Biology subjects

Avaliani, Z.

Publications and source records attributed to Avaliani, Z..

4 recordsLinked to original sources

bioRxiv2025

Within-host evolution of drug tolerance in Mycobacterium tuberculosis.

SynopsisO_ST_ABSBackgroundC_ST_ABSMycobacterium tuberculosis (Mtb) causes tuberculosis (TB) in humans. Poor treatment responses are a threat to global TB control, as such, understanding contributing factors to poor responses is important. We hypothesized that antibiotic tolerance could contribute to delayed culture conversion (recalcitrant TB), and resistance amplification in patients during TB treatment. ObjectivesTo investigate the role of drug tolerance in delayed culture conversion and resistance amplification in TB patients. MethodsWe collected serial Mtb isolates from i) patients with drug-susceptible TB who remained culture positive for up to 6 years (i.e. recalcitrant TB), and ii) patients with multidrug-resistant TB (MDR-TB) where resistance amplified during treatment. We measured tolerance to rifampicin (RIF) in drug-susceptible TB strains and tolerance to moxifloxacin (MFX) in MDR-TB strains using a real-time time-kill assay. ResultsRIF tolerance evolved within-host, increasing up to and ~1.5-fold, however, there was no apparent contribution of RIF tolerance to delayed culture conversion. Tolerance to Mfx in MDR-TB patients appeared negatively associated with resistance amplification and consistently decreased over time in patients. ConclusionOur findings confirm that antibiotic tolerance evolves in Mtb within patients over time during treatment. However, there was no evidence that this tolerance influences treatment responses, calling for further investigation of contributors to adverse treatment responses and their mitigation.

microbiology↗

bioRxiv2024

Drug-induced differential culturability in diverse strains of Mycobacterium tuberculosis.

Differential culturable bacteria grow in liquid culture medium but are unable to form colonies on solid medium. Differentially culturable Mycobacterium tuberculosis (Mtb) bacteria, have been found in tuberculosis (TB) patient sputa. We hypothesized that antibiotic treatment can induce differential culturability in Mtb. We investigated the effect of exposure to TB drugs on Mtb culturability using clinical samples from an ongoing TB patient cohort and by conducting several in vitro experiments with a diverse set of Mtb strains. In patients, serial sputa were more likely to generate Mtb-positive cultures in liquid as opposed to solid medium, with this liquid culture bias extending up to 5 months post diagnosis. Experimentally, there was a disparity between bacterial time to positivity (TTP) and colony forming units (CFUs) when Mtb was exposed to isoniazid (INH) and rifampicin (RIF) alone or in combination. Cultures recovered from RIF treatment yielded more CFUs on agar plates, but INH-treated cultures had a faster TTP in liquid. Follow up experiments using a fluorescently labelled laboratory strain of Mtb revealed that CFUs overestimated killing by INH treatment. Here we provide evidence in Mtb that drug exposure affects culturability on solid medium, which has implications for treatment monitoring and drug-pathogen interaction studies.

microbiology↗

bioRxiv2024

Genetic diversity within diagnostic sputum samples is mirrored in the culture of Mycobacterium tuberculosis

Culturing Mycobacterium tuberculosis (MTB) from tuberculosis cases is the basis for many research and clinical applications. Paradoxically, it is assumed to impose a diversity bottleneck, which, if true, would entail unexplored consequences. The alternative, culture-free sequencing from diagnostic samples, is a promising but challenging approach both to obtain and analyse the MTB genome from the complex sample. This study obtains high-quality genomes of sputum-culture pairs from two different settings after developing a workflow for sequencing from sputum and a tailored bioinformatics pipeline. Our approach reveals that 88% of variants called in culture-free sequencing analysis are false positives due to supplementary alignments, mostly in enriched-sputa samples. Overall, contrary to the bottleneck dogma, we identify a 97% variant agreement within sputum-culture pairs, with a high correlation also in the variants frequency (0.98). Our findings extrapolate to all publicly available data, thus demonstrating that in most cases culture accurately mirrors clinical samples.

genomics↗

bioRxiv2019

Prediction of multiple drug resistant pulmonary tuberculosis against drug sensitive pulmonary tuberculosis by CT nodular consolidation sign

Multidrug-resistant tuberculosis (mdrtb) refers to TB infection resistant to at least two most powerful anti-TB drugs, isoniazid and rifampincin. It has been estimated that globally 3.5% (which can be much higher in some regions) of newly diagnosed TB patients, and 20.5% of previously treated patients had mdrtb. Extensively drug-resistant TB (xdrtb) has resistance to rifampin and isoniazid, as well as to any member of the quinolone family and at least one of the second line injectable drugs: kanamycin, amikacin and capreomycin. xdrtb accounts for 4-20% of mdrtb. Early detection and targeted treatment are priorities for mdrtb/xdrtb control. The suspicion of mdr/xdr -pulmonary TB (mdrptb or xdrptb) by chest imaging shall suggest intensive diagnostic testing for mdrptb/xdrptb. We hypothesize that multiple nodular consolidation (NC) may serve one of the differentiators for separating dsptb vs mdrptb/xdrptb cases. For this study, mdrptb cases (n=310) and XDR-PTB cases ([xcap]=I58) were from the NIAID TB Portals Program (TBPP) . Drug sensitive pulmonary TB (dsptb) cases were from the TBPP collection (n=112) as well as the Shenzhen Center for Chronic Disease Control (n=111), Shenzhen, China, and we excluded patients with HIV(+) status. Our study shows NC, particularly multiple NCs, is more common in mdrptb than in dsptb, and more common in xdrptb than in mdrptb. For example, 2.24% of dsptb patients, 13.23% of mdrptb patients, and 20.89% of xdrptb patients, respectively, have NCs with diameter >= 10mm equal or more than 2 in number.

pathology↗