New molecular and surrogate biomarker-based tests in the diagnosis of bacterial and fungal infection in febrile neutropenic patients

Utility of plasma cell-free DNA next-generation sequencing for diagnosis of infectious diseases in patients with hematological disorders

BACKGROUND

Plasma cell-free DNA Next-Generation Sequencing has been used as a non-invasive and comprehensive method for the etiological diagnosis of infectious diseases. However, only a handful of studies have described the real-world utility of this technique in patients with hematological disorders, a cohort of patients that are distinctive due to neutropenia and weakened immune functions.

METHODS

We retrospectively analyzed the results of plasma cell-free DNA sequencing performed on 184 and 163 specimens collected from hematological patients suspected of infections with (Group I) or without (Group II) neutropenia, respectively. The diagnostic performance and the clinical impact of plasma sequencing were comparatively evaluated to conventional microbiological tests and a composite reference standard (conventional tests combined with the clinical assessment).

RESULTS

The overall positive detection rate of plasma cell-free DNA sequencing was significantly higher than that of conventional microbiological tests (72.6% vs.31.4%, P < 0.001). The positive rate of conventional microbiological tests in Group I was lower than that in Group II (25.5% vs. 38.0%, P = 0.012). Combining plasma sequencing with conventional tests yielded a positive detection rate of 75.0% and 74.8% for these two groups, respectively. Using the composite reference standard, the sensitivity and specificity of plasma sequencing were 89.1% and 65.1%, respectively. The proportions of the positive impact of cell-free DNA sequencing results in the Group I were higher than in the Group II in terms of both diagnosis and treatment (diagnosis: 54.3% vs. 40.5%, P = 0.013; treatment: 45.7% vs.30.7%, P = 0.004). A total of 73 patients (21.0%) benefited from plasma sequencing through adjustment of the antibiotic regimen.

CONCLUSIONS

The diagnostic yield of conventional microbiological tests was low in patients with neutropenia. Combining conventional tests with plasma cell-free DNA sequencing significantly improved the detection rate for pathogens and optimized antibiotic treatment. Our findings on the clinical impact warrant confirmation through larger, multicenter, randomized controlled trials. Moreover, the cost-effectiveness of this testing strategy remains unknown and requires further exploration.

Contemporary diagnostics for medically relevant fastidious microorganisms belonging to the genera Anaplasma, Bartonella, Coxiella, Orientia, and Rickettsia

Many of the human infectious pathogens—especially the zoonotic or vector-borne bacteria—are fastidious organisms that are difficult to cultivate because of their strong adaption to the infected host culminating in their near-complete physiological dependence on this environment. These bacterial species exhibit reduced multiplication rates once they are removed from their optimal ecological niche. This fact complicates the laboratory diagnosis of the disease and hinders the detection and further characterization of the underlying organisms, e.g. at the level of their resistance to antibiotics due to their slow growth. Here, we describe the current state of microbiological diagnostics for five genera of human pathogens with a fastidious laboratory lifestyle. For Anaplasma spp., Bartonella spp., Coxiella burnetii, Orientia spp. and Rickettsia spp., we will summarize the existing diagnostic protocols, the specific limitations for implementation of novel diagnostic approaches and the need for further optimization or expansion of the diagnostic armamentarium. We will reflect upon the diagnostic opportunities provided by new technologies including mass spectrometry and next-generation nucleic acid sequencing. Finally, we will review the (im)possibilities of rapidly developing new in vitro diagnostic tools for diseases of which the causative agents are fastidiously growing and therefore hard to detect.

Comprehensive analysis of peripheral blood non-coding RNAs identifies a diagnostic panel for fungal infection after transplantation

The occurrence of fungal infection seriously affects the survival and life quality of transplanted patients. The accurate diagnosis is of particular importance in the early stage of infection. To develop a novel diagnostic method for this kind of patient, we established a post-transplant immunosuppressed mice model with fungus inoculation and collected their peripheral blood at specific time points after infection. After screening by microarray, differentially expressed miRNAs and lncRNAs were selected and homologously analyzed with those of human beings from the gene database. These miRNAs and lncRNAs candidates were validated by qRT-PCR in peripheral blood samples from transplanted patients. We found that, compared with normal transplanted patients, the levels of miR-215 and miR-let-7 c were up-regulated in the plasma of patients with fungal infection (P < 0.01), while levels of miR-154, miR-193a, NR_027669.1, and NR_036506.1 were down-regulated in their peripheral blood mononuclear cells (P < 0.01). Principal component analysis shows that the expression pattern of the above RNAs was different between the two groups. A 6-noncoding-RNA detection panel was established by the support vector machine analysis, whose area under the ROC curve was 0.927. The accuracy, precision, sensitivity, and specificity of this model were 0.928, 0.919, 0.944, and 0.910, respectively. Though our detection panel has excellent diagnostic efficacy, its clinical application value still needs to be further confirmed by multi-center prospective clinical trials.

Cytokine and chemokine profiles in episodes of persistent high-risk febrile neutropenia in children with cancer

BACKGROUND

In children with cancer and persistent high-risk febrile neutropenia (HRFN), cytokines/chemokines profiles can guide the differentiation of febrile neutropenia (FN) due to infections and episodes of unknown origin (FN-UO).

METHODS

A prospective, multicenter study in Santiago, Chile included patients ≤ 18 years with cancer and HRFN. Clinical and microbiological studies were performed according to validated protocols. Serum levels of 38 cytokines/chemokines were determined on day 4 of persistent HRFN. We performed comparisons between i) HRFN episodes with a detected etiological agent (FN-DEA) and FN-UO, and ii) bacterial versus viral infections. ROC curves were used to assess the discriminatory power of the analytes.

RESULTS

110 HRFN episodes were enrolled (median age 8 years, 53% female). Eighty-four patients were FN-DEA: 44 bacterial, 32 viral, and 8 fungal infections. Twenty-six cases were categorized as FN-UO. Both groups presented similar clinical and laboratory characteristics. Nineteen out of 38 analytes had higher concentrations in the FN-DEA versus FN-UO group. G-CSF, IL-6, and Flt-3L showed the highest discriminatory power to detect infection (AUC 0.763, 0.741, 0.701). Serum levels of G-CSF differentiated bacterial infections and IP-10 viral agents. A combination of G-CSF, IL-6, Flt-3L, and IP-10 showed an AUC of 0.839, 75% sensitivity, and 81% specificity.

CONCLUSION

A specific immune response is present on day four of persistent HRFN in children with cancer. We propose a combined measure of serum concentrations of G-CSF, IL-6, IP-10, and Flt-3L, in order to predict the presence of an infectious agent as compared to an episode of FN with unknown origin.

A novel enzyme immunoassay for the measurement of plasma (1 → 3)-β-D-glucan levels

The presence of (1 → 3)-β-D-glucan in human plasma is a marker for fungal infections. Currently, the Limulus amebocyte lysate (LAL)-based assay is widely used for the quantification of plasma (1 → 3)-β-D-glucan. However, it has limitations in clinical use, such as an unstable supply of natural resources, complicated manufacturing process, and low-throughput of the reagents. Alternative assays exploiting specific antibodies against (1 → 3)-β-D-glucan have been developed to overcome these challenges. However, these methods are associated with low sensitivity and poorly correlate with the data obtained by the LAL-based assay. The aim of this study is to develop a novel enzyme immunoassay that is as sensitive and accurate in determining plasma (1 → 3)-β-D-glucan levels as compared to that obtained with the LAL-based assay. We generated specific monoclonal antibodies against (1 → 3)-β-D-glucan that recognizes four-unit glucose oligomers with (1 → 3)-β-D-linkages, and constructed a sandwich enzyme-linked immunosorbent assay (ELISA) using these antibodies. The newly developed ELISA showed proportional increase in absorbance with the volume of (1 → 3)-β-D-glucan added. The limit of detection of the assay was 4 pg/ml of plasma (1 → 3)-β-D-glucan that was equivalent to the LAL-based assay and the working range was 4-500 pg/ml. The intra-assay coefficient of variation was 2.2-5.4% using three different concentrations of plasma samples. We observed strong correlation (R = 0.941, slope = 0.986) between the measurements obtained by our ELISA and Fungitec G test ES Nissui, a commonly used LAL-based assay, using 26 types of plasma samples. This could be attributed to the epitopes of the antibodies. Both antibodies could inhibit the LAL-based assay, suggesting that the antibodies recognize the identical regions in β-D-glucan, thereby inactivating factor G, an initiation zymogen for coagulation cascade, in the LAL-based assay. Thus, the ELISA developed in this study can detect fungal infections in clinical settings with similar efficiency as the LAL-based assay. This assay is characterized by good performance, stable supply of materials, and simple manufacturing process and is more suitable for the high-throughput diagnosis of fungal infections.

One-Step Preparation of Phenyl Boron-Modified Magnetic Mesoporous Silica for Selective Enrichment of cis-Diol-Containing Substances

For enrichment and separation of cis-diol-containing compounds from biomatrix, a new type of magnetic nanoparticles named MS-48-PBSC, whichwas facilely prepared in a one-step heterogeneous reaction. The morphology results demonstrated that the MS-48-PBSC was a spherical nanomaterial containing a core of silica-coated magnetic particle with a diameter of about 200 nm, and a cover layer of mesoporous silica with a thickness of approximate 50 nm. The characterization results showed that MS-48-PBSC presented a pore size of 4.2 nm, a surface area of 548 m²·g⁻¹, and a pore volume of 0.30 cm³·g⁻¹. The MS-48-PBSC also exhibited magnetism of 42 emu·g⁻¹ that contributed to the easy separation of magnetic nanomaterial within 30 s from the matrix with the aid of the external magnetic field. In addition, the MS-48-PBSC exhibited high adsorption capacity for adenosine, xanthosine, uridine, sialic acid, and teicoplanin with 0.60, 0.51, 0.42, 0.75, and 1.26 mg/g, respectively, and showed a high selectivity for the cis-diol structure compounds, relative to interferences of bovine serum albumin, guanine, uric acid, and xanthine. The recoveries of adenosine, xanthosine, uridine, sialic acid, and teicoplanin were 71.8–114.1% with relative standard deviation (RSD) ≤ 8.6%, and the enrichment factors of them were 8–11. MS-48-PBSC exhibited quick separation capability from matrix, high adsorption capacity and size exclusion for bovine serum albumin, which could meet the requirements of separation and enrichment for substances with a cis-diol structure.

Commercial Molecular Tests for Fungal Diagnosis from a Practical Point of View

The increasing interest in molecular diagnostics is a result of tremendously improved knowledge on fungal infections in the past 20 years and the rapid development of new methods, in particular polymerase chain reaction. High expectations have been placed on molecular diagnostics, and the number of laboratories now using the relevant technology is rapidly increasing-resulting in an obvious need for standardization and definition of laboratory organization. In the past 10 years, multiple new molecular tools were marketed for the detection of DNA, antibodies, cell wall components, or other antigens. In contrast to classical culture methods, molecular methods do not detect a viable organisms, but only molecules which indicate its presence; this can be nucleic acids, cell components (antigens), or antibodies (Fig. 1). In this chapter, an overview is provided on commercially available detection tools, their strength and how to use them. A main focus is laid on providing tips and tricks that make daily life easier. We try to focus and mention methodical details which are not highlighted in the manufacturer's instructions of these test kits, but are based on our personal experience in the laboratory. Important to keep in mind is that molecular tools cannot replace culture, microscopy, or a critical view on patients' clinical history, signs, and symptoms, but provide a valuable add on tool. Diagnosis should not be based solely on a molecular test, but molecular tools might deliver an important piece of information that helps matching the diagnostic puzzle to a diagnosis, in particular as few tests are in vitro diagnostic tests (IVD) or only part of the whole test carries the IVD certificate (e.g., DNA extraction is often not included). Please be aware that the authors do not claim to provide a complete overview on all commercially available diagnostic assays being currently marketed for fungal detection, as those are subject to constant change. A main focus is put on commonly used panfungal assays and pathogen-specific assays, including Aspergillus-specific, Candida-specific, Cryptococcus specific, Histoplasma-specific, and Pneumocystis-specific assays. Assays are categorized according to their underlying principle in either antigen-detecting or antibody-detecting or DNA-detecting (Fig. 1). Other non-DNA-detecting nucleic acid methods such as FISH and PNA FISH are not summarized in this chapter and an overview on test performance, common false positives, and the clinical evaluation of commercial tests in studies is provided already in a previous book series by Javier Yugueros Marcos and David H. Pincus (Marcos and Pincus, Methods Mol Biol 968:25-54, 2013).

Molecular diagnosis of bloodstream infections in onco-haematology patients with PCR/ESI-MS technology

OBJECTIVES

Onco-haematological patients are prone to develop infections, and antibiotic prophylaxis may lead to negative blood cultures. Thus, the microbiological diagnosis and subsequent administration of a targeted antimicrobial therapy is often difficult. The goal of this study was to evaluate the usefulness of IRIDICA (PCR/ESI-MS technology) for the molecular diagnosis of bloodstream infections in this patient group.

METHODS

A total of 463 whole blood specimens from different sepsis episodes in 429 patients were analysed using the PCR/ESI-MS platform, comparing the results with those of blood culture and other clinically relevant information.

RESULTS

The sensitivity of PCR/ESI-MS by specimen (excluding polymicrobial infections, n = 25) in comparison with blood culture was 64.3% overall, 69.0% in oncological patients, and 59.3% in haematological patients. When comparing with a clinical infection criterion, overall sensitivity rose to 74.7%, being higher in oncological patients (80.0%) than in haematological patients (67.7%). Thirty-one microorganisms isolated by culture were not detected by IRIDICA, whereas 42 clinically relevant pathogens not isolated by culture were detected moleculary.

CONCLUSIONS

PCR/ESI-MS offers a reliable identification of pathogens directly from whole blood. While additional studies are needed to confirm our findings, the system showed a lower sensitivity in onco-haematological patients in comparison with previously reported results in patients from the Intensive Care Unit.

Blood Aspergillus RNA is a promising alternative biomarker for invasive aspergillosis

A critical challenge for the successful application of antifungal therapies for invasive aspergillosis (IA) is a lack of reliable biomarkers to assess early treatment response. Patients with proven or probable IA were prospectively enrolled, and serial blood samples were collected at 8 specified time points during 12-week antifungal therapy. Total nucleic acid was extracted from 2.5 ml blood and tested for Aspergillus-specific RNA by a pan-Aspergillus real-time nucleic acid sequence-based amplification (NASBA) assay. Serum 1, 3-β-D-glucan (BG) and galactomannan (GM) were measured in parallel. Clinical outcome was evaluated at 6 and 12 weeks. Overall, 48/328 (14.6%) blood samples from 29/46 (63%) patients had positive NASBA detection at baseline and/or some point during the study. Positive NASBA results during the first 4 and 6 weeks of treatment are significantly associated with the 12-week outcome. Blood RNA load change during weeks 4-6 may be informative to predict outcome at 12 weeks. While independent of serum GM, the kinetic change of circulating Aspergillus RNA appears to be well correlated with that of BG on some patient individuals. Monitoring blood Aspergillus RNA during the first 4-6 weeks of antifungal treatment may help assess therapeutic response. Combination of circulating Aspergillus RNA and BG may be a useful adjunct to assess response.

Identification of invasive fungal diseases in immunocompromised patients by combining an Aspergillus specific PCR with a multifungal DNA-microarray from primary clinical samples

The increasing incidence of invasive fungal diseases (IFD), most of all invasive aspergillosis (IA) in immunocompromised patients emphasises the need to improve the diagnostic tools for detection of fungal pathogens. We investigated the diagnostic performance of a multifungal DNA-microarray detecting 15 different fungi [Aspergillus, Candida, Fusarium, Mucor, Rhizopus, Scedosporium and Trichosporon species (spp.)] in addition to an Aspergillus specific polymerase chain reaction (PCR) assay. Biopsies, bronchoalveolar lavage and peripheral blood samples of 133 immunocompromised patients (pts) were investigated by a multifungal DNA-microarray as well as a nested Aspergillus specific PCR assay. Patients had proven (n = 18), probable (n = 29), possible (n = 48) and no IFD (n = 38) and were mostly under antifungal therapy at the time of sampling. The results were compared to culture, histopathology, imaging and serology, respectively. For the non-Aspergillus IFD the microarray analysis yielded in all samples a sensitivity of 64% and a specificity of 80%. Best results for the detection of all IFD were achieved by combining DNA-microarray and Aspergillus specific PCR in biopsy samples (sensitivity 79%; specificity 71%). The molecular assays in combination identify genomic DNA of fungal pathogens and may improve identification of causative pathogens of IFD and help overcoming the diagnostic uncertainty of culture and/or histopathology findings, even during antifungal therapy.

Early Changes of Mannose-Binding Lectin, H-Ficolin, and Procalcitonin in Patients with Febrile Neutropenia: A Prospective Observational Study

Objective:

The significance of mannose-binding lectin (MBL) and H-ficolin deficiency in febrile neutropenic (FN) patients and the correlation of these markers along with consecutive C-reactive protein (CRP) and procalcitonin (PCT) levels during the infectious process are investigated.

Materials and Methods:

Patients with any hematological malignancies who were defined to have “microbiologically confirmed infection”, “clinically documented infection”, or “fever of unknown origin” were included in this single-center prospective observational study. Serum levels of CRP, PCT, MBL, and H-ficolin were determined on 3 separate occasions: at baseline (between hospital admission and chemotherapy), at the onset of fever, and at the 72nd hour of fever.

Results:

Forty-six patients (54% male, mean age 41.7 years) with 61 separate episodes of FN were evaluated. Eleven patients (23.9%) had “microbiologically confirmed infection”, 17 (37%) had “clinically documented infection”, and 18 (39.1%) had “fever of unknown origin”. Fourteen (30.4%) patients had low (<500 ng/mL) initial MBL levels and 7 (15.21%) had low (<12,000 ng/mL) H-ficolin levels. Baseline MBL and H-ficolin levels did not significantly change on the first and third days of fever (p=0.076). Gram-negative bacteremia more frequently occurred in those with low initial MBL levels (p=0.006). PCT levels were significantly higher in those with microbiologically documented infections. Mean and median PCT levels were significantly higher in cases with bacteremia. There was no significant difference between hemoculture-positive and-negative patients in terms of CRP levels.

Conclusion:

Monitoring serum H-ficolin levels was shown to be of no benefit in terms of predicting severe infection. Low baseline MBL levels were correlated with high risk of gram-negative bacteremia; however, no significant correlation was shown in the follow-up. Close monitoring of PCT levels is warranted to provide more accurate and specific data while monitoring cases of bacteremia.

Pneumonia in the neutropenic cancer patient

PURPOSE OF REVIEW

Pneumonia is the leading cause of death among neutropenic cancer patients, particularly those with acute leukaemia. Even with empiric therapy, case fatality rates of neutropenic pneumonias remain unacceptably high. However, recent advances in the management of neutropenic pneumonia offer hope for improved outcomes in the cancer setting. This review summarizes recent literature regarding the clinical presentation, microbiologic trends, diagnostic advances and therapeutic recommendations for cancer-related neutropenic pneumonia.

RECENT FINDINGS

Although neutropenic patients acquire pathogens both in community and nosocomial settings, patients' obligate healthcare exposures result in the frequent identification of multidrug-resistant bacterial organisms on conventional culture-based assessment of respiratory secretions. Modern molecular techniques, including expanded use of galactomannan testing, have further facilitated identification of fungal pathogens, allowing for aggressive interventions that appear to improve patient outcomes. Multiple interested societies have issued updated guidelines for antibiotic therapy of suspected neutropenic pneumonia. The benefit of antibiotic medications may be further enhanced by agents that promote host responses to infection.

SUMMARY

Neutropenic cancer patients have numerous potential causes for pulmonary infiltrates and clinical deterioration, with lower respiratory tract infections among the most deadly. Early clinical suspicion, diagnosis and intervention for neutropenic pneumonia provide cancer patients' best hope for survival.

Molecular-based diagnosis of bacteremia in the setting of fever with or without neutropenia in pediatric hematology-oncology patients

BACKGROUND

Prompt evaluation and appropriate treatment with wide-spectrum antibiotics is considered mandatory for febrile oncology patients especially during neutropenia. Central venous catheters are widely used in pediatric oncology patients and are often the source of infections. Patients are usually admitted for follow-up and administration of antibiotics. Aims were to assess the efficacy of the polymerase chain reaction (PCR) method in identifying bacteria in blood samples as compared with standard blood cultures.

METHODS

This was a prospective study, which included all patients with central venous catheters admitted to the pediatric hematology-oncology department over the 14-month period. Demographic, clinical, and laboratory variables were compared in bacteremic and nonbacteremic patients. Standard microbiological cultures were compared using the PCR technique.

RESULTS

From September 2004 to November 2005, 148 blood cultures (70 patients) were evaluated. Positive blood cultures were detected on 21 (18.3%) occasions. PCR had sensitivity of 46%, specificity of 98%, positive predictive value 86%, and negative predictive value 89%. The PCR identified fastidious bacteria in 2 occasions when standard cultures were negative.

CONCLUSIONS

Inspite of low sensitivity, PCR may help with early identification of bacteremia. Improving this technology is warranted.

Diagnostic methods for invasive fungal diseases in patients with hematologic malignancies

Invasive fungal disease is associated with increased morbidity and mortality in hematologic malignancy patients and hematopoietic stem cell transplant recipients. Timely recognition and treatment of invasive fungal diseases in these patients are essential and decrease mortality. However, conventional definitive diagnostic methods are difficult and time consuming. While conventional microbiological and histopathological methods are still needed for a definitive diagnosis of invasive fungal disease, new noninvasive diagnostic methods including serologic and molecular biomarkers are now available. These new diagnostic methods facilitate an early diagnosis of invasive fungal disease and allow for utilization of a pre-emptive treatment approach, which may ultimately lead to improved treatment outcomes and reduced toxicity.

Laboratory diagnosis of invasive aspergillosis: from diagnosis to prediction of outcome

Invasive aspergillosis (IA), an infection caused by fungi in the genus Aspergillus, is seen in patients with immunological deficits, particularly acute leukaemia and stem cell transplantation, and has been associated with high rates of mortality in previous years. Diagnosing IA has long been problematic owing to the inability to culture the main causal agent A. fumigatus from blood. Microscopic examination and culture of respiratory tract specimens have lacked sensitivity, and biopsy tissue for histopathological examination is rarely obtainable. Thus, for many years there has been a great interest in nonculture-based techniques such as the detection of galactomannan, β -D-glucan, and DNA by PCR-based methods. Recent meta-analyses suggest that these approaches have broadly similar performance parameters in terms of sensitivity and specificity to diagnose IA. Improvements have been made in our understanding of the limitations of antigen assays and the standardisation of PCR-based DNA detection. Thus, in more recent years, the debate has focussed on how these assays can be incorporated into diagnostic strategies to maximise improvements in outcome whilst limiting unnecessary use of antifungal therapy. Furthermore, there is a current interest in applying these tests to monitor the effectiveness of therapy after diagnosis and predict clinical outcomes. The search for improved markers for the early and sensitive diagnosis of IA continues to be a challenge.

Fungal diagnostics: review of commercially available methods

Fungi and yeasts are critical causes of acute infection. As such, the detection and identification of these organisms are crucial in the diagnosis of affected patient populations. There is a vast array of commercial tests currently available for diagnostic purposes. These vary from traditional culture and biochemical methods to advanced multiparameter molecular tests. Recent technological advances have driven the development of rapid tests which are complementing and in some cases replacing the more traditional methods of detection. Irrespective of the method used the ultimate goal is timely detection of the infectious agent allowing appropriate treatment and improved outcome for the patient.

Role of molecular diagnostics in the management of infectious disease emergencies

In the setting of infectious disease emergencies, rapid and accurate identification of the causative agent is critical to optimizing antimicrobial therapy in a timely manner. It is clearly evident that the age of molecular diagnostics is now upon us, with real-time PCR becoming the standard of diagnosis for many infectious disease emergencies in either monoplex or multiplex format. Other molecular techniques such as whole or partial genome sequencing, microarrays, broad-range PCR, restriction fragment length polymorphisms, and molecular typing are also being used. However, for most small clinical laboratories, implementation of these advanced molecular techniques is not feasible owing to the high cost of instrumentation and reagents. If these tests are not available in-house, samples can be sent to national reference laboratories (eg, Mayo Medical Laboratories and Quest Diagnostics) for real-time PCR assays that can be completed in 1 day. It is anticipated that over time commercial real-time PCR tests and instrumentation will become more standardized and affordable, allowing individual laboratories to conduct tests locally, thus further reducing turnaround time. Although real-time PCR has been proved to expand our diagnostic capability, it must be stressed that such molecular methodology constitutes only an additional tool in the diagnosis of infectious diseases in emergency situations. Phenotypic methodologies (staining, cultures, biochemical tests, and serology) still play a critical role in identifying, confirming, and providing antibiotic susceptibility testing for many microbial pathogens. As multiplex assays become increasingly available, there will be even greater temptation for taking a “shotgun” approach to diagnostic testing. These new technologies will not substitute for a proper history and physical examination leading to a thoughtful differential diagnosis. None the less, these new molecular tests increase the capability of the diagnostician to rapidly identify the microbiological etiology of an infection. An added advantage of rapid diagnostic tests often not emphasized is the capability to rule out certain diagnoses for which unnecessary antimicrobial therapy may otherwise be instituted and/or continued.

Bidirectional crosstalk between platelets and monocytes initiated by Toll-like receptor: an important step in the early defense against fungal infections?

Monocytes are important in the defense against fungal infections due to their phagocytic and immunoregulatory functions. Platelets also contribute in such immune responses through their release of soluble mediators, including chemokines as well as several other soluble mediators. Both monocytes and platelets express several Toll-like receptors (TLRs) that can recognize fungal molecules and thus initiate intracellular signaling events. TLR ligation on monocytes and platelets may thereby be an early immunological event and function as an initiator of a local proinflammatory crosstalk between platelets and monocytes resulting in (i) monocyte-induced increase of platelet activation and (ii) platelet-associated enhancement of the monocyte activation/function. These effects may have clinical implications both for the efficiency of antifungal treatment and for the predisposition to fungal infections, for example, increased predisposition in patients with thrombocytopenia/monocytopenia due to chemotherapy- or disease-induced bone marrow failure.

Invasive mycoses: diagnostic challenges

Despite the availability of newer antifungal drugs, outcomes for patients with invasive fungal infections (IFIs) continue to be poor, in large part due to delayed diagnosis and initiation of appropriate antifungal therapy. Standard histopathologic diagnostic techniques are often untenable in at-risk patients, and culture-based diagnostics typically are too insensitive or nonspecific, or provide results after too long a delay for optimal IFI management. Newer surrogate markers of IFIs with improved sensitivity and specificity are needed to enable earlier diagnosis and, ideally, to provide prognostic information and/or permit therapeutic monitoring. Surrogate assays should also be accessible and easy to implement in the hospital. Several nonculture-based assays of newer surrogates are making their way into the medical setting or are currently under investigation. These new or up-and-coming surrogates include antigens/antibodies (mannan and antimannan antibodies) or fungal metabolites (d-arabinitol) for detection of invasive candidiasis, the Aspergillus cell wall component galactomannan used to detect invasive aspergillosis, or the fungal cell wall component and panfungal marker β-glucan. In addition, progress continues with use of polymerase chain reaction- or other nucleic acid- or molecular-based assays for diagnosis of either specific or generic IFIs, although the various methods must be better standardized before any of these approaches can be more fully implemented into the medical setting. Investigators are also beginning to explore the possibility of combining newer surrogate markers with each other or with more standard diagnostic approaches to improve sensitivity, specificity, and capacity for earlier diagnosis, at a time when fungal burden is still relatively low and more responsive to antifungal therapy.

Fungal pneumonia in patients with hematologic malignancies: current approach and management

PURPOSE OF REVIEW

Fungal pneumonia is the most frequent presentation of invasive mold infections (IMIs) in patients with hematologic malignancies. In this review, we summarize recent advances in the epidemiology, diagnosis, and treatment of fungal pneumonia and improvement in the outcome of such patients.

RECENT FINDINGS

The epidemiology of IMIs in hematopoietic stem cell transplant recipients has evolved in response to changes in conditioning regimens, increasing use of alternative sources of stem cells and antifungal prophylaxis, among other factors. PCR analysis and serologic tests, used in combination with imaging findings, have improved the timing and accuracy of diagnosis of these infections.Recent guidelines incorporated evidence-based treatment recommendations; however, application in real world situations is often difficult. A new treatment approach known as preemptive therapy, based on screening with biomarkers combined with early clinical and imaging findings, is being compared with the traditional empirical therapy in neutropenic patients with persistent or recurrent fever. The use of new triazoles and prompt diagnosis has contributed to improved outcomes in these patients. In addition, therapeutic drug monitoring may be useful when administering voriconazole.

SUMMARY

Evidence-based diagnosis and treatment of fungal pneumonia in patients with hematologic malignancies are becoming increasingly institution-specific and patient-specific, integrating host factors, new diagnostic methods, and epidemiologic and pharmacologic considerations.

Recent advances in molecular technologies and their application in pathogen detection in foods with particular reference to yersinia

Yersinia enterocolitica is an important zoonotic pathogen that can cause yersiniosis in humans and animals. Food has been suggested to be the main source of yersiniosis. It is critical for the researchers to be able to detect Yersinia or any other foodborne pathogen with increased sensitivity and specificity, as well as in real-time, in the case of a foodborne disease outbreak. Conventional detection methods are known to be labor intensive, time consuming, or expensive. On the other hand, more sensitive molecular-based detection methods like next generation sequencing, microarray, and many others are capable of providing faster results. DNA testing is now possible on a single molecule, and high-throughput analysis allows multiple detection reactions to be performed at once, thus allowing a range of characteristics to be rapidly and simultaneously determined. Despite better detection efficiencies, results derived using molecular biology methods can be affected by the various food matrixes. With the improvements in sample preparation, data analysis, and testing procedures, molecular detection techniques will likely continue to simplify and increase the speed of detection while simultaneously improving the sensitivity and specificity for tracking pathogens in food matrices.

Neurologic infectious disease emergencies

Nearly 70 years after the discovery of penicillin, neurologic infectious diseases (NIDs) remain an important worldwide source of morbidity and mortality. The clinician faced with a potential NID must urgently consider patient demographics, pace of illness and clinical syndrome, and laboratory data. In keeping with the topics of this issue, initial emergency diagnosis and management are emphasized, with appropriate references to relevant literature for subsequent longer-term interventions.

Invasive Candida infections in solid organ transplant recipient children

Solid organ transplantation (SOT) is now an accepted therapy for many end-stage organ disorders and fungal infections are the principal cause of infection-related mortality in SOT recipients. Among invasive fungal infections, Candida species are the most common pathogens identified, associated with high mortality rates. The epidemiology and clinical manifestations of Candida infections vary with the type of organ transplantation. This article reviews invasive Candida infections in pediatric SOT recipients.