Quantitative detection of Borrelia burgdorferi by real-time PCR

Microbial pathogens in ticks, rodents and a shrew in northern Gyeonggi-do near the DMZ, Korea

A total of 1,618 ticks [420 individual (adults) and pooled (larvae and nymphs) samples], 369 rodents (Apodemus agrarius, Rattus norvegicus, Tscherskia triton, Mus musculus, and Myodes regulus), and 34 shrews (Crocidura lasiura) that were collected in northern Gyeonggi-do near the Demilitarized Zone (DMZ) of Korea during 2004-2005, were assayed by PCR for selected zoonotic pathogens. From a total of 420 individual and pooled tick DNA samples, Anaplasma (A.) phagocytophilum (16), A. platys (16), Ehrlichia (E.) chaffeensis (63), Borrelia burgdorferi (16), and Rickettsia spp. (198) were detected using species-specific PCR assays. Out of 403 spleens from rodents and shrews, A. phagocytophilum (20), A. platys (34), E. chaffeensis (127), and Bartonella spp. (24) were detected with species-specific PCR assays. These results suggest that fevers of unknown causes in humans and animals in Korea should be evaluated for infections by these vector-borne microbial pathogens.

Adenoviral delivery of interleukin-10 fails to attenuate experimental Lyme disease

Production of interleukin-10 (IL-10) by C57BL/6 mice following infection with Borrelia burgdorferi has been proposed as a mechanism whereby resistance to the development of experimental Lyme arthritis is maintained. In the current study, we sought to determine the role of IL-10 during infection of arthritis- and carditis-susceptible C3H mice. Infection of C3H IL-10(-/-) mice led to increased joint swelling and arthritis severity scores over those of wild-type C3H mice. Measurement of B. burgdorferi numbers in joints or disseminated tissues indicated a more efficient clearance of spirochetes in the absence of IL-10, similar to that reported in C57BL/6 IL-10(-/-) mice. However, in contrast to previous in vitro work, infection of C3H IL-10(-/-) mice led to decreased in vivo expression of the cytokines KC, IL-1beta, IL-4, and IL-12p70 in the infected joints. Finally, adenoviral expression of IL-10 in the infected joints of C3H mice was unable to modulate the development of severe Lyme arthritis and had no effect on spirochete clearance or Borrelia-specific antibody production. Development of Lyme carditis appeared to be independent of modulation by IL-10. These results suggest that IL-10 limits the development of joint inflammation in both arthritis-resistant and -susceptible mouse strains infected with B. burgdorferi and that increased IL-10 production cannot rescue genetic susceptibility to development of pathology in this model.

Role of the BBA64 locus of Borrelia burgdorferi in early stages of infectivity in a murine model of Lyme disease

Borrelia burgdorferi, the causative agent of Lyme disease, undergoes rapid adaptive gene expression in response to environmental signals encountered during different stages of its life cycle in the arthropod vector or the mammalian host. Among all the plasmid-encoded genes of B. burgdorferi, several linear plasmid 54 (lp54)-encoded open reading frames (ORFs) exhibit the greatest differential expression in response to mammalian host-specific temperature, pH, and other uncharacterized signals. These ORFs include members of the paralogous gene family 54 (pgf 54), such as BBA64, BBA65, and BBA66, present on lp54. In an attempt to correlate transcriptional up-regulation of these pgf 54 members to their role in infectivity, we inactivated BBA64 and characterized the phenotype of this mutant both in vitro and in vivo. There were no major differences in the protein profiles between the BBA64 mutant and the control strains, while immunoblot analysis indicated that inactivation of BBA64 resulted in increased levels of BBA65. Moreover, there was no significant difference in the ability of the BBA64 mutant to infect C3H/HeN mice compared to that of its parental or complemented control strains as determined by culturing of viable spirochetes from infected tissues. However, enumeration of spirochetes using quantitative real-time PCR revealed tissue-specific differences, suggesting a minimal role for BBA64 in the survival of B. burgdorferi in select tissues. Infectivity analysis of the BBA64 mutant suggests that B. burgdorferi may utilize multiple determinants to establish infection in mammalian hosts.

A reverse transcriptase-polymerase chain reaction assay of Borrelia burgdorferi 16S rRNA for highly sensitive quantification of pathogen load in a vector

We developed a real-time quantitative detection assay for the pathogen Borrelia burgdorferi, a Lyme borreliosis (LB) agent, using reverse transcription-polymerase chain reaction (RT-PCR) with primers and probe for a Borrelia genus-specific region of 16S ribosomal RNA. The standard curve of the assay was linear by semi-log plot over more than five orders of magnitude, and the detection limit of the assay was one thousandth of a single cell of B. burgdorferi. The minimum target level for detection using the RT-PCR assay for 16S RNA was 40-fold lower than the RT-PCR assay for messenger RNA of ospA, a highly expressed, plasmid-borne gene, and 1600-fold lower than the RT-PCR assay for messenger RNA of p66, a chromosome-borne gene of B. burgdorferi. The 16S rRNA assay was then applied in an experimental setting for monitoring the spirochetal load in B. burgdorferi-infected Ixodes scapularis ticks before and after they fed on Peromyscus leucopus mice immunized with recombinant OspA. Unfed infected ticks had a mean of 2,240 spirochetes per tick, and after feeding on non-immunized mice and engorgement, the mean number of spirochetes increased to 223,900 per tick. In contrast, there were either no or <or=7 spirochetes in ticks that had fed on OspA-immunized mice.

Assessment of the kinetics of Treponema pallidum dissemination into blood and tissues in experimental syphilis by real-time quantitative PCR

Little is known about the size and kinetics of treponemal burdens in blood and tissues during acquired or experimental syphilitic infection. We used real-time quantitative PCR to measure Treponema pallidum DNA levels in rabbits infected intratesticularly with the prototype Nichols strain. At the outset, we performed a series of in vitro blood spiking experiments to determine the effect of blood processing procedures on the distribution of treponemes in various blood components. T. pallidum DNA levels in plasma and whole blood were approximately 10-fold higher than those in serum and more than 200-fold greater than those in peripheral blood mononuclear cells (PBMCs). Ten rabbits were inoculated intratesticularly with doses of treponemes ranging from 4 x 10(7) to 2 x 10(8) organisms. In five rabbits, T. pallidum DNA levels were measured sequentially in serum, plasma, whole blood, and PBMCs until sacrifice at peak orchitis, at which time brain, kidney, liver, spleen, and testicles were harvested; blood and organs were also harvested at orchitis from the other five rabbits. T. pallidum DNA was detected in plasma within 24 h postinfection. Treponeme levels in whole blood and blood components increased significantly with the development of peak orchitis. Overall, levels in serum and PBMCs were lower than those in plasma and whole blood; this disparity was particularly marked at early time points. Significantly greater numbers of spirochetes were found in the spleen than in liver, kidney, or brain tissue at the time of sacrifice. Our findings highlight the remarkable capacity of T. pallidum to disseminate from the site of infection to blood and tissues, and they identify the spleen as a prime target for treponemal invasion.

Analysis of close proximity quenching of phosphorescent metalloporphyrin labels in oligonucleotide structures

Quenching of phosphorescent platinum(II) and palladium(II) coproporphyrin (MeCP) labelled oligonucleotides was investigated. Strong hybridization-specific quenching was observed in duplex DNA structures with a variety of quenchers and with two identical porphyrin labels when in close proximity. Classical resonance energy transfer mechanism was ruled out, since quenching did not correlate with spectral overlaps and lifetime changes were insignificant. Quenching of MeCP by the free quenchers in solution revealed that porphyrin-porphyrin quenching is predominantly static while other dyes quench dynamically. The results suggest that the quenching in DNA duplex proceeds via direct contact.

Detection of Borrelia burgdorferi DNA in tissues from dogs with presumptive Lyme borreliosis

OBJECTIVE

To develop a quantitative PCR assay for detection of Borrelia burgdorferi DNA in formalin-fixed, paraffin-embedded tissues; compare results of this assay with results of immunohistochemical staining of tissues from seropositive dogs; and determine whether B burgdorferi DNA could be detected in renal tissues from dogs with presumptive Lyme nephritis.

DESIGN

Cohort study.

SAMPLE POPULATION

Archived tissue samples from 58 dogs.

PROCEDURES

A quantitative PCR assay was performed on formalin-fixed, paraffin-embedded tissue sections from the dogs. Results were compared with results of immunohistochemical staining, B burgdorferi serostatus, clinical signs, and necropsy findings.

RESULTS

38 dogs were classified as having positive or equivocal results for Lyme borreliosis, and 20 were classified as having negative results on the basis of clinical signs, serologic findings, and pathologic abnormalities. Borrelia burgdorferi DNA was amplified from tissue samples from only 4 (7%) dogs, all of which had been classified as having positive or equivocal results for Lyme borreliosis and had signs of presumptive Lyme nephritis. Results of PCR assays of renal tissue were positive for only 1 dog, and there was no agreement between results of immunohistochemical staining (ie, detection of B burgdorferi antigen) and results of the PCR assay (ie, detection of B burgdorferi DNA) for renal tissues.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that detection of B burgdorferi DNA in formalin-fixed, paraffin-embedded tissues is feasible, but that intact B burgdorferi DNA is rarely found in tissues from naturally infected dogs, even tissues from dogs with presumptive Lyme borreliosis. Further, findings support the contention that Lyme nephritis may be a sterile, immune complex disease.

Specific detection of residual CHO host cell DNA by real-time PCR

Chinese hamster ovary cells have been widely used to manufacture recombinant proteins for human therapeutic use. A sensitive quantitative real-time polymerase chain reaction assay for the detection of residual Chinese hamster (Cricetulus griseus) DNA is presented in this paper. The assay is reasonably affordable and can be adapted for high-throughput screening using 96-well format. Real-time PCR primers were designed to amplify a 150bp region of a genomic fragment from hamster DNA. The specificity of the probe was evaluated in real-time PCR reactions using genomic DNA from mouse fibroblast, human kidney and hamster ovary cell lines as template. Sensitivity of real-time PCR was compared on genomic DNA from hamster cell line CHO DG44. These primers can be used in real-time PCR reactions to detect presence of contaminating hamster DNA in purified protein samples down to sensitivity of 300fg genomic DNA.

A LightCycler TaqMan assay for detection of Borrelia burgdorferi sensu lato in clinical samples

Lyme disease (LD) is an infection caused by an ixodid tick-borne spirochete, Borrelia burgdorferi sensu lato. LD manifests itself as a multisystem inflammatory disease that affects the skin in its early localized stage and spreads to the joints, nervous system, heart, and, to a lesser extent, other organ systems in its later disseminated stages. If diagnosed and treated early with appropriate antibiotics, LD is almost always readily cured. Developing a highly sensitive and specific real-time polymerase chain reaction assay could be very useful in improving the diagnostic accuracy and decreasing turnaround time for results. We report the development of a LightCycler TaqMan assay targeting the OspA gene for clinical detection of B. burgdorferi sensu lato in various types of biologic samples. This assay was validated by testing a variety of clinical samples including cerebrospinal fluid, synovial fluid, skin biopsies, and blood and culture isolates from skin biopsies. The TaqMan testing results were 100% concordant with previously reported results. Reference strains representing isolates from other geographic regions were also successfully amplified. The developed assay is robust, is highly sensitive and specific for B. burgdorferi sensu lato, and is suitable for clinical detection of the bacterium in biologic samples.

Stat1 deficiency exacerbates carditis but not arthritis during experimental lyme borreliosis

Activation of the transcription factor Stat1 by interferon-gamma (IFN-gamma) is an important step in the development of antimicrobial effector mechanisms against many bacterial pathogens. Susceptibility to murine Lyme arthritis has been correlated with the production of several proinflammatory cytokines, especially IFN-gamma. To determine the role of IFN-mediated effector mechanisms in the development of Lyme borreliosis, we infected Stat1-deficient mice on both resistant (DBA), and susceptible (C3H) genetic backgrounds. Arthritis in Stat1(/) mice was similar to that of wild-type controls in both mouse strains. Spirochete loads in tissues were also unchanged in Stat1(/) mice. C3H Stat1(/) mice exhibited increased inflammation in the heart, whereas carditis was unchanged in DBA Stat1(/) mice. These results demonstrate that inhibition of macrophage activation and responses to IFN-gamma-mediated signaling do not alter the arthritis resistance or susceptibility phenotype; however, they do affect the severity of carditis in susceptible mouse strains.

Inactivation of the fibronectin-binding adhesin gene bbk32 significantly attenuates the infectivity potential of Borrelia burgdorferi

Borrelia burgdorferi, the aetiological agent of Lyme disease, utilizes multiple adhesins to interact with both the arthropod vector and mammalian hosts it colonizes. One such adhesive molecule is a surface-exposed fibronectin-binding lipoprotein, designated BBK32. Previous characterization of BBK32-mediated fibronectin binding has been limited to biochemical analyses due to the difficulty in mutagenizing infectious isolates of B. burgdorferi. Here we report an alternative method to inactivate bbk32 via allelic exchange through use of a low-passage variant of B. burgdorferi strain B31 that is more readily transformed. The resulting mutant does not synthesize BBK32, exhibits reduced fibronectin binding in solid phase assays and manifests decreased interactions with mouse fibroblast cells relative to both the infectious parent and genetic complement. Furthermore, the bbk32 knockout was significantly attenuated in the murine model of Lyme disease, whereas a genetically complemented control was not, indicating that BBK32 is necessary for maximal B. burgdorferi infection in the mouse. To our knowledge this is the first mutational analysis of a surface exposed, functional borrelial lipoprotein adhesin whose activity is associated with the mammalian host environment. By analogy with other pathogens that utilize fibronectin binding as an important virulence determinant, the borrelial fibronectin-BBK32 interaction is likely to be important in B. burgdorferi-specific pathogenic mechanisms, particularly in the context of dissemination, secondary colonization and/or persistence.

A small molecule alpha 4 beta 1 antagonist prevents development of murine Lyme arthritis without affecting protective immunity

After infection with Borrelia burgdorferi, humans and mice under certain conditions develop arthritis. Initiation of inflammation is dependent on the migration of innate immune cells to the site of infection, controlled by interactions of a variety of adhesion molecules. In this study, we used the newly synthesized compound S18407, which is a prodrug of the active drug S16197, to analyze the functional importance of alpha4beta1-dependent cell adhesion for the development of arthritis and for the antibacterial immune response. S16197 is shown to interfere specifically with the binding of alpha4beta(1 integrin to its ligands VCAM-1 and fibronectin in vitro. Treatment of B. burgdorferi-infected C3H/HeJ mice with the alpha4beta1 antagonist significantly ameliorated the outcome of clinical arthritis and the influx of neutrophilic granulocytes into ankle joints. Furthermore, local mRNA up-regulation of the proinflammatory mediators IL-1, IL-6, and cyclooxygenase-2 was largely abolished. Neither the synthesis of spirochete-specific Igs nor the development of a Th1-dominated immune response was altered by the treatment. Importantly, the drug also did not interfere with Ab-mediated control of spirochete load in the tissues. These findings demonstrate that the pathogenesis, but not the protective immune response, in Lyme arthritis is dependent on the alpha4beta1-mediated influx of inflammatory cells. The onset of inflammation can be successfully targeted by treatment with S18407.

Three multiplex assays for detection of Borrelia burgdorferi sensu lato and Borrelia miyamotoi sensu lato in field-collected Ixodes nymphs in North America

Two hundred fifty New Jersey field-collected Ixodes scapularis Say ticks and 17 Colorado Ixodes spinipalpis Hadwen & Nuttall ticks were tested using three separate multiplex real-time polymerase chain reaction (PCR) assays. One assay targets the rrs-rrlA IGS region of Borrelia spp. to detect Borrelia burgdorferi sensu lato (s.l.) and Borrelia miyamotoi s.l. The second assay targets the ospA region of B. burgdorferi s.l. to detect B. burgdorferi sensu stricto (s.s.), Borrelia bissettii, and Borrelia andersonii. The final assay targets the glpQ region of B. miyamotoi s.l. to differentiate B. miyamotoi LB-2001 and Borrelia lonestari. A testing scheme combining these tests yielded 18% of tested I. scapularis ticks surveyed from New Jersey positive for B. burgdorferi s.s., 3.2% I. scapularis ticks positive for B. miyamotoi LB-2001, and 41.2% I. spinipalpis ticks positive for B. bissettii surveyed from Colorado.

Monitoring Lactobacillus plantarum in grass silages with the aid of 16S rDNA-based quantitative real-time PCR assays

Ensiling plant material with the aid of lactic acid bacteria (LAB) is a common agricultural practice for conserving forages independently of the time point of harvest. Despite ensiling being a natural process, it can be improved by the treatment of the harvested forage with starter cultures before storage. Within this context, Lactobacillus plantarum (L. plantarum) is the most frequently used LAB in commercially available starter cultures. In order to enable the monitoring of the population dynamics of L. plantarum in silage, methods for species-specific detection based on the 16S ribosomal DNA (rDNA) sequence were developed by applying a quantitative real-time polymerase chain reaction (QRT-PCR) approach. The QRT-PCR assay was also applied to estimate the development of the L. plantarum population within experimental grass silages. In addition, a multiplex QRT-PCR assay was developed to estimate the amount of L. plantarum 16S rDNA in relation to total bacterial 16S rDNA. This multiplex QRT-PCR assay was applied to monitor the influence of different silage additives on the L. plantarum population.

Diagnosis of lyme borreliosis

A large amount of knowledge has been acquired since the original descriptions of Lyme borreliosis (LB) and of its causative agent, Borrelia burgdorferi sensu stricto. The complexity of the organism and the variations in the clinical manifestations of LB caused by the different B. burgdorferi sensu lato species were not then anticipated. Considerable improvement has been achieved in detection of B. burgdorferi sensu lato by culture, particularly of blood specimens during early stages of disease. Culturing plasma and increasing the volume of material cultured have accomplished this. Further improvements might be obtained if molecular methods are used for detection of growth in culture and if culture methods are automated. Unfortunately, culture is insensitive in extracutaneous manifestations of LB. PCR and culture have high sensitivity on skin samples of patients with EM whose diagnosis is based mostly on clinical recognition of the lesion. PCR on material obtained from extracutaneous sites is in general of low sensitivity, with the exception of synovial fluid. PCR on synovial fluid has shown a sensitivity of up to >90% (when using four different primer sets) in patients with untreated or partially treated Lyme arthritis, making it a helpful confirmatory test in these patients. Currently, the best use of PCR is for confirmation of the clinical diagnosis of suspected Lyme arthritis in patients who are IgG immunoblot positive. PCR should not be used as the sole laboratory modality to support a clinical diagnosis of extracutaneous LB. PCR positivity in seronegative patients suspected of having late manifestations of LB most likely represents a false-positive result. Because of difficulties in direct methods of detection, laboratory tests currently in use are mainly those detecting antibodies to B. burgdorferi sensu lato. Tests used to detect antibodies to B. burgdorferi sensu lato have evolved from the initial formats as more knowledge on the immunodominant antigens has been collected. The recommendation for two-tier testing was an attempt to standardize testing and improve specificity in the United States. First-tier assays using whole-cell sonicates of B. burgdorferi sensu lato need to be standardized in terms of antigen composition and detection threshold of specific immunoglobulin classes. The search for improved serologic tests has stimulated the development of recombinant protein antigens and the synthesis of specific peptides from immunodominant antigens. The use of these materials alone or in combination as the source of antigen in a single-tier immunoassay may someday replace the currently recommended two-tier testing strategy. Evaluation of these assays is currently being done, and there is evidence that certain of these antigens may be broadly cross-reactive with the B. burgdorferi sensu lato species causing LB in Europe.

Improving the specificity of 16S rDNA-based polymerase chain reaction for detecting Borrelia burgdorferi sensu lato-causative agents of human Lyme disease

AIMS

16S rDNA sequences of Borrelia burgdorferi sensu lato were aligned with the 16S rDNA sequences of Borrelia hermsii, Borrelia turicatae, and Borrelia lonestari in order to identify primers that might be used to more specifically identify agents of human Lyme disease in ticks in human skin samples.

METHODS AND RESULTS

Standard polymerase chain reaction (PCR), using an oligonucleotide sequence, designated TEC1, was shown, in combination with a previously developed primer (LD2) to amplify strains of B. burgdorferi sensu stricto, Borrelia afzelii, and Borrelia garinii, but not the non-Lyme causing B. hermsii or B. turicatae. This primer pair, designated Bbsl, was successfully used to amplify B. burgdorferi sensu lato from skin biopsies of patients with Lyme disease symptoms as well as from Ixodes scapularis, Amblyomma americanum and Dermacentor variabilis ticks.

CONCLUSIONS

The primer set Bbsl allows for the rapid detection and differentiation of B. burgdorferi sensu lato from non-Lyme disease-causing Borrelia species in ticks and human tissues.

SIGNIFICANCE AND IMPACT OF THE STUDY

The PCR primer set, Bbsl, will greatly facilitate detection of the causative agents of Lyme disease in infected ticks and human skin samples assisting in epidemiological studies, and potentially allowing for a more rapid diagnosis of the disease in patients.

NK cells contribute to the control of Trypanosoma cruzi infection by killing free parasites by perforin-independent mechanisms

The protozoan parasite Trypanosoma cruzi circulates in the blood as trypomastigotes and invades a variety of cells to multiply intracellularly as amastigotes. The acute phase leads to an immune response that restricts the proliferation of the parasite. However, parasites are able to persist in different tissues, which causes the pathology of Chagas' disease. Natural killer (NK) cells play an important role in innate resistance to a variety of pathogens. In the present study we analyzed whether NK cells participated in the control of experimental T. cruzi infection. NK cells were depleted from C57BL/6 mice by antiasialo antibodies. This treatment caused an increased parasitemia during the acute phase, but tissue parasite burdens were not significantly altered according to quantitative real-time PCR. Our results demonstrated that NK cells were activated during the initial phase of a T. cruzi infection and exhibited a contact-dependent antiparasitic activity against extracellular parasites that was independent from perforin. Thus, NK cells limit the propagation of the parasite by acting on circulating T. cruzi trypomastigotes.

Real-time Fluorescent PCR Techniques to Study Microbial-Host Interactions

This chapter describes how real-time polymerase chain reaction (PCR) performs and how it may be used to detect microbial pathogens and the relationship they form with their host. Research and diagnostic microbiology laboratories contain a mix of traditional and leading-edge, in-house and commercial assays for the detection of microbes and the effects they impart upon target tissues, organs, and systems. The PCR has undergone significant change over the last decade, to the extent that only a small proportion of scientists have been able or willing to keep abreast of the latest offerings. The chapter reviews these changes. It discusses the second-generation of PCR technology-kinetic or real-time PCR, a tool gaining widespread acceptance in many scientific disciplines but especially in the microbiology laboratory.

Detection of Haemophilus influenzae type b by real-time PCR

A real-time PCR assay targeting the capsulation locus of Haemophilus influenzae type b (Hib) was developed. The linear detection range was from 1 to 10(6) microorganisms per reaction mixture. No H. influenzae other than Hib or any other control bacteria typically found in the upper respiratory tract was detected.

Treatment of mice with the neutrophil-depleting antibody RB6-8C5 results in early development of experimental lyme arthritis via the recruitment of Gr-1- polymorphonuclear leukocyte-like cells

Recently, we demonstrated that blocking the entry of neutrophils into Borrelia burgdorferi-infected joints in mice deficient in the chemokine receptor CXCR2 prevented the development of experimental Lyme arthritis. Neutrophils were marginalized in blood vessels at the site of infection but could not enter the joint tissue. In the present study, we treated both genetically arthritis-resistant DBA/2J (DBA) and arthritis-susceptible C3H/HeJ (C3H) mice with the neutrophil-depleting monoclonal antibody RB6-8C5 (RB6) to determine the effect on arthritis development. Surprisingly, both DBA and C3H mice treated with RB6 developed arthritis at 1 week postinfection, approximately 1 week earlier than the control-treated C3H mice. The early development of arthritis in the RB6-treated mice was accompanied by an influx into the joints of cells with ring-shaped polymorphonuclear leukocyte (PMN) cell morphology that were negative for the Gr-1 neutrophil maturation marker. RB6 treatment of mice also resulted in increased numbers of B. burgdorferi cells in the joints at 7 days postinfection and earlier expression of the chemokines KC and monocyte chemoattractant protein 1 in the joints compared to control-treated animals. Together, these results suggest that recruitment of neutrophils or PMN-like cells into an infected joint is a key requirement for Lyme arthritis development and that altered recruitment of these cells into the joints of arthritis-resistant mice can exacerbate the development of pathology.

Complement C3 is required for the progression of cutaneous lesions and neutrophil attraction in Leishmania major infection

To elucidate the role of complement-mediated uptake in Leishmania major infection in vivo, transgenic BALB/c mice that express the cobra venom factor (CVF) under control of the alpha1-antitrypsin promoter were infected. CVF expression in these mice leads to a continuous activation and subsequent consumption of complement C3 in the serum. In contrast to susceptible non-transgenic BALB/c mice, CVF-transgenic mice are highly resistant to L. major infection and show a significantly reduced parasite dissemination. Transient depletion of C3 in wild-type BALB/c mice delays progression of lesions for some days. Both CVF-transgenic and non-transgenic mice exhibit similar T cell responses upon infection. However, in CVF-transgenic mice, no infiltration of neutrophils, which were the prominent infiltrating cells at the site of infection in normal susceptible mice, could be detected. We conclude that C3 cleavage is required for the attraction of neutrophils that participate in parasite dissemination.

Real-time PCR in the microbiology laboratory

Use of PCR in the field of molecular diagnostics has increased to the point where it is now accepted as the standard method for detecting nucleic acids from a number of sample and microbial types. However, conventional PCR was already an essential tool in the research laboratory. Real-time PCR has catalysed wider acceptance of PCR because it is more rapid, sensitive and reproducible, while the risk of carryover contamination is minimised. There is an increasing number of chemistries which are used to detect PCR products as they accumulate within a closed reaction vessel during real-time PCR. These include the non-specific DNA-binding fluorophores and the specific, fluorophore-labelled oligonucleotide probes, some of which will be discussed in detail. It is not only the technology that has changed with the introduction of real-time PCR. Accompanying changes have occurred in the traditional terminology of PCR, and these changes will be highlighted as they occur. Factors that have restricted the development of multiplex real-time PCR, as well as the role of real-time PCR in the quantitation and genotyping of the microbial causes of infectious disease, will also be discussed. Because the amplification hardware and the fluorogenic detection chemistries have evolved rapidly, this review aims to update the scientist on the current state of the art. Additionally, the advantages, limitations and general background of real-time PCR technology will be reviewed in the context of the microbiology laboratory.

Quantitative analysis of Borrelia burgdorferi gene expression in naturally (tick) infected mouse strains

Adaptation of Borrelia burgdorferi in the vector and vertebrate host is mediated by mechanisms that regulate differential expression of outer surface lipoproteins (Osps). In this study, real time PCR was applied to quantify tissue-specific expression of four linear plasmid (lp54)-encoded (ospA, zs7.a36, zs7.a66 zs7.a68) and one circular plasmid (cp26)-encoded (ospC) gene from B. burgdorferi sensu stricto, in a natural setting of tick-infected immunodeficient (C.B-17 SCID) and immunocompetent (BALB/c and AKR/OlaHsd) mice for up to 120 days post-infection (p.i.). Early during infection (day 30 p.i.) high numbers of spirochetes were found in the heart and joint, but not the ear and spleen tissues of disease-susceptible SCID mice. In disease-susceptible AKR mice spirochetes colonized the ear and joint tissues, but were undetectable in tissues of disease-resistant BALB/c mice. Later in infection (day 120 p.i.), spirochetes had expanded (approximately 1,000-fold) in all SCID tissues tested but were undetectable in AKR and BALB/c mice. Of the five genes analyzed, only zs7.a36 transcripts were detected in various tissues of all infected mouse strains, though at differing levels, whereas ospC transcripts were only found in tissue specimens of SCID mice. Furthermore, gene expression of ospC and zs7.a36 appears to be differentially regulated in distinct organs of individual mice. In contrast, transcripts for ospA, zs7.a66, and zs7.a68 were not detected in any of the mouse strains, independent of their immune status and/or the severity of their infection/inflammatory responses. Late during infection (day 120 p.i.), transcription of zs7.a36 and ospC was down-regulated in the tissues of SCID mice despite expansion of spirochetes. This type of quantitative analysis may be helpful to further disclose principles of pathogenesis of Lyme borreliosis and to design strategies for its therapeutic treatment.

Detection and differentiation of in vitro-spiked bacteria by real-time PCR and melting-curve analysis

We introduce a consensus real-time PCR protocol for the detection of bacterial DNA from laboratory-prepared specimens such as water, urine, and plasma. This prototype detection system enables an exact Gram stain classification and, in particular, screening for specific species of 17 intensive care unit-relevant bacteria by means of fluorescence hybridization probes and melting-curve analysis in a one-run experiment. One strain of every species was tested at a final density of 10(6) CFU/ml. All bacteria examined except Staphylococcus aureus and Staphylococcus epidermidis could be differentiated successfully; S. aureus and S. epidermidis could only be classified as "Staphylococcus species." The hands-on time for preparation of the DNA, performance of the PCR, and evaluation of the PCR results was less than 4 h. Nevertheless, this prototype detection system requires more clinical validation.

Induction of CYP1A by a diterpene quinone tanshinone IIA isolated from a medicinal herb Salvia miltiorrhiza in C57BL/6J but not in DBA/2J mice

Effects of tanshinone IIA, an active diterpene quinone of the herbal medicine Salvia miltiorrhiza (Danshen), on cytochrome P450 (CYP), UDP-glucuronosyl transferase (UGT), and glutathione S-transferase (GST) were studied in the arylhydrocarbon (Ah)-responsive C57BL/6J (B6) and nonresponsive DBA/2J (D2) mice. Oral treatment of tanshinone IIA caused a dose-dependent increase of liver microsomal 7-methoxyresorufin O-demethylation (MROD) activity in B6 but not in D2 mice. In B6 mice, tanshinone IIA increased hepatic benzo(a)pyrene hydroxylation (AHH), 7-ethoxyresorufin O-deethylation, MROD, and 7-ethoxycoumarin O-deethylation activities. The levels of Cyp1A2 protein and mRNA were elevated. On the contrary, in D2 mice, tanshinone IIA decreased hepatic AHH and nifedipine oxidation activities and the CYP3A protein level without affecting other activities determined. Cyp1A2 protein and mRNA levels were not affected by tanshinone IIA in D2 mice. Tanshinone IIA had no effects on UGT and GST activities in both B6 and D2 mice. These results demonstrated that induction of CYP1A2 by tanshinone IIA depended on the Ah-responsiveness and occurred at pre-translational level.

Direct detection methods for Lyme Borrelia, including the use of quantitative assays

Direct detection of Borrelia burgdorferi sensu lato, the etiologic agent of Lyme borreliosis, is the most reliable laboratory diagnostic tool. Several methods have been developed for direct detection of B. burgdorferi in infected vectors, host tissues, and clinical specimens from patients with Lyme borreliosis. These include microscope-based assays, antigen detection assays, in vitro cultivation, and nucleic acid-based detection of B. burgdorferi. The sensitivity and specificity of these methods depend on various factors and are also variable among laboratories. To date, only in vitro cultivation of B. burgdorferi has been widely accepted to confirm clinical diagnosis of Lyme borreliosis. Nevertheless, various polymerase chain reaction-based molecular assays have shown increasing significance in the laboratory diagnosis of Lyme borreliosis because of their high sensitivity, specificity, and capability for quantification and typing of spirochetes in clinical specimens. In this review, the currently available methods for direct detection of B. burgdorferi in clinical samples and quantitative analysis of spirochete load in different biological sources are discussed.

Real-time PCR for simultaneous detection and quantification of Borrelia burgdorferi in field-collected Ixodes scapularis ticks from the Northeastern United States

The density of spirochetes in field-collected or experimentally infected ticks is estimated mainly by assays based on microscopy. In this study, a real-time quantitative PCR (qPCR) protocol targeting the Borrelia burgdorferi-specific recA gene was adapted for use with a Lightcycler for rapid detection and quantification of the Lyme disease spirochete, B. burgdorferi, in field-collected Ixodes scapularis ticks. The sensitivity of qPCR for detection of B. burgdorferi DNA in infected ticks was comparable to that of a well-established nested PCR targeting the 16S-23S rRNA spacer. Of the 498 I. scapularis ticks collected from four northeastern states (Rhode Island, Connecticut, New York, and New Jersey), 91 of 438 (20.7%) nymphal ticks and 15 of 60 (25.0%) adult ticks were positive by qPCR assay. The number of spirochetes in individual ticks varied from 25 to 197,200 with a mean of 1,964 spirochetes per nymphal tick and a mean of 5,351 spirochetes per adult tick. No significant differences were found in the mean numbers of spirochetes counted either in nymphal ticks collected at different locations in these four states (P = 0.23 by one-way analysis of variance test) or in ticks infected with the three distinct ribosomal spacer restriction fragment length polymorphism types of B. burgdorferi (P = 0.39). A high degree of spirochete aggregation among infected ticks (variance-to-mean ratio of 24,877; moment estimate of k = 0.279) was observed. From the frequency distribution data and previously published transmission studies, we estimated that a minimum of 300 organisms may be required in a host-seeking nymphal tick to be able to transmit infection to mice while feeding on mice. These data indicate that real-time qPCR is a reliable approach for simultaneous detection and quantification of B. burgdorferi infection in field-collected ticks and can be used for ecological and epidemiological surveillance of Lyme disease spirochetes.

Isolation and detection of Borrelia burgdorferi DNA from cerebral spinal fluid, synovial fluid, blood, urine, and ticks using the Roche MagNA Pure system and real-time PCR

The Roche MagNA Pure automated nucleic acid extraction system was tested for its ability to extract Borrelia burgdorferi DNA from a diverse set of spiked specimen types including blood, cerebral spinal fluid, synovial fluid, urine and ticks. A method comparison between MagNA Pure automated extraction and manual extraction, using either QIAamp columns or phenol/chloroform extraction, showed equivalent detection sensitivities for all methodologies with all specimen types (except for urine, in which case QIAamp extraction was twofold less sensitive). Eighty positive clinical specimens (as determined by an independent testing method), including 76 synovial fluid, and 4 cerebral spinal fluid specimens, were found to be positive by the MagNA Pure/real-time PCR method of extraction and detection. This data shows that the MagNA Pure system can be used to extract B. burgdorferi DNA from clinical specimens, and when combined with real-time PCR, the result is an extremely sensitive assay with limited hands on time and rapid turn around times.

Interleukin-12 but not interleukin-18 is required for immunity to Trypanosoma cruzi in mice

Protective immunity to the parasite Trypanosoma cruzi in mice depends on a pro-inflammatory T cell response involving the production of interferon-gamma (IFN-gamma). In conjunction with interleukin-12 (IL-12), IL-18 promotes the synthesis of IFN-gamma and a T helper type 1 immune response. We investigated the requirements of IL-12 and IL-18 in murine T. cruzi infection by use of C57BL/6 mice genetically deficient in either cytokine. IL-12p40(-/-) mice succumbed to infection at doses of 100 parasites, whereas IL-18(-/-) and wild-type mice resisted infectious doses up to 1000 parasites to the same extent. Levels of parasitemia were comparable between the latter groups, as were tissue parasite burdens according to quantitative real-time PCR. In contrast, IL-12p40(-/-) mice displayed vastly increased levels of parasites both in blood and in tissue. IFN-gamma concentrations in the serum of infected mice and in supernatants of splenocytes stimulated in vitro were decreased in IL-18(-/-) mice, whereas in IL-12p40(-/-) mice, IFN-gamma was undetectable in the serum and drastically reduced in cell supernatants. Levels of IL-12 production were generally comparable between wild-type and IL-18(-/-) mice, as were levels of IL-4, IL-2 and nitric oxide. Thus, the requirement for endogenous pro-inflammatory cytokines for a protective murine immune response against T. cruzi is satisfied by the expression of IL-12, while IL-18 is dispensable.

Susceptibility to experimental Lyme arthritis correlates with KC and monocyte chemoattractant protein-1 production in joints and requires neutrophil recruitment via CXCR2

The development of experimental Lyme arthritis has been correlated with the expression of a number of chemokines and cytokines, however, none of these have been measured directly from the arthritic joint. We examined the temporal expression of IL-1beta, IL-4, IL-6, IL-10, IL-12p70, GM-CSF, IFN-gamma, TNF-alpha, macrophage inflammatory protein-2, KC, macrophage inflammatory protein-1alpha, and monocyte chemoattractant protein-1 directly from the tibiotarsal joint in arthritis-resistant C57BL/6 (B6) and -susceptible C3H/He (C3H) mice. Only the chemokines KC and monocyte chemoattractant protein-1 were differentially expressed in joints of B6 and C3H mice and correlated with the development of Lyme arthritis. Infection of CXCR2(-/-) mice on either genetic background resulted in a significant decrease in the development of pathology, although infection of CCR2(-/-) mice had little or no effect. Neutrophils in CXCR2(-/-) mice were marginalized within blood vessels and could not enter the joint tissue. These results suggest that chemokine-mediated recruitment of neutrophils into the infected joint is a key requirement for the development of experimental Lyme arthritis.

Murine susceptibility to Chagas' disease maps to chromosomes 5 and 17

Chagas' disease is caused by the protozoan parasite Trypanosoma cruzi and commonly modelled in inbred mice. Susceptibility of mouse strains to experimental infection varies considerably. We quantified parasite tissue burdens in resistant and susceptible strains by real time PCR and applied a backcross strategy to map the genomic loci linked to susceptibility in inbred mice. Resistant B6D2F1 mice were backcrossed with susceptible C57BL/6 mice, and 46 of a total 192 offspring died after infection. Their genomes were scanned with microsatellite markers. One region on chromosome 17 was significantly linked to susceptibility, while another on chromosome 5 was suggestive of linkage.

An analysis of spirochete load, strain, and pathology in a model of tick-transmitted Lyme borreliosis

Four laboratory-grown, low-passage isolates of Borrelia burgdorferi sensu stricto, B31, JD-1, 910255, and N40, were incorporated into Ixodes scapularis ticks to examine the pathogenesis of these isolates in mice after tick transmission. All isolates induced multifocal, lymphoid nodular cystitis, subacute, multifocal, necrotizing myocarditis, and a localized periostitis and arthritis of the femorotibial joint 6-18 weeks after tick infestation. In terms of the number of mice that demonstrated pathology in bladder, heart, and joint, the highest incidence of lesions occurred 12 weeks after tick bite. Utilizing the Taqman quantitative polymerase chain reaction (q-PCR) fluorogenic detection technology to amplify a conserved region of the flagellin gene, a trend was demonstrated between the number of spirochetes in tissue with duration of pathology. The q-PCR assay developed for this study was sensitive and could reliably measure as few as 1 to 10 spirochetes in the target tissues tested. A higher percentage of B31- and N40-infected mice (92 and 100%, respectively) developed myocarditis than JD-1- or 910255-infected mice (67 and 46%, respectively) 12 weeks after tick bite. The amount of spirochetal DNA that could be amplified for heart at this time point was not statistically different between isolates, indicating a difference in virulence between B31 and N40 relative to JD-1 and 910225. N40-infected mice demonstrated a significantly higher spirochete load (an average of 1.23 spirochetes/mg of tissue, p = 0.045) in femorotibial joints 18 weeks after infection, with 60% of these mice maintaining lesions compared with those infected with B31 (13%), JD-1 (25%), or 910255 (50%), which averaged <0.5 spirochetes/mg of tissue. This mouse model of Lyme borreliosis, including the ability to monitor lesion development and spirochete load, can facilitate the testing of therapeutic regimens for the later stages of tick-transmitted Lyme disease and help investigate aspects of the immunopathogenesis of lesion development.

Quantitative detection of Moraxella catarrhalis in nasopharyngeal secretions by real-time PCR

The recognition of Moraxella catarrhalis as an important cause of respiratory tract infections has been protracted, mainly because it is a frequent commensal organism of the upper respiratory tract and the diagnostic sensitivity of blood or pleural fluid culture is low. Given that the amount of M. catarrhalis bacteria in the upper respiratory tract may change during infection, quantification of these bacteria in nasopharyngeal secretions (NPSs) by real-time PCR may offer a suitable diagnostic approach. Using primers and a fluorescent probe specific for the copB outer membrane protein gene, we detected DNA from serial dilutions of M. catarrhalis cells corresponding to 1 to 10(6) cells. Importantly, there was no difference in the amplification efficiency when the same DNA was mixed with DNA from NPSs devoid of M. catarrhalis. The specificity of the reaction was further confirmed by the lack of amplification of DNAs from other Moraxella species, nontypeable Haemophilus influenzae, H. influenzae type b, Streptococcus pneumoniae, Streptococcus oralis, Streptococcus pyogenes, Bordetella pertussis, Corynebacterium diphtheriae, and various Neisseria species. The assay applied to NPSs from 184 patients with respiratory tract infections performed with a sensitivity of 100% and a specificity of up to 98% compared to the culture results. The numbers of M. catarrhalis organisms detected by real-time PCR correlated with the numbers detected by semiquantitative culture. This real-time PCR assay targeting the copB outer membrane protein gene provided a sensitive and reliable means for the rapid detection and quantification of M. catarrhalis in NPSs; may serve as a tool to study changes in the amounts of M. catarrhalis during lower respiratory tract infections or following vaccination against S. pneumoniae, H. influenzae, or N. meningitidis; and may be applied to other clinical samples.

Real-time PCR for detection and differentiation of gram-positive and gram-negative bacteria

We developed a consensus real-time PCR protocol that enables us to detect spiked bacterial 16S DNA from specimens such as water, urine, plasma, and sputum. The technique allows an exact Gram stain classification of 17 intensive care unit-relevant bacteria by means of fluorescence hybridization probes. All tested bacteria were identified correctly, and none gave a false-positive signal with the opposite Gram probe.

Use of both 16S rRNA and engineered functional genes with real-time PCR to quantify an engineered, PCB-degrading Rhodococcus in soil

A real-time PCR (RTm-PCR) assay using fluorescently labeled oligonucleotides (TaqMan probes) was used to detect and quantify the recombinant Rhodococcus sp. strain RHA1(fcb) in soil. One primer and probe set targeted a hypervariable region of the 16S rRNA gene unique to strain RHA1(fcb) and its phylogenetic relatives, and the other set targeted the recombinant 4-chlorobenzoate (4-CBA) degradation operon (fcb) and was strain-specific. The method had a 6-log dynamic range of detection (10(2)-10(7) cells ml(-1)) for both probes when DNA from pure cultures was used. Although the method was less sensitive in soil, the estimated number of cells in soil by real-time PCR corresponded to the measured number of RHA1(fcb) cells determined by colony-forming units.

Disease severity in a murine model of lyme borreliosis is associated with the genotype of the infecting Borrelia burgdorferi sensu stricto strain

The pathogenicity of Borrelia burgdorferi sensu stricto clinical isolates representing 2 distinct ribosomal DNA spacer restriction fragment-length polymorphism genotypes (RSTs) was assessed in a murine model of Lyme disease. B. burgdorferi was recovered from 71.5% and 26.6% of specimens from mice infected with RST1 and RST3 isolates, respectively (P<.0001). The average ankle diameter and histologic scores for carditis and arthritis were significantly higher after 2 weeks of infection among mice infected with RST1 isolates than among those infected with RST3 isolates (P<.001). These clinical manifestations were associated with larger numbers of spirochetes in target tissues but not with the serum sensitivity of the individual isolates. Thus, the development and severity of disease in genetically identical susceptible hosts is determined mainly by the pathogenic properties of the infecting B. burgdorferi isolate. The RST1 genotype is genetically homogeneous and thus may represent a recently evolved clonal lineage that is highly pathogenic in humans and animals.

Evaluation of antibiotic susceptibilities of three rickettsial species including Rickettsia felis by a quantitative PCR DNA assay

Rickettsiae grow only intracellularly, and the antibiotic susceptibilities of these bacteria have been assessed by either plaque, dye uptake, or immunofluorescence assays, which are time-consuming. We used a quantitative PCR (with the LightCycler instrument) to assess the levels of inhibition of Rickettisa felis, R. conorii, and R. typhi DNA synthesis in the presence of various antibiotics. We established the kinetics of rickettsial DNA during growth and showed that R. conorii grows more quickly than R. typhi in cell culture, with maximum replication occurring after 5 and 7 days, respectively. The MICs of the antibiotics tested for R. conorii and R. typhi by the quantitative PCR assay were similar to those previously obtained by plaque and dye uptake assays. We found that R. felis is susceptible to doxycycline, rifampin, thiamphenicol, and fluoroquinolones but not to gentamicin, erythromycin, amoxicillin, or trimethoprim-sulfamethoxazole. The resistance of this new species to erythromycin is consistent with its current taxonomic position within the spotted fever group. We believe that quantitative PCR could be used in the future to simplify and shorten antibiotic susceptibility assays of other rickettsiae and other strict intracellular pathogens.

A method for the rapid construction of cRNA standard curves in quantitative real-time reverse transcription polymerase chain reaction

Quantification of nucleic acids, especially of mRNA, is increasingly important in biomedical research. The recently developed quantitative real-time polymerase chain reaction (PCR) - a highly sensitive technology for the rapid, accurate and reproducible quantification of gene expression - offers major advantages over conventional quantitative PCR. Transcript quantification is performed in the exponential phase of the PCR reaction through extrapolation of fluorescence signals from a standard calibration curve which represents the initial copy number for a given fluorescence signal. We have developed a method for gene transcript quantification which is based on a LightCycler - assisted real-time PCR in combination with a simple and rapid approach for the construction of external cRNA standards with identical gene sequences as the target gene. Synthesis of cRNAs was performed by in vitro transcription with T7 RNA polymerase followed by reverse transcription and real-time PCR. We applied this approach for transcript quantification of eukaryotic initiation factor 3 p110 (EIF3S8) mRNA in normal testicular tissue. We also present a rapid and simple strategy for the construction of cRNA standards for use in real-time PCR.

Quantitative detection of Borrelia burgdorferi in 2-millimeter skin samples of erythema migrans lesions: correlation of results with clinical and laboratory findings

Variability of disease manifestations has been noted in patients with Lyme disease. A contributing factor to this variation may be the number of spirochetes present in infected patients. We evaluated clinical and laboratory findings for patients with erythema migrans with regard to the number of Borrelia burgdorferi organisms detected by quantitative PCR (qPCR) in 2-mm skin biopsy specimens. B. burgdorferi was detected in 80% (40 of 50) of the specimens tested; the mean number of spirochetes in these specimens ranged over 3 orders of magnitude (10 to 11,000 spirochetes per 2-mm biopsy specimen). Larger numbers of spirochetes were significantly associated with a shorter duration of the erythema migrans skin lesion (P = 0.020), smaller skin lesions (P = 0.020), and infection with a specific genotype of B. burgdorferi (P = 0.008) but not with the number or severity of symptoms. Skin culture positivity was significantly associated with skin lesions containing larger numbers of spirochetes (P = 0.019).

Tick-borne diseases in transfusion medicine

Ticks are effective vectors of viral, bacterial, rickettsial and parasitic diseases. Many of the tick-borne diseases (TBDs) are of significance to transfusion medicine, either because of the risks they pose to the blood supply or the necessity for blood products required in their treatment. The transmission of tick-borne pathogens via blood transfusion is of global concern. However, among transfusion medicine practitioners, experience with most of these microorganisms is limited. Transfusion transmission of TBDs has been documented largely by means of single case reports. A better understanding of the epidemiology, biology and management of this group of diseases is necessary in order to assess the risks they pose to the blood supply and to help guide effective prevention strategies to reduce this risk. Unique methods are required to focus on donor selection, predonation questioning, mass screening and inactivation or eradication procedures. The role of the transfusion medicine service in their treatment also needs to be better defined. This article reviews the growing body of literature pertaining to this emerging field of transfusion medicine and offers some recommendations for transfusionists in dealing with TBDs.

Distribution of clinically relevant Borrelia genospecies in ticks assessed by a novel, single-run, real-time PCR

A LightCycler-based PCR protocol was developed which targets the ospA gene for the identification and quantification of the different Borrelia burgdorferi sensu lato species in culture and in ticks, based on the use of a fluorescently labeled probe (HybProbe) and an internally labeled primer. The detection limit of the PCR was 1 to 10 spirochetes. A melting temperature determined from the melting curve of the amplified product immediately after thermal cycling allowed the differentiation of the three different B. burgdorferi sensu lato genospecies (B. burgdorferi sensu stricto, Borrelia garinii, and Borrelia afzelii) that are clinically relevant in Europe in a single PCR run. This method represents a simplified approach to study the association of different Borrelia species in ticks, the risk of Lyme borreliosis, and the putatively species-specific clinical sequelae. To determine the reliability of the real-time PCR protocol, we studied the prevalence of B. burgdorferi sensu lato infection in Ixodes ricinus ticks. A total of 1,055 ticks were collected by flagging vegetation in five different sites in the region of Konstanz (south Germany) and were examined for the distribution of B. burgdorferi species by real-time PCR. The mean infection rate was 35%. Of 548 adult ticks, 40% were positive, and of 507 nymphs, 30% were positive. The predominant genospecies (with 18% mixed infections) in the examined areas was B. afzelii (53%), followed by B. garinii (18%) and B. burgdorferi sensu stricto (11%); 0.8% of the infecting Borrelia could not be identified.

Use of quantitative PCR to measure density of Borrelia burgdorferi in the midgut and salivary glands of feeding tick vectors

Quantitative real-time PCR was used to assay spirochetes in feeding ticks. Spirochetes in tick midguts increased sixfold, from 998 per tick before attachment to 5,884 at 48 h of attachment. Spirochetes in tick salivary glands increased >17-fold, from 1.2 per salivary gland pair before feeding to 20.8 at 72 h postattachment. The period of the most rapid increase in the number of spirochetes in the salivary glands occurred from 48 to 60 h postattachment; this time period coincides with the maximal increase in transmission risk during nymphal tick feeding.

Quantitative detection of Streptococcus pneumoniae in nasopharyngeal secretions by real-time PCR

Streptococcus pneumoniae is an important cause of community-acquired pneumonia. However, in this setting the diagnostic sensitivity of blood cultures is below 30%. Since during such infections changes in the amounts of S. pneumoniae may also occur in the upper respiratory tract, quantification of these bacteria in nasopharnygeal secretions (NPSs) may offer a suitable diagnostic approach. Real-time PCR offers a sensitive, efficient, and routinely reproducible approach to quantification. Using primers and a fluorescent probe specific for the pneumolysin gene, we were able to detect DNA from serial dilutions of S. pneumoniae cells in which the quantities of DNA ranged from the amounts extracted from 1 to 10(6) cells. No difference was noted when the same DNA was mixed with DNA extracted from NPSs shown to be deficient of S. pneumoniae following culture, suggesting that this bacterium can be detected and accurately quantitated in clinical samples. DNAs from Haemophilus influenzae, Moraxella catarrhalis, or alpha-hemolytic streptococci other than S. pneumoniae were not amplified or were only weakly amplified when there were > or =10(6) cells per reaction mixture. When the assay was applied to NPSs from patients with respiratory tract infections, the assay performed with a sensitivity of 100% and a specificity of up to 96% compared to the culture results. The numbers of S. pneumoniae organisms detected by real-time PCR correlated with the numbers detected by semiquantitative cultures. A real-time PCR that targeted the pneumolysin gene provided a sensitive and reliable means for routine rapid detection and quantification of S. pneumoniae present in NPSs. This assay may serve as a tool to study changes in the amounts of S. pneumoniae during lower respiratory tract infections.

Routine diagnosis of Borrelia burgdorferi (sensu lato) infections using a real-time PCR assay

OBJECTIVE

To establish a one-tube fluorogenic real-time PCR assay for routine detection of Borrelia burgdorferi (sensu lato) DNA in various clinical specimens.

METHODS

A fragment of the flagellin gene sequence was amplified with the TaqMan chemistry using primers and a probe common to Borrelia burgdorferi sensu stricto, Borrelia afzelii, Borrelia garinii and Borrelia valaisiana. A recombinant plasmid containing the chromosomal gene coding for the flagellin protein was used as standard.

RESULTS

The specificity of the assay was documented with 48 different clinically relevant Borrelia burgdorferi strains. No cross-reaction occurred with unrelated bacteria, viruses and fungi. At an analytic sensitivity of 10 copies, excellent precision within runs and between runs was observed. The potential presence of inhibitors of the Taq DNA polymerase was monitored by spiking aliquots of each sample with a plasmid containing the target sequence. Among 56 cerebrospinal fluid samples taken from 54 patients with clinical suspicion of neuroborreliosis, one (1.8%) tested positive for Borrelia burgdorferi sensu lato DNA. Borrelia burgdorferi DNA was also detected in five (17.9%) of 28 synovial fluid specimens and in one (20%) of five synovial membrane biopsies obtained from 31 patients with arthropathies. In order to test for the absence of false-positive results, 84 samples from 83 patients without evidence of Lyme disease were investigated. None of these samples showed measurable amounts of Borrelia burgdorferi DNA.

CONCLUSION

By its established features, such as speed, reliability, sensitivity, specificity, the inclusion of carryover prevention and the monitoring of inhibitors in individual test tubes, this real-time PCR assay has proved to be a potent tool for the detection of Borrelia burgdorferi DNA under routine conditions in diagnostic laboratories.

Lyme disease in children

Lyme borreliosis is a multisystem disorder caused by Borrelia burgdorferi and transmitted by ticks in the northern hemisphere. The disease is common in children. In addition to frequently recognized manifestations such as erythema migrans, neuroborreliosis, and Lyme arthritis, rarer manifestations, including eye and ear disease, are increasingly understood. Clinical diagnosis is supported by serologic confirmation. Improvement of laboratory methodology, especially polymerase chain reaction-based tests, is continuing. Actual treatment recommendations based on controlled studies reflect expanding scientific knowledge. In the United States, license of a vaccine to prevent infection in children is awaited. Lyme borreliosis is an intriguing human example of bacterial persistence in the presence of the host immune system. Chronic Lyme arthritis is a model of chronic arthritis resembling forms of arthritis of unknown cause, such as rheumatoid arthritis and juvenile idiopathic arthritis.

Impact of genotypic variation of Borrelia burgdorferi sensu stricto on kinetics of dissemination and severity of disease in C3H/HeJ mice

Various genotypes of Borrelia burgdorferi sensu stricto have been previously identified among a large collection of isolates cultured from patients with Lyme disease in the United States. Furthermore, association of specific genotypes with hematogenous dissemination early in the disease course has been observed. The present study assessed kinetics of spirochete dissemination and disease severity in C3H/HeJ mice infected with two different genotypes of B. burgdorferi. Spirochete load in plasma and ear and other tissue samples of infected mice was measured by quantitative PCR, and these data were compared to those obtained by culture and histopathologic analysis. In mice infected with isolate BL206 (a type 1 strain), the peak number of spirochetes was observed in plasma between day 4 and 7, in heart and ear tissue on day 14, and in joints on day 28 postinoculation. There was a correlation between the peak number of spirochetes in plasma on day 4 or 7 and that in ear biopsy and joint specimens on day 14. By contrast, spirochete burdens in plasma of mice infected with isolate B356 (a type 3 strain) were 16- and 5-fold lower than those of BL206-infected mice on days 7 and 14 of infection, respectively. Similarly, approximately 6- and 13-fold fewer spirochetes were detected in the heart tissues of B356-infected mice compared to BL206-infected mice. Histopathologically, severe arthritis and aortitis were noted only in mice infected with isolate BL206. Spirochete dissemination and disease severity vary significantly in mice infected with distinct genotypes of B. burgdorferi, suggesting that genotypic differences in the infecting spirochetes play a key role in the pathogenesis and development of clinical disease.

Sensitive detection of Borrelia burgdorferi sensu lato DNA and differentiation of Borrelia species by LightCycler PCR

In order to differentiate species within the Borrelia burgdorferi sensu lato complex, LightCyler PCR and melting-curve analysis of the amplicons of two genes with intraspecies variability, the p66 gene and the recA gene, were performed. It was demonstrated that nested LightCycler PCR amplification of p66 is more sensitive in the detection of borrelia DNA than amplification of the recA gene. B. burgdorferi sensu stricto could be differentiated from Borrelia garinii and Borrelia afzelii by melting-curve analysis of the p66 gene amplicon. B. garinii could be differentiated from B. afzelii and B. burgdorferi sensu stricto by melting-curve analysis of the recA gene amplicon. Therefore, the PCRs complement each other in subtyping different Borrelia species, and combined LightCycler PCR and melting-curve analysis of both target genes is a rapid method to distinguish the three species of B. burgdorferi sensu lato.

Ticks and tickborne bacterial diseases in humans: an emerging infectious threat

Ticks are currently considered to be second only to mosquitoes as vectors of human infectious diseases in the world. Each tick species has preferred environmental conditions and biotopes that determine the geographic distribution of the ticks and, consequently, the risk areas for tickborne diseases. This is particularly the case when ticks are vectors and reservoirs of the pathogens. Since the identification of Borrelia burgdorferi as the agent of Lyme disease in 1982, 15 ixodid-borne bacterial pathogens have been described throughout the world, including 8 rickettsiae, 3 ehrlichiae, and 4 species of the Borrelia burgdorferi complex. This article reviews and illustrate various aspects of the biology of ticks and the tickborne bacterial diseases (rickettsioses, ehrlichioses, Lyme disease, relapsing fever borrelioses, tularemia, Q fever), particularly those regarded as emerging diseases. Methods are described for the detection and isolation of bacteria from ticks and advice is given on how tick bites may be prevented and how clinicians should deal with patients who have been bitten by ticks.