Abstract
Mycobacterium kansasii is an emerging non-tuberculous mycobacterial (NTM) pathogen capable of causing severe lung disease. Of the seven currently recognized M. kansasii genotypes (I-VII), genotypes I and II are most prevalent and have been associated with human disease, whereas the other five (III-VII) genotypes are predominantly of environmental origin and are believed to be non-pathogenic. Subtyping of M. kansasii serves as a valuable tool to guide clinicians in pursuing diagnosis and to initiate the proper timely treatment. Most of the previous rapid diagnostic tests for mycobacteria employing the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) technology focused on species-level identification. The purpose of this study was to establish MALDI-TOF MS reference spectra database for discrimination of M. kansasii at the genotype level. A panel of 32 strains, representatives of M. kansasii genotypes I-VI were selected, whole cell proteins extracted and measured with MALDI-TOF MS. A unique main spectra (MSP) library was created using MALDI Biotyper Compass Explorer software. The spectra reproducibility was assessed by computing composite correlation index and MSPs cross-matching. One hundred clinical M. kansasii isolates used for testing of the database resulted in 90% identification at genus-level, 7% identification at species-level and 2% identification was below the threshold of log score value 1.7, of which all were correct at genotype level. One strain could not be identified. On the other hand, 37% of strains were identified at species level, 40% at genus level and 23% was not identified with the manufacturer's database. The MALDI-TOF MS was proven a rapid and robust tool to detect and differentiate between M. kansasii genotypes. It is concluded that MALDI-TOF MS has a potential to be incorporated into the routine diagnostic workflow of M. kansasii and possibly other NTM species.
Highlights
Mycobacterium kansasii is one of the leading causative agents of pulmonary and extrapulmonary infections due to nontuberculous mycobacteria (NTM)
MALDI-TOF Matrix-assisted laser desorption ionizationtime-of-flight mass spectrometry (MS) profiling has been successfully employed in various commercial software packages allowing the identification of a wide array of Mycobacterium species, including M. kansasii
The discrimination of different M. kansasii genotypes is useful for the clinical categorization of M. kansasii infection, it has never been attempted by MALDI-TOF analysis (Pignone et al, 2006; El Khechine et al, 2011; Saleeb et al, 2011; BaladaLlasat et al, 2013; Chen et al, 2013; Machen et al, 2013; Mather et al, 2014; Mediavilla-Gradolph et al, 2015; RodriguezSanchez et al, 2015; Wilen et al, 2015; Ceyssens et al, 2017; Leyer et al, 2017)
Summary
Mycobacterium kansasii is one of the leading causative agents of pulmonary and extrapulmonary infections due to nontuberculous mycobacteria (NTM). Pulmonary diseases caused by M. kansasii tend to cluster in specific geographical areas, such as central Europe or metropolitan centers of London, Brasilia, and Johannesburg (Hoefsloot et al, 2013). In most of the countries there is no obligation of registration of such cases, the true incidence of M. kansasii disease is largely unknown. The estimated incidence of infections due to this pathogen, reported in the general population, fall within the range of 0.3–1.5 cases per 100,000 (Santin et al, 2004; Moore et al, 2010; Namkoong et al, 2016)
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