The future of Clostridioides difficile diagnostics.

PURPOSE OF REVIEW: Although the epidemiology of Clostridioides difficile has changed, this organism continues to cause significant morbidity and mortality. This review addresses current and future approaches to the diagnosis of C. difficile disease. RECENT FINDINGS: Over the last several years, large prospective studies have confirmed that there is no single optimal test for the diagnosis of C. difficile disease. The pendulum has swung from a focus on rapid molecular diagnosis during the years of the ribotype 027 epidemic, to a call for use of algorithmic approaches that include a test for toxin detection. In addition, diagnostic stewardship has been shown to improve test utilization, especially with molecular methods. Advances in testing include development of ultrasensitive toxin tests and an expansion of biomarkers that may be more C. difficile specific. Microbiome research may be leveraged to inform novel diagnostic approaches based on measurements of volatile and nonvolatile organic compounds in stool. SUMMARY: As rates of C. difficile infection decline, emphasis is now on improving test utilization and a quest for improved diagnostic approaches. These approaches may involve implementation of technologies that improve toxin testing, predict patients likely to have disease and/or a severe outcome, and harnessing research on changes in the microbiome to advance metabolomics.

A Case of Scedosporium aurantiacum Infection in the United States.

Scedosporium aurantiacum is one of the emergent opportunistic fungal pathogens among immunocompromised hosts. Colonization of S. aurantiacum can also occur in patients with underlying lung diseases such as cystic fibrosis. S. aurantiacum is highly resistant to multiple antifungal agents, and management of the infected patients can be very challenging compared to those infected with other species of Scedosporium. Clinical cases have been geographically restricted mostly in Australia with a small number of cases identified in Europe and Japan. Although clinical isolates of S. aurantiacum from the USA have been included in several research studies, no clinical case of S. aurantiacum infection from the USA has been described. We report a case of S. aurantiacum infection acquired in the SA. Awareness of S. aurantiacum among healthcare providers and the species-level identification for Scedosporium are critically important for appropriate selection of antifungal agents and improvement of treatment outcomes.

Updates on Rapid Diagnostic Tests in Infectious Diseases.

In the last two decades there have been dramatic advances in development of rapid diagnostic tests. Turnaround time of the assays have significantly been shortened which led to reductions in time to appropriate antimicrobial therapy and improvement of patient clinical outcomes. Molecular-based assays generally have better sensitivity than conventional methods, but the cost is higher. The results need to be interpreted cautiously as detection of colonized organisms, pathogen detection in asymptomatic patients, and false negative/positive can occur. Indications and cost-effectiveness need to be considered for appropriate utilization of rapid diagnostic tests.

Laboratory Tests for the Diagnosis of Clostridium difficile.

Clostridium (reclassified as " Clostridioides ") difficile is an anaerobic, gram-positive bacterium that causes significant disease through elaboration of two potent toxins in patients whose normal gut microbiota has been altered through antimicrobial or chemotherapeutic agents (dysbiosis). The optimum method of laboratory diagnosis is still somewhat controversial. Recent practice guidelines published by professional societies recommend a two-step approach beginning with a test for glutamate dehydrogenase (GDH), followed by a toxin test and/or a nucleic acid test. Alternatively, in institutions where established clinical algorithms guide testing, a nucleic acid test alone is acceptable. Nucleic acid tests are the methods of choice in approximately 50% of laboratories in the United States. These tests are considered as the most sensitive methods for detection of C. difficile in stool and are the least specific. Because of the lower specificity with nucleic acid tests, some clinicians believe that toxin enzyme immunoassays are better predictors of disease, despite their known poor performance in certain patient populations. This review will discuss the advantages and disadvantages of the currently available test methods for the diagnosis of C. difficile with a brief mention of some novel assays that are currently in clinical trials.

Prescriber Behavior in Clostridioides difficile Testing: A 3-Hospital Diagnostic Stewardship Intervention.

Computerized clinical decision support (CCDS) significantly reduced Clostridioides difficile testing at 3 hospitals; from 12.6 to 9.5, from 10.1 to 6.4, and from 14.0 to 9.6 average weekly tests per 1000 inpatient days. There were no related adverse events. Senior providers were more likely than interns or residents to follow CCDS.

Recent updates in the development of molecular assays for the rapid identification and susceptibility testing of MRSA.

INTRODUCTION: Methicillin-resistant Staphylococcus aureus (MRSA) is a frequent cause of healthcare- and community-associated infections. Nasal carriage of MRSA is a risk factor for subsequent MRSA infections. Increased morbidity and mortality are associated with MRSA infections and screening and diagnostic tests for MRSA play an important role in clinical management. AREAS COVERED: A literature search was conducted in PubMed and supplemented by citation searching. In this article, we provide a comprehensive review of molecular-based methods for MRSA screening and diagnostic tests including individual nucleic acid detection assays, syndromic panels, and sequencing technologies with a focus on their analytical performance. EXPERT OPINION: Molecular based-assays for the detection of MRSA have improved in terms of accuracy and availability. Rapid turnaround enables earlier contact isolation and decolonization for MRSA. The availability of syndromic panel tests that include MRSA as a target has expanded from positive blood cultures to pneumonia and osteoarticular infections. Sequencing technologies allow detailed characterizations of novel methicillin-resistance mechanisms that can be incorporated into future assays. Next generation sequencing is capable of diagnosing MRSA infections that cannot be identified by conventional methods and metagenomic next-generation sequencing (mNGS) assays will likely move closer to implementation as front-line diagnostics in the near future.

Updates on the profile of GenMark's ePlex blood culture identification fungal pathogen panel.

INTRODUCTION: The clinical and economical burdens of invasive fungal diseases (IFDs) remain substantial despite advances in diagnostics and therapeutics. Major challenges in diagnosis of IFDs are difficulty in obtaining appropriate specimens for histopathology examination and prolonged turnaround time for fungal cultures. Molecular assays for direct detection of fungal DNA from sterile sites such as blood can provide definitive diagnosis of IFDs in a reduced turnaround time. The ePlex BCID-FP Panel from GenMark Diagnostics, a member of the Roche corporation, is currently the largest commercial multiplex fungal pathogen identification panel for blood cultures and has potential for early optimization of treatment and improvement of patient outcomes. AREAS COVERED: This article provides a comprehensive review of the ePlex BCID-FP Panel including its market profile, assay performance characteristics, clinical profile, and cost-effectiveness. Other currently available diagnostic assays for IFDs are also discussed. EXPERT OPINION: Although molecula- based assays for detection of fungal pathogens such as the ePlex BCID-FP Panel have increased diagnostic capacity for IFDs and provide timelier results compared to the conventional methods, there are still unmet clinical needs in the diagnosis of IFDs. Further development of novel assays is needed to fulfill the diagnostic gaps.

Advances and required improvements in methods to diagnosing Clostridioides difficile infections in the healthcare setting.

INTRODUCTION: Clostrididioides difficile is associated with adverse clinical outcomes and increased morbidity, mortality, length of hospital stay, and health-care costs.Areas Covered: We searched relevant papers in PubMed for the last 10 years. In major papers, we scanned the bibliographies to ensure that important articles were included. This review addresses the evolving epidemiology of Clostridioides difficile infection (CDI) and discusses novel methods/approaches for improving the diagnosis of this important disease. EXPERT OPINION: No single diagnostic test to date has demonstrated optimum sensitivity and specificity for detection of CDI. Many institutions have developed multi-step algorithms consistent with guidelines established by various professional societies. Some institutions have successfully tried to improve the pretest probability of molecular assays by implementing appropriate sample rejection criteria and establishing best practice alerts at the time of electronic order entry. Others have established PCR cycle threshold cutoffs to attempt to differentiate symptomatic patients from asymptomatic carriers or to make predictions about severity of disease with variable success. As research advances our understanding of C. difficile pathogenesis and pathophysiology, more information on CDI specific biomarkers is emerging. Finally, assessments of the microbiome and metabolome may expand the diagnostic armamentarium with advances in mass spectrometry and sequencing technologies.

High numbers of interferon-gamma-producing T cells and low titers of anti-tuberculous glycolipid antibody in individuals with latent tuberculosis.

Latent tuberculosis infection (LTBI) is defined as an infection with Mycobacterium tuberculosis (MTB) without clinical, bacteriological, or radiological findings, and its early diagnosis is essential for eradication of tuberculosis. To identify LTBI, we measured the numbers of interferon-gamma producing T cells, based on the ELISPOT assay, and the antibody titers in the sera to tuberculous glycolipid antigen (TBGL-Ab). Seventeen culture-confirmed TB patients, 13 controls from TB endemic areas (EC) and 13 controls from TB non-endemic areas (NEC) were enrolled. Peripheral blood mononuclear cells (2.5 x 10(5) per well) were cultured on plates precoated with antibody against interferon-gamma. ELISPOT response was defined as positive when the MTB-specific antigen-containing wells showed at least 6 spots and twice numbers of spots than negative control wells. ELISPOT responses were positive in 15 (88%), 8 (62%) and 4 (31%) subjects of TB, EC and NEC groups, respectively. The ELISPOT data differ between TB and NEC groups (p < 0.01) but not between TB and EC groups. In contrast, TBGL-Ab titers were elevated (> 2.0 U/ml) in 12 TB patients (71%), but only in one subject (8%) each from EC and NEC groups. These results indicate the high prevalence of LTBI in EC. In conclusion, LTBI is associated with positive ELISPOT assay and the low titer of TBGL-Ab, while positive results both in ELISPOT and TBGL-Ab assays indicate active TB. The low titer of TBGL-Ab is a helpful marker to identify LTBI in ELISPOT-positive individuals in TB endemic areas.

Novel strategies for rapid identification and susceptibility testing of MRSA.

INTRODUCTION: Methicillin-resistant Staphylococcus aureus (MRSA) is associated with adverse clinical outcomes and increased morbidity, mortality, length of hospital stay, and health-care costs. Rapid diagnosis of MRSA infections has been associated with positive impact on clinical outcomes. AREAS COVERED: We searched relevant papers in PubMed for the last 10 years. In major papers, we scanned the bibliographies to ensure that important articles were included. This review describes screening and diagnostic test methods for MRSA and their analytical performances with a focus on rapid molecular-based assays including those that are on the horizon. Future novel technologies will allow more rapid detection of phenotypic resistance. In the case of whole-genome sequencing, detection of mutations may predict resistance, transmission, and virulence. EXPERT OPINION: Currently there are many diagnostic options for the detection of MRSA in surveillance and clinical samples. In general, these are highly accurate and have resulted in improvements in targeted management and reduction in hospital or intensive care unit length of stay for both MSSA and MRSA. Impact on mortality has been variable. Promising novel technologies will not only accurately identify pathogens and detect their resistance markers but will allow discovery of virulence determinants that might further affect patient management.

A case series of rapidly growing mycobacterial catheter-related bloodstream infections among immunocompetent patients.

Rapidly growing mycobacteria (RGM) are ubiquitous in the environment and can cause a variety of human infections. Catheter-related bloodstream infections (CRBSI) caused by RGM have been reported predominantly among immunocompromised patients. Removal of central lines and antimicrobial therapy with at least 2 active agents are generally recommended for immunocompromised patients. RGM bloodstream infections (BSIs) are rare in immunocompetent patients and clinical data are very limited. Retrospective medical record review was conducted on patients with blood cultures positive for RGM from July 2012 through March 2015 at Lemuel Shattuck Hospital, a public teaching hospital in Jamaica Plain, Massachusetts, United States. RGM was suspected by presence of beaded Gram-positive bacilli on Gram staining of positive conventional blood cultures and it was confirmed as RGM by Massachusetts State Public Health Laboratory. Nineteen episodes of RGM BSI were identified in 17 patients who had no known immunocompromised conditions that predispose them to opportunistic pathogens. They were predominantly young male with history of intravenous drug use. Peripherally inserted central catheter (PICC) was present in all episodes of RGM BSI and 74% of them clinically improved with PICC removal alone without specific antibiotic therapy for RGM. They were followed up for median duration of 45 days (interquartile range 25-385). The patients remained alive and asymptomatic until the end of follow-up periods. In immunocompetent patients, removal of catheters alone without adding specific antibiotics may be sufficient for RGM CRBSI.

Localized Talaromyces marneffei infection presenting as a tonsillar mass mimicking malignancy.

Talaromyces marneffei is an opportunistic fungal infection seen in immunocompromised patients including those with HIV/AIDS. It is usually seen in patients who live in or are from tropical Asia. In HIV patients, oropharyngeal and laryngeal lesions are usually part of disseminated infection. We describe a case of 63-year-old Vietnamese male with history of HIV/AIDS who presented with localized T. marneffei tonsillar infection without disseminated disease. Imaging studies showed a right tonsillar mass with right cervical lymphadenopathy which was initially thought to be malignancy. The patient underwent biopsy of the mass and histology showed noncaseating granulomas on hematoxylin and eosin stain as well as yeast on Grocott methenamine silver stain. Fungal culture of the biopsy specimen grew suede-like grayish-white colonies with diffuse underlying deep red color pigment which was identified as Talaromyces marneffei. The patient was treated with intravenous liposomal amphotericin B and achieved resolution of symptoms and tonsillar mass. In HIV/AIDS patients who are either from endemic regions or with history of travel to endemic areas particularly Southeast Asia and China, T. marneffei infection should be considered in differential diagnoses of a tonsillar mass.

Clostridium difficile Diarrhea in the Elderly: Current Issues and Management Options.

Clostridium difficile infection (CDI) is the most common cause of infectious diarrhea in healthcare settings. Along with antimicrobial exposure, advanced age has been shown to be a significant risk factor for the development and recurrence of, and mortality from, CDI. The substantial burden of CDI in the elderly may be related to frequent healthcare exposure, the necessity for more medications, altered intestinal microbiota, and complicated comorbidities. A diagnosis of CDI is based on evidence of toxin, or the C. difficile organism itself, in a stool sample in the presence of clinical signs and symptoms. Only symptomatic patients should be tested for CDI, and routine surveillance or repeat testing on asymptomatic patients as a test of cure is discouraged. Antibiotic discontinuation alone can improve or resolve CDI in some patients, and concomitant use of antibiotics is associated with decreased response to CDI treatment. Metronidazole, vancomycin, and fidaxomicin are the therapeutic agents currently available for CDI, with the selection of these agents being based on disease severity, history of recurrence, and cost. The recurrence rate after initial treatment is 20-30%. The first recurrence can be treated with the same therapeutic agent and, for subsequent recurrences, vancomycin in a tapered and/or pulsed regimen is recommended. Fecal microbiota transplantation has shown remarkable effectiveness for recurrent anti-refractory CDI, although caution is advised in treating immunocompromised hosts and those with toxic megacolon. C. difficile can be transmitted directly and indirectly via contact with patients or their environment; therefore, isolation precautions should be initiated at the first suspicion of CDI. C. difficile spores can survive for a long time on environmental surfaces, and the patient's room and all equipment used in the room should be disinfected. In order to manage CDI in the elderly, timely diagnosis, appropriate treatment based on severity of illness, and effective infection control are essential.

Rapid loss of vaccine-acquired hepatitis B surface antibody after three doses of hepatitis B vaccination in HIV-infected persons.

HIV-infected individuals have poor responses to hepatitis B vaccine and may have decreased durability of post-vaccination immunity. Retrospective chart review was conducted for HIV-1 positive individuals aged ≥18 years who received hepatitis B vaccine at an urban HIV clinic. A total of 309 patients completed three doses and 178 had post-vaccine serology testing after the third dose. In multivariate analysis, time between the third dose and the first post-vaccine serology testing at 180-359 days (OR = 0.077, p = 0.049) and at ≥360 days (OR = 0.065, p = 0.019) were associated with poor vaccine responses. A significant decrease in seropositivity appeared as early as 180 days after the third vaccine dose, suggesting a rapid loss of vaccine-acquired hepatitis B surface antibody in HIV-infected persons. Our findings suggest that hepatitis B surface antibody should be tested at 6 to 12 months after completing primary vaccine series in order to detect early secondary vaccine failure.

Increased synthesis of anti-tuberculous glycolipid immunoglobulin G (IgG) and IgA with cavity formation in patients with pulmonary tuberculosis.

Tuberculous glycolipid (TBGL) antigen is a cell wall component of Mycobacterium tuberculosis and has been used for the serodiagnosis of tuberculosis. We investigated correlations between the levels of anti-TBGL antibodies and a variety of laboratory markers that are potentially influenced by tuberculous infection. Comparisons between patients with cavitary lesions and those without cavitary lesions were also made in order to determine the mechanism underlying the immune response to TBGL. Blood samples were obtained from 91 patients with both clinically and microbiologically confirmed active pulmonary tuberculosis (60 male and 31 female; mean age, 59 +/- 22 years old). Fifty-nine patients had cavitary lesions on chest X-rays. Positive correlations were found between anti-TBGL immunoglobulin G (IgG) and C-reactive protein (CRP) (r = 0.361; P < 0.001), between anti-TBGL IgA and soluble CD40 ligand (sCD40L) (r = 0.404; P < 0.005), between anti-TBGL IgG and anti-TBGL IgA (r = 0.551; P < 0.0000005), and between anti-TBGL IgM and serum IgM (r = 0.603; P < 0.00000005). The patients with cavitary lesions showed significantly higher levels of anti-TBGL IgG (P < 0.005), anti-TBGL IgA (P < 0.05), white blood cells (P < 0.01), neutrophils (P < 0.005), basophils (P < 0.0005), natural killer cells (P < 0.05), CRP (P < 0.0005), KL-6 (sialylated carbohydrate antigen KL-6) (P < 0.0005), IgA (P < 0.05), and sCD40L (P < 0.01). The observed positive correlations between the anti-TBGL antibody levels and inflammatory markers indicate the involvement of inflammatory cytokines and NKT cells in the immunopathogenesis of pulmonary tuberculosis.

Induction of remission of relapsed acute myeloid leukemia after unrelated donor cord blood transplantation by concomitant low-dose cytarabine and calcitriol in adults.

Low-dose cytarabine and calcitriol (LDCA + VD3) combination therapy was performed in two adult patients with acute myeloid leukemia (AML) that relapsed within 1 yr after unrelated donor cord blood transplantation (URD CBT) performed in a relapse or non-remission stage. Concomitant aclarubicin was also administered in one patient. Remission because of recovery of donor cord blood hematopoiesis was obtained in both patients. The treatment was low intensive, and neither adverse effects in terms of digestive symptoms nor hypercalcemia was observed. Activity of daily life was maintained. The patients were followed as outpatients after remission, and the remission duration was approximately 6 months in both patients. Although LDCA + VD3 therapy is minimally intensive chemotherapy, it may prolong the survival time of patients with relapsed AML after URD CBT.