The relative frequency of Mycobacterium tuberculosis and Mycobacterium avium infections in HIV positive patients, Ahvaz, Iran

ObjectiveTo estimate the prevalence of Mycobacterium tuberculosis (M. tuberculosis) and Mycobacterium avium (M. avium) infections in HIV-positive patients suspected to have pulmonary and extrapulmonary mycobacterial co-infection using PCR technique.MethodsTotally 50 samples comprising sputum, pleural fluid and CSF taken from HIV positive patients suspected to have mycobacterial infection, were processed. The demographic information and results of acid fast staining and culture were recorded for each patient. The PCR for detecting of M. tuberculosis comprised of specific primers targeting IS6110 gene sequence. For detecting of M. avium, PCR with primers that amplifies the mig gene were used.ResultsFrom 50 samples processed, 45 were sputum (90%), 3 pleural fluid (6%) and 2 CSF (4%). In total, 8 (16%) were culture positive, 7 had positive acid fast staining (14 %) and 13 samples (26%) were positive using PCR technique. All the positive samples were sputum and belonged to patients with pulmonary infection. Of these, 9 were positive for M. tuberculosis (69.2%) and 4 were identified as M. avium (30.8%), which 2 out of 13 positive samples showed mixed infections by both mycobacteria.ConclusionsThe PCR shows the highest detection rate (26%) of mycobacteria compared with culture and acid fast staining. The majority of infections were with M. tuberculosis (18%) and this shows the importance of this mycobacterial co-infection in HIV positive patients in the region of study.     

A case of tuberculosis verrucosa cutis in Brazil undiagnosed for 15 years

Tuberculosis verrucosa cutis is a rare medical condition that is caused by the inoculation of Mycobacterium tuberculosis into the skin of a previously sensitized individual. This clinical form of tuberculosis corresponds to 1–2% of all cases of tuberculosis and due to the paucibacillary characteristic of the lesions, patients can be misdiagnosed, accounting for the chronification of the skin infection. Herein, we report the case of a 26-year-old male farmer, presenting plaques with verrucosa and hyperkeratosis features in the left thigh and buttocks during 15 years. M. tuberculosis was identified by PCR and the patient was treated with standard anti-tuberculosis drugs, with subsequent improvement of the skin lesions.     

Interpretation of mycobacterial antibodies in the cerebrospinal fluid of adults with tuberculous meningitis

Objective Microbiological identification of Mycobacterium tuberculosis is insensitive and slow, and clinical distinction of tuberculous meningitis (TBM) from other subacute or chronic meningoenchephalitides (SACM) is difficult. Successful use of highly specific M. tuberculosis serological assays on cerebrospinal fluid has been reported, but their performance for diagnosis in a tuberculosis endemic country where they would be of most value is unclear. We sought to determine the biological basis for the uncertainty in interpretation of antibody detection in the CSF of TBM patients. Methods We identified prospectively 46 adults with SACM and explored the concordance between TBM diagnosis and detection of highly specific M. tuberculosis antibodies in CSF. The source of antibodies in CSF was explored by evaluating the correlation between antibody titres in CSF with those in serum, or with the albumin quotient. Intrathecal IgG synthesis was assessed by the IgG index. Results Positive antibody titres were more frequent among TBM patients (76%), but were also present in individuals with other SACM (59%). A positive correlation between antibody titres in CSF with those in serum, or with the albumin quotient, supported the leakage of antibodies from plasma to CSF through an increased blood–brain barrier permeability. Intrathecal IgG synthesis was only detected in 35% of the TBM cases. Conclusion Plasma antibodies likely synthesized in response to previous tuberculosis infections were a major source of mycobacterial antibodies in CSF due to leakage through an impaired blood–brain barrier. Interpretation of mycobacterial antibodies in CSF of adults for TBM, however specific, must take into account the contribution of antibodies from plasma, and hence, has questionable use for diagnosis.     

Diagnosis of intestinal tuberculosis using a monoclonal antibody to Mycobacterium tuberculosis

AIM: To investigate the utility of immunohistochemical (IHC) staining with an antibody to Mycobacterium tuberculosis (M. tuberculosis) for the diagnosis of intestinal tuberculosis (TB).METHODS: We retrospectively identified 10 patients (4 males and 6 females; mean age = 65.1 ± 13.6 years) with intestinal TB. Clinical characteristics, including age, gender, underlying disease, and symptoms were obtained. Chest radiograph and laboratory tests, including sputum Ziehl-Neelsen (ZN) staining, M. tuberculosis culture, and sputum polymerase chain reaction (PCR) for tubercle bacilli DNA, as well as Tuberculin skin test (TST) and QuantiFERON-TB gold test (QFT), were examined. Colonoscopic records recorded on the basis of Sato’s classification were also reviewed, in addition to data from intestinal biopsies examined for histopathological findings, including hematoxylin and eosin staining, and ZN staining, as well as M. tuberculosis culture, and PCR for tubercle bacilli DNA. For the present study, archived formalin-fixed paraffin-embedded (FFPE) intestinal tissue samples were immunohistochemically stained using a commercially available species-specific monoclonal antibody to the 38-kDa antigen of the M. tuberculosis complex. These sections were also stained with the pan-macrophage marker CD68 antibody.RESULTS: From the clinical data, we found that no patients were immunocompromised, and that the main symptoms were diarrhea and weight loss. Three patients displayed active pulmonary TB, six patients (60%) had a positive TST, and 4 patients (40%) had a positive QFT. Colonoscopic findings revealed that all patients had type 1 findings (linear ulcers in a circumferential arrangement or linear ulcers arranged circumferentially with mucosa showing multiple nodules), all of which were located in the right hemicolon and/or terminal ileum. Seven patients (70%) had concomitant healed lesions in the ileocecal area. No acid-fast bacilli were detected with ZN staining of the intestinal tissue samples, and both M. tuberculosis culture and PCR for tubercle bacilli DNA were negative in all samples. The histopathological data revealed that tuberculous granulomas were present in 4 cases (40%). IHC staining in archived FFPE samples with anti-M. tuberculosis monoclonal antibody revealed positive findings in 4 patients (40%); the same patients in which granulomas were detected by hematoxylin and eosin staining. M. tuberculosis antigens were found to be mostly intracellular, granular in pattern, and primarily located in the CD68⁺ macrophages of the granulomas.CONCLUSION: IHC staining with a monoclonal antibody to M. tuberculosis may be an efficient and simple diagnostic tool in addition to classic examination methods for the diagnosis of intestinal TB.     

Comparison of conventional diagnostic methods with molecular method for the diagnosis of pulmonary tuberculosis

BackgroundTuberculosis remains one of the deadliest communicable diseases. Prompt diagnosis of active tuberculosis cases facilitates timely therapeutic intervention and minimizes the community transmission. Although conventional microscopy has low sensitivity, still it remains the corner stone for the diagnosis of pulmonary tuberculosis in high burden countries like India. On the other hand, Nucleic acid amplification techniques due to their rapidity and sensitivity, not only help in early diagnosis and management of tuberculosis but also curtail the transmission of the disease. This study therefore was aimed at assessing the diagnostic performance of Microscopy by Ziehl Neelsen (ZN) and Auramine Staining (AO) with Gene Xpert/CBNAAT (Cartridge based nucleic acid amplification test) in the diagnosis of Pulmonary Tuberculosis.MethodsA prospective comparative study was done on the sputum samples of 1583 adult patients from November 2018 to May 2020 suspected of having pulmonary tuberculosis as per NTEP criteria visiting the Designated Microscopic Centre of SGT Medical College, Budhera, Gurugram. Each sample was subjected to ZN staining, AO staining, and was run on CBNAAT as per National Tuberculosis Elimination Program (NTEP) guidelines. The sensitivity, specificity, PPV and NPV and Area under the curve of ZN microscopy and Fluorescent Microscopy were calculated taking CBNAAT as reference in absence of culture.ResultsOut of the 1583 samples studied, 145 (9.15%) and 197 (12.44%) were positive by ZN and AO staining methods respectively. By CBNAAT 246 (15.54%) samples were positive for M. tuberculosis. AO was also able to detect more pauci-bacillary cases than ZN. While CBNAAT detected M. tuberculosis in 49 sputum samples which were missed by both methods of microscopy. On the other hand there were 9 samples which were positive for AFB by both the smear microscopy techniques but M. tuberculosis was not detected by CBNAAT, these were considered as Non-Tuberculous Mycobacteria. Seventeen samples were resistant to rifampicin.ConclusionAuramine Staining technique is more sensitive and less time consuming for the diagnosis of pulmonary tuberculosis as compared to the conventional ZN Staining. CBNAAT can be a useful tool for early diagnosis of patients with high clinical suspicion of pulmonary tuberculosis and detecting rifampicin resistance.     

Drug susceptibility in Mycobacterium tuberculosis of a sample of patients in Guinea Bissau

Sputum samples from patients with known or suspected tuberculosis were collected in Bissau, Guinea Bissau, and isolates belonging to the Mycobacterium tuberculosis complex (M. tuberculosis, M. bovis or M. africanum) were examined for their susceptibility to the 4 drugs streptomycin, isoniazid, ethambutol and rifampicin. Of 59 M. tuberculosis complex isolates only 2 were resistant to any of the drugs (isoniazid). Thus there is little resistance to these first line drugs among M. tuberculosis isolates from patients in Guinea Bissau.     

Correlation between culture of Mycobacterium tuberculosis and IgG antibody to Mycobacterium tuberculosis antigen-5 in the cerebrospinal fluid of patients with tuberculous meningitis

A retrospective study was made of the correlation between culture of Mycobacterium tuberculosis and detection of IgG antibody to M. tuberculosis antigen-5 in cerebrospinal fluid (CSF) by means of an enzyme linked immunosorbent assay (ELISA). Mycobacterium tuberculosis was cultured from the CSF in 14 of 70 patients with a clinical diagnosis of tuberculous meningitis (TBM). IgG antibody to M. tuberculosis antigen-5 was demonstrated in significant titres (80–640) in all 14 culture-positive patients. Thus, positive correlation was observed between culture of M. tuberculosis and detection of IgG antibody in the CSF. As a result of this observation, the CSF from 56 culture-negative patients with a clinical diagnosis TBM was specifically investigated for the detection of IgG antibody to M. tuberculosis antigen-5 and the findings were correlated with those of culture-positive patients. The assay was positive in 34 of 56 patients, the antibody titre ranging between 80 and 640. In the CSF of 70 patients with non-tuberculous neurological diseases, the assay was negative at a dilution of 1 in 80. Thus, detection of IgG antibody to M. tuberculosis antigen-5 by indirect ELISA carried 100% specificity and 60·7 % sensitivity for a tuberculous aetiology in culture-negative patients with TBM. The results of this study suggest that indirect ELISA for IgG antibody to M. tuberculosis antigen-5 in CSF holds definite promise in diagnosis of TBM, particularly when repeated cultures of CSF are negative for M. tuberculosis.     

系统性红斑狼疮合并脑结核十例临床分析

目的 对系统性红斑狼疮(SLE)合并脑结核患者的临床资料进行回顾性分析,以期指导临床早期诊断和治疗.方法 回顾分析1995年1月至2010年10月北京协和医院住院治疗的SLE合并脑结核患者10例临床资料.结果 10例患者SLE病程0.6～30年,中位时间i.5年.发病时8例患者的狼疮病情稳定.所有患者均曾应用相当于1 mg·kg1·d-1的泼尼松治疗,其中3例患者曾接受甲泼尼龙冲击治疗,9例患者曾应用免疫抑制剂治疗.SLE合并脑结核患者,脑结核感染相关症状以发热、头痛最常见8例,其次是恶心呕吐6例、神经系统定位体征6例,合并其他部位结核感染9例.脑脊液检查示脑脊液压力增高[ (247±66) cm H2O],脑脊液蛋白正常或增高[(1.4±0.7)g/L].8例完善头颅增强磁共振成像(MRI)的患者均可见典型环形强化或结节样强化.经积极抗结核治疗,7例患者好转或稳定,1例死亡,2例失访.结论 对于病情稳定的SLE患者出现不明原因的发热、头痛及神经系统定位体征时,需警惕颅内感染尤其是脑结核的可能.胸部X线片及头颅MRI有助于诊断.此类患者病情凶险,但及时给予足量足疗程针对性治疗,预后较好.     

Case Report: Disseminated Mycobacterium tuberculosis Infection in a Dog

An uncommon disseminated Mycobacterium tuberculosis infection is described in a 12-year-old female dog presenting with fever, dyspnea, cough, weight loss, lymphadenopathy, melena, epistaxis, and emesis. The dog had a history of close contact with its owner, who died of pulmonary tuberculosis. Radiographic examination revealed diffuse radio-opaque images in both lung lobes, diffuse visible masses in abdominal organs, and hilar and mesenteric lymphadenopathy. Bronchial washing samples and feces were negative for acid-fast organisms. Polymerase chain reaction (PCR)-based species identification of bronchial washing samples, feces, and urine revealed M. tuberculosis using PCR-restriction enzyme pattern analysis-PRA. Because of public health concerns, which were worsened by the physical condition of the dog, euthanasia of the animal was recommended. Rough and tough colonies suggestive of M. tuberculosis were observed after microbiological culture of lung, liver, spleen, heart, and lymph node fragments in Löwenstein-Jensen and Stonebrink media. The PRA analysis enabled diagnosis of M. tuberculosis strains isolated from organs.     

BKV-DNA and JCV-DNA in CSF of Patients with Suspected Meningitis or Encephalitis

Abstract. Background: Few studies have looked for the polyoma viruses JC or BK virus in the central nervous system (CNS) of patients without neurological symptoms or with neurological symptoms other than progressive multifocal leukoencephalopathy (PML). PCR-microplate hybridization method was employed for the detection of BKV-DNA or JCV-DNA in cerebrospinal fluid (CSF) specimens from patients with suspected meningitis or encephalitis. Materials and Methods: A total of 181 CSF specimens from 151 patients with suspected meningitis or encephalitis was examined for BKV or JCV using PCR-microplate hybridization method. None of the patients had (clinically diagnosed) PML. A control group consisting of 20 CSF specimens from normal subject was also included. Results: BKV DNA was found in five out of 131 (3.8%) and JCV DNA in two out of 131 (1.5%) of the patients with suspected meningitis or encephalitis by PCR ELISA. BKV or JCV DNA was not detected in CSF samples of any of 19 HIVpositive patients. BKV and JCV DNAs were detected respectively in two CSF samples in which Mycobacterium tuberculosis (TB) PCR was also positive. Another patient who was positive for JCV PCR died with a diagnosis of cerebral lymphoma. Among the BK virus infected patients there was a patient with a previous history of hemolytic uremia and acute renal failure. Neither BKV nor JCV DNA was found in any of the 20 CSF samples from normal patients undergoing lumbar puncture for myelography as a part of an investigation of lower back pain. Conclusion: These results suggest that BK virus may be associated with neurological diseases either in immunocompetent or immunocompromised patients. Detection of BKV and JCV DNA in the CSF of the patients suspected to have either meningitis or encephalitis suggests that these viruses may have an etiological role. Thus, diagnostic tests for BK and JC viruses should be included in the investigative program for meningitis or encephalitis patients.     

Misdiagnosis of tuberculosis and the clinical relevance of non—tuberculous mycobacteria in Zambia

ObjectiveTo determine the accuracy of TB diagnosis of TB in Zambia in the era of increasing HIV prevalence.MethodsSputum of the clinically diagnosed TB cases was additionally subjected to liquid culture and molecular identification. This study distinguished between TB cases confirmed by positive Mycobacterium tuberculosis (M. tuberculosis) cultures and mycobacterial disease caused by non-tuberculous mycobacteria (NTM).ResultsOnly 49% of the 173 presumptively diagnosed TB cases was M. tuberculosis cultured, while in 13% (22) cases, a combination of M. tuberculosis and NTM was found. In 18% of the patients only NTM were cultured. In 28%, no mycobacteria was cultivable. HIV positive status was correlated with the isolation of NTM (P <0.05).ConclusionsThe diagnosis of tuberculosis based on symptoms, sputum smear and/or chest X-ray leads to significant numbers of false-positive TB cases in Zambia, most likely due to the increased prevalence of HIV. The role of NTM in tuberculosis-like disease also seems relevant to the false diagnosis of TB in Zambia.     

Infectiousness of patients with smear-negative pulmonary tuberculosis,assessed by Real-time Polymerase Chain Reaction,XpertⓇMTB/RIF

Currently, pulmonary tuberculosis (TB) isolation recommendations are based on serial sputum smear microscopy. To assess infectiousness of smear-negative/GeneXpert-positive (Sm-/GXpert+) pulmonary TB, we evaluated 511 contacts of pulmonary TB patients attended at a teaching hospital in Spain (2010–2018). There were no statistically significant differences in rates of Mycobacterium tuberculosis infection (46.2% contacts of smear-positive and 34.6% contacts of Sm-/GXpert+ pulmonary TB patients, p = 0.112). Sm-/GXpert+ pulmonary TB poses a substantial risk of transmission of M. tuberculosis infection. Our results add evidence to support including Real-time Polymerase Chain Reaction (Xpert^ⓇMTB/RIF) in the work-up diagnosis of suspected pulmonary TB cases to make decisions on air-borne isolation.     

Direct detection of Mycobacterium tuberculosis in sputum samples from Guinea Bissau by an rRNA target-amplified test system

Setting: There is a need for more sensitive and rapid methods for laboratory confirmation in the diagnosis of tuberculosis.Objective: To investigate the applicability of a target rRNA amplified test system (AMTDT, Gen-Probe, CA) for rapid detection of Mycobacterium tuberculosis.Design: The rRNA amplified test system was compared to standard methods for acid fast microscopy and mycobacterial culture for the demonstration of M. tuberculosis in sputum samples from 247 patients in Guinea Bissau with suspected tuberculosis.Results: The highest incidence of positive samples was obtained with the AMTDT test. Out of 274 sputum samples 96 (35%) were positive by the AMTDT test, 82 (30%) were positive by culture and 38 (14%) by direct microscopy. Using culture as reference method the sensitivity of the test was 85% (after discrepancy analysis 87%), and the specificity was 86% (after discrepancy analysis 93%).Conclusion: The sensitivity and specificity of the AMTDT test used in this setting indicates that it may be a valuable complement for improving the laboratory diagnosis of tuberculosis.     

The detection of Mycobacterium tuberculosis in bone marrow aspirate using the polymerase chain reaction

Setting: Tygerberg Hospital, South Africa.Objective: Bone marrow aspirate and biopsy were obtained from 37 patients who were in-patients at the Tygerberg hospital. The specificity and sensitivity of the polymerase chain reaction (PCR) in the detection of Mycobacterium tuberculosis in bone marrow aspirate was evaluated.Design: The PCR was compared to standard culture as well as to clinical and bone marrow biopsy data in 24 patients with suspected tuberculosis (TB).Results: 12 of the 24 patients eventually had definite or probable TB and in these 12 patients the detection incidence was 42% for PCR and 25% for culture.Conclusion: This study confirms that it is possible to use PCR to detect M. tuberculosis in bone marrow aspirate material and that this technique is more sensitive than culture methods. The PCR technique has the added advantage of being a rapid test yielding results within 2 days of sampling. Overall sensitivity for the detection of M. tuberculosis in bone marrow aspirate may be improved to 67% by using both culture and PCR techniques.     

Humoral response to Mycobacterium tuberculosis-specific antigens in African tuberculosis patients with high prevalence of Human immunodeficiency virus infection

Setting: The applicability of serodiagnosis of tuberculosis using Mycobacterium tuberculosis-complex-specific antigens in a Tanzanian population with high prevalence of HIV.Objective: This study was performed to evaluate the usefulness, sensitivity and specificity of serology using M. tuberculosis-specific antigens in the diagnosis of tuberculosis in patients with and without HIV co-infection.Design: Patients with proven pulmonary and extrapulmonary tuberculosis at a major referral centre in Tanzania were enrolled in the study. The control group consisted of patients without a history of previous tuberculosis admitted to the trauma ward and of healthy volunteers. Sera were analysed by an enzyme linked immunoassay (ELISA) using two M. tuberculosis specific proteins as antigen: the 38 kDa protein [3t]and a 17 kDa protein. In addition was recorded presence or absence of BCG scar and tuberculin sensitivity and the sera were tested for HIV and analysed for β-2-microglobulin content.Result: Sensitivity and specificity were markedly reduced in tuberculosis patients with HIV co-infection compared to patients without this disease (73% and 70% versus 52% and 50% respectively).Conclusion: Serology for diagnosis of tuberculosis is not feasible in an HIV endemic region.     

Recurrence of HIV-related tuberculosis in an endemic area may be due to relapse or reinfection

Setting: Two Research Clinics within Nairobi, Kenya, one in the Infectious Diseases Hospital, the national referral centre for tuberculosis, and one in a community based project in Pumwani district, and the Bacterial Molecular Genetics Unit at the London School of Hygiene and Tropical Medicine.Objective: To determine whether recurrence of tuberculosis after ‘adequate’ treatment was due to reinfection with a different isolate of Mycobacterium tuberculosis or to relapse of the original infection.Design: A retrospective comparison by DNA fingerprinting of sets of isolates of M. tuberculosis from patients with recurrence of tuberculosis and in whom isolates from the original episode had been stored was made. Five patients with recurrence of tuberculosis two to nineteen months after adequate treatment and documented clearance of disease were studied.Results: In one patient, fingerprints of the isolates of M. tuberculosis from the recurrence were quite different to those from the original episode; in the other four, the fingerprints were identical.Conclusion: Reinfection rather than relapse was the cause of recurrence in at least one patient. The high ‘relapse’ rates seen in HIV-related tuberculosis in Africa may in part be due to increased susceptibility to reinfection and not to treatment failure.     

Enterovirus Infections in Germany: Comparative Evaluation of Different Laboratory Diagnostic Methods

Background: The diagnosis of an enterovirus infection may be achieved through direct virus detection from fecal or cerebrospinal fluid (CSF) samples by virus isolation or PCR. Serologically, a significant rise in antibody titer may be detected and different enteroviral types can be differentiated using the neutralization assay. Patients and Methods: We investigated the contribution of these different laboratory parameters to the diagnosis of enterovirus infections occurring in the Frankfurt am Main area during the years 1997 to 1999, including an echovirus 30 outbreak in a group of children with aseptic meningitis in 1997. Samples were referred from 1,013 patients; virus isolation was attempted from 579 CSF specimens and from 400 stool samples. 208 CSF samples were tested by PCR. Results: During the echorivus 30 outbreak we identified 22.3% of samples as positive, almost exclusively echovirus 30. In 1998 only 7.1% of samples were positive and a rather broad range of agents was isolated. In 1999 10.4% were positive, predominantly coxsackie B5 and echovirus 11. We could show that in acute enterovirus infections, virus detection by cell culture and PCR is superior to serological methods (neutralization assay and IgM assay). For virus isolation, there was a higher rate of positives from stool compared to CSF (1997: 27.8% versus 25%; 1998: 14.4% versus 3%; 1999: 17.9% versus 8.5%). When comparing PCR and virus isolation from the CSF, the former yielded a higher rate of positive results but was not clearly superior to virus isolation from CSF. Conclusion: The recommended method for the diagnosis of acute enterovirus infections is virus isolation from feces. In cases of suspected aseptic meningitis virus isolation and PCR are valuable for the direct detection of virus in CSF. Received: March 31, 2000 · Revision accepted: March 5, 2001     

Varicella-zoster virus limbic encephalitis in an immunocompromised patient.

A case of limbic encephalitis in a patient who had undergone prolonged immunosuppressive treatment with i.v. cyclophosphamide and oral prednisolone for a microscopic polyangeitis is reported. A brain MRI scan revealed symmetric mesial temporal lobe lesions. Studies of cerebrospinal fluid (CSF) revealed a positive PCR for varicella-zoster virus (VZV) DNA in 2 separate samples. Owing to a delay in diagnosis, intravenous acyclovir was initiated only after 11 d of symptoms. PCR of CSF for VZV DNA became negative on day 14 of treatment while brain lesions had resolved on subsequent MRI scans. Limbic encephalitis is a novel form of VZV infection. When brain imaging is suggestive of limbic encephalitis in an immunocompromised patient, PCR of CSF for VZV DNA should be performed, as early antiviral treatment may improve the outcome.     

Interleukin-6 and Mycobacterium tuberculosis dormancy antigens improve diagnosis of tuberculosis

ObjectivesIFNγ-release assays (IGRAs) used for diagnosis of Mycobacterium (M.) tuberculosis infection have limited sensitivity. Alternative cytokines and M. tuberculosis latency-associated antigens may improve immune-based tests.MethodsMultiplex cytokine analyses was done in culture supernatants after 6-day in vitro restimulation with M. tuberculosis IGRA and latency-associated antigens (i.e. Rv2628, Rv1733) in tuberculosis patients (n = 22) and asymptomatic contacts (AC)s (n = 20) from Ghana.ResultsFour cytokines (i.e. IFNγ, IP-10, IL-22 and IL-6) were significantly increased after IGRA-antigen specific restimulation. IFNγ, IP-10, and IL-22 correlated positively and showed no differences between the study groups whereas IGRA-antigen induced IL-6 was significantly higher in tuberculosis patients. Using adjusted IGRA criteria, IL-6 showed the highest sensitivity for detection of tuberculosis patients (91%) and ACs (85%) as compared to IFNγ, IP-10, and IL-22. Rv2628 and Rv1733 restimulation induced significantly higher IFNγ, IP-10, and IL-22 concentrations in ACs. Combined antigen/cytokine analyses identified study group specific patterns and a combination of Rv2628/Rv1733 induced IFNγ with IGRA-antigen induced IL-6 was optimal for classification of tuberculosis patients and ACs (AUC: 0.92, p<0.0001).ConclusionsWe demonstrate the potency of alternative cytokines, especially IL-6, and latency-associated antigens Rv1733/Rv2628 to improve detection of M. tuberculosis infection and to classify tuberculosis patients and healthy contacts.     

A blind study of the polymerase chain reaction for the detection of mycobacterium tuberculosis DNA

Setting: Nine French laboratories routinely involved in mycobacterial work.Objective: To assess the detection of Mycobacterium tuberculosis in experimental samples by polymerase chain reaction (PCR) using the insertion sequence IS6110 as a target for deoxyribonucleic acid (DNA) amplification.Design: Nine laboratories participated in a blind study of the detection of M. tuberculosis by PCR in 20 coded samples containing either a definite number of M. tuberculosis complex (positive samples) or environmental mycobacteria (four samples) or no mycobacteria (five samples).Results: Five laboratories reported false-positive PCR results, with an average rate of 7%. All laboratories except one reported positive PCR results for samples containing 10⁵ cfu/ml or more. M. tuberculosis DNA was detected in two thirds of samples containing 10⁴ and 10³ cfu/ml, and in one third of the samples containing 10² cfu/ml.Conclusion: The results of the study suggest that PCR using IS6110 as a target for DNA amplication is neither very sensitive nor really specific for the detection of M. tuberculosis.