Next-generation sequencing of drug resistant Mycobacterium tuberculosis clinical isolates in low-incidence countriesNataša Toplak
, Eva Sodja
, Minka Kovač
, Simon Koren
, Marija Žolnir-Dovč
, Biljana Ilievska Poposka
, Sara Truden
Abstract: Drug resistant tuberculosis (TB), especially multidrug (MDR) and extensively drug-resistant (XDR) TB, is still a serious problem in global TB control. Slovenia and North Macedonia are low-incidence countries with TB incidence rates of 5.4 and 10.4 in 2017, respectively. In both countries, the percentage of drug resistant TB is very low with sporadic cases of MDR-TB. However, global burden of drug-resistant TB continues to increase imposing huge impact on public health systems and strongly stimulating the detection of gene variants related with drug resistance in TB. Next-generation sequencing (NGS) can provide comprehensive analysis of gene variants linked to drug resistance in Mycobacterium tuberculosis. Therefore, the aim of our study was to examine the feasibility of a full-length gene analysis for the drug resistance related genes (inhA, katG, rpoB, embB) using Ion Torrent technology and to compare the NGS results with those obtained from conventional phenotypic drug susceptibility testing (DST) in TB isolates. Between 1996 and 2017, we retrospectively selected 56 TB strains from our National mycobacterial culture collection. Of those, 33 TB isolates from Slovenian patients were isolated from various clinical samples and subjected to phenotypic DST testing in Laboratory for Mycobacteria (University Clinic Golnik, Slovenia). The remaining 23 TB isolates were isolated from Macedonian patients and sent to our laboratory for assistance in phenotypic DST testing. TB strains included were either mono-, poly- or multidrug resistant. For control purposes, we also randomly selected five TB strains susceptible to first-line anti-TB drugs. High concordance between genetic (Ion Torrent technology) and standard phenotypic DST testing for isoniazid, rifampicin and ethambutol was observed, with percent of agreement of 77%, 93.4% and 93.3%, sensitivities of 68.2%, 100% and 100%, and specificities of 100%, 80% and 88.2%, respectively. In conclusion, the genotypic DST using Ion Torrent semiconductor NGS successfully predicted drug resistance with significant shortening of time needed to obtain the resistance profiles from several weeks to just a few days.
Keywords: drug resistant tuberculosis, next-generation sequencing, low-incidence countries, phenotypic drug susceptibility testing
DiRROS - Published: 24.07.2020; Views: 1019; Downloads: 465
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Next-generation sequencing to characterize pyrazinamide resistance in Mycobacterium tuberculosis isolates from two Balkan countriesEva Sodja
, Simon Koren
, Nataša Toplak
, Sara Truden
, Marija Žolnir-Dovč
Abstract: Objectives. Next-generation sequencing (NGS) provide a comprehensive analysis of the genetic alterations that are most commonly linked with pyrazinamide (PZA) resistance. There are no studies reporting molecular background of PZA resistance in TB isolates from Balkan Peninsula. We aimed to examine the feasibility of full-length analysis of a gene linked with PZA resistance, pncA, using Ion Torrent technology in comparison to phenotypic BACTEC MGIT 960 DST in clinical TB isolates from two countries of the Balkan Peninsula. Methods. Between 1996 and 2017, we retrospectively selected 61 TB isolates. To identify gene variants related to drug resistance in genomic DNA extracted from TB isolates, AmpliSeq libraries were generated automatically using the AmpliSeq™ Kit for Chef DL8 and the Ion AmpliSeq TB Research Panel. Result.s Of all 61 TB isolates included, 56 TB were phenotypically resistant to any antibiotic. Among them, 38/56 (67.9%) TB isolates were phenotypically resistant to pyrazinamide and pncA mutations were detected in 33/38 cases (86.8%). A mutation in the pncA promoter region was the most prevalent genetic alteration, detected in eight TB isolates. Comparison of NGS to conventional BACTEC MGIT 960 DST revealed very strong agreement (90.2%) between the two methods in identifying PZA resistance, with high sensitivity (89.5%) and specificity (95.7%) for NGS. Conclusions. Detection of PZA resistance using NGS seems to be a valuable tool for surveillance of TB drug resistance also in the Balkan Peninsula, with great potential to provide useful information at least one weak earlier than is possible with phenotypic DST.
Keywords: tuberculosis, Mycobacterium tuberculosis, high-throughput nucleotide sequencing, pyrazinamide, microbial sensitivity tests, next-generation sequencing, drug susceptibility testing, Slovenia, Republic of North Macedonia
DiRROS - Published: 10.01.2022; Views: 33; Downloads: 27
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Functional complement analysis can predict genetic testing results and long-term outcome in patients with complement deficienciesŠtefan Blazina
, Maruša Debeljak
, Mitja Košnik
, Saša Simčič
, Sanja Stopinšek
, Gašper Markelj
, Nataša Toplak
, Peter Kopač
, Breda Zakotnik
, Marko Pokorn
, Tadej Avčin
Abstract: Background: Prevalence of complement deficiencies (CDs) is markedly higher in Slovenian primary immunodeficiency (PID) registry in comparison to other national and international PID registries.
Objective: The purposes of our study were to confirm CD and define complete and partial CD in registered patients in Slovenia, to evaluate frequency of clinical manifestations, and to assess the risk for characteristic infections separately for subjects with complete and partial CD.
Methods: CD was confirmed with genetic analyses in patients with C2 deficiency, C8 deficiency, and hereditary angioedema or with repeated functional complement studies and measurement of complement components in other CD. Results of genetic studies (homozygous subjects vs. heterozygous carriers) and complement functional studies were analyzed to define complete (complement below the level of heterozygous carriers) and partial CD (complement above the level of homozygous patients). Presence of characteristic infections was assessed separately for complete and partial CD.
Results: Genetic analyses confirmed markedly higher prevalence of CD in Slovenian PID registry (26% of all PID) than in other national and international PID registries (0.5–6% of all PID). Complement functional studies and complement component concentrations reliably distinguished between homozygous and heterozygous CD carriers. Subjects with partial CD had higher risk for characteristic infections than previously reported.
Conclusion: Results of our study imply under-recognition of CD worldwide. Complement functional studies and complement component concentrations reliably predicted risk for characteristic infections in patients with complete or partial CD. Vaccination against encapsulated bacteria should be advocated also for subjects with partial CD and not limited to complete CD.
Keywords: complement deficiency, primary immunodeficiency, laboratory analysis, genetic analysis, clinical manifestations
DiRROS - Published: 12.11.2020; Views: 625; Downloads: 250
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