scholarly journals Induction of Mycobacterial Resistance to Quinolone Class Antimicrobials

2012 ◽  
Vol 56 (7) ◽  
pp. 3879-3887 ◽  
Author(s):  
Muhammad Malik ◽  
Kalyan Chavda ◽  
Xilin Zhao ◽  
Nirali Shah ◽  
Syed Hussain ◽  
...  

ABSTRACTAn agar plate assay was developed for detecting the induction of drug-resistant mycobacterial mutants during exposure to inhibitors of DNA gyrase. WhenMycobacterium smegmatison drug-containing agar, resistant colonies arose over a period of 2 weeks. ArecAdeficiency reduced mutant recovery, consistent with involvement of the SOS response in mutant induction. The C-8-methoxy compounds gatifloxacin and moxifloxacin allowed the recovery of fewer resistant mutants than either ciprofloxacin or levofloxacin when present at the same multiple of the MIC; a quinolone-like 8-methoxy-quinazoline-2,4-dione was more effective at restricting the emergence of resistant mutants than its cognate fluoroquinolone. Thus, the structure of fluoroquinolone-like compounds affects mutant recovery. A spontaneous mutator mutant ofM. smegmatis, obtained by growth in medium containing both isoniazid and rifampin, increased mutant induction during exposure to ciprofloxacin. Moreover, the mutator increased the size of spontaneous resistant mutant subpopulations, as detected by population analysis. Induction of ciprofloxacin resistance was also observed withMycobacterium tuberculosisH37Rv. When measured with clinical isolates, no difference in mutant recovery was observed between multidrug-resistant (MDR) and pansusceptible isolates. This finding is consistent with at least some MDR isolates ofM. tuberculosislacking mutators detectable by the agar plate assay. Collectively, the data indicate that the use of fluoroquinolones against tuberculosis may induce resistance and that the choice of quinolone may be important for restricting the recovery of induced mutants.

2019 ◽  
Vol 63 (12) ◽  
Author(s):  
A. L. Bidaud ◽  
F. Botterel ◽  
A. Chowdhary ◽  
E. Dannaoui

ABSTRACT Candida auris is an emerging, multidrug-resistant pathogen responsible for invasive hospital-acquired infections. Flucytosine is an effective anti-Candida species drug, but which cannot be used as a monotherapy because of the risk of development of resistant mutants during treatment. It is, therefore, noteworthy to test possible combinations with flucytosine that may have a synergistic interaction. In this study, we determined the in vitro interaction between flucytosine and amphotericin B, micafungin, or voriconazole. These combinations have been tested against 15 C. auris isolates. The MIC ranges (geometric mean [Gmean]) of flucytosine, amphotericin B, micafungin, and voriconazole were 0.125 to 1 μg/ml (0.42 μg/ml), 0.25 to 1 μg/ml (0.66 μg/ml), 0.125 to 0.5 μg/ml (0.3 μg/ml), and 0.03 to 4 μg/ml (1.05 μg/ml), respectively. When tested in combination, indifferent interactions were mostly observed with fractional inhibitory concentration index values from 0.5 to 1, 0.31 to 1.01, and 0.5 to 1.06 for the combinations of flucytosine with amphotericin B, micafungin, and voriconazole, respectively. A synergy was observed for the strain CBS 10913 from Japan. No antagonism was observed for any combination. The combination of flucytosine with amphotericin B or micafungin may be relevant for the treatment of C. auris infections.


2011 ◽  
Vol 55 (12) ◽  
pp. 5826-5833 ◽  
Author(s):  
Chao-Hsien Chen ◽  
Chiang-Ching Huang ◽  
Tsao-Chuen Chung ◽  
Rouh-Mei Hu ◽  
Yi-Wei Huang ◽  
...  

ABSTRACTKJ09C, a multidrug-resistant mutant ofStenotrophomonas maltophiliaKJ, was generated byin vitroselection with chloramphenicol. The multidrug-resistant phenotype of KJ09C was attributed to overexpression of a resistance nodulation division (RND)-type efflux system encoded by an operon consisting of five genes:smeU1,smeV,smeW,smeU2, andsmeX. Proteins encoded bysmeV,smeW, andsmeXwere similar to the membrane fusion protein, RND transporter, and outer membrane protein, respectively, of known RND-type systems. The proteins encoded bysmeU1andsmeU2were found to belong to the family of short-chain dehydrogenases/reductases. Mutant KJ09C exhibited increased resistance to chloramphenicol, quinolones, and tetracyclines and susceptibility to aminoglycosides; susceptibility to β-lactams and erythromycin was not affected. The expression of thesmeU1-V-W-U2-Xoperon was regulated by the divergently transcribed LysR-type regulator genesmeRv. Overexpression of the SmeVWX pump contributed to the acquired resistance to chloramphenicol, quinolones, and tetracyclines. Inactivation ofsmeVandsmeWcompletely abolished the activity of the SmeVWX pump, whereas inactivation ofsmeXalone decreased the activity of the SmeVWX pump. The enhanced aminoglycoside susceptibility observed in KJ09C resulted from SmeX overexpression.


mBio ◽  
2018 ◽  
Vol 9 (3) ◽  
Author(s):  
Catherine Vilchèze ◽  
Jacqueline Copeland ◽  
Tracy L. Keiser ◽  
Torin Weisbrod ◽  
Jacqueline Washington ◽  
...  

ABSTRACTMultidrug-resistant (MDR) tuberculosis, defined as tuberculosis resistant to the two first-line drugs isoniazid and rifampin, poses a serious problem for global tuberculosis control strategies. Lack of a safe and convenient model organism hampers progress in combating the spread of MDR strains ofMycobacterium tuberculosis. We reasoned that auxotrophic MDR mutants ofM. tuberculosiswould provide a safe means for studying MDRM. tuberculosiswithout the need for a biosafety level 3 (BSL3) laboratory. Two different sets of triple auxotrophic mutants ofM. tuberculosiswere generated, which were auxotrophic for the nutrients leucine, pantothenate, and arginine or for leucine, pantothenate, and methionine. These triple auxotrophic strains retained their acid-fastness, their ability to generate both a drug persistence phenotype and drug-resistant mutants, and their susceptibility to plaque-forming mycobacterial phages. MDR triple auxotrophic mutants were obtained in a two-step fashion, selecting first for solely isoniazid-resistant or rifampin-resistant mutants. Interestingly, selection for isoniazid-resistant mutants of the methionine auxotroph generated isolates with single point mutations inkatG, which encodes an isoniazid-activating enzyme, whereas similar selection using the arginine auxotroph yielded isoniazid-resistant mutants with large deletions in the chromosomal region containingkatG. TheseM. tuberculosisMDR strains were readily sterilized by second-line tuberculosis drugs and failed to kill immunocompromised mice. These strains provide attractive candidates forM. tuberculosisbiology studies and drug screening outside the BSL3 facility.IMPORTANCEElimination ofMycobacterium tuberculosis, the bacterium causing tuberculosis, requires enhanced understanding of its biology in order to identify new drugs against drug-susceptible and drug-resistantM. tuberculosisas well as uncovering novel pathways that lead toM. tuberculosisdeath. To circumvent the need for a biosafety level 3 (BSL3) laboratory when conducting research onM. tuberculosis, we have generated drug-susceptible and drug-resistant triple auxotrophic strains ofM. tuberculosissuitable for use in a BSL2 laboratory. These strains originate from a double auxotrophicM. tuberculosisstrain, H37Rv ΔpanCDΔleuCD, which was reclassified as a BSL2 strain based on its lack of lethality in immunocompromised and immunocompetent mice. A third auxotrophy (methionine or arginine) was introduced via deletion ofmetAorargB, respectively, sinceM. tuberculosisΔmetAandM. tuberculosisΔargBare unable to survive amino acid auxotrophy and infect their host. The resulting triple auxotrophicM. tuberculosisstrains retained characteristics ofM. tuberculosisrelevant for most types of investigations.


2013 ◽  
Vol 57 (8) ◽  
pp. 3738-3745 ◽  
Author(s):  
Hee Ji Lee ◽  
Phillip J. Bergen ◽  
Jurgen B. Bulitta ◽  
Brian Tsuji ◽  
Alan Forrest ◽  
...  

ABSTRACTCombination therapy may be required for multidrug-resistant (MDR)Acinetobacter baumannii. This study systematically investigated bacterial killing and emergence of colistin resistance with colistin and rifampin combinations against MDRA. baumannii. Studies were conducted over 72 h in anin vitropharmacokinetic (PK)/pharmacodynamic (PD) model at inocula of ∼106and ∼108CFU/ml using two MDR clinical isolates ofA. baumannii, FADDI-AB030 (colistin susceptible) and FADDI-AB156 (colistin resistant). Three combination regimens achieving clinically relevant concentrations (constant colistin concentration of 0.5, 2, or 5 mg/liter and a rifampin maximum concentration [Cmax] of 5 mg/liter every 24 hours; half-life, 3 h) were investigated. Microbiological response was measured by serial bacterial counts. Population analysis profiles assessed emergence of colistin resistance. Against both isolates, combinations resulted in substantially greater killing at the low inoculum; combinations containing 2 and 5 mg/liter colistin increased killing at the high inoculum. Combinations were additive or synergistic at 6, 24, 48, and 72 h with all colistin concentrations against FADDI-AB030 and FADDI-AB156 in, respectively, 8 and 11 of 12 cases (i.e., all 3 combinations) at the 106-CFU/ml inoculum and 8 and 7 of 8 cases with the 2- and 5-mg/liter colistin regimens at the 108-CFU/ml inoculum. For FADDI-AB156, killing by the combination was ∼2.5 to 7.5 and ∼2.5 to 5 log10CFU/ml greater at the low inoculum (all colistin concentrations) and high inoculum (2 and 5 mg/liter colistin), respectively. Emergence of colistin-resistant subpopulations was completely suppressed in the colistin-susceptible isolate with all combinations at both inocula. Our study provides important information for optimizing colistin-rifampin combinations against colistin-susceptible and -resistant MDRA. baumannii.


2011 ◽  
Vol 55 (10) ◽  
pp. 4858-4865 ◽  
Author(s):  
Sofia Borges ◽  
Pedro Cravo ◽  
Alison Creasey ◽  
Richard Fawcett ◽  
Katarzyna Modrzynska ◽  
...  

ABSTRACTMultidrug-resistantPlasmodium falciparummalaria parasites pose a threat to effective drug control, even to artemisinin-based combination therapies (ACTs). Here we used linkage group selection and Solexa whole-genome resequencing to investigate the genetic basis of resistance to component drugs of ACTs. Using the rodent malaria parasiteP. chabaudi, we analyzed the uncloned progeny of a genetic backcross between the mefloquine-, lumefantrine-, and artemisinin-resistant mutant AS-15MF and a genetically distinct sensitive clone, AJ, following drug treatment. Genomewide scans of selection showed that parasites surviving each drug treatment bore a duplication of a segment of chromosome 12 (translocated to chromosome 04) present in AS-15MF. Whole-genome resequencing identified the size of the duplicated segment and its position on chromosome 4. The duplicated fragment extends for ∼393 kbp and contains over 100 genes, includingmdr1, encoding the multidrug resistance P-glycoprotein homologue 1. We therefore show that resistance to chemically distinct components of ACTs is mediated by the same genetic mutation, highlighting a possible limitation of these therapies.


Microbiology ◽  
2020 ◽  
Vol 166 (9) ◽  
pp. 837-848
Author(s):  
Yingyu Liu ◽  
Melanie J. Filiatrault

Bacterial soft rot caused by the bacteria Dickeya and Pectobacterium is a destructive disease of vegetables, as well as ornamental plants. Several management options exist to help control these pathogens. Because of the limited success of these approaches, there is a need for the development of alternative methods to reduce losses. In this study, we evaluated the effect of potassium tetraborate tetrahydrate (PTB) on the growth of six Dickeya and Pectobacterium spp. Disc diffusion assays showed that Dickeya spp. and Pectobacterium spp. differ in their sensitivity to PTB. Spontaneous PTB-resistant mutants of Pectobacterium were identified and further investigation of the mechanism of PTB resistance was conducted by full genome sequencing. Point mutations in genes cpdB and supK were found in a single Pectobacterium atrosepticum PTB-resistant mutant. Additionally, point mutations in genes prfB (synonym supK) and prmC were found in two independent Pectobacterium brasiliense PTB-resistant mutants. prfB and prmC encode peptide chain release factor 2 and its methyltransferase, respectively. We propose the disruption of translation activity due to PTB leads to Pectobacterium growth inhibition. The P. atrosepticum PTB-resistant mutant showed altered swimming motility. Disease severity was reduced for P. atrosepticum -inoculated potato stems sprayed with PTB. We discuss the potential risk of selecting for bacterial resistance to this chemical.


2019 ◽  
Vol 63 (8) ◽  
Author(s):  
Rebecca J. Silver ◽  
Michelle K. Paczosa ◽  
Anne L. McCabe ◽  
Joan-Miquel Balada-Llasat ◽  
James D. Baleja ◽  
...  

ABSTRACTThe emergence of multidrug-resistantKlebsiella pneumoniaehas rendered a large array of infections difficult to treat. In a high-throughput genetic screen of factors required forK. pneumoniaesurvival in the lung, amino acid biosynthesis genes were critical for infection in both immunosuppressed and wild-type (WT) mice. The limited pool of amino acids in the lung did not change during infection and was insufficient forK. pneumoniaeto overcome attenuating mutations inaroA,hisA,leuA,leuB,serA,serB,trpE, andtyrAin WT and immunosuppressed mice. Deletion ofaroA, which encodes 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase class I, resulted in the most severe attenuation. Treatment with the EPSP synthase-specific competitive inhibitor glyphosate decreasedK. pneumoniaegrowth in the lungs.K. pneumoniaeexpressing two previously identified glyphosate-resistant mutations in EPSP synthase had significant colonization defects in lung infection. Selection and characterization of six spontaneously glyphosate-resistant mutants inK. pneumoniaeyielded no mutations inaroA. Strikingly, glyphosate treatment of mice lowered the bacterial burden of two of three spontaneous glyphosate-resistant mutants and further lowered the burden of the less-attenuated EPSP synthase catalytic mutant. Of 39 clinical isolate strains, 9 were resistant to glyphosate at levels comparable to those of selected resistant strains, and none appeared to be more highly resistant. These findings demonstrate amino acid biosynthetic pathways essential forK. pneumoniaeinfection are promising novel therapeutic targets.


2016 ◽  
Vol 60 (5) ◽  
pp. 3106-3111 ◽  
Author(s):  
Olusegun O. Soge ◽  
Stephen J. Salipante ◽  
David No ◽  
Erin Duffy ◽  
Marilyn C. Roberts

ABSTRACTWe evaluated thein vitroactivity of delafloxacin against a panel of 117Neisseria gonorrhoeaestrains, including 110 clinical isolates collected from 2012 to 2015 and seven reference strains, compared with the activities of seven antimicrobials currently or previously recommended for treatment of gonorrhea. We examined the potential for delafloxacin to select for resistant mutants in ciprofloxacin-susceptible and ciprofloxacin-resistantN. gonorrhoeae. We characterized mutations in thegyrA,gyrB,parC, andparEgenes and the multidrug-resistant efflux pumps (MtrC-MtrD-MtrE and NorM) by PCR and sequencing and by whole-genome sequencing. The MIC50, MIC90, and MIC ranges of delafloxacin were 0.06 μg/ml, 0.125 μg/ml, and ≤0.001 to 0.25 μg/ml, respectively. The frequency of spontaneous mutation ranged from 10−7to <10−9. The multistep delafloxacin resistance selection of 30 daily passages resulted in stable resistant mutants. There was no obvious cross-resistance to nonfluoroquinolone comparator antimicrobials. A mutant with reduced susceptibility to ciprofloxacin (MIC, 0.25 μg/ml) obtained from the ciprofloxacin-susceptible parental strain had a novel Ser91Tyr alteration in thegyrAgene. We also identified new mutations in thegyrAand/orparCandparEgenes and the multidrug-resistant efflux pumps (MtrC-MtrD-MtrE and NorM) of two mutant strains with elevated delafloxacin MICs of 1 μg/ml. Although delafloxacin exhibited potentin vitroactivity againstN. gonorrhoeaeisolates and reference strains with diverse antimicrobial resistance profiles and demonstrated a low tendency to select for spontaneous mutants, it is important to establish the correlation between these excellentin vitrodata and treatment outcomes through appropriate randomized controlled clinical trials.


mBio ◽  
2015 ◽  
Vol 6 (6) ◽  
Author(s):  
Ashley N. Brown ◽  
George L. Drusano ◽  
Jonathan R. Adams ◽  
Jaime L. Rodriquez ◽  
Kalyani Jambunathan ◽  
...  

ABSTRACT Linezolid is an oxazolidinone with potent activity against Mycobacterium tuberculosis. Linezolid toxicity in patients correlates with the dose and duration of therapy. These toxicities are attributable to the inhibition of mitochondrial protein synthesis. Clinically relevant linezolid regimens were simulated in the in vitro hollow-fiber infection model (HFIM) system to identify the linezolid therapies that minimize toxicity, maximize antibacterial activity, and prevent drug resistance. Linezolid inhibited mitochondrial proteins in an exposure-dependent manner, with toxicity being driven by trough concentrations. Once-daily linezolid killed M. tuberculosis in an exposure-dependent manner. Further, 300 mg linezolid given every 12 hours generated more bacterial kill but more toxicity than 600 mg linezolid given once daily. None of the regimens prevented linezolid resistance. These findings show that with linezolid monotherapy, a clear tradeoff exists between antibacterial activity and toxicity. By identifying the pharmacokinetic parameters linked with toxicity and antibacterial activity, these data can provide guidance for clinical trials evaluating linezolid in multidrug antituberculosis regimens. IMPORTANCE The emergence and spread of multidrug-resistant M. tuberculosis are a major threat to global public health. Linezolid is an oxazolidinone that is licensed for human use and has demonstrated potent activity against multidrug-resistant M. tuberculosis. However, long-term use of linezolid has shown to be toxic in patients, often resulting in thrombocytopenia. We examined therapeutic linezolid regimens in an in vitro model to characterize the exposure-toxicity relationship. The antibacterial activity against M. tuberculosis was also assessed for these regimens, including the amplification or suppression of resistant mutant subpopulations by the chosen regimen. Higher exposures of linezolid resulted in greater antibacterial activity, but with more toxicity and, for some regimens, increased resistant mutant subpopulation amplification, illustrating the trade-off between activity and toxicity. These findings can provide valuable insight for designing optimal dosage regimens for linezolid that are part of the long combination courses used to treat multidrug-resistant M. tuberculosis.


2019 ◽  
Vol 63 (4) ◽  
Author(s):  
Htut Htut Htoo ◽  
Lauren Brumage ◽  
Vorrapon Chaikeeratisak ◽  
Hannah Tsunemoto ◽  
Joseph Sugie ◽  
...  

ABSTRACTAn increasing number of multidrug-resistantAcinetobacter baumannii(MDR-AB) infections have been reported worldwide, posing a threat to public health. The establishment of methods to elucidate the mechanism of action (MOA) ofA. baumannii-specific antibiotics is needed to develop novel antimicrobial therapeutics with activity against MDR-AB. We previously developed bacterial cytological profiling (BCP) to understand the MOA of compounds inEscherichia coliandBacillus subtilis. Given how distantly relatedA. baumanniiis to these species, it was unclear to what extent it could be applied. Here, we implemented BCP as an antibiotic MOA discovery platform forA. baumannii. We found that the BCP platform can distinguish among six major antibiotic classes and can also subclassify antibiotics that inhibit the same cellular pathway but have different molecular targets. We used BCP to show that the compound NSC145612 inhibits the growth ofA. baumanniivia targeting RNA transcription. We confirmed this result by isolating and characterizing resistant mutants with mutations in therpoBgene. Altogether, we conclude that BCP provides a useful tool for MOA studies of antibacterial compounds that are active againstA. baumannii.


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