Polymerase chain reaction amplification of culture supernatants for rapid detection of Borrelia burgdorferi

Plasticity in early immune evasion strategies of a bacterial pathogen

Borrelia burgdorferi is one of the few extracellular pathogens capable of establishing persistent infection in mammals. The mechanisms that sustain long-term survival of this bacterium are largely unknown. Here we report a unique innate immune evasion strategy of B. burgdorferi, orchestrated by a surface protein annotated as BBA57, through its modulation of multiple spirochete virulent determinants. BBA57 function is critical for early infection but largely redundant for later stages of spirochetal persistence, either in mammals or in ticks. The protein influences host IFN responses as well as suppresses multiple host microbicidal activities involving serum complement, neutrophils, and antimicrobial peptides. We also discovered a remarkable plasticity in BBA57-mediated spirochete immune evasion strategy because its loss, although resulting in near clearance of pathogens at the inoculum site, triggers nonheritable adaptive changes that exclude detectable nucleotide alterations in the genome but incorporate transcriptional reprograming events. Understanding the malleability in spirochetal immune evasion mechanisms that ensures their host persistence is critical for the development of novel therapeutic and preventive approaches to combat long-term infections like Lyme borreliosis.

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.

Enhanced detection of host response antibodies to Borrelia burgdorferi using immuno-PCR

Lyme disease is the fastest-growing zoonotic disease in North America. Current methods for detection of Borrelia burgdorferi infection are challenged by analysis subjectivity and standardization of antigen source. In the present study, we developed an immuno-PCR (iPCR)-based approach employing recombinant in vivo-expressed B. burgdorferi antigens for objective detection of a host immune response to B. burgdorferi infection. iPCR is a liquid-phase protein detection method that combines the sensitivity of PCR with the specificity and versatility of immunoassay-based protocols. Use of magnetic beads coated with intact spirochetes provided effective antigen presentation and allowed detection of host-generated antibodies in experimentally infected mice at day 11 postinoculation, whereas host-generated antibodies were detected at day 14 by enzyme-linked immunosorbent assay (ELISA) and day 21 by immunoblotting. Furthermore, magnetic beads coated with recombinant B. burgdorferi in vivo-expressed antigen OspC or BmpA demonstrated positive detection of host-generated antibodies in mice at day 7 postinoculation with markedly increased iPCR signals above the background, with the quantification cycle (C(q)) value for each sample minus the mean background C(q) plus 3 standard deviations (ΔC(q)) being 4 to 10, whereas ΔC(q) was 2.5 for intact spirochete-coated beads. iPCR demonstrated a strong correlation (Spearman rank correlation = 0.895, P < 0.0001) with a commercial ELISA for detection of host antibodies in human Lyme disease patient sera using the B. burgdorferi VlsE C6 peptide. In addition, iPCR showed potential applicability for direct detection of spirochetes in blood. The results presented here indicate that our iPCR assay has the potential to provide an objective format that can be used for sensitive detection of multiple host response antibodies and isotypes to B. burgdorferi infection.

Comparison of five diagnostic modalities for direct detection of Borrelia burgdorferi in patients with early Lyme disease

Lyme disease, the most commonly reported tick-borne infection in North America, is caused by infection with the spirochete Borrelia burgdorferi. Although an accurate clinical diagnosis can often be made based on the presence of erythema migrans, in research studies microbiologic or molecular microbiologic confirmation of the diagnosis may be required. In this study, we evaluated the sensitivity of 5 direct diagnostic methods (culture and nested polymerase chain reaction [PCR] of a 2-mm skin biopsy specimen, nested PCR and quantitative PCR (qPCR) performed on the same 1-mL aliquot of plasma and a novel qPCR-blood culture method) in 66 untreated adult patients with erythema migrans. Results of one or more of these tests were positive in 93.9% of the patients. Culture was more sensitive than PCR for both skin and blood, but the difference was only statistically significant for blood samples (P<0.005). Blood culture was significantly more likely to be positive in patients with multiple erythema migrans skin lesions compared to those with a single lesion (P=0.001). Positive test results among the 48 patients for whom all 5 assays were performed invariably included either a positive blood or a skin culture. The results of this study demonstrate that direct detection methods such as PCR and culture are highly sensitive in untreated adult patients with erythema migrans. This enabled microbiologic or molecular microbiologic confirmation of the diagnosis of B. burgdorferi infection in all but 4 (6.1%) of the 66 patients evaluated.

Improving the yield of blood cultures from patients with early Lyme disease

Approximately 45% of untreated United States patients with early Lyme disease associated with erythema migrans have a positive blood culture based on microscopic detection of Borrelia burgdorferi in Barbour-Stoenner-Kelly medium after 2 to 12 weeks of incubation. In this study we demonstrate that the yield of blood cultures can be significantly increased to 70.8% by the use of a combined culture-quantitative PCR technique and that among those patients found to have a positive blood culture, positivity was detected in over 90% within just 7 days of incubation. Patients with multiple erythema migrans were almost uniformly culture positive by this technique.

Molecular diagnosis of Borrelia bacteria for the diagnosis of Lyme disease

INTRODUCTION

Lyme borreliosis is the most common vector-borne disease in the temperate climate zone of Europe and the US, and its frequency is increasing. Serology is often negative in the early stage of Lyme borreliosis and cannot distinguish between active and past infection. Culture is cumbersome and not very sensitive, and polymerase chain reaction (PCR) for the diagnosis of Lyme borreliosis has been described over the last 20 years, with varying results.

AREAS COVERED

In this article, all of the major studies in which PCR has been used to diagnose Lyme borreliosis in humans are critically reviewed. However, this article does not include studies that consisted of fewer than 10 patients, nor does it include studies that have inadequate descriptions of the patient population.

EXPERT OPINION

There is a lack of standardized protocols, and preamplification procedures have not been standardized. Nested PCRs seem to perform best, but are prone to contamination. PCR on skin biopsies can be used to diagnose early Lyme borreliosis in patients with atypical forms of erythema migrans. PCR also has diagnostic potential in Lyme arthritis and early neuroborreliosis. Blood and urine should not used for PCR. For future development, preamplification procedures should be optimized using materials from experimentally infected animals. Multi-center studies should follow to evaluate these optimized tests.

[Role of biological assays in the diagnosis of Lyme borreliosis presentations. What are the techniques and which are currently available?]

The biological diagnosis of Borrelia burgdorferi sensu lato infection is usually made by antibody detection in patient sera. Thus, serological testing (Elisa, immunoblotting) is essential for a biological diagnosis. Specific antibody detection is usually done in serum and CSF of patients suspected of Lyme borreliosis. Laboratories must follow European recommendations to validate these assays in routine practice. Antibody detection lacks sensitivity in the early cutaneous phase of the infection. Therefore, serological testing is not recommended for the diagnosis of erythema migrans. The interpretation of serology must take into account the variability of Elisa sensitivity and specificity and the lack of standardization for Western-blotting in Europe. Besides these indirect diagnosis techniques, there is also direct detection of spirochetes by culture or by in vitro DNA amplification but these require adequate samples. These molecular tests must not be performed routinely, but only for specific clinical situations and in specialized laboratories only.

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.

Laboratory testing for suspected Lyme disease

Laboratory testing for B. burgdorferi infection is intended to substantiate a physician's clinical judgment of whether a patient has Lyme disease or not. Cultivation of B. burgdorferi from a patient's skin or blood is the gold standard for demonstration of active infection, but it is expensive and lacks clinical sensitivity. Detection of spirochetal DNA in clinical samples by PCR has better sensitivity, but PCR for B. burgdorferi has not yet been standardized for more routine diagnostic testing. Detection of antibodies to B. burgdorferi is the most practical and common approach for laboratory work-up of a case of suspected Lyme disease. Serologic assays fall short of 100% sensitivity and specificity, however, and examination of a single specimen in time does not discriminate between previous and ongoing infection. Because of a background false positivity even among healthy populations of nonendemic regions, serologic testing is recommended only when there is at least a one in five chance, in the physician's estimation, that the patient has active Lyme disease. The pretest likelihood of the disease is determined by the physician in the context of epidemiologic and clinical facts of the case. This estimate can serve to reassure patients who are at low risk of B. burgdorferi infection but are seeking a Lyme test for complaints of a more nonspecific nature. Although new subunit serologic assays based on recombinant proteins are becoming available commercially, the longstanding two-test approach, in which a positive or indeterminate result with a standardized, sensitive ELISA test is followed by verification with a more specific Western blot assay, still provides the physician with a reasonably accurate and reliable assessment of the presence of antibodies to B. burgdorferi. More recent challenges for serologic testing are seropositivity in the population as the result of immunization with the Lyme disease vaccine and the emergence of new Borrelia species that cause Lyme disease-like illnesses.

Distribution of Borrelia burgdorferi sensu lato in Ixodes ricinus (Acari: Ixodidae) ticks from the Basque Country, Spain

Borrelia burgdorferi was found widespread in ixodid ticks from the Basque Country (Spain) during a two-step study. In the first part, a total of 7,835 ixodids of eight different species was collected from vegetation, classified, and processed using polymerase chain reaction (PCR) for detection of B. burgdorferi ospA DNA. B. burgdorferi DNA wasdetectedin < or = 12.5% of adults and > or = 0.6% of Ixodes ricinus (L., 1758) nymphs (mean 1.5 and 0.05%, respectively), and in < or = 14.3% of adult Hemaphysalis punctata (Canestrini & Fanzago, 1877) analyzed (mean 1.2%). The second part of the study was undertaken 2 yr later to characterize B. burgdorferi distribution by focusing on the areas where L. ricinus was the predominant species. Ten areas were selected from which 1,535 nymphs and adults of I. ricinus were collected and processed by PCR and culture techniques. Infected ticks were found in all zones. B. burgdorferi DNA was detected in a mean of 9.3 and 1.5% of adults and nymphs, respectively. Nine isolates of B. burgdorferi were obtained, belonging to four different genospecies (B. burgdorferi sensu stricto, B. garinii, B. valaisiana, and B. lusitaniae). The results indicate that some areas of Spain have a potential risk for Lyme disease agent exposure and that B. borgdorferi appears to have an increasing occurrence in ticks in the Basque Country.

An indirect hemagglutination antibody test to detect antibodies to Borrelia burgdorferi in patients with Lyme disease

An indirect hemagglutination antibody (IHA) test was evaluated for its ability to detect borrelial antibodies in serum samples from patients with Lyme disease. The key test reagent developed for this antibody detection system was tannic acid-treated and glutaraldehyde-fixed sheep red blood cells (SRBC) containing Borrelia burgdorferi (Bb) antigens attached to the outer surface of the SRBC. In order to establish suitable cut-off titers, initial specificity and sensitivity measurements were made using sera from 100 anonymous healthy volunteers and 30 additional pre-determined samples known to be non-reactive or reactive for Lyme disease or syphilis. These results were compared with those obtained using a commercially available ELISA. At titers >/=64, the IHA test had a combined 98% specificity and 100% sensitivity for these 130 serum samples, 30 of which were known positives or negatives, whereas the ELISA was less specific (93%) and much less sensitive (80%). Subsequent testing was performed on sera from 65 patients with the erythema migrans (EM) rash and 20 patients with early disseminated (cardiac/neurologic) symptoms or with Lyme arthritis. At initial presentation, 46-48% of the EM patients had IHA reactivity, with titers >/=128, while 42% were positive in the ELISA. Follow-up testing performed on these EM patients, 8-12 days after receiving antibiotic treatment, revealed that Bb antibodies were detected best by the IHA test (83-86% reactive) relative to the ELISA (81% reactive). Bb antibodies were readily detectable on all of the serum samples from the early disseminated and late stage Lyme disease cases in both assay systems. Based on these results and because of its technical and interpretive simplicity, the IHA test should be considered as a useful and convenient alternative for the serological analysis of Bb infections.

Diagnostic value of PCR for detection of Borrelia burgdorferi in skin biopsy and urine samples from patients with skin borreliosis

Skin biopsies of 36 patients with erythema migrans and acrodermatitis chronica atrophicans (ACA) before therapy and those of 8 patients after therapy were examined for Borrelia burgdorferi DNA by PCR. Skin biopsies of 27 patients with dermatological diseases other than Lyme borreliosis and those of 10 healthy persons were examined as controls. Two different primer sets targeting 23S rRNA (PCR I) and 66-kDa protein (PCR II) genes were used. PCR was performed with freshly frozen tissue (FFT) and paraffin-embedded tissue (PET). For FFT specimens of erythema migrans, 73% were positive by PCR I, 79% were positive by PCR II, and 88% were positive by combining PCR I and II. For PET specimens, PCR was less sensitive (PCR I, 44%; PCR II, 52%). For FFT specimens of ACA, PCR I was positive for two of five patients and PCR II was positive for four of five patients. B. burgdorferi was cultured from 79% of the erythema migrans specimens but not from any of the ACA lesions. Elevated B. burgdorferi antibodies were detected in sera of 74% of erythema migrans patients and 100% of ACA patients. All urine samples were negative by PCR II, whereas PCR I was positive for 27%. However, hybridization of these amplicons was negative. Sequencing of three amplicons identified nonborrelial DNA. In conclusion, urine PCR is not suitable for the diagnosis of skin borreliosis. A combination of two different primer sets achieves high sensitivity with skin biopsies. In early erythema migrans infection, culture and PCR are more sensitive than serology.

PCR in laboratory diagnosis of human Borrelia burgdorferi infections

The laboratory diagnosis of Lyme borreliosis, the most prevalent vector-borne disease in the United States and endemic in parts of Europe and Asia, is currently based on serology with known limitations. Direct demonstration of Borrelia burgdorferi by culture may require weeks, while enzyme-linked immunosorbent assays for antigen detection often lack sensitivity. The development of the PCR has offered a new dimension in the diagnosis. Capable of amplifying minute amounts of DNA into billions of copies in just a few hours, PCR facilitates the sensitive and specific detection of DNA or RNA of pathogenic organisms. This review is restricted to applications of PCR methods in the diagnosis of human B. burgdorferi infections. In the first section, methodological aspects, e.g., sample preparation, target selection, primers and PCR methods, and detection and control of inhibition and contamination, are highlighted. In the second part, emphasis is placed on diagnostic aspects, where PCR results in patients with dermatological, neurological, joint, and ocular manifestations of the disease are discussed. Here, special attention is given to monitoring treatment efficacy by PCR tests. Last, specific guidelines on how to interpret PCR results, together with the advantages and limitations of these new techniques, are presented.

Detection of Borrelia burgdorferi sensu lato in lesional skin of patients with erythema migrans and acrodermatitis chronica atrophicans by ospA-specific PCR

The aim of this study was to develop a sensitive and specific PCR for the detection of Borrelia burgdorferi DNA. The plasmid-located gene coding for the outer surface protein A (OspA [31-kDa protein]) was used as a target. Nucleotide sequence information from different B. burgdorferi ospA genotypes was used to design primers homologous to different genotypes. The sensitivity of the nested PCR differed from 1 fg to 1 pg of borrelial DNA, depending on the strain analyzed. No cross-reactions with DNA from spirochetes other than B. burgdorferi or with human DNA were observed. A total of 22 skin biopsy samples from patients with erythema migrans (EM [n = 10]) or acrodermatitis chronica atrophicans (ACA [n = 12]) were examined for the presence of B. burgdorferi by nested PCR. Of 22 biopsies, 80% from EM patients and 92% from ACA patients were positive by PCR amplification. By comparison, 50% of the EM patients had elevated B. burgdorferi-specific immunoglobulin M (IgM) and/or IgG antibody levels as tested by enzyme-linked immunosorbent assay (ELISA) using purified B. burgdorferi flagella as antigen. A total of 33% of ACA patients had elevated IgM titers, and all had high IgG titers in their sera. Only 30% of specimens from patients with EM and none from patients with ACA were positive by culture. All culture-positive specimens were also positive by PCR. Thus, the sensitivities of the PCR were 80 and 92%, respectively, for patients with EM and ACA on the basis of the clinical and histopathological diagnoses of Lyme disease. From these results, we conclude that PCR is a suitable method to detect B. burdorferi sensu lato DNA in skin biopsy samples and could be applied as an additional diagnostic tool.