Searching for the Optimal Predictor of Ciprofloxacin Resistance in Klebsiella pneumoniae by UsingIn VitroDynamic Models

There is growing evidence of applicability of the hypothesis of the mutant selection window (MSW), i.e., the range between the MIC and the mutant prevention concentration (MPC), within which the enrichment of resistant mutants is most probable. However, it is not clear if MPC-based pharmacokinetic variables are preferable to the respective MIC-based variables as interstrain predictors of resistance. To examine the predictive power of the ratios of the area under the curve (AUC24) to the MPC and to the MIC, the selection of ciprofloxacin-resistant mutants of threeKlebsiella pneumoniaestrains with different MPC/MIC ratios was studied. Each organism was exposed to twice-daily ciprofloxacin for 3 days at AUC24/MIC ratios that provide peak antibiotic concentrations close to the MIC, between the MIC and the MPC, and above the MPC. ResistantK. pneumoniaemutants were intensively enriched at an AUC24/MIC ratio of 60 to 360 h (AUC24/MPC ratio from 2.5 to 15 h) but not at the lower or higher AUC24/MIC and AUC24/MPC ratios, in accordance with the MSW hypothesis. AUC24/MPC and AUC24/MIC relationships with areas under the time courses of ciprofloxacin-resistantK. pneumoniae(AUBCM) were bell shaped. These relationships predict highly variable “antimutant” AUC24/MPC ratios (20 to 290 h) compared to AUC24/MIC ratios (1,310 to 2,610 h). These findings suggest that the potential of the AUC24/MPC ratio as an interstrain predictor ofK. pneumoniaeresistance is lower than that of the AUC24/MIC ratio.

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Bacterial Resistance Studies UsingIn VitroDynamic Models: the Predictive Power of the Mutant Prevention and Minimum Inhibitory Antibiotic Concentrations

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00578-13 ◽

2013 ◽

Vol 57 (10) ◽

pp. 4956-4962 ◽

Cited By ~ 23

Author(s):

Alexander A. Firsov ◽

Elena N. Strukova ◽

Darya S. Shlykova ◽

Yury A. Portnoy ◽

Varvara K. Kozyreva ◽

...

Keyword(s):

Predictive Power ◽

Bacterial Resistance ◽

Area Under The Curve ◽

Mutant Selection ◽

Content Type ◽

E Coli ◽

Selection Window ◽

Mutant Prevention Concentration ◽

Time Courses ◽

Selection Of

ABSTRACTIn light of the concept of the mutant selection window, i.e., the range between the MIC and the mutant prevention concentration (MPC), MPC-related pharmacokinetic indices should be more predictive of bacterial resistance than the respective MIC-related indices. However, experimental evidence of this hypothesis remains limited and contradictory. To examine the predictive power of the ratios of the area under the curve (AUC24) to the MPC and the MIC, the selection of ciprofloxacin-resistant mutants of fourEscherichia colistrains with different MPC/MIC ratios was studied. Each organism was exposed to twice-daily ciprofloxacin for 3 days at AUC24/MIC ratios that provide peak antibiotic concentrations close to the MIC, between the MIC and the MPC, and above the MPC. ResistantE. coliwas intensively enriched at AUC24/MPCs from 1 to 10 h (AUC24/MIC from 60 to 360 h) but not at the lower or higher AUC24/MPC and AUC24/MIC ratios. AUC24/MPC and AUC24/MIC relationships of the areas under the time courses of ciprofloxacin-resistantE. coli(AUBCM) were bell-shaped. A Gaussian-like function fits the AUBCM-AUC24/MPC and AUBCM-AUC24/MIC data combined for all organisms (r2= 0.69 and 0.86, respectively). The predicted anti-mutant AUC24/MPC ratio was 58 ± 35 h, and the respective AUC24/MIC ratio was 1,080 ± 416 h. Although AUC24/MPC was less predictive of strain-independentE. coliresistance than AUC24/MIC, the established anti-mutant AUC24/MPC ratio was closer to values reported forStaphylococcus aureus(60 to 69 h) than the respective AUC24/MIC ratio (1,080 versus 200 to 240 h). This implies that AUC24/MPC might be a better interspecies predictor of bacterial resistance than AUC24/MIC.

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Synergistic Combination of Linezolid and Fosfomycin Closing Each Other’s Mutant Selection Window to Prevent Enterococcal Resistance

Frontiers in Microbiology ◽

10.3389/fmicb.2020.605962 ◽

2021 ◽

Vol 11 ◽

Author(s):

Lifang Jiang ◽

Na Xie ◽

Mingtao Chen ◽

Yanyan Liu ◽

Shuaishuai Wang ◽

...

Keyword(s):

Ribosomal Proteins ◽

Bacterial Resistance ◽

Selection Index ◽

Resistance Mechanism ◽

Mutant Selection ◽

Selection Window ◽

Mutant Prevention Concentration ◽

Resistant Mutants ◽

Synergistic Combination ◽

Selection Of

Enterococci, the main pathogens associated with nosocomial infections, are resistant to many common antibacterial drugs including β-lactams, aminoglycosides, etc. Combination therapy is considered an effective way to prevent bacterial resistance. Preliminary studies in our group have shown that linezolid combined with fosfomycin has synergistic or additive antibacterial activity against enterococci, while the ability of the combination to prevent resistance remains unknown. In this study, we determined mutant prevention concentration (MPC) and mutant selection window (MSW) of linezolid, fosfomycin alone and in combination including different proportions for five clinical isolates of Enterococcus and characterized the resistance mechanism for resistant mutants. The results indicated that different proportions of linezolid combined with fosfomycin had presented different MPCs and MSWs. Compared with linezolid or fosfomycin alone, the combination can restrict the enrichment of resistant mutants at a lower concentration. A rough positive correlation between the selection index (SI) of the two agents in combination and the fractional inhibitory concentration index (FICI) of the combination displayed that the smaller FICI of linezolid and fosfomycin, the more probable their MSWs were to close each other. Mutations in ribosomal proteins (L3 and L4) were the mechanisms for linezolid resistant mutants. Among the fosfomycin-resistant mutants, only two strains have detected the MurA gene mutation related to fosfomycin resistance. In conclusion, the synergistic combination of linezolid and fosfomycin closing each other’s MSW could effectively suppress the selection of enterococcus resistant mutants, suggesting that the combination may be an alternative for preventing enterococcal resistance. In this study, the resistance mechanism of fosfomycin remains to be further studied.

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CTX-M-33 Is a CTX-M-15 Derivative Conferring Reduced Susceptibility to Carbapenems

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01515-19 ◽

2019 ◽

Vol 63 (12) ◽

Cited By ~ 6

Author(s):

Laurent Poirel ◽

José-Manuel Ortiz de la Rosa ◽

Anaïs Richard ◽

Marta Aires-de-Sousa ◽

Patrice Nordmann

Keyword(s):

Membrane Protein ◽

Klebsiella Pneumoniae ◽

Hydrolytic Activity ◽

Sequence Type ◽

High Rate ◽

Mutant Selection ◽

Content Type ◽

Selection Window ◽

Mutant Prevention Concentration ◽

Lactamase Inhibitor

ABSTRACT CTX-M-type extended-spectrum β-lactamases (ESBLs) are widespread among Enterobacterales strains worldwide. The most common variant is CTX-M-15, which hydrolyzes ceftazidime at a high rate but spares carbapenems. Here, we identified CTX-M-33, a point mutation derivative of CTX-M-15 (Asp to Ser substitution at Ambler position 109) that exhibited low carbapenemase activity. β-Lactamase CTX-M-33 was identified in a Klebsiella pneumoniae isolate, belonging to sequence type 405 and lacking the outer membrane protein OmpK36, that was resistant to broad-spectrum cephalosporins and β-lactam/β-lactamase inhibitor combinations and displayed decreased susceptibility to carbapenems. Comparative hydrolytic activity assays showed that CTX-M-33 hydrolyzed ceftazidime at a lower level than CTX-M-15 but significantly hydrolyzed meropenem. In addition, CTX-M-33 showed higher mutant prevention concentration values and a wider mutant selection window in the presence of meropenem, in accordance with its observed hydrolytic properties. Here, we identified the very first CTX-M enzyme possessing weak carbapenemase activity, which may correspond to an emerging phenomenon, considering its possible evolution from the widespread ESBL CTX-M-15.

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In Vivo Validation of the Mutant Selection Window Hypothesis with Moxifloxacin in a Murine Model of Tuberculosis

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01123-07 ◽

2007 ◽

Vol 51 (12) ◽

pp. 4261-4266 ◽

Cited By ~ 24

Author(s):

Deepak Almeida ◽

Eric Nuermberger ◽

Sandeep Tyagi ◽

William R. Bishai ◽

Jacques Grosset

Keyword(s):

Drug Exposure ◽

Serum Concentrations ◽

Mutant Selection ◽

Drug Concentrations ◽

Selection Window ◽

Mutant Prevention Concentration ◽

Resistant Mutants ◽

Selection Of

ABSTRACT Combination therapy is the most effective strategy to prevent emergence of resistance during tuberculosis (TB) treatment. Another strategy, albeit theoretical, is to limit the time that drug concentrations fall in the “mutant selection window” (MSW) between the MIC and the mutant prevention concentration (MPC). Drug concentrations above the MPC prevent selective amplification of resistant mutants in vitro even with a single drug exposure. The MSW concept has been validated using fluoroquinolones against Mycobacterium tuberculosis in vitro but not in vivo. Using a mouse model in which serum moxifloxacin (MXF) concentrations were maintained above the MPC, we tested whether this strategy prevents selection of MXF-resistant mutants. Beginning 2 weeks after aerosol infection with M. tuberculosis, when the mean lung log10 CFU count was 7.9 ± 0.2, mice received either no treatment or MXF in the diet at 0.25% to approximate the conventional human dose or 1.5% to maintain serum concentrations above the MPC (8 μg/ml). After 56 days of treatment, lung CFU counts were 3.5 ± 0.8 and 0.9 ± 0.6 in 0.25% and 1.5% of the MXF-treated mice, respectively. In mice given 0.25% MXF, MXF-resistant mutants were selected by day 28 and detected in 16% (3/19) of mice tested on day 56. No selection of MXF-resistant mutants was detected in mice given 1.5% MXF. We conclude that maintaining serum concentrations of MXF above the MPC prevents selection of MXF-resistant mutants. Although this target cannot be achieved clinically with MXF, it might be possible with new fluoroquinolones with more potent activity and/or improved pharmacokinetics.

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Influence of Inoculum Size on the Selection of Resistant Mutants of Escherichia coli in Relation to Mutant Prevention Concentrations of Marbofloxacin

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00156-07 ◽

2007 ◽

Vol 51 (11) ◽

pp. 4163-4166 ◽

Cited By ~ 31

Author(s):

Aude Ferran ◽

Véronique Dupouy ◽

Pierre-Louis Toutain ◽

Alain Bousquet-Mélou

Keyword(s):

Escherichia Coli ◽

Bacterial Population ◽

Inoculum Size ◽

Pharmacodynamic Model ◽

Initial Size ◽

Mutant Selection ◽

Selection Window ◽

Resistant Mutants ◽

Selection Of

ABSTRACT We demonstrate using an in vitro pharmacodynamic model that the likelihood of selection of Escherichia coli mutants resistant to a fluoroquinolone was increased when the initial size of the bacterial population, exposed to fluoroquinolone concentrations within the mutant selection window, was increased.

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Mutant Selection Window and Characterization of Allelic Diversity for Ciprofloxacin-Resistant Mutants of Rhodococcus equi

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01670-09 ◽

2010 ◽

Vol 54 (8) ◽

pp. 3520-3523 ◽

Cited By ~ 4

Author(s):

Hidekazu Niwa ◽

Brent A. Lasker

Keyword(s):

Amino Acid ◽

Allelic Diversity ◽

Dna Gyrase ◽

Rhodococcus Equi ◽

Mutant Selection ◽

Single Nucleotide ◽

Selection Window ◽

Mutant Prevention Concentration ◽

Resistant Mutants

ABSTRACT The mutant prevention concentration (MPC) for ciprofloxacin was determined for two Rhodococcus equi strains. The MPC for both strains was 32 μg/ml, which is above the peak serum concentration of ciprofloxacin obtainable by oral administration in humans. Nine single nucleotide changes corresponding to eight amino acid substitutions in the quinolone resistance-determining regions of DNA gyrase subunits A and B were characterized. Only mutants with amino acid changes in Ser-83 of GyrA were highly resistant (≥64 μg/ml). Our results suggest that ciprofloxacin monotherapy against R. equi infection may result in the emergence of ciprofloxacin-resistant mutants.

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Susceptibility and PK/PD relationships of Staphylococcus aureus strains isolated from the milk of sheep and goats with clinical mastitis to five veterinary fluoroquinolones

Veterinary Record ◽

10.1136/vr.103964 ◽

2017 ◽

Vol 180 (15) ◽

pp. 376-376 ◽

Cited By ~ 4

Author(s):

J. M. Serrano-Rodríguez ◽

C. Cárceles-García ◽

C. M. Cárceles-Rodríguez ◽

M. L. Gabarda ◽

J. M. Serrano-Caballero ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Inhibitory Concentration ◽

Clinical Mastitis ◽

The Other ◽

Mutant Selection ◽

Sheep And Goats ◽

Selection Window ◽

Mutant Prevention Concentration ◽

Higher Doses ◽

Selection Of

Minimum inhibitory concentration (MIC) and mutant prevention concentration (MPC) of veterinary fluoroquinolones as enrofloxacin, its metabolite ciprofloxacin, danofloxacin, difloxacin and marbofloxacin against Staphylococcus aureus strains (n=24) isolated from milk of sheep and goats affected by clinical mastitis were evaluated. The authors have used the MIC and MPC, as well as the pharmacokinetic-pharmacodynamic relationships in plasma and milk. MIC values were significantly different between drugs, unlike MPC values. Lower MIC values were obtained for danofloxacin and difloxacin, middle and higher values for enrofloxacin, ciprofloxacin and marbofloxacin. However, differences in MPC values were not found between drugs. At conventional doses, the AUC24/MIC and AUC24/MPC ratios were close to 30–80 hours and 5–30 hours, with exception of danofloxacin, in plasma and milk. The time inside the mutant selection window (TMSW) was close to 3–6 hours for enrofloxacin, ciprofloxacin and marbofloxacin, near to 8 hours for danofloxacin and 12–22 hours for difloxacin. From these data, the mutant selection window could be higher for danofloxacin and difloxacin compared with the other fluoroquinolones tested. The authors concluded that enrofloxacin and marbofloxacin, at conventional doses, could prevent the selection of bacterial subpopulations of S aureus, unlike danofloxacin and difloxacin, where higher doses could be used.

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Mutant Prevention Concentration of Garenoxacin (BMS-284756) for Ciprofloxacin-Susceptible or -Resistant Staphylococcus aureus

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.47.3.1023-1027.2003 ◽

2003 ◽

Vol 47 (3) ◽

pp. 1023-1027 ◽

Cited By ~ 32

Author(s):

Xilin Zhao ◽

William Eisner ◽

Nathan Perl-Rosenthal ◽

Barry Kreiswirth ◽

Karl Drlica

Keyword(s):

Staphylococcus Aureus ◽

Treatment Time ◽

Mutant Selection ◽

Selective Enrichment ◽

Drug Concentrations ◽

Selection Window ◽

Mutant Prevention Concentration ◽

Resistant Mutants

ABSTRACT The new quinolone garenoxacin (BMS-284756), which lacks a C-6 fluorine, was examined for its ability to block the growth of Staphylococcus aureus. Measurement of the MIC and the mutant prevention concentration (MPC) revealed that garenoxacin was 20-fold more potent than ciprofloxacin for a variety of ciprofloxacin-susceptible isolates, some of which were resistant to methicillin. The MPC for 90% of the isolates (MPC90) was below published serum drug concentrations achieved with recommended doses of garenoxacin. These in vitro observations suggest that garenoxacin has a low propensity for selective enrichment of fluoroquinolone-resistant mutants among ciprofloxacin-susceptible isolates of S. aureus. For ciprofloxacin-resistant isolates, the MIC at which 90% of the isolates tested were inhibited was below serum drug concentrations while the MPC90 was not. Thus, for these strains, garenoxacin concentrations are expected to fall inside the mutant selection window (between the MIC and the MPC) for much of the treatment time. As a result, garenoxacin is expected to selectively enrich mutants with even lower susceptibility.

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In vitro selection of aztreonam/avibactam resistance in dual-carbapenemase-producing Klebsiella pneumoniae

Journal of Antimicrobial Chemotherapy ◽

10.1093/jac/dkz468 ◽

2019 ◽

Vol 75 (3) ◽

pp. 559-565 ◽

Cited By ~ 6

Author(s):

Siqiang Niu ◽

Jie Wei ◽

Chunhong Zou ◽

Kalyan D Chavda ◽

Jingnan Lv ◽

...

Keyword(s):

Klebsiella Pneumoniae ◽

In Vitro Selection ◽

Fold Increase ◽

Single Step ◽

Mutant Selection ◽

Microdilution Method ◽

Broth Microdilution Method ◽

Resistant Mutants ◽

Selection Of

Abstract Objectives To examine the in vitro selection of aztreonam/avibactam resistance among MBL-producing Klebsiella pneumoniae and to understand the mechanism of increased resistance. Methods The MICs of aztreonam were determined with and without avibactam (4 mg/L) using a broth microdilution method. Single-step and multi-step mutant selection was conducted on five MBL-producing K. pneumoniae strains, including two dual carbapenemase producers. Genomic sequencing and gene cloning were performed to investigate the mechanism of increased resistance. Results We examined the MICs for 68 MBL-producing K. pneumoniae isolates, including 13 dual carbapenemase producers. Compared with aztreonam alone, the addition of avibactam (4 mg/L) reduced the MICs for all isolates by >128-fold, with MIC50 and MIC90 values of 0.25 and 1 mg/L, respectively. One NDM-1-, OXA-48-, CTX-M-15- and CMY-16-positive ST101 K. pneumoniae strain was selected to be resistant to aztreonam/avibactam, with a >16-fold increase in MIC (>128 mg/L). WGS revealed that the resistant mutants lost the blaNDM-1 gene, but acquired amino acid substitutions in CMY-16 (Tyr150Ser and Asn346His). Construction of blaCMY-16 mutants confirmed that the substitutions (Tyr150Ser and Asn346His) were primarily responsible for the decreased susceptibility to aztreonam/avibactam. In addition, transfer of blaCMY-16 mutant (Tyr150Ser and Asn346His) plasmid constructs into certain clinical carbapenemase-producing isolates demonstrated >64-fold increased MICs of aztreonam/avibactam and aztreonam/avibactam/ceftazidime. Conclusions Aztreonam in combination with avibactam showed potent in vitro activity against MBL-producing K. pneumoniae. However, our study suggested the likelihood of aztreonam/avibactam resistance among MBL- and AmpC-co-producing strains and clinical practice should beware of the possibility of the emerging resistance.

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The Inactivation of Intrinsic Antibiotic Resistance Determinants Widens the Mutant Selection Window for Quinolones in Stenotrophomonas maltophilia

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01558-12 ◽

2012 ◽

Vol 56 (12) ◽

pp. 6397-6399 ◽

Cited By ~ 9

Author(s):

Guillermo García-León ◽

María B. Sánchez ◽

José L. Martínez

Keyword(s):

Stenotrophomonas Maltophilia ◽

Wild Type Strain ◽

Efflux Pump ◽

Intrinsic Resistance ◽

Mutant Selection ◽

Content Type ◽

Resistance Determinants ◽

Selection Window ◽

Resistance Protein ◽

Resistant Mutants

ABSTRACTWe have determined that the mutational inactivation of the SmeDEF efflux pump and the SmQnr quinolone resistance protein widens the mutant selection windows for ofloxacin and ciprofloxacin ofStenotrophomonas maltophiliaby reducing their MICs. Resistant mutants arising from a strain lacking SmeDEF and SmQnr presented levels of susceptibility similar to those of the wild-type strain. This indicates that inactivation of intrinsic resistance determinants might increase the chances for selecting resistant mutants at low antibiotic concentrations.

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