Diagnostic system strengthening for drug resistant tuberculosis in Nigeria: impact and challenges.

BACKGROUND: The increasing prevalence of drug-resistant tuberculosis and the threat of extensively-drug-resistant tuberculosis in HIV hotspots have made the detection and treatment of drug-resistant tuberculosis in the sub-Saharan Africa setting a global public health priority. OBJECTIVE: We sought to examine the impact and challenges of tuberculosis diagnostic capacity development for the detection of drug-resistant tuberculosis and bio-surveillance using a modular biosafety level 3 (BSL-3) laboratory in Nigeria. METHOD: In 2010, the United States President's Emergency Plan for AIDS Relief (PEPFAR) programme, through the Institute of Human Virology at the University of Maryland in Baltimore, Maryland, United States, deployed a modular, BSL-3 laboratory to support the national tuberculosis programme in drug-resistant tuberculosis detection and bio-surveillance for effective tuberculosis prevention and control. RESULTS: From 2010 until present, sputum samples from 11 606 suspected cases in 33 states were screened for drug-resistant tuberculosis. Of those, 1500 (12.9%) had mono-resistant tuberculosis strains, and 459 (4.0%) cases had multidrug-resistant tuberculosis. Over the last four years, 133 scientists were trained in a train-the-trainer programme on advanced tuberculosis culture, drug susceptibility testing, line-probe assays and Xpert® MTB/RIF, in addition to safety operations for biosafety facilities. Power instability, running cost and seasonal dust are notable challenges to optimal performance and scale up. CONCLUSION: Movable BSL-3 containment laboratories can be deployed to improve diagnostic capacity for drug-resistant tuberculosis and bio-surveillance in settings with limited resources.

Performance of Genotype MTBDRplus in the Detection of Resistance to Rifampicin and Isoniazid Among Clinical Mycobacteria Isolates in Ilorin, Nigeria.

BACKGROUND: Performance of Genotype MTBDRplus assay against Lowenstein Jensen (LJ) proportion method of Drug Susceptibility Testing (DST) in detection of resistance among clinical mycobacteria isolates to rifampicin (RMP) and isoniazid (INH) was evaluated in Ilorin, Nigeria. METHODS: This retrospective study characterized one hundred mycobacteria isolates from pulmonary TB patients, stored on LJ medium and subcultured unto fresh LJ slants before being genotyped using MTBDRplus assay. DST was performed on the isolates against RMP, INH, Ethambutol and Streptomycin. RESULTS: Genotype MTBDRplus identified 97% and 3% of the 100 isolates as Mycobacterium tuberculosis Complex (MTBC) and Non-Tuberculous Mycobacteria (NTM) respectively. Fourteen of the isolates, (14%) were resistant to RMP while 86% were sensitive by the genotypic method. Three of these 14 RMP-resistant isolates were NTMs while 11 were MTBC. Twelve (12%) of the 100 isolates were resistant to INH. Three INH-resistant isolates were NTMs, and 9 were MTBC. Phenotypically and genotypically, the 3 NTMs were resistant to RMP and INH and ten of the 97 MTBC strains were RMP-resistant. One RMP-phenotypically-sensitive strain was genotypically resistant to RMP. Six of the MTBC isolates were resistant to both RMP and INH by both methods. Most mutations occurred in the S-531L and S315T1 codons of rpoB and KatG genes of RMP and INH, respectively. CONCLUSION: The high specificity and positive predictive values recorded by MTBDRplus in our study make it suitable for use in the programmatic management of drug-resistant TB in resource-limited settings.

Optimising Mycobacterium tuberculosis detection in resource limited settings.

OBJECTIVES: The light-emitting diode (LED) fluorescence microscopy has made acid-fast bacilli (AFB) detection faster and efficient although its optimal performance in resource-limited settings is still being studied. We assessed the optimal performances of light and fluorescence microscopy in routine conditions of a resource-limited setting and evaluated the digestion time for sputum samples for maximum yield of positive cultures. DESIGN: Cross-sectional study. SETTING: Facility-based involving samples of routine patients receiving tuberculosis treatment and care from the main tuberculosis case referral centre in northern Nigeria. PARTICIPANTS: The study included 450 sputum samples from 150 new patients with clinical diagnosis of pulmonary tuberculosis. METHODS: The 450 samples were pooled into 150 specimens, examined independently with mercury vapour lamp (FM), LED CysCope (CY) and Primo Star iLED (PiLED) fluorescence microscopies, and with the Ziehl-Neelsen (ZN) microscopy to assess the performance of each technique compared with liquid culture. The cultured specimens were decontaminated with BD Mycoprep (4% NaOH-1% NLAC and 2.9% sodium citrate) for 10, 15 and 20 min before incubation in Mycobacterium growth incubator tube (MGIT) system and growth examined for acid-fast bacilli (AFB). RESULTS: Of the 150 specimens examined by direct microscopy: 44 (29%), 60 (40%), 49 (33%) and 64 (43%) were AFB positive by ZN, FM, CY and iLED microscopy, respectively. Digestion of sputum samples for 10, 15 and 20 min yielded mycobacterial growth in 72 (48%), 81 (54%) and 68 (45%) of the digested samples, respectively, after incubation in the MGIT system. CONCLUSIONS: In routine laboratory conditions of a resource-limited setting, our study has demonstrated the superiority of fluorescence microscopy over the conventional ZN technique. Digestion of sputum samples for 15 min yielded more positive cultures.