Genomic signature-based identification of influenza A viruses using RT-PCR/electro-spray ionization mass spectrometry (ESI-MS) technology

Mechanisms, Techniques and Devices of Airborne Virus Detection: A Review

Airborne viruses, such as COVID-19, cause pandemics all over the world. Virus-containing particles produced by infected individuals are suspended in the air for extended periods, actually resulting in viral aerosols and the spread of infectious diseases. Aerosol collection and detection devices are essential for limiting the spread of airborne virus diseases. This review provides an overview of the primary mechanisms and enhancement techniques for collecting and detecting airborne viruses. Indoor virus detection strategies for scenarios with varying ventilations are also summarized based on the excellent performance of existing advanced comprehensive devices. This review provides guidance for the development of future aerosol detection devices and aids in the control of airborne transmission diseases, such as COVID-19, influenza and other airborne transmission viruses.

Natural infection of parvovirus in wild fishing cats (Prionailurus viverrinus) reveals extant viral localization in kidneys

Carnivore protoparvovirus-1 (CPPV-1), a viral species containing feline panleukopenia virus (FPV) and canine parvovirus (CPV) variants, are widely spread among domestic and wild carnivores causing systemic fatal diseases. Wild fishing cats (Prionailurus viverrinus), a globally vulnerable species, have been found dead. Postmortem examination of the carcasses revealed lesions in intestine, spleen and kidney. CPPV-1 antigen identification in these tissues, using polymerase chain reaction (PCR) and immunohistochemistry (IHC), supported the infection by the virus. PCR- and IHC-positivity in kidney tissues revealed atypical localization of the virus while in situ hybridization (ISH) and transmission electron microscopy (TEM) with the pop-off technique confirmed the first description of viral localization in kidneys. Complete genome characterization and deduced amino acid analysis of the obtained CPPV-1 from the fishing cats revealed FPV as a causative agent. The detected FPV sequences showed amino acid mutations at I566M and M569R in the capsid protein. Phylogenetic and evolutionary analyses of complete coding genome sequences revealed that the fishing cat CPPV-1 genomes are genetically clustered to the FPV genomes isolated from domestic cats in Thailand. Since the 1970s, these genomes have also been shown to share a genetic evolution with Chinese FPV strains. This study is the first evidence of CPPV-1 infection in fishing cats and it is the first to show its localization in the kidneys. These findings support the multi-host range of this parvovirus and suggest fatal CPPV-1 infections may result in other vulnerable wild carnivores.

Advanced Immunotechnological Methods for Detection and Diagnosis of Viral Infections: Current Applications and Future Challenges

Diagnosis and identification of viruses is an important component of diagnostic virology laboratory. Although various modes of diagnostic methods are now available at disposal, a vast majority of the diseases across the globe remain undiagnosed. This is largely due to the overlapping undifferentiated set of symptoms across myriad set of RNA and DNA viral diseases. As such, it becomes critical to take into consideration several factors for viral diagnosis ranging from the type and quality of specimen collected, time of specimen collection, mode of transport, accuracy, specificity, sensitivity, and the type of diagnostic method used. This chapter broadly emphasizes various methods on diagnostic virology ranging from the classical methods of diagnosis to the most recently developed molecular methods of detection of virus.

Molecular Testing of Serial Blood Specimens from Patients with Early Lyme Disease during Treatment Reveals Changing Coinfection with Mixtures of Borrelia burgdorferi Genotypes

Borrelia burgdorferi is the etiological agent of Lyme disease. In the current study, we used direct-detection PCR and electrospray ionization mass spectrometry to monitor and genotype B. burgdorferi isolates from serially collected whole-blood specimens from patients clinically diagnosed with early Lyme disease before and during 21 days of antibiotic therapy. B. burgdorferi isolates were detected up to 3 weeks after the initiation of antibiotic treatment, with ratios of coinfecting B. burgdorferi genotypes changing over time.

Molecular characterization of influenza viruses from women and infants in Sarlahi, Nepal

We used RT-PCR-electrospray ionization-mass spectrometry to identify subtypes and strains of influenza viruses detected during a maternal influenza immunization study in Nepal from May 2011 to April 2014. Hemagglutinin (HA) gene amino acid (aa) sequences of inferred reference strains were compared to those of the vaccines to determine impact of aa relatedness on vaccine efficacy (VE) and disease severity. Three influenza subtypes and many strains were identified. A(H3N2) strains with less than 13 aa differences in HA compared to vaccine strains (matched) showed higher VE than strains with 13 or more differences (mismatched). Yamagata lineage B strains, which were mismatched to the Victoria strain in the vaccine, demonstrated lower VE compared to Victoria strains. Differences in VE were not statistically significant. All A(H1N1pdm) matched the vaccine strain, with 10 or fewer aa differences. Except for women infected with vaccine-matched strains of influenza A, clinical signs and symptoms did not differ between vaccinated and unvaccinated participants.

Design and testing of multiplex RT-PCR primers for the rapid detection of influenza A virus genomic segments: Application to equine influenza virus

The avian influenza A virus causes respiratory infections in animal species. It can undergo genomic recombination with newly obtained genetic material through an interspecies transmission. However, the process is an unpredictable event, making it difficult to predict the emergence of a new pandemic virus and distinguish its origin, especially when the virus is the result of multiple infections. Therefore, identifying a novel influenza is entirely dependent on sequencing its whole genome. Occasionally, however, it can be time-consuming, costly, and labor-intensive when sequencing many influenza viruses. To compensate for the difficulty, we developed a rapid, cost-effective, and simple multiplex RT-PCR to identify the viral genomic segments. As an example to evaluate its performance, H3N8 equine influenza virus (EIV) was studied for the purpose. In developing this protocol to amplify the EIV eight-segments, a series of processes, including phylogenetic analysis based on different influenza hosts, in silico analyses to estimate primer specificity, coverage, and variation scores, and investigation of host-specific amino acids, were progressively conducted to reduce or eliminate the negative factors that might affect PCR amplification. Selectively, EIV specific primers were synthesized with dual priming oligonucleotides (DPO) system to increase primer specificity. As a result, 16 primer pairs were selected to screen the dominantly circulating H3N8 EIV 8 genome segments: PA (3), PB2 (1), PA (3), NP (3), NA8 (2), HA3 (1), NS (1), and M (2). The diagnostic performance of the primers was evaluated with eight sets composing of four segment combinations using viral samples from various influenza hosts. The PCR results suggest that the multiplex RT-PCR has a wide range of applications in detection and diagnosis of newly emerging EIVs. Further, the proposed procedures of designing multiplex primers are expected to be used for detecting other animal influenza A viruses.

Sterile intra-amniotic inflammation in asymptomatic patients with a sonographic short cervix: prevalence and clinical significance

OBJECTIVE

To determine the frequency and clinical significance of sterile and microbial-associated intra-amniotic inflammation in asymptomatic patients with a sonographic short cervix.

METHODS

Amniotic fluid (AF) samples obtained by transabdominal amniocentesis from 231 asymptomatic women with a sonographic short cervix [cervical length (CL) ≤25 mm] were analyzed using cultivation techniques (for aerobic and anaerobic as well as genital mycoplasmas) and broad-range polymerase chain reaction (PCR) coupled with electrospray ionization mass spectrometry (PCR/ESI-MS). The frequency and magnitude of intra-amniotic inflammation [defined as an AF interleukin (IL)-6 concentration ≥2.6 ng/mL], acute histologic placental inflammation, spontaneous preterm delivery (sPTD), and the amniocentesis-to-delivery interval were examined according to the results of AF cultures, PCR/ESI-MS and AF IL-6 concentrations.

RESULTS

Ten percent (24/231) of patients with a sonographic short cervix had sterile intra-amniotic inflammation (an elevated AF IL-6 concentration without evidence of microorganisms using cultivation and molecular methods). Sterile intra-amniotic inflammation was significantly more frequent than microbial-associated intra-amniotic inflammation [10.4% (24/231) versus 2.2% (5/231); p < 0.001]. Patients with sterile intra-amniotic inflammation had a significantly higher rate of sPTD <34 weeks of gestation [70.8% (17/24) versus 31.6% (55/174); p < 0.001] and a significantly shorter amniocentesis-to-delivery interval than patients without intra-amniotic inflammation [median 35, (IQR: 10-70) versus median 71, (IQR: 47-98) days, (p < 0.0001)].

CONCLUSION

Sterile intra-amniotic inflammation is more common than microbial-associated intra-amniotic inflammation in asymptomatic women with a sonographic short cervix, and is associated with increased risk of sPTD (<34 weeks). Further investigation is required to determine the causes of sterile intra-amniotic inflammation and the mechanisms whereby this condition is associated with a short cervix and sPTD.

Respiratory Infections in the U.S. Military: Recent Experience and Control

This comprehensive review outlines the impact of military-relevant respiratory infections, with special attention to recruit training environments, influenza pandemics in 1918 to 1919 and 2009 to 2010, and peacetime operations and conflicts in the past 25 years. Outbreaks and epidemiologic investigations of viral and bacterial infections among high-risk groups are presented, including (i) experience by recruits at training centers, (ii) impact on advanced trainees in special settings, (iii) morbidity sustained by shipboard personnel at sea, and (iv) experience of deployed personnel. Utilizing a pathogen-by-pathogen approach, we examine (i) epidemiology, (ii) impact in terms of morbidity and operational readiness, (iii) clinical presentation and outbreak potential, (iv) diagnostic modalities, (v) treatment approaches, and (vi) vaccine and other control measures. We also outline military-specific initiatives in (i) surveillance, (ii) vaccine development and policy, (iii) novel influenza and coronavirus diagnostic test development and surveillance methods, (iv) influenza virus transmission and severity prediction modeling efforts, and (v) evaluation and implementation of nonvaccine, nonpharmacologic interventions.

Antiviral resistance in influenza viruses: laboratory testing

Influenza continues to be a significant health care issue. Although vaccination is the major line of defense, antiviral drugs play an important role in prophylaxis and disease management. Approved drugs for influenza are currently limited to those that target the viral matrix protein or neuraminidase enzyme. Resistance-associated sequence changes in the genes encoding these proteins have been extensively studied. Available methods for genotypic and phenotypic antiviral susceptibility testing have expanded and are being further developed and improved. The sporadic emergence of drug-resistant variants and the global spread of resistant strains have demonstrated the ongoing need for vigilant testing and surveillance.

Mass spectrometry-based comparative sequence analysis for the genetic monitoring of influenza A(H1N1)pdm09 virus

The pandemic influenza A (H1N1) 2009 virus (pH1N1) contains novel gene segments of zoonotic origin that lack virulence and antiviral resistance markers. We aimed to evaluate the applicability and accuracy of mass spectrometry-based comparative sequence analysis (MSCSA) to detect genetic mutations associated with increased virulence or antiviral resistance in pH1N1. During the 2009 H1N1 pandemic, routine surveillance specimens and clinical antiviral resistance monitoring specimens were analyzed. Routine surveillance specimens obtained from 70 patients with pH1N1 infection were evaluated for mutations associated with increased virulence (PB1-F2, PB2 and NS1 genes) or antiviral resistance (neuraminidase gene, NA) using MSCSA and Sanger sequencing. MSCSA and Sanger sequencing results revealed a high concordance (nucleotides >99%, SNPs ∼94%). Virulence or resistance markers were not detected in routine surveillance specimens: all identified SNPs encoded for silent mutations or non-relevant amino acid substitutions. In a second study population, the presence of H275Y oseltamivir resistant virus was identified by real-time PCR in 19 of 35 clinical antiviral resistance monitoring specimens obtained from 4 immunocompromised patients with ≥14 days prolonged pH1N1 excretion. MSCSA detected H275Y in 24% (4/19) of positive specimens and Sanger sequencing in 89% (17/19). MSCSA only detected H275Y when the mutation was dominant in the analyzed specimens. In conclusion, MSCSA may be used as a rapid screening tool during molecular surveillance of pH1N1. The low sensitivity for the detection of H275Y mutation in mixed viral populations suggests that MSCSA is not suitable for antiviral resistance monitoring in the clinical setting.

A case-control study evaluating RT-PCR/ESI-MS technology compared to direct fluorescent antibody and xTAG RVP PCR

Waste nasopharyngeal swabs (N = 244) were evaluated by the reverse-transcriptase polymerase chain reaction/electrospray ionization mass spectrometry PLEX-ID Broad Respiratory Virus Surveillance Kit version 2.5 compared to direct fluorescent antibody and xTAG Respiratory Virus Panel for percent agreement, sensitivity, and specificity. Sensitivity and specificity were 91% (111/122) and 95.1% (116/122), respectively. Sensitivity by virus, except parainfluenza, was 92.9-100%, and specificity was 99-100%.

A novel molecular microbiologic technique for the rapid diagnosis of microbial invasion of the amniotic cavity and intra-amniotic infection in preterm labor with intact membranes

PROBLEM

The diagnosis of microbial invasion of the amniotic cavity (MIAC) has been traditionally performed using traditional cultivation techniques, which require growth of microorganisms in the laboratory. Shortcomings of culture methods include the time required (days) for identification of microorganisms, and that many microbes involved in the genesis of human diseases are difficult to culture. A novel technique combines broad-range real-time polymerase chain reaction with electrospray ionization time-of-flight mass spectrometry (PCR/ESI-MS) to identify and quantify genomic material from bacteria and viruses.

METHOD OF STUDY

AF samples obtained by transabdominal amniocentesis from 142 women with preterm labor and intact membranes (PTL) were analyzed using cultivation techniques (aerobic, anaerobic, and genital mycoplasmas) as well as PCR/ESI-MS. The prevalence and relative magnitude of intra-amniotic inflammation [AF interleukin 6 (IL-6) concentration ≥ 2.6 ng/mL], acute histologic chorioamnionitis, spontaneous preterm delivery, and perinatal mortality were examined.

RESULTS

(i) The prevalence of MIAC in patients with PTL was 7% using standard cultivation techniques and 12% using PCR/ESI-MS; (ii) seven of ten patients with positive AF culture also had positive PCR/ESI-MS [≥17 genome equivalents per PCR reaction well (GE/well)]; (iii) patients with positive PCR/ESI-MS (≥17 GE/well) and negative AF cultures had significantly higher rates of intra-amniotic inflammation and acute histologic chorioamnionitis, a shorter interval to delivery [median (interquartile range-IQR)], and offspring at higher risk of perinatal mortality, than women with both tests negative [90% (9/10) versus 32% (39/122) OR: 5.6; 95% CI: 1.4-22; (P < 0.001); 70% (7/10) versus 35% (39/112); (P = 0.04); 1 (IQR: <1-2) days versus 25 (IQR: 5-51) days; (P = 0.002), respectively]; (iv) there were no significant differences in these outcomes between patients with positive PCR/ESI-MS (≥17 GE/well) who had negative AF cultures and those with positive AF cultures; and (v) PCR/ESI-MS detected genomic material from viruses in two patients (1.4%).

CONCLUSION

(i) Rapid diagnosis of intra-amniotic infection is possible using PCR/ESI-MS; (ii) the combined use of biomarkers of inflammation and PCR/ESI-MS allows for the identification of specific bacteria and viruses in women with preterm labor and intra-amniotic infection; and (iii) this approach may allow for administration of timely and specific interventions to reduce morbidity attributed to infection-induced preterm birth.

The experimental aerosol transmission of influenza virus

The threat of a virulent, highly transmissible pandemic virus has motivated an escalating research effort to identify the transmissible genotypes of animal viruses that cross over into the human population (animal–human transmission) and sustain human–human transmission. In addition to the pursuit of the viral genotype, a greater understanding of the host-virus phenotype of infectiousness, transmissibility and susceptibility will be required. This review examines experimental animal transmission of influenza for insights into human influenza transmission. Transmission is viewed as sequential steps that the virus must pass critical thresholds to achieve transmission and ultimately survival in the human host. In particular, a quantitative understanding in animal models of viral replication efficiency, airway viral load, exhaled viral aerosol load, environmental virus survival and host susceptibility will likely yield important insights. Computational modeling will enhance animal model data, as well as guide the use of pandemic mitigation strategies.

Mass spectrometric approaches to study enveloped viruses: new possibilities for structural biology and prophylactic medicine

This review considers principles of the use of mass spectrometry for the study of biological macromolecules. Some examples of protein identification, virion proteomics, testing vaccine preparations, and strain surveillance are represented. Possibilities of structural characterization of viral proteins and their posttranslational modifications are shown. The authors’ studies by MALDI-MS on S-acylation of glycoproteins from various families of enveloped viruses and on oligomerization of the influenza virus hemagglutinin transmembrane domains are summarized.

Reverse transcription-PCR-electrospray ionization mass spectrometry for rapid detection of biothreat and common respiratory pathogens

Electrospray ionization mass spectrometry (ESI-MS) analysis of reverse transcription (RT)-PCR amplicons from human respiratory samples allows for broad pathogen identification approximately 8 h after collection. We investigated the performance characteristics of a high-throughput RT-PCR-coupled ESI-MS assay for distinguishing biothreat (BT) agents from common bacterial, fungal, and viral respiratory pathogens in bronchoalveolar lavage (BAL) fluid specimens from subjects with suspected respiratory infections. In a retrospective case series, 202 BAL fluid specimens were collected at the Johns Hopkins Hospital between August 2010 and February 2011 from patients with suspected acute respiratory infections. Samples were processed using standard bacterial, viral, and fungal testing in the clinical microbiology laboratory as part of routine care and then were blindly spiked with either water or nucleic acids from BT organisms (Bacillus anthracis, Yersinia pestis, Francisella tularensis, Brucella spp., Burkholderia spp., and Rickettsia prowazekii) and tested by RT-PCR-ESI-MS. The sensitivities and specificities of RT-PCR-ESI-MS versus standard clinical methods were as follows: for mock BT DNA, 98.5% sensitivity (95% confidence interval [CI], 94.2 to 99.7%) and 100% specificity (95% CI, 93.1 to 100.0%); for bacterial pathogens, 81.8% sensitivity (95% CI, 74.3 to 87.6%) and 73.6% specificity (95% CI, 64.2 to 81.4%); for viral pathogens, 93.3% sensitivity (95% CI, 66.0 to 99.7%) and 97.3% specificity (95% CI, 89.7 to 99.5%); for fungal pathogens, 42.6% sensitivity (95% CI, 29.5 to 56.7%) and 97.8% specificity (95% CI, 91.8 to 99.6%). Our data suggest that RT-PCR-ESI-MS is a useful adjunct to standard culture protocols for rapid detection of both BT and common respiratory pathogens; further study is required for assay validation, especially for fungal detection, and potential implementation.

What is the role of newer molecular tests in the management of CAP?

Community-acquired pneumonia (CAP) accounts for major morbidity and mortality in the United States. With improved broad-spectrum antibiotics, the implementation of diagnostic studies has declined and most patients do not have an etiologic pathogen of CAP identified. To enhance the appropriate use of antiviral agents and prevent overuse of antibiotics, the successful management of CAP requires rapid and accurate diagnosis of the etiologic agent of CAP. This article provides an overview of the new rapid molecular tests for the diagnosis of influenza, other respiratory viruses, and bacteria compared with nonmolecular tests and how their use for directed therapy can enhance and improve the management of CAP.

Evaluation of the Pan Influenza detection kit utilizing the PLEX-ID and influenza samples from the 2011 respiratory season

A comparison study was performed between the PLEX-ID and the CDC RT-PCR method for the detection and identification of Influenza A viruses using nasopharyngeal samples (N=75) collected between January and May 2011. Overall agreement was 89.3% (67/75 kappa=0.57 95% CI 0.3-0.89). Positive percent agreement was 92.3% (60/65); negative percent agreement was 70% (7/10). H1N1 pdm09 identified: 42.6% (32/75) and 54.7% (41/75) by PLEX-ID and CDC RT-PCR, respectively. H3N2 identified: 29.3% (22/75) and 32% (24/75) of samples by PLEX-ID and CDC RT-PCR, respectively. Negatives identified: 16% (12/75) and 13.3% (10/75), by PLEX-ID and CDC RT-PCR respectively. For influenza viruses identified as H1N1 pdm09, Influenza A virus A/NEW YORK/15/2009(H1N1 pdm09) was the most prevalent genotype at 50% (16/32), followed by A/CALIFORNIA/05/2009(H1N1 pdm09) at 18.2% (6/32). Updated assay plates containing additional primers designed for H1N1 pdm09 HA and NA genes were utilized for this evaluation. Among H1N1 pdm09 samples, the HA gene was conserved in 96.9% (31/32) of samples. The NA gene was conserved in 96.9% (31/32).

Evaluation of a polymerase chain reaction-electrospray ionization time-of-flight mass spectrometry for the detection and subtyping of influenza viruses in respiratory specimens

Background

PCR coupled to electrospray ionization mass spectrometry technology (PCR/ESI-TOF-MS) (PLEX-ID system, Abbott Ibis Biosciences) was developed to characterize microbial pathogens.

Objectives

To evaluate the performance of the PLEX-ID flu detection™ kit for detecting Influenza viruses by comparison with the multiplex RespiFinder^® Kit (PathoFinder).

Study design

Acute-phase respiratory samples (n = 293) were analysed for this purpose. A subpopulation of influenza type A positive samples, identified with the RespiFinder^® kit (n = 64), were subtyped with the RealTime ready Inf A/H1N1 Detection Set^® (Roche Molecular Diagnostics) and results were compared to the PLEX-ID Flu Detection™ kit.

Results

274 samples gave concordant results (93.5%, p < 0.0001): 65 influenza A-positive, 18 influenza B-positive and 191 negative samples. Of these, 7 samples were PLEX-ID positive/RespiFinder^® negative (5 influenza A and 2 influenza B) and 12 were PLEX-ID positive/RespiFinder^® negative (10 influenza A and 2 influenza B). PLEX-ID showed one sample as an influenza A and B co-infection while the RespiFinder^® assay showed it to be influenza A-positive. The sensitivity, specificity, positive and negative predictive values of the PLEX-ID™ system were 87.4%, 96.5%, 92.2% and 94.1% respectively. Thirteen of 19 discordant samples available for retesting were investigated further with the Anyplex™II RV16 Detection kit (Seegene): seven were RespiFinder^® concordant, while six were PLEX-ID™ concordant. Subtyping of 61/64 influenza A samples was concordant (95.3%): 55 were H1N1pdm09 and six were non-H1N1pdm09. Three samples gave negative PLEX-ID™ results (one H1N1pdm09 and two non-H1N1pdm09).

Conclusions

PCR/ESI-TOF-MS technology showed good diagnostic performances to detect and subtype influenza viruses.

Clinical accuracy of a PLEX-ID flu device for simultaneous detection and identification of influenza viruses A and B

Respiratory tract infections caused by influenza A and B viruses often present nonspecifically, and a rapid, high-throughput laboratory technique that can identify influenza viruses is clinically and epidemiologically desirable. The PLEX-ID Flu assay (Abbott Molecular Inc., Des Plaines, IL) incorporates multilocus PCR and electrospray ionization-mass spectrometry to detect and differentiate influenza A 2009 H1N1 (H1N1-p), seasonal H1N1 (H1N1-s), influenza A H3N2, and influenza B viruses in nasopharyngeal swab (NPS) specimens. The clinical performance characteristics of the PLEX-ID Flu assay in symptomatic patients were determined in this multicenter trial. A total of 2,617 prospectively and retrospectively collected NPS specimens from patients with influenza-like illness between February 2008 and 28 May 2010 were eligible for inclusion in the study. Each specimen was tested in parallel by the PLEX-ID Flu assay and by the Prodesse ProFLU+ assay (Prodesse Inc., Madison, WI), to detect influenza A and B viruses. Specimens testing positive for influenza A virus by ProFLU+ were subtyped as H1N1-p, H1N1-s, or H3N2 by using the ProFAST+ assay (Gen-Probe Prodesse Inc.). The reproducibility of the PLEX-ID Flu assay ranged from 98.3 to 100.0%, as determined by testing a nine-specimen panel at three clinical sites on each of 5 days. Positive percent agreements (PPAs) and negative percent agreements (NPAs) of the PLEX-ID Flu assay were 94.5% and 99.0% for influenza A virus and 96.0% and 99.9% for influenza B virus, respectively. For the influenza A virus subtyping characterization, the PLEX-ID Flu assay had PPAs and NPAs of 98.3% and 97.5% for H1N1-p, 88.6% and 100.0% for H1N1-s, and 98.0% and 99.9% for H3N2, respectively. The overall agreements between the PLEX-ID and Prodesse ProFLU+/ProFAST+ assays were 97.1 to 100.0%. Bidirectional Sanger sequencing analysis revealed that 87.5% of 96 discrepant results between the PLEX-ID Flu and ProFLU+/ProFAST+ assays were found upon influenza A virus detection and H1N1-p subtyping. The PLEX-ID Flu assay demonstrated a high level of accuracy for the simultaneous detection and identification of influenza A and B viruses in patient specimens, providing a new laboratory tool for the rapid diagnosis and management of influenza A and B virus infections.

Detection and Identification of Salmonella enterica, Escherichia coli, and Shigella spp. via PCR-electrospray ionization mass spectrometry: isolate testing and analysis of food samples

An assay to identify the common food-borne pathogens Salmonella, Escherichia coli, Shigella, and Listeria monocytogenes was developed in collaboration with Ibis Biosciences (a division of Abbott Molecular) for the Plex-ID biosensor system, a platform that uses electrospray ionization mass spectroscopy (ESI-MS) to detect the base composition of short PCR amplicons. The new food-borne pathogen (FBP) plate has been experimentally designed using four gene segments for a total of eight amplicon targets. Initial work built a DNA base count database that contains more than 140 Salmonella enterica, 139 E. coli, 11 Shigella, and 36 Listeria patterns and 18 other Enterobacteriaceae organisms. This assay was tested to determine the scope of the assay's ability to detect and differentiate the enteric pathogens and to improve the reference database associated with the assay. More than 800 bacterial isolates of S. enterica, E. coli, and Shigella species were analyzed. Overall, 100% of S. enterica, 99% of E. coli, and 73% of Shigella spp. were detected using this assay. The assay was also able to identify 30% of the S. enterica serovars to the serovar level. To further characterize the assay, spiked food matrices and food samples collected during regulatory field work were also studied. While analysis of preenrichment media was inconsistent, identification of S. enterica from selective enrichment media resulted in serovar-level identifications for 8 of 10 regulatory samples. The results of this study suggest that this high-throughput method may be useful in clinical and regulatory laboratories testing for these pathogens.

Comprehensive biothreat cluster identification by PCR/electrospray-ionization mass spectrometry

Technology for comprehensive identification of biothreats in environmental and clinical specimens is needed to protect citizens in the case of a biological attack. This is a challenge because there are dozens of bacterial and viral species that might be used in a biological attack and many have closely related near-neighbor organisms that are harmless. The biothreat agent, along with its near neighbors, can be thought of as a biothreat cluster or a biocluster for short. The ability to comprehensively detect the important biothreat clusters with resolution sufficient to distinguish the near neighbors with an extremely low false positive rate is required. A technological solution to this problem can be achieved by coupling biothreat group-specific PCR with electrospray ionization mass spectrometry (PCR/ESI-MS). The biothreat assay described here detects ten bacterial and four viral biothreat clusters on the NIAID priority pathogen and HHS/USDA select agent lists. Detection of each of the biothreat clusters was validated by analysis of a broad collection of biothreat organisms and near neighbors prepared by spiking biothreat nucleic acids into nucleic acids extracted from filtered environmental air. Analytical experiments were carried out to determine breadth of coverage, limits of detection, linearity, sensitivity, and specificity. Further, the assay breadth was demonstrated by testing a diverse collection of organisms from each biothreat cluster. The biothreat assay as configured was able to detect all the target organism clusters and did not misidentify any of the near-neighbor organisms as threats. Coupling biothreat cluster-specific PCR to electrospray ionization mass spectrometry simultaneously provides the breadth of coverage, discrimination of near neighbors, and an extremely low false positive rate due to the requirement that an amplicon with a precise base composition of a biothreat agent be detected by mass spectrometry.

Monitoring seasonal influenza A evolution: rapid 2009 pandemic H1N1 surveillance with an reverse transcription-polymerase chain reaction/electro-spray ionization mass spectrometry assay

BACKGROUND

The emergence of the pandemic H1N1 influenza strain in 2009 reinforced the need for improved influenza surveillance efforts. A previously described influenza typing assay that utilizes RT-PCR coupled to electro-spray ionization mass spectrometry (ESI-MS) played an early role in the discovery of the pandemic H1N1 influenza strain, and has potential application for monitoring viral genetic diversity in ongoing influenza surveillance efforts.

OBJECTIVES

To determine the analytical sensitivity of RT-PCR/ESI-MS influenza typing assay for identifying the pandemic H1N1 strain and describe its ability to assess viral genetic diversity.

STUDY DESIGN

Two sets of pandemic H1N1 samples, 190 collected between April and June of 2009, and 69 collected between October 2009 and January 2010, were processed by the RT-PCR/ESI-MS influenza typing assay, and the spectral results were compared to reference laboratory results and historical sequencing data from the Nucleotide Database of the National Center for Biotechnology Information (NCBI).

RESULTS

Strain typing concordance with reference standard testing was 100% in both sample sets, and the assay demonstrated a significant increase in influenza genetic diversity, from 10.5% non-wildtype genotypes in early samples to 69.9% in late samples (P<0.001). An NCBI search demonstrated a similar increase, from 13.4% to 45.2% (P<0.001).

CONCLUSIONS

This comparison of early versus late influenza samples analyzed by RT-PCR/ESI-MS demonstrates the influenza typing assay's ability as a universal influenza detection platform to provide high-fidelity pH1N1 strain identification over time, despite increasing genetic diversity in the circulating virus. The genotyping data can also be leveraged for high-throughput influenza surveillance.

PCR-electrospray ionization mass spectrometry: the potential to change infectious disease diagnostics in clinical and public health laboratories

During the past 20 years, microbial detection methods that are genetically based, such as real-time PCR and peptide nucleic acid fluorescent hybridization, coexisted with traditional microbiological methods and were typically based on the identification of individual genetic targets. For these methods to be successful, a potential cause of infection must be suspected. More recently, multiplex PCR and multiplex RT-PCR were used to enable more broad-range testing based on panels of suspected pathogens. PCR–electrospray ionization mass spectrometry (PCR-ESI/MS) has emerged as a technology that is capable of identifying nearly all known human pathogens either from microbial isolates or directly from clinical specimens. Assay primers are strategically designed to target one or more of the broad pathogen categories: bacterial, mycobacterial, fungal, or viral. With broad-range amplification followed by detection of mixed amplicons, the method can identify genetic evidence of known and unknown pathogens. This unique approach supports a higher form of inquiry, asking the following question: What is the genetic evidence of known or unknown pathogens in the patient sample? This approach has advantages over traditional assays that commonly target the presence or absence of one or more pathogens with known genetic composition. This review considers the breadth of the published literature and explores the possibilities, advantages, and limitations for implementation of PCR-ESI/MS in diagnostic laboratories.

Pilot Evaluation of RT-PCR/Electrospray Ionization Mass Spectrometry (PLEX-ID/Flu assay) on Influenza-Positive Specimens

The PLEX-ID/Flu assay has been recently developed to enable the detection and typing of influenza viruses based on the RT-PCR/electrospray ionization mass spectrometry technology.This novel assay was evaluated for typing performance on 201 positive influenza A or B nasopharyngeal swab specimens (NPS) detected by real-time RT-PCR during the 2010-2011 season. The PLEX-ID/Flu assay detected and characterized 91.3% and 95.3% of all influenza A and B samples, respectively. All non-typeable influenza A and B specimens by the assay showed low viral loads with threshold cycle values ≥ 33. Taken together, and although our results need to be confirmed by further prospective studies, the PLEX-ID/Flu assay detected positively and gave a typing result for 93% of all NPS detected positively by real-time RT-PCR, thus suggesting a potential role for influenza virus surveillance among other techniques.

Molecular diagnosis of respiratory virus infections

The appearance of eight new respiratory viruses, including the SARS coronavirus in 2003 and swine-origin influenza A/H1N1 in 2009, in the human population in the past nine years has tested the ability of virology laboratories to develop diagnostic tests to identify these viruses. Nucleic acid based amplification tests (NATs) for respiratory viruses were first introduced two decades ago and today are utilized for the detection of both conventional and emerging viruses. These tests are more sensitive than other diagnostic approaches, including virus isolation in cell culture, shell vial culture (SVC), antigen detection by direct fluorescent antibody (DFA) staining, and rapid enzyme immunoassay (EIA), and now form the backbone of clinical virology laboratory testing around the world. NATs not only provide fast, accurate and sensitive detection of respiratory viruses in clinical specimens but also have increased our understanding of the epidemiology of both new emerging viruses such as the pandemic H1N1 influenza virus of 2009, and conventional viruses such as the common cold viruses, including rhinovirus and coronavirus. Multiplex polymerase chain reaction (PCR) assays introduced in the last five years detect up to 19 different viruses in a single test. Several multiplex PCR tests are now commercially available and tests are working their way into clinical laboratories. The final chapter in the evolution of respiratory virus diagnostics has been the addition of allelic discrimination and detection of single nucleotide polymorphisms associated with antiviral resistance. These assays are now being multiplexed with primary detection and subtyping assays, especially in the case of influenza virus. These resistance assays, together with viral load assays, will enable clinical laboratories to provide physicians with new and important information for optimal treatment of respiratory virus infections.

Exhaled aerosol transmission of pandemic and seasonal H1N1 influenza viruses in the ferret

Person-to-person transmission of influenza viruses occurs by contact (direct and fomites) and non-contact (droplet and small particle aerosol) routes, but the quantitative dynamics and relative contributions of these routes are incompletely understood. The transmissibility of influenza strains estimated from secondary attack rates in closed human populations is confounded by large variations in population susceptibilities. An experimental method to phenotype strains for transmissibility in an animal model could provide relative efficiencies of transmission. We developed an experimental method to detect exhaled viral aerosol transmission between unanesthetized infected and susceptible ferrets, measured aerosol particle size and number, and quantified the viral genomic RNA in the exhaled aerosol. During brief 3-hour exposures to exhaled viral aerosols in airflow-controlled chambers, three strains of pandemic 2009 H1N1 strains were frequently transmitted to susceptible ferrets. In contrast one seasonal H1N1 strain was not transmitted in spite of higher levels of viral RNA in the exhaled aerosol. Among three pandemic strains, the two strains causing weight loss and illness in the intranasally infected 'donor' ferrets were transmitted less efficiently from the donor than the strain causing no detectable illness, suggesting that the mucosal inflammatory response may attenuate viable exhaled virus. Although exhaled viral RNA remained constant, transmission efficiency diminished from day 1 to day 5 after donor infection. Thus, aerosol transmission between ferrets may be dependent on at least four characteristics of virus-host relationships including the level of exhaled virus, infectious particle size, mucosal inflammation, and viral replication efficiency in susceptible mucosa.

Molecular methods for pathogen and microbial community detection and characterization: current and potential application in diagnostic microbiology

Clinical microbiology laboratories worldwide have historically relied on phenotypic methods (i.e., culture and biochemical tests) for detection, identification and characterization of virulence traits (e.g., antibiotic resistance genes, toxins) of human pathogens. However, limitations to implementation of molecular methods for human infectious diseases testing are being rapidly overcome allowing for the clinical evaluation and implementation of diverse technologies with expanding diagnostic capabilities. The advantages and limitation of molecular techniques including real-time polymerase chain reaction, partial or whole genome sequencing, molecular typing, microarrays, broad-range PCR and multiplexing will be discussed. Finally, terminal restriction fragment length polymorphism (T-RFLP) and deep sequencing are introduced as technologies at the clinical interface with the potential to dramatically enhance our ability to diagnose infectious diseases and better define the epidemiology and microbial ecology of a wide range of complex infections.

Improving influenza virus detection

INTRODUCTION

Influenza virus infections cause significant morbidity, and the unique ability of these viruses to undergo antigenic drift and shift means that it is critical for current laboratory assays to keep pace with these changes for accurate diagnosis. New subtypes have the potential to evolve into pandemics hence accurate virus subtyping is also essential.

AREAS COVERED

In this article, the authors review the current techniques available to detect influenza virus.

EXPERT OPINION

The biggest gains in improving on influenza diagnostics may lie in reappraising our current approach and optimizing all existing steps in influenza detection: pre-analytical, analytical, post-analytical. In addition, we must foster close collaboration between governments, surveillance networks and frontline diagnostic laboratories, and utilize advances in information technology to facilitate these interactions and to disseminate crucial information.

Rethinking approaches to improve the utilization of nucleic acid amplification tests for detection and characterization of influenza A in diagnostic and reference laboratories

Influenza A virus (IFVA) is a significant cause of respiratory infections worldwide and was also responsible for a recent pandemic in 2009. Laboratory identification of IFVA can guide antiviral therapy, assist in cohorting of patients and prevent antibiotic use. Characterization of the virus can track the emergence of novel strains, identify resistance and determine how circulating strains match with vaccine components. The gold standard for detection and characterization of IFVA is nucleic acid amplification technology (e.g., reverse transcriptase PCR [RT-PCR]), which must contend with a constantly evolving viral genome. Although molecular technology has been available for over two decades, there is still an operational gap between assay design and utilization of these tests for the diagnosis and characterization of IFVA. This review will discuss issues surrounding the implementation and use of RT-PCR for the identification and characterization of IFVA, and speculate on why RT-PCR has not been used more widely in clinical laboratories or moved closer to the patient. Newer, less widely used technologies that may change our laboratory practices will be identified and the authors will close with an attempt to identify some future applications of RT-PCR-based technologies for the detection and characterization of IFVA.

Transmission of aerosolized seasonal H1N1 influenza A to ferrets

Influenza virus is a major cause of morbidity and mortality worldwide, yet little quantitative understanding of transmission is available to guide evidence-based public health practice. Recent studies of influenza non-contact transmission between ferrets and guinea pigs have provided insights into the relative transmission efficiencies of pandemic and seasonal strains, but the infecting dose and subsequent contagion has not been quantified for most strains. In order to measure the aerosol infectious dose for 50% (aID₅₀) of seronegative ferrets, seasonal influenza virus was nebulized into an exposure chamber with controlled airflow limiting inhalation to airborne particles less than 5 µm diameter. Airborne virus was collected by liquid impinger and Teflon filters during nebulization of varying doses of aerosolized virus. Since culturable virus was accurately captured on filters only up to 20 minutes, airborne viral RNA collected during 1-hour exposures was quantified by two assays, a high-throughput RT-PCR/mass spectrometry assay detecting 6 genome segments (Ibis T5000™ Biosensor system) and a standard real time RT-qPCR assay. Using the more sensitive T5000 assay, the aID₅₀ for A/New Caledonia/20/99 (H1N1) was approximately 4 infectious virus particles under the exposure conditions used. Although seroconversion and sustained levels of viral RNA in upper airway secretions suggested established mucosal infection, viral cultures were almost always negative. Thus after inhalation, this seasonal H1N1 virus may replicate less efficiently than H3N2 virus after mucosal deposition and exhibit less contagion after aerosol exposure.

Are we ready for novel detection methods to treat respiratory pathogens in hospital-acquired pneumonia?

Hospital-acquired pneumonia represents one of the most difficult treatment challenges in infectious diseases. Many studies suggest that the timely administration of appropriate, pathogen-directed therapy can be lifesaving. Because results of culture and antimicrobial susceptibility testing can take 48 h or longer, physicians currently rely on clinical, epidemiological, and demographic factors to assist with the choice of empiric therapy for antibiotic-resistant pathogens. At present, a number of rapid molecular tests are being developed that identify pathogens and the presence of genetic determinants of antimicrobial resistance (eg, GeneXpert [Cepheid], ResPlex [Qiagen], FilmArray [Idaho Technologies], and Microarray [Check-Points]). In this review, the potential impact that molecular diagnostics has to identify and characterize pathogens that cause hospital-acquired bacterial pneumonia at an early stage is examined. In addition, a perspective on a novel technology, polymerase chain reaction followed by electrospray ionization mass spectrometry, is presented, and its prospective use in the diagnosis of pneumonia is also discussed. The complexities of the pulmonary microbiome represent a novel challenge to clinicians, but many questions still remain even as these technologies improve.