scholarly journals Topoisomerase Mutations Associated with In Vitro Selection of Resistance to Moxifloxacin in Streptococcus pneumoniae

2002 ◽  
Vol 46 (8) ◽  
pp. 2712-2715 ◽  
Author(s):  
Serge Houssaye ◽  
Laurent Gutmann ◽  
Emmanuelle Varon
Keyword(s):  
Streptococcus Pneumoniae ◽  
In Vitro Selection ◽  
Second Step ◽  
Wild Type ◽  
Topoisomerase Iv ◽  
Selection Step ◽  
Gyra Mutation ◽  
Selection Of ◽  
Selection Of Resistance

ABSTRACT We analyzed the frequencies of selection, the order of acquisition, and the mutations selected on moxifloxacin in two wild-type pneumococcal strains, R6 and 5714. The first selection step showed either a single GyrA mutation or no mutation in any of the quinolone resistance-determining regions. Second-step mutants selected had either a second mutation in ParC or in ParE. Moxifloxacin could belong to these fluoroquinolones, which preferentially target GyrA though probably acting equally through both gyrase and topoisomerase IV.

scholarly journals In Vitro Selection of Resistance to Four β-Lactams and Azithromycin in Streptococcus pneumoniae

1998 ◽  
Vol 42 (11) ◽  
pp. 2914-2918 ◽  
Author(s):  
Glenn A. Pankuch ◽  
Shane A. Jueneman ◽  
Todd A. Davies ◽  
Michael R. Jacobs ◽  
Peter C. Appelbaum
Keyword(s):  
Streptococcus Pneumoniae ◽  
In Vitro Selection ◽  
Antimicrobial Agents ◽  
Penicillin G ◽  
Resistance Selection ◽  
Resistant Strains ◽  
Selection Of ◽  
Selection Of Resistance

ABSTRACT Selection of resistance to amoxicillin (with or without clavulanate), cefaclor, cefuroxime, and azithromycin among six penicillin G- and azithromycin-susceptible pneumococcal strains and among four strains with intermediate penicillin sensitivities (azithromycin MICs, 0.125 to 4 μg/ml) was studied by performing 50 sequential subcultures in medium with sub-MICs of these antimicrobial agents. For only one of the six penicillin-susceptible strains did subculturing in medium with amoxicillin (with or without clavulanate) lead to an increased MIC, with the MIC rising from 0.008 to 0.125 μg/ml. Five of the six penicillin-susceptible strains showed increased azithromycin MICs (0.5 to >256.0 μg/ml) after 17 to 45 subcultures. Subculturing in medium with cefaclor did not affect the cefaclor MICs of three strains but and led to increased cefaclor MICs (from 0.5 to 2.0 to 4.0 μg/ml) for three of the six strains, with MICs of other β-lactams rising 1 to 3 twofold dilutions. Subculturing in cefuroxime led to increased cefuroxime MICs (from 0.03 to 0.06 μg/ml to 0.125 to 0.5 μg/ml) for all six strains without significantly altering the MICs of other β-lactams, except for one strain, which developed an increased cefaclor MIC. Subculturing in azithromycin did not affect β-lactam MICs. Subculturing of the four strains with decreased penicillin susceptibility in amoxicillin (with or without clavulanate) or cefuroxime did not select for β-lactam resistance. Subculturing of one strain in cefaclor led to an increase in MIC from 0.5 to 2.0 μg/ml after 19 passages. In contrast to strains that were initially azithromycin susceptible, which required >10 subcultures for resistance selection, three of four strains with azithromycin MICs of 0.125 to 4.0 μg/ml showed increased MICs after 7 to 13 passages, with the MICs increasing to 16 to 32 μg/ml. All azithromycin-resistant strains were clarithromycin resistant. With the exception of strains that contained mefE at the onset, no strains that developed resistance to azithromycin containedermB or mefE, genes that have been found in macrolide-resistant pneumococci obtained from clinic patients.

scholarly journals In Vitro Activities of Novel Nonfluorinated Quinolones PGE 9262932 and PGE 9509924 against Clinical Isolates of Staphylococcus aureus and Streptococcus pneumoniae with Defined Mutations in DNA Gyrase and Topoisomerase IV

2002 ◽  
Vol 46 (6) ◽  
pp. 1651-1657 ◽  
Author(s):  
Mark E. Jones ◽  
Ian A. Critchley ◽  
James A. Karlowsky ◽  
Renée S. Blosser-Middleton ◽  
Franz-Josef Schmitz ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Streptococcus Pneumoniae ◽  
Dna Gyrase ◽  
Quinolone Resistance ◽  
Clinical Isolates ◽  
Wild Type ◽  
Topoisomerase Iv ◽  
Selection Of

ABSTRACT Two 8-methoxy nonfluorinated quinolones (NFQs), PGE 9262932 and PGE 9509924, were tested against contemporary clinical isolates of Staphylococcus aureus (n = 122) and Streptococcus pneumoniae (n = 69) with genetically defined quinolone resistance-determining regions (QRDRs). For S. aureus isolates with wild-type (WT) sequences at the QRDRs, the NFQs demonstrated activities 4- to 32-fold more potent (MICs at which 90% of isolates are inhibited [MIC90s], 0.03 μg/ml) than those of moxifloxacin (MIC90, 0.12 μg/ml), gatifloxacin (MIC90, 0.25 μg/ml), levofloxacin (MIC90, 0.25 μg/ml), and ciprofloxacin (MIC90, 1 μg/ml). Against S. pneumoniae isolates with WT sequences at gyrA and parC, the NFQs PGE 9262932 (MIC90, 0.03 μg/ml) and PGE 9509924 (MIC90, 0.12 μg/ml) were 8- to 64-fold and 2- to 16-fold more potent, respectively, than moxifloxacin (MIC90, 0.25 μg/ml), gatifloxacin (MIC90, 0.5 μg/ml), levofloxacin (MIC90, 2 μg/ml), and ciprofloxacin (MIC90, 2 μg/ml). The MICs of all agents were elevated for S. aureus isolates with alterations in GyrA (Glu88Lys or Ser84Leu) and GrlA (Ser80Phe) and S. pneumoniae isolates with alterations in GyrA (Ser81Phe or Ser81Tyr) and ParC (Ser79Phe or Lys137Asn). Fluoroquinolone MICs for S. aureus strains with double alterations in GyrA combined with double alterations in GrlA were ≥32 μg/ml, whereas the MICs of the NFQs for strains with these double alterations were 4 to 8 μg/ml. The PGE 9262932 and PGE 9509924 MICs for the S. pneumoniae isolates did not exceed 0.5 and 1 μg/ml, respectively, even for isolates with GyrA (Ser81Phe) and ParC (Ser79Phe) alterations, for which levofloxacin MICs were >16 μg/ml. No difference in the frequency of selection of mutations (<10−8 at four times the MIC) in wild-type or first-step mutant isolates of S. aureus or S. pneumoniae was detected for the two NFQs. On the basis of their in vitro activities, these NFQ agents show potential for the treatment of infections caused by isolates resistant to currently available fluoroquinolones.

The Effects of Shock Vancomycin Concentrations on the Formation of Heteroresistance in Staphylococcus aureus

2020 ◽  
Vol 65 (9-10) ◽  
pp. 3-7
Author(s):  
V. V. Gostev ◽  
Yu. V. Sopova ◽  
O. S. Kalinogorskaya ◽  
M. E. Velizhanina ◽  
I. V. Lazareva ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
In Vitro Selection ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
High Concentration ◽  
Short Term ◽  
High Concentrations ◽  
Selection Of ◽  
Selection Of Resistance ◽  
Test Cultures

Glycopeptides are the basis of the treatment of infections caused by MRSA (Methicillin-Resistant Staphylococcus aureus). Previously, it was demonstrated that antibiotic tolerant phenotypes are formed during selection of resistance under the influence of high concentrations of antibiotics. The present study uses a similar in vitro selection model with vancomycin. Clinical isolates of MRSA belonging to genetic lines ST8 and ST239, as well as the MSSA (ATCC29213) strain, were included in the experiment. Test isolates were incubated for five hours in a medium with a high concentration of vancomycin (50 μg/ml). Test cultures were grown on the medium without antibiotic for 18 hours after each exposure. A total of ten exposure cycles were performed. Vancomycin was characterized by bacteriostatic action; the proportion of surviving cells after exposure was 70–100%. After selection, there was a slight increase in the MIC to vancomycin (MIC 2 μg/ml), teicoplanin (MIC 1.5–3 μg/ml) and daptomycin (MIC 0.25–2 μg/ml). According to the results of PAP analysis, all strains showed an increase in the area under curve depending on the concentration of vancomycin after selection, while a heteroresistant phenotype (with PAP/AUC 0.9) was detected in three isolates. All isolates showed walK mutations (T188S, D235N, E261V, V380I, and G223D). Exposure to short-term shock concentrations of vancomycin promotes the formation of heteroresistance in both MRSA and MSSA. Formation of VISA phenotypes is possible during therapy with vancomycin.

In vitro selection of resistance to sofosbuvir in HCV replicons of genotype 1 to 6

2017 ◽  
Vol 22 (7) ◽  
pp. 587-597 ◽  
Author(s):  
Simin Xu ◽  
Brian Doehle ◽  
Sonal Rajyaguru ◽  
Bin Han ◽  
Ona Barauskas ◽  
...  
Keyword(s):  
In Vitro Selection ◽  
Genotype 1 ◽  
Selection Of ◽  
Selection Of Resistance

IN VITRO SELECTION OF FLUOROQUINOLONE-RESISTANT NEISSERIA GONORRHOEAE HARBORING ALTERATIONS IN DNA GYRASE AND TOPOISOMERASE IV

2000 ◽  
pp. 847-851
Author(s):  
MITSURU YASUDA ◽  
HIDEYUKI FUKUDA ◽  
SHIGEAKI YOKOI ◽  
SATOSHI ISHIHARA ◽  
YUKIMICHI KAWADA ◽  
...  
Keyword(s):  
Neisseria Gonorrhoeae ◽  
In Vitro Selection ◽  
Dna Gyrase ◽  
Topoisomerase Iv ◽  
Selection Of

scholarly journals In vitro selection of mutants of Streptococcus pneumoniae resistant to macrolides and linezolid: relationship with susceptibility to penicillin G or macrolides

2005 ◽  
Vol 56 (4) ◽  
pp. 633-642 ◽  
Author(s):  
H. Carsenti-Dellamonica ◽  
M. Galimand ◽  
F. Vandenbos ◽  
C. Pradier ◽  
P. M. Roger ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
In Vitro Selection ◽  
Penicillin G ◽  
Selection Of

In vitro selection of Phytomonas serpens cells resistant to the calpain inhibitor MDL28170: alterations in fitness and expression of the major peptidases and efflux pumps

Parasitology ◽  
2017 ◽  
Vol 145 (3) ◽  
pp. 355-370 ◽  
Author(s):  
SIMONE S. C. OLIVEIRA ◽  
INÊS C. GONÇALVES ◽  
VITOR ENNES-VIDAL ◽  
ANGELA H. C. S. LOPES ◽  
RUBEM F. S. MENNA-BARRETO ◽  
...  
Keyword(s):  
In Vitro Selection ◽  
Oncopeltus Fasciatus ◽  
Calpain Inhibitor ◽  
Insect Vector ◽  
Peptidase Activity ◽  
Wild Type ◽  
Calcium Dependent ◽  
Calpain Inhibitors ◽  
Selection Of

SUMMARYThe species Phytomonas serpens is known to express some molecules displaying similarity to those described in trypanosomatids pathogenic to humans, such as peptidases from Trypanosoma cruzi (cruzipain) and Leishmania spp. (gp63). In this work, a population of P. serpens resistant to the calpain inhibitor MDL28170 at 70 µm (MDLR population) was selected by culturing promastigotes in increasing concentrations of the drug. The only relevant ultrastructural difference between wild-type (WT) and MDLR promastigotes was the presence of microvesicles within the flagellar pocket of the latter. MDLR population also showed an increased reactivity to anti-cruzipain antibody as well as a higher papain-like proteolytic activity, while the expression of calpain-like molecules cross-reactive to anti-Dm-calpain (from Drosophila melanogaster) antibody and calcium-dependent cysteine peptidase activity were decreased. Gp63-like molecules also presented a diminished expression in MDLR population, which is probably correlated to the reduction in the parasite adhesion to the salivary glands of the insect vector Oncopeltus fasciatus. A lower accumulation of Rhodamine 123 was detected in MDLR cells when compared with the WT population, a phenotype that was reversed when MDLR cells were treated with cyclosporin A and verapamil. Collectively, our results may help in the understanding of the roles of calpain inhibitors in trypanosomatids.

scholarly journals Robotic QM/MM-driven maturation of antibody combining sites

2016 ◽  
Vol 2 (10) ◽  
pp. e1501695 ◽  
Author(s):  
Ivan V. Smirnov ◽  
Andrey V. Golovin ◽  
Spyros D. Chatziefthimiou ◽  
Anastasiya V. Stepanova ◽  
Yingjie Peng ◽  
...  
Keyword(s):  
Immune Response ◽  
In Vitro Selection ◽  
Single Point ◽  
Combinatorial Libraries ◽  
Single Point Mutation ◽  
Wild Type ◽  
Selection Of ◽  
Maturation Function

In vitro selection of antibodies from large repertoires of immunoglobulin (Ig) combining sites using combinatorial libraries is a powerful tool, with great potential for generating in vivo scavengers for toxins. However, addition of a maturation function is necessary to enable these selected antibodies to more closely mimic the full mammalian immune response. We approached this goal using quantum mechanics/molecular mechanics (QM/MM) calculations to achieve maturation in silico. We preselected A17, an Ig template, from a naïve library for its ability to disarm a toxic pesticide related to organophosphorus nerve agents. Virtual screening of 167,538 robotically generated mutants identified an optimum single point mutation, which experimentally boosted wild-type Ig scavenger performance by 170-fold. We validated the QM/MM predictions via kinetic analysis and crystal structures of mutant apo-A17 and covalently modified Ig, thereby identifying the displacement of one water molecule by an arginine as delivering this catalysis.

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