Gastrointestinal infections in the immunocompromised host

Performance of the QIAstat-Dx Gastrointestinal Panel for Diagnosing Infectious Gastroenteritis

Detection and identification of enteropathogens that cause infectious gastroenteritis are essential steps for appropriate patient treatment and effective isolation precautions. Several syndrome-based tests have recently become available, with the gastrointestinal panel (GIP) assay on the QIAstat-Dx as the most recent addition to the syndromic testing landscape.

Detection and identification of enteropathogens that cause infectious gastroenteritis are essential steps for appropriate patient treatment and effective isolation precautions. Several syndrome-based tests have recently become available, with the gastrointestinal panel (GIP) assay on the QIAstat-Dx as the most recent addition to the syndromic testing landscape. The QIAstat-Dx GIP assay offers simultaneous testing for 24 bacterial, viral, and parasitic enteropathogens using a single test that reports the results in 70 min. In this study, we compared the performance of the GIP assay to laboratory-developed real-time PCR assays (LDTs), using 172 prospectively and retrospectively collected fecal samples from patients suspected to have infectious gastroenteritis. The GIP assay detected 97/107 enteropathogens (91%) that were detected by LDTs, and the overall agreement of results increased to 95% when excluding discrepant results with cycle threshold (C_T) values of >35. Further, the GIP assay detected 42 additional enteropathogens that were not detected, or tested, by LDTs. These included 35 diarrheagenic Escherichia coli targets for which the clinical relevance is unclear for most. The main advantage of the QIAstat-Dx system compared to other syndromic testing systems is the ability to generate C_T values that could help with the interpretation of results. However, compared to LDTs, the GIP assay is limited by flexibility and high-throughput testing. In conclusion, the GIP assay offers an easy, sample-to-answer workflow with a rapid detection of the most common enteropathogens and therefore has the potential to direct appropriate therapy and infection control precautions.

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.

Comparative Evaluation of Broad-Panel PCR Assays for the Detection of Gastrointestinal Pathogens in Pediatric Oncology Patients

Broadly multiplexed molecular amplification assays offer an unprecedented ability to diagnose gastrointestinal infection in immunocompromised patients. However, little data are available to compare the performance of such systems in this population. A total of 436 stool samples were collected from 199 predominantly immunocompromised pediatric oncology patients. Remnant samples were tested in parallel with the use of the premarket (investigational use only) versions of two broadly multiplexed PCR assays (BioFire and Luminex), and the results of samples corresponding to the first episode per patient were compared with those from laboratory-developed molecular assays, culture, and antigen detection. Overall performance of the multiplexed systems was comparable, with BioFire and Luminex detecting 94 and 99 positives (P = 0.34), respectively. Stratifying by analyte, BioFire assay detected 51 samples positive for Clostridium difficile, whereas Luminex assay detected 60 (P = 0.01). Biofire and Luminex detected 28 and 38 norovirus-positive samples (P = 0.002), respectively. Astrovirus- and adenovirus-positive samples were detected in higher numbers by in-house PCR than by BioFire; the same was observed for adenovirus with Luminex. Differences observed with other analytes were minimal, did not reach statistical significance, or lacked the numbers needed to detect a difference between systems. Broadly multiplexed PCR offers an effective means of detecting a variety of gastrointestinal pathogens in pediatric oncology patients, with assay performance comparable among the tests examined.

The occurrence and prevention of foodborne disease in vulnerable people

In developed countries, such as the United Kingdom and the United States, between 15% and 20% of the population show greater susceptibility than the general population to foodborne disease. This proportion includes people with primary immunodeficiency, patients treated with radiation or with immunosuppressive drugs for cancer and diseases of the immune system, those with acquired immune-deficiency syndrome and diabetics, people suffering from liver or kidney disease or with excessive iron in the blood, pregnant women, infants, and the elderly. Malnutrition and use of antacids, particularly proton-pump inhibitors, also increase susceptibility. We review the occurrence of infection by foodborne pathogens in these groups of people and measures to prevent infection. The nature and use of low microbial diets to reduce the risk of foodborne disease in immunocompromised patients are very variable. Diets for vulnerable people in care should exclude higher-risk foods, and vulnerable people in the community should receive clear advice about food safety, in particular avoidance of higher-risk foods and substitution of safer, nutritious foods.

Diagnosis and management of infectious complications in critically ill patients with cancer

Cancer and its treatments lead to profound suppression of innate and acquired immune function. In this population, bacterial infections are common and may rapidly lead to overwhelming sepsis and death. Furthermore, infections caused by viral and fungal pathogens should be considered in patients who have specific immune defects. As cancer therapies have become more aggressive the risk for infection has increased and many patients require intensive care support. Despite improvements in long-term survival, infections remain a common complication of cancer therapy and accounts for the majority of chemotherapy-associated deaths. By understanding the host defense impairments and likely pathogens clinicians will be better able to guide diagnosis and management of this unique population.

Rotavirus enteritis in solid organ transplant recipients: an underestimated problem?

BACKGROUND

Diarrhea in solid organ transplantation can be a complication with a high morbidity and mortality. Rotavirus (RV) infection normally occurs in children up to 3 years of age and often presents with severe diarrhea; however, it can also affect adults. We investigated the prevalence and outcome of RV infections in both adult and pediatric patients after solid organ transplantation.

PATIENTS AND METHODS

Retrospective analysis of RV-related enteritis in solid organ transplant recipients with a minimum of a 1-year follow-up from a single center between 2000 and 2004.

RESULTS

Within our cohort of 1303 solid organ transplants, RV infection was observed in 19 patients (1.5%); 14 of these were liver recipients. Infection was most prevalent among pediatric liver recipients, with 52% (11/21) of the children affected. Five adults acquired the infection during their initial hospitalization. Two adult patients had to be readmitted following late-onset RV infection. In all cases, infection was self-limiting, but led to prolonged hospitalization because of significant loss of fluids and electrolytes.

CONCLUSIONS

RV enteritis is a common infection in pediatric solid organ recipients but may also affect adult patients.

Gastroduodenal cytomegalovirus infection is common in kidney transplantation patients

OBJECTIVE

Cytomegalovirus (CMV) infection is known to cause ulcerations, erosion and mucosal haemorrhage in the gastrointestinal tract. The aim of this study was to report the CMV findings in the gastroduodenal mucosa of kidney transplantation patients and immunocompetent controls.

MATERIAL AND METHODS

Forty-six kidney transplant patients with upper gastrointestinal symptoms and 43 immunocompetent, dyspeptic patients (controls) prospectively underwent oesophagogastroduodenoscopies (OEGDs), with biopsies from the duodenum and stomach. CMV was demonstrated by immunohistochemistry, both in frozen sections using a monoclonal antibody against CMV-specific antigens (pp65 matrix protein) and in paraffin sections by means of a monoclonal antibody against the delayed early protein (p52).

RESULTS

CMV was detected in the gastric mucosa in 30% of the kidney transplant patients and in 9% of the controls (p<0.05) and in the duodenal mucosa in 70% and 35%, respectively (p<0.01). The total frequency of CMV findings was similar in patients who underwent OEGDs <1 year and >1 year after transplantation. CMV inclusions were found only in transplantation patients <1 year after transplantation (n=9). CMV findings, especially inclusions, in the gastric biopsies were associated with nausea and upper gastric pain. Histopathological findings in CMV-positive samples were non-specific, focal inflammation in haematoxylin-eosin-stained preparations, while CMV p52 staining showed inclusions in either the epithelial or endothelial cells.

CONCLUSIONS

CMV could be detected in the gastroduodenal mucosa in 74% of kidney transplantation patients and in 40% of immunocompetent controls (p<0.01). CMV diagnostics are always recommended when gastroduodenal biopsies of kidney transplantation patients are performed.

Gastrointestinal infections in the immunocompromised host

Persons with HIV infection, leukemia, lymphoma, solid organ and bone marrow transplants, and inherited immune deficiencies as well as those on immunosuppressive drugs are at high risk for infections of the gastrointestinal tract. Pathogenic as well as opportunistic viruses, bacteria, fungi, and protozoa cause infections in the esophagus, stomach, small intestine, and large intestine. Symptoms may be mild but more often are severe and even life threatening. This article reviews what is new in the field of gastrointestinal infections in the immunocompromised host during the past year. I will place specific emphasis on articles that are most pertinent to clinical care.