ABSTRACT
Objective@#To establish the domestic matrix assisted laser desorption/ionisation time of flight mass spectrometry database for identification of clinical mycobacteria and evaluate its accuracy with foreign counterpart. @*Methods@#The establishment of "Chinese Pathogenic Mycobacteria Mass Spectrometry Database" : nineteen American type culture collection strains from 19 species and 183 "standardized" isolates from 42 species were selected and extracted by modified ultrasonic extraction method for spectral acquisition and database establishment based on microTyper MS. Each extract was dropped onto 12 spots and tested twice to generate 24 spectrum, then at least 20 qualified spectrum according to the standard were selected. Subsequently they were composed into one main spectra (MSP) by setting peak number maximum, peak frequency minimum and mass tolerance. Verification of database: Totally 305 mycobacteria from different regions were used for comparison of accuracy and spectral features between microTyper MS based on domestic database and imported MALDI TOF MS base on Mycobacteria Library 3.0 database. @*Results@#The database composed of 202 stains from 42 species was constructed, with an average of 4.8 in each species. The top ten were M. Kansasii(16), M. intracellulare(16), M. gordonae(16), M. fortuitum(16), M. avium(16), M. abscessus(16), M. tuberculosis(15), M. marseillense(11), M. arupense(10), M. yongongens(8). A total of 305 isolates were confirmed belonging to 22 species by sequencing. The accuracy based on this database was 99.67% (304/305), which was better than the Mycobacteria Library 3.0 database (χ2=4.06, P<0.05). @*Conclusion@#The construction of the "Chinese Pathogenic Mycobacteria Mass Spectrometry Database" meets the requirement of routine clinical application and was more accurate than its counterpart in terms of domestic comment strains.(Chin J Lab Med, 2018, 41: 519-526)
ABSTRACT
Background: Rapidly growing mycobacteria (RGM) are considered opportunistic pathogens. An increasing number of post traumatic or surgical infections are caused by these microorganisms. Aim: To determine the antimicrobial susceptibility of RGM using the E-test method. Material and methods: A total of 54 isolates of RGM was obtained from several clinical samples and selected for this study Strains were identified to the species level by phenotypic and biochemical characteristics, PCR-restriction enzyme analysis of the hsp65 gene (PRA) and sequencing of the 16S rRNA. Susceptibility was investigated by E-test to amikacin, cefoxitin, ciprofioxacin, clarithromycin, imipenem, quinupristin/dalfopristin, linezolid and tigecycline. Results: Twelve different species of RGM were identified: Mycobacterium fortuitum (23 strains), M chelonae (11), M abscessus (10), Msenegalense (2), Malvei (1), Mbrumae (1), Mmageritense (1), mucogenicum (1), M neoaurum (1), Mperegrinum (1), M septicum (1) y M smegmatis (1). All the strains were inhibited by low concentrations of amikacin and tigecycline. Susceptibility to cefoxitin, fluoroquinolones, clarithromycin, imipenem and linezolid was variable. All but two strains were resistant to quinupristin/ dalfopristin. Conclusions: Due to the uneven antimicrobial susceptibility of different species of RGM, an antimicrobial susceptibility test is mandatory for these microorganisms. The E-test method is well suited to determine minimum inhibitory concentrations.