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Many organisms, such as insects, filarial nematodes, and ticks, contain heritable bacterial endosymbionts that are often closely related to transmissible tickborne pathogens. These intracellular bacteria are sometimes unique to the host species, presumably due to isolation and genetic drift. We used a polymerase chain reaction/electrospray ionization-mass spectrometry assay designed to detect a wide range of vectorborne microorganisms to characterize endosymbiont genetic signatures from Amblyomma americanum (L.), Amblyomma maculatum Koch, Dermacentor andersoni Stiles, Dermacentor occidentalis Marx, Dermacentor variabilis (Say), Ixodes scapularis Say, Ixodes pacificus Cooley & Kohls, Ixodes ricinus (L.), and Rhipicephalus sanguineus (Latreille) ticks collected at various sites and of different stages and both sexes. The assay combines the abilities to simultaneously detect pathogens and closely related endosymbionts and to identify tick species via characterization of their respective unique endosymbionts in a single test.

Objective—To develop and evaluate a rapid and accurate assay involving PCR amplification and electrospray ionization mass spectrometry of nucleic acid extracts from whole blood samples for the detection of Dirofilaria immitis infection in dogs. Sample—Whole blood nucleic acid extracts from 29 dogs experimentally infected with D immitis (and in which circulating D immitis antigen was detected) and 10 uninfected dogs. Procedures—16 of the 29 whole blood samples from infected dogs were examined at the time of collection for circulating microfilaria. Nucleic acids were extracted from all whole blood specimens and underwent PCR amplification with 12 PCR primer pairs designed to detect a wide range of pathogens (including the Wolbachia endosymbiont of D immitis) and electrospray ionization mass spectrometry. Results—On the basis of assay results, heartworm infection was detected in 13 of 13 antigen-positive dogs of unknown microfilaria status, 11 of 11 antigen-positive dogs with circulating microfilaria, 0 of 3 antigen-positive dogs tested at 3 months after larval infection, 0 of 2 antigen-positive dogs with occult infections, and 0 of 10 uninfected dogs. Conclusions and Clinical Relevance—With the assay under investigation, it was possible to identify D immitis infection in dogs with circulating microfilaria via detection of the obligate Wolbachia endosymbiont of D immitis. It was not possible to identify dogs with occult infections, which suggested that circulating microfilaria must be present to detect infection with this assay, although further studies would be required to verify that finding.

Technologies for the correct and timely diagnosis of bloodstream infections are urgently needed. Molecular diagnostic methods have yet to have a major impact on the diagnosis of bloodstream infections; however, new methods are being developed that are beginning to address key issues. In this article, we discuss the key needs and objectives of molecular diagnostics for bloodstream infections and review some of the currently available methods and how these techniques meet key needs. We then focus on a new method that combines nucleic acid amplification with mass spectrometry in a novel approach to molecular diagnosis of bloodstream infections.

There are few diagnostic methods that readily distinguish among community-acquired methicillin (meticillin)-resistant Staphylococcus aureus strains, now frequently transmitted within hospitals. We describe a rapid and high-throughput method for bacterial profiling of staphylococcal isolates. The method couples PCR to electrospray ionization-mass spectrometry (ESI-MS) and is performed on a platform suitable for use in a diagnostic laboratory. This profiling technology produces a high-resolution genetic signature indicative of the presence of specific genetic elements that represent distinctive phenotypic features. The PCR/ESI-MS signature accurately identified genotypic determinants consistent with phenotypic traits in well-characterized reference and clinical isolates of S. aureus . Molecular identification of the antibiotic resistance genes correlated strongly with phenotypic in vitro resistance. The identification of toxin genes correlated with independent PCR analyses for the toxin genes. Finally, isolates were correctly classified into genotypic groups that correlated with genetic clonal complexes, repetitive-element-based PCR patterns, or pulsed-field gel electrophoresis types. The high-throughput PCR/ESI-MS assay should improve clinical management of staphylococcal infections.

Invasive fungal infections are a significant cause of morbidity and mortality among immunocompromised patients. Early and accurate identification of these pathogens is central to direct therapy and to improve overall outcome. PCR coupled with electrospray ionization mass spectrometry (PCR/ESI-MS) was evaluated as a novel means for identification of fungal pathogens. Using a database grounded by 60 ATCC reference strains, a total of 394 clinical fungal isolates (264 molds and 130 yeasts) were analyzed by PCR/ESI-MS; results were compared to phenotypic identification, and discrepant results were sequence confirmed. PCR/ESI-MS identified 81.4% of molds to either the genus or species level, with concordance rates of 89.7% and 87.4%, respectively, to phenotypic identification. Likewise, PCR/ESI-MS was able to identify 98.4% of yeasts to either the genus or species level, agreeing with 100% of phenotypic results at both the genus and species level. PCR/ESI-MS performed best with Aspergillus and Candida isolates, generating species-level identification in 94.4% and 99.2% of isolates, respectively. PCR/ESI-MS is a promising new technology for broad-range detection and identification of medically important fungal pathogens that cause invasive mycoses.

Detection of pathogens in bloodstream infections is important for directing antimicrobial treatment, but current culture-based approaches can be problematic. Broad-range PCR assays which target conserved genomic motifs for postamplification amplicon analysis permit detection of sepsis-causing pathogens. Comparison of different broad-range assays is important for informing future implementation strategies. In this study, we compared positive-blood-culture bottles processed by PCR coupled to high-resolution melting curve analysis (PCR/HRMA) and PCR coupled to electrospray ionization-mass spectrometry (PCR/ESI-MS) to microbiology culture results. Genus-level concordance was 90% (confidence interval [CI], 80 to 96%) for PCR/HRMA and 94% (CI, 85 to 98%) for PCR/ESI-MS. Species-level concordance was 90% (CI, 80 to 96%) for PCR/HRMA and 86% (CI, 75 to 93%) for PCR/ESI-MS. Unlike PCR/HRMA, PCR/ESI-MS was able to resolve polymicrobial samples. Our results demonstrated that the two assays have similar overall concordance rates but may have different roles as potential adjunctive tests with standard blood culture, since each method has different capabilities, advantages, and disadvantages.

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.

The Ibis T5000 is a novel diagnostic platform that couples PCR and mass spectrometry. In this study, we developed an assay that can identify all known pathogenic Vibrio species and field-tested it using natural water samples from both freshwater lakes and the Georgian coastal zone of the Black Sea. Of the 278 total water samples screened, 9 different Vibrio species were detected, 114 (41%) samples were positive for V. cholerae , and 5 (0.8%) samples were positive for the cholera toxin A gene ( ctxA ). All ctxA -positive samples were from two freshwater lakes, and no ctxA -positive samples from any of the Black Sea sites were detected.

Monkeypox virus (MPXV), a member of the family Poxviridae and genus Orthopoxvirus, causes a smallpox-like disease in humans. A previously described pan-Orthopoxvirus assay, based on a broad-range polymerase chain reaction (PCR) coupled with electrospray ionization mass spectrometry (PCR/ESI-MS), was evaluated for its ability to detect MPXV from spiked human and aerosol-infected cynomolgous macaque (Macaca fascicularis) samples. Detection of MPXV DNA from macaque tissue, blood, and spiked human blood by the PCR/ESI-MS pan-Orthopoxvirus assay was comparable, albeit at slightly higher levels, to the current gold standard method of real-time PCR with the pan-Orthopoxvirus assay and had a limit of detection of 200 plaque-forming units. Furthermore, the platform was able to distinguish MPXV and vaccinia viruses that were spiked into macaque blood samples at various concentrations. This platform provides a new tool for the diagnosis and monitoring of orthopoxviral loads during vaccine or antiviral studies, but also could provide rapid identification during natural outbreaks or bioterrorism attacks.

Rapid detection and identification of Ehrlichia species improves clinical outcome for patients suspected of ehrlichiosis. We describe an assay that employs multilocus PCR and electrospray ionization mass spectrometry (PCR/ESI-MS) to detect and identify Ehrlichia species directly from blood specimens. The results were compared to those of a colorimetric microtiter PCR enzyme immunoassay (PCR-EIA) used as a diagnostic assay. Among 213 whole-blood samples collected from patients who were clinically suspected of ehrlichiosis from 1 May to 1 August 2008 at Vanderbilt University Hospital, 40 were positive for an Ehrlichia species by PCR/ESI-MS, giving a positive rate of 18.8%. In comparison to the PCR-EIA, PCR/ESI-MS possessed a sensitivity, a specificity, and positive and negative predictive values of 95.0%, 98.8%, 95.0%, and 98.8%, respectively. The 38 specimens that were positive for Ehrlichia by both PCR/ESI-MS and the PCR-EIA were further characterized to the species level, with 100% agreement between the two assays. In addition, Rickettsia rickettsii was detected by PCR/ESI-MS from four specimens that were confirmed retrospectively by serology and PCR-EIA. In three specimens, the PCR/ESI-MS assay identified Pseudomonas aeruginosa , Neisseria meningitidis , and Staphylococcus aureus ; these were confirmed by culture and/or clinical diagnosis as being clinically relevant. From specimen processing to result reporting, the PCR/ESI-MS assay can be completed within 6 h, providing another laboratory tool for the diagnosis of ehrlichiosis. Moreover, this system may provide rapid detection and identification of additional pathogens directly from blood specimens.

We describe a high-throughput assay using PCR coupled to electrospray ionization-mass spectrometry (PCR/ESI-MS) to determine the genotypes of Staphylococcus aureus isolates. The primer sets used in the PCR/ESI-MS assay were designed to amplify the same genes analyzed in multilocus sequence typing (MLST). The method was used to identify the clonal complex and USA type of each isolate and is suitable for use in a clinical or public-health setting. The method was validated using a panel of diverse isolates from the Centers for Disease Control and Prevention that were previously characterized by MLST and pulsed-field gel electrophoresis (PFGE). Clinical isolates from two geographically distinct hospitals were characterized, and the clustering results were in agreement with those for repetitive-element PCR and PFGE. The PCR/ESI-MS method enables genotyping of over 180 samples of S. aureus per day in an automated fashion.

Direct molecular tests in blood for early Lyme disease can be insensitive due to low amount of circulating Borrelia burgdorferi DNA. To address this challenge, we have developed a sensitive strategy to both detect and genotype B. burgdorferi directly from whole blood collected during the initial patient visit. This strategy improved sensitivity by employing 1.25 mL of whole blood, a novel pre-enrichment of the entire specimen extract for Borrelia DNA prior to a multi-locus PCR and electrospray ionization mass spectrometry detection assay. We evaluated the assay on blood collected at the initial presentation from 21 endemic area patients who had both physician-diagnosed erythema migrans (EM) and positive two-tiered serology either at the initial visit or at a follow-up visit after three weeks of antibiotic therapy. Results of this DNA analysis showed detection of B. burgdorferi in 13 of 21 patients (62%). In most cases the new assay also provided the B. burgdorferi genotype. The combined results of our direct detection assay with initial physician visit serology resulted in the detection of early Lyme disease in 19 of 21 (90%) of patients at the initial visit. In 5 of 21 cases we demonstrate the ability to detect B. burgdorferi in early Lyme disease directly from whole blood specimens prior to seroconversion.

BackgroundThe emergence and rapid spread of the 2009 H1N1 pandemic influenza A virus (H1N1pdm) in humans highlights the importance of enhancing the capability of existing influenza surveillance systems with tools for rapid identification of emerging and re-emerging viruses. One of the new approaches is the RT-PCR electrospray ionization mass spectrometry (RT-PCR/ESI-MS) technology, which is based on analysis of base composition (BC) of RT-PCR amplicons from influenza "core" genes. Combination of the BC signatures represents a "genomic print" of an influenza A virus.Methodology/principal findingsHere, 757 samples collected between 2006 and 2009 were tested, including 302 seasonal H1N1, 171 H3N2, 7 swine triple reassortants, and 277 H1N1pdm viruses. Of the 277 H1N1pdm samples, 209 were clinical specimens (throat, nasal and nasopharyngeal swabs, nasal washes, blood and sputum). BC signatures for the clinical specimen from one of the first cases of the 2009 pandemic, A/California/04/2009, confirmed it as an unusual, previously unrecognized influenza A virus, with "core" genes related to viruses of avian, human and swine origins. Subsequent analysis of additional 276 H1N1pdm samples revealed that they shared the genomic print of A/California/04/2009, which differed from those of North American swine triple reassortant viruses, seasonal H1N1 and H3N2 and other viruses tested. Moreover, this assay allowed distinction between "core" genes of co-circulating groups of seasonal H1N1, such as clades 2B, 2C, and their reassortants with dual antiviral resistance to adamantanes and oseltamivir.Conclusions/significanceThe RT-PCR/ESI-MS assay is a broad range influenza identification tool that can be used directly on clinical specimens for rapid and accurate detection of influenza virus genes. The assay differentiates the H1N1pdm from seasonal and other nonhuman hosts viruses. Although not a diagnostic tool, this assay demonstrates its usefulness and robustness in influenza virus surveillance and detection of novel and unusual viruses with previously unseen genomic prints.

Background: Lyme disease, caused by various species of Borrelia, is transmitted by Ixodes ticks in North America and Europe. Studies have shown the genotype of Borrelia burgdorferi sensu stricto (s.s.) or the species of B. burgdorferi sensu lato (s.l.) affects the ability of the bacteria to cause local or disseminated infection in humans. Methodology/Principal Findings: We used a multilocus PCR electrospray mass spectrometry assay to determine the species and genotype Borrelia from ticks collected in New York, Connecticut, Indiana, Southern Germany, and California and characterized isolates from parts of the United States and Europe. These analyses identified 53 distinct genotypes of B. burgdorferi sensu stricto with higher resolution than ospC typing. Genotypes of other members of the B. burgdorferi sensu lato complex were also identified and genotyped including B. afzelii, B. garinii, B. lusitaniae, B. spielmanii, and B. valaisiana. While each site in North America had genotypes unique to that location, we found genotypes shared between individual regions and two genotypes found across the United States. Significant B. burgdorferi s.s. genotypic diversity was observed between North America and Europe: only 6.6% of US genotypes (3 of 45) were found in Europe and 27% of the European genotypes (3 of 11) were observed in the US. Interestingly, 39% of adult Ixodes scapularis ticks from North America were infected with more than one genotype of B. burgdorferi s.s. and 22.2% of Ixodes ricinus ticks from Germany were infected with more than one genotype of B. burgdorferi s.l. Conclusions/Significance: The presence of multiple Borrelia genotypes in ticks increases the probability that a person will be infected with more than one genotype of B. burgdorferi, potentially increasing the risks of disseminated Lyme disease. Our study indicates that the genotypic diversity of Borrelia in ticks in both North America and Europe is higher then previously reported and can have potential clinical consequences.