Evaluation of the MB/BacT system compared with Middlebrook 7H11 and Lowenstein-Jensen media for detection and recovery of mycobacteria from clinical specimens

Multicenter matched-pair study comparing BACT/ALERT® MP reagent systems for the recovery of mycobacteria from specimens other than blood

The BACT/ALERT® MP Reagent System is a broth culture medium for optimal detection and recovery of mycobacteria from clinical samples. The MP formulation was recently modified to improve detection and recovery times. A multicenter prospective matched pair study design was conducted to validate the performance of improved MP (MP-I) versus current MP (MP-C) bottles utilizing nonsterile and normally sterile samples, except blood, from patients suspected of having mycobacterial infections. A total of 1488 clinical samples were collected to obtain 212 mycobacteria samples by either or both MP culture bottles. MP-I and MP-C sensitivities were 86.6% and 81.4%, respectively, but the difference was not significant (P = 0.163) while specificities were 96.8% and 93.8%, respectively, and that difference was significant (P = 0.002). Overall recovery was 94.34% for MP-I and 88.68% for MP-C (recovery was 100% for both bottles with 52 seeded samples). Overall performance of MP-I was better than MP-C for sensitivity, specificity, and recovery.

Accuracy of the color plate micro-colony detection for the diagnosis of Mycobacterium tuberculosis complex in Northwest Ethiopia

BACKGROUND

Accurate and timely tuberculosis diagnosis is the primary step for initiating effective treatment. The color plate agar-based culture test (TB-CX test) is low cost, simple to use and detects Mycobacterium tuberculosis faster. Therefore, the main objective of this study was to compare the diagnostic accuracy and time to detection of positive cultures using color test and Lӧwenstein Jensen culture.

METHODS

A comparative cross-sectional study was conducted at University of Gondar Hospital. A total of 200 sputum samples were collected from TB patients and processed for direct smear microscopy and cultures.

RESULTS

Sixty-five percent were found positive on both methods and 4 (2%) were positive on LJ culture and negative on the color plate. The median time for detection of MTB growth was significantly shorter using color plate test (Median 12 days) than LJ culture (Median 21 days) (P < 0.0001). The overall sensitivity and specificity of the color test compared to LJ culture were 97% (95% CI: 93-99) and 100% (95% CI: 94-100), respectively.

CONCLUSIONS

The color plate test for micro-colonies allows early and accurate MTB diagnosis in a median time of 12 days. This rapid method could be an option for diagnosis of pulmonary TB in resource limited settings.

Current trends and intricacies in the management of HIV-associated pulmonary tuberculosis

Human immunodeficiency virus (HIV) epidemic has undoubtedly increased the incidence of tuberculosis (TB) globally, posing a formidable global health challenge affecting 1.2 million cases. Pulmonary TB assumes utmost significance in the programmatic perspective as it is readily transmissible as well as easily diagnosable. HIV complicates every aspect of pulmonary tuberculosis from diagnosis to treatment, demanding a different approach to effectively tackle both the diseases. In order to control these converging epidemics, it is important to diagnose early, initiate appropriate therapy for both infections, prevent transmission and administer preventive therapy. Liquid culture methods and nucleic acid amplification tests for TB confirmation have replaced conventional solid media, enabling quicker and simultaneous detection of mycobacterium and its drug sensitivity profile Unique problems posed by the syndemic include Acquired rifampicin resistance, drug-drug interactions, malabsorption of drugs and immune reconstitution inflammatory syndrome or paradoxical reaction that complicate dual and concomitant therapy. While the antiretroviral therapy armamentarium is constantly reinforced by discovery of newer and safer drugs every year, only a few drugs for anti tuberculosis treatment have successfully emerged. These include bedaquiline, delamanid and pretomanid which have entered phase III B trials and are also available through conditional access national programmes. The current guidelines by WHO to start Antiretroviral therapy irrespective of CD4+ cell count based on benefits cited by recent trials could go a long way in preventing various complications caused by the deadly duo. This review provides a consolidated gist of the advancements, concepts and updates that have emerged in the management of HIV-associated pulmonary TB for maximizing efficacy, offering latest solutions for tackling drug-drug interactions and remedial measures for immune reconstitution inflammatory syndrome.

Rapid culture-based diagnosis of pulmonary tuberculosis in developed and developing countries

Culturing Mycobacterium tuberculosis remains the gold standard for the laboratory diagnosis of pulmonary tuberculosis, with 9 million new cases and 1.5 million deaths mainly in developing countries. Reviewing data reported over 20 years yields a state-of-the-art procedure for the routine culture of M. tuberculosis in both developed and developing countries. Useful specimens include sputum, induced sputum, and stools collected in quaternary ammonium preservative-containing sterile cans. The usefulness of other non-invasive specimens remains to be evaluated. Specimens can be collected in a diagnosis kit also containing sampling materials, instructions, laboratory requests, and informed consent. Automated direct LED fluorescence microscopy after auramine staining precedes inoculation of an egg-lecithin-containing culture solid medium under microaerophilic atmosphere, inverted microscope reading or scanning video-imaging detection of colonies and colonies identification by recent molecular methods. This procedure should result in a diagnosis of pulmonary tuberculosis as fast as 5 days. It may be implemented in both developed and developing countries with automated steps replaceable by manual steps depending on local resources.

A comparison of two different culture methods for use in the diagnosis of pulmonary tuberculosis

OBJECTIVE

Tuberculosis (TB) continues to be a significant health problem worldwide. Pulmonary TB is a contagious disease. To control the spread of TB, the disease must be diagnosed early and treated effectively.

MATERIALS AND METHODS

In this study, we determined the rates and periods of TB bacterial reproduction using the Lowenstein-Jensen (LJ) and the Mycobacterium Growth Indicator Tube (MGIT) culture systems in respiratory specimens obtained from 105 suspected TB cases that applied to our service.

RESULTS

Using either the LJ or MGIT method, the reproduction rates of TB cultures from 91 positively diagnosed cases were determined to be 69.2% and 92.3% (p=0.116), respectively. The reproduction period for these same cultures was determined to be 29.7±10.0 days and 12.1±6.1 days (p<0.0001), respectively. The culture positivity rate determined using both the LJ and MGIT methods together was found to be significantly higher than the rate determined using either LJ or MGIT separately (p<0.0001).

CONCLUSION

For the early diagnosis of pulmonary tuberculosis, which is essential for controlling the spread of TB, the routine use of the MGIT system, which is a rapid, automated and non-radiometric method, combined with the LJ method would effectively increase the diagnosis rate in order to control tuberculosis outbreaks.

Comparative performance of Thin Layer Agar and Löwenstein-Jensen culture for diagnosis of tuberculosis

Sputum smear microscopy for the diagnosis of tuberculosis (TB) is cheap and simple but its sensitivity is low. Culture on Löwenstein-Jensen (LJ) is more sensitive but it takes a long time to yield results. Thin-Layer Agar (TLA) culture was suggested as an equally sensitive and faster alternative. We evaluated the performance of TLA for diagnosing TB in Jogjakarta, Indonesia. People with suspected TB presenting from July 2010 to July 2011 to two chest clinics of the National TB Control Programme network of Jogjakarta were eligible for inclusion. A sputum sample was sent to the Gadjah Mada University microbiology laboratory for concentration, smearing, Ziehl-Neelsen staining and culture on LJ and TLA. Sensitivity of cultures was evaluated against a composite reference standard (any positive culture). Time to detection of Mycobacteria was recorded. Out of 1414 samples, 164 (12%) were smear positive, 99 (7%) were scanty and 1151 (81%) were negative. On TLA and LJ respectively, 168 (12%) and 149 (11%) samples were positive, 72 (5%) and 32 (2%) were contaminated (κ = 0.64; 95% CI 0.59-0.69, p <0.01). Using the reference standard, 196 (14%) TB cases were identified. The sensitivity of TLA was 0.86 (95% CI 0.80-0.90), significantly higher (p 0.03) than for LJ (0.76; 95% CI 0.69-0.81). The median time to detection in days was significantly shorter (p <0.01) for TLA (12; 95% CI 11-13) than for LJ (44; 95% CI 43-45). TLA is a rapid and sensitive method for the diagnosis of TB. Implementation studies to evaluate the cost-effectiveness and impact of its introduction into programmatic settings are urgently needed.

Characterization of Mycobacterium tuberculosis isolated from cancer patients with suspected tuberculosis infection in Egypt: identification, prevalence, risk factors and resistance pattern

Data are sparse on Mycobacterium tuberculosis infection among patients with cancer in Egypt. We sought to detect the presence of tuberculosis (TB) disease among patients with malignant conditions and suspected TB and to study the main risk factors. Also, we compared different diagnostic procedures and detected the antimicrobial susceptibility of M. tuberculosis isolates against rifampin and isoniazid. One hundred patients were included in this study, all of them had malignant conditions and were suspected by the clinicians of having TB. Identification of M. tuberculosis in different specimens was performed by smear microscopy, followed by Lowenstein-Jensen medium and Mycobacterium growth indicator tube (MGIT) cultures and artus(®) real-time PCR. In addition, an indirect MGIT anti-TB susceptibility test was carried out against rifampin and isoniazid. A total of 76% of studied cases were found to be TB positive. The frequencies of TB-positive cases in the bronchogenic, haematological and solid tumour malignancy groups were 21%, 25% and 30%, respectively. Significant differences between pulmonary and extrapulmonary TB in different malignancy groups were recorded. Real-time PCR showed the highest overall diagnostic efficiency. Multidrug-resistance of M. tuberculosis to both rifampin and isoniazid was detected in 28.6% of examined isolates. Infection in cancer patients with TB was significantly more often recorded among elderly patients and those suffering from poverty. Pulmonary TB is more common than extrapulmonary TB in patients with malignancy. Real-time PCR is the most accurate and rapid method for TB diagnosis. MGIT-rifampin resistance may be used as a reliable marker for detection of multidrug-resistant TB. Diagnosis and instituting treatment course for active or latent TB infection are crucial before starting anticancer therapy.

Advances in the Diagnosis, Treatment and Control of HIV Associated Tuberculosis

There has been an increase in the number of published tuberculosis/HIV (TB/HIV) research findings in recent times. The potential impact of these findings on routine care has informed this review which aims at discussing current concepts and practices underpinning TB/HIV care and control. Any HIV infected person with a cough of any duration is currently considered a TB suspect. Preliminary results also show that the diagnostic yield of same day sputum samples (front loading) is comparable to two-day samples. Laboratory diagnosis is shifting from Ziehl-Neelsen (ZN) smear microscopy and solid culture to fluorescent microscopy, molecular tests and liquid culture. Concomitant TB/HIV therapy improves survival and WHO has recommended ART for all TB/HIV patients. Unless CD4 cell counts are less than 50 cells/µl, ART can be deferred until end of intensive phase. Evidence of survival benefit at high CD4 cell counts is still lacking. New TB drugs and treatment shortening studies are underway but so far no new TB drugs has been added to the current arsenal and treatment duration still remains six months or more. WHO has recommended the 31s (intensified TB case finding, isoniazid prophylaxis and infection control) for TB/HIV control in addition to effective therapy, Antiretroviral therapy and TB vaccines. There has been immense progress in TB/HIV research, however optimal management of HIV-Infected TB patients, will require further research and appropriate translation of emerging evidence to policy and practice.

Diagnosis & treatment of tuberculosis in HIV co-infected patients

Human immunodeficiency virus (HIV) associated tuberculosis (TB) remains a major global public health challenge, with an estimated 1.4 million patients worldwide. Co-infection with HIV leads to challenges in both the diagnosis and treatment of tuberculosis. Further, there has been an increase in rates of drug resistant tuberculosis, including multi-drug (MDR-TB) and extensively drug resistant TB (XDRTB), which are difficult to treat and contribute to increased mortality. Because of the poor performance of sputum smear microscopy in HIV-infected patients, newer diagnostic tests are urgently required that are not only sensitive and specific but easy to use in remote and resource-constrained settings. The treatment of co-infected patients requires antituberculosis and antiretroviral drugs to be administered concomitantly; challenges include pill burden and patient compliance, drug interactions, overlapping toxic effects, and immune reconstitution inflammatory syndrome. Also important questions about the duration and schedule of anti-TB drug regimens and timing of antiretroviral therapy remain unanswered. From a programmatic point of view, screening of all HIV-infected persons for TB and vice-versa requires good co-ordination and communication between the TB and AIDS control programmes. Linkage of co-infected patients to antiretroviral treatment centres is critical if early mortality is to be prevented. We present here an overview of existing diagnostic strategies, new tests in the pipeline and recommendations for treatment of patients with HIV-TB dual infection.

HIV and tuberculosis in India

The global impact of the converging dual epidemics of tuberculosis (TB) and human immunodeficiency virus (HIV) is one of the major public health challenges of our time. The World Health Organization (WHO) reports 9.2 million new cases of TB in 2006 of whom 7.7% were HIV-infected. Tuberculosis is the most common opportunistic infection in HIV-infected patients as well as the leading cause of death. Further,there has been an increase in rates of drug resistant tuberculosis, including multi-drug (MDRTB) and extensively drug resistant TB (XDRTB), which are difficult to treat and contribute to increased mortality. The diagnosis of TB is based on sputum smear microscopy, a 100-year old technique and chest radiography,which has problems of specificity. Extra-pulmonary, disseminated and sputum smear negative manifestations are more common in patients with advanced immunosuppression. Newer diagnostic tests are urgently required that are not only sensitive and specific but easy to use in remote and resourc-poor settings. Treatment of HIV-TB co-infection is complex and associated with high pill burden, overlapping drug toxicities,risk of immune reconstitution inflammatory syndrome (IRIS) and challenges related to adherence. From a programmatic point of view, screening of all HIV-infected persons for tuberculosis and vice-versa will help identify co-infected patients who require treatment for both infections. This requires good coordination and communication between the TB and AIDS control programs, in India.

Prevalence of mycobacteremia in Indian HIV-infected patients detected by the MB/BacT automated culture system

The use of automated blood cultures system, such as MB/BacT, has provided a novel opportunity for laboratories to diagnose mycobacteremia in HIV-infected patients. However, no such study has been carried out in India so far. This prospective study was conducted on 52 HIV-positive patients with suspected tuberculosis who were referred to our tertiary care hospital in New Delhi. In these patients, the prevalence of mycobacteremia was evaluated using the MB/BacT automated culture system (bioMérieux, France). Twenty-seven HIV-negative but suspected tuberculosis patients were also included for comparison. Mycobacteria could be isolated from sputa or fecal samples of 20 HIV-positive patients (38.4%), and in nine (45%) of these 20 cases, mycobacteria could also be isolated simultaneously from their blood specimens. In the remaining 32 patients, all relevant non-hematological clinical samples remained negative for mycobacteria, but the pathogen could be detected from the blood samples of seven (21.87%) of these 32 patients. Therefore, only 25 (48%) clinically suspected patients remained negative in both Löwenstein-Jensen (L-J) and MB/BacT culture methods, and 12 of these responded to anti-tubercular treatment, while in the rest either non-tubercular diagnosis was established or they were lost to follow-up. The study revealed that low CD+(4) counts and poor or no reactivity to purified protein derivative (PPD) were the best clinical predictors for the occurrence of mycobacteremia in HIV-positive patients. Of the 16 isolates from blood, 13 were diagnosed as Mycobacterium tuberculosis and one each were identified as M. avium, M. kansasii, and a mixed infection of M. tuberculosis and M. avium complex. The prevalence rate of mycobacteremia was significantly low (11.1%) in HIV-negative patients. In conclusion, this study showed that blood culture could be an important adjunct investigation for confirming the clinical diagnosis of tuberculosis in HIV-positive patients.

Facing the crisis: improving the diagnosis of tuberculosis in the HIV era

Although the human immunodeficiency virus (HIV) infection pandemic has had a catastrophic impact on tuberculosis (TB) control efforts, especially in sub-Saharan Africa, most of the fundamental concepts reflected in the directly observed treatment, short course (DOTS) strategy still hold true in the HIV era. What has changed, and dramatically, is the importance of speedy and accurate TB diagnosis and the difficulty of achieving this. The disproportionate amount of smear-negative disease in sub-Saharan Africa, which shoulders two-thirds of the global burden of HIV infection and acquired immunodeficiency syndrome, has greatly complicated TB case detection and disease control. Now, 15 years after TB rates began to soar in countries where HIV infection is prevalent, we have learned that the conventional approach -- passively waiting for patients with advanced symptomatic disease to make their way to microscopy centers for diagnosis -- has disastrous consequences. Without better diagnostic tools for TB and effective strategies for their implementation, transmission will not be interrupted, mortality will not be checked, and TB will not be controlled in areas where HIV infection is prevalent. Fortunately, a number of technical opportunities exist for the creation of improved diagnostic tests. Developing and exploiting such tests to support TB control in HIV-infected populations is an urgent priority. A substantial public sector effort is under way to work in partnership with the biotechnology industry to accelerate progress toward that goal. In this article, we will define the need for better TB tests and describe technologies being developed to meet that need.