Comparison of the radiometric BACTEC 460 TB culture system and Löwenstein–Jensen medium for the isolation of mycobacteria in cutaneous tuberculosis and their drug susceptibility pattern

Lupus vulgaris: a narrative review

Lupus vulgaris (LV) is a type of paucibacillary cutaneous tuberculosis that can occur due to inoculation, lymphatic, or hematogenous route. It occurs in a previously sensitized individual with high immunity to tuberculosis. LV can have different morphology of presentation, which can lead to difficulty in diagnosis. The Tuberculin test is strongly positive. Histopathology will show epithelioid granulomas in the superficial dermis and acid-fast bacilli rarely demonstrable within the granulomas. Dermoscopy will show focused linear vessels on a yellow to orange background. Culture is the gold standard for diagnosis, but its positivity rate is low. Mycobacterium tuberculosis bacilli can be detected using polymerase chain reaction from the lesions. Histopathology, tuberculin test, dermoscopy, molecular test, and culture would help diagnose LV. This review discusses the introduction, pathogenesis, clinical features, differential diagnosis, investigations, complications, and treatment of lupus vulgaris in detail. This review can help the dermatologist understand the condition better with appropriate diagnosis and therapy.

Cutaneous tuberculosis. Part II: Complications, diagnostic workup, histopathologic features, and treatment

Despite the availability of effective treatment regimens for cutaneous tuberculosis, challenges to disease control result from delayed diagnosis, infection with multidrug-resistant mycobacterial strains, and coinfection with HIV. Delayed diagnosis can be mitigated when dermatologists are sensitized to the clinical signs and symptoms of infection and by the incorporation of appropriate diagnostic tests. All cases of cutaneous tuberculosis should be confirmed with histopathology and culture with or without molecular testing. In each case, a thorough evaluation for systemic involvement is necessary. Mycobacteria may not be isolated from cutaneous tuberculosis lesions and therefore, a trial of antituberculosis treatment may be required to confirm the diagnosis. The second article in this 2-part continuing medical education series describes the sequelae, histopathology, and treatment of tuberculosis.

Clinicoepidemiological characteristics of cutaneous tuberculosis in 1458 Indian patients: a retrospective analytical study from a tertiary care center

BACKGROUND

Tuberculosis (TB) has been one of the most challenging infectious diseases globally. Cutaneous tuberculosis (CTB) accounts for 0.5-2% of extrapulmonary TB and is often missed owing to its varying morphology and paucibacillary nature.

METHODS

In this retrospective analytical study, we share our 22-year experience to describe the clinicoepidemiological features and treatment response of CTB in 1458 Indian patients. In each patient, detailed history was followed by clinical examination, hematological and biochemical investigations, Mantoux testing, chest x-ray, and other specialized investigations to detect coexisting systemic foci. Clinical diagnosis of CTB was confirmed on histopathology/cytology and response to standard antitubercular treatment (ATT). All details were recorded on a predesigned proforma.

RESULTS

Of 1458 eligible patients, 803 were children. The mean disease duration was 15.3 months. Lupus vulgaris (40.4%) was the most common clinical variant, followed by scrofuloderma (32.7%) and lichen scrofulosorum (15.2%). Other variants included tuberculosis verrucosa cutis, gumma, tuberculids, and inoculation TB. Multiple clinical variants were observed in 3.6% of patients. A total of 41.4% of patients had coexistent systemic foci; in lymph nodes (50.4%), lungs (35.6%), bone (10.3%), and abdomen (5.8%). TB foci were also observed at uncommon locations like the eye, central nervous system, and genital organs. Treatment response to ATT was favorable in 99.2%.

INTERPRETATION

The burden of CTB still persists in developing countries. The diagnosis is often missed due to the wide spectrum of clinical and histological presentations. Awareness among clinicians of varying aspects of CTB is of paramount importance for early diagnosis and management and will significantly prevent morbidity and disease complications.

Role of GeneXpertMTB/RIF in the diagnosis of cutaneous tuberculosis

BACKGROUND

cutaneous involevemtn is an important extrapulmonary manifestation of tuberculosis. It is a paucibacillary condition and has diverse clinical presentations. Sufficient data is not available regarding role of GeneXpertMTB/RIF in cutanoues tuberculosis.

METHODS

in this study, BacT/Alert3D and response to antitubercular therapy were taken as gold standard and performance of GeneXpertMTB/RIF was evaluated against it in clinically and histopathologically suspected cases of cutaneous tuberculosis.

RESULTS

forty seven patients were included in the study of which commonest presentation was scrofuloderma (42.6%) followed by lupus vulgaris (40.4%). Granulomatous inflammation on histopathology was seen in 75.5% patients on skin biopsy. Sic patients had extracutaneous focus of tuberculosis. In 14 (29.79%), culture of skin biopsy was positive for M. tuberculosis and all showed complete response to ATT in 6 months. GeneXpertMTB/RIF detected M. tuberculsois in 4 samples.

CONCLUSION

GeneXpertMTB/RIF is not a reliable tool for diagnosis of cutaneous tuberculosis. Clinic-histopathological correlation along with response to ATT is needed for confirmation of diagnosis of cutaneous tuberculosis.

Diagnostic Dilemma of Cutaneous Tuberculosis: Opening of the Pandora's Box

ABSTRACT

Tuberculosis in all forms, that is, pulmonary (PTB) or extrapulmonary (EPTB), is a universal health problem. Cutaneous tuberculosis (CTb) remains one of the least studied and often under-reported variants of EPTB because of its wide and protean clinical presentation. The diagnosis of CTb remains challenging because of lack of sensitive and specific investigations for its diagnosis. The sensitivity of some of the traditional tests is low because of low concentration of mycobacteria in paucibacillary lesions. Besides it is difficult to distinguish between M. tuberculosis (MTb) and other mycobacterial species in skin biopsies morphologically. Molecular methods may target either MTb DNA or RNA, and serve as promising tools in the diagnosis of various forms of CTb, with high sensitivity and rapidity. This review is focused on diagnostic challenges of CTb and to discuss various methods and newer technologies for diagnosing CTb. This will help the dermatologists and dermatopathologists to elucidate and accurately diagnose CTb from other infectious granulomatous dermatitis for appropriate timely treatment of the patient.

Revisiting the methods for detecting Mycobacterium tuberculosis: what has the new millennium brought thus far?

Tuberculosis (TB) affects around 10 million people worldwide in 2019. Approximately 3.4 % of new TB cases are multidrug-resistant. The gold standard method for detecting Mycobacterium tuberculosis, which is the aetiological agent of TB, is still based on microbiological culture procedures, followed by species identification and drug sensitivity testing. Sputum is the most commonly obtained clinical specimen from patients with pulmonary TB. Although smear microscopy is a low-cost and widely used method, its sensitivity is 50-60 %. Thus, owing to the need to improve the performance of current microbiological tests to provide prompt treatment, different methods with varied sensitivity and specificity for TB diagnosis have been developed. Here we discuss the existing methods developed over the past 20 years, including their strengths and weaknesses. In-house and commercial methods have been shown to be promising to achieve rapid diagnosis. Combining methods for mycobacterial detection systems demonstrates a correlation of 100 %. Other assays are useful for the simultaneous detection of M. tuberculosis species and drug-related mutations. Novel approaches have also been employed to rapidly identify and quantify total mycobacteria RNA, including assessments of global gene expression measured in whole blood to identify the risk of TB. Spoligotyping, mass spectrometry and next-generation sequencing are also promising technologies; however, their cost needs to be reduced so that low- and middle-income countries can access them. Because of the large impact of M. tuberculosis infection on public health, the development of new methods in the context of well-designed and -controlled clinical trials might contribute to the improvement of TB infection control.

Extrapulmonary Tuberculosis—An Update on the Diagnosis, Treatment and Drug Resistance

Pathogenic Mycobacterium tuberculosis complex organisms (MTBC) primarily cause pulmonary tuberculosis (PTB); however, MTBC are also capable of causing disease in extrapulmonary (EP) organs, which pose a significant threat to human health worldwide. Extrapulmonary tuberculosis (EPTB) accounts for about 20–30% of all active TB cases and affects mainly children and adults with compromised immune systems. EPTB can occur through hematogenous, lymphatic, or localized bacillary dissemination from a primary source, such as PTB, and affects the brain, eye, mouth, tongue, lymph nodes of neck, spine, bones, muscles, skin, pleura, pericardium, gastrointestinal, peritoneum, and the genitourinary system as primary and/or disseminated disease. EPTB diagnosis involves clinical, radiological, microbiological, histopathological, biochemical/immunological, and molecular methods. However, only culture and molecular techniques are considered confirmatory to differentiate MTBC from any non-tuberculous mycobacteria (NTM) species. While EPTB due to MTBC responds to first-line anti-TB drugs (ATD), drug susceptibility profiling is an essential criterion for addressing drug-resistant EPTB cases (DR-EPTB). Besides antibiotics, adjuvant therapy with corticosteroids has also been used to treat specific EPTB cases. Occasionally, surgical intervention is recommended, mainly when organ damage is debilitating to the patient. Recent epidemiological studies show a striking increase in DR-EPTB cases ranging from 10–15% across various reports. As a neglected disease, significant developments in rapid and accurate diagnosis and better therapeutic interventions are urgently needed to control the emerging EPTB situation globally. In this review, we discuss the recent advances in the clinical diagnosis, treatment, and drug resistance of EPTB.

Diagnosis of Tuberculosis: Nanodiagnostics Approaches

Tuberculosis (TB) remains one of the most devastating infectious diseases worldwide. The burden of TB is alarmingly high in developing countries, where diagnosis latent TB infection (LTBI), Extra-pulmonary tuberculosis (EPTB), drug-resistant tuberculosis (DR-TB), HIV-associated TB, and paediatric TB is still a challenge. This is mainly due to delayed or misdiagnosis of TB, which continues to fuel its worldwide epidemic. The ideal diagnostic test is still unavailable, and conventional methods remain a necessity for TB diagnosis, though with poor diagnostic ability. The nanoparticles have shown potential for the improvement of drug delivery, reducing treatment frequency and diagnosis of various diseases. The engineering of antigens/antibody nanocarriers represents an exciting front in the field of diagnostics, potentially flagging the way toward development of better diagnostics for TB. This chapter discusses the presently available tests for TB diagnostics and also highlights the recent advancement in the nanotechnology-based detection tests for M. tuberculosis.

Vulvar Tuberculosis Cutis Orificialis Concomitant to Pulmonary Tuberculosis: A Case Report

Tuberculosis (TB) is a common condition with increasing incidence worldwide. Cutaneous TB represents a small portion of extrapulmonary TB. Health care professionals must be aware of cutaneous forms of TB to avoid delay in diagnosis and treatment. We present a case of a 59-year-old woman with vulvar TB cutis orificialis in association with pulmonary TB without any other involvement of genitourinary system. We discuss epidemiological aspects, classification, treatment, range of histopathological patterns, and use of ancillary techniques for diagnosis.

Rapid culture-based detection of living mycobacteria using microchannel electrical impedance spectroscopy (m-EIS)

Background

Multiple techniques exist for detecting Mycobacteria, each having its own advantages and drawbacks. Among them, automated culture-based systems like the BACTEC-MGIT™ are popular because they are inexpensive, reliable and highly accurate. However, they have a relatively long “time-to-detection” (TTD). Hence, a method that retains the reliability and low-cost of the MGIT system, while reducing TTD would be highly desirable.

Methods

Living bacterial cells possess a membrane potential, on account of which they store charge when subjected to an AC-field. This charge storage (bulk capacitance) can be estimated using impedance measurements at multiple frequencies. An increase in the number of living cells during culture is reflected in an increase in bulk capacitance, and this forms the basis of our detection. M. bovis BCG and M. smegmatis suspensions with differing initial loads are cultured in MGIT media supplemented with OADC and Middlebrook 7H9 media respectively, electrical “scans” taken at regular intervals and the bulk capacitance estimated from the scans. Bulk capacitance estimates at later time-points are statistically compared to the suspension’s baseline value. A statistically significant increase is assumed to indicate the presence of proliferating mycobacteria.

Results

Our TTDs were 60 and 36 h for M. bovis BCG and 20 and 9 h for M. smegmatis with initial loads of 1000 CFU/ml and 100,000 CFU/ml respectively. The corresponding TTDs for the commercial BACTEC MGIT 960 system were 131 and 84.6 h for M. bovis BCG and 41.7 and 12 h for M smegmatis, respectively.

Conclusion

Our culture-based detection method using multi-frequency impedance measurements is capable of detecting mycobacteria faster than current commercial systems.

Cutaneous tuberculosis: diagnosis, histopathology and treatment - part II

The evolution in the knowledge of tuberculosis' physiopathology allowed not only a better understanding of the immunological factors involved in the disease process, but also the development of new laboratory tests, as well as the establishment of a histological classification that reflects the host's ability to contain the infectious agent. At the same time, the increasing bacilli resistance led to alterations in the basic tuberculosis treatment scheme in 2009. This article critically examines laboratory and histological investigations, treatment regimens for tuberculosis and possible adverse reactions to the most frequently used drugs.

Incidence of multidrug-resistant tuberculosis disease in children: systematic review and global estimates

BACKGROUND

Multidrug-resistant tuberculosis threatens to reverse recent reductions in global tuberculosis incidence. Although children younger than 15 years constitute more than 25% of the worldwide population, the global incidence of multidrug-resistant tuberculosis disease in children has never been quantified. We aimed to estimate the regional and global annual incidence of multidrug-resistant tuberculosis in children.

METHODS

We developed two models: one to estimate the setting-specific risk of multidrug-resistant tuberculosis among child cases of tuberculosis, and a second to estimate the setting-specific incidence of tuberculosis disease in children. The model for risk of multidrug-resistant tuberculosis among children with tuberculosis needed a systematic literature review. We multiplied the setting-specific estimates of multidrug-resistant tuberculosis risk and tuberculosis incidence to estimate regional and global incidence of multidrug-resistant tuberculosis disease in children in 2010.

FINDINGS

We identified 3403 papers, of which 97 studies met inclusion criteria for the systematic review of risk of multidrug-resistant tuberculosis. 31 studies reported the risk of multidrug-resistant tuberculosis in both children and treatment-naive adults with tuberculosis and were used for evaluation of the linear association between multidrug-resistant disease risk in these two patient groups. We identified that the setting-specific risk of multidrug-resistant tuberculosis was nearly identical in children and treatment-naive adults with tuberculosis, consistent with the assertion that multidrug-resistant disease in both groups reflects the local risk of transmitted multidrug-resistant tuberculosis. After application of these calculated risks, we estimated that around 999,792 (95% CI 937,877-1,055,414) children developed tuberculosis disease in 2010, of whom 31,948 (25,594-38,663) had multidrug-resistant disease.

INTERPRETATION

Our estimates underscore that many cases of tuberculosis and multidrug-resistant tuberculosis disease are not being detected in children. Future estimates can be refined as more and better tuberculosis data and new diagnostic instruments become available.

FUNDING

US National Institutes of Health, the Helmut Wolfgang Schumann Fellowship in Preventive Medicine at Harvard Medical School, the Norman E Zinberg Fellowship at Harvard Medical School, and the Doris and Howard Hiatt Residency in Global Health Equity and Internal Medicine at the Brigham and Women's Hospital.

Cutaneous tuberculosis in children

Cutaneous tuberculosis is a rare form of extrapulmonary tuberculosis that accounts for 1% to 2% of cases. Childhood skin tuberculosis represents 18% to 82% of all cutaneous tuberculosis cases. Scrofuloderma and lupus vulgaris are the two most common clinical forms in children. An increase in the number of tuberculids, especially lichen scrofulosorum, has been observed in the last several years. Cutaneous tuberculosis in children can be severe and have a protracted course. Multiplicity of lesions and multifocal disseminated involvement in scrofuloderma and lupus vulgaris is common. Scrofuloderma progressing to gummatous lesions (scrofulous gumma) is mostly described in children. Morbidities and deformities are more severe in children.

[Scrofuloderma: a misleading lesion]

We describe a case of scrofuloderma in an 8-year-old boy with a cutaneous tuberculosis lesion.

CASE REPORT

The child had spent holidays in Morocco. He presented a cutaneous lesion of the thigh which turned into an abscess with suppuration, in spite of surgical drainage. The lymph node analysis showed Koch bacilli and granuloma, leading to the diagnosis of scrofuloderma. Further exams found no other lesion. The course was favorable under treatment.

COMMENTS

With lupus vulgaris, scrofuloderma is the most common cutaneous tuberculosis lesion in children, particularly in developing countries. It is often associated with other organ lesions, such as bone or lung, and these must be sought. Scrofulodermas are unusual in Western countries, leading to misdiagnosis. Fortunately, adapted treatment most often results in recovery.

Evaluation of BACTEC 460 TB system for rapid in vitro screening of drugs against latent state Mycobacterium tuberculosis H37Rv under hypoxia conditions

Mycobacterium tuberculosis exhibits latent state due to its ability to survive for extended periods under oxygen depletion conditions. The conventional plating method employed for in vitro screening of antitubercular agents against latent state M. tuberculosis is laborious and time consuming exercise. Towards this end, BACTEC 460 TB system of antitubercular screening was evaluated for testing efficacy of antimicrobial agents in hypoxia induced model of latent tuberculosis, in vitro. In this study, drugs like isoniazid, metronidazole and rifampin were tested at concentrations- 2, 10 and 50 microg/ml for their antilatency activity by using BACTEC and conventional methods. Results obtained from both the methods were comparable (P>0.05) and a good correlation was observed between colony forming units and growth index values. Further, time to determine mycobacterial growth was significantly reduced (P<or=0.001) in BACTEC method (4-7 days) as compared to plating method (26-30 days). BACTEC method was found to be faster, cost effective and more sensitive as compared to plating method. Being rapid, reliable and reproducible, this method can be a promising alternative to conventional plating method for screening of potential antitubercular agents in in vitro models of latent tuberculosis.