Immunocytochemistry versus nucleic acid amplification in fine needle aspirates and tissues of extrapulmonary tuberculosis

Importance of eosinophilic structures and its correlation with acid fast bacilli in fine needle aspiration smears of tubercular lymphadenitis

BACKGROUND

The hallmark of tuberculosis in cytological smears is the presence of epithelioid cell granulomas, necrosis and AFB. In cases, where AFB not detected, diagnosis of tuberculosis can be made by ancillary tests like PCR which requires infrastructure besides being expensive. In India, where majority of population is rural-based there is an imminent need of some morphological change in cytological smears which can point towards diagnosis of tuberculosis in absence of AFB. This study was done to assess the importance of eosinophilic structures (ES) and its correlation with presence of AFB.

MATERIAL & METHODS

This was a retrospective study over a period of one year. Lymph node aspirates reported as granulomatous lymphadenitis, tubercular lesion or suppurative lesion were included. All smears for each case, stained with May Grunwald Giemsa (MGG), Hematoxylin and Eosin (H&E) and ZN stain were retrieved and rescreened for the presence of eosinophilic structure, necrosis, granulomas and AFB.

RESULTS

Our study included 256 cases. Most common age group was 21-30 years with female predominance. Cervical lymph nodes were most commonly involved. In relation to ES and AFB four cytological pictures were seen i.e ES + AFB+ (44.54%) ES + AFB- (5.46%) ES- AFB+ (14.45%) ES - AFB- (35.55%). Chi square test showed a high significant statistical association between ES and AFB(p = 0.00001).

CONCLUSION

In developing countries with very high TB prevalence like India, where new diagnostic modalities are unaffordable by rural population, presence of ES should be included as a morphological parameter in routine cytology reporting of tubercular lesions.

Aptamer Detection of Mycobaterium tuberculosis Mannose-Capped Lipoarabinomannan in Lesion Tissues for Tuberculosis Diagnosis

Tuberculosis (TB) is the leading infectious cause of mortality worldwide. However, the diagnosis of TB, especially extrapulmonary TB (EPTB) diagnosis from lesion tissues, remains a challenge. Nucleic acid aptamers are analogous to antibodies and have advantages of easier modification, high specificity, and affinity. Mannose-capped lipoarabinomannan (ManLAM) is a unique surface lipoglycan component or constantly released from mycobacterium tuberculosis (M.tb) cell wall, which makes it a perfect candidate biomarker for TB diagnosis. Our present study aims to establish M.tb ManLAM aptamer-based immunohistochemistry (IHC) method for TB diagnosis. We performed TB diagnosis using 263 formalin-fixed paraffin-embedded tissue samples including 213 TB samples (pulmonary TB (PTB) and EPTB), and 8 samples from latent TB infection (LTBI) high risk subjects, and 42 samples from other non-TB patients with ManLAM aptamer-based IHC and routine laboratory TB diagnostic methods parallelly. The sensitivity and specificity of the ManLAM aptamer-based IHC were 86.38% and 92.86%, with much higher sensitivity than those of mycobacterial culture (9.66%) and acid-fast staining (AFS) (43.01%) and comparability to Interferon-gamma Release Assay (IGRA) (84.38%) and GeneXpert (79.31%). High agreement between ManLAM based-IHC and IGRA or GeneXpert for TB diagnosis were observed. Furthermore, ManLAM aptamer-based IHC combination with other routine TB laboratory diagnostic methods significantly increased the sensitivity up to 88.64%–97.92%. As our knowledge, this is the first report about aptamer-based IHC for disease diagnosis. Thus, ManLAM aptamer-based IHC has potentials for TB diagnosis, including PTB, and EPTB, and assists the diagnosis of LTBI with high effectiveness, feasibility, and easy production.

The presence of mycobacterial antigens in sarcoidosis associated granulomas

Background: Sarcoidosis is a multi-organ disorder with unknown etiology. The role of bacteria in pathogenesis of sarcoidosis is still controversial. This study analyses new aspects of Mycobacterium Tuberculosis (MTB) presence in sarcoidosis diseases. Objectives: To find MTB in paraffin embedded tissues of sarcoidosis patients, samples of 10 sarcoidosis, 12 confirmed pulmonary tuberculosis (PTB) and 5 controls associated with granulomatous tissues were analysed. Methods: The paraffin embedded tissue specimens of the selected patients from the pathology archive of a subspecialty pulmonary hospital in IRAN were evaluated by Real Time PCR for MTB DNA using IS6110. Immunohistochemistry (IHC) method using MTB purified protein derivative (PPD) antibody was used to detect mycobacterial antigens. Results: All sarcoidosis patients had negative MTB DNA results in Real time PCR analysis. This analysis resulted in 10 (83.3%) positive cases for TB patients. The IHC analysis for MTB anti-PPD antibody showed positive diffused cytoplasmic staining for all TB patients whereas this staining was positive for 3 sarcoidosis patients (30%). Conclusion: Amplification of the IS6110 DNA sequence that is the most common target used for MTB diagnosis is not sensitive method to detect MTB in sarcoidosis granuloma. However, tissue IHC for anti-PPD antibody shows higher performance to detect MTB in sarcoidal granulomas reveals a mycobacterial signature in sarcoidosis tissue with negative IS6110 assay. This finding supports Mycobacterium tuberculosis may have an etiologic role in sarcoidosis. (Sarcoidosis Vasc Diffuse Lung Dis 2017; 34: 236-241)

Application of Laser Scanning Confocal Microscopy for the Visualization of M. tuberculosis in Lung Tissue Samples with Weak Ziehl-Neelsen Staining

One of the key requirements for the diagnosis of pulmonary tuberculosis is the identification of M. tuberculosis in tissue. In this paper, we present the advantages of specific fluorescent antibody labelling, combined with laser scanning confocal microscopy (LSCM), for the detection of M. tuberculosis in histological specimens of lung tissues. We demonstrate that the application of LSCM allows: (i) The automatic acquisition of images of the whole slice and, hence, the determination of regions for subsequent analysis; (ii) the acquisition of images of thick (20–40 μm) slices at high resolution; (iii) single bacteria identification; and (iv) 3D reconstruction, in order to obtain additional information about the distribution, size, and morphology of solitary M. tuberculosis; as well as their aggregates and colonies, in various regions of tuberculosis inflammation. LSCM allows for the discrimination of the non-specific fluorescence of bacteria-like particles and their aggregates presented in histological lung samples, from the specific fluorescence of labelled M. tuberculosis, using spectrum emission analysis. The applied method was effective in the identification of M. tuberculosis in lung histological samples with weak Ziehl–Neelsen staining. Altogether, combining immunofluorescent labelling with the application of LSCM visualization significantly increases the effectiveness of M. tuberculosis detection.

Immuno-PCR, a new technique for the serodiagnosis of tuberculosis

Rapid and accurate diagnosis of tuberculosis (TB) is essential to control the disease. The conventional microbiological tests have limitations and there is an urgent need to devise a simple, rapid and reliable point-of-care (POC) test. The failure of TB diagnostic tests based on antibody detection due to inconsistent and imprecise results has stimulated renewed interest in the development of rapid antigen detection methods. However, the World Health Organization (WHO) has emphasized to continue research for designing new antibody-based detection tests with improved accuracy. Immuno-polymerase chain reaction (I-PCR) combines the simplicity and versatility of enzyme-linked immunosorbent assay (ELISA) with the exponential amplification capacity and sensitivity of PCR thus leading to several-fold increase in sensitivity in comparison to analogous ELISA. In this review, we have described the serodiagnostic potential of I-PCR assays for an early diagnosis of TB based on the detection of potential mycobacterial antigens and circulating antibodies in body fluids of TB patients.

Development of real-time immuno-PCR for the quantitative detection of mycobacterial PstS1 in tuberculosis patients

A novel indirect real-time immuno-polymerase chain reaction (RT-I-PCR) assay, an evolution of I-PCR, was developed for the quantitative detection of Mycobacterium tuberculosis PstS1 (Rv0934) with a wide dynamic range of 10ng/mL to 1pg/mL in body fluids of tuberculosis (TB) patients, which may monitor the dynamics of disease.

Double staining of bacilli and antigen Ag85B improves the accuracy of the pathological diagnosis of pulmonary tuberculosis

BACKGROUND

A pathological examination plays an important role in the confirmation of a diagnosis of tuberculosis, especially for smear- and culture-negative cases. However, conventional Ziehl-Neelsen staining and histological tests lack sensitivity and specificity.

OBJECTIVE

To evaluate the diagnostic value of immunohistochemical staining to detect Mycobacterium tuberculosis protein Ag85B and a newly developed double staining (ZC staining) method that can simultaneously detect acid-fast bacilli and M. tuberculosis antigen in the same histological section.

METHODS

A total of 282 formalin-fixed paraffin-embedded lung tissues were identified following histological examination, including 212 cases of pulmonary tuberculosis and 70 other pulmonary diseases. Ziehl-Neelsen staining, Ag85B-immunohistochemistry and the newly developed ZC staining were performed on serial sections of all the specimens.

RESULTS

Expression patterns of Ag85B were consistent with the distribution patterns of acid-fast bacilli. The signal produced by Ag85B-immunohistochemistry was much stronger than that produced by Ziehl-Neelsen staining. The sensitivity of Ag85B-immunohistochemistry was significantly higher than that of Ziehl-Neelsen staining, 53.8% (95% CI 47.0% to 60.5%) vs 34.4% (95% CI 28.0% to 40.9%). The newly developed ZC staining, integrating advantages of both Ziehl-Neelsen staining and immunohistochemistry, further improved the rate of sensitivity up to 65.6% (95% CI 59.1% to 72.0%).

CONCLUSIONS

This new method, detecting both acid-fast bacilli and M. tuberculosis antigen, is a simple and sensitive method for the pathological diagnosis of tuberculosis and can be easily incorporated into routine tests of pathological laboratories.

Correlation of eosinophilic structures with detection of acid-fast bacilli in fine needle aspiration smears from tuberculous lymph nodes: Is eosinophilic structure the missing link in spectrum of tuberculous lesion?

Background:

Acid-fast bacilli (AFB) is not seen in all necrotic tuberculous lesions. If the subset of tuberculous lesions which yield positive result for AFB can be identified, it would save on time and manpower besides optimizing use of resources. A prospective study was undertaken to assess if presence of eosinophilic structures (ESs) in necrotic tuberculous lesions correlated with the presence of AFB.

Materials and Methods:

Patients referred for fine needle aspiration cytology for evaluation of lymphadenopathy between July 2012 and June 2013 were analyzed. The hematoxylin and eosin and May-Grünwald-Giemsa stained slides were screened for epithelioid cell granuloma, ES and necrosis and Ziehl Neelsen stained smears for AFB.

Result:

One hundred and eight tuberculous lymph nodes yielded necrotic material on aspiration. Four cytologic pictures were seen: (a) ES⁺ AFB⁺ in 58.33%, (b) ES⁺ AFB⁻ in 20.37%, (c) ES⁻ AFB⁺ in 9.26% (d) ES⁻ AFB⁻ in 12.04% cases. Overall AFB was found in 67.59% cases, out of which 58.33% correlated with the presence of ES while 9.26% were seen in smears without ES.

Conclusion:

Presence of ESs should be included in the morphological description of tuberculous lesions. In the absence of granulomas, they indicate tuberculous nature of the lesion. Presence of ES mandates a search for AFB as probability of finding AFB is high in such lesions. Significance of ES lies in their presence and not in their absence. Eosinophilic structures appear to be the missing link in the spectrum of tuberculous lesion.