To assess the spread of the Mycobacterium tuberculosis Beijing genotype among patients with multidrug-resistant and extensively resistant tuberculosis in Bulgaria, we genotyped 188 (72%) of 261 microbiologically confirmed resistant isolates obtained during 2007–2011. The estimated prevalence of the Beijing genotype among these patients was 3.2%.

Introduction: The transmission of drug-resistant tuberculosis is one of the greatest challenges facing the global tuberculosis control. Aim: The aim of the study was to investigate the resent transmission of rifampicin resistant tuberculosis in Bulgaria and to describe the mutations related to the antimicrobials&rsquo; resistance using whole genome sequencing. Materials and methods: As part of an ECDC funded pilot study for evaluation of the systematic use of whole genome sequencing (WGS) of Mycobacterium tuberculosis (MTB) surveillance (EUSeqMyTB), Bulgaria provided 65 rifampicin resistant isolates over a three years&rsquo; timeframe (2017-2019) representing 87.5% of the notified rifampicin resistant cases. Drug resistance prediction and relatedness analysis of the resistant isolates was performed in collaboration with San Raffaele Scientific Institute, Milan, Italy. Results: Almost all of the isolates were identified as Euro-American lineage (96.9%); 18.5% of the isolates were found to be resistant to fluoroquinolones, but no mutations conferring resistance to bedaquiline or linezolid could be identified. Less than half (43.3%) of the isolates were clustered (<5 SNPs distance) into a total of seven national SNP-based clusters, while a total of six isolates were found to be part of different cross-border clusters. All clustered cases originated from Bulgaria. Conclusions: WGS has proven to be a reliable tool for surveillance and tracing of recent transmission of tuberculosis and has the potential for resistance prediction for most of the antituberculosis drugs.

This study aimed to describe the first two microbiologically confirmed cases of cutaneous and soft tissue Mycobacterium marinum infection in Bulgaria. The isolation of the Nontuberculous Mycobacteria (NTM) strains and their species identification was performed at NRL TB, NCIPD using specific media and cultivation conditions, and PCR based Line Probe Assay (LPA) from the positive cultures. The two patients had closely related jobs to fishes and water reservoirs and both of them had a similar clinical manifestation of M. mari&shy;num infection known as &ldquo;swimming pool&rdquo; or &ldquo;fish tank&rdquo; granuloma. The prolonged specific treatment with at least two-drug combina&shy;tion of rifampicin plus ethambutol and some complications were a big challenge for clinicians as well as the patients.

Background. Isoniazid is a common drug in the treatment regimens for TB infection. Monoisoniazid resistance reduces the probability of a successful treatment outcome and increases the risk of acquiring additional drug resistance. Material and methods. For the period 2015-2016 a total of 36 TB cases were confirmed in NRL TB, Sofia, as isoniazid-monoresistant Mycobacterium tuberculosis complex. Minimum inhibitory concentration testing for isoniazid was conducted with BАСТЕС MGIT 960 System in the following concentrations of the drug: 0.1 μg/ml, 0.15μg/ml, 0.2μg/ml, 0.3μg/ml, 0.4μg/ml. Molecular testing was performed with GenoType ® MTBDRplus in order to detect the most common mutations associated with resistance to isoniazid. Results. Only 25% of the tested M. tuberculosis complex isolates with phenotypic isoniazid monoresistance had the S315T1 mutation in katG; all isolates were with MIC over 0.4 μg/ml. C15T in the promoter region of inhA was detected in 22.22% of cases and only 1 of them showed MIC below 0.4 μg/ml. No mutations were detected in nearly half of the cases (n=19, 52.78%) and most of these isolates were with lower MIC values (n=12). Conclusion. The rapid testing with GenoType ® MTBDRplus can be used as a screening procedure indicating whether further examination of isoniazid MIC is relevant in resistant M. tuberculosis and whether higher doses could be considered.

The members of Mycobacterium avium complex (MAC) are opportunistic microorganisms, common in the environment (soil and water) and cause infections in birds, mammals and humans. The objective of the present study was to determine the prevalence of MAC representatives among suspected for tuberculosis patients in Bulgaria over an eight-year period – from 2010 to 2017. The exact epidemiology of pulmonary non-tuberculous mycobacterial (NTM) disease was difficult to determine because unlike cases of infection with M. tuberculosis complex, notification of NTM and MAC in particular, is not mandatory in terms of Ordinance 21 of the Ministry of Health (1) and there is no any accurate information about their prevalence in Bulgaria. The survey was conducted in the National Reference Laboratory of Tuberculosis at the National Centre of Infectious and Parasitic Diseases. MAC was identified using phenotypic methods, biochemical features and molecular genetic assay (LPA). A total of 596 NTM strains were identified during the study period and 16.8% (n=100) of them were MAC. In EU countries, MAC representatives areprevalent among NTM isolates, but in Bulgaria they are significantly less in number.