Resistance to Second-Line Anti-TB Drugs in Cambodia: A Phenotypic and Genetic Study

Pre-extensively drug-resistant tuberculosis among pulmonary multidrug-resistant tuberculosis patients in Eastern Nigeria

Background

Pre-extensively drug-resistant tuberculosis (Pre-XDR-TB), an emerging form of drug-resistant tuberculosis, is challenging efforts at tuberculosis control, leading to treatment failure among multidrug-resistant tuberculosis (MDR-TB) patients and progression to extensively drug-resistant tuberculosis (XDR-TB). We determined the rate of Pre-XDR-TB among multidrug-resistant patients in Southeast, Nigeria.

Methods

A prospective laboratory-based study was carried out at the South East Zonal Tuberculosis Reference Laboratory from January 2021 to December 2021. Second-line drug (SLD) resistance was performed on 225 sputum samples of multidrug-resistant patients prior to treatment initiation using GenoType MTBDRsl genotypic drug susceptibility testing (DST) method.

Results

The rate of Pre-XDR-TB among 225 MDR-TB cases was 3.1%. Fluoroquinolone-resistant Pre-XDR-TB was observed (100%) in previously treated tuberculosis cases. Only one (0.4%) case showed resistance to both fluoroquinolone (FQ) and one second-line injectable drug (XDR-TB). The extensively drug-resistant case observed was a de-novo resistance. Exactly 0.9% of the multidrug-resistant cases showed resistance to second-line injectables.

Conclusion

The prevalence of Pre-XDR-TB among MDR-TB cases was high. There is need for rapid detection of Pre-XDR-TB among MDR-TB cases before treatment initiation.

Pre-extensively drug-resistant tuberculosis among multidrug-resistant tuberculosis patients in Ethiopia: a laboratory-based surveillance study

Background

The rise of drug-resistant tuberculosis (DR-TB) has presented a substantial challenge to the national tuberculosis (TB) control program. Understanding the epidemiology of pre-extensively drug-resistant tuberculosis (pre-XDR-TB) could help clinicians to adapt MDR-TB treatment regimens at an earlier stage. This study aimed to assess second-line anti-TB drug resistance among MDR-TB patients in Ethiopia using routine laboratory-based data.

Methods

Laboratory-based cross-sectional data were collected from the national TB reference laboratory and seven regional tuberculosis culture laboratories in Ethiopia from July 2019 to March 2022. The required data, such as drug-susceptibility testing (DST) results and sociodemographics, were collected on a structured checklist from laboratory registration books and electronic databases. Data were entered into a Microsoft Excel spreadsheet and analyzed using SPSS version 23. Descriptive statistics were performed to show the distribution and magnitude of drug resistance.

Results

Second-line drugs (SLDs) susceptibility testing was performed for 644 MDR isolates, of which 19 (3%) were found to be pre-XDR-TB cases. Of the total MDR-TB isolates, 19 (3%) were resistant to at least one fluoroquinolone drug, while 11 (1.7%) were resistant to at least one injectable second-line drug. Of the 644 MDR-TB isolates, 1.9% (5/261) pre-XDR were from new MDR-TB cases, while 3.7% (14/383) were from previously treated MDR-TB patients. The most frequently identified mutations, based on MTBDRsl results, were in codon A90V of the gyrA gene (77.3%) and A1401G of the rrs gene (45.5%).

Conclusion

The overall prevalence of pre-XDR-TB in Ethiopia is considerable. The majority of SLD resistance mutations were in the gyrA gene at position A90V. Modern, rapid DST is necessary to enable identification of pre-XDR-TB and XDR-TB in supporting proper regimen administration for patients.

Synthesis and in vitro studies for structure-based design of novel chalcones as antitubercular agents targeting InhA

Background: The authors aimed to estimate the therapeutic potential of novel chalcones against tuberculosis. Methods: 11 synthesized compounds were tested for in vitro antimycobacterial activity against Mycobacterium tuberculosis (H37RV; American Type Culture Collection number: 27294) using the microplate alamarBlue assay. Molecular docking and pharmacokinetic parameter analyses were then performed. Results: The most potent compounds, (2E)-1-(4-bromophenyl) (2E)-1-(2-nitrophenyl) prop-2-en-1-one, -3-(2-nitrophenyl) prop-2-en-1-one (4-bromophenyl) (2E)-1-(3-phenoxyphenyl)prop-2-en-1-one, 3-(phenoxyphenyl)prop-2-en-1-one (4-bromophenyl) prop-2-en-1-one and (2E)-1-(4-bromophenyl)-3-(5-chloro-2-hydroxyphenyl)-prop-2-en-1-one, showed in vitro activity, with a minimum inhibitory concentration (MIC) of 6.25 μg/ml. Conclusion: Compounds LSD2, LSD12, LSD13 and LSD15 showed strong in vitro antimycobacterial activity at a concentration of 6.25 μg/ml.

Molecular characterisation of second-line drug resistance among drug resistant tuberculosis patients tested in Uganda: a two and a half-year's review

BACKGROUND

Second-line drug resistance (SLD) among tuberculosis (TB) patients is a serious emerging challenge towards global control of the disease. We characterized SLD-resistance conferring-mutations among TB patients with rifampicin and/or isoniazid (RIF and/or INH) drug-resistance tested at the Uganda National TB Reference Laboratory (NTRL) between June 2017 and December 2019.

METHODS

This was a descriptive cross-sectional secondary data analysis of 20,508 M. tuberculosis isolates of new and previously treated patients' resistant to RIF and/or INH. DNA strips with valid results to characterise the SLD resistance using the commercial Line Probe Assay Genotype MTBDRsl Version 2.0 Assay (Hain Life Science, Nehren, Germany) were reviewed. Data were analysed with STATAv15 using cross-tabulation for frequency and proportions of known resistance-conferring mutations to injectable agents (IA) and fluoroquinolones (FQ).

RESULTS

Among the eligible participants, 12,993/20,508 (63.4%) were male and median (IQR) age 32 (24-43). A total of 576/20,508 (2.8%) of the M. tuberculosis isolates from participants had resistance to RIF and/or INH. These included; 102/576 (17.7%) single drug-resistant and 474/576 (82.3%) multidrug-resistant (MDR) strains. Only 102 patients had test results for FQ of whom 70/102 (68.6%) and 01/102 (0.98%) had resistance-conferring mutations in the gyrA locus and gyrB locus respectively. Among patients with FQ resistance, gyrAD94G 42.6% (30.0-55.9) and gyrA A90V 41.1% (28.6-54.3) mutations were most observed. Only one mutation, E540D was detected in the gyrB locus. A total of 26 patients had resistance-conferring mutations to IA in whom, 20/26 77.0% (56.4-91.0) had A1401G mutation in the rrs gene locus.

CONCLUSIONS

Our study reveals a high proportion of mutations known to confer high-level fluoroquinolone drug-resistance among patients with rifampicin and/or isoniazid drug resistance. Utilizing routinely generated laboratory data from existing molecular diagnostic methods may aid real-time surveillance of emerging tuberculosis drug-resistance in resource-limited settings.

Novel mutations detected from drug resistant Mycobacterium tuberculosis isolated from North East of Thailand

The emergence of drug-resistant tuberculosis is a major global public health threat. Thailand is one of the top 14 countries with high tuberculosis and multi-drug resistant tuberculosis rates. Immediate detection of drug-resistant tuberculosis is necessary to reduce mortality and morbidity by effectively providing treatment to ameliorate the formation of resistant strains. Limited data exist of mutation profiles in Northeastern Thailand. Here, 65 drug-resistant Mycobacterium tuberculosis isolates were used to detect mutations by polymerase chain reaction (PCR) and DNA sequencing. In the katG gene, mutations were occurred in 47 (79.7%) among 59 isoniazid resistant samples. For rpoB gene, 31 (96.9%) were observed as mutations in 32 rifampicin resistant isolates. Of 47 katG mutation samples, 45 (95.7%) had mutations in katG315 codon and 2 (4.3%) showed novel mutations at katG365 with amino acid substitution of CCG-CGG (Pro-Arg). Moreover, out of 31 rpoB mutation isolates, the codon positions rpoB516, rpoB526, rpoB531 and rpoB533 were 3 (9.7%), 8 (25.8%), 11 (35.5%) and 1 (3.2%), respectively. Seven isolates of double point mutation were found [rpoB516, 526; 1 (3.2%) and rpoB516, 531; 6 (19.4%)]. In addition, 1 (3.2%) sample had triple point mutation at codon positions rpoB516, 526 and 531. Common and novel mutation codons of the rpoB and katG genes were generated. Although DNA sequencing showed high accuracy, conventional PCR could be applied as an initial marker for screening drug-resistant Mycobacterium tuberculosis isolates in limit resources region. Mutations reported here should be considered when developing new molecular diagnostic methods for implementation in Northeastern Thailand.