Comparison of BacT/ALERT 3D, Lowenstein-Jensen medium and Middlebrook 7H10/7H11 biplate for recovering mycobacteria from clinical specimens

Study of HLA-G gene polymorphism and serum level of soluble HLA-G in patients infected with Mycobacterium tuberculosis

Tuberculosis affects about one-third of the world population. The incidence of the disease differs significantly among populations living under almost similar conditions, indicating the role of genetic factors. The present study aimed to appraise the impact of HLA-G gene polymorphisms and soluble HLA-G on the susceptibility to pulmonary tuberculosis. 48 patients with pulmonary tuberculosis and other 42 age- and sex-matched healthy individuals were included in the study. Both groups evaluated two gene polymorphisms in the HLA-G gene and soluble HLA-G protein. The frequency of Del/Del genotype of rs66554220 (14-bp Ins/Del) polymorphism in patients was 8.33% which was higher than that of controls (2.38%) with a significant difference (crude OR= 9.26, 95%CI=1.06-80.93, p=0.044). Such association remained significant after adjusting for confounding factors, including smoking, family history, socioeconomic status and residence (adjusted OR= 11.83, 95%CI=2.77-50.51, p= 0.01). The median serum level of soluble HLA-G in patients was 34.0 ng/ml (range 6.18-74.25 ng/ml), which was greater than that of controls (median 20 ng/ml, range 312-71.98 ng/ml) with a significant difference. We can conclude that The Del/Del genotype of rs66554220 (14-bp Ins/Del) polymorphism is an independent risk factor for pulmonary tuberculosis in the Iraqi population Keywords: Mycobacterium tuberculosis, HLA-G gene, single nucleotide polymorphism

An electrochemical biosensor for the detection of Mycobacterium tuberculosis DNA from sputum and urine samples

Tuberculosis (TB) is a major global public health problem with high mortality and morbidity. In low-middle income countries (LMIC) a large number of respiratory symptomatic cases that require TB screening per year demands more accurate, fast and affordable testing for TB diagnostics. Sputum smear is the initial screening test in LMICs, however, its sensitivity is limited in patients with low sputum bacilli load. The same limitation is observed in the currently available molecular tests. We designed, standardized and evaluated an electrochemical biosensor that detects the highly specific DNA insertion element 6110 (IS6110). A PCR amplified DNA product is hybridized on the surface of the working electrode built on FTO-Glass with immobilized specific DNA probes, after which cyclic voltammetry is performed with an Ag/AgCl reference electrode and a platinum counter electrode. The response of the sensor was measured by the ratio (cathodic peak current of the hybridized sensor) / (cathodic peak current of the non-hybridized sensor). We tested the biosensor, using positive hybridization control sequences, genomic DNA extracted from M. tuberculosis strains and sputum of TB patients, and extracted DNA from the urine of healthy controls spiked with M. tuberculosis DNA. This biosensor was effective for the detection of M. tuberculosis DNA with a detection limit of 16 fM in sputum sample and 1 fM in spiked urine samples. The low cost and the relatively brief duration of the assay make this an important TB screening tool in the fight against tuberculosis.

Needle Aspiration and Cytology for Suspected Osteoarticular Tuberculosis in Children

Introduction: Early diagnosis of osteoarticular tuberculosis (OATB) is essential to prevent significant functional disability. There is no single test for diagnosis. Despite an array of investigations available, definitive diagnosis at early stage before starting antitubercular drugs is still a challenge. Materials and Methods: A cross sectional study was carried out between February 2016 and October 2017. All children less than 18 years of age with suspected osteoarticular tuberculosis were included. The cases were subjected to simple needle aspiration from whichever site was accessible. Multiple sample aspirations were done at site of involvement. Smears were prepared from the aspirated material.

Results: Ziehl-Neelsen staining for Acid Fast Bacilli (AFB) showed deep pink red rods under light microscopy. Features suggestive of tuberculosis can be seen by May-Grünwald-Giemsa (MGG) staining. Auramine-O staining method of detecting AFB under fluorescent microscope shows the bacilli as greenish yellow slender curved rods in dark background. Fluorescent microscopy has higher sensitivity and comparable specificity. In our study, microbiological confirmation of OATB could be done in 100% cases where the lesion could be accessed for aspiration. The molecular techniques are relatively more expensive and not available everywhere.

Conclusion: Meticulous search for AFB in a well stained smear using three different staining methods provides a direct evidence of infection over costly imaging especially in poor patients seen in resource limited settings.

Evaluation of the efficacy of Myco/F lytic system, MGIT960 system and Lowenstein-Jensen medium for recovery of Mycobacterium tuberculosis from sterile body fluids

The diagnosis of extrapulmonary tuberculosis (EPTB) is challenging due to non-specific symptoms, invasive approach for specimen collection and most importantly, the paucibacillary status. The objective of this assay was to evaluate the efficacy of Myco/F lytic system, BACTEC Mycobacteria Growth Indicator Tube (MGIT) 960 system and Lowenstein-Jensen (L-J) medium for recovery of bacilli from sterile body fluids. 214 specimens (114 pleural fluid and 100 pus) from clinically diagnosed EPTB patients were collected and subjected to Ziehl-Neelsen (ZN) smear microscopy, L-J culture, MGIT 960 culture and Myco/F lytic culture.103 out of the 214 sterile body fluid samples yielded positive culture outcomes by any of the three methods. Among all the culture positive specimens, the recovery rate was 86.41% for Myco/F lytic, 75.73% for MGIT 960, and 42.72% for L-J medium. The mean time to positivity (TTP) was 27.06 ± 8.03 days for Myco/F lytic, 22.20 ± 7.84 days for MGIT960 and 42 ± 8.84 days for L-J medium. The rates of contamination were 6.54%, 3.74% and 2.80% for Myco/F lytic, MGIT960 and L-J medium respectively. Both Myco/F lytic and MGIT960 system were superior to L-J medium for recovery of bacilli from sterile body fluids. Myco/F lytic system was more favorable than MGIT960 regarding recovery rate and cost-effectiveness, thus can be considered as a promising alternative to MGIT960 system for diagnosing EPTB.

Microchip-based ultrafast serodiagnostic assay for tuberculosis

Access to point-of-care (POC), rapid, inexpensive, sensitive, and instrument-free tests for the diagnosis of tuberculosis (TB) remains a major challenge. Here, we report a simple and low-cost microchip-based TB ELISA (MTBE) platform for the detection of anti-mycobacterial IgG in plasma samples in less than 15 minutes. The MTBE employs a flow-less, magnet-actuated, bead-based ELISA for simultaneous detection of IgG responses against multiple mycobacterial antigens. Anti-trehalose 6,6′-dimycolate (TDM) IgG responses were the strongest predictor for differentiating active tuberculosis (ATB) from healthy controls (HC) and latent tuberculosis infections (LTBI). The TDM-based MTBE demonstrated superior sensitivity compared to sputum microscopy (72% vs. 56%) with 80% and 63% positivity among smear-positive and smear-negative confirmed ATB samples, respectively. Receiver operating characteristic analysis indicated good accuracy for differentiating ATB from HC (AUC = 0.77). Thus, TDM-based MTBE can be potentially used as a screening device for rapid diagnosis of active TB at the POC.

Dramatic reduction of culture time of Mycobacterium tuberculosis

Mycobacterium tuberculosis culture, a critical technique for routine diagnosis of tuberculosis, takes more than two weeks. Here, step-by-step improvements in the protocol including a new medium, microaerophlic atmosphere or ascorbic-acid supplement and autofluorescence detection dramatically shortened this delay. In the best case, primary culture and rifampicin susceptibility testing were achieved in 72 hours when specimens were inoculated directly on the medium supplemented by antibiotic at the beginning of the culture.

Tuberculous lymphadenitis in Northern Ethiopia: in a public health and microbiological perspectives

Background

The actual burden and causative agent of tuberculous lymphadenitis (TBLN) cases is not well known due to lack of strong surveillance system and diagnostic facilities in Ethiopia. This study was conducted to determine the prevalence of TBLN, its causative agent and risk factors for acquiring this infection.

Methods

A cross-sectional study was conducted from April to May 2012 at four main hospitals and one diagnostic clinic located in northern Ethiopia. Fine needle aspirates (FNAs) from TBLN suspects were taken for acid fast bacilli (AFB) microscopy, culture and molecular typing.

Results

Among 437 aspirates, culture yielded AFB in 226 (51.7%) of cases. Sixty one culture negative cases (30.5% of 200 cases) were positive by Xpert MTB/RIF test. Moreover, a rifampicin resistant AFB was detected from culture negative cases. The overall prevalence of FNAs positive TBLN cases was 65.8 %. The BacT/AlerT 3D system proved to be a more rapid method with higher recovery rate than Lowenstein-Jensen (L-J) and/or Gottsacker media (P<0.0001). Molecular typing identified all culture positive isolates as M.tuberculosis. The main risk factors for TBLN were pediatric age (OR 2.8, 95% CI, 1.09- 7.05) and cough (OR 2, 95%CI, 1.09-3.7).

Conclusions

The results of this study revealed a high prevalence of TBLN in the study sites and that pediatric age and cough are key predictors of the disease. TBLN is an important public health problem that needs to be addressed in the area. It is important to note that MDR strains of TB could be involved and aetiological confirmation and drug sensitivity testing of TBLN isolates should be expanded. Further studies on the M.tuberculosis lineages, circulating strains and transmission dynamics, are recommended.

Pneumonia pathogen detection and microbial interactions in polymicrobial episodes

Recent reports show that microbial communities associated with respiratory infections, such as pneumonia and cystic fibrosis, are more complex than expected. Most of these communities are polymicrobial and might comprise microorganisms originating from several diverse biological and ecological sources. Moreover, unexpected bacteria in the etiology of these respiratory infections have been increasingly identified. These findings were established with the use of efficient microbiological diagnostic tools, particularly molecular tools based on common gene amplification, followed by cloning and sequencing approaches, which facilitated the identification of the polymicrobial flora. Similarly, recent investigations reported that microbial interactions might exist between species in polymicrobial communities, including typical pneumonia pathogens, such as Pseudomonas aeruginosa and Candida albicans. Here, we review recent tools for microbial diagnosis, in particular, of intensive care unit pneumonia and the reported interactions between microbial species that have primarily been identified in the etiology of these infections.

Comparison of the Lowenstein-Jensen Medium, the Middlebrook 7H10 Medium and MB/BacT for the Isolation of Mycobacterium Tuberculosis (MTB) from Clinical Specimens

INTRODUCTION

Tuberculosis (TB) is the most common cause of death due to a single infectious agent worldwide in adults. India alone accounts for 30% of the global tuberculosis burden. There is a need for a method of cultivation of mycobacteria that is reliable and economical and has a short turnaround time.

OBJECTIVE

The present study was attempted to assess the feasibility of using MB BACT and Middlebrook 7h10(MB7H10) as primary isolation media for mycobacteria. They were compared with the LJ medium, which was the gold standard.

MATERIALS AND METHODS

Various clinical specimens from a total of 236 clinically suspected cases of TB were studied. All the samples were decontaminated by using the modified Petroff's method. Each sample was subjected to ZN staining and it was simultaneously inoculated onto the LJ medium, the MB7H10 medium and MB BACT. The growth from the cultures were confirmed by ZN staining and they were speciated by using biochemical reactions.

RESULTS

Out of the 236 samples which were screened, 116 isolates were obtained. All the 116 were isolated from MB BACT, 82 were isolated from the LJ medium and 62 were isolated from MB7H10. 82 isolates were obtained from MB BACT and the LJ medium, 62 were obtained from MB7H10 and MB BACT, 58 were isolated from LJ and MB7H10 and 58 were isolated from LJ medium, MB7H10 and MB bact. Neither the L J medium nor the Middlebrook 7h 10 medium could isolate mycobacteria exclusively. It showed that the combination of media did not prove to be superior over the use of MB BACT alone. The average isolation time of L J, the MB7H10 medium and MB BACT was 30.81 days, 31.06 days and 18.70 days.

INTERPRETATION AND CONCLUSION

MB BACT is a better medium as compared to the L J medium and the MB7H10 medium, both in terms of the number of isolates and the isolation rate. The MB BACT method proved to be a very speedy method and it could isolate mycobacteria 7-10 days earlier as compared to the L J medium and the Middlebrook 7 H10 medium.

Clinical and laboratory aspects of the diagnosis and management of cutaneous and subcutaneous infections caused by rapidly growing mycobacteria

Rapidly growing mycobacteria (RGM) are known to cause pulmonary, extra-pulmonary, systemic/disseminated, and cutaneous and subcutaneous infections. The erroneous detection of RGM that is based solely on microscopy, solid and liquid cultures, Bactec systems, and species-specific polymerase chain reaction (PCR) may produce misleading results. Thus, inappropriate therapeutic measures may be used in dermatologic settings, leading to increased numbers of skin deformity cases or recurrent infections. Molecular tools such as the sequence analyses of 16S rRNA, rpoB and hsp65 or PCR restriction enzyme analyses, and the alternate gene sequencing of the superoxide dismutase (SOD) gene, dnaJ, the 16S-23S rRNA internal transcribed spacers (ITS), secA, recA1, dnaK, and the 32-kDa protein gene have shown promising results in the detection of RGM species. PCR restriction enzyme analyses (PRA) work better than conventional methods at identifying species that are closely related. Recently introduced molecular tools such as matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), pyrosequencing, DNA chip technology, and Beacon probes-combined PCR probes have shown comparable results in the detection of various species of RGM. Closely related RGM species (e.g., Mycobacterium fortuitum, M. chelonae, and M. abscessus) must be clearly differentiated using accurate molecular techniques because their therapeutic responses are species-specific. Hence, this paper reviews the following aspects of RGM: (i) its sources, predisposing factors, clinical manifestations, and concomitant fungal infections; (ii) the risks of misdiagnoses in the management of RGM infections in dermatological settings; (iii) the diagnoses and outcomes of treatment responses in common and uncommon infections in immunocompromised and immunocompetent patients; (iv) conventional versus current molecular methods for the detection of RGM; (v) the basic principles of a promising MALDI-TOF MS, sampling protocol for cutaneous or subcutaneous lesions and its potential for the precise differentiation of M. fortuitum, M. chelonae, and M. abscessus; and (vi) improvements in RGM infection management as described in the recent 2011 Clinical and Laboratory Standards Institute (CLSI) guidelines, including interpretation criteria of molecular methods and antimicrobial drug panels and their break points [minimum inhibitory concentrations (MICs)], which have been highlighted for the initiation of antimicrobial therapy.

A toolbox for tuberculosis diagnosis: an Indian multicentric study (2006-2008): microbiological results

BACKGROUND

The aim of this multicentric prospective study in India was to assess the value of several microbiological tools that contribute to the diagnosis of tuberculosis (TB) according to HIV status.

METHODS

Standard microbiological tools on individual specimens were analyzed.

RESULTS

Among the 807 patients with active TB, 131 were HIV-infected, 316 HIV-uninfected and 360 had HIV-unknown status. Among the 980 non-active TB subjects, 559 were at low risk and 421 were at high risk of M. tuberculosis (Mtb) exposure. Sensitivity of smear microscopy (SM) was significantly lower in HIV-infected (42.2%) than HIV-uninfected (75.9%) (p = 0.0001) and HIV-unknown pulmonary TB patients (61.4%) (p = 0.004). Specificity was 94.5% in non-TB patients and 100% in health care workers (HCW) and healthy family contacts. Automated liquid culture has significantly higher diagnostic performances than solid culture, measured by sensitivity (74.7% vs. 55.9%) (p = 0.0001) and shorter median time to detection (TTD) (12.0 vs. 34.0 days) (p = 0.0001). Specificity was 100% in HCW and cured-TB patients, but was lower in non-TB patients (89%) due to isolation of Mycobacteria other than tuberculosis (MOTT). TTD by both methods was related to AFB score. Contamination rate was low (1.4%). AccuProbe hybridization technique detected Mtb in almost all culture-positive specimens, but MOTT were found in 4.7% with a significantly higher frequency in HIV-infected (15%) than HIV-uninfected TB patients (0.5%) (p = 0.0007). Pre-test classification significantly increased the diagnostic value of all microbiological tests in pulmonary TB patients (p<0.0001) but to a lesser degree in extrapulmonary TB patients.

CONCLUSIONS

Conventional microbiological tools led to results similar to those already described in India special features for HIV-infected TB patients included lower detection by SM and culture. New microbiological assays, such as the automated liquid culture system, showed increased accuracy and speed of detection.