Frequently Isolated Slow Growing Nontuberculous Mycobacteria from Pulmonary Samples and Evaluation of Drug Susceptibility Testing Results in a Referral Hospital in Turkey

Most of the nontuberculous mycobacteria (NTM) are opportunistic pathogenic microorganisms and free-living in nature. NTM can cause a wide range of infections. However, pulmonary NTM disease is the most frequent clinical picture. The aim of this study was to identify and evaluate drug susceptibility of slow growing NTM isolated from pulmonary samples of patients prediagnosed as tuberculosis between 2014 and 2018 in Atatürk Chest Diseases and Chest Surgery Training and Research Hospital Microbiology Laboratory by a commercial microtube dilution plaque method. A total of 435 NTM strains obtained from suspected TB patients were included in the study. After the samples were processed by homogenization and decontamination and acid-fast staining, culture in two solid media (Löwenstein-Jensen, Ogawa) and in MGIT-BACTEC960 automated system were performed. Acid-fast bacilli isolated from culture media were identified by using cart test (MPB64, Capilla TB-Neo) and polymerase chain reaction (PCR) based reverse hybridization "line probe assay (LPA)" method (GenoType MycobacteriumCM/AS, Hain Lifescience, GmbH, Germany). After DNA isolation from the culture, PCR was performed by using the primers specific for mycobacterial 23S rRNA spacer region. PCR products were then hybridized with the probes specific for Mycobacterium species on nitrocellulose strips according to the recommendations of the manufacturer and the results were evaluated. In this study, Mycobacterium avium (n= 77, 17.7%), Mycobacterium intracellulare (n= 70, 16.1%), Mycobacterium szulgai (n= 19, 4.4%), Mycobacterium kansasii (n= 10, 2.3%) ve Mycobacterium smiae (n= 9, 2.1%) were isolated as slowly growing mycobacteria from the pulmonary patients. Susceptibility testing was performed in cation-adjusted Mueller-Hinton broth (CAMH), supplemented with "oleic acid, albumin dextrose catalase" according to CLSI/ M24-A2 guideline recommendations. For the antibiotic susceptibility test, ready-to-use plaque drugs for slow-growing mycobacteria (SLOMYCO-Sensititre, TREK Diagnostic Systems Ltd, UK), were used. M.intracellulare, M.avium, M.kansasii and M.smiae isolates were found to be sensitive to clarithromycin %100, %99, %100 and %100, respectively. For M.intracellulare and M.avium isolates, moxifloxacin and linezolid sensitivity values were found to be 91%, 64% and 80%, 74% respectively. M.kansasii isolates were more sensitive than M.simiae isolates to the most of the drugs. M.kansasii isolates, were susceptible to