Diagnostic accuracy of the Xpert® MTB/XDR assay for detection of Isoniazid and second-line antituberculosis drugs resistance at central TB reference laboratory in Tanzania.

INTRODUCTION: Early diagnosis of tuberculosis (TB) and universal access to drug-susceptibility testing (DST) are critical elements of the WHO End TB Strategy. Current rapid tests (e.g., Xpert® MTB/RIF and Ultra-assays) can detect rifampicin resistance-conferring mutations, but cannot detect resistance to Isoniazid and second-line anti-TB agents. Although Line Probe Assay is capable of detecting resistance to second-line anti-TB agents, it requires sophisticated laboratory infrastructure and advanced skills which are often not readily available in settings replete with TB. A rapid test capable of detecting Isoniazid and second-line anti-TB drug resistance is highly needed. METHODS: We conducted a diagnostic accuracy study to evaluate a new automated Xpert MTB/XDR 10-colour assay for rapid detection of Isoniazid and second-line drugs, including ethionamide, fluoroquinolones, and injectable drugs (Amikacin, Kanamycin, and Capreomycin). Positive Xpert MTB/RIF respiratory specimens were prospectively collected through routine diagnosis and surveillance of drug resistance at the Central TB Reference Laboratory in Tanzania. Specimens were tested by both Xpert XDR assay and LPA against culture-based phenotypic DST as the reference standard. FINDINGS: We analysed specimens from 151 TB patients with a mean age (SD) of 36.2 (12.7) years. The majority (n = 109, 72.2%) were males. The sensitivity for Xpert MTB/XDR was 93.5% (95% CI, 87.4-96.7); for Isoniazid, 96.6 (95% CI, 92.1-98.6); for Fluoroquinolone, 98.7% (95% Cl 94.8-99.7); for Amikacin, 96.6%; and (95% CI 92.1-98.6) for Ethionamide. Ethionamide had the lowest specificity of 50% and the highest was 100% for Fluoroquinolone. The diagnostic performance was generally comparable to that of LPA with slight variations between the two assays. The non-determinate rate (i.e., invalid M. tuberculosis complex detection) of Xpert MTB/XDR was 2·96%. CONCLUSION: The Xpert MTB/XDR demonstrated high sensitivity and specificity for detecting resistance to Isoniazid, Fluoroquinolones, and injectable agents. This assay can be used in clinical settings to facilitate rapid diagnosis of mono-isoniazid and extensively drug-resistant TB.

In-field evaluation of Xpert® HCV viral load Fingerstick assay in people who inject drugs in Tanzania.

BACKGROUND: Although novel hepatitis C virus (HCV) RNA point-of-care technology has the potential to enhance the diagnosis in resource-limited settings, very little real-world validation of their utility exists. We evaluate the performance of HCV RNA quantification using the Xpert® HCV viral load Fingerstick assay (Xpert® HCV VL Fingerstick assay) as compared to the World Health Organisation pre-qualified plasma Xpert® HCV VL assay among people who inject drugs (PWID) attending an opioid agonist therapy (OAT) clinic in Dar-es-Salaam, Tanzania. METHODS: Between December 2018 and February 2019, consecutive HCV seropositive PWID attending the OAT clinic provided paired venous and Fingerstick samples for HCV RNA quantification. These were processed onsite using the GeneXpert® platform located at the Central tuberculosis reference laboratory. RESULTS: A total of 208 out of 220 anti-HCV-positive participants recruited (94.5%) had a valid Xpert® HCV VL result available; 126 (61%; 95% CI 53.8-67.0) had detectable and quantifiable HCV RNA. About 188 (85%) participants had paired plasma and Fingerstick whole blood samples; the sensitivity and specificity for the quantification of HCV RNA levels were 99.1% and 98.7% respectively. There was an excellent correlation (R2  = .95) and concordance (mean difference 0.13 IU/mL, (95% CI -0.9 to 0.16 IU/mL) in HCV RNA levels between plasma samples and Fingerstick samples. CONCLUSION: This study found excellent performance of the Xpert® HCV VL Fingerstick assay for HCV RNA detection and quantification in an African-field setting. Its clinical utility represents an important watershed in overcoming existing challenges to HCV diagnosis, which should play a crucial role in HCV elimination in Africa.

Antibiotic Susceptibility Patterns of Bacterial Isolates from Routine Clinical Specimens from Referral Hospitals in Tanzania: A Prospective Hospital-Based Observational Study.

INTRODUCTION: Antimicrobial resistance is one of the biggest threats of modern public health. Although sub-Saharan Africa is highly burdened with infectious diseases, current data on antimicrobial resistance are sparse. METHODS: A prospective study was conducted between October 2018 and September 2019 to assess the antibiotic susceptibility patterns of clinical bacterial isolates obtained from four referral hospitals in Tanzania. We used standard media and Kirby-Bauer disc diffusion methods as per Clinical and Laboratory Standards Institute (CLSI) standards. RESULTS: We processed a total of 2620 specimens of which 388 (14.8%) were culture-positive from patients with a median (IQR) age of 28 (12-44) years. Of the positive cultures, 52.3% (203) were from females. Most collected specimens were ear pus 28.6% (111), urine 24.0% (93), wound pus 20.6% (80), stool 14.9% (58), and blood 8.3% (32). Predominant isolates were S. aureus 28.4% (110), E. coli 15.2% (59), P. aeruginosa 10.6% (41), P. mirabilis 7.0% (27), V. cholerae 01 Ogawa 6.2% (24), Klebsiella spp. 5.2% (20) and Streptococcus spp. 4.6% (18). Generally, the isolates exhibited a high level of resistance to commonly used antibiotics such as Ampicillin, Amoxicillin-Clavulanic acid, Erythromycin, Gentamicin, Tetracycline, Trimethoprim, third-generation Cephalosporins (Ceftriaxone and Ceftazidime), and reserved drugs (Clindamycin and Meropenem). S. aureus isolates were resistant to most of the antibiotics tested; 66.7% were classified as MRSA infections. CONCLUSION: Antibiotic resistance to commonly prescribed antibiotics was alarmingly high. Our findings emphasize the need for comprehensive national control programs to combat antibiotic resistance.

Evaluation of stool GeneXpert MTB/RIF for the diagnosis of pulmonary tuberculosis among presumptive patients in Tanzania.

BACKGROUND: Diagnosis of pulmonary tuberculosis remains grim, especially in resource-limited settings. Low quality of sputum, particularly among seriously ill, HIV/AIDS, and pediatric patients might result in missing the diagnosis. This study evaluated the performance of GeneXpert MTB/RIF for the detection of pulmonary tuberculosis on stool specimens as an alternative to respiratory specimens. METHODS: A cross-sectional study design was used to evaluate the performance of GeneXpert MTB/RIF to detect TB in stool specimens from presumptive TB patients. Sputum culture on Lowenstein-Jensen media was used as the gold standard. Recruitment of patients into the study was conducted in 12 selected health facilities in Tanzania. Two sputa and a stool specimen were collected from each study participant. Both sputa and stool samples were tested at their respective study sites of collection using GeneXpert, and their respective portions shipped to the Central Tuberculosis Reference Laboratory for testing by stool GeneXpert and sputum culture in the LJ media. Statistical analysis was performed using STATA software version 14.1. RESULTS: A total of 590 presumptive tuberculosis patients were enrolled in this study. Their median age was 35 years (IQR = 21-47 years). More than half (57.5%, n = 339) of the study participants, were males. Children aged below 15 years constituted 17.6% (n = 104) of the study participants. A total of 75 tuberculosis cases were detected by sputum culture. The sensitivity and specificity of Stool GeneXpert conducted at CTRL was 84% (95% CI: 81.0-87.0%), and 93.4% (CI: 98.5-99.9%) respectively. The overall sensitivity and specificity of stool GeneXpert at the peripheral laboratories was 63.0% (95% CI: 47.8-76.1) and 76.7% (95% CI: 72.1-81.4), respectively. CONCLUSION: Findings from this study suggest that stool is a potential alternative to respiratory specimen for use in routine diagnosis of tuberculosis, especially when obtaining a respiratory specimen is challenging.