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M Wootton

Publications and source records attributed to M Wootton.

At least 19 recordsLinked to original sources
PubMed2002

BAL 9141, a new broad-spectrum pyrrolidinone cephalosporin: activity against clinically significant anaerobes in comparison with 10 other antimicrobials.

The in vitro potency of BAL 9141, a new pyrrolidinone cephalosporin, was tested against non-duplicate strains of anaerobic bacteria. The MIC(50) was 1 mg/L against Actinomyces species, Clostridium species, Gram-positive anaerobic cocci, Porphyromonas species, Fusobacterium species, Lactobacillus species, Prevotella species and Veillonella species. The MIC(50) was 16 mg/L for Bacteroides fragilis and other Bacteroides species. BAL 9141 was not active against cefoxitin-resistant Bacteroides fragilis.

Bacteria, Anaerobic↗
PubMed2001

A modified population analysis profile (PAP) method to detect hetero-resistance to vancomycin in Staphylococcus aureus in a UK hospital.

One hundred methicillin-resistant Staphylococcus aureus (MRSA) strains, isolated between 1983 and 1999, were tested alongside the vancomycin hetero-resistant S. aureus (hVRSA) strain Mu 3, and vancomycin-resistant S. aureus (VRSA) strain Mu 50, for their resistance to vancomycin. This was achieved using the screening method described by Hiramatsu, gradient plates, agar incorporation, standard Etest, macrodilution Etest and a modified population analysis. Using Hiramatsu's screening method, 5% of the 100 MRSA were identified as VRSA and 5% identified as hVRSA, the gradient plates identified 7% hVRSA, and the standard and macrodilution Etests identified no hVRSA. Mu 3 appeared to be vancomycin-susceptible using both the agar incorporation and standard Etest methods, but was classified as hVRSA using the macrodilution Etest. The modified population analysis reliably detected vancomycin hetero-resistance in Mu 3 and identified no hVRSAs within the 100 MRSA sample.

Hospitals↗
PubMed2001

The activity of vancomycin against heterogeneous vancomycin-intermediate methicillin-resistant Staphylococcus aureus explored using an in vitro pharmacokinetic model.

Heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) may account for treatment failure with vancomycin and act as a precursor of vancomycin-intermediate or -resistant S. aureus. The activity of vancomycin was assessed against vancomycinsusceptible, hVISA and VISA strains in a dilutional pharmacokinetic model. Over a 48 h period, total bacteria and cells with a vancomycin-intermediate phenotype were quantified. Total counts of hVISA were reduced by vancomycin in a similar way to a vancomycin-susceptible control. The vancomycin-intermediate sub-population was eradicated from the model within one dose interval. Exposure to low vancomycin concentrations did not result in an increase in the proportion of cells which were vancomycin intermediate. Short-term exposure of hVISA to vancomycin at gradient concentrations did not increase the proportion of cells with vancomycin-intermediate phenotype.

Anti-Bacterial Agents↗
PubMed2001

Pharmacodynamics of gemifloxacin against Streptococcus pneumoniae in an in vitro pharmacokinetic model of infection.

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.

Anti-Infective Agents↗
PubMed2001

Evaluation of current methods for detection of staphylococci with reduced susceptibility to glycopeptides.

The sensitivity and specificity of seven methods (agar dilution, broth microdilution, Etest at 0.5 and 2.0 McFarland (McF) inocula, two agar screening methods, and population studies [PS]) were evaluated in a double-blind study involving 284 methicillin-resistant Staphylococcus aureus (MRSA) strains and 45 Staphylococcus strains with reduced susceptibilities to vancomycin (SRSV). The results were compared to the population analysis profile-area under the curve ratio method (PAP-AUC ratio compared to that of Mu3) as described by Wootton et al. The agar screening method using brain heart infusion agar (6 microg of vancomycin per ml) gave a sensitivity of 22% and a specificity of 97%. A similar method using Mueller-Hinton agar (5 microg of vancomycin per ml) gave a sensitivity of 20% and a specificity of 99%. The PS method detected 34 false positives (12%) and gave a sensitivity of 71% and a specificity of 88%. Etest using 0.5 and 2.0 McF inocula gave sensitivities and specificities of 82 and 93% and of 96 and 97%, respectively. The best Etest interpretative criteria for the 2.0 McF inoculum was > or =8 mg of vancomycin per liter and > or =8 microg teicoplanin per ml or > or =12 microg of teicoplanin per ml. The direct colony suspension inoculum for this method was found to be equally accurate in detecting (hetero-)glycopeptide-intermediate S. aureus compared to the overnight broth inoculum preparation method. Agar dilution and broth microdilution using the NCCLS breakpoint criteria for vancomycin gave sensitivities and specificities of 20 and 100% and of 11 and 100%, respectively. Using the Etest with a 2.0 McF inoculum, six different media were assessed against a selection of SRSV (n = 48) and MRSA (n = 12). Brain heart infusion agar yielded the highest sensitivity and specificity values: 88 and 88%, respectively.

Anti-Bacterial Agents↗
PubMed2000

Differentiating embryonal stem cells are a rich source of haemopoietic gene products and suggest erythroid preconditioning of primitive haemopoietic stem cells.

The difficulties associated with studying molecular mechanisms important in hemopoietic stem cell (HSC) function such as the problems of purifying homogeneous stem cell populations, have prompted us to adapt the murine ES cell system as an in vitro model of HSC generation and function. We now report that careful analysis of the time course of HSC generation in differentiating ES cells allows them to be used as a source of known and novel hemopoietic gene products. We have generated a subtracted library using cDNA from ES cells collected just prior to and just following the emergence of HSCs. Analysis of this library shows it to be a rich source of known hemopoietic and hemopoietic related gene products with 44% of identifiable cDNAs falling into these camps. We have demonstrated the value of this system as a source of novel genes of relevance to HSC function by characterizing a novel membrane protein encoding cDNA that is preferentially expressed in primitive hemopoietic cells. Intriguingly, further analysis of the known components of the subtracted library is suggestive of erythroid preconditioning of the ES cell-derived HSC. We have used dot-blot and in situ analysis to indicate that this erythroid preconditioning is probably restricted to primitive but not definitive HSC.

Amino Acid Sequence↗
PubMed2000

Assessment of different antibacterial effect measures used in in vitro models of infection and subsequent use in pharmacodynamic correlations for moxifloxacin.

A dilutional culture in vitro pharmacodynamic model of infection was used to assess the best measure of antibacterial effect for moxifloxacin at simulated human doses of 400 mg 24 hourly for 48 h. This was then related to two pharmacodynamic parameters, the drug area under curve: MIC ratio (AUC/MIC) and the length of time that the drug concentration remained above the MIC of the bacterium (T > MIC). Twenty-one bacterial strains (Streptococcus pneumoniae n = 6; Haemophilus influenzae n = 6; Moraxella catarrhalis n = 3; beta-haemolytic streptococci n = 3; Staphylococcus aureus n = 3; MIC range 0.06-3.6 mg/L) were tested in 69 individual simulations. The measures or parameters of antibacterial effect considered were log change in viable count in the initial inoculum at 12 h (triangle up12), 24 h (triangle up24), 36 h (triangle up36), 48 h (triangle up48), maximum reduction in count (triangle up(max)); time for bacterial counts to reduce by 100-fold from the initial density (T99) or 1,000-fold (T99.9); and area under the bacterial kill curve from 0 to 24 h (AUBKC(24)) or from 0 to 48 h (AUBKC(48)). triangle up12, triangle up24, triangle up36, triangle up48, triangle up(max), T99, T99.9 did not vary over the complete range of MICs; at high MICs, especially with Gram-positive bacteria the T99 and T99.9 values were >48 h while at low MICs, especially with Gram-negative bacteria, bacterial counts were reduced below the limit of detection with triangle up12, triangle up24, triangle up36, triangle up48 and triangle up(max) exceeding >6.5 log reduction. AUBKC(24) and AUBKC(48) varied more completely over the range of MICs and more importantly had the best within-strain reproducibility (median percentage coefficient of variation <15%). The relationship between the transformed AUBKC(24) and AUC/MIC could be described by a sigmoid Emax model but the relationship with T > MIC could not. Use of weighted least squares regression to examine the combined effect of AUC/MIC and T > MIC on AUBKC(24) indicated that AUC/MIC provided a good fit to the data (r(2) = 0.94) and adding T > MIC did not improve the model fit. Cox proportional hazards regression indicated that AUC/MIC was predictive of T99 and in a multivariate model although AUC/MIC predicted outcome after fitting AUC/MIC, T > MIC was not significant. AUBKC was thus shown to be the optimum measure of antibacterial effect to use in pharmacodynamic studies of moxifloxacin and AUC/MIC the best predictor of antibacterial effect as measured by AUBKC(24) or T99. These results are in good agreement with animal data on moxifloxacin pharmacodynamics and human data for some other fluoroquinolones.

Animals↗
PubMed2000

Safety and tolerability of bolus intravenous colistin in acute respiratory exacerbations in adults with cystic fibrosis.

OBJECTIVE: To assess the safety and tolerability of bolus intravenous doses of colistin during acute respiratory exacerbations in adults with cystic fibrosis and chronic Pseudomonas aeruginosa infection. METHODS: Twelve patients with acute exacerbations of cystic fibrosis were enrolled in a Phase I open-label study. On day 1, patients received three doses of colistin 2 mega-units (160 mg), reconstituted in 50 mL of NaCl 0.9%, by infusion over 30 minutes three times daily. On days 2, 3, and 4, the same dose of colistin was administered by bolus injection three times a day over five minutes after reconstitution in 20, 15, and 10 mL of NaCl 0.9%, respectively. The injection was given by a nurse or physician using a hand-held syringe. If the latter dose was tolerated, it was continued for the remaining eight days of the study. If any dose was not tolerated, treatment reverted to the previously tolerated concentration, which was continued throughout the remainder of the study. RESULTS: No serious adverse events occurred during the course of the trial. Patients without total indwelling venous access systems experienced mild to moderate injection pain. There were no clinically significant changes in renal function. CONCLUSIONS: This study indicates that the administration of bolus intravenous colistin as 2 mega-units (160 mg) in 10 mL of NaCl 0.9% three times a day is safe. It is well-tolerated by patients with total indwelling venous access systems.

Adult↗
PubMed1999

B-cell antigens within normal and activated human T cells.

In this study we compared cell surface staining for human peripheral blood lymphocyte (PBL) CD antigens by flow cytometry, with staining obtained following permeabilization of PBL using the Cytoperm method (Serotec). Six CD antigens (CD20, CD21, CD22, CD32, CD35 and major histocompatibility complex class II antigen) normally found on the surface of B cells, were also found to be expressed within T cells. We also showed, by immunoelectron microscopy, that these inappropriately expressed ('occult') CD antigens are located within cytoplasmic vesicles or within the rough endoplasmic reticulum. Following in vitro activation of T cells a distinct increase in expression of all of these cytoplasmic antigens was observed but staining at the cell surface was, by comparison, weak. We therefore propose that up-regulation of various B-cell CD antigens occurs within the cytoplasm of T cells following activation and that these antigens may be synthesized and released into the fluid-phase as soluble immunoregulatory molecules.

Antigens, CD↗
PubMed1999

The antibacterial efficacy of levofloxacin and ciprofloxacin against Pseudomonas aeruginosa assessed by combining antibiotic exposure and bacterial susceptibility.

Ciprofloxacin has a four-fold greater in-vitro activity than levofloxacin against Pseudomonas aeruginosa, but levofloxacin has a four-fold higher area under the serum concentration-time curve (AUC) for an equivalent dose. It has been proposed that the AUC/MIC ratio is a general predictor of antibacterial efficacy for quinolones. Using an in-vitro kill curve technique, performed in quadruplicate, with nine antibiotic concentrations and three strains of P. aeruginosa with varying quinolone susceptibility, we constructed sigmoidal dose-response curves for AUC(0-6.5)/MIC and area under the bacterial kill curve (AUBKC) or AUC(0-24)/MIC and log change in viable count at 24 h (delta24). For levofloxacin the log AUC(0-6.5)/MIC ratio to produce 50% of the maximal effect was 0.74 +/- 0.13 (r2 = 0.9435) for levofloxacin and 0.82 +/- 0.06 (r2 = 0.7935) for ciprofloxacin. The log AUC(0-24)/MIC ratio to produce 50% maximal effect was 1.58 +/- 0.13 (r2 = 0.7788) for levofloxacin and 1.37 +/- 0.12 (r2 = 0.7207) for ciprofloxacin. An AUC(0-24)/MIC ratio of 125 produced 85.4% of the maximal response with levofloxacin and 81.5% with ciprofloxacin. These data suggest that levofloxacin and ciprofloxacin have equivalent activity against P. aeruginosa at equivalent AUC/MIC ratios.

Anti-Infective Agents↗
PubMed1999

In-vitro activity of HMR 3647 against Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and beta-haemolytic streptococci.

The in-vitro activity of HMR 3647 and seven comparators (azithromycin, clarithromycin, erythromycin A, roxithromycin, penicillin G, ciprofloxacin and levofloxacin) were tested against 207 Streptococcus pneumoniae and 200 beta-haemolytic streptococci. Ten comparators (azithromycin, clarithromycin, erythromycin A, roxithromycin, ampicillin, co-amoxiclav, cefuroxime, cefotaxime, ciprofloxacin and levofloxacin) were tested against 143 Haemophilus influenzae and 58 Moraxella catarrhalis. The MIC50 of HMR 3647 for S. pneumoniae was < or =0.008 mg/L, less than that for the macrolides or quinolones tested. Pneumococci with an erythromycin A MIC of 0.06 mg/L (n = 23) had an MIC50 of HMR 3647 < or =0.008 mg/L, whereas isolates with an erythromycin A MIC > or =1 mg/L (n = 34) had an MIC50 of HMR 3647 of 0.03 mg/L, a four-fold increase. In contrast, the difference in macrolide MIC50s for the two groups was > or =64-fold. The MIC50s foro beta-haemolytic streptococci, classified by Lancefield group, were in the range 0.015 to 0.06 mg/L for HMR 3647. H. influenzae were categorized into three groups according to cefuroxime MIC: <1 mg/L (n = 72); 2-4 mg/L (n = 29); and >4 mg/L (n = 42). The MIC50 of HMR 3647 increased two-fold with increasing cefuroxime MICs; beta-lactam MICs increased much more markedly. The MIC50 of HMR 3647 for M. catarrhalis was 0.03 mg/L. HMR 3647 has good activity against respiratory tract pathogens but in-vitro susceptibility is affected by erythromycin A susceptibility in S. pneumoniae and beta-haemolytic streptococci.

Anti-Bacterial Agents↗
PubMed1999

Comparison of in-vitro pharmacodynamics of once and twice daily ciprofloxacin.

The pharmacodynamics of ciprofloxacin were explored in an in-vitro continuous bacterial culture model of infection, by simulating two oral dosing regimens; 0.5 g 12-hourly (bd) and 1 g 24-hourly (od). Three strains of Escherichia coli (ciprofloxacin MICs 0.03, 0.5 and 2 mg/L); two strains of Pseudomonas aeruginosa (MICs 0.09 and 1.5 mg/L), two strains of Staphylococcus aureus (MICs 0.12 and 1 mg/L) and two strains of Streptococcus pneumoniae (MICs 0.5 and 2 mg/L) were used. Three pharmacodynamic parameters, T > MIC, C(max)/MIC and AUC/MIC (T = time, C(max) = peak serum concentration, AUC = area under the curve), were compared with area under the bacterial-kill curve (AUBKC) (after transformation of the AUBKC) using a simple E(max) or sigmoidal E(max) model. AUBKC was taken to be the main antibacterial effect measure. The models were compared by inspection of residuals and Akaike information criterion. E(max) models adequately described the relationship between AUC/MIC and AUBKC and between C(max)/MIC and AUBKC, but not between T> MIC and AUBKC. All three pharmacodynamic parameters are related to each other but multiple regression analysis indicated that AUC/MIC was the best individual predictor of AUBKC. Despite this, comparison of od and bd regimens indicates some advantage to od in terms of early antibacterial effect. Serum concentration-time curve shape has some importance in determining antibacterial effect. These data indicate that for ciprofloxacin AUC/MIC ratio is not the sole determinant of antibacterial effect.

Anti-Infective Agents↗
PubMed1999

Expression and detection of hetero-vancomycin resistance in Staphylococcus aureus.

Isolates of Staphylococcus aureus resistant to vancomycin have been reported but appear to be extremely rare. However, isolates displaying hetero-resistance to vancomycin (hVRSA) are reportedly common in parts of Japan (9.3% of MRSA isolated from a group of university hospitals). We have investigated the reliability of the proposed method for detection of hetero-resistant isolates and the ability of clinical S. aureus isolates to express vancomycin resistance. The original method for identification of hVRSA was found to have poor reproducibility and may select for, rather than detect, vancomycin resistance. There appears to be a spectrum of heterogeneity in the expression of resistance to vancomycin among S. aureus. Until there is a clearer understanding of the mechanism and control of vancomycin resistance in S. aureus, and reliable tests are devised, the clinical relevance of different degrees of hetero-resistance cannot be assessed.

Anti-Bacterial Agents↗
PubMed1999

Exploration of the in-vitro pharmacodynamic activity of moxifloxacin for Staphylococcus aureus and Streptococci of lancefield groups A and G.

The serum concentrations associated with the oral administration of 400 mg moxifloxacin every 24 h over 48 h in man were simulated in an in-vitro dilutional, continuous bacterial culture model of infection. The initial inoculum was 5 x 10(7)-5 x 10(8) cfu/mL and all strains were tested on at least three occasions. Two strains of Staphylococcus aureus (one methicillin susceptible, the other resistant) with moxifloxacin MICs 0.14 mg/L and 0.06 mg/L and two strains of beta-haemolytic streptococci, Lancefield Group A, MIC 0. 16 mg/L and Group G, MIC 0.4 mg/L were used. In addition, two laboratory-generated mutants with raised moxifloxacin MICs were also employed: methicillin-sensitive S. aureus (MSSA) MIC 1.0 mg/L and Group A streptococcus MIC 1.8 mg/L. The antibacterial effect of moxifloxacin was judged by changes in viable count over time, and the area under the bacterial-kill curve (AUBKC) after 24 and 48 h. For S. aureus MIC 0.14 mg/L the AUBKC(24) (log cfu/mL.h) was 77.8 +/- 4.6 and AUBKC(48) 92.0 +/- 6.9. For its mutant, moxifloxacin MIC 1.0 mg/L, the AUBKC(24) was 116.1 +/- 15.6 and AUBKC(48) 211.9 +/- 23.1, indicating decreased killing. AUBKC(24) and AUBKC(48) values of 110.7 +/- 10.3 and 130.9 +/- 21.3, respectively, were noted for the MRSA strain. The Group A streptococcus, MIC 0.16 mg/L, had an AUBKC(24) of 91.4 +/- 19.4 and AUBKC(48) of 157.0 +/- 70.9. The mutant, MIC 1.8 mg/L, had an AUBKC(24) of 127.0 +/- 1.9 and AUBKC(48) of 205.1 +/- 6.4. Despite a lower MIC (0.4 mg/L) the single strain of Group G streptococcus tested was killed poorly, AUBKC(24) 139.9 +/- 3.6 and AUBKC(48) 252.3 +/- 18.6. The pharmacodynamic parameters AUC/MIC, T > MIC, (AUC > MIC)/MIC (AUC = area under the curve, T = time) and WAUC ((AUC/MIC) (T > MIC/100)) (WAUC = weighted area under the curve) were related to AUBKC(24) and AUBKC(48) using an inhibitory sigmoid E(max) model. T > MIC was poorly related to AUBKC (r = 0.36) while AUC/MIC, (AUC > MIC)/MIC and WAUC were strongly related to AUBKC(24) (r = 0.75-0.79) and AUBKC(48) (r = 0.78-0.84). The maximum antibacterial effect was achieved with an AUC/MIC ratio of 150-200. AUC-related pharmacodynamic parameters predicted antibacterial effect better than T > MIC.

Anti-Infective Agents↗
PubMed1999

Activity of moxifloxacin, administered once a day, against Streptococcus pneumoniae in an in vitro pharmacodynamic model of infection.

The antibacterial effect of moxifloxacin was studied by using an in vitro pharmacodynamic model of infection with dosing simulations of 400 mg every 24 h for 48 h. Streptococcus pneumoniae was tested by using four wild-type strains for which the moxifloxacin MICs were 0. 008, 0.12, 0.14, and 3.6 mg/liter. In addition, two isogenic mutants, generated from the strains for which the moxifloxacin MICs were </=0.12 mg/liter and for which the MICs were 1.0 and 1.6 mg/liter, were also used. Antibacterial efficacy was measured by the following indices: log change in viable count at 12, 24, 36, and 48 h; area under the bacterial kill curve (AUBKC); and time to kill 99.9% of the initial inoculum. With the three strains for which the moxifloxacin MICs were </=0.14 mg/liter, there was a marked reduction in viable count over 12 to 36 h; in contrast, with strains for which the MICs were >/=1.0 mg/liter, little killing occurred over 48 h. A sigmoid dose-response model indicated that the area under the curve/MIC ratio was strongly related to the log change in viable count at 24 and 48 h and to the AUBKC. These data indicate that moxifloxacin may have a role in management of S. pneumoniae infection.

Anti-Infective Agents↗