Microbiological diagnosis of severe diarrhea in kidney transplant recipients by use of multiplex PCR assays

Infectious Diarrhea in Kidney Transplant Recipients

Introduction Infectious diarrhea represents a significant and frequent complication among kidney transplant recipients, primarily due to the immunosuppressive therapy required to prevent graft rejection. This condition poses substantial risks to both graft function and patient survival, driven by increased susceptibility to opportunistic pathogens and potential medication-related gastrointestinal effects. This study aims to characterize the pathogen spectrum and associated risk factors of infectious diarrhea in a German cohort of kidney transplant recipients, providing insights into regional patterns and clinical implications. Methods A retrospective cohort study was conducted, analyzing 604 patients, including 436 kidney transplant recipients, who were hospitalized with infectious diarrhea (ICD-10 codes A00-A09) at the Universitätsklinikum Düsseldorf (UKD) between January 2019 and December 2023. Nontransplant patients (n = 168) were included as a comparison group to evaluate pathogen distribution and infection risk specific to immunosuppressive therapy in transplant recipients. Pathogen identification was performed focusing on stool samples. Data collected included transplantation status, dates of admission and transplantation, recurrence rates, and detailed immunosuppressive regimens. Statistical analyses were applied to evaluate pathogen distribution, temporal patterns, and the influence of immunosuppression on infection risk. Results The most prevalent pathogens identified among kidney transplant recipients were Clostridioides difficile (26.3%), cytomegalovirus (CMV, 12.3%), enteropathogenic Escherichia coli (EPEC, 8.6%), and norovirus (4.8%). Immunosuppression significantly heightened infection susceptibility, with Clostridioides difficile infections occurring notably more frequently and CMV-related diarrhea observed exclusively in the transplant cohort. Recurrence rates were elevated for both CMV and Clostridioides difficile, underscoring their clinical persistence. Temporal analysis revealed a median onset of CMV infections at approximately 13 months post-transplantation, with no significant seasonal variation. Conclusions The predominance of opportunistic pathogens such as Clostridioides difficile and CMV in kidney transplant recipients reflects the profound impact of immunosuppression on infection risk and pathogen profiles. These findings emphasize the necessity for enhanced diagnostic approaches in kidney transplant recipients, including early and comprehensive pathogen screening, and targeted prevention strategies, such as optimized and maybe prolonged CMV prophylaxis and stringent hygiene protocols for Clostridioides difficile. It emphasizes close monitoring of a potential viral load in blood samples, especially after cessation of the routine CMV prophylaxis after kidney transplantation. This study contributes to a better understanding of infectious diarrhea in this vulnerable population and lays the groundwork for improved clinical management, overall cost reduction, and future prospective research.

Development of RNA reference materials for norovirus GI and GII using digital PCR

Norovirus is a highly virulent pathogen that causes enteritis in all age groups worldwide. Owing to the diversity of noroviruses, the development of vaccines and treatments is challenging, and an early and accurate diagnosis is crucial. Reference materials (RMs) developed previously for norovirus genotypes I (GI) and II (GII) were quantified using reverse transcription quantitative PCR. In this study, we developed norovirus GI and GII RMs as in vitro transcribed RNA forms. These RMs were then assigned reference values for the RNA copy number concentration. The concentrations of GI and GII RMs determined using in-house reverse transcription digital PCR assays were (1.92±0.37)×107 and (1.20±0.27)×107 copy/mL, respectively. The homogeneity and stability of the RMs were evaluated, and their compatibility with commercial diagnostic kits was validated. These RMs can be used for the development of detection assays, as calibrants for various molecular measurement techniques, and as test materials for internal and external quality assurance.

A Systematic Literature Review to Determine Gaps in Diagnosing Suspected Infection in Solid Organ Transplant Recipients

Background

Improved diagnostic testing (DT) of infections may optimize outcomes for solid organ transplant recipients (SOTR), but a comprehensive analysis is lacking.

Methods

We conducted a systematic literature review across multiple databases, including EMBASE and MEDLINE(R), of studies published between 1 January 2012-11 June 2022, to examine the evidence behind DT in SOTR. Eligibility criteria included the use of conventional diagnostic methods (culture, biomarkers, directed-polymerase chain reaction [PCR]) or advanced molecular diagnostics (broad-range PCR, metagenomics) to diagnose infections in hospitalized SOTR. Bias was assessed using tools such as the Cochrane Handbook and PRISMA 2020.

Results

Of 2362 studies, 72 were eligible and evaluated heterogeneous SOT populations, infections, biospecimens, DT, and outcomes. All studies exhibited bias, mainly in reporting quality. Median study sample size was 102 (range, 11-1307). Culture was the most common DT studied (N = 45 studies, 62.5%), with positive results in a median of 27.7% (range, 0%-88.3%). Biomarkers, PCR, and metagenomics were evaluated in 7, 19, and 3 studies, respectively; only 6 reported sensitivity, specificity, and positive/negative predictive values. Directed-PCR performed well for targeted pathogens, but only 1 study evaluated broad-range PCR. Metagenomics approaches detected numerous organisms but required clinical adjudication, with too few studies (N = 3) to draw conclusions. Turnaround time was shorter for PCR/metagenomics than conventional diagnostic methods (N = 4 studies, 5.6%). Only 6 studies reported the impact of DT on outcomes like antimicrobial use and length of stay.

Conclusions

We identified considerable evidence gaps in infection-related DT among SOT, particularly molecular DT, highlighting the need for further research.

Enteric Pathogen Detection Using Multiplex PCR Assay in Kidney Transplant Recipients with Diarrhea-Retrospective Before-After Study

INTRODUCTION

Diarrhea is a frequent complication after kidney transplantation, however the etiology is often not identified. Multiplex PCR assays may increase the detection of diarrheal pathogens among kidney transplant recipients (KTRs), leading to improved management.

METHODS

This was a retrospective before-after study, conducted in a high-volume transplant center. In September 2017, multiplex PCR assay was introduced. We reviewed all hospitalized KTRs with diarrhea during 1/2015-8/2017 (pre-GI PCR, n = 111) and 9/2017-12/2021 (GI PCR, n = 159) and followed them for 3 years. We performed univariate and multivariate analysis for predictors of pathogen identification, introducing the study period as an independent variable.

RESULTS

Among 270 hospitalized KTRs with diarrhea, 64 (24%) had an identified diarrheal pathogen. The proportion of KTRs with an identified pathogen increased from 20% (13/64) in the pre-GI PCR to 80% (51/64) post GI PCR (p < 0.01). Of 51 KTRs with an identified pathogen in the post GI PCR, 44 (86%) were diagnosed using GI PCR. GI PCR was more likely used in younger KTRs with more recent transplantation and higher creatinine level at admission. The most common non-C. difficile diarrheal pathogens in the post-GI PCR cohort were enteropathogenic Escherichia coli (n = 23, 58%), norovirus (n = 11, 28%), and Campylobacter (n = 11, 28%). Implementing GI PCR significantly increased the detection and identification of GI pathogens (odds ratio [OR] = 21, CI 95% 10-44; p < 0.001).

CONCLUSIONS

Infectious etiologies of diarrhea were identified in a higher proportion of KTRs after the implementation of GI PCR. This emphasizes the importance of integrating this diagnostic tool into diarrhea workup in KTRs.

Diagnostic performance of a multiplexed gastrointestinal PCR panel for identifying diarrheal pathogens in children undergoing hematopoietic stem cell transplant

BACKGROUND

Diarrhea is a common complication of hematopoietic stem cell transplantation (HSCT) and is associated with substantial morbidity, but its etiology is often unknown. Etiologies of diarrhea in this population include infectious causes, chemotherapy- or medication-induced mucosal injury and graft-versus-host disease (GVHD). Distinguishing these potential causes of diarrhea is challenging since diarrheal symptoms are often multifactorial, and the etiologies often overlap in transplant patients. The objectives of this study were to evaluate whether the FilmArray gastrointestinal (GI) panel would increase diagnostic yield and the degree to which pre-transplantation colonization predicts post-transplantation infection.

METHODS

From November 2019 to February 2021, a total of 158 patients undergoing HSCT were prospectively included in the study. Stool specimens were obtained from all HSCT recipients prior to conditioning therapy, 28 ± 7 days after transplantation and at any new episode of diarrhea. All stool samples were tested by the FilmArray GI panel and other clinical microbiological assays.

RESULTS

The primary cause of post-transplantation diarrhea was infection (57/84, 67.86%), followed by medication (38/84, 45.24%) and GVHD (21/84, 25.00%). Ninety-five of 158 patients were colonized with at least one gastrointestinal pathogen before conditioning therapy, and the incidence of infectious diarrhea was significantly higher in colonized patients (47/95, 49.47%) than in non-colonized patients (10/63, 15.87%) (P < 0.001). Fourteen of 19 (73.68%) patients who were initially colonized with norovirus pre-transplantation developed a post-transplantation norovirus infection. Twenty-four of 62 (38.71%) patients colonized with Clostridium difficile developed a diarrheal infection. In addition, FilmArray GI panel testing improved the diagnostic yield by almost twofold in our study (55/92, 59.78% vs. 30/92, 32.61%).

CONCLUSIONS

Our data show that more than half of pediatric patients who were admitted for HSCT were colonized with various gastrointestinal pathogens, and more than one-third of these pathogens were associated with post-transplantation diarrhea. In addition, the FilmArray GI panel can increase the detection rate of diarrheal pathogens in pediatric HSCT patients, but the panel needs to be optimized for pathogen species, and further studies assessing its clinical impact and cost-effectiveness in this specific patient population are also needed.

Epidemiology of Campylobacter Species Infection in Kidney Transplant Recipients: A Retrospective Multicentric Case-Control Study in France

Background

Campylobacteriosis in kidney transplant recipients (KTRs) is the most common identified bacterial cause of diarrhea. Risk factors in KTRs are unknown.

Methods

A 10-year multicentric, retrospective 1:1 case-control study was performed in France between 2010 and 2020. The main aim was to identify factors associated with Campylobacter-related infection in KTRs. The KTRs with a functional graft and campylobacteriosis (positive stool culture and/or blood culture and/or positive nucleic amplification test) and their controls matched on transplantation date within the same center were included.

Results

We identified 326 patients with campylobacteriosis. The estimated incidence rate of campylobacteriosis was 2.3/1000 patient-years. The infection occurred at a median of 2.4 years posttransplantation. The independent risk factors for campylobacteriosis were use of corticosteroids as maintenance regimen (75.8% vs 66%; P < .001), acute rejection (8.9% vs 4%; P = .048), low lymphocyte count (0.96 vs 1.4 giga/liter (G/L); P < .001), and low basal estimated glomerular filtration rate (eGFR) (44.2 vs 57.5 mL/minute/1.73 m2; P < .001). A fluoroquinolone was initiated in 64 (21.4%) patients, with 51.1% of antimicrobial resistance, whereas almost all strains were erythromycin sensitive.

Conclusions

Campylobacteriosis has a higher incidence in the 2 first years of transplantation. The factors independently associated with campylobacteriosis are corticosteroids as maintenance immunosuppressive regimen, low lymphocyte counts, low eGFR, and a history of acute rejection. Due to high antimicrobial resistance with fluoroquinolone, the first line of treatment should be azithromycin.

Evaluation of non-invasive diagnostic tools for diarrhea: a systematic review of point-of-care tests and biomarkers

Background

Diarrhea is a prevalent condition affecting millions worldwide. However, current standard diagnostic methods have many drawbacks. This review examines various non-invasive point-of-care (POC) tests and biomarkers aiding rapid diagnosis of diarrhea from different causes.

Methods

PubMed, PubMed Central, ScienceDirect, Cochrane Library, and Google Scholar were searched from 2013 to present for relevant literature. Two reviewers independently assessed included studies' quality using the Critical Appraisal Skills Programme (CASP) checklist.

Results

The search yielded 1453 studies, of which 39 were included after screening and applying eligibility criteria. Polymerase chain reaction (PCR) was the POC test in 25 studies, providing consistent sensitivity and specificity. For biomarkers, C-reactive protein (CRP), fecal calprotectin, and procalcitonin offered high sensitivity and specificity for conditions like acute pediatric diarrhea, microscopic colitis, and inflammatory diarrhea, respectively.

Conclusion

PCR proved the ideal POC test for rapid diarrhea diagnosis, while the procalcitonin biomarker helps differentiate inflammatory from non-inflammatory diarrhea. Other reviewed tools also demonstrated promising diagnostic performance, though improvements in sensitivity, specificity, and usability are still needed.

Diarrhea after kidney transplantation: A study of risk factors and outcomes

Background

Diarrhea in kidney transplant recipients (KTRs) can be associated with significant morbidity.

Material and Methods

We evaluated 198 KTRs for a history of diarrhea post-kidney transplant at a tertiary care center in western India over 1 year. A protocol-based evaluation of diarrhea was done with respect to clinical features, diagnostic evaluation, associated acute allograft dysfunction, and its impact on long-term allograft function. Primary outcomes of interest were: chronic allograft injury (CAI) and the need for mycophenolate mofetil (MMF) withdrawal. We also assessed the effect of MMF withdrawal on the risk of the development of CAI.

Results

Eighty-five of 198 (42.5%) recipients experienced diarrhea and a total of 140 diarrheal episodes were evaluated. The mean age of these 85 recipients was 38 ± 12 years and 72 (84.7%) were males. 73 of 85 recipients were on MMF at the time of diarrhea and in 35 (48%) of them MMF withdrawal was needed for chronic and persistent symptoms. Diarrhea was attributed to infective etiologies in 90 of 140 (64.2%) cases. Among the microbiologically confirmed infective diarrheal episodes, giardia and cryptosporidium were the common pathogens in 11/28 (39%) and 6/28 (21.4%) episodes respectively. One hundred and twenty-eight episodes out of 140 (91.4%) episodes were complicated by acute allograft dysfunction. Forty-one of 85 recipients (48.2%) developed chronic allograft injury and 12 (14.1%) developed allograft rejection (acute and/or chronic). Probability of chronic allograft injury was higher in those with MMF withdrawal.

Conclusion

Diarrhea post-kidney transplant adversely affects graft function, especially after MMF withdrawal.

Reduced infant rhesus macaque growth rates due to environmental enteric dysfunction and association with histopathology in the large intestine

Environmental enteric dysfunction is associated with malnutrition as well as infant growth stunting and has been classically defined by villous blunting, decreased crypt-to-villus ratio, and inflammation in the small intestine. Here, we characterized environmental enteric dysfunction among infant rhesus macaques that are naturally exposed to enteric pathogens commonly linked to human growth stunting. Remarkably, despite villous atrophy and histological abnormalities observed in the small intestine, poor growth trajectories and low serum tryptophan levels were correlated with increased histopathology in the large intestine. This work provides insight into the mechanisms underlying this disease and indicates that the large intestine may be an important target for therapeutic intervention.

Environmental enteric dysfunction (EED), a subclinical disorder of intestinal function, is associated with malnutrition, infant growth stunting and pathologies in the small intestine. Here the authors report that infant rhesus macaques that are naturally exposed to enteric pathogens commonly linked to human growth stunting present with EED and growth faltering that associates with large intestine pathologies.

Epidemiology and outcomes of medically attended and microbiologically confirmed bacterial foodborne infections in solid organ transplant recipients

Food-safety measures are recommended to solid organ transplant (SOT) recipients. However, the burden of foodborne infections in SOT recipients has not been established. We describe the epidemiology and outcomes of bacterial foodborne infections in a nationwide cohort including 4405 SOT recipients in Switzerland between 2008 and 2018. Participants were prospectively followed for a median of 4.2 years with systematic collection of data on infections, and patient and graft-related outcomes. We identified 151 episodes of microbiologically confirmed bacterial foodborne infections occurring in median 1.6 years (IQR 0.58-3.40) after transplantation (131 [88%] Campylobacter spp. and 15 [10%] non-typhoidal Salmonella). The cumulative incidence of bacterial foodborne infections was 4% (95% CI 3.4-4.8). Standardized incidence rates were 7.4 (95% CI 6.2-8.7) and 4.6 (95% CI 2.6-7.5) for Campylobacter and Salmonella infections, respectively. Invasive infection was more common with Salmonella (33.3% [5/15]) compared to Campylobacter (3.2% [4/125]; p = .001). Hospital and ICU admission rates were 47.7% (69/145) and 4.1% (6/145), respectively. A composite endpoint of acute rejection, graft loss, or death occurred within 30 days in 3.3% (5/151) of cases. In conclusion, in our cohort bacterial foodborne infections were late post-transplant infections and were associated with significant morbidity, supporting the need for implementation of food-safety recommendations.

Review of the role of gastrointestinal multiplex polymerase chain reaction in the management of diarrheal illness

Acute and chronic diarrheal illness secondary to gastrointestinal infection is a significant cause of morbidity and mortality around the world. A cornerstone of management includes prompt diagnosis and appropriate treatment of culprit pathogens. Timely diagnosis can improve patient care, assist in infection control, and prevent disease outbreaks. Historical methods of diagnosis include traditional culture methods and stool analysis. These are limited by long turnaround time and inability to simultaneously assess multiple pathogens. The advent of multiplexed nucleic acid amplification tests first began with the Food and Drug Administration-approved respiratory virus multiplex polymerase chain reaction (PCR) panel in 2009, followed by gastrointestinal infections in 2013, and neurological infections in 2014. We conducted a review of current literature pertaining to the clinical utility of a gastrointestinal multiplex PCR in management of acute and chronic diarrhea in patients. To date, seven platforms approved by the US Food and Drug Administration are used in detection of various bacterial, viral, and parasitic causative organisms for diagnosis of gastrointestinal infections. The sensitivity and specificity of each assay vary depending on the tested organism. Interpretation of a positive result has to be tailored to the clinical context. Further studies are required to establish the utility of gastrointestinal multiplex PCR from a cost-based perspective, whether specific enteropathogens such as Clostridioides difficile are better assessed with toxin gene detection and whether new parameters such as cycle threshold values can improve clinical application of test results.

Diarrhea in pediatric recipients of solid organ or bone marrow transplants

Diarrhea is common in adults after solid organ transplantation (SOT) and bone marrow transplantation (BMT), but data in children are limited. Therefore, we aimed to determine the incidence and etiology of pediatric early-onset diarrhea in post SOT and BMT.We reviewed children aged 6 months to 18 years who underwent liver transplantation, kidney transplantation or BMT between January 2015 and December 2019 with duration of diarrhea > 72 hours within the first 6 months after transplantation. Clinical data and diarrheal course were collected. Regression analyses were performed to define factors associated with the interested outcomes.Among 252 transplanted patients, 168 patients (66.6%) had 289 documented episodes of diarrhea. A diagnosis of 68.2% of post-transplant diarrhea remained 'indefinite'. Enteric infection in SOT and gastrointestinal acute graft-versus-host disease (GI-aGVHD) in BMT were the commonly identified etiologies. Among 182 episodes among BMT children, skin rash was more pronounced when compared the ones with diarrhea > 7 days vs ≤ 7 days (odds ratio [OR] 13.9; 95% CI 1.8, 107.6). Males were more likely to develop GI-aGVHD as compared to females (OR 8.9). We found that GI-aGVHD was more common in the ones with skin rash and the presence of white blood cells in stool examination (OR 8.4 and 3.1, respectively). Deaths occurred in 7.7%.Two-thirds of post-transplant children experienced at least one episode of early-onset diarrhea, of which the etiology mainly remains undefined. Various clinical factors of prolonged/chronic diarrhea and GI-aGVHD may help clinicians when managing these children.

Epidemiological and clinical study of microsporidiosis in French kidney transplant recipients from 2005 to 2019: TRANS-SPORE registry

INTRODUCTION

Microsporidiosis is an emerging opportunistic infection in renal transplantation (RT) recipients. We aimed to describe its clinical presentation and treatment.

MATERIALS AND METHODS

We collected microsporidiosis cases identified in RT recipients between 2005 and 2019 in six French centers from the Crystal, Divat and Astre prospective databases.

RESULTS

We report 68 RT recipients with intestinal microsporidiosis; the patients were predominantly male (61.8%), with a median age of 58 (46-69) years. Infection occurred at a median time of 3 (0.8-6.8) years posttransplant. Only Enterocytozoon bieneusi was found. Microsporidiosis manifested as diarrhea (98.5% of patients) with weight loss (72.1%) and acute renal injury (57.4%) without inflammatory biological parameters. The therapeutic approaches were no treatment (N = 9), reduction of the immunosuppressive regimen (∆IS) (N = 22), fumagillin alone (N = 9), fumagillin and ∆IS (N = 19), and albendazole or nitazoxanide and ∆IS (N = 9). Overall clinical remission was observed in 60 patients (88.2%). We observed no acute kidney rejection, renal transplant failure, or death within 6 months after microsporidiosis.

CONCLUSION

E. bieneusi is an underestimated opportunistic pathogen in RT recipients, and infection with E. bieneusi leads to diarrhea with important dehydration and acute renal injury. The treatment is based on the reduction of the immunosuppressive regimen and the administration of fumagillin if available.

Infectious Gastroenteritis in Transplant Patients

Infectious gastroenteritis is common after transplantation and can lead to increased morbidity and mortality. A wide range of organisms can lead to gastroenteritis in this patient population. Clostridioides difficile, cytomegalovirus, and norovirus are the most common pathogens. Newer diagnostic methods, especially multiplex polymerase chain reaction, have increased the diagnostic yield of infectious etiologies. In this review, we describe the epidemiology and risk factors for common infectious pathogens leading to gastroenteritis.

Clinical characteristics, risk factors and outcome of severe Norovirus infection in kidney transplant patients: a case-control study

Background

Human Norovirus (HuNoV) has recently been identified as a major cause of diarrhea among kidney transplant recipients (KTR). Data regarding risk factors associated with the occurrence of HuNoV infection, and its long-term impact on kidney function are lacking.

Methods

We conducted a retrospective case-control study including all KTR with a diagnosis of HuNoV diarrhea. Each case was matched to a single control according to age and date of transplantation, randomly selected among our KTR cohort and who did not develop HuNoV infection. Risk factors associated with HuNoV infection were identified using conditional logistic regression, and survival was estimated using Kaplan-Meier estimator.

Results

From January 2012 to April 2018, 72 cases of NoV diarrhea were identified among 985 new KT, leading to a prevalence of HuNoV infection of 7.3%. Median time between kidney transplantation and diagnosis was 46.5 months (Inter Quartile Range [IQR]:17.8–81.5), and the median duration of symptoms 40 days (IQR: 15–66.2). Following diagnosis, 93% of the cases had a reduction of immunosuppression. During follow-up, de novo Donor Specific Antibody (DSA) were observed in 8 (9%) cases but none of the controls (p = 0.01). Acute rejection episodes were significantly more frequent among cases (13.8% versus 4.2% in controls; p = 0,03), but there was no difference in serum creatinine level at last follow-up between the two groups (p = 0.08). Pre-transplant diabetes and lymphopenia below 1000/mm³ were identified as risks factors for HuNoV infection in multivariate analysis.

Conclusion

HuNoV infection is a late-onset and prolonged infection among KTR. The current management, based on the reduction of immunosuppressive treatment, is responsible for the appearance of de novo DSA and an increase in acute rejection episodes.

MOL-PCR and xMAP Technology: A Multiplex System for Fast Detection of Food- and Waterborne Viruses

Viruses are common causes of food- and waterborne diseases worldwide. Conventional identification of these agents is based on cultivation, antigen detection, electron microscopy, or real-time PCR. Because recent technological advancements in detection methods are focused on fast and robust analysis, a rapid multiplexing technology, which can detect a broad spectrum of pathogenic viruses connected to food or water contamination, was utilized. A new semiquantitative magnetic bead-based multiplex system has been designed for simultaneous detection of several targets in one reaction. The system includes adenoviruses 40/41 (AdV), rotavirus A (RVA), norovirus (NoV), hepatitis E virus (HEV), hepatitis A virus (HAV), and a target for external control of the system. To evaluate the detection system, interlaboratory ring tests were performed in four independent laboratories. Analytical specificity of the tool was tested on a cohort of pathogenic agents and biological samples with quantitative PCR as a reference method. Limit of detection (analytical sensitivity) of 5 × 10⁰ (AdV, HEV, and RVA) and 5 × 10¹ (HAV and NoV) genome equivalents per reaction was reached. This robust, senstivie, and rapid multiplexing technology may be used to routinely monitor and manage viruses in food and water to prevent food and waterborne diseases.

Diarrhea in the pediatric solid organ transplantation recipient: A multidisciplinary approach to diagnosis and management

Diarrhea in the pediatric solid organ transplantation (SOT) recipient is a frequent complaint that is associated with significant morbidity and impaired quality of life. There are limited published data regarding the specific epidemiology, diagnostic evaluation, and treatment of diarrhea after SOT in children. Pediatric SOT recipients have an increased risk of developing diarrhea because of a generalized immunosuppressed state, epidemiologic exposures, and polypharmacy. There is a need to standardize the diagnostic evaluation of diarrhea in children after SOT to facilitate an accurate diagnosis and timely treatment. Herein, we review the available published data and propose a systematic, stepwise approach to the evaluation of diarrhea in this high-risk population, focusing on timely diagnosis of both infectious and non-infectious causes, in order to provide focused management. Prospective studies are needed to better assess the true prevalence, risk factors for, etiologies, and complications of diarrhea in pediatric SOT patients that will guide optimal management. Development of effective vaccines and antiviral therapies for enteric viruses may also contribute to improved outcomes.

Etiological profile of diarrhea in solid organ transplant recipients at a tertiary care center in Southern India

BACKGROUND

Diarrhea is one of the common gastrointestinal (GI) adverse events after solid organ transplantation. Diarrhea may be caused by infectious or non-infectious etiology. The infectious etiology of diarrhea varies according to the location and duration of diarrhea. Non-infectious etiologies include drugs, inflammatory bowel disease, neoplasia. The objective of this study was to evaluate the etiological profile of diarrhea in solid organ transplant recipients presenting to a tertiary care center in Southern India.

METHODS

This was a retrospective analysis of prospectively collected data of all solid organ transplantation recipients referred to the Department of Medical Gastroenterology for evaluation of diarrhea from April 2012 till May 2014. All patients had stool evaluated by wet mount examination, modified acid fast (AFB) stain, trichrome stain, culture, and Clostridium difficile toxin assay. EDTA plasma was collected for quantitative Cytomegalovirus (CMV) detection by real-time PCR. If the diarrhea was acute (<2 wk), and no etiological agent was identified, empirical antibiotic therapy was instituted and followed up. If persistent or chronic diarrhea (>2-4 wk), endoscopic evaluation (upper GI endoscopy and/or colonoscopy with biopsies), depending on the clinical type of diarrhea was done. If no specific etiological diagnosis was established after endoscopic evaluation, breath test for SIBO and celiac serology were done. If no specific etiology was identified after the above investigations, dose of immunosuppressive drugs was reduced. If diarrhea responded to dose reduction, it was considered to be drug related.

RESULTS

Fifty-eight episodes of diarrhea occurred in 55 solid organ transplant recipients during the study period. Renal transplant recipients constituted the majority (70%). Most (79%) of patients included in the study had their transplant > 6 mo ago. Infective diarrhea was the etiology in 46%, drug-related diarrhea in 29.3%. No specific etiology was identified in 22.4% of patients. Parasites accounted for 69% of all infective diarrhea. Stool evaluation was the main investigation in establishing diagnosis in acute diarrhea. Endoscopic evaluation was required in two thirds of patients to establish diagnosis in chronic diarrhea.

CONCLUSION

GI infections and drug-related diarrhea were the common causes of diarrhea in solid organ transplant recipients. Parasites were the most common infectious etiology of diarrhea. Step-wise evaluation was able to identify the etiology in ~ 77% of patients. Overall, 98% of diarrheal episodes resolved.

Etiological Spectrum of Infective Diarrhea in Renal Transplant Patient by Stool PCR: An Indian Perspective

Introduction:

Diarrhea is a common cause of morbidity and mortality among renal transplant patients. The etiological spectrum of pathogens varies with regional diversity, socioeconomic conditions, sanitation, and eating habits. We aimed to delineate the etiological profile of gastrointestinal pathogens in renal transplant patients using the stool Polymerase chain reaction.

Methods:

In this single-center, retrospective analysis of patients from January 2016 to January 2018, all renal transplant patients who were admitted with severe diarrhea and underwent the stool Polymerase chain reaction (PCR) were included. In the control group, we included patients from the general population who were admitted with similar complaints in the general medicine ward and underwent stool PCR over the same duration.

Results:

One hundred ten admissions occurred over 2 years in the transplant group. 86% of samples were positive for infection. More than one organism was seen in 68% of the patient. Norovirus was the most common organism isolated. Giardia lamblia with Norovirus was the most common coinfection among the transplant population. In the control group, 87% of samples tested positive, with 53% of patients having more than one organism. Enteroaggregative E. coli was the common organism, Enteroaggregative E. coli with Enteropathogenic E. coli and Enterotoxigenic E. coli were the most common organism in combination. Both the groups had similar incidence of infection with multiple organisms.

Conclusion:

The etiological profile of gastrointestinal pathogens differs significantly between the transplant and general population. Coinfections are common in both populations. Norovirus is the most common pathogen in the transplant population, presenting as isolated as well as in coinfections.

Emerging Microbiology Diagnostics for Transplant Infections: On the Cusp of a Paradigm Shift

In light of the heightened risk for infection associated with solid organ and hematopoietic stem cell transplantation, rapid and accurate microbiology diagnostics are essential to the practice of transplant clinicians, including infectious diseases specialists. In the last decade, diagnostic microbiology has seen a shift toward culture-independent techniques including single-target and multiplexed molecular testing, mass-spectrometry, and magnetic resonance-based methods which have together greatly expanded the array of pathogens identified, increased processing speed and throughput, allowed for detection of resistance determinants, and ultimately improved the outcomes of infected transplant recipients. More recently, a newer generation of diagnostics with immense potential has emerged, including multiplexed molecular panels directly applicable to blood and blood culture specimens, next-generation metagenomics, and gas chromatography mass spectrometry. Though these methods have some recognized drawbacks, many have already demonstrated improved sensitivity and a positive impact on clinical outcomes in transplant and immunocompromised patients.

Newer approaches in diagnosis of diarrhea in immunocompromised patients

PURPOSE OF REVIEW

This review will focus on the epidemiology and cause of diarrheal illness in solid organ transplant and stem-cell transplant population recipients with a specific focus on the role of advanced multiplex technology in the diagnosis of diarrhea within this patient population.

RECENT FINDINGS

A wide range of infectious and noninfectious causes of diarrhea have been described in immunocompromised patients. The most common infections noted are Clostridioides difficile, norovirus, and cytomegalovirus, whereas immunosuppressive drugs and mucositis are the most common noninfectious causes of diarrhea. Historically, diagnostic evaluation has been limited to an array of single pathogen assays. Newer multiplex assays have become available that allow rapid, sensitive detection of a wide range of pathogens in a single assay. These assays have improved the number of patients with a diagnosed pathogen but may identify colonizing pathogens that are not pathogenic. Studies are needed to inform the discrimination and optimal use of these newer assays.

SUMMARY

Diarrhea is a common complication in immunocompromised patients and is associated with greater morbidity and rare mortality. New diagnostics facilitate detection of recognized pathogens and may allow for improved outcomes through the use of pathogen-targeted therapy.

Diagnostic Test Accuracy of Commercial Tests for Detection of Shiga Toxin-Producing Escherichia coli: A Systematic Review and Meta-Analysis

BACKGROUND

Rapid detection of Shiga toxin-producing Escherichia coli (STEC) enables appropriate monitoring and treatment. We synthesized available evidence to compare the performance of enzyme immunoassay (EIA) and PCR tests for the detection of STEC.

METHODS

We searched published and gray literature for studies of STEC EIA and/or PCR diagnostic test accuracy relative to reference standards including at least one nucleic acid amplification test. Two reviewers independently screened studies, extracted data, and assessed quality with the second version of the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. Bivariate random effects models were used to meta-analyze the clinical sensitivity and specificity of commercial EIA and PCR STEC diagnostic tests, and summary receiver operator characteristic curves were constructed. We evaluated the certainty of evidence with the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

RESULTS

We identified 43 articles reflecting 25 260 specimens. Meta-analysis of EIA and PCR accuracy included 25 and 22 articles, respectively. STEC EIA pooled sensitivity and specificity were 0.681 (95% CI, 0.571-0.773; very low certainty of evidence) and 1.00 (95% CI, 0.998-1.00; moderate certainty of evidence), respectively. STEC PCR pooled sensitivity and specificity were 1.00 (95% CI, 0.904-1.00; low certainty of evidence) and 0.999 (95% CI, 0.997-0.999; low certainty of evidence), respectively. Certainty of evidence was downgraded because of high risk of bias.

CONCLUSIONS

PCR tests to identify the presence of STEC are more sensitive than EIA tests, with no meaningful loss of specificity. However, given the low certainty of evidence, our results may overestimate the difference in performance.

Real-life food-safety behavior and incidence of foodborne infections in solid organ transplant recipients

Food-safety measures are recommended in solid organ transplant (SOT) recipients. However, the actual adherence of patients in a real-life setting and the impact on the incidence of foodborne infections remain largely unexplored. We performed a survey among SOT recipients followed at our institution, aiming to evaluate their food-safety behavior. We assessed the incidence of microbiologically proven foodborne infections by chart review. One hundred ninety-seven SOT recipients (kidney = 117, lung = 35, liver = 29, and heart = 16) participated in the survey. Overall, 17.7% of the participants observed all food-safety recommendations (22.0% avoided food at risk of contamination while 67.9% applied hygiene recommendations). Patients within the first year after transplantation (odds ratio [OR] 5.42; P = .001) and females (OR 4.67; P = .001) followed food-safety recommendations more closely. Although the majority of SOT recipients felt concerned and actively sought information on food safety (68%-70%), only 27% were able to recognize all risks of foodborne infection in hypothetical scenarios. Incidence of proven foodborne infections was 17.9% (95% confidence interval 9.9%-30.9%) 5 years after transplantation. Importantly, foodborne infections occurred exclusively among patients not following food-safety recommendations. In summary, most SOT recipients eat foods that make them at risk of foodborne infections. Our results indicate that there is room for improvement in patient education, particularly later after transplantation, and reinforce current food-safety recommendations.

Recurring Norovirus & Sapovirus Infection in a Renal Transplant Patient

Noroviruses and sapoviruses are common causes of gastroenteritis and infectious diarrhea. Although these viruses are typically of short duration in healthy individuals, immunocompromised organ transplant recipients can develop chronic, relapsing symptoms with grave outcomes. We discuss a unique case of chronic norovirus infection with subsequent sapovirus infection in a kidney transplant recipient. Relief of norovirus symptoms occurred after the reduction of immunosuppression and treatment with nitazoxanide. Subsequently, a superimposed sapovirus infection developed. Patient developed renal transplant rejection due to reduction of immunosuppression. Findings from this case study suggest that norovirus and sapovirus are associated with chronic, relapsing symptoms and significant morbidity in immunocompromised renal transplant patients and that reduction of immunosuppression in order to overcome infection risks allograft rejection. Early detection and management are essential to reduce morbidity associated with these viruses among immunocompromised transplant recipients.

Diarrhea in kidney transplant recipients: Etiology and outcome

BACKGROUND AND AIM

Diarrhea in kidney transplant recipients influences outcome of transplantation. Data from India in this regard are sparse and do not address the differential outcome of infective and non-infective diarrhea. We studied the demographic data, laboratory findings, treatment response, disease duration, and outcome of diarrhea in kidney transplant recipients, and the differential outcome between infective and non-infective diarrhea, if any.

METHODS

All kidney transplant recipients who were referred to the Division of Gastroenterology with diarrhea between June 2015 and February 2017 were prospectively included. Demographic, clinical and laboratory data, graft function, treatment administered, and outcome were noted, and the patients were followed up for 3 months.

RESULTS

Forty-seven patients (median age 45 years, range 16-78; 34 men) with 64 episodes of diarrhea were studied. Thirty-three (51.5%) episodes were attributed to infections. Eleven (17%) were immunosuppressant-induced (mycophenolate 8, tacrolimus 2, cyclosporine 1). Twenty (31%) were due to other causes (antibiotics 6, laxatives 3, irritable bowel syndrome 3, sepsis 8). Fifty-three episodes (82%) had graft dysfunction during the diarrheal episodes. Mean increase in serum creatinine was 45% in the infectious diarrhea group and 95% in the non-infectious diarrhea group (p < 0.05). Median time to resolution of diarrhea was 3 days. With improvement in diarrhea, return to pre-diarrhea creatinine levels occurred in 87% of episodes at 3 months.

CONCLUSION

One-half of episodes of diarrhea in kidney transplant recipients were non-infectious in origin. Seventeen percent were attributed to immunosuppressants, requiring dose modification. More than 80% were associated with worsening of graft function. Recovery of graft function to baseline was seen in a majority of cases with the resolution of diarrhea.

Correlation between changes in gut flora and serum inflammatory factors in children with noninfectious diarrhea

Purpose

To assess the association between changes in gut flora and serum inflammatory factors in children with noninfectious diarrhea.

Basic Procedure

Ninety-three children diagnosed with and treated for noninfectious diarrhea (diarrhea group) and 80 healthy children (healthy control group) were enrolled in this study. Fresh fecal samples were diluted, and after cultivating bacteria for 48 hours at 37°C, we compared the number of bacterial cells in gut flora per gram of feces and determined gut colonization resistance.

Findings

The abundance of Escherichia coli and Enterococcus in feces was significantly higher in the diarrhea group than in the healthy control group. Conversely, the abundance of Bifidobacterium and lactic acid bacteria was significantly lower in the diarrhea group than in the healthy control group. Serum interleukin (IL)-1, IL-6, IL-17, and tumor necrosis factor (TNF)-α levels in the diarrhea group were significantly higher than those in the healthy control group. Pearson’s correlation analysis revealed that serum IL-1, IL-6, IL-17, and TNF-α levels positively correlated with abundance of E. coli and Enterococcus and negatively correlated with abundance of Bifidobacterium and lactic acid bacteria.

Conclusions

Gut dysbacteriosis and overexpression of serum inflammatory factors occur in children with noninfectious diarrhea and are closely correlated.

Diagnosis and management of diarrhea in solid-organ transplant recipients: Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the diagnosis, prevention, and management of diarrhea in the pre- and post-transplant period. Diarrhea in an organ transplant recipient may result in significant morbidity including dehydration, increased toxicity of medications, and rejection. Transplant recipients are affected by a wide range of etiologies of diarrhea with the most common causes being Clostridioides (formerly Clostridium) difficile infection, cytomegalovirus, and norovirus. Other bacterial, viral, and parasitic causes can result in diarrhea but are far less common. Further, noninfectious causes including medication toxicity, inflammatory bowel disease, post-transplant lymphoproliferative disease, and malignancy can also result in diarrhea in the transplant population. Management of diarrhea in this population is directed at the cause of the diarrhea, instituting therapy where appropriate and maintaining proper hydration. Identification of the cause to the diarrhea needs to be timely and focused.

Prevalence of rotavirus and human bocavirus in immunosuppressed individuals after renal transplantation in the Northern Region of Brazil

Immunosuppressive therapy causes severe impairment of host defense and diarrhea is a frequent complication in renal transplant recipients. This study aimed to describe the occurrence of Rotavirus A (RVA) and Human Bocavirus (HBoV) in fecal samples of immunosuppressed patients submitted to renal transplantation during posttransplant follow-up. A longitudinal study was carried out involving a 25-patient cohort, selected for kidney transplantation. A total of 126 fecal samples were collected between May 2014 and May 2016. Molecular techniques were used to detect and characterize circulating RVA and HBoV genotypes and statistical analysis were applied to verify the association between epidemiological and clinical characteristics. The prevalence of RVA and HBoV was 24% (6/25) and 40% (10/25), respectively. Among RVA and HBoV positive cases, the majority was female; did not conduct water treatment nor had adequate sewage facilities. The most detected genotypes were RVA G3 (62.5%) and HBoV-3 (95%). Phylogenetic analysis of HBoV strains indicated that studied samples were similar to those found in Asian and American countries. The present study point out the circulation of these viral agents among immunosuppressed individuals and these findings will enable the construction of new knowledge and care perspectives on the cause of diarrhea in this population.

A Case of Intestinal Microsporidiosis in a Renal Transplant Recipient

Post-renal transplant diarrhea is a common clinical presentation. An extensive list of potential etiology adds to the diagnostic dilemma. In cases of prolonged or intractable diarrhea, invasive tests are often performed. Intestinal microsporidia can be diagnosed with simple non-invasive stool polymerase chain reaction (PCR). Based on this case, we propose an easy to follow flow chart and present a literature review on post-renal transplant diarrhea. Further multicenter validation testing is required for the proposed flow chart.

Baseline graft status is a critical predictor of kidney graft failure after diarrhoea

Background

Diarrhoea is one of the most frequent complications after kidney transplantation (KT). Non-infectious diarrhoea has been associated with reduced graft survival in kidney transplant recipients. However, the risk factors for renal allograft loss following diarrhoea remain largely unknown.

Methods

Between January 2010 and August 2011, 195 consecutive KT recipients who underwent standardized microbiological workups for diarrhoea at a single centre were enrolled in this retrospective study.

Results

An enteric pathogen was readily identified in 91 patients (47%), while extensive microbiological investigations failed to find any pathogen in the other 104. Norovirus was the leading cause of diarrhoea in these patients, accounting for 30% of the total diarrhoea episodes. The baseline characteristics were remarkably similar between non-infectious and infectious diarrhoea patients, with the exception that the non-infectious group had significantly lower graft function before diarrhoea (P = 0.039). Infectious diarrhoea was associated with a longer duration of symptoms (P = 0.001) and higher rates of acute kidney injury (P = 0.029) and hospitalization (P &lt; 0.001) than non-infectious diarrhoea. However, the non-infectious group had lower death-censored graft survival than the infectious group (Gehan–Wilcoxon test, P = 0.038). Multivariate analysis retained three independent predictors of graft failure after diarrhoea: diarrhoea occurring ≥5 years after KT [hazard ratio (HR) 4.82; P &lt; 0.001], re-transplantation (HR 2.38; P = 0.001) and baseline estimated glomerular filtration rate &lt;30 mL/min/1.73 m2 (HR 11.02; P &lt; 0.001).

Conclusion

Our study shows that pre-existing conditions (re-transplantation, chronic graft dysfunction and late occurrence) determine the primary functional long-term consequences of post-transplant diarrhoea.

Three Severe Cases of Viral Infections with Post-Kidney Transplantation Successfully Confirmed by Polymerase Chain Reaction and Flow Cytometry

Viral infections in patients with post-kidney transplantation are often difficult to diagnose as well as treat. We herein report three cases with severe viral infections after kidney transplantation. All their causative pathogens could be detected promptly by polymerase chain reaction and flow cytometry during the early stages of infection. These examinations would also be of great use to monitor therapeutic responses and disease activity. It is indeed true that no specific treatment is available for most of the viral infections, but we should be aware that some infections, such as Epstein-Barr virus infection, can be treatable with prompt and specific treatment, such as rituximab.

Gastrointestinal pathogens in anti-FH antibody positive and negative Hemolytic Uremic Syndrome

BACKGROUND

Prodromal symptoms are frequently reported in the atypical form of Hemolytic uremic syndrome (aHUS) suggesting implication of infectious triggers. Some pathogens may also play a role in the mechanisms of production of autoantibody directed against Factor H (FH), a complement regulator, leading to aHUS.

METHODS

The presence of 15 gastrointestinal (GI) pathogens was investigated by using xTAG-based multiplex PCR techniques on stools collected at the acute phase in a cohort of Indian HUS children classified according to the presence or absence of anti-FH autoantibodies.

RESULTS

Prevalence of pathogens in patients with anti-FH antibody (62.5%) was twice that in those without (31.5%). Different pathogens were detected, the most frequent being Clostridium difficile, Giardia intestinalis, Salmonella, Shigella, Rotavirus, Norovirus and Entamoeba histolytica. No stool was positive for Shigatoxin.

CONCLUSION

This study reveals a higher prevalence of GI pathogens in anti-FH positive than in negative patients. No single pathogen was implicated exclusively in one form of HUS. These pathogens may play a role in the disease initiation by inducing complement activation or an autoimmune response.

Rapid diagnosis of parasitic diseases: current scenario and future needs

BACKGROUND

Parasitic diseases are one of the world's most devastating and prevalent infections, causing millions of morbidities and mortalities annually. In the past, many of these infections have been linked predominantly to tropical or subtropical areas. Nowadays, however, climatic and vector ecology changes, a significant increase in international travel, armed conflicts, and migration of humans and animals have influenced the transmission of some parasitic diseases from 'book pages' to reality in developed countries. It has also been noted that many patients who have never travelled to endemic areas suffer from blood-borne infections caused by protozoa. In the light of existing knowledge, this new trend can be explained by the fact that in the process of migration a large number of asymptomatic carriers become a part of the blood bank donor and transplant donor populations. Accurate and rapid diagnosis represents the crucial weapon in the fight against parasitic infections.

AIMS

To review old and new approaches for rapid diagnosis of parasitic infections.

SOURCES

Data for this review were obtained through searches of PubMed using combinations of the following terms: parasitological diagnostics, microscopy, lateral flow assays, immunochromatographic assays, multiplex-PCR, and transplantation.

CONTENT

In this review, we provide a brief account of the advantages and limitations of rapid methods for diagnosis of parasitic diseases and focus our attention on current and future research in this area. The approximate costs associated with the use of different techniques and their applicability in endemic and non-endemic areas are also discussed.

IMPLICATIONS

Microscopy remains the cornerstone of parasitological diagnostics, especially in the field and low-resource settings, and provides epidemiological assessment of parasite burden. However, increased use and availability of point-of-care tests and molecular assays in modern era allow more rapid and accurate diagnoses and increased sensitivity in the identification of parasitic infections.

Exploration of Fecal Microbiota Transplantation in the Treatment of Refractory Diarrhea After Renal Transplantation

OBJECTIVE

Exploration of fecal microbiota transplantation in the treatment of refractory diarrhea after renal transplantation.

METHODS

Summarize the etiology of 120 cases with diarrhea after renal transplantation from 2014 to 2017 in our hospital. There were 4 recipients of refractory diarrhea who accepted fecal microbiota transplantation with informed consent, and we collected clinical data of stool and bacterial culture, gut microbiota analysis, graft function, electrolytes, immunosuppressant concentrations of prognostic evaluation of patients with fecal transplantation.

RESULTS

The absorption of electrolyte is slightly higher and concentration of tacrolimus and creatinine were not significantly changed compared with before.

CONCLUSION

Fecal microbiota transplantation provides a new choice to refractory diarrhea after renal transplantation as an innovative treatment, but the effectiveness of fecal microbiota transplantation needs long-term observation and further evaluation through large sample data.

Multiplex tests to identify gastrointestinal bacteria, viruses and parasites in people with suspected infectious gastroenteritis: a systematic review and economic analysis

BACKGROUND

Gastroenteritis is a common, transient disorder usually caused by infection and characterised by the acute onset of diarrhoea. Multiplex gastrointestinal pathogen panel (GPP) tests simultaneously identify common bacterial, viral and parasitic pathogens using molecular testing. By providing test results more rapidly than conventional testing methods, GPP tests might positively influence the treatment and management of patients presenting in hospital or in the community.

OBJECTIVE

To systematically review the evidence for GPP tests [xTAG^® (Luminex, Toronto, ON, Canada), FilmArray (BioFire Diagnostics, Salt Lake City, UT, USA) and Faecal Pathogens B (AusDiagnostics, Beaconsfield, NSW, Australia)] and to develop a de novo economic model to compare the cost-effectiveness of GPP tests with conventional testing in England and Wales.

DATA SOURCES

Multiple electronic databases including MEDLINE, EMBASE, Web of Science and the Cochrane Database were searched from inception to January 2016 (with supplementary searches of other online resources).

REVIEW METHODS

Eligible studies included patients with acute diarrhoea; comparing GPP tests with standard microbiology techniques; and patient, management, test accuracy or cost-effectiveness outcomes. Quality assessment of eligible studies used tailored Quality Assessment of Diagnostic Accuracy Studies-2, Consolidated Health Economic Evaluation Reporting Standards and Philips checklists. The meta-analysis included positive and negative agreement estimated for each pathogen. A de novo decision tree model compared patients managed with GPP testing or comparable coverage with patients managed using conventional tests, within the Public Health England pathway. Economic models included hospital and community management of patients with suspected gastroenteritis. The model estimated costs (in 2014/15 prices) and quality-adjusted life-year losses from a NHS and Personal Social Services perspective.

RESULTS

Twenty-three studies informed the review of clinical evidence (17 xTAG, four FilmArray, two xTAG and FilmArray, 0 Faecal Pathogens B). No study provided an adequate reference standard with which to compare the test accuracy of GPP with conventional tests. A meta-analysis (of 10 studies) found considerable heterogeneity; however, GPP testing produces a greater number of pathogen-positive findings than conventional testing. It is unclear whether or not these additional 'positives' are clinically important. The review identified no robust evidence to inform consequent clinical management of patients. There is considerable uncertainty about the cost-effectiveness of GPP panels used to test for suspected infectious gastroenteritis in hospital and community settings. Uncertainties in the model include length of stay, assumptions about false-positive findings and the costs of tests. Although there is potential for cost-effectiveness in both settings, key modelling assumptions need to be verified and model findings remain tentative.

LIMITATIONS

No test-treat trials were retrieved. The economic model reflects one pattern of care, which will vary across the NHS.

CONCLUSIONS

The systematic review and cost-effectiveness model identify uncertainties about the adoption of GPP tests within the NHS. GPP testing will generally correctly identify pathogens identified by conventional testing; however, these tests also generate considerable additional positive results of uncertain clinical importance.

FUTURE WORK

An independent reference standard may not exist to evaluate alternative approaches to testing. A test-treat trial might ascertain whether or not additional GPP 'positives' are clinically important or result in overdiagnoses, whether or not earlier diagnosis leads to earlier discharge in patients and what the health consequences of earlier intervention are. Future work might also consider the public health impact of different testing treatments, as test results form the basis for public health surveillance.

STUDY REGISTRATION

This study is registered as PROSPERO CRD2016033320.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

The role of multiplex molecular panels for the diagnosis of gastrointestinal infections in immunocompromised patients

PURPOSE OF REVIEW

An increasing number of laboratories have implemented multiplex molecular panels for the diagnosis of gastrointestinal infections. This review focuses on recent data addressing the performance of US Food and Drug Administration-cleared multiplex gastrointestinal panels and discusses the advantages and limitations of these tests in the immunocompromised population.

RECENT FINDINGS

Testing for gastrointestinal pathogens using multiplex molecular panels increases sensitivity and detection of coinfections compared with routine testing methods. Furthermore, multiplex panels reduce turnaround time and may allow for more informed decisions regarding treatment and infection control measures. However, the routine use of multiplex gastrointestinal panels has led to an increase in the detection of certain organisms, such as enteroaggregative Escherichia coli and sapovirus, which many clinical laboratories did not specifically test for in the past. This has created a degree of confusion on how to best interpret the results of multiplex panels, especially in the immunocompromised host.

SUMMARY

Multiplex molecular panels provide a rapid and sensitive tool for the diagnosis of infectious diarrhea, and may allow for more timely decisions regarding the management of immunosuppressed patients. However, there are limitations associated with multiplex panels, including the interpretation of results and the cost associated with testing. Clinical microbiologists should work closely with clinicians to develop evidence-based algorithms to guide test utilization in this area.

Practical Guidance for Clinical Microbiology Laboratories: Laboratory Diagnosis of Parasites from the Gastrointestinal Tract

This Practical Guidance for Clinical Microbiology document on the laboratory diagnosis of parasites from the gastrointestinal tract provides practical information for the recovery and identification of relevant human parasites. The document is based on a comprehensive literature review and expert consensus on relevant diagnostic methods. However, it does not include didactic information on human parasite life cycles, organism morphology, clinical disease, pathogenesis, treatment, or epidemiology and prevention. As greater emphasis is placed on neglected tropical diseases, it becomes highly probable that patients with gastrointestinal parasitic infections will become more widely recognized in areas where parasites are endemic and not endemic. Generally, these methods are nonautomated and require extensive bench experience for accurate performance and interpretation.

Evaluation of a multiplex panel for the diagnosis of acute infectious diarrhea in immunocompromised hematologic patients

Introduction

Diarrhea is a frequent complication in hematologic patients, being an infectious cause frequently suspected. Rapid and accurate detection of gastrointestinal pathogens is vital in immunocompromised hosts. The aim of this study was to compare routine diagnostic methods versus a multiplex polymerase chain reaction (PCR) assay for the diagnosis of infectious diarrhea in immunocompromised hematologic patients.

Material and methods

We conducted a prospective observational study from March 2015 to January 2016 to compare conventional methods for the diagnosis of infectious diarrhea with FIlmArray GI Panel (BioFire-bioMérieux, France). Samples from adult immunocompromised hematologic patients with acute diarrhea were collected. In cases with discordant results, a second multiplex assay was performed (Allplex, Seegene, Korea). The result was considered positive or negative when the same result was obtained by at least two of the methods.

Results

A total of 95 samples were obtained from 95 patients (median age of 52 years (46–64)). Sixty-one (64%) episodes were hospital-acquired and 34 (36%) were community-acquired diarrhea. Twenty-five (26%) patients had a positive microbiological result, being Clostridium difficile the most frequent pathogen, followed by Campylobacter spp and norovirus. The concordance between FilmArray methods was good (k = 0.79). The FilmArray GI panel showed a sensitivity of 95%, a specificity of 100% for positive results. The time required to obtain results was markedly reduced with the use of multiplex PCR methods.

Conclusions

Multiplex molecular panels provide a rapid and sensitive tool for the diagnosis of infectious diarrhea, thereby allowing more timely clinical decisions in immunocompromised hematologic patients.

Inhibition of Calcineurin or IMP Dehydrogenase Exerts Moderate to Potent Antiviral Activity against Norovirus Replication

Norovirus is a major cause of acute gastroenteritis worldwide and has emerged as an important issue of chronic infection in transplantation patients. Since no approved antiviral is available, we evaluated the effects of different immunosuppressants and ribavirin on norovirus and explored their mechanisms of action by using a human norovirus (HuNV) replicon-harboring model and a surrogate murine norovirus (MNV) infectious model. The roles of the corresponding drug targets were investigated by gain- or loss-of-function approaches. We found that the calcineurin inhibitors cyclosporine (CsA) and tacrolimus (FK506) moderately inhibited HuNV replication. Gene silencing of their cellular targets, cyclophilin A, FKBP12, and calcineurin, significantly inhibited HuNV replication. A low concentration, therapeutically speaking, of mycophenolic acid (MPA), an uncompetitive IMP dehydrogenase (IMPDH) inhibitor, potently and rapidly inhibited norovirus replication and ultimately cleared HuNV replicons without inducible resistance following long-term drug exposure. Knockdown of the MPA cellular targets IMPDH1 and IMPDH2 suppressed HuNV replication. Consistent with the nucleotide-synthesizing function of IMPDH, exogenous guanosine counteracted the antinorovirus effects of MPA. Furthermore, the competitive IMPDH inhibitor ribavirin efficiently inhibited norovirus and resulted in an additive effect when combined with immunosuppressants. The results from this study demonstrate that calcineurin phosphatase activity and IMPDH guanine synthase activity are crucial in sustaining norovirus infection; thus, they can be therapeutically targeted. Our results suggest that MPA shall be preferentially considered immunosuppressive medication for transplantation patients at risk of norovirus infection, whereas ribavirin represents as a potential antiviral for both immunocompromised and immunocompetent patients with norovirus gastroenteritis.

Chronic Norovirus Infection as a Risk Factor for Secondary Lactose Maldigestion in Renal Transplant Recipients: A Prospective Parallel Cohort Pilot Study

BACKGROUND

Chronic norovirus infection is an emerging challenge in the immunocompromised host, in whom it may be asymptomatic or present as chronic diarrhea. The mechanisms of diarrhea in chronic norovirus infection are not well understood, but in analogy to Gardia lamblia and rotavirus infections, secondary lactose maldigestion (LM) might be implicated.

METHODS

Adult renal transplant recipients who had symptomatic chronic norovirus infection with diarrhea were asked to participate in this prospective parallel cohort study. Renal transplant recipients with otherwise unexplainable chronic diarrhea but absent infection served as control group. In both groups, a lactose hydrogen breath test and a lactose tolerance test were performed after exclusion of primary LM by a negative lactase gene test.

RESULTS

Of approximately 800 patients in the cohort of renal transplant recipients at our institution, 15 subjects were included in the present study. Of these, 7 had chronic symptomatic norovirus infection with diarrhea (noro group), and 8 had diarrhea in the absence of norovirus (control group). Lactose hydrogen breath test and lactose tolerance test were positive in all 7 patients (100%) in the noro group, whereas only 1 (12.5%) of 8 patients in the control group had a positive test. Thus, secondary LM was highly prevalent in the noro compared with the control group with an odds ratio of 75.0 (95% confidence interval, 2.6-2153, P = 0.01).

CONCLUSIONS

This is the first report showing a positive association of chronic norovirus infection and secondary LM. Further studies with larger patient numbers and longer follow-up are needed to test a causative relationship between both entities.

Detection of gastrointestinal pathogens in oncology patients by highly multiplexed molecular panels

We compared the frequency of gastrointestinal (GI) pathogen detection in an oncology patient population by two multiplexed molecular assays, the Luminex xTAG® Gastrointestinal Pathogen Panel (GPP, which identifies 14 GI pathogens) and the BioFire Gastrointestinal Panel (BFGP, which identifies 22 GI pathogens). We additionally reviewed the clinical characteristics of patients tested with both panels. A total of 200 prospectively collected and 81 archived stool samples were tested by both panels. In the prospective cohort, the GPP and BFGP identified a pathogen in 33.5% [95% confidence interval (CI): 27.3-40.35%] and 39.6% (95% CI: 33.0%-46.6%) of samples, respectively (p = 0.25). The BFGP detected significantly more pathogens than the GPP (p = 0.038), with 21.3% of samples positive for targets only detected by the BFGP. The concordance between the assays was very good at 91.1% (κ = 0.8, 95% CI: 0.7-0.9) when considering only pathogens detected by both assays. The most frequent pathogens detected were Clostridium difficile, norovirus, Campylobacter, and Salmonella species. On the archived samples, the BFGP was positive in 92.6% of samples but detected more pathogens than the GPP (86 vs. 97, p = 0.033), including both targets unique to the BFGP and targets common to both panels. A pathogen was more frequently detected in patients with hematological malignancies than solid tumors and in ambulatory patients compared to hospitalized patients, but these differences were not statistically significant. Overall, the detection rates were similar for both the GPP and the BFGP, and the latter detected more than one pathogen in additional patients. The impact of increased detection of GI pathogens by multiplexed panels on the clinical care of oncology patients will require further investigation.