Estimating Fitness by Competition Assays between Drug Susceptible and Resistant Mycobacterium tuberculosis of Predominant Lineages in Mumbai, India

Bhatter, Purva; Chatterjee, Anirvan; D'souza, Desiree T.B.; Tolani, Monica; Mistry, Nerges

doi:10.1371/journal.pone.0033507

Cited by 25 publications

(26 citation statements)

References 24 publications

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“…We therefore missed an opportunity to compare the performance of different culture systems to detect the “false-negative” MTB isolates. Third, several previous reports have revealed that MTB with resistance mutations is associated with a decrease in fitness [16–18], while the drug susceptibility profiles and mutant types conferring drug resistance of MTB isolates were not detected in this study. Hence, further analysis of MTB isolates with false-negative results will extend our knowledge regarding the relationship between specific mutations and loss of fitness.…”

Section: Discussioncontrasting

confidence: 56%

Factors Associated with Missed Detection ofMycobacterium tuberculosisby Automated BACTEC MGIT 960 System

Zhang²,

et al. 2016

BioMed Research International

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Despite the demonstration of excellent performance, mycobacterial growth in BACTEC MGIT 960 can go undetected. The aim of this study was to investigate the prevalence of “false-negative” culture sample in Beijing and the potential factors associated with the detection failures by MGIT 960. Of the 577 sputum samples tested, 141 (24.4%) were culture-positive for mycobacteria, of which 133 (94.3%) were automatically determined by MGIT 960 system and 8 (5.7%) were positive for visual growth (false negative by MGIT). Statistical analysis showed that positive grade of specimen had no influence on the false-negative rate by MGIT 960 system (χ 2 = 2.207, P = 0.820). In addition, the mean time to detection (TTD) was 241.4 (range: 224–261) hours for false-negative group and 186.8 (range: 173–199) hours for positive group. The difference in TTD between false-negative and positive groups was statistically significant (P < 0.01). In conclusion, our data demonstrate that the automatic MGIT missed a small portion of bacteriological mycobacterial patients. In addition, the poor growth rate rather than the low grade of AFB smear is associated with the detection failure by MGIT. Our findings highlight the notion that manual inspection for all instrument-negative MGIT tubes will bring about considerable benefit to patients and clinicians.

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Section: Discussioncontrasting

confidence: 56%

Factors Associated with Missed Detection ofMycobacterium tuberculosisby Automated BACTEC MGIT 960 System

Zhang²,

et al. 2016

BioMed Research International

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“…This shows that the results for fully susceptible strains were significantly likely to be available before those for strains with any resistance. This might be due to the fact that drug-resistant isolates have lower overall metabolic activity and grow slower than the wild strains [30]. Thus, the sensitivity of the MTT method depends on the metabolic activity of viable cells in order to achieve measurable MTT reduction [20].…”

Section: Discussionmentioning

confidence: 99%

Evaluation of Direct Colorimetric MTT Assay for Rapid Detection of Rifampicin and Isoniazid Resistance in Mycobacterium tuberculosis

2016

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With the spread of multidrug-resistant tuberculosis (MDR-TB) strains there is an increasing need for new accurate and cost-effective methods for a rapid diagnostic and drug susceptibility testing (DST), particularly in low-income countries where tuberculosis is hyperendemic. A colorimetric assay using 3-(4, 5-dimethylthiazol-2-yl)-2, 5- diphenyltetrazolium bromide (MTT) has been suggested as a promising method for DST, especially to rifampicin. In this study, we standardized and evaluated the MTT assay for a rapid direct detection of rifampicin and isoniazid resistant Mycobacterium tuberculosis strains from sputum specimens using Lowenstein-Jensen (LJ) culture medium as a gold standard. The MTT assay sensitivity, specificity, positive and negative predictive values for rifampicin were 100%, 86%, 100%, 99%, respectively. For isoniazid, the MTT assay had a 100% sensitivity, specificity, positive and negative predictive values. Interestingly, the MTT assay gave interpretable results within two weeks for 94% of the samples compared to 7–14 weeks for LJ media. Overall, an excellent agreement was observed between MTT assay and LJ proportion method (Kappa, 0.91 for rifampicin and 1.00 for isoniazid). In conclusion, the direct colorimetric MTT assay simultaneously detects susceptible and resistant strains of M. tuberculosis within three weeks. It significantly shortens the time required to obtain a DST result and could be a reliable alternative method for rapid detection of drug-resistant TB strains in high-TB-burden resource-limited settings.

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“…To test this, we implemented a stochastic competitive growth assay to compare the fitness of the Wildtype network to a new variant with reduced noise ( Reduced Noise ). Competition assays can be used to discriminate between genotypes in order to identify those that achieve higher population fitness [57]–[59]. We developed a stochastic competition assay by using a modified evolutionary algorithm: cells are first initialized with equal representation of each of the alternative networks, simulation are performed, the cost for each cell is calculated, and cells with poorly performing phenotypes are replaced by top performers (Methods).…”

Section: Resultsmentioning

confidence: 99%

Tunable Stochastic Pulsing in the Escherichia coli Multiple Antibiotic Resistance Network from Interlinked Positive and Negative Feedback Loops

Garcia‐Bernardo

Dunlop

2013

PLoS Comput Biol

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Cells live in uncertain, dynamic environments and have many mechanisms for sensing and responding to changes in their surroundings. However, sudden fluctuations in the environment can be catastrophic to a population if it relies solely on sensory responses, which have a delay associated with them. Cells can reconcile these effects by using a tunable stochastic response, where in the absence of a stressor they create phenotypic diversity within an isogenic population, but use a deterministic response when stressors are sensed. Here, we develop a stochastic model of the multiple antibiotic resistance network of Escherichia coli and show that it can produce tunable stochastic pulses in the activator MarA. In particular, we show that a combination of interlinked positive and negative feedback loops plays an important role in setting the dynamics of the stochastic pulses. Negative feedback produces a pulsatile response that is tunable, while positive feedback serves to amplify the effect. Our simulations show that the uninduced native network is in a parameter regime that is of low cost to the cell (taxing resistance mechanisms are expressed infrequently) and also elevated noise strength (phenotypic variability is high). The stochastic pulsing can be tuned by MarA induction such that variability is decreased once stresses are sensed, avoiding the detrimental effects of noise when an optimal MarA concentration is needed. We further show that variability in the expression of MarA can act as a bet hedging mechanism, allowing for survival in time-varying stress environments, however this effect is tunable to allow for a fully induced, deterministic response in the presence of a stressor.

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Estimating Fitness by Competition Assays between Drug Susceptible and Resistant Mycobacterium tuberculosis of Predominant Lineages in Mumbai, India

Cited by 25 publications

References 24 publications

Factors Associated with Missed Detection ofMycobacterium tuberculosisby Automated BACTEC MGIT 960 System

Factors Associated with Missed Detection ofMycobacterium tuberculosisby Automated BACTEC MGIT 960 System

Evaluation of Direct Colorimetric MTT Assay for Rapid Detection of Rifampicin and Isoniazid Resistance in Mycobacterium tuberculosis

Tunable Stochastic Pulsing in the Escherichia coli Multiple Antibiotic Resistance Network from Interlinked Positive and Negative Feedback Loops

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