Rifamycin-Resistant Mutation in E. coli: Effect of Rifamycin on DNA-Dependent RNA Polymerase and on R17 Phage Growth

1972 ◽  
Vol 50 (2) ◽  
pp. 128-135
Author(s):  
S. J. Igarashi
Keyword(s):  
Rna Polymerase ◽  
Template Molecule ◽  
E Coli ◽  
Resistant Strains ◽  
Resistant Mutants ◽  
Natural Mutation ◽  
Male Specific ◽  
Phage Growth ◽  
Resistant Mutation ◽  
Selection Of

Rifamycin-resistant mutants in E. coli, K12, Hfr strain, were isolated without mutagenic treatment. The frequency of natural mutation of this type appeared to be approximately 10−9. Selection of resistant strains was effected by plating 109 cells on agar plates containing 50 μg of rifamycin per milliliter. A total of 11 strains resistant to rifamycin thus isolated remained Hfr and, in the presence of rifamycin, permitted the growth of the RNA-containing, male specific coliphage R17, which is sensitive to rifamycin in a wild-type E. coli. DNA-dependent RNA polymerase was prepared from these resistant mutants and examined for sensitivity toward rifamycin and other antibiotics. It was found that the RNA polymerase of the resistant strain is indeed resistant to rifamycin. However, both rifamycin-resistant and -sensitive enzymes are inhibited by the other three antibiotics (acridine orange, ethidium bromide, actinomycin D), which are known to interact with the template molecule.

scholarly journals Antipneumococcal Activities of Two Novel Macrolides, GW 773546 and GW 708408, Compared with Those of Erythromycin, Azithromycin, Clarithromycin, Clindamycin, and Telithromycin

2004 ◽  
Vol 48 (11) ◽  
pp. 4103-4112 ◽  
Author(s):  
Vlatka Matic ◽  
Klaudia Kosowska ◽  
Bulent Bozdogan ◽  
Linda M. Kelly ◽  
Kathy Smith ◽  
...  
Keyword(s):  
Ribosomal Protein ◽  
Protein Sequence ◽  
Single Step ◽  
23S Rrna ◽  
Susceptible Parent ◽  
Rrna Sequence ◽  
Resistant Strains ◽  
Resistant Mutants ◽  
Rrna Sequences ◽  
Selection Of

ABSTRACT The MICs of GW 773546, GW 708408, and telithromycin for 164 macrolide-susceptible and 161 macrolide-resistant pneumococci were low. The MICs of GW 773546, GW 708408, and telithromycin for macrolide-resistant strains were similar, irrespective of the resistance genotypes of the strains. Clindamycin was active against all macrolide-resistant strains except those with erm(B) and one strain with a 23S rRNA mutation. GW 773546, GW 708408, and telithromycin at two times their MICs were bactericidal after 24 h for 7 to 8 of 12 strains. Serial passages of 12 strains in the presence of sub-MICs yielded 54 mutants, 29 of which had changes in the L4 or L22 protein or the 23S rRNA sequence. Among the macrolide-susceptible strains, resistant mutants developed most rapidly after passage in the presence of clindamycin, GW 773546, erythromycin, azithromycin, and clarithromycin and slowest after passage in the presence of GW 708408 and telithromycin. Selection of strains for which MICs were ≥0.5 μg/ml from susceptible parents occurred only with erythromycin, azithromycin, clarithromycin, and clindamycin; 36 resistant clones from susceptible parent strains had changes in the sequences of the L4 or L22 protein or 23S rRNA. No mef(E) strains yielded resistant clones after passage in the presence of erythromycin and azithromycin. Selection with GW 773546, GW 708408, telithromycin, and clindamycin in two mef(E) strains did not raise the erythromycin, azithromycin, and clarithromycin MICs more than twofold. There were no change in the ribosomal protein (L4 or L22) or 23S rRNA sequences for 15 of 18 mutants selected for macrolide resistance; 3 mutants had changes in the L22-protein sequence. GW 773546, GW 708408, and telithromycin selected clones for which MICs were 0.03 to >2.0 μg/ml. Single-step studies showed mutation frequencies <5.0 × 10−10 to 3.5 × 10−7 for GW 773546, GW 708408, and telithromycin for macrolide-susceptible strains and 1.1 × 10−7 to >4.3 × 10−3 for resistant strains. The postantibiotic effects of GW 773546, GW 708408, and telithromycin were 2.4 to 9.8 h.

scholarly journals In Vitro Activity of CEM-101 against Streptococcus pneumoniae and Streptococcus pyogenes with Defined Macrolide Resistance Mechanisms

2009 ◽  
Vol 54 (1) ◽  
pp. 230-238 ◽  
Author(s):  
Pamela McGhee ◽  
Catherine Clark ◽  
Klaudia M. Kosowska-Shick ◽  
Kensuke Nagai ◽  
Bonifacio Dewasse ◽  
...  
Keyword(s):  
Streptococcus Pyogenes ◽  
Bacterial Species ◽  
Resistance Mechanisms ◽  
Macrolide Resistance ◽  
23S Rrna ◽  
Resistant Strains ◽  
Resistant Mutants ◽  
The One ◽  
Selection Of

ABSTRACT CEM-101 had MIC ranges of 0.002 to 0.016 μg/ml against macrolide-susceptible pneumococci and 0.004 to 1 μg/ml against macrolide-resistant phenotypes. Only 3 strains with erm(B), with or without mef(A), had CEM-101 MICs of 1 μg/ml, and 218/221 strains had CEM-101 MICs of ≤0.5 μg/ml. CEM-101 MICs were as much as 4-fold lower than telithromycin MICs against all strains. For Streptococcus pyogenes, CEM-101 MICs ranged from 0.008 to 0.03 μg/ml against macrolide-susceptible strains and from 0.015 to 1 μg/ml against macrolide-resistant strains. Against erm(B) strains, erythromycin, azithromycin, and clarithromycin MICs were 32 to >64 μg/ml, while 17/19 strains had telithromycin MICs of 4 to 16 μg/ml; CEM-101 MICs were 0.015 to 1 μg/ml. By comparison, erm(A) and mef(A) strains had CEM-101 MICs of 0.015 to 0.5 μg/ml, clindamycin and telithromycin MICs of ≤1 μg/ml, and erythromycin, azithromycin, and clarithromycin MICs of 0.5 to >64 μg/ml. Pneumococcal multistep resistance studies showed that although CEM-101 yielded clones with higher MICs for all eight strains tested, seven of eight strains had clones with CEM-101 MICs that rose from 0.004 to 0.03 μg/ml (parental strains) to 0.06 to 0.5 μg/ml (resistant clones); for only one erm(B) mef(A) strain with a parental MIC of 1 μg/ml was there a resistant clone with a MIC of 32 μg/ml, with no detectable mutations in the L4, L22, or 23S rRNA sequence. Among two of five S. pyogenes strains tested, CEM-101 MICs rose from 0.03 to 0.25 μg/ml, and only for the one strain with erm(B) did CEM-101 MICs rise from 1 to 8 μg/ml, with no changes occurring in any macrolide resistance determinant. CEM-101 had low MICs as well as low potential for the selection of resistant mutants, independent of bacterial species or resistance phenotypes in pneumococci and S. pyogenes.

Latent infections in avian malaria in relation to the production of drug-resistance

Parasitology ◽  
1951 ◽  
Vol 41 (1-2) ◽  
pp. 110-116 ◽  
Author(s):  
Elspeth W. McConnachie
Keyword(s):  
Drug Resistance ◽  
Avian Malaria ◽  
Latent Infection ◽  
Prolonged Treatment ◽  
Reproduction Rate ◽  
Latent Infections ◽  
Once Daily ◽  
Resistant Strains ◽  
Resistant Mutants ◽  
Selection Of

1. No resistance to paludrine or to sulphadiazine was obtained after treating latent infections of Plasmodium gallinaceum in chickens with twice daily doses of 20 mg./20 g. of sulphadiazine over periods of 171, 178 and 190 days.2. No resistance to paludrine was obtained after treating a latent infection of P. relictum in a canary over a period of 1 year with doses of paludrine increasing from 0·05 mg./20 g. once daily to 1·0 mg./ 20 g. twice daily.3. It is considered that if drug-resistance arises by mutation and selection, then resistance should arise more readily when a large number of rapidly multiplying parasites is treated with a drug than when the population treated is small, with a low reproduction rate, i.e. the failure to obtain resistant strains of malaria by prolonged treatment of latent infections with large amounts of drug, lends support to the theory of the origin of resistant strains of malaria by the selection of resistant mutants.

scholarly journals Development of antibacterial compounds that constrain evolutionary pathways to resistance

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Yanmin Zhang ◽  
Sourav Chowdhury ◽  
João V Rodrigues ◽  
Eugene I Shakhnovich
Keyword(s):  
Dihydrofolate Reductase ◽  
Experimental Approach ◽  
Whole Genome ◽  
Bacterial Protein ◽  
Antibacterial Compounds ◽  
E Coli ◽  
Resistant Strains ◽  
Evolutionary Pathways ◽  
Resistant Mutants

Antibiotic resistance is a worldwide challenge. A potential approach to block resistance is to simultaneously inhibit WT and known escape variants of the target bacterial protein. Here we applied an integrated computational and experimental approach to discover compounds that inhibit both WT and trimethoprim (TMP) resistant mutants of E. coli dihydrofolate reductase (DHFR). We identified a novel compound (CD15-3) that inhibits WT DHFR and its TMP resistant variants L28R, P21L and A26T with IC50 50-75 µM against WT and TMP-resistant strains. Resistance to CD15-3 was dramatically delayed compared to TMP in in vitro evolution. Whole genome sequencing of CD15-3 resistant strains showed no mutations in the target folA locus. Rather, gene duplication of several efflux pumps gave rise to weak (about twofold increase in IC50) resistance against CD15-3. Altogether, our results demonstrate the promise of strategy to develop evolution drugs - compounds which constrain evolutionary escape routes in pathogens.

scholarly journals Development of evolution drugs - antibacterial compounds that block pathways to resistance

2020 ◽  
Author(s):  
Yanmin Zhang ◽  
Sourav Chowdhury ◽  
João V. Rodrigues ◽  
Eugene Shakhnovich
Keyword(s):  
Antibiotic Resistance ◽  
Dihydrofolate Reductase ◽  
Experimental Approach ◽  
Whole Genome ◽  
Bacterial Protein ◽  
Antibacterial Compounds ◽  
E Coli ◽  
Resistant Strains ◽  
Resistant Mutants

AbstractAntibiotic resistance is a worldwide challenge. A potential approach to block resistance is to simultaneously inhibit WT and known escape variants of the target bacterial protein. Here we applied an integrated computational and experimental approach to discover compounds that inhibit both WT and trimethoprim (TMP) resistant mutants of E. coli dihydrofolate reductase (DHFR). We identified a novel compound (CD15-3) that inhibits WT DHFR and its TMP resistant variants L28R, P21L and A26T with IC50 50-75 μM against WT and TMP-resistant strains. Resistance to CD15-3 was dramatically delayed compared to TMP in in vitro evolution. Whole genome sequencing of CD15-3 resistant strains showed no mutations in the target folA locus. Rather, gene duplication of several efflux pumps gave rise to weak (about twofold increase in IC50) resistance against CD15-3. Altogether, our results demonstrate the promise of strategy to develop evolution drugs - compounds which block evolutionary escape routes in pathogens.

scholarly journals Effects of oxygen on aerosol survival of radiation sensitive and resistant strains ofEscherichia coliB

1971 ◽  
Vol 69 (4) ◽  
pp. 661-672 ◽  
Author(s):  
C. S. Cox ◽  
M. C. Bondurant ◽  
M. T. Hatch
Keyword(s):  
Escherichia Coli ◽  
Relative Humidity ◽  
Metabolic Activity ◽  
Radiation Sensitivity ◽  
The Other ◽  
E Coli ◽  
Radiation Induced ◽  
Resistant Strains ◽  
Resistant Mutants ◽  
Survival In Air

SUMMARYThe aerosol survivals in air and nitrogen of radiation sensitive and resistant mutants ofEscherichia coliB have been determined with logarithmic and resting phase bacteria. No consistent correlation was found between radiation sensitivity and aerosol sensitivity in the strains tested. Hence, the phenotypes Fil Her Exr, which determine sensitivity to radiation, do not influence aerosol survival, i.e. these known mechanisms which repair radiation-induced damage do not operate in aerosol stressedE. coli. In all cases the survival in air was less than that in nitrogen particularly so forE. coliBs-1. The effect is explained in terms of a toxic action of oxygen. Comparison of survival of log and resting phase bacteria show that log phase cells are less aerosol stable than are resting phase cells. The ability to synthesize DNA in bacteria collected from the aerosol was less than in control unstressed bacteria, and this effect was independent of the presence of oxygen. Reduced ability to synthesize DNA could have been caused by reduced metabolic activity. It is shown that two different death mechanisms occur simultaneously in aerosols at low relative humidity. One mechanism is oxygen dependent and the other oxygen independent. The former was not through a decrease in metabolic activity, whereas the latter could be.

scholarly journals Molecular Genetic and Structural Modeling Studies of Staphylococcus aureus RNA Polymerase and the Fitness of Rifampin Resistance Genotypes in Relation to Clinical Prevalence

2006 ◽  
Vol 50 (1) ◽  
pp. 298-309 ◽  
Author(s):  
A. J. O'Neill ◽  
T. Huovinen ◽  
C. W. G. Fishwick ◽  
I. Chopra
Keyword(s):  
Staphylococcus Aureus ◽  
Rna Polymerase ◽  
Molecular Genetic ◽  
Fitness Costs ◽  
Novel Mutations ◽  
Resistant Strains ◽  
Rifampin Resistance ◽  
First Time ◽  
Selection Of

ABSTRACT The adaptive and further evolutionary responses of Staphylococcus aureus to selection pressure with the antibiotic rifampin have not been explored in detail. We now present a detailed analysis of these systems. The use of rifampin for the chemotherapy of infections caused by S. aureus has resulted in the selection of mutants with alterations within the β subunit of the target enzyme, RNA polymerase. Using a new collection of strains, we have identified numerous novel mutations in the β subunits of both clinical and in vitro-derived resistant strains and established that additional, undefined mechanisms contribute to expression of rifampin resistance in clinical isolates of S. aureus. The fitness costs associated with rifampin resistance genotypes were found to have a significant influence on their clinical prevalence, with the most common clinical genotype (H481N, S529L) exhibiting no fitness cost in vitro. Intragenic mutations which compensate for the fitness costs associated with rifampin resistance in clinical strains of S. aureus were identified for the first time. Structural explanations for rifampin resistance and the loss of fitness were obtained by molecular modeling of mutated RNA polymerase enzymes.

scholarly journals Strong In Vitro Activities of Two New Rifabutin Analogs against Multidrug-Resistant Mycobacterium tuberculosis

2010 ◽  
Vol 54 (12) ◽  
pp. 5363-5365 ◽  
Author(s):  
Ana-Belén García ◽  
Juan J. Palacios ◽  
María-Jesús Ruiz ◽  
José Barluenga ◽  
Fernando Aznar ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Rna Polymerase ◽  
Molecular Dynamic ◽  
Multidrug Resistant ◽  
Dynamic Studies ◽  
Resistant Strains ◽  
Selection Of

ABSTRACT Two new rifabutin analogs, RFA-1 and RFA-2, show high in vitro antimycobacterial activities against Mycobacterium tuberculosis. MIC values of RFA-1 and RFA-2 were ≤0.02 μg/ml against rifamycin-susceptible strains and 0.5 μg/ml against a wide selection of multidrug-resistant strains, compared to ≥50 μg/ml for rifampin and 10 μg/ml for rifabutin. Molecular dynamic studies indicate that the compounds may exert tighter binding to mutants of RNA polymerase that have adapted to the rifamycins.

Free-living and symbiotic characteristics of chlorate resistant mutants of Rhizobium japonicum

1980 ◽  
Vol 26 (3) ◽  
pp. 338-342 ◽  
Author(s):  
Laura de Vasconcelos ◽  
Llonas Miller ◽  
Carlos A. Neyra
Keyword(s):  
Nitrate Reductase ◽  
Parent Strain ◽  
Rhizobium Japonicum ◽  
Free Living ◽  
Chlorate Resistance ◽  
Soybean Seedlings ◽  
Resistant Strains ◽  
Resistant Mutants ◽  
Selection Of ◽  
Better Than

This work investigated the usefulness of chlorate resistance as a method for the selection of nitrate reductase negative (NR−) strains from Rhizobium japonicum (61A76) and evaluated the symbiotic characteristics of these strains. Chlorate resistant strains were selected from populations seeded on CS 7 agar containing 10 or 20 mM KClO3 and incubated in 2% air – 98% N2–CO2 (95:5).Over 200 resistant strains were isolated, 58% of which lacked the dissimilatory nitrate reductase. In 12 selected isolates, some strains had also lost the assimilatory nitrate reductase, but all retained hydrogenase activity.Chlorate resistant strains inoculated to soybean seedlings were equal to or better than the parent strain in terms of nodule mass and acetylene reduction. Those strains lacking both assimilatory and dissimilatory nitrate reductase showed the best symbiotic characteristics, suggesting that chlorate resistance in R. japonicum could be a useful method for the selection of strains with superior nitrogen-fixing characteristics.

scholarly journals Fluoroquinolone Action against Mycobacteria: Effects of C-8 Substituents on Growth, Survival, and Resistance

1998 ◽  
Vol 42 (11) ◽  
pp. 2978-2984 ◽  
Author(s):  
Yuzhi Dong ◽  
Chen Xu ◽  
Xilin Zhao ◽  
John Domagala ◽  
Karl Drlica
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Bacterial Species ◽  
Resistant Mutant ◽  
Methoxyl Group ◽  
Bacteriostatic Activity ◽  
Dna Breaks ◽  
Lethal Action ◽  
Resistant Strains ◽  
Resistant Mutants ◽  
Selection Of

ABSTRACT Fluoroquinolones trap gyrase on DNA as bacteriostatic complexes from which lethal DNA breaks are released. Substituents at the C-8 position increase activities of N-1-cyclopropyl fluoroquinolones against several bacterial species. In the present study, a C-8-methoxyl group improved bacteriostatic action againstgyrA (gyrase-resistant) strains ofMycobacterium tuberculosis and M. bovis BCG. It also enhanced lethal action against gyrase mutants of M. bovis BCG. When cultures of M. smegmatis, M. bovis BCG, and M. tuberculosis were challenged with a C-8-methoxyl fluoroquinolone, no resistant mutant was recovered under conditions in which more than 1,000 mutants were obtained with a C-8-H control. A C-8-bromo substituent also increased bacteriostatic and lethal activities against a gyrA mutant of M. bovisBCG. When lethal activity was normalized to bacteriostatic activity, the C-8-methoxyl compound was more bactericidal than its C-8-H control, while the C-8-bromo fluoroquinolone was not. The C-8-methoxyl compound was also found to be more effective than the C-8-bromo fluoroquinolone at reducing selection of resistant mutants when each was compared to a C-8-H control over a broad concentration range. These data indicate that a C-8-methoxyl substituent, which facilitates attack of first-step gyrase mutants, may help make fluoroquinolones effective antituberculosis agents.

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