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William A Craig - One of the best experts on this subject based on the ideXlab platform.

  • decreased bactericidal activity during the period of the Postantibiotic Effect
    Journal of Antimicrobial Chemotherapy, 1994
    Co-Authors: Sigurdur Gudmundsson, Bennett Vogelman, William A Craig
    Abstract:

    Standard and clinical strains of Staphylococcus aureus, Escherichia coli and Klebsiella preumoniae were subjected to continuous exposure to β-lactams and aminoglycosides during the Postantibiotic Effect phase induced by rifampicin or erythromycin (for S. aureus). A significant inhibition of bactericidal activity by these agents during the PAE period was observed. The degree of inhibition was dependent both on the class of antimicrobial agent (β-lactams>aminoglycosides) and the microorganism (Gram-negative bacilli>S. aureus)

  • the Postantibiotic Effect of antifungal agents against common pathogenic yeasts
    Journal of Antimicrobial Chemotherapy, 1994
    Co-Authors: J Turnidge, Sigurdur Gudmundsson, Bennett Vogelman, William A Craig
    Abstract:

    A total of ten strains of Candida spp. and Cryptococcus neoformans were examined for the presence of the Postantibiotic Effect (PAE) after 0.5-2 h exposure to amphotericin B, 5-fluorocytosine, miconazole and ketoconazole. Significant PAEs were observed for amphotericin B and 5-fluorocytosine, but none for the imidazoles. The duration of the PAEs of amphotericin B ranged from 0.5-10.4 h for the Candida spp. and 2.8-10.6 h for the cryptococcos, while 5-fluorocytosine induced PAEs from 0.8-7.4 h and 2.4-5.4 h, respectively. Even though no PAEs were demonstrated for the imidazoles, the growth rate was persistently reduced by continuous exposure to concentrations as low as 1/1000 of the MIC of these agents. These findings may have implications for dosing antifungal agents in systemic yeast infections

  • factors affecting duration of in vivo Postantibiotic Effect for aminoglycosides against gram negative bacilli
    Journal of Antimicrobial Chemotherapy, 1991
    Co-Authors: B Fantin, Bennett Vogelman, Steven C Ebert, J Leggett, William A Craig
    Abstract:

    A murine thigh-infection model was used to determine the Effect of certain host- and drug-related factors on the duration of the in-vivo Postantibiotic Effect (PAE) observed with aminoglycosides against Gram-negative bacilli. The role of neutrophils, pharmacokinetics and variation among species and strains were studied. PAEs were quantitated after a single injection of gentamicin or amikacin

Sigurdur Gudmundsson - One of the best experts on this subject based on the ideXlab platform.

  • different patterns of bacterial dna synthesis during Postantibiotic Effect
    Antimicrobial Agents and Chemotherapy, 1995
    Co-Authors: Magnus Gottfredsson, Helga Erlendsdottir, A Gudmundsson, Sigurdur Gudmundsson
    Abstract:

    Studies on bacterial metabolism during the Postantibiotic Effect (PAE) period are limited but might provide insight into the nature of the PAE. We evaluated the rate of DNA synthesis in bacteria during the PAE period after a 1-h exposure of organisms in the logarithmic growth phase to various antibiotics. Staphylococcus aureus ATCC 25923 was exposed to vancomycin, dicloxacillin, rifampin, and ciprofloxacin ; Escherichia coli ATCC 25922 was exposed to gentamicin, tobramycin, rifampin, imipenem, and ciprofloxacin ; and Pseudomonas aeruginosa ATCC 25783 was exposed to imipenem, tobramycin, and ciprofloxacin. DNA synthesis was determined by measuring the rate of [ 3 H]thymidine incorporation in S. aureus and E. coli and [ 3 H]adenine incorporation in P. aeruginosa. DNA synthesis in S. aureus was suppressed during the PAE phase with vancomycin, dicloxacillin, and rifampin, it was suppressed in E. coli with rifampin, and it was suppressed in P. aeruginosa after exposure to tobramycin. Conversely, DNA synthesis was relatively enhanced in the gram-negative bacilli after exposure to imipenem and in all three species after exposure to ciprofloxacin. However, DNA synthesis in E. coli was only minimally affected after exposure to tobramycin and gentamicin. The differences in DNA synthesis observed after exposure to various antimicrobial agents suggest multiple mechanisms for the PAE.

  • decreased bactericidal activity during the period of the Postantibiotic Effect
    Journal of Antimicrobial Chemotherapy, 1994
    Co-Authors: Sigurdur Gudmundsson, Bennett Vogelman, William A Craig
    Abstract:

    Standard and clinical strains of Staphylococcus aureus, Escherichia coli and Klebsiella preumoniae were subjected to continuous exposure to β-lactams and aminoglycosides during the Postantibiotic Effect phase induced by rifampicin or erythromycin (for S. aureus). A significant inhibition of bactericidal activity by these agents during the PAE period was observed. The degree of inhibition was dependent both on the class of antimicrobial agent (β-lactams>aminoglycosides) and the microorganism (Gram-negative bacilli>S. aureus)

  • the Postantibiotic Effect of antifungal agents against common pathogenic yeasts
    Journal of Antimicrobial Chemotherapy, 1994
    Co-Authors: J Turnidge, Sigurdur Gudmundsson, Bennett Vogelman, William A Craig
    Abstract:

    A total of ten strains of Candida spp. and Cryptococcus neoformans were examined for the presence of the Postantibiotic Effect (PAE) after 0.5-2 h exposure to amphotericin B, 5-fluorocytosine, miconazole and ketoconazole. Significant PAEs were observed for amphotericin B and 5-fluorocytosine, but none for the imidazoles. The duration of the PAEs of amphotericin B ranged from 0.5-10.4 h for the Candida spp. and 2.8-10.6 h for the cryptococcos, while 5-fluorocytosine induced PAEs from 0.8-7.4 h and 2.4-5.4 h, respectively. Even though no PAEs were demonstrated for the imidazoles, the growth rate was persistently reduced by continuous exposure to concentrations as low as 1/1000 of the MIC of these agents. These findings may have implications for dosing antifungal agents in systemic yeast infections

  • ultrastructural alterations of bacteria during the Postantibiotic Effect
    Chemotherapy, 1993
    Co-Authors: Magnus Gottfredsson, Helga Erlendsdottir, Ragnhildur Kolka, A Gudmundsson, Sigurdur Gudmundsson
    Abstract:

    Ultrastructural alterations of Staphylococcus aureus and Pseudomonas aeruginosa were examined during the Postantibiotic Effect (PAE) with transmission electron microscopy. After exposure to dicloxacillin the staphylococci were characterized by an increase in the number of crosswalls, rifampin produced thickening of the cell wall, but only minimal changes were induced by gentamicin. Intracellular electrondense aggregates were observed in P. aeruginosa after exposure to imipenem, tobramycin and ciprofloxacin, and imipenem caused globoid cell formations. These alterations were not uniform in every organism, but they correlated well with the duration of the PAE determined by viable counts.

  • quantitation of Postantibiotic Effect by measuring co2 generation of bacteria with the bactec blood culture system
    Antimicrobial Agents and Chemotherapy, 1991
    Co-Authors: Magnus Gottfredsson, Helga Erlendsdottir, Sigurdur Gudmundsson
    Abstract:

    The duration of the Postantibiotic Effect (PAE) determined by bacterial CO2 production measured by using the BACTEC NR 730 blood culture system was compared with PAEs determined by standard viability counting. PAEs for Staphylococcus aureus after exposure to dicloxacillin, vancomycin, rifampin, gentamicin, and ciprofloxacin and for Escherichia coli after exposure to ampicillin, gentamicin, and ciprofloxacin were quantitated by the two methods, and an excellent correlation (r = 0.93) was demonstrated. The difference in the PAE durations determined by the two methods was 0.1 +/- 0.4 (mean +/- standard deviation) h. Thus, the BACTEC CO2 generation method provides a simple, alternate way of determining the PAE in vitro.

L Marzella - One of the best experts on this subject based on the ideXlab platform.

  • hyperoxia and prolongation of aminoglycoside induced Postantibiotic Effect in pseudomonas aeruginosa role of reactive oxygen species
    Antimicrobial Agents and Chemotherapy, 1993
    Co-Authors: M K Park, R A M Myers, L Marzella
    Abstract:

    Abstract Hyperoxia prolongs the Postantibiotic Effect (PAE) of the aminoglycoside tobramycin in Pseudomonas aeruginosa. We tested the hypothesis that the PAE is prolonged because hyperoxia increases free radical flux while tobramycin inhibits the induction of antioxidant defenses. Exposure of P. aeruginosa to hyperoxia (100% O2) for 1 h increased superoxide dismutase, catalase, and glutathione levels. In the presence of tobramycin (1x the MIC), the induction of antioxidant defenses by hyperoxia was nearly abrogated. Neither preexposure of P. aeruginosa to hyperoxia nor supplementation with the antioxidants copper(II) (diisopropylsalicylate)2 (superoxide dismutase-like), catalase, or dimethyl sulfoxide abolished prolongation of the PAE of tobramycin induced by hyperoxia.

  • hyperoxia prolongs the aminoglycoside induced Postantibiotic Effect in pseudomonas aeruginosa
    Antimicrobial Agents and Chemotherapy, 1991
    Co-Authors: M K Park, R A M Myers, K H Muhvich, L Marzella
    Abstract:

    The objective of this study was to determine whether hyperoxia enhances aminoglycoside activity against Pseudomonas aeruginosa. The existence of tobramycin-oxygen synergy was determined by using the in vitro Postantibiotic Effect (PAE). P. aeruginosa strains were incubated for 1 h in medium containing tobramycin at four times the MIC in the following gas mixtures: normoxia (21% O2), hyperoxia (100% O2, 101.3 kPa), or hyperbaric oxygen (100% O2, 274.5 kPa). Tobramycin was removed after 1 h and bacteria were incubated under normoxic conditions; growth rates were measured for 5 h. Exposure of three P. aeruginosa strains to hyperoxia prolonged the PAE of tobramycin approximately twofold compared with the PAE after exposure to normoxia (P less than 0.05). Exposure of P. aeruginosa ATCC 27853 to tobramycin and hyperbaric oxygen prolonged the time required for bacteria to increase 1 log10 CFU/ml compared with the time after exposure for this increase to occur in tobramycin-treated, normoxic or hyperoxic groups (P less than 0.02). Pulse-chase labeling of bacteria with L-[35S]methionine, immediately after removal of tobramycin, showed that protein synthesis rates were decreased compared with those in controls (P = 0.0001). Moreover, in tobramycin-treated groups, hyperoxia and hyperbaric oxygen induced 2- and 16-fold decreases, respectively, in protein synthesis rates compared with normoxia; these results did not achieve statistical significance. In the absence of tobramycin, hyperoxia increased bacterial growth (134%; P less than 0.01) and protein synthesis (24%; not significant) compared with normoxia. Hyperbaric oxygen, however, delayed the growth recovery of bacteria (P less than 0.05). We conclude that hyperoxia enhances the bacteriostatic Effects of tobramycin in a synergistic manner.+

Ferenc Kilar - One of the best experts on this subject based on the ideXlab platform.

R Wise - One of the best experts on this subject based on the ideXlab platform.

  • Pharmacodynamic properties of HMR 3004, a novel ketolide, on respiratory pathogens, enterococci and Bacteroides fragilis demonstrated by studies of time kill kinetics and Postantibiotic Effect
    Clinical Microbiology and Infection, 1998
    Co-Authors: F J Boswell, J M Andrews, R Wise
    Abstract:

    Objective The pharmacodynamic properties of the novel ketolide (a new class of macrolide) antibiotic, HMR 3004, were investigated by studying time-kill kinetics and Postantibiotic Effect. Methods The time-kill kinetics were studied at two inocula against three strains each of Staphylococcus aureus, Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pneumoniae, Streptococcus pyogenes, Enterococcus faecalis, Enterococcus faecium and Bacteroides fragilis. The Postantibiotic Effects of HMR 3004 were also investigated on these organisms at concentrations equivalent to 1, 4 and 10 × MIC. Results The time kill-kinetic data demonstrated that HMR 3004 is inoculum dependent and predominantly bacteriostatic being only slowly bactericidal at higher concentrations. HMR 3004 exhibited a significant Postantibiotic Effect with all strains studied, ranging from 1.9–6.2 h at 10 × MIC. Conclusions The bacteriostatic activity and significant Postantibiotic Effect demonstrated by HMR 3004 are similar to those previously obtained with other macrolides.

  • Postantibiotic Effect of trovafloxacin on pseudomonas aeruginosa
    Journal of Antimicrobial Chemotherapy, 1997
    Co-Authors: F J Boswell, J M Andrews, R Wise
    Abstract:

    The Postantibiotic Effect (PAE) of trovafloxacin (CP 99,219) was investigated with six strains of Pseudomonas aeruginosa at concentrations equivalent to 0.5, 1, 2 and 4 x MIC. Trovafloxacin exhibited a significant PAE with four out of the six strains of P. aeruginosa studied. The PAE values obtained for trovafloxacin with P. aeruginosa ranged from 0.3 h to 2.3 h, increasing with increased exposure time and trovafloxacin concentration.

  • pharmacodynamic properties of faropenem demonstrated by studies of time kill kinetics and Postantibiotic Effect
    Journal of Antimicrobial Chemotherapy, 1997
    Co-Authors: F J Boswell, J M Andrews, R Wise
    Abstract:

    The pharmacodynamic properties of faropenem, a new oral penem antibiotic, were investigated by studying time‐kill kinetics and Postantibiotic Effect. Time‐kill kinetics were employed against strains of Bacteroides fragilis, Escherichia coli, Staphylococcus aureus, Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pyogenes . The Postantibiotic Effects of faropenem were studied using strains of E. coli, S. aureus, H. infl u e n z a e and S t r e p t ococcus pneumoniae. The time‐kill kinetic data demonstrated that faropenem has bactericidal activity. Faropenem exhibited a signifi cant Postantibiotic Effect against all strains except H. influenzae .

  • The Postantibiotic Effect of azithromycin on respiratory pathogens
    Revista medico-chirurgicala a Societatii de Medici si Naturalisti din Iasi, 1996
    Co-Authors: D Diculencu, F J Boswell, J M Andrews, R Wise
    Abstract:

    Azithromycin has in vitro activity which includes important respiratory pathogens and is successful in treatment of respiratory tract infections. We assessed Postantibiotic Effect (PAE) of azithromycin against 3 stains of Streptococcus pneumoniae, 2 strains of Haemophilus influenzae and 2 strains of Moraxella catarrhalis. The strains were exposed for 2 hours to an azithromycin concentration of 0.5 mg/L (maximum serum concentration achieved by azithromycin after the usual dosing regimen). A stationary phase inoculum of 1 x 10(6)-5 x 10(6) UFC/ml in IsoSensitest Broth with 5% lysed horse blood and 20 mg/L NAD was used and shaken for the duration of the experiment. Antibiotic was neutralised by dilution 1:1000 into pre-warmed medium. Viable counts were determined before and after antibiotic exposure and then hourly for 7 hours by Miles and Misra method. The experiment was performed in triplicate. Even at such low concentration as that achieved in serum, azithromycin exhibits a PAE of 119 min for pneumococci, 130 min for haemophili and 155 min for moraxellae, fact which could allow the use of usual oral regimen in bacteraemic respiratory infection, as well.