First molecular-based anti-TB drug resistance survey in Eritrea.

BACKGROUND: In the absence of reliable data on drug-resistant TB in Eritrea, a national survey was conducted in 2018 using molecular-based methods, bypassing the need for culture.METHODS: A cross-sectional study was conducted in all 77 TB microscopy centres in the country. All 629 newly registered sputum smear-positive pulmonary TB patients were enrolled over 12 months. Sputum samples were tested using the Xpert® MTB/RIF assay and targeted next-generation sequencing (Deeplex Myc-TB) to identify resistance and explore the phylogenetics of Mycobacterium tuberculosis complex strains.RESULTS: Drug resistance profiles were obtained for 555 patients (502 new, 53 previously treated). The prevalence of rifampicin-resistant TB (RR-TB) was respectively 2.0% and 7.6% among new and previously treated cases. All RR-TB isolates that were susceptible to isoniazid displayed a phylogenetic marker conferring capreomycin resistance, confirming circulation of a previously described resistant TB sub-lineage in the Horn of Africa. Only one case of fluoroquinolone resistance was detected.CONCLUSION: The prevalence of rifampicin resistance among TB patients is encouragingly low. The scarcity of fluoroquinolone resistance bodes well for the success of the recommended all-oral treatment regimen. Surveillance based on molecular approaches enables a reliable estimation of the burden of resistance and can be used to guide appropriate treatment and care.

Characterization of Genomic Variants Associated with Resistance to Bedaquiline and Delamanid in Naive Mycobacterium tuberculosis Clinical Strains.

The role of mutations in genes associated with phenotypic resistance to bedaquiline (BDQ) and delamanid (DLM) in Mycobacterium tuberculosis complex (MTBc) strains is poorly characterized. A clear understanding of the genetic variants' role is crucial to guide the development of molecular-based drug susceptibility testing (DST). In this work, we analyzed all mutations in candidate genomic regions associated with BDQ- and DLM-resistant phenotypes using a whole-genome sequencing (WGS) data set from a collection of 4,795 MTBc clinical isolates from six countries with a high burden of tuberculosis (TB). From WGS analysis, we identified 61 and 163 unique mutations in genomic regions potentially involved in BDQ- and DLM-resistant phenotypes, respectively. Importantly, all strains were isolated from patients who likely have never been exposed to these medicines. To characterize the role of mutations, we calculated the free energy variation upon mutations in the available protein structures of Ddn (DLM), Fgd1 (DLM), and Rv0678 (BDQ) and performed MIC assays on a subset of MTBc strains carrying mutations to assess their phenotypic effect. The combination of structural and phenotypic data allowed for cataloguing the mutations clearly associated with resistance to BDQ (n = 4) and DLM (n = 35), only two of which were previously described, as well as about a hundred genetic variants without any correlation with resistance. Significantly, these results show that both BDQ and DLM resistance-related mutations are diverse and distributed across the entire region of each gene target, which is of critical importance for the development of comprehensive molecular diagnostic tools.

Sputum smear microscopy result: a predictor for drug-resistant tuberculosis?

Until countries establish capacity for continuous surveillance systems, representative surveys of tuberculosis (TB) patients continue to improve our understanding of the burden of drug-resistant TB and help ensure appropriate allocation of resources. Although the available data are limited, the current recommendation of restricting surveys to sputum smear-positive patients is justified, given the greatly simplified logistics and only limited evidence in specific settings of an association between drug resistance and sputum smear status. Nonetheless, the relationship between drug resistance and sputum smear microscopy results may vary according to the setting and population under study. With the increasing availability and use of molecular diagnostics and the drive for universal drug susceptibility testing under the World Health Organization's End TB Strategy, substantially more data on drug resistance in the whole TB patient population should become available in the near future.

The fourth national anti-tuberculosis drug resistance survey in Viet Nam.

SETTING: Viet Nam's Fourth National Anti-Tuberculosis Drug Resistance Survey was conducted in 2011. OBJECTIVE: To determine the prevalence of resistance to the four main first-line anti-tuberculosis drugs in Viet Nam. METHODS: Eighty clusters were selected using a probability proportion to size approach. Drug susceptibility testing (DST) against the four main first-line anti-tuberculosis drugs was performed. RESULTS: A total of 1629 smear-positive tuberculosis (TB) patients were eligible for culture. Of these, DST results were available for 1312 patients, including 1105 new TB cases, 195 previously treated TB cases and 12 cases with an unknown treatment history. The proportion of cases with resistance to any drug was 32.7% (95%CI 29.1-36.5) among new cases and 54.2% (95%CI 44.3-63.7) among previously treated cases. The proportion of multidrug-resistant TB (MDR-TB) cases was 4.0% (95%CI 2.5-5.4) in new cases and 23.3 (95%CI 16.7-29.9) in previously treated cases. CONCLUSIONS: The fourth drug resistance survey in Viet Nam found that the proportion of MDR-TB among new and previously treated cases was not significantly different from that in the 2005 survey. The National TB Programme should prioritise the detection and treatment of MDR-TB to reduce transmission of MDR-TB in the community.

Deletion in the gene BruAb2_0168 of Brucella abortus strains: diagnostic challenges.

Three Brucella abortus strains were isolated from joint hygromas from cows in northern Togo. Two deletions in the 5' side of the gene BruAb2_0168 were identified. As this gene is used for species identification, these deletions have consequences for diagnostic procedures. Multiple locus variable number of tandem repeat (VNTR) analysis was therefore performed for species identification. The strains showed unique VNTR profiles, providing some of the first genotypic data from West Africa. More molecular and epidemiological data are needed from the region, in order to better understand transmission patterns and develop suitable diagnostic assays.