PCR detection of mycobacteraemia in tanzanian patients with extrapulmonary tuberculosis

Detection of Apparent Cell-free M. tuberculosis DNA from Plasma

New diagnostics are needed to improve clinicians’ ability to detect tuberculosis (TB) disease in key populations such as children and persons living with HIV and to rapidly detect drug resistance. Circulating cell-free DNA (ccfDNA) in plasma is a diagnostic target in new obstetric and oncologic applications, but its utility for diagnosing TB is not known. Here we show that Mycobacterium tuberculosis complex DNA can be detected in plasma of persons with sputum smear-positive TB, even in the absence of mycobacteremia. Among 40 participants with bacteriologically-confirmed smear-positive TB disease who had plasma tested by quantitative PCR (qPCR), 18/40 (45%) had a positive result on at least one triplicate reaction. Our results suggest that plasma DNA may be a useful target for improving clinicians’ ability to diagnose TB. We anticipate these findings to be the starting point for optimized methods of TB ccfDNA testing and sequence-based diagnostic applications such as molecular detection of drug resistance.

Limited value of whole blood Xpert(®) MTB/RIF for diagnosing tuberculosis in children

OBJECTIVES

We evaluated the ability of the Xpert(®) MTB/RIF assay to detect Mycobacterium tuberculosis in whole blood of children with tuberculosis in tuberculosis endemic settings with high rates of HIV infection.

METHODS

From June 2011 to September 2012 we prospectively enrolled children with symptoms or signs suggestive of tuberculosis at three research centres in Tanzania and Uganda. After clinical assessment, respiratory specimens were collected for microscopy and culture, as well as whole blood for Xpert(®) MTB/RIF. Children were classified according to standardised case definitions.

RESULTS

A total of 232 children were evaluated; 14 (6.0%) had culture-confirmed tuberculosis. The Xpert(®) MTB/RIF assay detected M. tuberculosis in 5/232 (2.2%) blood samples with 1 (0.4%) error reading and presumably 1 (0.4%) false-positive result. The sensitivity of the assay in children with culture-confirmed (1/14) versus no tuberculosis (1/117) was 7.1% (95% CI, 1.3-31.5). Three of the five Xpert(®) MTB/RIF positive patients had negative cultures, but were classified as probable tuberculosis cases. Assay sensitivity against a composite reference standard (culture-confirmed, highly probable or probable tuberculosis) was 5.4% (95% CI, 2.1-13.1).

CONCLUSION

Whole blood Xpert(®) MTB/RIF demonstrated very poor sensitivity, although it may enhance the diagnostic yield in select cases, with culture-negative tuberculosis.

Evaluation of Xpert MTB/RIF for detection of tuberculosis from blood samples of HIV-infected adults confirms Mycobacterium tuberculosis bacteremia as an indicator of poor prognosis

Tuberculosis (TB) remains a leading cause of death among HIV-infected adults, in part because of delayed diagnosis and therefore delayed initiation of treatment. Recently, the Gene-Xpert platform, a rapid, PCR-based diagnostic platform, has been validated for the diagnosis of TB with sputum. We have evaluated the Xpert MTB/RIF assay for the diagnosis of Mycobacterium tuberculosis bacteremia and investigated its impact on clinical outcomes. Consecutive HIV-infected adults with fever and cough presenting to Queen Elizabeth Central Hospital, Blantyre, Malawi, were recruited and followed up for 2 months. At presentation, three sputum samples were examined by smear, culture, and Xpert MTB/RIF assay for the presence of M. tuberculosis and blood was drawn for PCR with Xpert, for mycobacterial culture (Myco/F Lytic), and for aerobic culture. One hundred four patients were recruited, and 44 (43%) were sputum culture positive for M. tuberculosis. Ten were Xpert blood positive, for a sensitivity of 21% and a specificity of 100%. The 2-week mortality rate was significantly higher among patients who were Xpert blood positive than among those who were negative (40% versus 3%; multivariate odds ratio [OR] for death if positive, 44; 95% confidence interval [CI], 3 to 662). This effect persisted on assessment of the mortality rate at 2 months (40% versus 11%; OR, 5.6; 95% CI, 1.3 to 24.6). When screening uncomplicated patients presenting with a productive cough for pulmonary TB, Xpert blood offers no diagnostic advantage over sputum testing. Despite this, Xpert blood positivity is highly predictive of early death and this test rapidly identifies a group of patients in urgent need of initiation of treatment.

Fever of unknown origin caused by tuberculosis

Tuberculosis is an important cause of fever of unknown origin. Travel, age, dialysis, diabetes, birth in a country with a high prevalence of tuberculosis, and immunoincompetence are among the most salient risks. Associated physical findings, radiologic evaluation, and hematologic and endocrinologic abnormalities may provide clues to the diagnosis. Both noninvasive and invasive diagnostic modalities are reviewed. Because diagnosis may be elusive, therapeutic and diagnostic trials of antituberculous therapy should be considered in all patients with fever of unknown origin who defy diagnosis.

Mycobacterium tuberculosis Bacteremia in HIV-negative Patients

BACKGROUND/PURPOSE

Limited information exists about the epidemiologic characteristics of HIV-negative patients with Mycobacterium tuberculosis bacteremia (MTB).

METHODS

We retrospectively surveyed tuberculosis (TB) cases reported at National Taiwan University Hospital between 1997 and 2003. Demographic data, underlying diseases or conditions, clinical, microbiologic and radiologic findings and therapy were collected. Long-term outcome was evaluated at 1 year after initiation of anti-TB agents.

RESULTS

During the study period the incidence of MTB bacteremia in HIV-negative patients and HIV-positive patients were 0.024 and 6.2 per 1000 discharges, respectively (p<0.01). All 11 HIV-negative patients were males and eight (73%) were more than 50 years old. The most common underlying diseases/conditions were immunosuppressive therapy (64%) and heart disease (55%). Fever (80%), lymphopenia (75%) and pulmonary symptoms (58%) were the most common presentations. Ten patients were septic, two had septic shock and two had acute respiratory distress syndrome on admission. The median interval between admission and initiation of therapy for those who were cured was 6 days. Six (55%) died of TB and/or their underlying diseases. Of the six patients who died, the median survival after collection of positive blood culture was 19 days for three treated patients and 7 days for three untreated patients (p=0.01).

CONCLUSION

This case series demonstrates the wide spectrum of the initial presentation of HIV-negative patients with MTB bacteremia. The case fatality rate was high and was likely due to immunocompromised status and no anti-TB treatment prior to death. A high index of suspicion for TB and blood culture for MTB provides an additional simple and noninvasive diagnostic method to detect disseminated TB in endemic areas.

Peritoneal tuberculosis mimicking advanced ovarian cancer: a retrospective review of 22 cases

OBJECTIVE

To evaluate the clinical, laboratory and diagnostic features in women with peritoneal tuberculosis that resembled advanced ovarian malignancy.

METHODS

A retrospective review of women with peritoneal tuberculosis who were managed at TCSB Ankara Etlik Maternity and Women's Health Teaching and Research Hospital from July 1992 to November 2004 was undertaken.

RESULTS

Among the 1,826 women treated during the study period, 22 women with peritoneal tuberculosis (1.2%) were identified. The mean age was 36.9 years (range 21-68 years); the mean Ca125 level was 564.95 U/ml (3-2021 U/ml). All patients with peritoneal tuberculosis had ascites, 20 patients (90.91%) had elevated CA125 levels and 17 patients (77.27%) had detectable pelvic masses in the preoperative period. During preoperative diagnostic work-up, pulmonary tuberculosis was diagnosed and antituberculosis therapy had begun in two of 22 patients (9.09%). Among 20 patients, 11 (55%), 8 (40%) and 1 (5%) underwent exploratory laparotomy, diagnostic laparoscopy and laparoscopy converted to laparotomy due to dense pelvic adhesions, respectively. Since frozen section was not available during the surgery in 5 of 20, 3 patients (10%) underwent extended surgery. Frozen section was performed in 15 patients and revealed chronic granulomatous changes and final pathological examination confirmed the diagnosis.

CONCLUSION

Our data indicate that the majority of the cases with peritoneal tuberculosis can be diagnosed intraoperatively through the use of frozen section in conjunction with clinical features. Ascites and high levels of Ca125 do not necessarily indicate that the clinical picture is malignant in reproductive women. Laparoscopic tissue biopsy may be a fundamental tool in the management of such cases to avoid extended surgery.

The usefulness of PCR amplification of the IS6110 insertion element of M. tuberculosis complex in ascitic fluid of patients with peritoneal tuberculosis

Background: The diagnosis of tuberculous peritonitis (TP) may be difficult and elusive. The present study was designed to demonstrate the diagnostic usefulness of a nested polymerase chain reaction (PCR) assay, specific for the IS6110 insertion element of M. tuberculosis complex, in patients with ascites who were suspected of having TP in order to achieve a more timely diagnosis and treatment. Methods: Three HIV-negative patients suffering from fever and ascites were evaluated for suspected TP. Specimens were obtained from ascitic fluid, bone marrow, and peripheral blood and analyzed by both conventional methods and nested PCR for the presence of bacilli. Response to antituberculous treatment was considered as the final criterion for diagnosis of peritoneal tuberculosis. Results: All three patients had an excellent response to antituberculous therapy. Our PCR-based protocol detected M. tuberculosis complex DNA in the ascitic fluid of all patients, whereas conventional methods failed to establish the disease. Furthermore, in one patient, M. tuberculosis was also detected in both bone marrow and peripheral blood. Conclusions: PCR amplification of the IS6110 sequence of M. tuberculosis complex in ascitic fluid is a useful tool when peritoneal tuberculosis is suspected. However, its validity still needs to be established.

Amplification of IS6110 sequence for detection of Mycobacterium tuberculosis complex in HIV-negative patients with fever of unknown origin (FUO) and evidence of extrapulmonary disease

OBJECTIVES

Extrapulmonary tuberculosis (TB) constitutes the main cause of classic fever of unknown origin (FUO) in many populations. The aim of this study was to improve the diagnostic field of the disease using a nested polymerase chain reaction (PCR) assay, specific for the IS6110 insertion element of Mycobacterium tuberculosis complex, in order to achieve a more timely diagnosis and treatment.

SETTING

Twenty-four, HIV-negative classic FUO patients who were admitted to the Regional Hospital of Alexandroupolis between April 1997 and July 1999.

SUBJECTS AND DESIGN

The above patients were considered as putative extrapulmonary TB after 3 weeks of in-patient investigation and underwent exhaustive examination for diagnosis of the disease. For this purpose, specimens were obtained from peripheral blood and bone marrow from these patients, as well as from damaged tissues, and analysed by both PCR and conventional methods. Anti-tuberculous treatment was initiated in 16 out of 24 patients and the response to this regimen was considered as the final criterion for diagnosis of tuberculosis.

RESULTS

Extrapulmonary TB was established in 11 patients. The PCR-based methodology, when applied to samples derived from bone marrow aspirations and suspected damaged tissues, was able to diagnose 10 of them, whereas the conventional methods were able to detect only two.

CONCLUSIONS

Our results confirm the diagnostic value of molecular detection of M. tuberculosis in cases of FUO, thus supporting the application of PCR in tissue samples suspected of bacillus infection. Furthermore, our studies demonstrate that bone marrow aspiration specimens constitute an alternative, easy, safe and reliable source for such PCR analysis.

Rapid diagnosis of bacteremia by universal amplification of 23S ribosomal DNA followed by hybridization to an oligonucleotide array

The rapid identification of bacteria in blood cultures and other clinical specimens is important for patient management and antimicrobial therapy. We describe a rapid (<4 h) detection and identification system that uses universal PCR primers to amplify a variable region of bacterial 23S ribosomal DNA, followed by reverse hybridization of the products to a panel of oligonucleotides. This procedure was successful in discriminating a range of bacteria in pure cultures. When this procedure was applied directly to 158 unselected positive blood culture broths on the day when growth was detected, 125 (79.7%) were correctly identified, including 4 with mixed cultures. Nine (7.2%) yielded bacteria for which no oligonucleotide targets were present in the oligonucleotide panel, and 16 culture-positive broths (10.3%) produced no PCR product. In seven of the remaining eight broths, streptococci were identified but not subsequently grown, and one isolate of Staphylococcus aureus was misidentified as a coagulase-negative staphylococcus. The accuracy, range, and discriminatory power of the assay can be continually extended by adding further oligonucleotides to the panel without significantly increasing complexity or cost.