Previous laboratory tests have Treponema pallidum inspection, syphilis test serum and cerebrospinal fluid examination. With the development of gene diagnosis technology, PCR technology applications of DNA testing Treponema pallidum, the syphilis diagnosis become accurate, rapid and sensitive.
First, Treponema pallidum inspection
(1) inspection methods
1. Dark-field microscopy: skin lesions, using slide organizations exudative fluid or lymph node puncture fluid, see that the activities of Treponema pallidum.
2. Immunofluorescent staining: green fluorescence microscopy showed the Treponema pallidum.
3. Biopsy examination Treponema pallidum, such as silver staining (Warthin - starry) Act, or (Levoaditis Act) or fluorescent antibody staining, available on the see Treponema pallidum, a dark brown, spiral structure, located in the surrounding dermal capillary. Silver stain positive results have to be interpreted cautiously because similar Treponema pallidum of other substances easily confused. While specific fluorescence tests were more reliable. (B) Identification of spirochetes
Endoscopic examination Treponema pallidum and Yaws, endemic syphilis, for his three non-venereal spiral of identification, and the tooth should also be of great spiral, helical gear of the small, soft spiral body, the spiral of genital phase identification.
1. Yaws, endemic syphilis, for his three non-STD spirochetes: morphology and Treponema pallidum not distinguish, but epidemiology, medical history, clinical manifestations can be identified;
2. Teeth of the spiral: reduced spirochetes than Treponema pallidum longer exists in the oral cavity, particularly the largest in Chifeng;
3. Tooth small spiral of: shorter than Treponema pallidum, Rotary also short distance, irregular movement at both the central slightly more width. Scale were seen mainly in the tooth; 4. Soft spirochetes: dredging of the spiral, spiral less, sports law and not fast, often changing its shape. The parasitic skin ulcers.
5. Genital spirochetes: short than Treponema pallidum, the spiral of big without rules, born in overcast dirt, not regular cleaning to a higher detection rate.
6. Other: spiral-shaped mesh fiber, fiber protein filaments, cilia, string-cell, and other objects of a spiral differential.
Second, syphilis serum test
According to different antigen used, syphilis serum test is divided into the following two categories:
(A) Non-Treponema pallidum serum antigen test motives for phospholipid antigen in the serum of anticardiolipin antibodies, also known as Su-reaction. This high sensitivity and specificity test lower, it can easily happen biological false positive. Patients with early syphilis fully after treatment, the reaction-can disappear without treatment early to late in the reaction of some patients may also be reduced or disappear. As the current general screening and quantitative tests, observation of relapse and re-infection. 1. Sexually transmitted diseases research laboratory test (Venereal Disease Research Laboratory test, VDRL); intentions phospholipid, lecithin, and cholesterol as antigen, can be used for quantitative and qualitative tests, reagents and control serum has been standardized, low-cost. This method commonly used, simple operation, preparing microscope to read the results, the deficiency is a syphilis sensitivity is not high.
2. Quick-reaction test plasma (Rapid Plasma reagin test, RPR): VDRL antigen improved sensitivity and specificity and VDRL similar advantage is the naked eye can read out the results.
3. No heating of glass test seropositive (Unheated Serum Reagin USR) is also VDRL antigen improved sensitivity and specificity and VDRL similar.
(B) Treponema pallidum serum antigen test: living or dead Treponema pallidum or their components to make spiral of antigen-antibody determination. This test sensitivity and specificity are high, generally used to confirm test. This test is to test anti-serum IgG antibody Treponema pallidum, even after adequate treatment of patients still exist for a long time, even lifelong not disappear, serum continued existence of positive reaction, therefore, can not be used to observe the effects.
1. Fluorescence Treponema pallidum antibody absorption test (FTA-ABS Test): This method is more sensitive and specific than the helical body experiments.
2. Treponema pallidum hemagglutination test (TPHA): sensitivity and specificity are high, easy to operate, but on a syphilis test as FTA-ABS sensitive.
3. Syphilis system dynamic test (Treponema Pallidum immobilization, TPI); spiral of strains with Nichol (live) plus serum (containing antibodies), in meeting with the participation of inhibited spiral of events. If ≥ 50% Treponema pallidum stop their activities, compared to positive. This test specificity and sensitivity are high, but high equipment requirements, operational difficulties, only research.
Third, gene diagnosis technology detection Treponema pallidum
Treponema pallidum not conducted in vitro. Clinical specimens of Treponema pallidum in the most sensitive and reliable test method is infected rabbits (RIT), live RIT can prove the existence of Treponema pallidum, the syphilis testing is commonly used standard methods. But with RIT on neonatal or adult conventional diagnosis of syphilis is not realistic. Syphilis serology diagnosis and treatment of infections identified significant, but not sensitive to the early diagnosis of syphilis, congenital syphilis and the diagnosis of nerve enough specificity. Serological tests for the diagnosis of congenital syphilis, the first problem is to be asymptomatic infected babies from the non-infected babies separately, these baby’s mother serum test positive syphilis, the difficulty lies in not humoral immune response to mothers with babies antibody response phase difference, because the mother’s IgG can be passed to the fetus. Also due to the existence of IgG life, it is difficult to evaluate the treatment results. Serological diagnosis often time, there is the false positive.
PCR Treponema pallidum DNA, highly specific, high sensitivity, is the diagnosis of syphilis in advanced methods.
(1) the design of PCR primers location and sequence:
At present, there are four sets of Treponema pallidum DNA amplification systems: Amplification 47 KDa membrane antigen gene (tpp47 gene), amplified 39 KDa alkaline membrane protein gene (bmp gene), amplified TpF1 protein gene (tpf-1) or TyF1 protein gene (tyf-1) and gene amplification tmpA.
Three amplification system primer sequence:
47-1 CACAATGCTCACTGAGGATAGT 648-669
47-2 ACGCACAGAACCGAATTCCTTG 1284-1035
Tpp47-3 TTGTGGTAGACACGGTGGGTAC 713-734
47-4 TGATCGCTGACAAGCTTAGGCT 1187-1208
TP3 CAGGTAACGGATGCTGAGT 256-275
TP4 CGTGGCAGTAACCGCAGTCT 762-741
BmpTP5 (probe) GACCTGAGGACTCTCAAATC 500-519
TP7 CTCAGCACTGCTGAGCGTAG 172-191
TP8 AACGCCTCCATCGTCACACC 788-769
F1 CTCTTCAAGGAGCTCAT 222-206
Tpf - 1F2 AGACAGTGGTTATGCTC 77-61
Or tyf - 1F3 (probe) ATTGCGCCAGCATGTAG 114-130
F4 (probe) ATTGCGCCGGCATGTAG 114-130
(B) the methods of operation
1. The collection of samples, according to the patient’s condition may take partial discharge, collected lymph node fluid, amniotic fluid, serum and cerebrospinal fluid. Distilled water with proper dilution, stored at 4 ° C refrigerator.
2. Sample handling: purpose is to expose the DNA Treponema pallidum, the elimination of specimens of PCR inhibitors. The following approach.
① boiling method: take 10 or 20 μ l serum or CSF Add 0.5 ml micro centrifuge tube, the water bath in boiling 10 minutes after cooling in the ice bath, 13000 g centrifugation 10 s, the supernatant for PCR analysis.
② low speed centrifugation: 100 μ l amniotic fluid, serum or cerebrospinal fluid into the 900 μ l sterile phosphate buffer, 10000 g centrifugation 10 min at room temperature, the supernatant was transferred to another microcentrifuge tube, 20000 g4 ℃ centrifugal 1 h, The supernatant was removed, suspended sediment 50 μ l sterile water, direct boiled for 10 min, ice bath cooling, supernatants from 40 μ l for PCR.
③ alkaline lysis method: take specimens 100 μ l collection in Canada with 1 mol / L NaCl, 1mol / L and 0.1% SDS NaOH solution in boiling 1.5 min, with 400 μ l (0.5 mol / L), Tris-HCl (pH 8.0) and . With the same volume of phenol extraction, then to 100 μ l 0.15mol / L NaCl phenol extraction. The entire 600 μ l solution with the same volume of chloroform: isoamyl alcohol (24:1) extraction, and then use the same volume of isopropanol precipitation (-20 ° C too fluid). 13000 g4 ℃ centrifugal 15 minutes, Along amylin suspended in 51 μ l sterile water, from 20 μ l as PCR template.
(C) PCR Amplification
1. Amplification 47 KDa membrane antigen gene: 100 ml of reaction of: 10 mmol / L TrisHCl (pH8.3), 50mmol / L KCl, 3mmol / L MgCl2, 100 μ g / ml gelatin, 0.5 μ g primer (47-1 and 47-2) , 75 mmol / LdNTPs, 2.5U TaqDNA polymerase. Preparation of various different from the DNA as template, the reaction process: 94 ° C 15 s, 60 ° C for 1 min, 72 ° C for 1 min, cycle 40, the end of the cycle to increase 72 ° C for 10 min extension of time, from 10 ml of reaction by 1% agarose gel Electrophoretic analysis. Dot blot analysis product: from 10 mlPCR amplified products by adding 10 ml0.5mol/LNaOH-1.5mol/NaCl solution degeneration 10 min, with 380 μ11.5 mol / L NaCl - 1mmol / L Tris (pH 7.2) and then use Minifold I point Films, 80 ° C vacuum processing film for 2 h with 496 bp probe 65 ° C hybridization overnight. Probe for primer 47-3 and 47-4 the PCR product with random primer labeling.
2. Amplification 39 KDa alkaline membrane protein gene: 25 μ1 reaction system including: 1 × RT buffer, 50 mmol / L Tris-HCl (pH 8.5), 50mmol/LNaCl, 4mmol/LMgCl2, 2mmol / L DTT (Kisumu sugar disulfide Alcohol), 200 μ mol / L dNTP, 100 µ mol / L primer (TP7 and TP8), 0.01% bovine serum albumin (no DNase and RNase), 1UTaqDNA polymerase, 5 μ1 sample, which may be included in 0.05 mmol / L 4-chloro enhance methylamine PCR.
PCR1: by using primers TP7 and TP8 amplified a 617 bp fragment, the reaction process: 94 ° C for 3 min and entered the cycle of: 94 ° C for 1 min, 65 ° C for 1 min, 72 ° C for 1 min, cycle number 30 or 35, each cycle of 72 ° C extension increased by 5 s, the last extension of time to 6 minutes.
PCR2: reuse nesting primer TP3 and TP4 amplified a 500 bp fragment, PCR1 product with distilled water diluted by 10 times, from 5 μ1 for the second time amplification. PCR2 of MgCl2 and primer concentrations of 5 mmol / L and 20 μ mol / L primer ( TP3 and TP4), and other conditions and PCR1 same.
PCR products were analyzed. ① from 10 μ1 reaction products by 2% agarose gel electrophoresis; ② Southern blot, using oligonucleotide probes TP5 (32P for end labeling) hybridization.
3. Amplification TpF1 protein gene TyF1 protein gene: 100 μ1 reaction containing: 50 mmol / L KCl, 10 mmol / L Tris-HCl (pH8.4), 2.5mmol / L MgCl2, 0.2mg/ml gelatin, 1 µ mol / L dNTP, 2mmol / L primer (F1 and F2), 2.5UTaqDNA polymerase, 10 μ1 treated rabbits testicular Treponema pallidum suspension, the reaction process: 94 ℃ 1min, 55 ℃ 1.5min, 72 ℃ 2.5min, cycle 40 times, from 10 μ1 PCR products used 2% agarose gel electrophoresis, Southern blotting, with tpf-1-specific probe F3 and tyf-1 special foreign body hybridization probes F4, respectively.
To achieve maximum efficiency amplification reaction parameters should choose the best value. Use the double-stranded DNA probe fragment detection of PCR products, rather than synthetic oligonucleotide probes, as this can be labeled high specific activity of radiation. In addition, the largest fragment probe can reduce wild strains tpp47 variable sequence and false negative results due to the Taq DNA polymerase base substitution errors led to the false negative results. Experiments confirmed: PCR can really achieve the sensitivity of detection tpp47 copy level.
Because clinical samples may contain a large amount of personnel cells and microorganisms, the establishment of Treponema pallidum highly specific PCR method is very important. Despite the large number of As noted in support of 47 Da membrane antigen gene and its corresponding gene with Treponema pallidum specificity, but also in-depth study of the specificity of the method. In EB stained agarose gel occasionally visible non-specific PCR products, (such as amplification gonorrhea Nyquist cocci), on the need for tpp47 specific probe hybridization to increase the specificity and sensitivity. Only Treponema pallidum subspecies of syphilis and Yaws subspecies of chromosomal DNA obtained specific PCR products, show that the pathogenic spirochetes very close relationship and 47 Da immune highly conserved protein antigenicity. Amplification tpp47 not as if the conventional method can distinguish between syphilis and of Borrelia burgdorferi, using serological tests in the diagnosis of Lyme disease and syphilis, there are two spiral cross-reaction.
Treponema pallidum subspecies of syphilis tpf-1 gene in 123 locations A, Yaws subspecies tpf-1 gene in 123 locations for G, Noordhoek with tpf-1 or tpf-1-specific oligonucleotide probe (two probes only one nucleotide different) testing different strains tpf-1 or tpf-1 gene amplification product. The results show that: it can not tpf-1 or tyf-1 gene 123 locations nucleotide difference between syphilis to the different subspecies. These strains isolated from patients with syphilis, some have spent several rabbits passage through the fresh clinical specimens Treponema pallidum DNA analysis and comparison, the above results may be due to Treponema pallidum in the passage by the mid-point mutation.
4, cerebrospinal fluid examination
For the diagnosis of syphilis nerve, including cell count, protein, VDRL test, PCR, colloidal gold test. Neural asymptomatic except for syphilis, all syphilis patients who period of more than one year should be for cerebrospinal fluid examination. Early Congenital Syphilis all babies should also check with the exception of cerebrospinal fluid of the central nervous system involvement may be. Cerebrospinal fluid cell count and the total protein amount of the increase in non-specific changes in neural CSF VDRL test is a more reliable diagnosis of syphilis basis. However, when the activities of the presence of syphilis, CSF white blood cell count often increased (WBC> 5/mm3), it also CSF white blood cell count is often a sensitive indicator of judgment. Conditional CSF PCR units will be fast and accurate diagnosis of syphilis nerve.
5, syphilis false positive serum reaction
Technical false positive: high sensitivity antigen, serum specimens made a mistake or hemolysis or bacterial contamination, the inspection room technology unskilled.
Biology false positive: spiral of non-antigen positive rate higher than the serum test spiral of serum antigen test. The former is to test the response of the patients, which is to test anti-Treponema pallidum antibody. The spiral of non-antigen test used also exist in other organizations, so other diseases have emerged even occasionally normal reaction of, in certain diseases occurred positive reaction against syphilis case called false positive.
1. Acute biological false positive: these diseases in the six months to overcast.
Seen measles, chickenpox, rubella, infectious mononucleosis disease, upper respiratory tract infections, scarlet fever, subacute bacterial endocarditis, pneumococcal pneumonia, active tuberculosis, filariasis, typhus, trypanosomiasis disease, relapsing fever, leptospirosis, malaria, but the low titer, in 1:8 following general, when using serum antigen spiral of FTA-ABS or TPHA test, serum negative reaction. PCR negative.
2. Chronic biological false positive, and sustainable for more than 6 months or a few years or even for life, can be divided into two categories:
(1) non-spiral of serum antigen test false positive; these diseases common in autoimmune diseases such as systemic lupus erythematosus, disseminated discoid lupus erythematosus, autoimmune hemolytic anemia, and systemic sclerosis, rheumatoid arthritis, rheumatic heart disease, cirrhosis, nodular more arteritis, Sjogren’s syndrome, chronic glomerulonephritis and heroin addiction, titer up to 1:64 ~ 1:128; minority pregnant women, the normal crowd false positive rate of 1% -2%. In over 70 years old in one percent false positive.
(2) antigen in serum spiral false positive rate than non-spiral of serum antigen test less, although some other disease patients FTA-ABS false positive, the staining was often weak or non-typical “beaded - like.”
(3) serum syphilis false negative reaction
1. A syphilis hard chancre:: General hard chancre: in 2-3 weeks, before a reaction of the body, so early response negative serum.
2. Immediate treatment of syphilis infection or advanced syphilis: Because of low serum response, a negative.
3. Secondary syphilis false negative; less than 1% of the patients with secondary syphilis not diluted its serum VDRL test were negative or weakly positive reaction, but in a highly diluted as positive, that is, before the band phenomenon (Prozone phenomenon), it is serum anticardiolipin antibodies in excess inhibit positive results.
4. Technical operations or antigen in serum low-sensitivity test negative.