scholarly journals ampR Gene Mutations That Greatly Increase Class C β-Lactamase Activity in Enterobacter cloacae

2000 ◽  
Vol 44 (3) ◽  
pp. 561-567 ◽  
Author(s):  
Akio Kuga ◽  
Ryoichi Okamoto ◽  
Matsuhisa Inoue
Keyword(s):  
Escherichia Coli ◽  
Clinical Setting ◽  
Point Mutations ◽  
Gene Mutations ◽  
Enterobacter Cloacae ◽  
Class C ◽  
Selection Of

ABSTRACT The ampC and ampR genes ofEnterobacter cloacae GN7471 were cloned into pMW218 to yield pKU403. Four mutant plasmids derived from pKU403 (pKU404, pKU405, pKU406, and pKU407) were isolated in an AmpD mutant ofEscherichia coli ML4953 by selection with ceftazidime or aztreonam. The β-lactamase activities expressed by pKU404, pKU405, pKU406, and pKU407 were about 450, 75, 160, and 160 times higher, respectively, than that expressed by the original plasmid, pKU403. These mutant plasmids all carried point mutations in theampR gene. In pKU404 and pKU405, Asp-135 was changed to Asn and Val, respectively. In both pKU406 and pKU407, Arg-86 was changed to Cys. The ease of selection of AmpR mutations at a frequency of about 10−6 in this study strongly suggests that derepressed strains, such as AmpD or AmpR mutants, could frequently emerge in the clinical setting.

scholarly journals Altered Substrate Selection of the Melibiose Transporter (MelY) of Enterobacter cloacae Involving Point Mutations in Leu-88, Leu-91, and Ala-182 That Confer Enhanced Maltose Transport

2003 ◽  
Vol 185 (12) ◽  
pp. 3672-3677 ◽  
Author(s):  
Steven G. Shinnick ◽  
Stephanie A. Perez ◽  
Manuel F. Varela
Keyword(s):  
Escherichia Coli ◽  
Point Mutations ◽  
Enterobacter Cloacae ◽  
Substrate Selection ◽  
Coupled Transport ◽  
Wild Type ◽  
Transmembrane Segment ◽  
Maltose Transport ◽  
Site Classes ◽  
Selection Of

ABSTRACT We isolated mutants of Escherichia coli HS4006 containing the melibiose-H+ symporter (MelY) from Enterobacter cloacae that had enhanced fermentation on 1% maltose MacConkey plates. DNA sequencing revealed three site classes of mutations: L-88-P, L-91-P, and A-182-P. The mutants L-88-P and L-91-P had 3.6- and 5.1-fold greater maltose uptake than the wild type and enhanced apparent affinities for maltose. Energy-coupled transport was defective for melibiose accumulation, but detectable maltose accumulation for the mutants indicated that active transport is dependent upon the substrate transported through the carrier. We conclude that the residues Leu-88, Leu-91 (transmembrane segment 3 [TMS-3]), and Ala-182 (TMS-6) of MelY mediate sugar selection. These data represent the first MelY mutations that confer changes in sugar selection.

scholarly journals MUTATIONS IN radA ARE RESPONSIBLE FOR ACQUIRED RADIO-RESISTANCE IN AN Escherichia coli STRAIN

2021 ◽  
Author(s):  
David Alcántara Díaz ◽  
Jorge Humberto Serment Guerrero ◽  
Gerardo Aguirre Escalona ◽  
Jorge Tonatiuh Ayala Sumuano
Keyword(s):  
Escherichia Coli ◽  
Gamma Radiation ◽  
Uv Light ◽  
Point Mutations ◽  
Coli Strain ◽  
Normal Strain ◽  
Wild Type ◽  
Different Strains ◽  
Strain Ab1157 ◽  
Selection Of

When bacteria are exposed to chronic or cyclic irradiation with ultraviolet (UV) light, it is observed that their resistance to this agent is increased by the selection of advantageous mutations under those conditions. UV light produces different damages in DNA, the repair of which is necessary to maintain the integrity of the genome. However, some damages can lead to such mutations when they are not properly repaired. In an earlier work, five subcultures of a wild-type Escherichia coli strain (PQ30) were cyclically irradiated with UV and different strains resistant to UV light and gamma radiation were obtained. In a preliminary mapping, different genes involved in their resistance to radiation were identified. In one of these strains, designated as IN801, the radA gene, the product of which is involved in recombinational DNA repair, was identified. In this work, cells from another wild-type strain (AB1157) were transformed with a plasmid (pUC19) that carries the radA gene from either PQ30 or IN801, in order to establish whether the radio-resistant phenotype can be transferred to a normal strain. Only cells that received the IN801 radA gene showed increased resistance to UV and gamma radiation. Further radA sequencing showed that the gene of IN801 acquired two-point mutations that replace two amino acids in the RadA protein, which most likely changed its enzymatic activities. These results confirm that radA participates in the radiation resistance of IN801.

The selection of optimum fermentation condition for improved expression of sumo-il11 in escherichia coli

2015 ◽  
Vol 37 (1se) ◽  
Author(s):  
Nguyen Thi Quy ◽  
Duong Thu Huong ◽  
Dang Thi Ngoc Ha ◽  
Le Thi Thu Hong ◽  
Do Thi Huyen ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Fermentation Condition ◽  
Selection Of

Антимікробна резистентність провідних збудників інфекцій сечових шляхів у Києві (Україна)

2017 ◽  
Vol 1 (2) ◽  
pp. 48-60
Author(s):  
A.G. Salmanov ◽  
A.V. Rudenko
Keyword(s):  
Escherichia Coli ◽  
Pseudomonas Aeruginosa ◽  
Klebsiella Pneumoniae ◽  
Staphylococcus Epidermidis ◽  
Klebsiella Oxytoca ◽  
Enterobacter Aerogenes ◽  
Enterobacter Cloacae ◽  
Proteus Vulgaris ◽  
Providencia Rettgeri ◽  
E Coli

Мета роботи — вивчити резистентність до антибіотиків бактеріальних збудників інфекцій сечових шляхів (ІСШ), виділених у пацієнтів урологічного стаціонару в м. Києві. Матеріали і методи. Досліджено 1612 штамів бактерій, виділених із сечі хворих з ІСШ (цистит, уретрит, пієлонефрит), госпіталізованих в урологічне відділення ДУ «Інститут урології НАМН України» у м. Києві протягом 2016 р. Серед пацієнтів переважали жінки — 1201 (74,5 %). Вік хворих становив від 17 до 74 років. Для збору даних використано медичну документацію лікарні. Мікробіологічні дослідження виконано у лабораторії мікробіології ДУ «Інститут урології НАМН України». Аналізували результати культурального дослідження зразків сечі, зібраних за наявності клінічних ознак ІСШ. Дослідження клінічного матеріалу та інтерпретацію отриманих результатів проводили загальноприйнятими методами. Вивчено чутливість уропатогенів до 31 антибіотика дискодифузійним методом відповідно до рекомендацій Інституту клінічних та лабораторних стандартів США (Clinical and Laboratory Standards Institute (CLSI)). Результати та обговорення. Аналіз мікробного спектра сечі виявив домінування серед уропатогенів штамів Escherichia coli (32,0 %), Enterococcus faecalis (19,5 %), Klebsiella pneumoniae (10,9 %), Staphylococcus epidermidis (8,9 %), S. haemolyticus (6,5 %) та Pseudomonas aeruginosa (6,4 %). Частка Enterococcus faecium, Enterobacter aerogenes і Streptococcus viridans становила відповідно 2,5, 2,2 і 1,6 %, Enterobacter cloacae, Klebsiella oxytoca, Acinetobacter baumannii, Proteus vulgaris та Providencia rettgeri — менше 1,0 %. У більшості випадків (69,7 %) мікроорганізми виділено у монокультурі, у решті випадків — у мікробних асоціа- ціях. Високу резистентність до тестованих антибіотиків виявили штами E. aerogenes (45,1 %), E. cloacae (45,7 %), E. faecium (40,9 %), E. faecalis (40,7 %), E. coli (39,9 %), P. aeruginosa (34,0 %), K. pneumoniae (28,6 %). Найбільш активними до уропатогенів були іміпенем (E. coli — 87,6 %, P. aeruginosa — 75,7 %, E. cloacae — 67,3 %, E. aerogenes — 72,6 %, K. pneumoniae — 93,2 %), меропенем (E. coli — 89,1 %, P. aeruginosa — 76,7 %, K. pneumoniae — 82,6 %), лефлоцин (E. coli — 74,5 %, ентерококи — 78,7 %, P. aeruginosa — 76,7 %, E. cloacae — 73,9 %, E. aerogenes — 80,4 %, K. pneumoniae — 83,5 %), амоксицилін/клавуланат (ентерококи — 84,6 %), фурагін (ентерококи — 82,6 %), цефоперазон (K. pneumoniae — 89,2 %, P. aeruginosa — 73,8 %), цефтріаксон (K. pneumoniae — 80,1 %). Висновки. Антибіотикорезистентність збудників ІСШ — важлива терапевтична проблема. Найбільшою активністю до уропатогенів характеризуються іміпенем, меропенем, лефлоцин, амоксицилін/ клавуланат, фурагін, цефоперазон, цефтріаксон, які можна розглядати як препарат вибору для призначення стартової терапії ІСШ. Необхідно здійснювати постійний моніторинг за резистентністю до дії антибіотиків. Політику використання антибіотиків у кожному стаціонарі слід визначати залежно від локальних даних щодо резистентності до протимікробних препаратів.

scholarly journals Selection and co-selection of antibiotic resistances among Escherichia coli by antibiotic use in primary care: An ecological analysis

PLoS ONE ◽  
2019 ◽  
Vol 14 (6) ◽  
pp. e0218134 ◽  
Author(s):  
Koen B. Pouwels ◽  
Berit Muller-Pebody ◽  
Timo Smieszek ◽  
Susan Hopkins ◽  
Julie V. Robotham
Keyword(s):  
Escherichia Coli ◽  
Primary Care ◽  
Antibiotic Use ◽  
Ecological Analysis ◽  
Selection Of

scholarly journals L-Alanine Prototrophic Suppressors Emerge from L-Alanine Auxotroph through Stress-Induced Mutagenesis in Escherichia coli

2021 ◽  
Vol 9 (3) ◽  
pp. 472
Author(s):  
Harutaka Mishima ◽  
Hirokazu Watanabe ◽  
Kei Uchigasaki ◽  
So Shimoda ◽  
Shota Seki ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Complex ◽  
Spontaneous Mutation ◽  
Point Mutations ◽  
Whole Genome Analysis ◽  
E Coli ◽  
Clone Pair ◽  
Induced Mutagenesis ◽  
Isogenic Mutants

In Escherichia coli, L-alanine is synthesized by three isozymes: YfbQ, YfdZ, and AvtA. When an E. coli L-alanine auxotrophic isogenic mutant lacking the three isozymes was grown on L-alanine-deficient minimal agar medium, L-alanine prototrophic mutants emerged considerably more frequently than by spontaneous mutation; the emergence frequency increased over time, and, in an L-alanine-supplemented minimal medium, correlated inversely with L-alanine concentration, indicating that the mutants were derived through stress-induced mutagenesis. Whole-genome analysis of 40 independent L-alanine prototrophic mutants identified 16 and 18 clones harboring point mutation(s) in pyruvate dehydrogenase complex and phosphotransacetylase-acetate kinase pathway, which respectively produce acetyl coenzyme A and acetate from pyruvate. When two point mutations identified in L-alanine prototrophic mutants, in pta (D656A) and aceE (G147D), were individually introduced into the original L-alanine auxotroph, the isogenic mutants exhibited almost identical growth recovery as the respective cognate mutants. Each original- and isogenic-clone pair carrying the pta or aceE mutation showed extremely low phosphotransacetylase or pyruvate dehydrogenase activity, respectively. Lastly, extracellularly-added pyruvate, which dose-dependently supported L-alanine auxotroph growth, relieved the L-alanine starvation stress, preventing the emergence of L-alanine prototrophic mutants. Thus, L-alanine starvation-provoked stress-induced mutagenesis in the L-alanine auxotroph could lead to intracellular pyruvate increase, which eventually induces L-alanine prototrophy.

scholarly journals Comparison of Common Enrichment Broths Used in Diagnostic Laboratories for Shiga Toxin—Producing Escherichia coli

2021 ◽  
Vol 9 (3) ◽  
pp. 503
Author(s):  
Michael Bording-Jorgensen ◽  
Hannah Tyrrell ◽  
Colin Lloyd ◽  
Linda Chui
Keyword(s):  
Escherichia Coli ◽  
Shiga Toxin ◽  
Real Time Pcr ◽  
Acute Gastroenteritis ◽  
Diagnostic Testing ◽  
First Line ◽  
Gram Negative ◽  
Culture Independent ◽  
Surveillance Programs ◽  
Selection Of

Acute gastroenteritis caused by Shiga toxin-producing Escherichia coli (STEC) affects more than 4 million individuals in Canada. Diagnostic laboratories are shifting towards culture-independent diagnostic testing; however, recovery of STEC remains an important aspect of surveillance programs. The objective of this study was to compare common broth media used for the enrichment of STEC. Clinical isolates including O157:H7 as well as non-O157 serotypes were cultured in tryptic soy (TSB), MacConkey (Mac), and Gram-negative (GN) broths and growth was compared using culture on sheep’s blood agar and real-time PCR (qPCR). In addition, a selection of the same isolates was spiked into negative stool and enriched in the same three broths, which were then evaluated using culture on CHROMagarTM STEC agar and qPCR. TSB was found to provide the optimal enrichment for growth of isolates with and without stool. The results from this study suggest that diagnostic laboratories may benefit from enriching STEC samples in TSB as a first line enrichment instead of GN or Mac.

scholarly journals Use of tellurite for the selection of verocytotoxigenic Escherichia coli O157

1993 ◽  
Vol 39 (2) ◽  
pp. 155-158 ◽  
Author(s):  
P. M. Zadik ◽  
P. A. Chapman ◽  
C. A. Siddons
Keyword(s):  
Escherichia Coli ◽  
Escherichia Coli O157 ◽  
Selection Of

scholarly journals Molecular Basis of In Vivo Resistance to Sulfadoxine-Pyrimethamine in African Adult Patients Infected withPlasmodium falciparum Malaria Parasites

1998 ◽  
Vol 42 (7) ◽  
pp. 1811-1814 ◽  
Author(s):  
Leonardo K. Basco ◽  
Rachida Tahar ◽  
Pascal Ringwald
Keyword(s):  
Dihydrofolate Reductase ◽  
Point Mutations ◽  
Gene Mutations ◽  
Adult Patients ◽  
Wild Type ◽  
Dihydropteroate Synthase ◽  
Reductase Gene ◽  
Parasite Populations

ABSTRACT In vitro sulfadoxine and pyrimethamine resistance has been associated with point mutations in the dihydropteroate synthase and dihydrofolate reductase domains, respectively, but the in vivo relevance of these point mutations has not been well established. To analyze the correlation between genotype and phenotype, 10 Cameroonian adult patients were treated with sulfadoxine-pyrimethamine and followed up for 28 days. After losses to follow-up (n = 1) or elimination of DNA samples due to mixed parasite populations with pyrimethamine-sensitive and pyrimethamine-resistant profiles (n = 3), parasite genomic DNA from day 0 blood samples of six patients were analyzed by DNA sequencing. Three patients who were cured had isolates characterized by a wild-type or mutant dihydrofolate reductase gene (with one or two mutations) and a wild-type dihydropteroate synthase gene. Three other patients who failed to respond to sulfadoxine-pyrimethamine treatment carried isolates with triple dihydrofolate reductase gene mutations and either a wild-type or a mutant dihydropteroate synthase gene. Three dihydrofolate reductase gene codons (51, 59, and 108) may be reliable genetic markers that can accurately predict the clinical outcome of sulfadoxine-pyrimethamine treatment in Africa.

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