PCR diagnosis on formalin-fixed, paraffin-embedded tissues with acid-fast stain and culture negativity in chronic dialysis patients of cervico-mediastinal tuberculous lymphadenitis

Extra-pulmonary tuberculosis infection in the dialysis patients with end stage renal diseases: case reports and literature review

The diagnosis of extra-pulmonary tuberculosis (TB) seems relatively difficult due to the absence of specific symptoms and signs in patients on peritoneal dialysis or hemodialysis. We report four cases of extra-pulmonary tuberculosis on dialysis, with two cases on peritoneal dialysis and two cases on hemodialysis. The presentations, therapy, and outcomes of TB infection in these patients were reviewed. Otherwise, the English literature published in the PubMed database associating extra-pulmonary tuberculosis on dialysis over the last three decades is reviewed. A total of 61 studies containing 70 cases were included. The most common primary disease was diabetic nephropathy (22.86%, 16/70). The peritoneum (31.42%, 22/70), bone (21.42%, 15/70), and lymph node (20%, 14/70) were the most frequently infected. Single organ infection was common (90%, 63/70). Fever (58.57%, 41/70), pain (35.71%, 25/70), and enlarged lymph node (20%, 14/70) were the most common symptoms. Biopsy (67.14%, 47/70) and culture (40%, 28/70) provided most reliable methods for clear diagnosis of tuberculosis. The combined treatment of isoniazid, rifampicin, pyrazinamide, and ethambutol (44.29%, 31/70) was the most common therapy. The majority of patients improved (82.86%, 58/70); however, 12 cases got worse (17.14%), with 10 of them dying (14.29%). Physicians should be aware of the non-specific symptoms and location of infection, and consider tuberculosis in their differential diagnoses in dialysis patients presenting with symptoms such as fever, pain, and weight loss.

Comparison of smear microscopy, culture, and real-time PCR for quantitative detection of Mycobacterium tuberculosis in clinical respiratory specimens

BACKGROUND

As a rapid diagnostic technique, the real-time polymerase chain reaction (PCR) can detect Mycobacterium tuberculosis with a high sensitivity and specificity. However, further studies are needed to confirm it as a standard method. In this study, we evaluated the cyp141 gene for the detection and quantification of M. tuberculosis in respiratory specimens and compared the results with direct microscopy and culture.

METHODS

Sputum samples (n = 247) were collected from patients of the different provinces of Iran. DNA was extracted from clinical specimens and H37Rv strain. After measuring the standard strain DNA concentration by NanoDrop and using the Avogadro number, the DNA was diluted 6 times in order to obtain 1 × 10(6) to 10 template copies. A Taqman probe was designed for detection of the target in a real-time PCR using the specific primers.

RESULTS

Of 247 samples, 135 (55%) were culture-negative. Of 112 (45%) culture-positive samples, 88 were positive by both smear and culture and 24 were smear-negative but culture-positive. The real-time PCR enumerated 1.5E + 02 to 4.3E+ 03, 8.5E + 03 to 5.5E + 04, 7.2E + 04 to 1.1E + 06, and 1.2E + 06 to 8.1E + 07 M. tuberculosis cells in the specimens with smear-negative, 1-plus, 2-plus, and 3-plus codes, respectively. The overall sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the real-time PCR were 90.2% (101/112), 97.8% (132/135), 97.1%, and 92.3%, respectively.

CONCLUSIONS

The overall sensitivity and specificity, the results in comparison with those of the Xpert MTB/RIF kit, and the good correlation with molecular and phenotypic methods, show that cyp141 could be a good target for the quantification of M. tuberculosis in sputum and possibly other clinical specimens.

Detection and identification of aquatic mycobacteria in formalin-fixed, paraffin-embedded fish tissues

The isolation of mycobacteria from field samples is problematic, and isolation of the bacterium is sometimes not even attempted. The detection of mycobacteria through traditional histology using formalin-fixed, paraffin-embedded (FFPE) tissues is neither sensitive nor specific. However, detection of mycobacterial DNA from FFPE specimens, suspected of being infected with mammalian mycobacteriosis, is a routine clinical procedure. In the present study, a polymerase chain reaction (PCR)-based method was used to detect and identify mycobacteria in FFPE specimens sampled from fish suspected of being infected with fish mycobacteriosis. A total of 45 fish tissue samples, comprising of 12 tissue samples obtained from experimentally infected fish and the remainder from fish naturally infected with mycobacteria, were analysed using a PCR protocol which amplifies a fragment of the mycobacterial 65 kDa heat-shock protein (hsp65) gene. PCR-restriction enzyme analysis and/or sequencing were employed to further analyse the PCR amplicons. The PCR results were compared with those obtained by histology and culture. Mycobacterial DNA was detected in 34 of the 45 samples examined, of which 16 samples (47%) showed granulomatous reactions on histological examination. Using histology as the gold standard, no false-negative PCR results were obtained. Also, considering the presence or absence of granulomas as a diagnostic criterion, the sensitivity and specificity of PCR in 42 of the FFPE tissues were 16/16 (100%) and 8/26 (approximately 30.8%), respectively. Corresponding microbiological cultures were available for 15 cases, of which 13 were pure Mycobacterium cultures. Of these, 13 were PCR positive (100% sensitivity and 50% specificity). The PCR-based methods used here proved sensitive, specific and rapid for the detection of mycobacteria in routinely processed paraffin wax-embedded and formalin-fixed histological samples, and the results of the study suggest that this method has potential use in retrospective epidemiological studies.

Tuberculous lymphadenitis in patients undergoing continuous ambulatory peritoneal dialysis

The aim of this study was to review the clinical features of tuberculous (TB) lymphadenitis in patients undergoing continuous ambulatory peritoneal dialysis (CAPD). Nine cases of TB lymphadenitis were diagnosed among 910 patients over a period of 10 years. There were five men and four women with a mean age of 51 +/- 15.5 years. The TB lymphadenitis involved the cervical lymph nodes in six patients, supraclavicular lymph nodes in two patients and mediastinal lymph nodes in one patient. Six patients presented with clinically enlarged lymph nodes of whom four also had fever. Three other patients were incidentally found to have enlarged lymph nodes on routine chest X-ray or ultrasound examination of the neck. Diagnosis of TB lymphadenitis was made by demonstrating caseating granulomata with or without positive acid-fast bacilli on excisional lymph node biopsy. All patients were cured with standard anti-tuberculosis drugs for 12 months. No recurrence of the TB lymphadenitis was observed after a mean follow-up of 59 +/- 30 months. We conclude that TB lymphadenitis is not uncommon among patients on CAPD. A high index of suspicion is needed for early diagnosis of this condition. Prompt initiation of anti-tuberculosis treatment is associated with good prognosis.

Sensitivity of acid-fast staining for Mycobacterium tuberculosis in formalin-fixed tissue

Microscopic examination of tissue sections of mycobacterial lesions frequently results in few or no bacilli seen, even if the lesions appear active histologically. This might be due to the effects of the fixative fluid and/or organic solvent, both of which are conventionally used to make tissue sections for histopathology, on the acid-fast staining of bacteria. The present study was performed to examine how formalin and xylene lower the sensitivity of acid-fast staining for Mycobacterium tuberculosis and to clarify the meaning of the staining result in tissue sections. Microscopic observation of mycobacteria smeared on glass slides revealed that both of these agents greatly reduced the sensitivity of acid-fast staining. Moreover, the number of bacilli was calculated in 30 samples of paraffin-embedded granulomatous lesions using acid-fast microscopy and real-time polymerase chain reaction. The numbers of bacilli present that were estimated by real-time polymerase chain reaction were considerably higher than those counted with a microscope. These results suggest that the bacilli are frequently missed or underestimated with acid-fast microscopy on formalin-fixed, paraffin-embedded tissue.

Comparison of in house polymerase chain reaction with conventional techniques for the detection of Mycobacterium tuberculosis DNA in granulomatous lymphadenopathy

AIMS

To evaluate the usefulness of the devR based polymerase chain reaction (PCR) in the detection of Mycobacterium tuberculosis in lymph node aspirates and tissues of lymphadenitis and to compare PCR with conventional diagnostic techniques.

SUBJECTS AND METHODS

Coded specimens of fine needle aspirates and biopsies from 22 patients with tuberculous lymphadenitis, 14 patients with non-tubercular lymphadenitis, and nine patients with granulomatous lymphadenitis were processed and subjected to analysis by PCR, smear microscopy, M tuberculosis culture, histology, and cytology.

RESULTS

Tuberculous lymphadenitis was correctly diagnosed by PCR in 18 patients, by culture in five patients, by histology in 13 patients, and by cytology in seven patients. PCR gave two false positive results in 14 patients with non-tubercular lymphadenitis. The sensitivity of the conventional techniques was significantly higher with biopsies (17 of 22 specimens; 77%) than with fine needle aspirates (nine of 22 specimens; 41%). However, the sensitivity of PCR was not significantly higher with biopsies (68%) in comparison with fine needle aspirates (55%). The sensitivity of either biopsy PCR or fine needle aspirate PCR was not significantly different from that of either histology combined with culture or cytology combined with culture. The overall combined specificity of PCR was 86%. Mycobacterium tuberculosis DNA was detected in six of nine patients with granulomatous lymphadenitis.

CONCLUSION

PCR is the most sensitive single technique available to date for the demonstration of M tuberculosis in specimens derived from patients with a clinical suspicion of tuberculous lymphadenitis. The value of PCR lies in its use as an adjunct test in the diagnosis of tuberculous lymphadenitis, particularly in those patients where conventional methods fail. Because fine needle aspiration is not an invasive procedure, it is the procedure of choice, and PCR should be performed initially on these samples. Excisional biopsy histology and PCR should be recommended only for patients in whom fine needle aspirate PCR is negative or when there is discrepancy with the clinical impression.