Molecular diagnostics in tuberculosis

Where are all the Mycobacterium avium subspecies paratuberculosis in patients with Crohn's disease?

Mycobacterium avium subspecies paratuberculosis (MAP) causes a chronic granulomatous inflammation of the intestines, Johne's disease, in dairy cows and every other species of mammal in which it has been identified. MAP has been identified in the mucosal layer and deeper bowel wall in patients with Crohn's disease by methods other than light microscopy, and by direct visualization in small numbers by light microscopy. MAP has not been accepted as the cause of Crohn's disease in part because it has not been seen under the microscope in large numbers in the intestines of patients with Crohn's disease. An analysis of the literature on the pathology of Crohn's disease and on possible MAP infection in Crohn's patients suggests that MAP might directly infect endothelial cells and adipocytes and cause them to proliferate, causing focal obstruction within already existing vessels (including granuloma formation), the development of new vessels (neoangiogenesis and lymphangiogenesis), and the "creeping fat" of the mesentery that is unique in human pathology to Crohn's disease but also occurs in bovine Johne's disease. Large numbers of MAP might therefore be found in the mesentery attached to segments of intestine affected by Crohn's disease rather than in the bowel wall, the blood and lymphatic vessels running through the mesentery, or the mesenteric fat itself. The walls of fistulas might result from the neoangiogenesis or lymphangiogenesis that occurs in the bowel wall in Crohn's disease and therefore are also possible sites of large numbers of MAP. The direct visualization of large numbers of MAP organisms in the tissues of patients with Crohn's disease will help establish that MAP causes Crohn's disease.

Electrospray ionization-tandem mass spectrometry analysis of the mycolic acid profiles for the identification of common clinical isolates of mycobacterial species

Mycolic acids are unique and complex molecular structures found in mycobacterial species. In the present study, we investigated whether electrospray ionization-tandem mass spectrometry (ESI-MS/MS) can be used to identify mycobacterial species based on their mycolic acid profiles. Clinical isolates of Mycobacterium tuberculosis complex and 18 nontuberculosis mycobacterial (NTM) species identified by PCR-restriction fragment length polymorphism (RFLP) or real-time PCR were used for this analysis. Crude lipid extracts were prepared by saponifying 1-2 colonies of individual isolates of mycobacterial species and by chloroform and methanol (2:1, v/v) extraction. ESI-MS/MS in negative ion mode with high cone voltage and collision energy was used for mycolic acid profiling analysis. Combinatorial precursor ion scans of m/z 395, 367, and 339 in the range of m/z 1000-1400 resulted in spectra specific to individual mycobacteria. M. tuberculosis complex and M. pulveris showed major ions by performing precursor ion scans on m/z 395 and 367, while other NTM species showed major ions by performing scans on m/z 367 and 339. The different NTM species examined showed different species dependent mycolic acid profiles. In conclusion, we describe a rapid, reliable, and informative ESI-MS/MS protocol for mycolic acid profiling in mycobacterial species, which allows mycobacterial species to be easily identified in clinical laboratories.

Evaluation of different primer sets for the rapid diagnosis of tuberculosis

Pleural fluid samples from patients with exudative effusion who were diagnosed with tuberculous pleuritis are examined using a new designed primer set based on IS1081 gene (IS1081-PCR) and rpoB-PCR. The PCR results are compared with the results of the sample cultures, using Loewenstein-Jensen (LJ) medium and Ziehl-Neelsen (ZN) staining. Of 78 cases that were confirmed as tuberculous pleuritis by histopathology, supported by sputum culture, biochemical markers (adenosine deaminase, gamma interferon and tumor necrosis factor), radiographic and clinical data, 61 (78.2%) were positive by IS1081-PCR, 43 (55.1%) by rpoB-PCR, 17 (21.7%) by culture and 3 (3.8%) by ZN stain. When IS1081-PCR test results were compared with the confirmed culture, the sensitivity, specificity, positive predictive value and negative predictive value for the IS1081-PCR were 94.1, 55.7, 37.2 and 97.1%, respectively. The corresponding values for the rpoB-PCR were 94.1, 26.2, 26.2 and 94.1%, respectively. When tests results were compare with the confirmed radiographic, histopathology, biochemical markers and clinical diagnosis of tuberculous pleuritis, the IS1081-PCR assay is more sensitive, specific and reliable than both rpoB-PCR assay and culture.

[Evaluation of the performances of AdvanSure TB/NTM real time PCR kit for detection of mycobacteria in respiratory specimens]

BACKGROUND

PCR is a widely used method for rapid and accurate diagnosis of mycobacteriosis. The sensitivity and specificity of a real time PCR kit newly developed in Korea were evaluated for detecting mycobacteria in respiratory specimens.

METHODS

One hundred twenty nine Mycobacterium tuberculosis (TB) culture positive respiratory specimens (82 AFB stain positive and 47 stain negative specimens) were used for evaluation of the sensitivity. Nine non-tuberculous mycobacteria (NTM) culture positive specimens were also included. For evaluation of the specificity, 48 AFB stain and culture negative respiratory specimens from patients who were initially not fully excluded from mycobacterial diseases (specificity group 1) were used. Other 51 respiratory specimens from patients who were not suspected of mycobacterial diseases were also included (specificity group 2). Real time PCR was performed by using AdvanSure TB/NTM real time PCR Kit (LG Lifescience, Korea) and SLAN real time PCR detection system (LG Lifescience). The target genes of TB and NTM were IS6110 and rpoB, respectively.

RESULTS

Among 129 TB culture positive specimens, 82 of 82 AFB stain positive specimens (100%) and 35 of 47 (74.5%) stain negative specimens revealed real time PCR positivity for TB, resulting in sensitivity of 90.7%. Five of nine NTM culture positive specimens resulted in real time PCR positivity for NTM (55.6%). Forty seven of 48 specimens (97.9%) and all 51 specimens (100%) of the specificity group 1 and 2, respectively, were real time PCR negative for TB and NTM.

CONCLUSIONS

AdvanSure TB/NTM real time PCR Kit should be useful for detecting TB in respiratory specimens with high sensitivity and specificity.

Evaluation of methods for detection and identification of Mycobacterium species in patients suspected of having pulmonary tuberculosis

Tuberculosis control is a priority for the Ministry of Health policies in Brazil. In the present work, the detection of Mycobacterium tuberculosis by the Polymerase Chain Reaction (PCR) was standardized, and the laboratory diagnosis of pulmonary tuberculosis was evaluated comparing baciloscopy, culture and PCR tests. The study was carried out with 117 sputum samples from different patients suspected of having pulmonary tuberculosis, for whom physicians had ordered a baciloscopy test. Baciloscopy was performed using the Ziehl-Neelsen method, and culture was performed by incubation of treated samples in Lowenstein-Jensen's medium at 37°C for eight weeks. For PCR, DNA was amplified with a specific pair of primers to the M. tuberculosis complex, with a resulting product of 123 bp from the insertion element IS6110. Three (2.56%) samples presented a positive baciloscopy result and a positive PCR result (100% agreement), and nine (7.69%) presented Mycobacterium sp. growth in culture (P= 0.1384). Among six samples with positive results in culture, one was identified by PCR-RFLP as belonging to the M. tuberculosis complex and one was identified as a non-tuberculosis mycobacteria. Sensitivity and specificity of PCR compared to culture were 33.3% and 100%, respectively.

Evaluation of reverse transcription loop-mediated isothermal amplification in conjunction with ELISA-hybridization assay for molecular detection of Mycobacterium tuberculosis

Traditional culture, followed by a panel of biochemical tests for the diagnosis of tuberculosis (TB), is time-consuming, and rapid identification of Mycobacterium tuberculosis is crucial for the early administration of appropriate therapy. In this study, the reverse transcription loop-mediated isothermal amplification combined with enzyme-linked immunosorbent hybridization (RT-LAMP-ELISA-hybridization) assay has been designed for the rapid detection of 16S rRNA in clinical isolates of M. tuberculosis. This assay reproducibly detected a single copy, as opposed to 2000 copies of MTB 16S rRNA detected by conventional gel electrophoresis. Among the 150 specimens of sputum analysed, RT-LAMP-ELISA-hybridization assay had a sensitivity of 94.1% in the culture method, compared to the Amplified M. tuberculosis Direct Test (AMTD), 91.1% and the 88.2% sensitivity of acid-fast staining. Furthermore, RT-LAMP-ELISA-hybridization assay is more cost-effective when compared to the real-time TaqMan RT-PCR and AMTD assays. In conclusion, our results suggest that the RT-LAMP-ELISA-hybridization assay is a highly sensitive, low cost diagnostic tool useful for the rapid and accurate direct diagnosis of sputum specimens, and is suitable for routine clinical use.

Tuberculosis infection of the breast mistaken for granulomatous mastitis: a case report

BACKGROUND

Tuberculosis of the breast is an uncommon disease with non-specific clinical, radiological and histological findings. Misdiagnosis is common as biopsy specimens are pauci-bacillary and investigations such as microscopy and culture are frequently negative.

CASE PRESENTATION

We report a case of a breast abscess in a 34-year old Bangladeshi woman attributed to tuberculosis infection. Equivocal histology, negative Ziehl-Neelsen stain and culture for acid-fast bacilli resulted in the abscess initially being diagnosed as granulomatous mastitis and treated accordingly. However failure to respond to therapy raised suspicion of culture negative breast tuberculosis. Treatment with standard antituberculosis drugs was associated with complete resolution of the breast abscess.

CONCLUSION

This case highlights the difficulty in differentiating culture negative tuberculosis from granulomatous mastitis and the importance of a high index of clinical suspicion.

DNA microarrays in the clinic: infectious diseases

We argue that the most-promising area of clinical application of microarrays in the foreseeable future is the diagnostics and monitoring of infectious diseases. Microarrays for the detection and characterization of human pathogens have already found their way into clinical practice in some countries. After discussing the persistent, yet often underestimated, importance of infectious diseases for public health, we consider the technologies that are best suited for the detection and clinical investigation of pathogens. Clinical application of microarray technologies for the detection of mycobacteria, Bacillus anthracis, HIV, hepatitis and influenza viruses, and other major pathogens, as well as the analysis of their drug-resistance patterns, illustrate our main thesis.

Orbital tuberculosis: a review of the literature

PURPOSE

To provide an up-to-date review of the clinical presentations, investigations, and management of orbital tuberculosis (OTB).

METHODS

Systematic review of the literature concerning OTB, limiting the results to English-language peer-reviewed journals.

RESULTS

Seventy-nine patients from 39 publications were identified as cases of OTB. The condition presents in one of five forms: classical periostitis; orbital soft tissue tuberculoma or cold abscess, with no bony involvement; OTB with bony involvement; spread from the paranasal sinuses; and tuberculous dacryoadenitis. The ocular adnexa, including the nasolacrimal system and overlying skin, may also be involved.

CONCLUSIONS

Diagnosis can be difficult and may necessitate an orbital biopsy, in which acid-fast bacilli (AFB) and characteristic histopathology may be seen. Growth of Mycobacterium tuberculosis (mTB) from such a specimen remains the gold standard for diagnosis. Ancillary investigations include tuberculin skin tests and chest radiography, but more recently alternatives such as whole blood interferon-gamma immunological tests and PCR-based tests of pathological specimens have proven useful. The management of OTB is complex, requiring a stringent public health strategy and high levels of patient adherence, combined with long courses of multiple anti-tuberculous medications. The interaction of the human immunodeficiency virus (HIV) with TB may further complicate management.

Multidrug-resistant and extensively drug-resistant Mycobacterium tuberculosis: epidemiology and control

The emergence of multidrug-resistant (MDR)-TB and, more recently, of extensively drug-resistant (XDR)-TB is a real threat to achieve TB control and elimination. Over 400,000 new cases of MDR-TB occur each year and, although their number is currently unknown, XDR cases are recognized in every setting where there has been the capacity to detect them. The long-term vision for the full control of MDR-TB requires the scaling-up of culture and drug-susceptibility testing capacity, which is very limited in disease-endemic countries, and the expanded use of high-technology assays for rapid determination of resistance. MDR cases are treatable and well designed regimens, largely based on second-line anti-TB drugs, can considerably improve cure rates. However, treatment regimens need to be markedly improved through the introduction of less toxic and more powerful drugs, thus reducing duration of treatment and tolerability. This is of utmost importance for XDR-TB cases. The prevalence of MDR-TB and XDR-TB are inversely correlated with the quality of TB control and the proper use of second-line anti-TB drugs. Adherence to proper standards of care and control is imperative and a top priority of all TB control efforts. However, the risk of an uncontrollable epidemic of MDR- and XDR-TB is real considering current levels of financing and commitment to care.

Infections in post-tsunami victims

Two tsunami survivors from Banda Acheh, Sumatra, presented with pyrexia of unknown origin and a nonresolving left-sided empyema, respectively. Both children had mixed infections of tuberculosis and melioidosis; Salmonella typhi was also present in the second patient. Mixed infections are common late sequela complications in post-tsunami victims.

Primary nasolacrymal tuberculosis diagnosed after dacryocytorhinostomy

Although tuberculosis (TB) is common and well recognized in many countries, unusual presentations of the disease sometimes raise difficulties in differential diagnosis. Primary tuberculosis of the lacrimal sac and the nasolacrimal duct is an extremely rare presentation of extra-pulmonary tuberculosis. Dacryocystorhinostomy alone is not sufficient for the treatment of these patients and an anti-tuberculous therapy has to be added. Here we present a patient with primary tuberculosis, which is limited to the inferior meatus and filled the entire lacrimal sac on the left side. The patient underwent endoscopic dacryocystorhinostomy due to obstruction of the nasolacrimal duct and culture of the granulation tissue, taken from the lacrimal sac revealed mycobacterial tuberculosis. The patient was improved with anti-tuberculous therapy that was added to the surgery. Primary tuberculosis is a rare granulomatous disease of the nasolacrimal system, which should be considered in the differential diagnosis to plan the effective treatment.

Molecular characteristics of rifampicin- and isoniazid-resistant Mycobacterium tuberculosis isolates from the Russian Federation

OBJECTIVES

Three Mycobacterium tuberculosis genetic loci--rpoB and katG genes and the fabG1(mabA)-inhA operon promoter region--were studied to reveal the mutations associated with rifampicin and isoniazid resistance.

METHODS

Four hundred and twelve isolates of M. tuberculosis from different regions of the Russian Federation were collected during 1997-2005. A matrix-assisted laser-desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS)-based minisequencing method was used for the detection of mutations.

RESULTS

Thirteen different variants of single mutations in codons 533, 531, 526, 516, 513 and 511 of the rifampicin resistance-determining region of the rpoB gene as well as the TTG insertion in the 514a position were found among the rifampicin-resistant isolates. Single nucleotide substitutions in codons 531, 526 and 516 (64.8%, 10.3% and 7.7%, respectively) were the most prevalent mutations. Codon 526 was shown to be the most variable of all. No mutations were detected in rpoB genes for 29 (10.7%) of the rifampicin-resistant isolates. 76.9% of the isoniazid-resistant isolates carried single mutations in codon 315 of the katG gene. For another 12.9% of them, double mutations in the katG gene and the fabG1(mabA)-inhA promoter region were revealed. No mutations were detected in 8.2% of the isoniazid-resistant isolates.

CONCLUSIONS

Molecular analysis of the loci of rpoB and katG genes and the inhA promoter region of 412 M. tuberculosis clinical isolates from various parts of the Russian Federation was carried out. The new MALDI-TOF MS-based method may be used for rapid and accurate monitoring of the spread of drug resistance.

Biologie moléculaire et microbiologie clinique en 2007

La biologie moléculaire est omniprésente en biologie médicale et plus particulièrement en microbiologie. De nombreux articles démontrent son importance tant dans le domaine du diagnostic que du pronostic, de l'évaluation thérapeutique, de l'épidémiologie ou des risques biologiques naturels ou non. La quantité considérable d'articles sur ce sujet n'apporte pas toujours une réponse évidente sur le rôle de la biologie moléculaire dans un laboratoire de microbiologie qu'il soit hospitalier ou non. Cette revue constitue une synthèse des apports de cette discipline en microbiologie. À partir de cet état des lieux, certaines questions se posent, par exemple : la biologie moléculaire constitue-t-elle un réel apport en microbiologie ? Dans quelles indications prescrire un examen de biologie moléculaire ? Les réponses ne sont pas toujours simples. Elles sont évidentes dans certains cas (l'hépatite C par exemple) et le sont moins dans d'autres, la tuberculose par exemple. Dans la première partie de l'article, nous avons parlé des généralités appliquées à la microbiologie. Dans cette deuxième partie, nous abordons certaines applications, reflets de l'importance prise par la biologie moléculaire en microbiologie.

Molecular epidemiology and prevalence of mutations conferring rifampicin and isoniazid resistance in Mycobacterium tuberculosis strains from the southern Ukraine

Understanding the molecular epidemiology of tuberculosis (TB) and mutations in genes associated with drug resistance may contribute to the development of appropriate interventions to improve tuberculosis control. A structured questionnaire was used to collect basic epidemiological data from 589 patients with radiologically confirmed TB in the Odessa and Nikolaev regions of the Ukraine in 2003-2004. A non-commercial reverse hybridisation assay and DNA sequencing were used to detect mutations associated with rifampicin and isoniazid resistance. Genotyping was performed using multilocus variable number tandem repeat (VNTR) typing and spoligotyping. Mutations conferring rifampicin and isoniazid resistance were detected in 32.9% and 44.0%, respectively, of 225 Mycobacterium tuberculosis isolates from individual consecutive patients. Mutations in codon 531 and codon 315 of the rpoB and katG genes, respectively, were predominant among drug-resistant isolates. Multidrug (MDR) resistance rates were significantly higher among former prison inmates compared with non-prisoners (54.8% vs. 27.3%; RR 2.01; 95% CI 1.35-2.97) and the prevalence of mutations was higher in Beijing strains sharing the VNTR signature 223325173533424 than in other Beijing strains (71.4% vs. 45.7%; RR 1.74; 95% CI 1.17-2.57), suggesting that this group may be responsible for rapid transmission of MDR TB in the southern Ukraine.

Use of the BACTEC Mycobacteria Growth Indicator Tube 960 automated system for recovery of Mycobacteria from 9,558 extrapulmonary specimens, including urine samples

The BACTEC Mycobacteria Growth Indicator Tube 960 (MGIT 960) system was applied for recovery of mycobacteria from extrapulmonary specimens and compared with solid media (Löwenstein-Jensen and Stonebrink). A total of 9,558 specimens were investigated, comprising 3,074 body fluids, 1,878 tissues, and 2,069 urine samples, from which the recovery of mycobacteria was not yet established for MGIT 960. In total, the MGIT 960 was able to detect 446 (90.3%) of the 494 isolates of Mycobacterium tuberculosis complex (MTBC) and 223 (86.0%) out of the 259 isolates of nontuberculous mycobacteria (NTM). In comparison to this, culture on solid medium revealed 358 (72.6%) MTBC isolates and 164 (66.8%) NTM isolates. While 136 (27.6%) of the MTBC isolates and 95 (19.2%) of the NTM isolates were recovered from the MGIT 960 only, 48 (9.7%) of the MTBC isolates and 36 (13.9%) NTM isolates grew only on solid media. Thus, the overall sensitivities for the recovery of mycobacteria from extrapulmonary specimens with MGIT 960 and solid media were 88.8% and 69.3%, respectively. However, the efficiency of the MGIT 960 system can be maximized with additional culture on solid media.