scholarly journals Analysis of Penicillin-Binding Protein Genes of Clinical Isolates of Streptococcus pneumoniae with Reduced Susceptibility to Amoxicillin

2002 ◽  
Vol 46 (8) ◽  
pp. 2349-2357 ◽  
Author(s):  
Mignon du Plessis ◽  
Edouard Bingen ◽  
Keith P. Klugman
Keyword(s):  
Sequence Divergence ◽  
Resistance Determinant ◽  
Penicillin Resistance ◽  
Donor Strain ◽  
Resistance Development ◽  
Complex Process ◽  
Recent Emergence ◽  
Stepwise Development ◽  
Amino Acid Mutations ◽  
High Level

ABSTRACT The recent emergence of pneumococcal isolates exhibiting an unusual resistance phenotype of higher amoxicillin MICs in relation to the penicillin MICs prompted an analysis of the pbp genes from three such strains isolated in France. For comparison, three amoxicillin-susceptible strains were included in the study. DNA sequence analysis of the pbp2x, pbp2b, and pbp1a genes revealed extensive sequence divergence in all six isolates compared to the sequences of the genes of penicillin-susceptible strain R6. With the exception of pbp2b, no amino acid mutations were unique to the resistant isolates. Transformation experiments with cloned pbp genes isolated from one of the resistant isolates demonstrated a stepwise development of amoxicillin resistance involving penicillin-binding proteins (PBPs) 2X, 2B, and 1A. Full resistance, equivalent to that of the donor strain, was achieved only when genomic DNA was transformed into R62x/2b/1a mutants, suggesting that full resistance development in this isolate is mediated by a non-PBP determinant. Moreover, the recently identified murMN resistance determinant does not appear to have any impact on resistance in this isolate. This determinant (from the French isolate) was, however, able to transform an R6 mutant harboring pbp2x, pbp2b, and pbp1a genes from a Hungarian clone with an extremely high level of penicillin resistance so that it had increased levels of penicillin resistance. These results indicate that the development of high-level β-lactam resistance is a complex process and that the involvement of MurMN in penicillin resistance appears to be dependent on specific mutations in PBPs 2X, 2B, and/or 1A. Furthermore, an additional (as yet unidentified) non-PBP-mediated resistance determinant is required for full resistance development in some pneumococci.

scholarly journals Mutations in Penicillin-Binding Protein (PBP) Genes and in Non-PBP Genes during Selection of Penicillin-Resistant Streptococcus gordonii

2006 ◽  
Vol 50 (12) ◽  
pp. 4053-4061 ◽  
Author(s):  
Marisa Haenni ◽  
Philippe Moreillon
Keyword(s):  
Penicillin Resistance ◽  
Streptococcus Gordonii ◽  
Intrinsic Resistance ◽  
Additional Increase ◽  
Resistance Development ◽  
Class A ◽  
Development Of Resistance ◽  
Class B ◽  
Resistant Mutants ◽  
High Level

ABSTRACT Penicillin resistance in Streptococcus spp. involves multiple mutations in both penicillin-binding proteins (PBPs) and non-PBP genes. Here, we studied the development of penicillin resistance in the oral commensal Streptococcus gordonii. Cyclic exposure of bacteria to twofold-increasing penicillin concentrations selected for a progressive 250- to 500-fold MIC increase (from 0.008 to between 2 and 4 μg/ml). The major MIC increase (≥35-fold) was related to non-PBP mutations, whereas PBP mutations accounted only for a 4- to 8-fold additional increase. PBP mutations occurred in class B PBPs 2X and 2B, which carry a transpeptidase domain, but not in class A PBP 1A, 1B, or 2A, which carry an additional transglycosylase domain. Therefore, we tested whether inactivation of class A PBPs affected resistance development in spite of the absence of mutations. Deletion of PBP 1A or 2A profoundly slowed down resistance development but only moderately affected resistance in already highly resistant mutants (MIC = 2 to 4 μg/ml). Thus, class A PBPs might facilitate early development of resistance by stabilizing penicillin-altered peptidoglycan via transglycosylation, whereas they might be less indispensable in highly resistant mutants which have reestablished a penicillin-insensitive cell wall-building machinery. The contribution of PBP and non-PBP mutations alone could be individualized in DNA transformation. Both PBP and non-PBP mutations conferred some level of intrinsic resistance, but combining the mutations synergized them to ensure high-level resistance (≥2 μg/ml). The results underline the complexity of penicillin resistance development and suggest that inhibition of transglycosylase might be an as yet underestimated way to interfere with early resistance development.

scholarly journals Genetic diversity and characteristics of high-level tigecycline resistance Tet(X) in Acinetobacter species

2020 ◽  
Vol 12 (1) ◽  
Author(s):  
Chong Chen ◽  
Chao-Yue Cui ◽  
Jun-Jun Yu ◽  
Qian He ◽  
Xiao-Ting Wu ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Bacterial Species ◽  
Sequence Divergence ◽  
Ecological Niches ◽  
Comparative Genomic ◽  
Phenotypic Variance ◽  
Evolutionary Analysis ◽  
Acinetobacter Species ◽  
Recent Emergence ◽  
High Level

Abstract Background The recent emergence and dissemination of high-level mobile tigecycline resistance Tet(X) challenge the clinical effectiveness of tigecycline, one of the last-resort therapeutic options for complicated infections caused by multidrug-resistant Gram-negative and Gram-positive pathogens. Although tet(X) has been found in various bacterial species, less is known about phylogeographic distribution and phenotypic variance of different genetic variants. Methods Herein, we conducted a multiregional whole-genome sequencing study of tet(X)-positive Acinetobacter isolates from human, animal, and their surrounding environmental sources in China. The molecular and enzymatic features of tet(X) variants were characterized by clonal expression, microbial degradation, reverse transcription, and gene transfer experiments, while the tet(X) genetic diversity and molecular evolution were explored by comparative genomic and Bayesian evolutionary analyses. Results We identified 193 tet(X)-positive isolates from 3846 samples, with the prevalence ranging from 2.3 to 25.3% in nine provinces in China. The tet(X) was broadly distributed in 12 Acinetobacter species, including six novel species firstly described here. Besides tet(X3) (n = 188) and tet(X4) (n = 5), two tet(X5) variants, tet(X5.2) (n = 36) and tet(X5.3) (n = 4), were also found together with tet(X3) or tet(X4) but without additive effects on tetracyclines. These tet(X)-positive Acinetobacter spp. isolates exhibited 100% resistance rates to tigecycline and tetracycline, as well as high minimum inhibitory concentrations to eravacycline (2–8 μg/mL) and omadacycline (8–16 μg/mL). Genetic analysis revealed that different tet(X) variants shared an analogous ISCR2-mediated transposon structure. The molecular evolutionary analysis indicated that Tet(X) variants likely shared the same common ancestor with the chromosomal monooxygenases that are found in environmental Flavobacteriaceae bacteria, but sequence divergence suggested separation ~ 9900 years ago (7887 BC), presumably associated with the mobilization of tet(X)-like genes through horizontal transfer. Conclusions Four tet(X) variants were identified in this study, and they were widely distributed in multiple Acinetobacter spp. strains from various ecological niches across China. Our research also highlighted the crucial role of ISCR2 in mobilizing tet(X)-like genes between different Acinetobacter species and explored the evolutionary history of Tet(X)-like monooxygenases. Further studies are needed to evaluate the clinical impact of these mobile tigecycline resistance genes.

scholarly journals Amino Acid Mutations Essential to Production of an Altered PBP 2X Conferring High-Level β-Lactam Resistance in a Clinical Isolate of Streptococcus pneumoniae

2005 ◽  
Vol 49 (11) ◽  
pp. 4622-4627 ◽  
Author(s):  
Anthony M. Smith ◽  
Keith P. Klugman
Keyword(s):  
Amino Acid ◽  
Laboratory Strain ◽  
Site Directed Mutagenesis ◽  
Resistance Determinant ◽  
Amino Acid Substitutions ◽  
Lactam Antibiotic ◽  
Amino Acid Mutations ◽  
High Level ◽  
The Impact ◽  
Level Resistance

ABSTRACT Altered penicillin-binding protein 2X (PBP 2X) is a primary β-lactam antibiotic resistance determinant and is essential to the development of penicillin and cephalosporin resistance in the pneumococcus. We have studied the importance for resistance of 23 amino acid substitutions located in the transpeptidase domain (TD) of PBP 2X from an isolate with high-level resistance, isolate 3191 (penicillin MIC, 16 μg/ml; cefotaxime MIC, 4 μg/ml). Strain R62X/2B/1A/mur (for which the MICs are as described for isolate 3191) was constructed by transforming laboratory strain R6 with all the necessary resistance determinants (altered PBPs 2X, 2B, and 1A and altered MurM) from isolate 3191. Site-directed mutagenesis was used to reverse amino acid substitutions in altered PBP 2X, followed by investigation of the impact of these reversions on resistance levels in R62X/2B/1A/mur. Of the 23 substitutions located in the TD of PBP 2X, reversals at six positions decreased the resistance levels in R62X/2B/1A/mur. Reversal of the Thr338Pro and Ile371Thr substitutions individually decreased the penicillin and cefotaxime MICs to 2 and 1 μg/ml, respectively, and individually displayed the greatest impact on resistance. To a lesser extent, reversal of the Leu364Phe, Ala369Val, Arg384Gly, and Tyr595Phe substitutions individually also decreased the penicillin and cefotaxime MICs. Reversal at all six positions collectively decreased both the penicillin and the cefotaxime MICs of R62X/2B/1A/mur to 0.06 μg/ml. This study confirms the essential role of altered PBP 2X as a resistance determinant. Our data reveal that, for isolate 3191, the six amino acid substitutions described above are collectively essential to the production of an altered PBP 2X required for high-level resistance to penicillin and cefotaxime.

scholarly journals Overexpression of the MtrC-MtrD-MtrE Efflux Pump Due to an mtrR Mutation Is Required for Chromosomally Mediated Penicillin Resistance in Neisseria gonorrhoeae

2002 ◽  
Vol 184 (20) ◽  
pp. 5619-5624 ◽  
Author(s):  
Wendy L. Veal ◽  
Robert A. Nicholas ◽  
William M. Shafer
Keyword(s):  
Neisseria Gonorrhoeae ◽  
Base Pair ◽  
Efflux Pump ◽  
Penicillin Resistance ◽  
Single Base ◽  
Base Pair Deletion ◽  
Resistance To Penicillin ◽  
Single Base Pair ◽  
High Level ◽  
Level Resistance

ABSTRACT The importance of the mtrCDE-encoded efflux pump in conferring chromosomally mediated penicillin resistance on certain strains of Neisseria gonorrhoeae was determined by using genetic derivatives of penicillin-sensitive strain FA19 bearing defined mutations (mtrR, penA, and penB) donated by a clinical isolate (FA6140) expressing high-level resistance to penicillin and antimicrobial hydrophobic agents (HAs). When introduced into strain FA19 by transformation, a single base pair deletion in the mtrR promoter sequence from strain FA6140 was sufficient to provide high-level resistance to HAs (e.g., erythromycin and Triton X-100) but only a twofold increase in resistance to penicillin. When subsequent mutations in penA and porIB were introduced from strain FA6140 into strain WV30 (FA19 mtrR) by transformation, resistance to penicillin increased incrementally up to a MIC of 1.0 μg/ml. Insertional inactivation of the gene (mtrD) encoding the membrane transporter component of the Mtr efflux pump in these transformant strains and in strain FA6140 decreased the MIC of penicillin by 16-fold. Genetic analyses revealed that mtrR mutations, such as the single base pair deletion in its promoter, are needed for phenotypic expression of penicillin and tetracycline resistance afforded by the penB mutation. As penB represents amino acid substitutions within the third loop of the outer membrane PorIB protein that modulate entry of penicillin and tetracycline, the results presented herein suggest that PorIB and the MtrC-MtrD-MtrE efflux pump act synergistically to confer resistance to these antibiotics.

Using Mobile Technologies in Education

2017 ◽  
Vol 13 (4) ◽  
pp. 77-90 ◽  
Author(s):  
Célio Gonçalo Cardoso Marques ◽  
António Manso ◽  
Ana Paula Ferreira ◽  
Felisbela Morgado
Keyword(s):  
Teaching And Learning ◽  
Reading Skills ◽  
Mobile Technologies ◽  
Ministry Of Education ◽  
Digital Repository ◽  
Learning To Read ◽  
Level Of Satisfaction ◽  
Complex Process ◽  
High Level ◽  
And Training

The acquisition of reading skills is decisive for the academic achievement of students. However, learning to read is a complex process. With this in mind, several attempts have been made to find new educational approaches to enhance students' reading motivation. Considering the enormous potential of ICT for education and training, we have developed a digital repository of teaching and learning materials and a multiplatform application that runs on mobile devices: Letrinhas. This information system was designed to promote the development of reading and to provide tools for monitoring and assessing reading skills against the curricular targets set by the Ministry of Education. Letrinhas was evaluated by specialists and users and a high level of satisfaction was observed among students and teachers as time and effort spent to consolidate reading is considerably reduced with this application. This evaluation also enabled to identify features that will be available in the future.

scholarly journals Genetics of high level penicillin resistance in clinical isolates ofStreptococcus pneumoniae

1995 ◽  
Vol 126 (3) ◽  
pp. 299-303 ◽  
Author(s):  
Victoria A Barcus ◽  
Kiran Ghanekar ◽  
Maggie Yeo ◽  
Tracey J Coffey ◽  
Christopher G Dowson
Keyword(s):  
Clinical Isolates ◽  
Penicillin Resistance ◽  
High Level

scholarly journals Modular action language

2015 ◽  
Vol 16 (2) ◽  
pp. 189-235 ◽  
Author(s):  
DANIELA INCLEZAN ◽  
MICHAEL GELFOND
Keyword(s):  
Logic Programming ◽  
Medium Size ◽  
Programming System ◽  
Problem Structuring ◽  
System Description ◽  
Action Languages ◽  
Special Cases ◽  
Action Language ◽  
Stepwise Development ◽  
High Level

AbstractThe paper introduces a new modular action language,${\mathcal ALM}$, and illustrates the methodology of its use. It is based on the approach of Gelfond and Lifschitz (1993,Journal of Logic Programming 17, 2–4, 301–321; 1998,Electronic Transactions on AI 3, 16, 193–210) in which a high-level action language is used as a front end for a logic programming system description. The resulting logic programming representation is used to perform various computational tasks. The methodology based on existing action languages works well for small and even medium size systems, but is not meant to deal with larger systems that requirestructuring of knowledge.$\mathcal{ALM}$is meant to remedy this problem. Structuring of knowledge in${\mathcal ALM}$is supported by the concepts ofmodule(a formal description of a specific piece of knowledge packaged as a unit),module hierarchy, andlibrary, and by the division of a system description of${\mathcal ALM}$into two parts:theoryandstructure. Atheoryconsists of one or more modules with a common theme, possibly organized into a module hierarchy based on adependency relation. It contains declarations of sorts, attributes, and properties of the domain together with axioms describing them.Structuresare used to describe the domain's objects. These features, together with the means for defining classes of a domain as special cases of previously defined ones, facilitate the stepwise development, testing, and readability of a knowledge base, as well as the creation of knowledge representation libraries.

scholarly journals Evaluation of Resistance Development in Bemisia tabaci Genn. (Homoptera: Aleyrodidae) in Cotton against Different Insecticides

Insects ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 996
Author(s):  
Muhammad Zaryab Khalid ◽  
Sohail Ahmed ◽  
Ibrahim Al-ashkar ◽  
Ayman EL Sabagh ◽  
Liyun Liu ◽  
...  
Keyword(s):  
Bemisia Tabaci ◽  
The Other ◽  
Resistance Development ◽  
Susceptible Population ◽  
Low Level ◽  
Development Of Resistance ◽  
Major Pest ◽  
Selection For ◽  
High Level ◽  
Very High

Cotton is a major crop of Pakistan, and Bemisia tabaci (Homoptera: Aleyrodidae) is a major pest of cotton. Due to the unwise and indiscriminate use of insecticides, resistance develops more readily in the whitefly. The present study was conducted to evaluate the resistance development in the whitefly against the different insecticides that are still in use. For this purpose, the whitefly population was selected with five concentrations of each insecticide, for five generations. At G1, compared with the laboratory susceptible population, a very low level of resistance was observed against bifenthrin, cypermethrin, acetamiprid, imidacloprid, thiamethoxam, nitenpyram, chlorfenapyr, and buprofezin with a resistance ratio of 3-fold, 2-fold, 1-fold, 4-fold, 3-fold, 3-fold, 3-fold, and 3-fold, respectively. However, the selection for five generations increased the resistance to a very high level against buprofezin (127-fold), and to a high level against imidacloprid (86-fold) compared with the laboratory susceptible population. While, a moderate level of resistance was observed against cypermethrin (34-fold), thiamethoxam (34-fold), nitenpyram (30-fold), chlorfenapyr (29-fold), and acetamiprid (21-fold). On the other hand, the resistance was low against bifenthrin (18-fold) after selection for five generations. A very low level of resistance against the field population of B. tabaci, at G1, showed that these insecticides are still effective, and thus can be used under the field conditions for the management of B. tabaci. However, the proper rotation of insecticides among different groups can help to reduce the development of resistance against insecticides.

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