In vitro anti-tuberculosis activity of azole drugs against Mycobacterium tuberculosis clinical isolates.

BACKGROUND: Latent tuberculosis has been associated with the persistence of dormant Mycobacterium tuberculosis in the organism of infected individuals, who are reservoirs of the bacilli and the source for spreading the disease in the community. New active anti-TB drugs exerting their metabolic action at different stages and on latent/dormant bacilli are urgently required to avoid endogenous reactivations and to be part of treatments of multi- and extensively-drug resistant tuberculosis (M/XDR-TB). It was previously reported that azole drugs are active against M. tuberculosis. For that reason, the aims of this study were to determine the in vitro activity of azole drugs, imidazole (clotrimazole, CLO and econazole, ECO) and nitroimidazole (metronidazole, MZ and ipronidazole, IPZ), against a collection of MDR M. tuberculosis clinical isolates; and to analyze their potential use in both the LTB and the active forms of M/XDR-TB treatments. METHODS: A total of 55 MDR M. tuberculosis isolates and H37Rv were included. MZ and IPZ activity against M. tuberculosis isolates were tested using anaerobic culture conditions. The activity of ECO and CLO was measured by the minimal inhibitory concentration (MIC) using a microdilution colorimetric method. RESULTS: MZ and IPZ showed bacteriostatic activity against M. tuberculosis strains. MIC50 and MIC90 to ECO was 4.0µg/ml, while MIC50 to CLO was 4.0µg/ml and MIC90 was 8.0µg/ml respectively. CONCLUSION: All azole compounds tested in the study showed inhibitory activity against MDR M. tuberculosis clinical isolates.

In vitro and ex vivo activity of the fluoroquinolone DC-159a against mycobacteria.

Antimicrobial resistance is a global health problem. In 2021, it was estimated almost half a million of multidrug-resistant tuberculosis (MDR-TB) cases. Besides, non-tuberculous mycobacteria (NTM) are highly resistant to several drugs and the emergence of fluoroquinolone (FQ) resistant M. tuberculosis (Mtb) is also a global concern making treatments difficult and with variable outcome. The aim of this study was to evaluate the activity of the FQ, DC-159a, against Mtb and NTM and to explore the cross-resistance with the currently used FQs.A total of 12 pre-extensively drug-resistant (XDR) Mtb, 2 XDR, 36 fully drug susceptible strains and 41 NTM isolates were included to estimate the in vitro activity of DC-159a, moxifloxacin (MOX) and levofloxacin (LX), using minimal inhibitory and bactericidal concentration (MIC and MBC). The activity inside the human macrophages and pulmonary epithelial cells were also determined.DC-159a was active in vitro and ex vivo against mycobacteria. Besides, it was more active than MOX/LX. Moreover, no cross-resistance was evidenced between DC-159a and LX/MOX as DC-159a could inhibit Mtb and MAC strains that were already resistant to LX/MOX.DC-159a could be a possible candidate in new therapeutic regimens for MDR/ XDR-TB and mycobacterioses cases.

First evaluation in Argentina of the GenoType® MTBDRplus assay for multidrug-resistant Mycobacterium tuberculosis detection from clinical isolates and specimens.

Tuberculosis (tB) and multidrug and extensively drug-resistant (dR) tB are important public health problems that are spreading worldwide. The aims of this study were to determine the sensitivity and specificity of the genotype® mtBdRplus assay from smear-positive clinical specimens and isolates and to explore its possible application in routine work. Clinical samples were previously decontaminated using naoH-n-acetyl-l-cystein or naoH-Clna hypertonic solution for Ziehl-neelsen staining and cultures. The leftover sediments of smear-positive samples were stored at -20 °C, 70 of which were selected to be included in this study according to their dR profile. thirty dR Mycobacterium tuberculosis isolates were also assessed. Sequencing was used as gold standard to detect mutations conferring isoniazid (InH) and rifampicin (RIF) resistance. Valid results were obtained in 94.0 % of the samples and 85.5 % (53/62) of the InH-R samples were properly identified. mutations in the katGS315t gene and inhA C-15t gene promoter region were present in 59.7 % (37/62) and 25.8 % (16/62) of the InH-R samples, respectively. the system could also identify 97.7 % (41/42) of the RIF-R samples; the mutations found were rpoBS531l (66.7 %, 28/42), d516V (19.0 %, 8/42), H526Y and S531p/W (4.8 %, 2/42 each one), and S522l/Q (2.4 %, 1/42). a 98.8 % concordance between the genotype assay and sequencing was obtained. genotype® mtBdRplus has demonstrated to be easy to implement and to perform in clinical laboratories and useful for a rapid detection of dR M. tuberculosis from decontaminated sputa and clinical isolates. Therefore, this assay could be applied as a rapid tool to predict InH-R and/or RIF-R in dR risk cases.

Predictive value of direct nitrate reductase assay and its clinical performance in the detection of multi- and extensively drug-resistant tuberculosis.

Conventional culture and drug susceptibility testing (DST) methods for Mycobacterium tuberculosis are laborious and time consuming. For this reason alternative rapid culture and DST techniques are urgently needed to shorten the time for drug-resistance detection. A total of 222 smear-positive sputum samples were evaluated by the direct nitrate reductase assay (D-NRA) on Lowenstein-Jensen medium, for the rapid and simultaneous detection of resistance to isoniazid, rifampicin, kanamycin and ofloxacin. p-Nitrobenzoic acid was also included for identification of the M. tuberculosis complex. Results were compared with the BACTEC MGIT 960 as gold standard. The general performance of the D-NRA was very good, reaching a global value of 97 %. D-NRA had a turn-around time of 16.9 days to obtain results while that of the indirect MGIT 960 system was 29 days. D-NRA is a low-cost technology, easy to set up in clinical laboratories and suitable to be used for DST of M. tuberculosis in all smear-positive samples.

Fitness of drug resistant Mycobacterium tuberculosis and the impact on the transmission among household contacts.

There has been an on-going debate on whether the development of drug resistance in Mycobacterium tuberculosis reduces its relative fitness and its ability to cause disease. The aim of this study was to explore this relationship. For this purpose, we evaluated the in vitro growth of clinical isolates and the transmission of the strains within the patients' households. Clinical and epidemiological data from patients in households, drug-susceptibility and genetic patterns of the isolates were collected. BACTEC MGIT 960™ system with the Epicenter™ software was used to perform fitness experiments and calculate the relative fitness (RF) comparing with the H73Rv reference strain. From 39 households, 124 patients and 388 contacts were included. Concerning transmission, 20 Multi drug-resistant (MDR) and 16 drug sensitive (DS) index cases generated 23 and 28 secondary cases, respectively. An average RF drop of 16.7% was found for MDR strains, but only mutations in rpoB codons 531 were associated with reduced fitness. When the strains were transmitted, their RF tended to decrease, and strains with low RF were less frequently transmitted. Within the limitations of this study, the results showed that the decrease in RF was associated to a limited transmission among the households' contacts.