence for shorter courses of parenteral antibiotic treatment. Prospective studies show effective treatment for a wide variety of antibiotic agents, but there are few comparative studies. Overall treatment for 4-6 weeks is considered standard therapy, but the laboratory or clinical parameters that would determine the decision to switch to oral therapy remain undefined. SUMMARY: Evidence-based data about the route and duration of intravenous antibiotic treatment for acute haematogenous osteomyelitis in children are still limited to observational and retrospective studies. A randomized controlled trial will provide much needed data.

Increased SR Ca2+ cycling contributes to improved contractile performance in SERCA2a-overexpressing transgenic rats.

OBJECTIVE: Heart failure is associated with reduced function of sarcoplasmic reticulum (SR) Ca2+-ATPase (SERCA2a) but increased function of sarcolemmal Na+/Ca2+ exchanger (NCX), leading to decreased SR Ca2+ content and loss of frequency-potentiation of contractile force. We reported that SERCA2a-overexpression in transgenic rat hearts (TG) results in improved contractility. However, it was not clear whether TG have improved contractility due to frequency-dependent improved SR Ca2+ handling. METHODS: Therefore, we characterized TG (n=35) vs. wild-type (WT) control rats (n=39) under physiological conditions (37 degrees C, stimulation rate <8 Hz). Twitch force, intracellular Ca2+ transients ([Ca2+]i), and SR Ca2+ content were measured in isolated muscles. The contribution of transsarcolemmal Ca2+ influx (I(Ca)) through L-type Ca2+ channels (LTCC) and reverse mode NCX (I(Na/Ca)) to Ca2+ cycling were studied in isolated myocytes. RESULTS: With increasing frequency, force increased in TG muscles by 168+/-35% (8 Hz; P<0.05) and SR Ca2+ content increased by maximally 118+/-31% (4 Hz; P<0.05). In WT, there was a flat force-frequency response without changes in SR Ca2+ content. Relaxation parameters of force and [Ca2+]i decay were accelerated at each frequency in TG vs. WT by approximately 10%. At prolonged rest intervals (<240 s), force and SR Ca2+ content increased significantly more in TG. Consequently, absolute SR Ca2+ content measured in myocytes was increased approximately 2-fold in TG. Transsarcolemmal Ca2+ fluxes estimated by I(Ca) (at 0 mV -10.2+/-1.1 vs. -16.9+/-1.3 pA/pF) and I(Na/Ca) (0.17+/-0.02 vs. 0.46+/-0.05 pA/pF) were decreased in TG vs. WT (P<0.05), whereas NCX and LTCC protein expression was only slightly reduced (P=n.s.). CONCLUSION: In summary, SERCA2a-overexpression improved contractility in a frequency-dependent way due to increased SR Ca2+ loading whereas transsarcolemmal Ca2+ fluxes were decreased.

Role of lipoteichoic acid in the phagocyte response to group B streptococcus.

Group B Streptococcus (GBS) cell walls potently activate phagocytes by a largely TLR2-independent mechanism. In contrast, the cell wall component lipoteichoic acid (LTA) from diverse Gram-positive bacterial species has been shown to engage TLR2. In this study we examined the role of LTA from GBS in phagocyte activation and the requirements for TLR-LTA interaction. Using cells from knockout mice and genetic complementation in epithelial cells we found that highly pure LTA from both GBS and Staphylococcus aureus interact with TLR2 and TLR6, but not TLR1, in contrast to previous reports. Furthermore, NF-kappaB activation by LTA required the integrity of two putative PI3K binding domains within TLR2 and was inhibited by wortmannin, indicating an essential role for PI3K in cellular activation by LTA. However, LTA from GBS proved to be a relatively weak stimulus of phagocytes containing approximately 20% of the activity observed with LTA from Staphylococcus aureus. Structural analysis by nuclear magnetic resonance spectrometry revealed important differences between LTA from GBS and S. aureus, specifically differences in glycosyl linkage, in the glycolipid anchor and a lack of N-acetylglucosamine substituents of the glycerophosphate backbone. Furthermore, GBS expressing LTA devoid of d-alanine residues, that are essential within immune activation by LTA, exhibited similar inflammatory potency as GBS with alanylated LTA. In conclusion, LTA from GBS is a TLR2/TLR6 ligand that might contribute to secreted GBS activity, but does not contribute significantly to GBS cell wall mediated macrophage activation.

The role of SR Ca(2+)-content in blunted inotropic responsiveness of failing human myocardium.

The effects of inotropic agents are blunted in end-stage failing human myocardium. This has been related to a number of subcellular alterations including desensitization of the beta -adrenergic system. However, it is unknown whether alterations in SR Ca(2+)-handling contribute to blunted inotropic responsiveness of failing myocardium. We tested the hypothesis that the reduced effectiveness of Ca(2+)-dependent inotropic interventions results from the inability of the SR to sufficiently increase its Ca(2+)-content in failing human myocardium. Experiments were performed in ventricular muscle preparations from a total of four non-failing and 18 end-stage failing hearts. Isometric twitch force and SR Ca(2+)-content (using rapid cooling contractures; RCCs) were assessed under basal experimental conditions (1 Hz, 37 degrees C, [Ca(2+)](o) 2.5 mmol/l), and at increasing [Ca(2+)](o) (1.25-15 mmol/l), increasing concentrations of the beta -adrenergic agonist isoproterenol (ISO; 0.01-10 micromol/l), or the glycolytic substrate pyruvate (5-15 mmol/l). In addition, paired RCCs were evoked in a subset of experiments to investigate the relative contribution of SR Ca(2+)-uptake v Na(+)/Ca(2+)-exchange to cytosolic Ca(2+)-elimination. In non-failing human myocardium, Ca(2+), ISO, and pyruvate exerted significant positive inotropic effects (increase in twitch force by maximally 396%, 437%, and 82%, respectively). The inotropic effects were associated with increasing RCCs (by 147%, 193%, and 51%, respectively). In failing myocardium, the inotropic effects of Ca(2+) and ISO were significantly less pronounced (with maximal increases in twitch force by 226% and 138%, respectively), associated with blunted effects on RCCs (increase by 33% and 79%, respectively). In contrast, the inotropic effect of pyruvate was unchanged in failing myocardium (increase by 66%), while the corresponding RCCs increased only by 30%. We conclude that the inotropic effects of Ca(2+), ISO, and pyruvate are associated with a significant increase in SR Ca(2+)-content in non-failing human myocardium. In end-stage failing myocardium, the reduced inotropic response to Ca(2+) and ISO is associated with the inability of the SR to appropriately increase its Ca(2+)-content, possibly related to decreased SR Ca(2+)-ATPase and increased Na(+)/Ca(2+)-exchanger expression. In contrast, the maintained inotropic response to pyruvate despite reduced SR Ca(2+)-loading points to additional subcellular effects such as enhanced myofilament Ca(2+)-responsiveness.