Evaluation of Mycobacterium tuberculosis Culture and Drug Susceptibility Test Results and the Distribution of Nontuberculosis Mycobacteria from the Clinical Specimens

Abstract

Tuberculosis (TB) continues to pose a significant public health problem worldwide. For mycobacteriology laboratories, it is important to be able to diagnose active cases and to make a differential diagnosis of non-tuberculous mycobacteria (NTM). In this study, it was aimed to retrospectively evaluate the epidemiological status of the Mycobacterium [Mycobacterium tuberculosis complex (MTC) and NTM] obtained from the clinical specimens of patients with TB suspicion, and the resistance rates of MTC isolates against anti-TB drugs. Various clinical samples of TB suspected patients sent to the Balıkesir Atatürk City Hospital Mycobacteriology Laboratory between 2011 and 2019, were included in the study. Microscopy, culture procedures, and the first-line anti-TB drug susceptibility tests were performed according to the instructions. Identification of NTM at the species level could be made during four years including 2012, 2013, 2016, and 2017. In our study, acid fast bacillus (AFB) positivity rate was 4% (1.867/47.235); the culture positivity rate for MTC was 5.1% (1.576/31.017) and 1.1% (333/31.017) for NTM. AFB positivity was detected in 837 (53.1%) of the clinical specimens isolated from MTC. In the presence of AFB positivity, it was determined that bacterial growth was significantly higher in both liquid culture systems (LCS) and Lowenstein-Jensen (LJ) media. The isolation rate of MTC isolates from LCS was determined as 95.3% (1.503/1.576) and the isolation rate from LJ was 67.4% (1.063/1.576). The bacterial growth rate was found to be significantly higher in LCS. The average bacterial growth time (ABGT) of AFB negative samples were 21.79 ± 9.96 days; 13.74 ± 8.13 days for AFB positive samples, and ABGT was significantly shorter in the case of AFB positivity. As the severity of AFB positivity increased, ABGT wasshortened which was statistically significant. While 783 (78%) of the isolates were found to be sensitive to all the tested drugs, 221 (22%) were found to be resistant to at least one drug. Eleven of them (1%) were identified as multidrug resistant-TB (MDR-TB) isolates. In our study, 16 different species were identified among 112 typed NTM isolates. Mycobacterium gordonae (25.0%), Mycobacterium avium complex (17.0%) (Mycobacterium intracellulare-11.6%, Mycobacterium avium-5.4%) and Mycobacterium abscessus (13.3%) were the most frequently isolated NTM species. As a result, nine-year results of the mycobacteriology laboratory in our region were analyzed and the MTC and NTM epidemiological data were determined for the first time.