scholarly journals Isoniazid-Induced Transient High-Level Resistance in Mycobacterium tuberculosis

2002 ◽  
Vol 46 (9) ◽  
pp. 2804-2810 ◽  
Author(s):  
Miguel Viveiros ◽  
Isabel Portugal ◽  
Rosário Bettencourt ◽  
Thomas C. Victor ◽  
Annemarie M. Jordaan ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Culture Collection ◽  
Free Medium ◽  
Solid Media ◽  
Antibiotic Susceptibility Test ◽  
Efflux Mechanism ◽  
Resistant Strains ◽  
High Level ◽  
Drug Free ◽  
Level Resistance

ABSTRACT An American Type Culture Collection reference strain and eight clinical strains of Mycobacterium tuberculosis, all of which were susceptible to isoniazid (INH) (mean MIC, 0.06 mg/liter) and negative for the Ser315Thr katG mutation, were left in their BACTEC 12B vials (for use with the BACTEC 460-TB method) containing 0.1 mg of INH per liter for periods of up to 28 days after the completion of the antibiotic susceptibility test. Each eventually grew to levels compatible with those of INH-resistant strains. Successive passages in INH-containing BACTEC 12B vials and onto solid media showed that the resistance noted above was maintained. Successive passages of these M. tuberculosis strains in which INH resistance had been induced into BACTEC 12B vials or solid media containing stepwise increases in INH concentrations eventually yielded organisms resistant to 20 mg of INH per liter. Transfer of cells in which INH resistance had been induced to drug-free medium followed by repeated passages in that medium eventually yielded organisms whose susceptibility to INH was identical to that of the original parent strains. The cycle of induced INH resistance could be repeated with these now INH-susceptible cells. The use of M. tuberculosis identification probes and IS6110-based restriction fragment length polymorphism analyses of cultures throughout the induction of INH resistance and the reversal of resistance in drug-free medium eliminated the possibility that the culture was contaminated or that the initial specimen had a mixed type of infection. Induced high-level resistance to INH (20 mg/liter) could be reduced 100-fold with a subinhibitory concentration of reserpine but not with verapamil. These results collectively suggest that high-level resistance to INH can be induced in INH-susceptible M. tuberculosis strains by the induction of a reserpine-sensitive efflux mechanism.

scholarly journals Mutations in fbiD (Rv2983) as a Novel Determinant of Resistance to Pretomanid and Delamanid in Mycobacterium tuberculosis

2020 ◽  
Vol 65 (1) ◽  
pp. e01948-20
Author(s):  
Dalin Rifat ◽  
Si-Yang Li ◽  
Thomas Ioerger ◽  
Keshav Shah ◽  
Jean-Philippe Lanoix ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Clinical Evidence ◽  
Clinical Samples ◽  
Loss Of Function ◽  
Wild Type ◽  
Content Type ◽  
Solid Media ◽  
High Level ◽  
Level Resistance

ABSTRACTThe nitroimidazole prodrugs delamanid and pretomanid comprise one of only two new antimicrobial classes approved to treat tuberculosis (TB) in 50 years. Prior in vitro studies suggest a relatively low barrier to nitroimidazole resistance in Mycobacterium tuberculosis, but clinical evidence is limited to date. We selected pretomanid-resistant M. tuberculosis mutants in two mouse models of TB using a range of pretomanid doses. The frequency of spontaneous resistance was approximately 10−5 CFU. Whole-genome sequencing of 161 resistant isolates from 47 mice revealed 99 unique mutations, of which 91% occurred in 1 of 5 genes previously associated with nitroimidazole activation and resistance, namely, fbiC (56%), fbiA (15%), ddn (12%), fgd (4%), and fbiB (4%). Nearly all mutations were unique to a single mouse and not previously identified. The remaining 9% of resistant mutants harbored mutations in Rv2983 (fbiD), a gene not previously associated with nitroimidazole resistance but recently shown to be a guanylyltransferase necessary for cofactor F420 synthesis. Most mutants exhibited high-level resistance to pretomanid and delamanid, although Rv2983 and fbiB mutants exhibited high-level pretomanid resistance but relatively small changes in delamanid susceptibility. Complementing an Rv2983 mutant with wild-type Rv2983 restored susceptibility to pretomanid and delamanid. By quantifying intracellular F420 and its precursor Fo in overexpressing and loss-of-function mutants, we provide further evidence that Rv2983 is necessary for F420 biosynthesis. Finally, Rv2983 mutants and other F420H2-deficient mutants displayed hypersusceptibility to some antibiotics and to concentrations of malachite green found in solid media used to isolate and propagate mycobacteria from clinical samples.

scholarly journals Phenotypic and Molecular Characterization of Mycobacterium tuberculosis Isolates Resistant to both Isoniazid and Ethambutol

2005 ◽  
Vol 49 (6) ◽  
pp. 2218-2225 ◽  
Author(s):  
Linda M. Parsons ◽  
Max Salfinger ◽  
Anne Clobridge ◽  
Jillian Dormandy ◽  
Lisa Mirabello ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Susceptibility Testing ◽  
Rapid Screening ◽  
The Past ◽  
Resistant Strains ◽  
The Common ◽  
Susceptibility Tests ◽  
High Level ◽  
Level Resistance

ABSTRACT In performing radiometric susceptibility testing on over 2,000 patient isolates of Mycobacterium tuberculosis during the past 6 years, we found that resistance to 7.5 μg/ml ethambutol (EMB) occurred only in isolates that are also resistant to 0.4 μg/ml isoniazid (INH). Using 157 selected isolates in the present study, we performed radiometric and agar proportion susceptibility tests and DNA sequencing of genetic regions associated with resistance to these two drugs. The goal was to study the occurrence of the common mutations associated with resistance to each drug and also to determine whether any particular INH-resistance-associated mutation occurred more often in combination with any particular EMB-resistance-associated mutation. In an analysis of 128 isolates resistant to 0.4 μg/ml INH, we found that a mutation at katG Ser315 was more common in isolates also resistant to 7.5 μg/ml EMB (61 of 67 = 91.0%) than in isolates either susceptible to EMB or resistant to 2.5 μg/ml EMB (39 of 60 = 65.0%). These observations suggest that INH-resistant strains with a mutation at katG Ser315 are more likely to acquire resistance to 7.5 μg/ml EMB than are isolates with INH-resistance-associated mutations at other sites. In addition, we found that 64 of 67 (95.5%) isolates resistant to 7.5 μg/ml EMB contained a mutation in either codon 306 or codon 406 of embB. Met306Val was the most common embB mutation, present in 52 (77.6%) of the 67 isolates. Most occurrences of this mutation (49 of 52 = 94.2%) were found in isolates that also contained the katG Ser315Thr mutation. Finally, sequencing this region of embB appears to be sufficiently sensitive for use as a rapid screening tool for detection of high-level resistance to EMB.

scholarly journals Mutations in fbiD (Rv2983) as a novel determinant of resistance to pretomanid and delamanid in Mycobacterium tuberculosis

2020 ◽  
Author(s):  
Dalin Rifat ◽  
Si-Yang Li ◽  
Thomas Ioerger ◽  
Keshav Shah ◽  
Jean-Philippe Lanoix ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Clinical Evidence ◽  
Clinical Samples ◽  
Loss Of Function ◽  
Wild Type ◽  
Solid Media ◽  
Resistant Mutants ◽  
High Level ◽  
Level Resistance

ABSTRACTThe nitroimidazole pro-drugs delamanid and pretomanid comprise one of only two new antimicrobial classes approved to treat tuberculosis (TB) in 50 years. Prior in vitro studies suggest a relatively low barrier to nitroimidazole resistance in Mycobacterium tuberculosis, but clinical evidence is limited to date. We selected pretomanid-resistant M. tuberculosis mutants in two mouse models of TB using a range of pretomanid doses. The frequency of spontaneous resistance was approximately 10−5 CFU. Whole genome sequencing of 161 resistant isolates from 47 mice revealed 99 unique mutations, 91% of which occurred in 1 of 5 genes previously associated with nitroimidazole activation and resistance: fbiC (56%), fbiA (15%), ddn (12%), fgd (4%) and fbiB (4%). Nearly all mutations were unique to a single mouse and not previously identified. The remaining 9% of resistant mutants harbored mutations in Rv2983, a gene not previously associated with nitroimidazole resistance but recently shown to be a guanylyltransferase necessary for cofactor F420 synthesis. Most mutants exhibited high-level resistance to pretomanid and delamanid, although Rv2983 and fbiB mutants exhibited high-level pretomanid resistance, but relatively small changes in delamanid susceptibility. Complementing an Rv2983 mutant with wild-type Rv2983 restored susceptibility to pretomanid and delamanid. By quantifying intracellular F420 and its precursor Fo in overexpressing and loss-of-function mutants, we provide further evidence that Rv2983 is necessary for F420 biosynthesis. Finally, Rv2983 mutants and other F420H2-deficient mutants displayed hypersusceptibility to some antibiotics and to concentrations of malachite green found in solid media used to isolate and propagate mycobacteria from clinical samples.

scholarly journals Effects of an Efflux Mechanism and Ribosomal Mutations on Macrolide Susceptibility of Haemophilus influenzae Clinical Isolates

2003 ◽  
Vol 47 (3) ◽  
pp. 1017-1022 ◽  
Author(s):  
Mihaela Peric ◽  
Bülent Bozdogan ◽  
Michael R. Jacobs ◽  
Peter C. Appelbaum
Keyword(s):  
Haemophilus Influenzae ◽  
Resistance Mechanisms ◽  
Macrolide Resistance ◽  
23S Rrna ◽  
Carbonyl Cyanide ◽  
Efflux Mechanism ◽  
Resistant Strains ◽  
High Level ◽  
Susceptibility Patterns ◽  
Level Resistance

ABSTRACT This study investigated macrolide resistance mechanisms in clinical Haemophilus influenzae strains with different levels of susceptibility to macrolides. A total of 6,382 isolates were collected during the Alexander Project from 1997 to 2000. For 96.9% of these isolates, the azithromycin MICs were 0.25 to 4 μg/ml, and these were defined as baseline strains. For 1.8% of the isolates, the azithromycin MICs were lower (<0.25 μg/ml), and for 1.3% of the isolates, the MICs were higher (>4 μg/ml). These isolates were defined as hypersusceptible and high-level macrolide-resistant strains, respectively. To identify the mechanisms associated with these three susceptibility patterns, representative strains were studied for the presence of macrolide efflux pumps and for ribosomal alterations. Macrolide efflux was studied by measuring the accumulation of radioactive azithromycin and clarithromycin in the presence or absence of carbonyl cyanide m-chlorophenylhydrazone (CCCP), a protonophore. Treatment with CCCP increased the accumulation of macrolides in baseline as well as high-level resistant strains, demonstrating the presence of an efflux mechanism, but not in the 20 hypersusceptible strains tested. Among the 31 strains studied that showed high-level resistance to both azithromycin and clarithromycin, 28 had ribosomal alterations, 7 had mutations in ribosomal protein L4, 11 had mutations in L22, 2 had mutations in 23S rRNA, 8 had multiple mutations, and 3 had no mutations. From these results, we conclude that the vast majority (>98%) of H. influenzae strains have a macrolide efflux mechanism, with a few of these being hyperresistant (1.3%) due to one or several ribosomal mutations. Occasional hypersusceptible strains (1.8%) were found and had no macrolide resistance mechanisms and appeared to be the only truly macrolide-susceptible variants of H. influenzae.

scholarly journals Significant contribution of the CmeABC Efflux pump in high-level resistance to ciprofloxacin and tetracycline in Campylobacter jejuni and Campylobacter coli clinical isolates

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Saeed Sharifi ◽  
Bita Bakhshi ◽  
Shahin Najar-peerayeh
Keyword(s):  
Gene Expression ◽  
Point Mutation ◽  
Campylobacter Jejuni ◽  
Significant Contribution ◽  
Efflux Pump ◽  
Campylobacter Coli ◽  
Rapd Pcr ◽  
Resistant Strains ◽  
High Level ◽  
Level Resistance

Abstract Background Campylobacter resistance to antimicrobial agents is regarded as a major concern worldwide. The aim of this study was to investigate the expression of the CmeABC efflux pump and the RAPD-PCR pattern in drug-resistant Campylobacter isolates. Methods A total of 283 stool specimens were collected from children under the age of five with diarrhea. The minimum inhibitory concentration (MIC) of tetracycline and ciprofloxacin was determined by broth microdilution method and E-test, respectively. Detection of tetracycline and ciprofloxacin determinants was done by amplification of tetO gene and PCR-sequencing of the gyrA gene. The cmeABC transcriptional expression was analyzed by Real-time (RT)-PCR. Clonal correlation of resistant strains was determined by RAPD-PCR genotyping. Results Out of 283 fecal samples, 20 (7.02%) samples were positive for Campylobacter spp. Analysis of duplex PCR assay of the cadF gene showed that 737 and 461 bp amplicons were corresponding to Campylobacter jejuni and Campylobacter coli, respectively. All of the 17 phenotypically tetracycline-resistant Campylobacter isolates harbored the tetO gene. Also, four phenotypically ciprofloxacin-resistant Campylobacter isolates had a point mutation at codon 257 of the gyrA gene (ACA to ATA; Thr > Ile). High-level expression of the cmeA gene was observed in ciprofloxacin-resistant and high-level tetracycline-resistant Campylobacter isolates, suggesting a positive correlation between the cmeA gene expression level and tetracycline resistance level. Moreover, a statistically significant difference was observed in the cmeA gene expression between ciprofloxacin-resistant and ciprofloxacin-susceptible strains, which signifies the crucial contribution of the efflux pump in conferring multiple drug resistance phenotype among Campylobacter spp. RAPD analysis of Campylobacter isolates exhibited 16 different patterns. Simpsone`s diversity index of RAPD-PCR was calculated as 0.85, showing a high level of homogeneity among the population; however, no clear correlation was detected among tetracycline and/or ciprofloxacin resistant isolates. Conclusion Significant contribution of the CmeABC efflux pump in conferring high-level resistance to tetracycline and ciprofloxacin was observed in C. jejuni and C. coli clinical isolates. The resistant phenotype is suggested to be mediated by CmeABC efflux pumps, the tetO gene, and point mutation of the gyrA gene. Genotyping revealed no clonal correlation among resistant strains, indicating distinct evolution of tetracycline and ciprofloxacin resistant genotypes among the isolates.

scholarly journals In Vitro Study of Stepwise Acquisition of rv0678 and atpE Mutations Conferring Bedaquiline Resistance

2019 ◽  
Vol 63 (8) ◽  
Author(s):  
Nabila Ismail ◽  
Nazir A. Ismail ◽  
Shaheed V. Omar ◽  
Remco P. H. Peters
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Solid Medium ◽  
In Vitro Study ◽  
Whole Genome ◽  
Content Type ◽  
Phenotypic Resistance ◽  
Atcc Strain ◽  
High Level ◽  
Level Resistance

ABSTRACT Bedaquiline resistance within Mycobacterium tuberculosis may arise through efflux-based (rv0678) or target-based (atpE) pathway mutations. M. tuberculosis mutant populations from each of five sequential steps in a passaging approach, using a pyrazinamide-resistant ATCC strain, were subjected to MIC determinations and whole-genome sequencing. Exposure to increasing bedaquiline concentrations resulted in increasing phenotypic resistance (up to >2 μg/ml) through MIC determination on solid medium (Middlebrook 7H10). rv0678 mutations were dynamic, while atpE mutations were fixed, once occurring. We present the following hypothesis for in vitro emergence of bedaquiline resistance: rv0678 mutations may be the first transient step in low-level resistance acquisition, followed by high-level resistance due to fixed atpE mutations.

scholarly journals Antimicrobial Resistance of Listeria monocytogenes Strains Isolated from Humans in France

2010 ◽  
Vol 54 (6) ◽  
pp. 2728-2731 ◽  
Author(s):  
A. Morvan ◽  
C. Moubareck ◽  
A. Leclercq ◽  
M. Hervé-Bazin ◽  
S. Bremont ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Antimicrobial Resistance ◽  
Resistant Strain ◽  
Temporal Evolution ◽  
Acquired Resistance ◽  
Mechanisms Of Resistance ◽  
Resistant Strains ◽  
High Level ◽  
Level Resistance ◽  
Microbiological Surveillance

ABSTRACT Susceptibility to antibiotics of 4,816 clinical L. monocytogenes strains isolated since 1926 was studied, and the temporal evolution of susceptibility to antibiotics was analyzed through several decades. The mechanisms of resistance in each resistant strain were studied. The prevalence of resistant strains was estimated at 1.27% among isolates from humans. Resistance to tetracyclines+ and fluoroquinolones was more common and has recently emerged. Although acquired resistance in clinical L. monocytogenes did not implicate clinically relevant antibiotics, the possibility of resistance gene transfers, the description of the first clinical isolate with high-level resistance to trimethoprim, and the recent increase in penicillin MICs up to 2 μg/ml reinforce the need for microbiological surveillance.

Inactivation of chloramphenicol by Gram-negative microorganisms

1968 ◽  
Vol 14 (8) ◽  
pp. 891-899 ◽  
Author(s):  
David Sompolinsky ◽  
Ruth Ziegler-Schlomowitz ◽  
Dora Herczog
Keyword(s):  
Escherichia Coli ◽  
Growth Medium ◽  
Minimal Medium ◽  
Resistance Factor ◽  
The Other ◽  
Gram Negative ◽  
Resistant Strains ◽  
Gram Negative Organisms ◽  
High Level ◽  
Level Resistance

Two derivative strains of Escherichia coli with high-level resistance to chloramphenicol, one carrying an episomal resistance factor and the other a chromosomal mutant, were both shown to be potent inactivators of the drug. When 1 mM chloramphenicol was added to an exponential culture in minimal medium, growth was halted until 85–90% of the drug was inactivated by acylation. At this state the drug was essentially monoacylated. During and after growth, esterification of the second alcoholic group occurred, though at a slower rate. Arylamines, in amounts up to 10% of chloramphenicol equivalents, were demonstrated in the growth medium after 1–3 days' incubation.With an acetateless mutant of Escherichia coli K12, carrying a resistance factor, it was shown that 5–6 moles of acetate was consumed for every mole of chloramphenicol acylated.Inactivation of chloramphenicol by Gram-negative organisms from infections in hospitalized patients was also examined. Among 103 strains susceptible to chloramphenicol, none produced considerable amounts of chloramphenicol esters. The same was the case with 14 resistant strains of Pseudomonas. Of 134 other resistant organisms examined, including strains of Escherichia, Proteus, Klebsiella, Salmonella, and Shigella, 133 were producers of chloramphenicol esters, and in most cases the drug was partly or entirely diacylated.

scholarly journals Genetic Characterization of Fluoroquinolone-Resistant Streptococcus pneumoniae Strains Isolated during Ciprofloxacin Therapy from a Patient with Bronchiectasis

2003 ◽  
Vol 47 (4) ◽  
pp. 1419-1422 ◽  
Author(s):  
Adela G. de la Campa ◽  
María-José Ferrandiz ◽  
Fe Tubau ◽  
Román Pallarés ◽  
Federico Manresa ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
Genetic Characterization ◽  
Susceptible Strain ◽  
Low Level ◽  
Resistant Strains ◽  
Resistant Mutants ◽  
High Level ◽  
Level Resistance

ABSTRACT Five Spain9V-3 Streptococcus pneumoniae strains were isolated from a patient with bronchiectasis who had received long-term ciprofloxacin therapy. One ciprofloxacin-susceptible strain was isolated before treatment, and four ciprofloxacin-resistant strains were isolated during treatment. The resistant strains were derived from the susceptible strain either by a parC mutation (low-level resistance) or by parC and gyrA mutations (high-level resistance). This study shows that ciprofloxacin therapy in a patient colonized by susceptible S. pneumoniae may select fluoroquinolone-resistant mutants.

scholarly journals Emergence of Quinolone-Resistant Bordetella pertussis in Japan

2009 ◽  
Vol 53 (7) ◽  
pp. 3147-3149 ◽  
Author(s):  
Masayuki Ohtsuka ◽  
Ken Kikuchi ◽  
Kenichiro Shimizu ◽  
Namiko Takahashi ◽  
Yuka Ono ◽  
...  
Keyword(s):  
Nalidixic Acid ◽  
Bordetella Pertussis ◽  
Resistant Strains ◽  
High Level ◽  
Level Resistance

ABSTRACT Six Bordetella pertussis strains isolated from children in Japan from 2004 to 2006 showed high-level resistance to nalidixic acid (NAL; MIC, >256 μg/ml) and decreased susceptibilities to fluoroquinolones. All of the NAL-resistant strains had the same D87G mutation in gyrA.

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