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Kegere J, Ouf A, Siam R, Mamdouh W. Fabrication of Poly(vinyl alcohol)/Chitosan/ Bidens pilosa Composite Electrospun Nanofibers with Enhanced Antibacterial Activities. ACS OMEGA 2019; 4:8778-8785. [PMID: 31459967 PMCID: PMC6648370 DOI: 10.1021/acsomega.9b00204] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Accepted: 05/10/2019] [Indexed: 05/03/2023]
Abstract
Due to the current challenges faced by the increasing rate of drug-resistant bacteria, attention is gradually shifting from synthetic antimicrobial chemical compounds to natural products that are ecofriendly with a wide spectrum of properties. The aim of this research was to successfully fabricate electrospun nanofibers from poly(vinyl alcohol) (PVA), PVA blended with Bidens pilosa and chitosan composite blends and investigate their potential antibacterial activities against Escherichia coli and Staphylococcus aureus. Fabrication of nanofibers was performed by the electrospinning technique, which applies high voltage on the polymer, forcing it to spin off as a jet onto a plate collector. Characterization of the nanofibers was successfully performed by scanning electron microscopy and Fourier transform infrared spectroscopy. Antibacterial assessment was carried out by colony forming unit enumeration. The results obtained revealed a 12% increase in growth inhibition of bacteria in composite nanofibers as compared with their parental forms, which were >91 and 79%, respectively. Chitosan nanofibers have been extensively researched, and their antibacterial properties have been studied. However B. pilosa antibacterial properties in a nanofiber form have not been previously reported. These composite nanofibers open new avenues toward using natural materials as potent antibacterial agents.
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Affiliation(s)
- James Kegere
- Department
of Chemistry, School of Sciences and Engineering (SSE) and Department of
Biology and Biotechnology Graduate Program, School of Sciences and
Engineering (SSE), The American University
in Cairo (AUC), AUC Avenue, P.O. Box 74, New Cairo 11835, Egypt
| | - Amged Ouf
- Department
of Chemistry, School of Sciences and Engineering (SSE) and Department of
Biology and Biotechnology Graduate Program, School of Sciences and
Engineering (SSE), The American University
in Cairo (AUC), AUC Avenue, P.O. Box 74, New Cairo 11835, Egypt
| | - Rania Siam
- Department
of Chemistry, School of Sciences and Engineering (SSE) and Department of
Biology and Biotechnology Graduate Program, School of Sciences and
Engineering (SSE), The American University
in Cairo (AUC), AUC Avenue, P.O. Box 74, New Cairo 11835, Egypt
| | - Wael Mamdouh
- Department
of Chemistry, School of Sciences and Engineering (SSE) and Department of
Biology and Biotechnology Graduate Program, School of Sciences and
Engineering (SSE), The American University
in Cairo (AUC), AUC Avenue, P.O. Box 74, New Cairo 11835, Egypt
- E-mail:
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Abuzeid WM, Girish VM, Fastenberg JH, Draganski AR, Lee AY, Nosanchuk JD, Friedman JM. Nitric oxide-releasing microparticles as a potent antimicrobial therapeutic against chronic rhinosinusitis bacterial isolates. Int Forum Allergy Rhinol 2018; 8:1190-1198. [PMID: 30044542 DOI: 10.1002/alr.22185] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 06/19/2018] [Accepted: 06/22/2018] [Indexed: 12/14/2022]
Abstract
BACKGROUND Bacteria, particularly in the biofilm state, may be implicated in the pathogenesis of chronic rhinosinusitis (CRS) and enhance antibiotic resistance. Nitric oxide (NO) is a gaseous immunomodulator with antimicrobial activity and a short half-life, complicating achievement of therapeutic concentrations. We hypothesized that a novel microparticle-based delivery platform, which allows for adjustable release of NO, could exhibit potent antibacterial effects. METHODS Porous organosilica microparticles (SNO-MP) containing nitrosylated thiol groups were formulated. Dissociation of the nitrosothiol groups generates NO at body temperature. The susceptibility of bacterial isolates from CRS patients to SNO-MP was evaluated through a colony forming unit (CFU) assay. Serial dilutions of SNO-MP in triplicate were incubated with isolates in suspension for 6 hours followed by plating on tryptic soy agar and overnight incubation followed by CFU quantification. Statistical analysis was performed with SPSS using one-way analysis of variance with Bonferroni correction. RESULTS SNO-MP displayed antibacterial activity against gram-positive (methicillin-resistant and -sensitive Staphylococcus aureus) and gram-negative (Pseudomonas aeruginosa, Enterobacter aerogenes, and Proteus mirabilis) isolates. SNO-MP induced dose-dependent reductions in CFU across all strains. Compared with controls and blank nanoparticles, SNO-MP (10 mg/mL) induced a 99.99%-100% reduction in CFU across all isolates, equivalent to a 5-9 log kill (p < 0.005). There was no statistically significant difference in CFU concentration between controls and blank microparticles. CONCLUSION SNO-MP demonstrates potent bactericidal effect against antibiotic-resistant CRS bacterial strains.
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Affiliation(s)
- Waleed M Abuzeid
- Department of Otorhinolaryngology-Head and Neck Surgery, Albert Einstein College of Medicine, Bronx, NY
| | | | - Judd H Fastenberg
- Department of Otorhinolaryngology-Head and Neck Surgery, Albert Einstein College of Medicine, Bronx, NY
| | - Andrew R Draganski
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, NY
| | - Andrew Y Lee
- Department of Otorhinolaryngology-Head and Neck Surgery, Albert Einstein College of Medicine, Bronx, NY
| | - Joshua D Nosanchuk
- Department of Microbiology and Immunology and Department of Medicine, Albert Einstein College of Medicine, Bronx, NY
| | - Joel M Friedman
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, NY
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Cao C, Qu Y, Sun M, Qiu Z, Huang X, Huai B, Lu Y, Zeng Z. In vivo antimicrobial activity of marbofloxacin against Pasteurella multocida in a tissue cage model in calves. Front Microbiol 2015; 6:759. [PMID: 26257726 PMCID: PMC4513234 DOI: 10.3389/fmicb.2015.00759] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2015] [Accepted: 07/13/2015] [Indexed: 12/12/2022] Open
Abstract
Marbofloxacin is a fluoroquinolone specially developed for use in veterinary medicine with broad-spectrum antibacterial activity. The objective of our study was to re-evaluate in vivo antimicrobial activity of marbofloxacin against Pasteurella multocida using subcutaneously implanted tissue cages in calves. Calves were infected by direct injection into tissue cages with P. multocida(type B, serotype 2), then intramuscularly received a range of marbofloxacin doses 24 h after inoculation. The ratio of 24 h area under the concentration-time curve divided by the minimum inhibitory concentration or the mutant prevention concentration (AUC24 h/MIC or AUC24 h/MPC) was the pharmacokinetic-pharmacodynamic (PK/PD) index that best described the effectiveness of marbofloxacin against P. multocida (R (2) = 0.8514) by non-linear regression analysis. Marbofloxacin exhibited a good antimicrobial activity in vivo. The levels of AUC24 h/MIC and AUC24 h/MPC that produced 50% (1.5log10 CFU/mL reduction) and 90% (3log10 CFU/mL reduction) of maximum response were 18.60 and 50.65 h, 4.67 and 12.89 h by using sigmoid Emax model WINNONLIN software, respectively. The in vivo PK/PD integrated methods by tissue cage model display the advantage of the evaluation of antimicrobial activity and the optimization of the dosage regimen for antibiotics in the presence of the host defenses, especially in target animal of veterinary interest.
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Affiliation(s)
- Changfu Cao
- National Reference Laboratory of Veterinary Drug Residues, College of Veterinary Medicine, South China Agricultural University Guangzhou, China
| | - Ying Qu
- National Reference Laboratory of Veterinary Drug Residues, College of Veterinary Medicine, South China Agricultural University Guangzhou, China
| | - Meizhen Sun
- National Reference Laboratory of Veterinary Drug Residues, College of Veterinary Medicine, South China Agricultural University Guangzhou, China
| | - Zhenzhen Qiu
- National Reference Laboratory of Veterinary Drug Residues, College of Veterinary Medicine, South China Agricultural University Guangzhou, China
| | - Xianhui Huang
- National Reference Laboratory of Veterinary Drug Residues, College of Veterinary Medicine, South China Agricultural University Guangzhou, China
| | - Binbin Huai
- National Reference Laboratory of Veterinary Drug Residues, College of Veterinary Medicine, South China Agricultural University Guangzhou, China
| | - Yan Lu
- National Reference Laboratory of Veterinary Drug Residues, College of Veterinary Medicine, South China Agricultural University Guangzhou, China
| | - Zhenling Zeng
- National Reference Laboratory of Veterinary Drug Residues, College of Veterinary Medicine, South China Agricultural University Guangzhou, China ; National Laboratory of Safety Evaluation (Environmental Assessment) of Veterinary Drugs, College of Veterinary Medicine, South China Agricultural University Guangzhou, China
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Pharmacokinetic/pharmacodynamic (PK/PD) indices of antibiotics predicted by a semimechanistic PKPD model: a step toward model-based dose optimization. Antimicrob Agents Chemother 2011; 55:4619-30. [PMID: 21807983 DOI: 10.1128/aac.00182-11] [Citation(s) in RCA: 160] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
A pharmacokinetic-pharmacodynamic (PKPD) model that characterizes the full time course of in vitro time-kill curve experiments of antibacterial drugs was here evaluated in its capacity to predict the previously determined PK/PD indices. Six drugs (benzylpenicillin, cefuroxime, erythromycin, gentamicin, moxifloxacin, and vancomycin), representing a broad selection of mechanisms of action and PK and PD characteristics, were investigated. For each drug, a dose fractionation study was simulated, using a wide range of total daily doses given as intermittent doses (dosing intervals of 4, 8, 12, or 24 h) or as a constant drug exposure. The time course of the drug concentration (PK model) as well as the bacterial response to drug exposure (in vitro PKPD model) was predicted. Nonlinear least-squares regression analyses determined the PK/PD index (the maximal unbound drug concentration [fC(max)]/MIC, the area under the unbound drug concentration-time curve [fAUC]/MIC, or the percentage of a 24-h time period that the unbound drug concentration exceeds the MIC [fT(>MIC)]) that was most predictive of the effect. The in silico predictions based on the in vitro PKPD model identified the previously determined PK/PD indices, with fT(>MIC) being the best predictor of the effect for β-lactams and fAUC/MIC being the best predictor for the four remaining evaluated drugs. The selection and magnitude of the PK/PD index were, however, shown to be sensitive to differences in PK in subpopulations, uncertainty in MICs, and investigated dosing intervals. In comparison with the use of the PK/PD indices, a model-based approach, where the full time course of effect can be predicted, has a lower sensitivity to study design and allows for PK differences in subpopulations to be considered directly. This study supports the use of PKPD models built from in vitro time-kill curves in the development of optimal dosing regimens for antibacterial drugs.
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SÁNCHEZ BRUNI SF. Reply to the Editor. J Vet Pharmacol Ther 2010. [DOI: 10.1111/j.1365-2885.2010.01238_2.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Activity of linezolid in an in vitro pharmacokinetic-pharmacodynamic model using different dosages and Staphylococcus aureus and Enterococcus faecalis strains with and without a hypermutator phenotype. Antimicrob Agents Chemother 2010; 54:1443-52. [PMID: 20100878 DOI: 10.1128/aac.01022-09] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The influence of antibiotic dosages and bacterial mutator phenotypes on the emergence of linezolid-resistant mutants was evaluated in an in vitro pharmacokinetic-pharmacodynamic model. A twice-daily 0.5-h infusion of a 200-, 600-, or 800-mg dose for 48 h was simulated against four strains (MIC, 2 microg/ml): Staphylococcus aureus RN4220 and its mutator derivative MutS2, Enterococcus faecalis ATCC 29212, and a mutator clinical strain of E. faecalis, Ef1497. The peak concentrations (4.38 to 4.79, 13.4 to 14.6, and 19.2 to 19.5 microg/ml) and half-lives at beta-phase (5.01 to 6.72 h) fit human plasma linezolid pharmacokinetics. Due to its bacteriostatic property, the cumulative percentages of the dosing interval during which the drug concentration exceeded the MIC (T > MIC), 66.6 and 69.1% of the dosing interval, were not significant, except for Ef1497, with an 800-mg dose and a T > MIC of 80.9%. At the standard 600-mg dosage, resistant mutants (2- to 8-fold MIC increases) were selected only with Ef1497. A lower, 200-mg dosage did not select resistant mutants of E. faecalis ATCC 29212, but a higher, 800-mg dosage against Ef1497 did not prevent their emergence. For the most resistant mutant (MIC, 16 microg/ml), characterization of 23S rRNA genes revealed the substitution A2453G in two of the four operons, which was previously described only in in vitro mutants of archaebacteria. Nevertheless, this mutant did not yield further mutants under 600- or 200-mg treatment. In conclusion, linezolid was consistently efficient against S. aureus strains. The emergence of resistant E. faecalis mutants was probably favored by the rapid decline of linezolid concentrations against a strong mutator, a phenotype less exceptional in E. faecalis than in S. aureus.
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Metlay JP, Powers JH, Dudley MN, Christiansen K, Finch RG. Antimicrobial drug resistance, regulation, and research. Emerg Infect Dis 2006; 12:183-90. [PMID: 16494740 PMCID: PMC3373116 DOI: 10.3201/eid1202.050078] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Innovative regulatory and legislative measures to stimulate and facilitate the development of new antimicrobial drugs are needed. We discuss research approaches that can aid regulatory decision making on the treatment of resistant infections and minimization of resistance selection. We also outline current and future measures that regulatory agencies may employ to help control resistance and promote drug development. Pharmacokinetic/pharmacodynamic research models offer promising approaches to define the determinants of resistance selection and drug doses that optimize efficacy and reduce resistance selection. Internationally, variations exist in how regulators use drug scheduling, subsidy restrictions, central directives, educational guidelines, amendments to prescribing information, and indication review. Recent consultations and collaborations between regulators, academics, and industry are welcome. Efforts to coordinate regulatory measures would benefit from greater levels of international dialogue.
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Affiliation(s)
- Joshua P Metlay
- VA Medical Center, University of Pennsylvania School of Medicine, Center for Clinical Epidemiology and Biostatistics, Philadelphia, Pennsylvania 19104, USA.
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Takei M, Yamaguchi Y, Fukuda H, Yasuda M, Deguchi T. Cultivation of Neisseria gonorrhoeae in liquid media and determination of its in vitro susceptibilities to quinolones. J Clin Microbiol 2005; 43:4321-7. [PMID: 16145072 PMCID: PMC1234085 DOI: 10.1128/jcm.43.9.4321-4327.2005] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The cultivation of Neisseria gonorrhoeae by use of fastidious broth (FB) was evaluated. FB was found to be able to support the growth of all N. gonorrhoeae strains tested in this study without a rapid decrease in the viable count after exponential growth. After 24 h of incubation at 35 degrees C with 5% CO(2), viable counts of all strains reached over 10(8) CFU/ml in FB. Similar growth of the wild-type strain and its target-altered quinolone-resistant derivatives was observed. The susceptibilities of laboratory-adapted strains and clinical isolates to quinolones were tested by the microdilution method using FB. The MICs determined by microdilution were not significantly different from those determined by the agar dilution method recommended by the CLSI (formerly National Committee for Clinical Laboratory Standards). Moreover, the concentration-dependent time-kill of quinolones such as gatifloxacin and ciprofloxacin was observed in FB. At 2 to 4 times the MIC, gatifloxacin and ciprofloxacin were predominantly bactericidal against N. gonorrhoeae WHO A. At the MIC, the activities of both quinolones ranged from bactericidal to bacteriostatic. At 0.25 to 0.5 times the MIC, gonococcal growth was comparable to that of the growth control. These results suggest that the cultivation of N. gonorrhoeae by use of FB may be useful for evaluation of the antibacterial effects of quinolones.
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Affiliation(s)
- Masaya Takei
- Department of Urology, Gifu University School of Medicine, Japan.
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Martinez M, McDermott P, Walker R. Pharmacology of the fluoroquinolones: a perspective for the use in domestic animals. Vet J 2005; 172:10-28. [PMID: 16154368 DOI: 10.1016/j.tvjl.2005.07.010] [Citation(s) in RCA: 230] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The fluoroquinolones are a class of compounds that comprise a large and expanding group of synthetic antimicrobial agents. Structurally, all fluoroquinolones contain a fluorine molecule at the 6-position of the basic quinolone nucleus. Despite the basic similarity in the core structure of these molecules, their physicochemical properties, pharmacokinetic characteristics and microbial activities can vary markedly across compounds. The first of the fluoroquinolones approved for use in animals, enrofloxacin, was approved in the late 1980s. Since then, five other fluoroquinolones have been marketed for use in animals in the United States, with others currently under investigation. This review focuses on the use of fluoroquinolones within veterinary medicine, providing an overview of the structure-activity relationship of the various members of the group, the clinical uses of fluoroquinolones in veterinary medicine, their pharmacokinetics and potential interspecies differences, an overview of the current understanding of the pharmacokinetic/pharmacodynamic relationships associated with fluoroquinolones, a summary of toxicities that have been associated with this class of compounds, their use in both in human and veterinary species, mechanisms associated with the development of microbial resistance to the fluoroquinolones, and a discussion of fluoroquinolone dose optimization. Although the review contains a large body of basic research information, it is intended that the contents of this review have relevance to both the research scientist and the veterinary medical practitioner.
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Affiliation(s)
- Marilyn Martinez
- US Food and Drug Administration, Center for Veterinary Medicine, Office of New Animal Drug Evaluation, Rockville, MD 20855, USA
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Ba BB, Feghali H, Arpin C, Saux MC, Quentin C. Activities of ciprofloxacin and moxifloxacin against Stenotrophomonas maltophilia and emergence of resistant mutants in an in vitro pharmacokinetic-pharmacodynamic model. Antimicrob Agents Chemother 2004; 48:946-53. [PMID: 14982788 PMCID: PMC353051 DOI: 10.1128/aac.48.3.946-953.2004] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A two-compartment in vitro pharmacokinetic-pharmacodynamic model, with full computer-controlled devices, was used to accurately simulate human plasma pharmacokinetic profiles after multidose oral regimens of ciprofloxacin (750 mg every 12 h) and moxifloxacin (400 mg every 24 h) during 48 h. Pharmacodynamics of these drugs was investigated against three quinolone-susceptible strains of Stenotrophomonas maltophilia (MICs of ciprofloxacin and moxifloxacin of 0.5 to 2 and 0.0625 to 0.5 microg/ml, respectively). The first dose of ciprofloxacin and moxifloxacin reduced the bacterial count by 1 and 2 log CFU/ml, respectively, prior to a bacterial regrowth that reached the plateau value of the growth control curve at 13 to 24 h versus 24 to 36 h and persisted despite repeated administration of both drugs. The surviving bacterial cells were quinolone-resistant mutants (2 to 128 times the MIC) that exhibited cross-resistance to unrelated antibiotics. Their antibiotic resistance probably resulted from the overproduction of different multidrug resistance efflux system(s). C(max)/MIC and area under the concentration-time curve from 0 to 24 h (AUC(0-24))/MIC values were at least threefold higher for moxifloxacin than for ciprofloxacin. Moreover, integral parameters of ciprofloxacin and moxifloxacin, in particular the area under the killing and regrowth curve from 0 to 48 h (AUBC(0-48), 342.3 to 401.3 versus 295.2 to 378.7 h x log CFU/ml, respectively) and the area between the control growth curve and the killing and regrowth curve from 0 to 48 h (ABBC(0-48), 40.4 to 101.1 versus 72.9 to 144.7 h x log CFU/ml, respectively), demonstrated a better antibacterial effect of moxifloxacin than ciprofloxacin on S. maltophilia. However, selection of resistant mutants by both fluoroquinolones, although delayed with moxifloxacin, emphasizes the need to use maximal dosages and combined therapy in the treatment of systemic S. maltophilia infections.
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Affiliation(s)
- Boubakar B Ba
- Laboratoire de Pharmacocinétique et de Pharmacie Clinique, France.
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MacGowan AP, Rogers CA, Holt HA, Bowker KE. Activities of moxifloxacin against, and emergence of resistance in, Streptococcus pneumoniae and Pseudomonas aeruginosa in an in vitro pharmacokinetic model. Antimicrob Agents Chemother 2003; 47:1088-95. [PMID: 12604546 PMCID: PMC149285 DOI: 10.1128/aac.47.3.1088-1095.2003] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2002] [Revised: 09/16/2002] [Accepted: 11/15/2002] [Indexed: 11/20/2022] Open
Abstract
The pharmacodynamics of moxifloxacin against Streptococcus pneumoniae and Pseudomonas aeruginosa were investigated in a pharmacokinetic infection model. Three strains of S. pneumoniae, moxifloxacin, and two strains of P. aeruginosa were used. Antibacterial effect and emergence of resistance were measured for both species over a 72-h period using an initial inoculum of about 10(8) CFU/ml. At equivalent area under the curve (AUC)/MIC ratios, S. pneumoniae was cleared from the model while P. aeruginosa was not. For S. pneumoniae, the area under the bacterial kill curve up to 72 h could be related to AUC/MIC ratio using an inhibitory maximum effect (E(max)) model (concentration required for 50% E(max) [EC(50)], 45 +/- 22; r(2), 0.97). For P. aeruginosa even at the highest AUC/MIC ratio (427), bacterial clearance was insufficient for the EC(50) to be calculated. Emergence of resistance occurred with P. aeruginosa but not to any significant extent with S. pneumoniae. Emergence of resistance in P. aeruginosa as measured by population analysis profile (PAP-AUC) was dependent on drug exposure and time of exposure. In weighted least-squares regression analysis AUC/MIC ratio was predictive of PAP-AUC. When emergence of resistance was measured by the time for the colony counts on media containing antibiotic to increase by 2 logs, again AUC/MIC was the best predictor of emergence of resistance. However, for both experiments using S. pneumoniae and P. aeruginosa the correlation between all the pharmacodynamic parameters was high. These data indicate that for a given fluoroquinolone the magnitude of the AUC/MIC ratio for antibacterial effect is dependent on the bacterial species. Emergence of resistance is dependent on (i) species, (ii) duration of drug exposure, and (iii) drug exposure. A single AUC/MIC ratio magnitude is not adequate to predict antibacterial effect or emergence of resistance for all bacterial species.
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Affiliation(s)
- Alasdair P MacGowan
- Bristol Centre for Antimicrobial Research and Evaluation, University of Bristol and North Bristol NHS Trust, Department of Medical Microbiology, Southmead Hospital, Westbury-on-Trym, United Kingdom.
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MacGowan AP, Bowker KE. Mechanism of fluoroquinolone resistance is an important factor in determining the antimicrobial effect of gemifloxacin against Streptococcus pneumoniae in an in vitro pharmacokinetic model. Antimicrob Agents Chemother 2003; 47:1096-100. [PMID: 12604547 PMCID: PMC149284 DOI: 10.1128/aac.47.3.1096-1100.2003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2002] [Revised: 09/16/2002] [Accepted: 11/15/2002] [Indexed: 11/20/2022] Open
Abstract
Antibacterial effect and emergence of resistance to gemifloxacin and levofloxacin were studied in an in vitro pharmacokinetic model of infection. A panel of Streptococcus pneumoniae strains with known mechanisms of resistance were used; two strains had no known resistance mechanism, two had efflux pumps, three had gyrA plus parC mutations, and one had only a parC mutation. Gemifloxacin MICs were in the range of 0.016 to 0.25 mg/liter, and levofloxacin MICs ranged from 1 to 16 mg/liter. Antimicrobial effect was measured by area under the bacterial-kill curve up to 72 h, and emergence of resistance was determined by population analysis profile before and during drug exposure. The area under the curve (AUC)/MIC ratios for gemifloxacin and levofloxacin were 35 to 544 and 3 to 48, respectively. As expected on the basis of these AUC/MIC ratio differences, antibacterial effect was much greater for gemifloxacin than levofloxacin. In the gemifloxacin simulations, mechanism of resistance as well as MIC determined the antibacterial effect, as indicated by gemifloxacin's greater effect against efflux strains compared to those with gyrA or parC mutations despite similar MICs. This was not true of levofloxacin. Emergence of resistance was not easily demonstrated with either agent, and mechanism of resistance did not have any impact on it.
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Affiliation(s)
- Alasdair P MacGowan
- Bristol Centre for Antimicrobial Research and Evaluation. University of Bristol, United Kingdom.
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MacGowan A, Bowker K. Developments in PK/PD: optimising efficacy and prevention of resistance. A critical review of PK/PD in in vitro models. Int J Antimicrob Agents 2002; 19:291-8. [PMID: 11978500 DOI: 10.1016/s0924-8579(02)00027-4] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In vitro pharmacokinetic models are excellent tools with which to study an antibacterial's pharmacodynamics (pD), being flexible, adaptable, low cost, and correlating well with animal and human systems. They can be used to perform simple descriptive studies on antibacterial effect, determine the dominant pD factor and its magnitude for antibacterial effect, and finally be used to assess the effect of dosing on emergence of resistance. A wide range of model designs are used and some standardisation maybe of value in the near future, however it is clear that in vitro models in conjunction with animal studies and human trials offer an excellent way of studying drug dosing to optimise outcomes.
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Affiliation(s)
- Alasdair MacGowan
- Department of Medical Microbiology, Bristol Centre for Antimicrobial Research and Evaluation, University of Bristol and North Bristol NHS Trust, Southmead Hospital, Westbury-on-Trym, BS10 5NB, UK.
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MacGowan AP, Rogers CA, Holt HA, Wootton M, Bowker KE. Pharmacodynamics of gemifloxacin against Streptococcus pneumoniae in an in vitro pharmacokinetic model of infection. Antimicrob Agents Chemother 2001; 45:2916-21. [PMID: 11557490 PMCID: PMC90752 DOI: 10.1128/aac.45.10.2916-2921.2001] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The pharmacodynamics of gemifloxacin against Streptococcus pneumoniae were investigated in a dilutional pharmacodynamic model of infection. Dose fractionation was used to simulate concentrations of gemifloxacin in human serum associated with 640 mg every 48 h (one dose), 320 mg every 24 h (two doses), and 160 mg every 12 h (four doses). Five strains of S. pneumoniae for which MICs were 0.016, 0.06, 0.1, 0.16, and 0.24 mg/liter were used to assess the antibacterial effect of gemifloxacin. An inoculum of 10(7) to 10(8) CFU/ml was used, and each experiment was performed at least in triplicate. The pharmacodynamic parameters (area under the concentration-time curve [AUC]/MIC, maximum concentration of drug in serum [C(max)]/MIC, and the time that the serum drug concentration remains higher than the MIC [T > MIC]) were related to antibacterial effect as measured by the area under the bacterial-kill curve from 0 to 48 h (AUBKC(48)) using an inhibitory sigmoid E(max) model. Weighted least-squares regression was used to predict the effect of the pharmacodynamic parameters on AUBKC(48), and Cox proportional-hazards regression was used to predict the effect of the three pharmacodynamic parameters on the time needed to kill 99.9% of the starting inoculum (T99.9). There was a clear relationship between strain susceptibility and clearance from the model. The simulations (160 mg every 12 h) were associated with slower initial clearance than were the other simulations; in contrast, bacterial regrowth occurred with the 640-mg simulation when MICs were > or =0.1 mg/liter. The percentage coefficient of variance was 19% for AUBKC(48), and the inhibitory sigmoid E(max) model best fit the relationship between AUBKC(48) and AUC/MIC. C(max)/MIC and T > MIC fit less well. The maximum response occurred at an AUC/MIC of >300 to 400. In weighted least-squares regression analysis, there was no evidence that C(max)/MIC was predictive of AUBKC(48), but both AUC/MIC and T > MIC were. A repeat analysis using only data for which the T > MIC was >75% and for which hence regrowth was minimized indicated that AUC/MIC alone was predictive of AUBKC(48). Initial univariate analysis indicated that all three pharmacodynamic parameters were predictive of T99.9, but in the multivariate model only C(max)/MIC reached significance. These data indicate that gemifloxacin is an effective antipneumococcal agent and that AUC/MIC is the best predictor of antibacterial effect as measured by AUBKC(48). However, C(max)/MIC is the best predictor of speed of kill, as measured by T99.9. T > MIC also has a role in determining AUBKC(48), especially when the dose spacing is considerable. Once-daily dosing seems most suitable for gemifloxacin.
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Affiliation(s)
- A P MacGowan
- Bristol Centre for Antimicrobial Research & Evaluation, North Bristol NHS Trust, Southmead Hospital, Westbury-on-Trym, Bristol BS10 5NB, United Kingdom.
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