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

Progress in the molecular diagnosis of Lyme disease

INTRODUCTION

Current laboratory testing of Lyme borreliosis mostly relies on serological methods with known limitations. Diagnostic modalities enabling direct detection of pathogen at the onset of the clinical signs could overcome some of the limitations. Molecular methods detecting borrelial DNA seem to be the ideal solution, although there are some aspects that need to be considered. Areas covered: This review represent summary and discussion of the published data obtained from literature searches from PubMed and The National Library of Medicine (USA) together with our own experience on molecular diagnosis of Lyme disease. Expert commentary: Molecular methods are promising and currently serve as supporting diagnostic testing in Lyme borreliosis. Since the field of molecular diagnostics is under rapid development, molecular testing could become an important diagnostic modality.

A Novel Isothermal Assay of Borrelia burgdorferi by Recombinase Polymerase Amplification with Lateral Flow Detection

A novel isothermal detection for recombinase polymerase amplification with lateral flow (LF-RPA) was established for Borrelia burgdorferi (B. burgdorferi) detection in this study. This assay with high sensitivity and specificity can get a visible result without any additional equipment in 30 min. We designed a pair of primers according to recA gene of B. burgdorferi strains and a methodology evaluation was performed. The results showed that the RPA assay based on the recA gene was successfully applied in B. burgdorferi detection, and its specific amplification was only achieved from the genomic DNA of B. burgdorferi. The detection limit of the new assay was about 25 copies of the B. burgdorferi genomic DNA. Twenty Lyme borreliosis patients’ serum samples were detected by LF-RPA assay, real-time qPCR and nested-PCR. Results showed the LF-RPA assay is more effective than nested-PCR for its shorter reaction time and considerably higher detection rate. This method is of great value in clinical rapid detection for Lyme borreliosis. Using the RPA assay might be a megatrend for DNA detection in clinics and endemic regions.

Borrelia Genotyping in Lyme Disease

Borrelia burgdorferisensu lato is the causative agent of Lyme borreliosis, multisystem disorder characterized by a wide spectrum of clinical manifestations. Different borrelia species can lead to distinct clinical presentations, but some species were associated with defined clinical manifestation likeBorrelia afzeliiwith skin manifestations,Borrelia gariniiwith central nervous system disorders andBorrelia burgdorferisensu stricto with Lyme arthritis.Ixodesticks represent the main vectors ofB. burgdorferisensu lato; wild animals, lizards and birds are the natural reservoir of borrelia. Genotyping of borrelia strains is of great importance for epidemiological, clinical, and evolutionary studies. Numerous methods are available for the genotyping ofB. burgdorferisensu lato based either on whole genome or PCR based typing. Typing methods differ in their approach and target, many of them were implemented more or less successfully for diagnostic purposes.

Evaluation of molecular methods for detection of Borrelia burgdorferi senso lato in ticks

Borrelia burgdorferi sensu lato (s. l.), the agent of Lyme disease, is distributed widely worldwide. A large number of polymerase chain reaction (PCR) methods have been developed and used for detection of B. burgdorferi s. l. However, there is a lack of a reference standard because of the genetic diversity of the B. burgdorferi s. l. complex. In this study, 4 PCR methods, based on the OspA, flagellin, rrs, and P66 genes, for detection of B. burgdorferi s. l. were evaluated by detection of genomic DNA from 3 reference genospecies and tick samples. The sensitivity of the PCR methods was analyzed using serially diluted gDNA from B. afzelii (Bo23), B. burgdorferi sensu stricto (B31), and B. garinii (PBi). The performance of the PCRs was evaluated by detection of the gDNA of 543 ticks. The results showed that the PCRs targeting the OspA gene, fla gene, rrs gene, and P66 gene detected 37 (6.8%), 74 (13.6%), 16 (2.9%), and 14 (2.6%) tick samples, respectively. The PCR targeting the fla gene was the most sensitive method for the detection of B. burgdorferi s. l.

Detection and differentiation of coccidian oocysts by real-time PCR and melting curve analysis

Rapid and reliable detection and identification of coccidian oocysts are essential for animal health and foodborne disease outbreak investigations. Traditional microscopy and morphological techniques can identify large and unique oocysts, but they are often subjective and require parasitological expertise. The objective of this study was to develop a real-time quantitative PCR (qPCR) assay using melting curve analysis (MCA) to detect, differentiate, and identify DNA from coccidian species of animal health, zoonotic, and food safety concern. A universal coccidia primer cocktail was designed and employed to amplify DNA from Cryptosporidium parvum, Toxoplasma gondii, Cyclospora cayetanensis, and several species of Eimeria, Sarcocystis, and Isospora using qPCR with SYBR Green detection. MCA was performed following amplification, and melting temperatures (T(m)) were determined for each species based on multiple replicates. A standard curve was constructed from DNA of serial dilutions of T. gondii oocysts to estimate assay sensitivity. The qPCR assay consistently detected DNA from as few as 10 T. gondii oocysts. T(m) data analysis showed that C. cayetanensis, C. parvum, Cryptosporidium muris, T. gondii, Eimeria bovis, Eimeria acervulina, Isospora suis, and Sarcocystis cruzi could each be identified by unique melting curves and could be differentiated based on T(m). DNA of coccidian oocysts in fecal, food, or clinical diagnostic samples could be sensitively detected, reliably differentiated, and identified using qPCR with MCA. This assay may also be used to detect other life-cycle stages of coccidia in tissues, fluids, and other matrices. MCA studies on multiple isolates of each species will further validate the assay and support its application as a routine parasitology screening tool.

Evaluation of real-time PCR targeting hbb gene for Borrelia species identification

Several molecular methods have been employed for Borrelia species identification. Newly developed technology, real-time polymerase chain reaction (RT-PCR), combines simultaneous amplification, detection and differentiation of strains in one PCR run. The aim of the study was to perform and evaluate RT-PCR for Borreliaburgdorferi sensu lato species identification. Borrelia species identification was accomplished on 374 Borrelia strains using two approaches: 1.) MluI restriction of entire borrelial chromosome (MluI-large restriction fragment patterns, LRFP), and 2.) RT-PCR targeting hbb gene and specific melting temperature (Tm) detection. The results of the two molecular methods were compared. With MluI-RFLP we were able to differentiate all Borrelia species and their subtypes within particular species. RT-PCR based on Tm determination identified unique strains within the species Borreliaafzelii (Tm 66.11 degrees C), B. burgdorferi sensu stricto (Tm 68.18 degrees C), Borreliaspielmanii (Tm 59.45 degrees C) and Borreliavalaisiana (Tm 59.62 degrees C). We were not able to distinguish the last two species that shared almost identical Tm. The large majority of Borreliagarinii strains shared Tm 51.42 degrees C, while subtype Mlg4 was characterized by Tm 56.87 degrees C. Strains of Borrelialusitaniae species also were heterogeneous; human isolate had Tm 63.47 degrees C while two tick isolates shared Tm 61.77 degrees C. Differences inside hbb gene enabled differentiation of the majority of Borrelia species, and revealed two clusters within B. garinii and B. lusitaniae species, respectively, but it was not possible to distinguish B. spielmanii form B. valaisiana. The major advantage of RT-PCR was that it was easy to perform and that the results were obtained within a few hours.

Examination of specific DNA by PCR in patients with different forms of Lyme borreliosis

BACKGROUND

Borrelial specific DNA was examined in a group of 62 patients with different forms of Lyme borreliosis (LB) (32 patients suffered from neuroborreliosis, 19 manifested erythema migrans, and 11 joint involvement).

METHODS

Nested-PCR system with five newly derived primers was used in parallel. The study was organized prospectively, the presence of DNA was tested for plasma, CSF, joint fluid and urine before treatment, and plasma, joint fluid and urine were examined after treatment.

RESULTS

Before therapy, 36 patients (58.1%) were DNA positive on the whole; 21 positive patients (65.6%) were found in the group of neuroborreliosis, 8 (42.1%) showed signs of skin involvement, and 7 (63.6%) were positive in arthritis. After treatment, 11 patients (36.7%) were positive in neuroborreliosis, 3 (17.6%) in skin form, and 6 (54.5%) in joint form of LB. Among 97 positive amplifications the most frequent target was found in primer corresponding with 16S rDNA (50 samples, 51.5%). Lower but very similar results were obtained with primers for OspA (18 positive amplifications; 18.6%), OspC (13 positive amplifications; 13.4%), and flagellin (13 positive amplifications; 13.4%). There were 11 patients in whom only DNA and no specific antibodies were found.

CONCLUSIONS

Specific DNA was found in all clinical groups of LB with similar sensitivity. Examination of the borrelial DNA in urine displayed the same sensitivity as in CSF and had a two times higher sensitivity than in plasma.

Molecular and serological evidence of Borrelia burgdorferi sensu lato in wild rodents in the Czech Republic

The aim of the present study was to determine the frequency and spatial distribution of the Borrelia species in wild rodents in the Czech Republic. In total, 293 muscle tissue samples and 106 sera from 293 wild rodents captured in North Bohemia and North-East and South Moravia were examined for the presence of Borrelia spp. and antibodies. Muscle samples were investigated with real-time polymerase chain reaction (PCR) with a recA primer set, with DNA quantification and melting curve analysis, and with restriction fragment length polymorphism (RFLP) analysis of the 5S-23S rDNA intergenic spacer. Infection with Borrelia burgdorferi sensu lato was found in 16.4% of the muscle samples. The most abundant genospecies was Borrelia afzelii (11.3%), followed by Borrelia burgdorferi sensu stricto (4.8%) and Borrelia garinii (0.7%). Borrelia infection was more frequently observed in Clethrionomys glareolus than in Apodemus spp. Sera were analyzed with an enzyme-linked immunosorbent assay (ELISA) test, yielding the total seropositivity rates of 24.5% for anti-Borrelia IgM antibodies and 25.5% for IgG antibodies. Total seroprevalence was higher in Apodemus spp. than in C. glareolus. In conclusion, our data indicate that in the Czech Republic small wild rodents can serve as hosts for B. burgdorferi s. s. as well as for B. afzelii.

Higher mRNA levels of chemokines and cytokines associated with macrophage activation in erythema migrans skin lesions in patients from the United States than in patients from Austria with Lyme borreliosis

BACKGROUND

Erythema migrans (EM) is caused primarily by Borrelia afzelii in Europe and solely by Borrelia burgdorferi in the United States. B. burgdorferi infection in the United States has previously been associated with faster expansion of EM lesions and with more associated symptoms, compared with B. afzelii infection in Europe. However, reasons for these differences are not yet known.

METHODS

We determined the Borrelia species infecting 67 US or Austrian patients with EM. The clinical pictures and chemokine and cytokine mRNA levels in lesional skin were then compared in the 19 B. burgdorferi-infected US patients and the 37 B. afzelii-infected Austrian patients, the 2 largest groups.

RESULTS

The 19 B. burgdorferi-infected US patients had faster-expanding EM lesions and a median of 4 associated signs and symptoms, whereas the 37 B. afzelii-infected Austrian patients had slower-expanding lesions and usually did not experience associated symptoms. Compared with the EM lesions of B. afzelii-infected Austrian patients, those of B. burgdorferi-infected US patients had significantly higher mRNA levels of chemokines associated with activation of macrophages, including chemoattractants for neutrophils (CXCL1), macrophages (CCL3 and CCL4), and T helper 1 cells (CXCL9, CXCL10, and CXCL11). In addition, compared with the EM lesions of Austrian patients, the EM lesions of US patients tended to have higher mRNA levels of the macrophage-associated proinflammatory cytokines interleukin 1beta and tumor necrosis factor alpha, and they had significantly higher mRNA expression of the antiinflammatory cytokines interleukin 10 and transforming growth factor beta.

CONCLUSIONS

The EM lesions of B. burgdorferi-infected US patients expanded faster, were associated with more symptoms, and had higher mRNA levels of macrophage-associated chemokines and cytokines than did the EM lesions of B. afzelii-infected Austrian patients.

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.

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.

A single-run, real-time PCR for detection and identification of Borrelia burgdorferi sensu lato species, based on the hbb gene sequence

Lyme borreliosis is the most important vector-borne disease caused by spirochetes within the Borrelia burgdorferi sensu lato (B. burgdorferi sl) complex. There is strong evidence that different species of this group of genetically diverse spirochetes are involved in distinct clinical manifestations of the disease. In order to differentiate species within this bacterial complex, we developed a real-time-PCR protocol, which targets the hbb gene. We designed a fluorescein-labeled probe specific of a region of this gene harboring a polymorphism linked to species. An internally Red640 labeled primer allowed a fluorescence resonance energy transfer to occur. The sensitivity of this method was in the range of 10 bacteria per assay. After amplification, a melting curve was generated for genotyping. Analysis of these melting curves clearly allowed the distinction between the main European species of B. burgdorferi sl. One hundred seventy tick extracts were analysed by this hbb-based method and in parallel by amplification of the 5S-23S intergenic spacer and RFLP analyses. There was a good correlation between these two methods. We conclude that this hbb-based real-time-PCR is suitable for epidemiological studies on field-collected ticks, although rare mutations in the genomic sequence spanned by the probe could lead to misidentification.

Comparison of SYTO9 and SYBR Green I for real-time polymerase chain reaction and investigation of the effect of dye concentration on amplification and DNA melting curve analysis

Following the initial report of the use of SYBR Green I for real-time polymerase chain reaction (PCR) in 1997, little attention has been given to the development of alternative intercalating dyes for this application. This is surprising considering the reported limitations of SYBR Green I, which include limited dye stability, dye-dependent PCR inhibition, and selective detection of amplicons during DNA melting curve analysis of multiplex PCRs. We have tested an alternative to SYBR Green I and report the first detailed evaluation of the intercalating dye SYTO9. Our findings demonstrate that SYTO9 produces highly reproducible DNA melting curves over a broader range of dye concentrations than does SYBR Green I, is far less inhibitory to PCR than SYBR Green I, and does not appear to selectively detect particular amplicons. The low inhibition and high melting curve reproducibility of SYTO9 means that it can be readily incorporated into a conventional PCR at a broad range of concentrations, allowing closed tube analysis by DNA melting curve analysis. These features simplify the use of intercalating dyes in real-time PCR and the improved reproducibility of DNA melting curve analysis will make SYTO9 useful in a diagnostic context.

Rapid detection and differentiation of Newcastle disease virus by real-time PCR with melting-curve analysis

In order to rapidly detect and differentiate Newcastle disease virus (NDV) isolates, a method based on real-time PCR SYBR Green I melting-curve analysis of the fusion (F) protein gene was developed. The detection limit of real-time PCR was 9 x 10(2) plasmid copies and was 100 times more sensitive than conventional PCR. Thirty eight reference NDV strains were rapidly identified by their distinctive melting temperatures (T(m)s): 89.23 +/- 0.27 degrees C for velogenic strains, 90.17 +/- 0.35 degrees C for pigeon mesogenic strains, 91.25 +/- 0.14 degrees C for two lentogenic strains (B1 and Ishii). No amplification was detected from unrelated RNA samples by this method. This real-time PCR directly detected NDV from infected tissues and eliminated the gel electrophoretic step for analyzing PCR product using ethidium bromide. The total time for a PCR run was less than 1 hour. The results obtained in this study showed that the real-time PCR presented here is a good screening test for the identification of NDV.

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.

Rapid detection of Wuchereria bancrofti in mosquitoes by LightCycler polymerase chain reaction and melting curve analysis

A LightCycler real-time polymerase chain reaction (PCR) assay was developed to detect Wuchereria bancrofti DNA in blood-fed mosquitoes. The assay is based on fluorescence melting curve analysis of the PCR product generated from a family of repeated DNA elements: the 182 bp SspI repeat, specific to the genus Wuchereria. According to the melting temperature, W. bancrofti infected-mosquitoes were differentiated from Brugia malayi-infected and non-infected mosquitoes as well as from genomic DNA of Dirofilaria immitis and human DNA. The method proved to be 100% sensitive in all W. bancrofti-infected mosquitoes. Melting curve analysis offers a rapid alternative for the specific detection of W. bancrofti in mosquitoes. It is very accurate and sensitive, allows a high throughput and can be performed on very small samples. The method therefore has great potential for application in epidemiological studies.

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.

Rapid differentiation of Old World Leishmania species by LightCycler polymerase chain reaction and melting curve analysis

A LightCycler real-time polymerase chain reaction (PCR) assay has been developed to detect and differentiate four of the main Leishmania species of the Old World. The assay is based on fluorescence melting curve analysis of PCR products generated from the minicircles of kinetoplast DNA. According to the melting temperature, which is a function of GC/AT ratio, length and nucleotide sequences of the amplified product, Leishmania major was differentiated from L. donovani and from L. tropica and L. infantum. Melting curves analysis offers a rapid alternative for identification of species in diagnostic or epidemiological studies of leishmaniasis or asymptomatic parasitism.

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).

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.

Recent advances in the diagnosis of Lyme disease

Diagnosis of human Lyme borreliosis is usually based on serology, which has a number of pitfalls. In the early phase of the disease serology can still be negative, whereas false-positive results are also common. The interpretation of confirmatory Western blot tests is not always easy. Furthermore, routine serology cannot discriminate between active and past infection. In addition, recombinant antigens are being introduced to improve serologic tests. New developments in the diagnosis of Lyme disease are the development of PCR tests. This review gives an overview of the molecular diagnostic possibilities of Lyme borreliosis, mainly by PCR, and describes some interesting possibilities for future serology.