Drug-Resistant Tuberculosis on the Balkan Peninsula: Determination of Drug Resistance Mechanisms with Xpert MTB/XDR and Whole-Genome Sequencing Analysis.

The new molecular assay Xpert MTB/XDR (Cepheid, Sunnyvale, CA, USA) was launched in 2021 to detect Mycobacterium tuberculosis (MT) complex with mutations conferring resistance to isoniazid (INH), ethionamide (ETH), fluoroquinolone (FQ), and second-line injectable drugs (SLIDs). The aim of our study was to evaluate the performance of the Xpert MTB/XDR rapid molecular assay on rifampicin-resistant, multidrug-resistant, and pre-extensively resistant tuberculosis (TB) isolates in a clinical laboratory in the Balkan Peninsula compared to a phenotypic drug susceptibility test (pDST). Xpert MTB/XDR was used to test positive Bactec MGIT 960 (Becton, Dickinson and Co., Franklin Lakes, NJ, USA) cultures or DNA isolates. In the case of discrepant results between Xpert MTB/XDR and pDST, the usefulness of whole-genome sequencing (WGS) was emphasized. In our study, 80 MT isolates from different Balkan countries were selectively chosen from the National Mycobacterial Strain Collection in Golnik, Slovenia. Isolates were tested with the Xpert MTB/XDR assay, conventional pDST, and WGS. Xpert MTB/XDR showed high sensitivities of 91.9%, 100%, and 100% for detecting INH, FQ, and SLID resistance, respectively, compared to pDST. In contrast, low sensitivity (51.9%) for ETH resistance was achieved because isolates harbored widespread mutations across the ethA gene. The specificity of Xpert MTB/XDR was 100% for all drugs except for INH (66.7%). Further investigation with WGS revealed -57c→t mutations in the oxyR-ahpC region marked with uncertain significance, which caused the low specificity for detecting INH resistance with the new assay. Xpert MTB/XDR can be used in clinical laboratories for the rapid detection of INH, FQ, and SLID resistance. Moreover, it can be used to rule in resistance to ETH. Additional use of WGS is recommended in cases of discrepant results between pDST and Xpert MTB/XDR. Future improvements of Xpert MTB/XDR with the inclusion of additional genes may increase the usefulness of the assay. IMPORTANCE The Xpert MTB/XDR was tested on drug-resistant Mycobacterium tuberculosis complex isolates from the Balkan Peninsula. Positive Bactec MGIT 960 cultures or DNA isolates were tested as starting material. According to the results of our study with Xpert MTB/XDR, sensitivities for the detection of SLID, FQ, and INH resistance were sufficient (>90%) for the assay to be implemented into diagnostic algorithms. In our study, WGS revealed lesser-known mutations in genes conferring INH and ETH resistance, and their impact on resistance is still unknown. Mutations in the ethA gene causing resistance to ETH were scattered along structural gene without high-confidence markers for resistance. Therefore, resistance to ETH should be reported based on a combination of methods. Because the Xpert MTB/XDR assay was found to have good performance, we propose that it should be the method of choice for confirming resistance to INH, FQ, and SLID and conditionally for resistance to ETH.

Next-generation sequencing to characterise pyrazinamide resistance in Mycobacterium tuberculosis isolates from two Balkan countries.

OBJECTIVES: Next-generation sequencing (NGS) can provide a comprehensive analysis of the genetic alterations most commonly linked with pyrazinamide (PZA) resistance. However, there are no studies reporting the molecular background of PZA resistance in Mycobacterium tuberculosis (TB) isolates from the Balkan Peninsula. We aimed to examine the feasibility of full-length analysis of a gene linked with PZA resistance (pncA) using Ion Torrent technology compared with phenotypic BACTEC MGIT 960 drug susceptibility testing (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 an AmpliSeq™ Kit for Chef DL8 and Ion AmpliSeq TB Research Panel. RESULTS: Of the 61 TB isolates, 56 were phenotypically resistant to any antibiotic. Among them, 38/56 isolates (67.9%) were phenotypically resistant to pyrazinamide, and pncA mutations were detected in 34/38 cases (89.5%). A mutation in the pncA promoter region was the most prevalent genetic alteration, detected in eight TB isolates. Comparison of NGS data with conventional BACTEC MGIT 960 DST revealed very strong agreement (91.8%) between the two methods in identifying PZA resistance, with high sensitivity (89.5%) and specificity (95.7%) for NGS. CONCLUSION: Detection of PZA resistance using NGS appears to be a valuable tool for surveillance of TB drug resistance in the Balkan Peninsula, with great potential to provide useful information at least 1 weak earlier than is possible with phenotypic DST.

Subspecies-specific sequence detection for differentiation of Mycobacterium abscessus complex.

Mycobacterium abscessus complex (MABC) is a taxonomic group of rapidly growing, nontuberculous mycobacteria that are found as etiologic agents of various types of infections. They are considered as emerging human pathogens. MABC consists of 3 subspecies-M. abscessus subsp. bolletti, M. abscessus subsp. massiliense and M. abscessus subsp. abscessus. Here we present a novel method for subspecies differentiation of M. abscessus named Subspecies-Specific Sequence Detection (SSSD). This method is based on the presence of signature sequences present within the genomes of each subspecies of MABC. We tested this method against a virtual database of 1505 genome sequences of MABC. Further, we detected signature sequences of MABC in 45 microbiological samples through DNA hybridization. SSSD showed high levels of sensitivity and specificity for differentiation of subspecies of MABC, comparable to those obtained by rpoB sequence typing.

Nationwide analysis of Mycobacterium chimaera and Mycobacterium intracellulare isolates: Frequency, clinical importance, and molecular and phenotypic resistance profiles.

The burden of tuberculosis (TB) in Slovenia is low due to good ongoing preventive measures. However, analysis of data obtained from the Registry for Tuberculosis and National Reference Laboratory for Mycobacteria at University Clinic of Respiratory and Allergic Diseases Golnik from January 2000 to December 2017 revealed that the number of nontuberculous mycobacterial (NTM) isolates is increasing. A group of slowly growing NTM and a common cause of NTM disease among humans is the Mycobacterium avium complex, the taxonomy of which is rapidly changing. M. intracellulare and M. chimaera are part of the Mycobacterium avium complex, and together represent 19.6% of all isolated NTM species in Slovenia. Due to the high genotypic and phenotypic similarity between M. intracellulare and M. chimaera species, both species are difficult to differentiate. A method that can be used to successfully distinguish between M. intracellulare and M. chimaera is the molecular assay GenoType NTM-DR. Mutations in the rrl and rrs genes that are associated with macrolide and aminoglycoside resistance, respectively, can also be detected with this method. Overall, 222 clinical isolates were tested, and the nationwide study showed that 44.6% of the previously identified M. intracellulare species were actually M. chimaera. Further, this study showed that none of the tested M. intracellulare and M. chimaera isolates harboured mutations in the rrl and rrs genes. The genotyping result that no isolates were resistant to macrolides or aminoglycosides was also confirmed phenotypically with the broth microdilution method. Among isolates from the Slovenian Mycobacterial Isolates Collection all these tested strains (n = 222) were sensitive to macrolides and aminoglycosides.

Genomic Insights Into the Mycobacterium kansasii Complex: An Update.

Only very recently, has it been proposed that the hitherto existing Mycobacterium kansasii subtypes (I-VI) should be elevated, each, to a species rank. Consequently, the former M. kansasii subtypes have been denominated as Mycobacterium kansasii (former type I), Mycobacterium persicum (II), Mycobacterium pseudokansasii (III), Mycobacterium innocens (V), and Mycobacterium attenuatum (VI). The present work extends the recently published findings by using a three-pronged computational strategy, based on the alignment fraction-average nucleotide identity, genome-to-genome distance, and core-genome phylogeny, yet essentially independent and much larger sample, and thus delivers a more refined and complete picture of the M. kansasii complex. Furthermore, five canonical taxonomic markers were used, i.e., 16S rRNA, hsp65, rpoB, and tuf genes, as well as the 16S-23S rRNA intergenic spacer region (ITS). The three major methods produced highly concordant results, corroborating the view that each M. kansasii subtype does represent a distinct species. This work not only consolidates the position of five of the currently erected species, but also provides a description of the sixth one, i.e., Mycobacterium ostraviense sp. nov. to replace the former subtype IV. By showing a close genetic relatedness, a monophyletic origin, and overlapping phenotypes, our findings support the recognition of the M. kansasii complex (MKC), accommodating all M. kansasii-derived species and Mycobacterium gastri. None of the most commonly used taxonomic markers was shown to accurately distinguish all the MKC species. Likewise, no species-specific phenotypic characteristics were found allowing for species differentiation within the complex, except the non-photochromogenicity of M. gastri. To distinguish, most reliably, between the MKC species, and between M. kansasii and M. persicum in particular, whole-genome-based approaches should be applied. In the absence of clear differences in the distribution of the virulence-associated region of difference 1 genes among the M. kansasii-derived species, the pathogenic potential of each of these species can only be speculatively assessed based on their prevalence among the clinically relevant population. Large-scale molecular epidemiological studies are needed to provide a better understanding of the clinical significance and pathobiology of the MKC species. The results of the in vitro drug susceptibility profiling emphasize the priority of rifampicin administration in the treatment of MKC-induced infections, while undermining the use of ethambutol, due to a high resistance to this drug.

Prospective genotyping of Mycobacterium tuberculosis from fresh clinical samples.

Shorter time-to-result is key for improving molecular-guided epidemiological investigation of tuberculosis (TB) cases. We performed a prospective study to evaluate the use of standardized MIRU-VNTR (mycobacterial interspersed repetitive-unit-variable-number tandem-repeat) typing of Mycobacterium tuberculosis directly on 79 fresh clinical samples from 26 TB patients consecutively enrolled over a 17-month period. Overall, complete 24-locus types were obtained for 18 out of the 26 (69.2%) patients and 14 of the 16 grade 3+ and grade 2+ samples (87.5%). The degree of completion of the genotypes obtained significantly correlated with smear microscopy grade both for 26 first samples (p = 0.0003) and for 53 follow-up samples (p = 0.002). For 20 of the 26 patients for whom complete or even incomplete M. tuberculosis isolate genotypes were obtained, typing applied to the clinical samples allowed the same unambiguous conclusions regarding case clustering or uniqueness as those that could have been drawn based on the corresponding cultured isolates. Standard 24 locus MIRU-VNTR typing of M. tuberculosis can be applied directly to fresh clinical samples, with typeability depending on the bacterial load in the sample.

Inventory study of non-tuberculous mycobacteria in the European Union.

BACKGROUND: Since non-tuberculous mycobacteria (NTM) disease is not notifiable in most European Union (EU) and European Economic Area (EEA) countries, the epidemiological situation of the >150 NTM species is largely unknown. We aimed to collect data on the frequency of NTM detection and NTM species types in EU/EEA countries. METHODS: Officially nominated national tuberculosis reference laboratories of all EU/EEA countries were asked to provide information on: laboratory routines for detection and identification of NTM, including drug sensitivity testing (DST) methods; data on the number and type of NTM species identified; coverage and completeness of the provided data on NTM; type and number of human specimens tested for NTM; and number of specimens tested for Mycobacterium tuberculosis complex and NTM. This information was summarized and the main results are described. RESULTS: In total, 99 different NTM species were identified with M. avium, M. gordonae, M. xenopi , M. intracellulare, and M. fortuitum identified most frequently. Seven percent of the NTM species could not be identified. NTM was cultured from between 0.4-2.0% of the specimens (data from four countries). The laboratories use culturing methods optimised for M. tuberculosis complex. Identification is mainly carried out by a commercial line probe assay supplemented with sequencing. Most laboratories carried out DST for rapid growers and only at the explicit clinical request for slow growers. CONCLUSION: It is likely that the prevalence of NTM is underestimated because diagnostic procedures are not optimized specifically for NTM and isolates may not be referred to the national reference laboratory for identification. Due to the diagnostic challenges and the need to establish the clinical relevance of NTM, we recommend that countries should concentrate detection and identification in only few laboratories.

One year nationwide evaluation of 24-locus MIRU-VNTR genotyping on Slovenian Mycobacterium tuberculosis isolates.

BACKGROUND: Slovenia is one of the few countries where IS6110 RFLP is applied for genotyping M. tuberculosis at a nationwide level, which has been in effect since 2000. Based on S6110 RFLP clustering, typical risk factors and routes of M. tuberculosis transmission were identified, such as alcohol abuse, homelessness, and bars. However, IS6110 RFLP typing suffers from important limitations including a long wait for results, which reduces the potential benefit of molecular-guided tuberculosis (TB) control. PCR-based 24-locus MIRU-VNTR typing combined with spoligotyping has recently emerged as a potential alternative for faster, large-scale genotyping of M. tuberculosis. METHODS: We compared these genotyping methods for analyzing 196 Slovenian Mycobacterium tuberculosis isolates representing 97.5% of all culture-positive cases included in the Slovenian TB Registry in 2008. RESULTS: IS6110 RFLP and 24-locus MIRU-VNTR typing combined with spoligotyping identified 157 and 155 distinct profiles, 135 and 125 unique isolates, and 61 and 71 clustered isolates grouped into 22 and 29 clusters, respectively. The discriminatory indexes were very close, at 0.9963 and 0.9965, respectively. The majority of the molecular clusters defined by either of the two methods were identical, including in the few cases for which epidemiological links were available. The differences frequently consisted of single-band changes in IS6170-RFLP profiles subdividing a MIRU-VNTR/spoligotype-based cluster. CONCLUSIONS: Our one-year nationwide study showed that the results of 24-locus MIRU-VNTR typing combined with spoligotyping reached a high level of concordance with those obtained from IS6110 RFLP typing.

The First Report of Mycobacterium celatum Isolation from Domestic Pig (Sus scrofa domestica) and Roe Deer (Capreolus capreolus) and an Overview of Human Infections in Slovenia.

Mycobacterium celatum, a slowly growing potentially pathogenic mycobacterium first described in humans, is regarded as an uncommon cause of human infection, though capable of inducing invasive disease in immunocompromised hosts. According to some reports, a serious disease due to M. celatum may also occur in individuals with no apparent immunodeficiency. In animals, an M. celatum-related disease has been described in three cases only: twice in a domestic ferret (Mustela putorius furo) and once in a white-tailed trogon (Trogon viridis). In this paper, we report the first detection of M. celatum in a domestic pig (Sus scrofa domestica) and roe deer (Capreolus capreolus). A nation-wide overview of human M. celatum infections recorded in Slovenia between 2000 and 2010 is also given. Pulmonary disease due to M. celatum was recognized in one patient with a history of a preexisting lung disease.

Delayed diagnosis of Mycobacterium marinum infection: A case report and review of the literature.

Mycobacterium marinum infection is the most common atypical skin mycobacterial infection of increasing importance. It results from skin injury and contact with contaminated aquarium water, fish, or shellfish; it is only rarely related to swimming pool sources nowadays. Diagnosis should be confirmed by isolation and identification of the organism; however, this gold standard is difficult to achieve in practice. Therefore, the diagnosis is primarily based on clinical examination, histopathology, and response to therapy. Awareness of this infection is still low and diagnosis often delayed, as presented in this case of a young immunocompetent patient with M. marinum infection of a chronic course. The reasons for the delay in diagnosis are discussed and current diagnostic and treatment recommendations are reviewed.

IS1245 RFLP-based genotyping study of Mycobacterium avium subsp. hominissuis isolates from pigs and humans.

Mycobacterium avium subsp. hominissuis, ubiquitous environmental mycobacterium, is an opportunistic pathogen that is regularly isolated from pigs and humans in Slovenia. Genetic diversity of 114 isolates from pigs (n = 57) and humans (n = 57), identified by means of bacteriology, DNA-RNA hybridization techniques, IS901 PCR and IS1245 PCR, was investigated in this study, using IS1245 restriction fragment length polymorphism (RFLP) analysis. Identical IS1245 RFLP profiles were found in isolates from pigs, isolates from humans and isolates from both origins. The proportion of clustered isolates varied as it depended on the similarity level (100% and 75%) chosen for the cluster limits. Using IS1245 RFLP, it was possible to detect monoclonal, polyclonal and recent infections and to monitor the genetic variability of the strains from individual patients. Our findings indicate the environment as the source of infection for both pigs and humans. The questions about the possibility of intra- and inter-species transmission of infection remain to be answered.

Transmission of Mycobacterium tuberculosis from human to cattle.

We describe the first transmission of Mycobacterium tuberculosis from human to cattle confirmed by molecular typing of isolates involved in the transmission. IS6110-based restriction fragment length polymorphism analysis showed that the isolates from the cattle and farm worker who suffered from pulmonary tuberculosis 1 year prior to this case were the same strains.

Molecular fingerprinting of Mycobacterium bovis subsp. caprae isolates from central Europe.

To study the dissemination of Mycobacterium bovis subsp. caprae, 79 European isolates from cattle, humans, and other hosts were examined by spoligotyping and IS6110 restriction fragment length polymorphism (RFLP) analysis. Among a total of 11 different spoligotypes identified, type C1 proved to be predominant (n = 62). Five of the spoligotypes are described for the first time. A total of 43 different RFLP types were identified, thus allowing further differentiation for epidemiological tracking. Isolates from a series of outbreaks in one village proved to be of the same spoligotype and of identical or closely related RFLP types.

Molecular epidemiology of tuberculosis in Slovenia: results of a one-year (2001) nation-wide study.

Slovenia is a small Central European country with a population of 1.99 million and an incidence of tuberculosis (TB) of 18.6 per 100,000 inhabitants in 2001. In a prospective nation-wide, 1-y DNA fingerprinting study, the genetic diversity of 99.7% of all Mycobacterium tuberculosis isolates obtained from Slovenian patients with culture-verified TB in 2001 were assessed using a standardized IS6110 restriction fragment length polymorphism (RFLP) method. Among 306 M. tuberculosis isolates, 228 different IS6110 RFLP patterns were found. The number of IS6110 copies varied from 2 to 16 (9.2 copies per isolate on average). Only 2 isolates (0.7%) with less than 5 IS6110 copies were identified. Clustered M. tuberculosis isolates were detected in 116 (37.9%) patients. The degree of recent transmission in the 1-y period was 25%. The clustering rate decreased with age from 46.4% (age group under 35 y) to 19.5% (age group above 65 y). A history of alcohol abuse and homelessness was found to be associated with clustering of TB cases. In conclusion, a high clustering frequency was identified among Slovenian TB patients. The study increased our understanding of important risk factors and routes of TB transmission in Slovenia.