Diagnostic system for rapid and sensitive differential detection of pathogens

A multicenter virome analysis of blood, feces, and saliva in myalgic encephalomyelitis/chronic fatigue syndrome

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is estimated to affect 0.4%-2.5% of the global population. Most cases are unexplained; however, some patients describe an antecedent viral infection or response to antiviral medications. We report here a multicenter study for the presence of viral nucleic acid in blood, feces, and saliva of patients with ME/CFS using polymerase chain reaction and high-throughput sequencing. We found no consistent group-specific differences other than a lower prevalence of anelloviruses in cases compared to healthy controls. Our findings suggest that future investigations into viral infections in ME/CFS should focus on adaptive immune responses rather than surveillance for viral gene products.

Fluorescent Biosensor Based on Hairpin DNA Stabilized Copper Nanoclusters for Chlamydia trachomatis Detection

Chlamydia trachomatis (C. trachomatis) is a kind of intracellular parasitic microorganism, which can causes many diseases such as trachoma. In this strategy, a specific hairpin DNA with the probe loop as specific regions to recognize C. trachomatis DNA with strong affinity was designed, and its stem consisted of 24 AT base pairs as an effective template for hairpin DNA-CuNCs formation. In the absence of C. trachomatis DNA, the detection system showed strong orange fluorescence emission peaks at 606 nm. In the presence of C. trachomatis DNA, the conformation of DNA probe changed after hybridizing with C. trachomatis DNA. Then, the amount of hairpin DNA-CuNCs was reduced and resulted in low fluorescence emission. C. trachomatis DNA displayed a significant inhibitory effect on the synthesis of fluorescent hairpin DNA-CuNCs due to the competition between C. trachomatis DNA and the specific hairpin DNA. Under the optimal experimental conditions, different concentrations of C. trachomatis were tested and the results showed a good linear relationship in the range of 50 nM to 950 nM. Moreover, the detection limit was 18.5 nM and this detection method possessed good selectivity. Finally, the fluorescent biosensor had been successfully applied to the detection of C. trachomatis target sequence in HeLa cell lysate, providing a new strategy for the detection of C. trachomatis.

Infant Nasopharyngeal Microbiota Subphenotypes and Early Childhood Lung Function: Evidence from a Rural Ghanaian Pregnancy Cohort

Early life respiratory microbiota may increase risk for future pulmonary disease. Associations between respiratory microbiota and lung health in children from low- and middle-income countries are not well-described. Leveraging the Ghana Randomized Air Pollution and Health Study (GRAPHS) prospective pregnancy cohort in Kintampo, Ghana, we collected nasopharyngeal swabs in 112 asymptomatic children aged median 4.3 months (interquartile range (IQR) 2.9, 7.1) and analyzed 22 common bacterial and viral pathogens with MassTag polymerase chain reaction (PCR). We prospectively followed the cohort and measured lung function at age four years by impulse oscillometry. First, we employed latent class analysis (LCA) to identify nasopharyngeal microbiota (NPM) subphenotypes. Then, we used linear regression to analyze associations between subphenotype assignment and lung function. LCA suggest that a two-class model best described the infant NPM. We identified a higher diversity subphenotype (N = 38, 34%) with more pathogens (median 4; IQR 3.25, 4.75) and a lower diversity subphenotype (N = 74, 66%) with fewer pathogens (median 1; IQR 1, 2). In multivariable linear regression models, the less diverse NPM subphenotype had higher small airway resistance (R5-R20 β = 17.9%, 95% CI 35.6, 0.23; p = 0.047) compared with the more diverse subphenotype. Further studies are required to understand the role of the microbiota in future lung health.

Screening for Viral Infections

This article reviews methods for diagnosis of viral infections including histopathology, culture, nucleic acid tests, and serology. We discuss the principles that underlie individual assays as well as their strengths and limitations. Our intent is to provide insights into selecting strategies for viral diagnosis and discovery that can be pursued by accessing more detailed and granular protocols.

Advances in laboratory assays for detecting human metapneumovirus

Human metapneumovirus (HMPV) is one of the major causes of acute respiratory tract infection (ARI) and shows high morbidity and mortality, particularly in children and immunocompromised patients. Various methods for detecting HMPV have been developed and applied in clinical laboratories. When reviewing the literature, we found that polymerase chain reaction (PCR)-based assays have been most frequently and consistently used to detect HMPV. The most commonly used method was multiplex reverse transcriptase-PCR (RT-PCR; 57.4%), followed by real-time RT-PCR (38.3%). Multiplex RT-PCR became the more popular method in 2011-2019 (69.7%), in contrast to 2001-2009 (28.6%). The advent of multiplex PCR in detecting broader viral pathogens in one run and coinfected viruses influenced the change in user preference. Further, newly developed microarray technologies and ionization mass spectrometry were introduced in 2011-2019. Viral culture (including shell vial assays) and fluorescent immunoassays (with or without culture) were once the mainstays. However, the percentage of studies employing culture and fluorescent immunoassays decreased from 21.4% in 2001-2010 to 15.2% in 2011-2019. Meanwhile, the use of PCR-based methods of HMPV detection increased from 78.6% in 2001-2010 to 84.8% in 2011-2019. The increase in PCR-based methods might have occurred because PCR methods demonstrated better diagnostic performance, shorter hands-on and run times, less hazards to laboratory personnel, and more reliable results than traditional methods. When using these assays, it is important to acquire a comprehensive understanding of the principles, advantages, disadvantages, and precautions for data interpretation. In the future, the combination of nanotechnology and advanced genetic platforms such as next-generation sequencing will benefit patients with HMPV infection by facilitating efficient therapeutic intervention. Analytical and clinical validation are required before using new techniques in clinical laboratories.

Examining the relationship between household air pollution and infant microbial nasal carriage in a Ghanaian cohort

BACKGROUND

Pneumonia, a leading cause of childhood mortality, is associated with household air pollution (HAP) exposure. Mechanisms between HAP and pneumonia are poorly understood, but studies suggest that HAP may increase the likelihood of bacterial, instead of viral, pneumonia. We assessed the relationship between HAP and infant microbial nasal carriage among 260 infants participating in the Ghana Randomized Air Pollution and Health Study (GRAPHS).

METHODS

Data are from GRAPHS, a cluster-randomized controlled trial of cookstove interventions (improved biomass or LPG) versus the 3-stone (baseline) cookstove. Infants were surveyed for pneumonia during the first year of life and had routine personal exposure assessments. Nasopharyngeal swabs collected from pneumonia cases (n = 130) and healthy controls (n = 130) were analyzed for presence of 22 common respiratory microbes by MassTag polymerase chain reaction. Data analyses included intention-to-treat (ITT) comparisons of microbial species presence by study arm, and exposure-response relationships.

RESULTS

In ITT analyses, 3-stone arm participants had a higher mean number of microbial species than the LPG (LPG: 2.71, 3-stone: 3.34, p < 0.0001, n = 260). This difference was driven by increased bacterial (p < 0.0001) rather than viral species presence (non-significant). Results were pronounced in pneumonia cases and attenuated in healthy controls. Higher prevalence bacterial species were Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis. Exposure-response relationships did not yield significant associations between measured CO and nasal microbial carriage.

CONCLUSIONS

Our intention-to-treat findings are consistent with a link between HAP and bacterial nasal carriage. No relationships were found for viral carriage. Given the null results in exposure-response analysis, it is likely that a pollutant besides CO is driving these differences.

Precise, direct, and rapid detection of Shigella Spa gene by a novel unmodified AuNPs-based optical genosensing system

Early detection of infectious bacteria is a necessity for combating infectious diseases. Due to low infectious dose of Shigella, rapid and sensitive detection is needed. Compared to the presented genes, Spa gene can be introduced as a novel sequence for all species of Shigella detection. Herein, the possibility of Spa genes for detection of four species of Shigella was investigated for the first time by AuNPs-based optical genosensing system. In this method, AuNP-DNA probes were hybridized with Spa gene sequence. When the complementary target is present, it prevents the aggregation of the complex under acid environment and the solution remains red whereas in the absence of the specific sequence, it turns to purple. Therefore, visual detection is possible with bare eye. The comparison of this Optical DNA biosensor and PCR-based method showed that the proposed method is simple, cost-effective, rapid operation, with high or comparable detection limit of (LOD and LOQ: 8.14 and 26.6 ng mLl^-1, respectively), without need of any expensive techniques, and equipments compared to the conventional methods. In conclusion, the described method may develop into a platform that could be utilized for detection of various bacterial species with high accuracy and prompt screening of samples.

A highly multiplexed broad pathogen detection assay for infectious disease diagnostics

Rapid pathogen identification during an acute febrile illness is a critical first step for providing appropriate clinical care and patient isolation. Primary screening using sensitive and specific assays, such as real-time PCR and ELISAs, can rapidly test for known circulating infectious diseases. If the initial testing is negative, potentially due to a lack of developed diagnostic assays or an incomplete understanding of the pathogens circulating within a geographic region, additional testing would be required including highly multiplexed assays and metagenomic next generation sequencing. To bridge the gap between rapid point of care diagnostics and sequencing, we developed a highly multiplexed assay designed to detect 164 different viruses, bacteria, and parasites using the NanoString nCounter platform. Included in this assay were high consequence pathogens such as Ebola virus, highly endemic organisms including several Plasmodium species, and a large number of less prevalent pathogens to ensure a broad coverage of potential human pathogens. Evaluation of this panel resulted in positive detection of 113 (encompassing 98 different human pathogen types) of the 126 organisms available to us including the medically important Ebola virus, Lassa virus, dengue virus serotypes 1–4, Chikungunya virus, yellow fever virus, and Plasmodium falciparum. Overall, this assay could improve infectious disease diagnostics and biosurveillance efforts as a quick, highly multiplexed, and easy to use pathogen screening tool.

Identifying the causative agent in an acute febrile illness can be challenging diagnostically, especially when organisms in a particular region have overlapping clinical presentation or when that pathogen’s presence is unexpected. Ebola virus, for example, was not considered in an acute febrile illness differential diagnosis in West Africa until the explosive outbreak in 2013 presented the risk of infection. Besides the cost and time of screening a single patient sample for a large number of pathogens, limited sample volumes place further restrictions on what assays can be applied. Here, we developed a broad pathogen screening assay targeting 164 different human pathogens and show positive detection of over 100 of the organisms on the panel including Ebola virus, Plasmodium falciparum, and a large number of rare pathogens. The hands on time and sample volume requirement is minimal. The assay performed well in mock clinical and human clinical samples, demonstrating the clinical utility of this assay in cases where the initial diagnostic testing results in negative results. Our results provide a framework for further validation studies that would be required for formal clinical diagnostic applications.

Parvovirus B19 Infection in Children With Arterial Ischemic Stroke

BACKGROUND AND PURPOSE

Case-control studies suggest that acute infection transiently increases the risk of childhood arterial ischemic stroke. We hypothesized that an unbiased pathogen discovery approach utilizing MassTag-polymerase chain reaction would identify pathogens in the blood of childhood arterial ischemic stroke cases.

METHODS

The multicenter international VIPS study (Vascular Effects of Infection in Pediatric Stroke) enrolled arterial ischemic stroke cases, and stroke-free controls, aged 29 days through 18 years. Parental interview included questions on recent infections. In this pilot study, we used MassTag-polymerase chain reaction to test the plasma of the first 161 cases and 34 controls enrolled for a panel of 28 common bacterial and viral pathogens.

RESULTS

Pathogen DNA was detected in no controls and 14 cases (8.7%): parvovirus B19 (n=10), herpesvirus 6 (n=2), adenovirus (n=1), and rhinovirus 6C (n=1). Parvovirus B19 infection was confirmed by serologies in all 10; infection was subclinical in 8. Four cases with parvovirus B19 had underlying congenital heart disease, whereas another 5 had a distinct arteriopathy involving a long-segment stenosis of the distal internal carotid and proximal middle cerebral arteries.

CONCLUSIONS

Using MassTag-polymerase chain reaction, we detected parvovirus B19-a virus known to infect erythrocytes and endothelial cells-in some cases of childhood arterial ischemic stroke. This approach can generate new, testable hypotheses about childhood stroke pathogenesis.

Evaluation of a TaqMan Array Card for Detection of Central Nervous System Infections

Infections of the central nervous system (CNS) are often acute, with significant morbidity and mortality. Routine diagnosis of such infections is limited in developing countries and requires modern equipment in advanced laboratories that may be unavailable to a number of patients in sub-Saharan Africa. We developed a TaqMan array card (TAC) that detects multiple pathogens simultaneously from cerebrospinal fluid. The 21-pathogen CNS multiple-pathogen TAC (CNS-TAC) assay includes two parasites (Balamuthia mandrillaris and Acanthamoeba), six bacterial pathogens (Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis, Mycoplasma pneumoniae, Mycobacterium tuberculosis, and Bartonella), and 13 viruses (parechovirus, dengue virus, Nipah virus, varicella-zoster virus, mumps virus, measles virus, lyssavirus, herpes simplex viruses 1 and 2, Epstein-Barr virus, enterovirus, cytomegalovirus, and chikungunya virus). The card also includes human RNase P as a nucleic acid extraction control and an internal manufacturer control, GAPDH (glyceraldehyde-3-phosphate dehydrogenase). This CNS-TAC assay can test up to eight samples for all 21 agents within 2.5 h following nucleic acid extraction. The assay was validated for linearity, limit of detection, sensitivity, and specificity by using either live viruses (dengue, mumps, and measles viruses) or nucleic acid material (Nipah and chikungunya viruses). Of 120 samples tested by individual real-time PCR, 35 were positive for eight different targets, whereas the CNS-TAC assay detected 37 positive samples across nine different targets. The CNS-TAC assays showed 85.6% sensitivity and 96.7% specificity. Therefore, the CNS-TAC assay may be useful for outbreak investigation and surveillance of suspected neurological disease.

Microbiome of the paranasal sinuses: Update and literature review

BACKGROUND

Our understanding of the resident microbiome of the paranasal sinuses has changed considerably in recent years. Once presumed to be sterile, healthy sinus cavities are now known to harbor a diverse assemblage of microorganisms, and, it is hypothesized that alterations in the kinds and quantities of these microbes may play a role in the pathogenesis of chronic rhinosinusitis (CRS).

OBJECTIVES

To review the current literature regarding the sinus microbiome and collate research findings from relevant studies published to date.

METHODS

A systematic literature review was performed on all molecular studies that investigated the microbial communities of the paranasal sinuses. Methods of detection, microbiome composition, and comparative profiling between patients with and without CRS were explored.

RESULTS

A complex consortium of microorganisms has been demonstrated in the sinuses of both patients with and without CRS. However, the latter generally have been characterized by reduced biodiversity compared with controls, with selective enrichment of particular microbes (e.g., Staphylococcus aureus). Such disruptions in the resident microbiome may contribute to disease pathogenesis by enhancing the virulence of potential pathogens and adversely modulating immune responses.

CONCLUSION

The advent of culture-independent molecular approaches has led to a greater appreciation of the intricate microbial ecology of the paranasal sinuses. Microbiota composition, distribution, and abundance impact mucosal health and influence pathogen growth and function. A deeper understanding of the host-microbiome relationship and its constituents may encourage development of new treatment paradigms for CRS, which target restoration of microbiome homeostasis and cultivation of optimal microbial communities.

Isolation of an Enterovirus D68 from Blood from a Child with Pneumonia in Rural Haiti: Close Phylogenetic Linkage with New York Strain

We report the detection and isolation of enterovirus D68 from the blood of a 6-year-old child in rural Haiti, who presented with high fever and clinical signs suggestive of pneumonia. On phylogenetic analysis, this Haitian isolate was virtually identical to an enterovirus D68 strain circulating in New York during the same time period.

Arbovirus and insect-specific virus discovery in Kenya by novel six genera multiplex high-resolution melting analysis

A broad diversity of arthropod-borne viruses (arboviruses) of global health concern are endemic to East Africa, yet most surveillance efforts are limited to just a few key viral pathogens. Additionally, estimates of arbovirus diversity in the tropics are likely to be underestimated as their discovery has lagged significantly over past decades due to limitations in fast and sensitive arbovirus identification methods. Here, we developed a nearly pan-arbovirus detection assay that uses high-resolution melting (HRM) analysis of RT-PCR products from highly multiplexed assays to differentiate broad diversities of arboviruses. We differentiated 15 viral culture controls and seven additional synthetic viral DNA sequence controls, within Flavivirus, Alphavirus, Nairovirus, Phlebovirus, Orthobunyavirus and Thogotovirus genera. Among Bunyamwera, sindbis, dengue and Thogoto virus serial dilutions, detection by multiplex RT-PCR-HRM was comparable to the gold standard Vero cell plaque assays. We applied our low-cost method for enhanced broad-range pathogen surveillance from mosquito samples collected in Kenya and identified diverse insect-specific viruses, including a new clade in anopheline mosquitoes, and Wesselsbron virus, an arbovirus that can cause viral haemorrhagic fever in humans and has not previously been isolated in Kenya, in Culex spp. and Anopheles coustani mosquitoes. Our findings demonstrate how multiplex RT-PCR-HRM can identify novel viral diversities and potential disease threats that may not be included in pathogen detection panels of routine surveillance efforts. This approach can be adapted to other pathogens to enhance disease surveillance and pathogen discovery efforts, as well as the study of pathogen diversity and viral evolutionary ecology.

Tuberculous meningitis is a major cause of mortality and morbidity in adults with central nervous system infections in Kota Kinabalu, Sabah, Malaysia: an observational study

BACKGROUND

Central nervous system (CNS) infections are a significant contributor to morbidity and mortality globally. However, most published studies have been conducted in developed countries where the epidemiology and aetiology differ significantly from less developed areas. Additionally, there may be regional differences due to variation in the socio-economic levels, public health services and vaccination policies. Currently, no prospective studies have been conducted in Sabah, East Malaysia to define the epidemiology and aetiology of CNS infections. A better understanding of these is essential for the development of local guidelines for diagnosis and management.

METHODS

We conducted a prospective observational cohort study in patients aged 12 years and older with suspected central nervous system infections at Queen Elizabeth Hospital, Kota Kinabalu, Sabah, Malaysia between February 2012 and March 2013. Cerebrospinal fluid was sent for microscopy, biochemistry, bacterial and mycobacterial cultures, Mycobacterium tuberculosis polymerase chain reaction (PCR), and multiplex and MassCode PCR for various viral and bacterial pathogens.

RESULTS

A total of 84 patients with clinically suspected meningitis and encephalitis were enrolled. An aetiological agent was confirmed in 37/84 (44 %) of the patients. The most common diagnoses were tuberculous meningitis (TBM) (41/84, 48.8 %) and cryptococcal meningoencephalitis (14/84, 16.6 %). Mycobacterium tuberculosis was confirmed in 13/41 (31.7 %) clinically diagnosed TBM patients by cerebrospinal fluid PCR or culture. The acute case fatality rate during hospital admission was 16/84 (19 %) in all patients, 4/43 (9 %) in non-TBM, and 12/41 (29 %) in TBM patients respectively (p = 0.02).

CONCLUSION

TBM is the most common cause of CNS infection in patients aged 12 years or older in Kota Kinabalu, Sabah, Malaysia and is associated with high mortality and morbidity. Further studies are required to improve the management and outcome of TBM.

Development of a Rapid Point-of-Use DNA Test for the Screening of Genuity® Roundup Ready 2 Yield® Soybean in Seed Samples

Testing for the presence of genetically modified material in seed samples is of critical importance for all stakeholders in the agricultural industry, including growers, seed manufacturers, and regulatory bodies. While rapid antibody-based testing for the transgenic protein has fulfilled this need in the past, the introduction of new variants of a given transgene demands new diagnostic regimen that allows distinguishing different traits at the nucleic acid level. Although such molecular tests can be performed by PCR in the laboratory, their requirement for expensive equipment and sophisticated operation have prevented its uptake in point-of-use applications. A recently developed isothermal DNA amplification technique, recombinase polymerase amplification (RPA), combines simple sample preparation and amplification work-flow procedures with the use of minimal detection equipment in real time. Here, we report the development of a highly sensitive and specific RPA-based detection system for Genuity Roundup Ready 2 Yield (RR2Y) material in soybean (Glycine max) seed samples and present the results of studies applying the method in both laboratory and field-type settings.

Diagnostics and Discovery in Viral Central Nervous System Infections

The range of viruses implicated in central nervous system disease continues to grow with globalization of travel and trade, emergence and reemergence of zoonoses and investments in discovery science. Diagnosis of viral central nervous system infections is challenging in that brain tissue, where the pathogen concentration is likely to be highest, is not readily obtained and sensitive methods for molecular and serological detection of infection are not available in most clinical microbiology laboratories. Here we review these challenges and discuss how they may be addressed using advances in molecular, proteomic and immunological methods.

Laboratory Methods for Determining Etiology of Neonatal Infection at Population-based Sites in South Asia: The ANISA Study

BACKGROUND

The Aetiology of Neonatal Infection in South Asia (ANISA) study aims to determine the etiology of neonatal infections in 5 population-based sites in Bangladesh, India and Pakistan.

METHODS

The main laboratory challenges in ANISA were selection and consistent implementation of laboratory methods at participating sites with varied infrastructure. The other specific challenges included (1) specimen collection and transport to designated study laboratories and timely processing in rural settings; (2) minimal or nonexistent laboratory facilities at the field sites; (3) obtaining sufficient volumes of blood from enrolled infants aged 0-59 days and (4) caregivers' concerns about collection of clinical specimens from young infants. An additional challenge was selecting an appropriate molecular platform from multiple available options, all with limited field validation, for use in determining infection in young infants.

CONCLUSIONS

This article describes how the challenges of specimen collection, transport and processing and implementation of laboratory methods have been addressed in the ANISA study. It also describes the measures taken to improve detection of microorganisms causing young infant infections by enhancing the sensitivity of existing laboratory methods for pathogen detection.

Application of a multiplex PCR assay for the detection of gastrointestinal pathogens in a rural African setting

BACKGROUND

Despite high morbidity and mortality, the laboratory diagnosis of gastrointestinal infections is largely neglected in tropical African settings. This study aims to apply the Luminex multiplex PCR assay for the diagnosis of gastrointestinal pathogens in rural Ghana to evaluate its usefulness as a routine method.

METHODS

A case-control study was conducted at the Agogo Presbyterian Hospital in Ghana. Stool samples were collected from children below 6 years of age with (cases) and without (controls) diarrhoea. Samples were screened for 15 different diarrhoeal pathogens by the Luminex xTAG GPP assay and associations between diarrhoea and gastrointestinal infections and fractions attributable to diarrhea (AF) were determined.

RESULTS

The Luminex PCR assay identified organisms in 96.6% (n = 428) of 443 cases and in 92.5% (n = 221) of 239 selected controls. A mean of 2.5 (standard deviation [SD]: ± 1.3) and 2.3 (SD: ± 1.3) organisms per sample were detected in cases and controls respectively. An association with diarrhoea was found for rotavirus (adjusted odds ratio [aOR] = 7.2; 95% confidence interval [CI]: 2.9-18.1), norovirus (aOR = 2.7; 95% CI: 1.4-5.3) and Shigella spp. (aOR = 1.7; 95% CI: 1.2-2.4) with respective AFs of 12.5% (95% CI: 9.6-15.3), 7.9% (95% CI: 3.8-11.7) and 16.9% (95% CI: 6.9-25.9).

CONCLUSION

The high proportion of pathogen-positive stool samples with a high number of co-infections in cases and controls suggests a substantial amount of transient or colonizing microorganisms for which treatment is not necessarily implicated. The use of sequential diagnostic algorithms with pathogen specific or quantitative PCRs might be most appropriate for diagnosing gastrointestinal infections.

Molecular Survey of Zoonotic Agents in Rodents and Other Small Mammals in Croatia

Croatia is a focus for many rodent-borne zoonosis. Here, we report a survey of 242 rodents and small mammals, including 43 Myodes glareolus, 131 Apodemus flavicollis, 53 Apodemus agrarius, three Apodemus sylvaticus, six Sorex araneus, four Microtus arvalis, one Microtus agrestis, and one Muscardinus avellanarius, collected at eight sites in Croatia over an 8-year period. Multiplex MassTag polymerase chain reaction (PCR) was used for detection of Borrelia, Rickettsia, Bartonella, Babesia, Ehrlichia, Anaplasma, Francisella tularensis, and Coxiella burnetii. Individual PCR assays were used for detection of Leptospira, lymphocytic choriomeningitis virus, orthopoxviruses, flaviviruses, hantaviruses, and Toxoplasma gondii. Of the rodents, 52 (21.5%) were infected with Leptospira, 9 (3.7%) with Borrelia miyamotoi, 5 (2%) with Borrelia afzelii, 29 (12.0%) with Bartonella, 8 (3.3%) with Babesia microti, 2 (0.8%) with Ehrlichia, 4 (1.7%) with Anaplasma, 2 (0.8%) with F. tularensis, 43 (17.8%) with hantaviruses, and 1 (0.4%) with an orthopoxvirus. Other agents were not detected. Multiple infections were found in 32 rodents (13.2%): dual infections in 26 rodents (10.7%), triple infections in four rodents (2.9%), and quadruple infections in two rodents (0.8%). Our findings indicate that rodents in Croatia harbor a wide range of bacteria and viruses that are pathogenic to humans.

Virome Capture Sequencing Enables Sensitive Viral Diagnosis and Comprehensive Virome Analysis

Insensitivity and technical complexity have impeded the implementation of high-throughput nucleic acid sequencing in differential diagnosis of viral infections in clinical laboratories. Here, we describe the development of a virome capture sequencing platform for vertebrate viruses (VirCapSeq-VERT) that increases the sensitivity of sequence-based virus detection and characterization. The system uses ~2 million probes that cover the genomes of members of the 207 viral taxa known to infect vertebrates, including humans. A biotinylated oligonucleotide library was synthesized on the NimbleGen cleavable array platform and used for solution-based capture of viral nucleic acids present in complex samples containing variable proportions of viral and host nucleic acids. The use of VirCapSeq-VERT resulted in a 100- to 10,000-fold increase in viral reads from blood and tissue homogenates compared to conventional Illumina sequencing using established virus enrichment procedures, including filtration, nuclease treatments, and RiboZero rRNA subtraction. VirCapSeq-VERT had a limit of detection comparable to that of agent-specific real-time PCR in serum, blood, and tissue extracts. Furthermore, the method identified novel viruses whose genomes were approximately 40% different from the known virus genomes used for designing the probe library. The VirCapSeq-VERT platform is ideally suited for analyses of virome composition and dynamics.

Importance  VirCapSeq-VERT enables detection of viral sequences in complex sample backgrounds, including those found in clinical specimens, such as serum, blood, and tissue. The highly multiplexed nature of the system allows both the simultaneous identification and the comprehensive genetic characterization of all known vertebrate viruses, their genetic variants, and novel viruses. The operational simplicity and efficiency of the VirCapSeq-VERT platform may facilitate transition of high-throughput sequencing to clinical diagnostic as well as research applications.

VirCapSeq-VERT enables detection of viral sequences in complex sample backgrounds, including those found in clinical specimens, such as serum, blood, and tissue. The highly multiplexed nature of the system allows both the simultaneous identification and the comprehensive genetic characterization of all known vertebrate viruses, their genetic variants, and novel viruses. The operational simplicity and efficiency of the VirCapSeq-VERT platform may facilitate transition of high-throughput sequencing to clinical diagnostic as well as research applications.

Evaluation of a multiplex polymerase chain reaction for early diagnosis of ventriculostomy-related infections

OBJECT

Diagnosis of ventriculostomy-related infections (VRIs) is challenging due to the lack of rapid, sensitive assays for pathogen detection. The authors report the development of a multiplex polymerase chain reaction (PCR) assay for differential diagnosis of common VRI pathogens.

METHODS

MassTag PCR was used to develop a multiplex assay for detection of 11 VRI pathogens. The assay was established and optimized using cloned template standards and spiked samples and was then evaluated on CSF specimens from ventricular drains. Subjects were grouped into definite VRI, possible VRI, or no VRI based on conventional microbiology, CSF evaluation, and clinical parameters.

RESULTS

CSF specimens were obtained from 45 subjects (median age 49 years, interquartile range 32-63 years; 51% were male). The assay detected 10-100 genome copies. It detected a pathogen in 100% (6 of 6) of definite VRI cases in which a pathogen targeted by the assay was present; these represented 67% of all definite VRIs (6 of 9). Among subjects with a possible VRI, the assay detected a pathogen in 29% (5 of 17). In subjects without overt infection the presence of a pathogen was detected in 32% of subjects (6 of 19), albeit with lower signal compared with the VRI group.

CONCLUSIONS

MassTag PCR enabled parallel testing of CSF specimens for 11 pathogens of VRI. The high sensitivity of PCR combined with possible device colonization, specimen contamination, and concurrent antibiotic treatments limit the clinical value of the assay, similar to other current diagnostic approaches. With further optimization, multiplex PCR may provide timely identification of multiple possible VRI pathogens and guide management, complementing classic culture approaches.

Can rapid integrated polymerase chain reaction-based diagnostics for gastrointestinal pathogens improve routine hospital infection control practice? A diagnostic study

BACKGROUND

Every year approximately 5000-9000 patients are admitted to a hospital with diarrhoea, which in up to 90% of cases has a non-infectious cause. As a result, single rooms are 'blocked' by patients with non-infectious diarrhoea, while patients with infectious diarrhoea are still in open bays because of a lack of free side rooms. A rapid test for differentiating infectious from non-infectious diarrhoea could be very beneficial for patients.

OBJECTIVE

To evaluate MassCode multiplex polymerase chain reaction (PCR) for the simultaneous diagnosis of multiple enteropathogens directly from stool, in terms of sensitivity/specificity to detect four common important enteropathogens: Clostridium difficile, Campylobacter spp., Salmonella spp. and norovirus.

DESIGN

A retrospective study of fixed numbers of samples positive for C. difficile (n = 200), Campylobacter spp. (n = 200), Salmonella spp. (n = 100) and norovirus (n = 200) plus samples negative for all these pathogens (n = 300). Samples were sourced from NHS microbiology laboratories in Oxford and Leeds where initial diagnostic testing was performed according to Public Health England methodology. Researchers carrying out MassCode assays were blind to this information. A questionnaire survey, examining current practice for infection control teams and microbiology laboratories managing infectious diarrhoea, was also carried out.

SETTING

MassCode assays were carried out at Oxford University Hospitals NHS Trust. Further multiplex assays, carried out using Luminex, were run on the same set of samples at Leeds Teaching Hospitals NHS Trust. The questionnaire was completed by various NHS trusts.

MAIN OUTCOME MEASURES

Sensitivity and specificity to detect C. difficile, Campylobacter spp., Salmonella spp., and norovirus.

RESULTS

Nucleic acids were extracted from 948 clinical samples using an optimised protocol (200 Campylobacter spp., 199 C. difficile, 60 S. enterica, 199 norovirus and 295 negative samples; some samples contained more than one pathogen). Using the MassCode assay, sensitivities for each organism compared with standard microbiological testing ranged from 43% to 94% and specificities from 95% to 98%, with particularly poor performance for S. enterica. Relatively large numbers of unexpected positives not confirmed with quantitative PCR were also observed, particularly for S. enterica, Giardia lamblia and Cryptosporidium spp. As the results indicated that S. enterica detection might provide generic challenges to other multiplex assays for gastrointestinal pathogens, the Luminex xTag(®) gastrointestinal assay was also run blinded on the same extracts (937/948 remaining) and on re-extracted samples (839/948 with sufficient material). For Campylobacter spp., C. difficile and norovirus, high sensitivities (> 92%) and specificities (> 96%) were observed. For S. enterica, on the original MassCode/Oxford extracts, Luminex sensitivity compared with standard microbiological testing was 84% [95% confidence interval (CI) 73% to 93%], but this dropped to 46% on a fresh extract, very similar to MassCode, with a corresponding increase in specificity from 92% to 99%. Overall agreement on the per-sample diagnosis compared with combined microbiology plus PCR for the main four/all pathogens was 85.6%/64.7%, 87.0%/82.9% and 89.8%/86.8% for the MassCode assay, Luminex assay/MassCode extract and Luminex assay/fresh extract, respectively. Luminex assay results from fresh extracts implied that 5% of samples did not represent infectious diarrhoea, even though enteropathogens were genuinely present. Managing infectious diarrhoea was a significant burden for infection control teams (taking 21% of their time) and better diagnostics were identified as having major potential benefits for patients.

CONCLUSIONS

Overall, the Luminex xTag gastrointestinal panel showed similar or superior sensitivity and specificity to the MassCode assay. However, on fresh extracts, this test had low sensitivity to detect a key enteric pathogen, S. enterica; making it an unrealistic option for most microbiology laboratories. Extraction efficiency appears to be a major obstacle for nucleic acid-based tests for this organism, and possibly the whole Enterobacteriaceae family. To improve workflows in service microbiology laboratories, to reduce workload for infection control practitioners, and to improve outcomes for NHS patients, further research on deoxyribonucleic acid-based multiplex gastrointestinal diagnostics is urgently needed.

FUNDING

The Health Technology Assessment programme of the National Institute for Health Research.

Virus hunting

Viral diagnosis and discovery are receiving increasing emphasis with the recognition of their importance in addressing the challenges of emerging infectious and chronic diseases, and the advent of antiviral drugs with which to reduce the morbidity and mortality of viral infections. Here we review the status of the field including the use of molecular, proteomic and immunological assays for viral detection, social media platforms for surveillance, and public health investments that may enable enhanced situational awareness and insights into the origins of zoonotic viral diseases.

Nucleic-acid testing, new platforms and nanotechnology for point-of-decision diagnosis of animal pathogens

Accurate disease diagnosis in animals is crucial for animal well-being but also for preventing zoonosis transmission to humans. In particular, livestock diseases may constitute severe threats to humans due to the particularly high physical contact and exposure and, also, be the cause of important economic losses, even in non-endemic countries, where they often arise in the form of rapid and devastating epidemics. Rapid diagnostic tests have been used for a long time in field situations, particularly during outbreaks. However, they mostly rely on serological approaches, which may confirm the exposure to a particular pathogen but may be inappropriate for point-of-decision (point-of-care) settings when emergency responses supported on early and accurate diagnosis are required. Moreover, they often exhibit modest sensitivity and hence significantly depend on later result confirmation in central or reference laboratories. The impressive advances observed in recent years in materials sciences and in nanotechnology, as well as in nucleic-acid synthesis and engineering, have led to an outburst of new in-the-bench and prototype tests for nucleic-acid testing towards point-of-care diagnosis of genetic and infectious diseases. Manufacturing, commercial, regulatory, and technical nature issues for field applicability more likely have hindered their wider entrance into veterinary medicine and practice than have fundamental science gaps. This chapter begins by outlining the current situation, requirements, difficulties, and perspectives of point-of-care tests for diagnosing diseases of veterinary interest. Nucleic-acid testing, particularly for the point of care, is addressed subsequently. A range of valuable signal transduction mechanisms commonly employed in proof-of-concept schemes and techniques born on the analytical chemistry laboratories are also described. As the essential core of this chapter, sections dedicated to the principles and applications of microfluidics, lab-on-a-chip, and nanotechnology for the development of point-of-care tests are presented. Microdevices already applied or under development for application in field diagnosis of animal diseases are reviewed.

Multiplex PCR analysis of clusters of unexplained viral respiratory tract infection in Cambodia

BACKGROUND

Fevers of unknown origin constitute a substantial disease burden in Southeast Asia. In majority of the cases, the cause of acute febrile illness is not identified.

METHODS

We used MassTag PCR, a multiplex assay platform, to test for the presence of 15 viral respiratory agents from 85 patients with unexplained respiratory illness representing six disease clusters that occurred in Cambodia between 2009 and 2012.

RESULTS

We detected a virus in 37 (44%) of the cases. Human rhinovirus, the virus detected most frequently, was found in both children and adults. The viruses most frequently detected in children and adults, respectively, were respiratory syncytial virus and enterovirus 68. Sequence analysis indicated that two distinct clades of enterovirus 68 were circulating during this time period.

CONCLUSIONS

This is the first report of enterovirus 68 in Cambodia and contributes to the appreciation of this virus as an important respiratory pathogen.

Rapid detection of shrimp white spot syndrome virus by real time, isothermal recombinase polymerase amplification assay

White spot syndrome virus (WSSV) causes large economic losses to the shrimp aquaculture industry, and thus far there are no efficient therapeutic treatments available against this lethal virus. In this study, we present the development of a novel real time isothermal recombinase polymerase amplification (RPA) assay for WSSV detection on a small ESEQuant Tube Scanner device. The RPA sensitivity, specificity and rapidity were evaluated by using a plasmid standard as well as viral and shrimp genomic DNAs. Compared with qPCR, the RPA assay revealed more satisfactory performance. It reached a detection limit up to 10 molecules in 95% of cases as determined by probit analysis of 8 independent experiments within 6.41 ± 0.17 min at 39 °C. Consequently, this rapid RPA method has great application potential for field use or point of care diagnostics.

Etiology of severe childhood pneumonia in the Gambia, West Africa, determined by conventional and molecular microbiological analyses of lung and pleural aspirate samples

Molecular analyses of lung aspirates from Gambian children with severe pneumonia detected pathogens more frequently than did culture and showed a predominance of bacteria, principally Streptococcuspneumoniae, >75% being of serotypes covered by current pneumococcal conjugate vaccines. Multiple pathogens were detected frequently, notably Haemophilus influenzae (mostly nontypeable) together with S. pneumoniae.

Use of staged molecular analysis to determine causes of unexplained central nervous system infections

No agent is implicated in most central nervous system (CNS) infections. To investigate cerebrospinal fluid samples from patients with CNS infections of unknown cause in 1 hospital in Taiwan, we used a staged molecular approach, incorporating techniques including multiplex MassTag PCR, 16S rRNA PCR, DNA microarray, and high-throughput pyrosequencing. We determined the infectious agent for 31 (24%) of 131 previously negative samples. Candidate pathogens were identified for 25 (27%) of 94 unexplained meningitis cases and 6 (16%) of 37 unexplained encephalitis cases. Epstein-Barr virus (18 infections) accounted for most of the identified agents in unexplained meningitis cases, followed by Escherichia coli (5), enterovirus (2), human herpesvirus 2 (1), and Mycobacterium tuberculosis. Herpesviruses were identified in samples from patients with unexplained encephalitis cases, including varicella-zoster virus (3 infections), human herpesvirus 1 (2), and cytomegalovirus (1). Our study confirms the power of multiplex MassTag PCR as a rapid diagnostic tool for identifying pathogens causing unexplained CNS infections.

Use of molecular assays for the diagnosis of influenza

Respiratory infections are the third highest cause of death worldwide and influenza has the highest mortality rate among lower respiratory tract infections (LRTIs). Diagnosis of LRTIs relies mostly on clinical symptoms and is not fully satisfactory. Influenza laboratory diagnosis improves the efficiency of prophylaxis or treatment of influenza by antiviral molecules and has a strong impact on the cost-effectiveness of curative treatment. Inappropriate treatment of patients may result in spreading of resistant strains. Molecular diagnostics play a central role in the surveillance and response of pandemic influenza due to highly pathogenic strains. Real-time assays can be used for diagnosis or surveillance purposes in humans and animals, and microarrays can be used to identify and monitor the spread of dangerous variants. Molecular assays are also useful to identify and distinguish influenza, other respiratory viruses and bacteria, although their cost-effectiveness must be proven on a large scale. As new antiviral options will be available to clinicians, a better treatment choice will benefit the patient and community. Recent progress in molecular techniques will be reviewed. Examples of real-time assays for the detection of influenza viruses, including the highly pathogenic influenza A strains H5N1 and H7N7, will be discussed. Promising new techniques that allow detailed genotyping of viruses or multiplex detection of several respiratory pathogens from a unique specimen will also be discussed. These techniques will, in the near future, significantly improve the quality of diagnosis and surveillance of respiratory pathogens.

The increasing application of multiplex nucleic acid detection tests to the diagnosis of syndromic infections

On 14 January 2013, the US Food and Drug Administration (FDA) announced permission for a multiplex nucleic acid test, the xTAG® Gastrointestinal Pathogen Panel (GPP) (Luminex Corporation, USA), which simultaneously detects 11 common viral, bacterial and parasitic causes of infectious gastroenteritis, to be marketed in the USA. This announcement reflects the current move towards the development and commercialization of detection technologies based on nucleic acid amplification techniques for diagnosis of syndromic infections. We discuss the limitations and advantages of nucleic acid amplification techniques and the recent advances in Conformité Européene - in-vitro diagnostic (CE-IVD)-approved multiplex real-time PCR kits for the simultaneous detection of multiple targets within the clinical diagnostics market.

Methods, quality control and specimen management in an international multicentre investigation of type 1 diabetes: TEDDY

BACKGROUND

The vast array and quantity of longitudinal samples collected in The Environmental Determinants of Diabetes in the Young study present a series of challenges in terms of quality control procedures and data validity. To address this, pilot studies have been conducted to standardize and enhance both biospecimen collection and sample obtainment in terms of autoantibody collection, stool sample preservation, RNA, biomarker stability, metabolic biomarkers and T-cell viability.

RESEARCH DESIGN AND METHODS

The Environmental Determinants of Diabetes in the Young is a multicentre, international prospective study (n = 8677) designed to identify environmental triggers of type 1 diabetes (T1D) in genetically at-risk children from ages 3 months until 15 years. The study is conducted through six primary clinical centres located in four countries.

RESULTS

As of May 2012, over three million biological samples and 250 million total data points have been collected, which will be analysed to assess autoimmunity status, presence of inflammatory biomarkers, genetic factors, exposure to infectious agents, dietary biomarkers and other potentially important environmental exposures in relation to autoimmunity and progression to T1D.

CONCLUSIONS

Detailed procedures were utilized to standardize both data harmonization and management when handling a large quantity of longitudinal samples obtained from multiple locations. In addition, a description of the available specimens is provided that serve as an invaluable repository for the elucidation of determinants in T1D focusing on autoantibody concordance and harmonization, transglutaminase autoantibody, inflammatory biomarkers (T-cells), genetic proficiency testing, RNA lab internal quality control testing, infectious agents (monitoring cross-contamination, virus preservation and nasal swab collection validity) and HbA1c testing.

Evolving gene targets and technology in influenza detection

Influenza viruses cause recurring epidemic outbreaks every year associated with high morbidity and mortality. Despite extensive research and surveillance efforts to control influenza outbreaks, the primary mitigation treatment for influenza is the development of yearly vaccine mixes targeted for the most prevalent virus strains. Consequently, the focus of many detection technologies has evolved toward accurate identification of subtype and understanding the evolution and molecular determinants of novel and pathogenic forms of influenza. The recent availability of potential antiviral treatments are only effective if rapid and accurate diagnostic tests for influenza epidemic management are available; thus, early detection of influenza infection is still important for prevention, containment, patient management, and infection control. This review discusses the current and emerging technologies for detection and strain identification of influenza virus and their specific gene targets, as well as their implications in patient management.

Proteomic analysis of extremely severe hand, foot and mouth disease infected by enterovirus 71

BACKGROUND

To clarify the molecular mechanisms that participate in the severe hand, foot and mouth disease (HFMD) infected by Enterovirus 71 and to detect any related protein biomarkers, we performed proteomic analysis of protein extracts from 5 extremely severe HFMD children and 5 healthy children.

METHODS

The protein profiles of them were compared using two-dimensional electrophoresis. Differentially expressed proteins were identified using mass spectrometry. Functional classifications of these proteins were based on the PANTHER. The interaction network of the differentially expressed protein was generated with Pathway Studio.

RESULTS

A total of 38 differentially expressed proteins were identified. Functional classifications of these proteins indicated a series of altered cellular processes as a consequence of the severe HFMD. These results provided not only new insights into the pathogenesis of severe HFMD, but also implications of potential therapeutic designs.

CONCLUSIONS

Our results suggested the possible pathways that could be the potential targets for novel therapy: viral protection, complement system and peroxide elimination.

A prospective study of agents associated with acute respiratory infection among young American Indian children

BACKGROUND

Native American children have higher rates of morbidity associated with acute respiratory infection than children in the general US population, yet detailed information is lacking regarding their principal clinical presentations and infectious etiologies.

METHODS

We pursued a comprehensive molecular survey of bacteria and viruses in nasal wash specimens from children with acute respiratory disease collected prospectively over 1 year (January 1 through December 31, 2009) from 915 Navajo and White Mountain Apache children in their second or third year of life who had been enrolled in an efficacy study of a respiratory syncytial virus monoclonal antibody in the first year of life.

RESULTS

During the surveillance period, 1476 episodes of disease were detected in 669 children. Rates of outpatient and inpatient lower respiratory tract illness were 391 and 79 per 1000 child-years, respectively, and were most commonly diagnosed as pneumonia. Potential pathogens were detected in 88% of specimens. Viruses most commonly detected were respiratory syncytial virus and human rhinovirus; the 2009 pandemic influenza A (H1N1) illnesses primarily occurred in the fall. Streptococcus pneumoniae was detected in 60% of subjects; only human rhinovirus was significantly associated with S. pneumoniae carriage. The presence of influenza virus, human rhinovirus or S. pneumoniae was not associated with increased risk for lower respiratory tract involvement or hospitalization.

CONCLUSIONS

Acute lower respiratory illnesses occur at disproportionately high rates among young American Indian children and are associated with a range of common pathogens. This study provides critical evidence to support reducing the disproportionate burden of acute respiratory disease among young Native Americans.

Genomic analysis of coxsackieviruses A1, A19, A22, enteroviruses 113 and 104: viruses representing two clades with distinct tropism within enterovirus C

Coxsackieviruses (CV) A1, CV-A19 and CV-A22 have historically comprised a distinct phylogenetic clade within Enterovirus (EV) C. Several novel serotypes that are genetically similar to these three viruses have been recently discovered and characterized. Here, we report the coding sequence analysis of two genotypes of a previously uncharacterized serotype EV-C113 from Bangladesh and demonstrate that it is most similar to CV-A22 and EV-C116 within the capsid region. We sequenced novel genotypes of CV-A1, CV-A19 and CV-A22 from Bangladesh and observed a high rate of recombination within this group. We also report genomic analysis of the rarely reported EV-C104 circulating in the Gambia in 2009. All available EV-C104 sequences displayed a high degree of similarity within the structural genes but formed two clusters within the non-structural genes. One cluster included the recently reported EV-C117, suggesting an ancestral recombination between these two serotypes. Phylogenetic analysis of all available complete genome sequences indicated the existence of two subgroups within this distinct Enterovirus C clade: one has been exclusively recovered from gastrointestinal samples, while the other cluster has been implicated in respiratory disease.

Multiplex and quantitative pathogen detection with high-resolution capillary electrophoresis-based single-strand conformation polymorphism

Among the molecular diagnostic methods for bacteria-induced diseases, capillary electrophoresis-based single-strand conformation polymorphism (CE-SSCP) combined with 16S rRNA gene-specific PCR has enormous potential because it can separate sequence variants using a simple procedure. However, conventional CE-SSCP systems have limited resolution and cannot separate most 16S rRNA gene-specific markers into separate peaks. A high-resolution CE-SSCP system that uses a poly(ethyleneoxide)-poly(propyleneoxide)-poly(ethyleneoxide) triblock copolymer matrix was recently developed and shown to effectively separate highly similar PCR products. In this report, a protocol for the detection of 12 pathogenic bacteria is provided. Pathogen markers were amplified by PCR using universal primers and separated by CE-SSCP; each marker peak was well separated at baseline and showed a characteristic mobility, allowing the easy identification of the pathogens.

Serotype analysis of Streptococcus pneumoniae in lung and nasopharyngeal aspirates from children in the Gambia by MassTag PCR

Streptococcus pneumoniae strains comprise >90 serotypes. Here we describe establishment of a MassTag PCR assay designed to serotype S. pneumoniae and demonstrate its utility in tests using 31 paired lung aspirate and nasopharyngeal aspirate samples from children with pneumonia in the Gambia. Serotypes 1, 5, and 14 in were implicated in 90% of lung infections. With 5 exceptions, serotypes found in lung aspirates were also found in nasopharyngeal aspirates.

Genomic analysis of two novel human enterovirus C genotypes found in respiratory samples from Peru

We report the discovery of two enteroviruses detected in nasopharyngeal samples obtained from subjects with respiratory disease in Peru. Phylogenetic analysis indicated that both viruses belong to a clade within the species Human enterovirus C, which includes the recently characterized human enteroviruses 109 and 104. Members of this clade have undergone significant genomic rearrangement, as indicated by deletions in the hypervariable region of the 5' UTR and the VP1 protein, as well as recombination within the non-structural genes. Our findings and review of published sequences suggests that several novel human enterovirus C serotypes are currently circulating worldwide.

Development of TaqMan probe-based insulated isothermal PCR (iiPCR) for sensitive and specific on-site pathogen detection

Insulated isothermal PCR (iiPCR), established on the basis of Ralyeigh-Bénard convection, is a rapid and low-cost platform for nucleic acid amplification. However, the method used for signal detection, namely gel electrophoresis, has limited the application of iiPCR. In this study, TaqMan probe-based iiPCR system was developed to obviate the need of post-amplification processing. This system includes an optical detection module, which was designed and integrated into the iiPCR device to detect fluorescent signals generated by the probe. TaqMan probe-iiPCR assays targeting white spot syndrome virus (WSSV) and infectious myonecrosis virus were developed for preliminary evaluation of this system. Significant elevation of fluorescent signals was detected consistently among positive iiPCR reactions in both assays, correlating with amplicon detection by gel electrophoresis analysis. After condition optimization, a threshold value of S/N (fluorescent intensity_after/fluorescent intensity_before) for positive reactions was defined for WSSV TaqMan probe-iiPCR on the basis of 20 blank reactions. WSSV TaqMan probe-iiPCR generated positive S/Ns from as low as 10¹ copies of standard DNA and lightly infected Litopenaeus vannamei. Compared with an OIE-certified nested PCR, WSSV TaqMan probe-iiPCR showed a sensitivity of 100% and a specificity of 96.67% in 120 WSSV-free or lightly infected shrimp samples. Generating positive signals specifically and sensitively, TaqMan probe-iiPCR system has a potential as a low-cost and rapid on-site diagnostics method.

Simultaneous detection and identification of enteric viruses by PCR-mass assay

Simultaneous detection of enteric viruses that cause similar symptoms (e.g. hand, foot and mouth disease) is essential to the prevention of outbreaks and control of infections. In this study, a novel PCR-Mass assay combining multiplex polymerase chain reaction (PCR) with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was developed and used for simultaneous detection of eight distinct human enteric viruses. Enteric viral isolates and standard viral RNAs were examined to determine the sensitivity and specificity of the PCR-Mass assay. Clinical performance was evaluated with a total of 101 clinical specimens from patients suspected of having hand, foot and mouth disease (HFMD). The results were compared to those of previous analyses using real-time RT-PCR. The identification of specific viruses and clinical specimens shows that the PCR-Mass assay performed as well as or better than standard methods with respect to indicating the presence of multiplex pathogens in a single specimen.

Comparison of real-time PCR and MassTag PCR for the multiplex detection of highly pathogenic agents

Multiplex PCR assays are a cost- as well as labour-effective way to analyse one sample for several pathogens simultaneously. Besides the mutual competition of the individual PCR reactions included in a multiplex PCR assay, their specific read-out displays a limiting factor for the total number of PCR reactions that can be multiplexed. In this study, two PCR systems with different read-out approaches are compared, using a pentaplex PCR assay for the detection of highly pathogenic agents. A pentaplex assay was used since five represents the current limit of real-time PCR multiplexing capacity due to the low resolution of fluorescence emission peaks of the current equipment. In contrast, MassTag PCR as a quite new technique offers the possibility to detect up to 20-30 target sequences from one reaction. After extensive and separate optimisation of the PCR protocol for both platforms, a comparative probit analysis showed good sensitivities for MassTag and real-time PCR detection. Nevertheless, the detection limits of MassTag PCR have been undercut by the real-time PCR for each target. We therefore conclude that MassTag PCR is a useful diagnostic technique for the sensitive screening for pathogens by highly multiplexed PCR assays, but cannot reach the sensitivity of real-time PCR for lower multiplexed PCR assays.

Bioethical considerations in developing a biorepository for the Pneumonia Etiology Research for Child Health project

The Pneumonia Etiology Research for Child Health (PERCH) project has the potential to provide a highly valuable resource of biospecimens that may be used to inform future studies on the causes of pneumonia. Designing a biorepository for this complex project was done in collaboration with a wide range of experts including bioethicists. In this paper, we describe the most significant ethical issues encountered related to the biorepository, focusing on its structure and informed consent. We also outline the proposed approach to the PERCH biorepository, which was designed to be sensitive to the ethical, practical, and cultural challenges inherent to the study. Through this process, we concluded that biorepository governance plans and strategies for managing informed consent should be implemented in a way to allow for careful study in order to better understand the attitudes of and impact on the stakeholders involved in the study.

Use and evaluation of molecular diagnostics for pneumonia etiology studies

Comprehensive microbiological testing will be a core function of the Pneumonia Etiology Research for Child Health (PERCH) project. The development stage of PERCH provided the time and resources necessary for us to conduct a comprehensive review of the current state of respiratory diagnostics. These efforts allowed us to articulate the unique requirements of PERCH, establish that molecular methods would be central to our testing strategy, and focus on a short list of candidate platforms. This process also highlighted critical challenges in the general design and interpretation of diagnostic evaluation studies, particularly in the field of respiratory infections. Although our final molecular diagnostic platform was ultimately selected on the basis of operational and strategic considerations determined by the specific context of PERCH, our review highlighted several conceptual and practical challenges in respiratory diagnostics that have broader relevance for the performance and interpretation of pneumonia research studies.