Person: Sevillano Fernández, David
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First Name
David
Last Name
Sevillano Fernández
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Medicina
Department
Medicina
Area
Microbiología
Identifiers
46 results
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Now showing 1 - 10 of 46
Item Effects of human albumin and serum on the in vitro bactericidal activity of cefditoren against penicillin-resistant Streptococcus pneumoniae(Journal of Antimicrobial Chemotherapy, 2007) Sevillano Fernández, David; Giménez, María José; Alou Cervera, Luis; Aguilar, Lorenzo; Cafini, Fabio; Torrico, Martha; González Hidalgo, Natalia; Echeverría, Olatz; Coronel, Pilar; Prieto Prieto, JoséObjectives: Attempts to interpret antibiotic pharmacodynamics using reported protein binding may underestimate true activity. To elucidate this issue we examined bacterial killing kinetics at cefditoren concentrations equal to C(max) in the presence of 90% human serum or albumin at physiological concentrations. Methods: Killing curves (final inocula of approximately 10(7) cfu/mL, cefditoren concentration of 4.2 mg/L) were performed against Streptococcus pneumoniae strains exhibiting cefditoren MICs (mg/L) of 0.12 (strain 1), 0.25 (strain 2) and 0.5 (strain 3) in different media: (i) C(max)-MH, Mueller-Hinton broth plus 5% lysed horse blood (MH), (ii) C(max)-HS, MH broth with a final human serum concentration of 90%; and (iii) C(max)-HAlb, MH broth with 4 g/dL human albumin. Killing curves were also performed with a final cefditoren concentration of 0.5 mg/L (similar to free-drug C(max) considering 88% protein binding) in MH broth (12% C(max)). Results: No significant differences were found between the different media or concentrations with strain 1 (log(10) reductions >or=4 at 24 h). Against strains 2 and 3, we observed significantly higher initial inocula decreases at 24 h for C(max)-HS as compared with C(max)-HAlb or 12% C(max). Bactericidal activity (>or=3 log(10) reduction) was obtained at 24 h against the three strains only with C(max)-HS and C(max)-MH. Conclusions: The presence of physiological concentrations of human albumin, but not 90% human serum, limited bactericidal activity as did the use of concentrations similar to free-drug C(max), suggesting that extrapolation of active drug from total drug by using the protein binding rate is not an accurate method to study antibacterial activity.Item Is there a pharmacodynamic need for the use of continuous versus intermittent infusion with ceftazidime against Pseudomonas aeruginosa? An in vitro pharmacodynamic model(Journal of Antimicrobial Chemotherapy, 2005) Alou Cervera, Luis; Aguilar, Lorenzo; Sevillano Fernández, David; Giménez, María José; Echeverría, Olatz; Gómez-Lus Centelles, María Luisa; Prieto Prieto, JoséObjectives: In order to explore the pharmacodynamic need for continuous versus intermittent (three times a day) administration of ceftazidime in critically ill patients, a pharmacokinetic computerized device was used to simulate concentrations of ceftazidime in human serum after 6 g/day. Methods: Efficacy was measured as the capability of simulated concentrations over time to reduce initial inoculum against four strains of Pseudomonas aeruginosa. MICs of the strains matched NCCLS breakpoints: one susceptible strain (MIC = 8 mg/L), two intermediate strains (MIC = 16 mg/L) and one resistant strain (MIC = 32 mg/L). C(max) was 119.97+/-2.53 mg/L for intermittent bolus and C(ss) (steady-state concentration) was 40.38+/-0.16 mg/L for continuous infusion. AUC(0-24) was similar for both regimens (approximately 950 mg x h/L). Inhibitory quotients were three times higher for the intermittent administration whereas t > MIC was higher for continuous infusion (100%) versus intermittent administration (99.8%, 69% and 47.6% for the susceptible, intermediate and resistant strains, respectively). Results: Against the susceptible and intermediate strains, no differences were found between both regimens with > or = 3 log10 reduction from 8 to 24 h. Against the resistant strain, only the continuous infusion achieved this bactericidal activity in the same time period, minimizing the differences between resistant and susceptible strains. Significantly higher initial inoculum reduction at 32 h was obtained for the continuous versus the intermittent administration (83.35% versus 38.40%, respectively). Conclusions: These results stress the importance of optimizing t >MIC, even at peri-MIC concentrations, of ceftazidime against resistant strains. Local prevalence of resistance justifies, on a pharmacodynamic basis, electing for continuous infusion versus intermittent administration.Item Efficacy of Preoperative and Intraoperative Skin and Nail Surgical Preparation of the Foot in Reducing Bacterial Load(Dermatologic Surgery, 2010) Becerro De Bengoa Vallejo, Ricardo; Losa Iglesias, Marta Elena; Alou Cervera, Luis; Sevillano Fernández, David; Prieto Prieto, JoséBackground: A common problem associated with toenail removal surgery is the accompanying bacterial infection that often ensues. The foot has a particularly difficult anatomy to prepare antiseptically for surgery, which contributes to this wide-spread problem. Objective: To compare the antiseptic efficacy of two skin pretreatment methods before toenail avulsion surgery. Methods: Two presurgical methods were performed on 24 patients each (48 patients total). Swab samples were taken from each patient at five distinct stages (pretreatment, post-treatment, after surgery, after saline solution irrigation of the nail bed, and after phenol application) throughout the surgical procedure, and bacterial culture analysis was performed (total inocula count and identification of specific microorganisms). Results: We found both methods to be effective at reducing the initial bacterial load when used at pretreatment, but the reduction in bacterial load was lost after the nail avulsion surgery, achieving values similar to the initial bacterial load before the presurgical scrub, from 5.17 and 5.04 log(10) colony-forming units (CFU)/cm(2) to 4.86 and 5.07 log(10) CFU/cm(2), respectively. An interoperative irrigation step was effective in reducing the bacterial load by 95.2% and 95.3%, respectively. Study limitations: Our patients underwent phenol-based nail avulsion, resulting in no bacterial load after complete nail removal because of the intrinsic antiseptic nature of the phenol. Conclusions: Incorporation of intraoperative irrigation of sterile saline solution after nail avulsion surgery reduces potential bacterial load. Every effort should be made to lower the risk of contamination after nail plate avulsion.Item β-Lactam Activity against Penicillin-Resistant Streptococcus pneumoniae Strains Exhibiting Higher Amoxicillin versus Penicillin Minimum Inhibitory Concentration Values: An in vitro Pharmacodynamic Simulation(Chemotherapy, 2008) Sevillano Fernández, David; Aguilar, Lorenzo; Alou Cervera, Luis; Giménez, María José; González Hidalgo, Natalia; Echeverría, Olatz; Torrico, Martha; Valdes, Laura; Coronel, Pilar; Prieto Prieto, JoséBackground: Activity of simulated serum concentrations after oral therapy with 400 mg cefditoren pivoxil b.i.d., 500 mg cefuroxime axetil b.i.d. and 875/125 mg amoxicillin/clavulanic acid b.i.d. and t.i.d. regimens was explored over 24 h against Streptococcus pneumoniae.Methods: Computerized pharmacodynamic simulations were performed against strains with penicillin/amoxicillin/cefuroxime/cefditoren minimum inhibitory concentrations (MICs, µg/ml) and serotypes: strain 1 (0.25/0.12/1/0.12; serotype 6A), strain 2 (2/4/ 2/0.25; serotype 6B), strain 3 (4/16/4/0.5; serotype 14), and strain 4 (4/16/8/1; serotype 14). Results: Bactericidal activity (≧3 log10 reduction) at 12 and 24 h was obtained against all strains with cefditoren, against strains 1 and 2 with cefuroxime and amoxicillin/clavulanic acid t.i.d., but only against strain 1 with amoxicillin/clavulanic acid b.i.d.. Bactericidal activity at 24 h was related to T > MIC of >30% dosing interval, 1.7–2.0 log10 reductions with T > MIC of 20–30%, and <1 log10 reduction or regrowth with T > MIC of 0%. Conclusions: It is difficult to achieve pharmacodynamic coverage and bactericidal activity by physiological concentrations of oral β-lactams against penicillin-resistant pneumococcal strains exhibiting higher amoxicillin versus penicillin MICs. Cefditoren may offer alternatives.Item Bactericidal activity of moxifloxacin against multidrug-resistant Streptoccocus pneumoniae at clinically achievable serum and epithelial lining fluid concentrations compared with three other antimicrobials(International Journal of Antimicrobial Agents, 2004) Cafini, Fabio; Alou Cervera, Luis; Sevillano Fernández, David; Valero, Eva; Prieto Prieto, JoséTime-kill studies compared the activities of moxifloxacin with those of levofloxacin, azithromycin and amoxicillin-clavulanate against 10 pneumococcal strains with various drug susceptibilities. Three Streptococcus pneumoniae strains were resistant to moxifloxacin: 6, 7 and 2 strains were resistant to levofloxacin, azithromycin and amoxicillin-clavulanate, respectively. Of these, 1 strain was resistant to all antimicrobial agents studied. Moxifloxacin and amoxicillin-clavulanate were bactericidal after 24h at serum Cmax levels against 9 and 8 strains, respectively, while levofloxacin and azithromycin were bactericidal against 3 and 2 strains, respectively. A higher activity was only observed for amoxicillin-clavulanate for logarithmic phase cultures at 1, 4 and 8h compared with stationary phase organisms. Amoxicillin-clavulanate and moxifloxacin were bactericidal at free serum levels (protein unbound) after 24h against 8 and 3 strains, respectively. Moxifloxacin was bactericidal at epithelial lining fluid levels against all strains at 24h, including one moxifloxacin, amoxicillin-clavulanate and azithromycin-resistant strain; lower levels of bactericidal activity was observed for levofloxacin, azithromycin and amoxicillin-clavulanate against 7, 2 and 4 strains, respectively. This demonstrated the importance of moxifloxacin tissue levels.Item Evolving architectural patterns in microbial colonies development(Microscopy Research and Technique, 2010) Gómez‐Aguado, Fernando; Alou Cervera, Luis; Corcuera, María Teresa; Sevillano Fernández, David; Alonso, María José; Gómez-Lus Centelles, María Luisa; Prieto Prieto, JoséAbstract Semithin sections of colonies of three ATCC strains (Staphylococcus aureus, Escherichia coli, and Candida albicans) showed that their internal structure had specific patterns that evolved over the time. These patterns generally were defined by the presence of different layers composed of microorganisms with variable population densities and dead cells. The observed structures in this study could be explained as a particular form of biofilm with an air-semisolid interface.Item Cefditoren versus ceftazidime in inducer-substrate combinations for the evaluation of AmpC production in a disc approximation test(Revista Española de Quimioterapia, 2010) Cafini, Fabio; Aguilar, Lorenzo; Alou Cervera, Luis; Giménez, María José; Sevillano Fernández, David; Torrico, Martha; González Hidalgo, Natalia; Coronel, Pilar; Prieto Prieto, JoséObjective: To evaluate cefditoren in inducer-substrate combinations to screen for AmpC induction. Methods: 100 clinical isolates (25 P. aeruginosa, 25 E. cloacae, 14 M. morganii, 13 S. marcescens, 12 C. freundii, 7 P. rettgeri, and 4 E. aerogenes) were tested by the Kirby-Bauer disc approximation method using cefditoren and ceftazidime discs as substrates, and cefditoren and imipenem discs as inducers. Results: None of the strains showed induction of AmpC with cefditoren-ceftazidime as inducer-substrate combination. Imipenem-cefditoren as inducer-substrate combination was not useful for evaluating strains of P. aeruginosa since no inhibition zones surrounding the cefditoren disc were found. Among evaluable enterobacteria (those showing substrate inhibition zone), inducible Amp C was detected in 48 out of 63 (76.2%) with cefditoren, and in 33 out of 68 (48.5%) isolates with ceftazidime as substrate. Significantly (p=0.013) higher number of AmpC producers were detected with cefditoren versus ceftazidime (76.2% vs. 48.5%), due to the differences found for E. cloacae (72.8% vs. 21.7%; p=0.0009) and S. marcescens (100% vs. 54.5%; p=0.03). Higher mean reductions of diameters around substrate discs were found for cefditoren (4.17 mm) vs. ceftazidime (3.79 mm), reaching statistical significance (p<0.05) for indol-positive proteae: M. morganii (5.32 mm vs. 3.92 mm) and P. rettgeri (3.47 mm vs. 2.64 mm). Conclusion: Cefditoren showed no induction capability, and when used as substrate (with imipenem as inducer) it offered detection rates of AmpC inducible enterobacteria higher than the imipenem-ceftazidime combination, mainly for Enterobacter spp. and Serratia spp., with higher diameter reductions for indol-positive proteae.Item Decrease in Bacterial Load Versus Resistance Selection of Pneumococcal Subpopulations by β-Lactam Physiological Concentrations over Time: An In Vitro Pharmacodynamic Simulation(Microbial Drug Resistance, 2008) Cafini, Fabio; Aguilar, Lorenzo; Sevillano Fernández, David; Giménez, María José; Alou Cervera, Luis; Fenoll, Asunción; Echevarría, Olatz; Torrico, Martha; González Hidalgo, Natalia; Coronel, Pilar; Prieto Prieto, JoséTo investigate β-lactam effects on Streptococcus pneumoniae–mixed cultures, a computerized pharmacodynamic model simulating over 24-hr concentrations obtained after several β-lactam regimens was used. Strain 1 (no penicillin binding protein [PBP] mutations) and strain 2 (mutation in pbp1a) were penicillin/amoxicillin susceptible. Strain 3 (mutations in pbp1a, pbp2x, and pbp2b) and strain 4 (mutations in pbp1a, pbp2x, and pbp2b [10 changes]) were penicillin/amoxicillin resistant. Initial inoculum was approximately 6 × 106 CFU (colony forming units)/ml (with a 1:1:1:1 proportion of each strain). Population analysis profile was performed pre- and postsimulations. Strain 1 exhibited the best fitness (growth over 24 hr) in individual cultures, and strain 2 did so in mixed cultures in antibiotic-free simulations. In antibiotic simulations with the mixed inocula, penicillin/amoxicillin-susceptible strains were eradicated with all study drugs (time that concentrations exceed the minimal inhibitory concentration [T > MIC ≥ 43%]). Penicillin-resistant strains showed different evolution depending on the antibiotic: (a) cefditoren produced >2 log10 reduction of initial inocula at 12–24 hr (T>MIC ≥45%), with a remaining population growing in plates with ≥4 mg/L amoxicillin; (b) cefuroxime, cefixime, and cefaclor did not decrease initial inocula at 12–24 hr (T > MIC = 0%), with minor subpopulations growing in plates with 4 mg/L amoxicillin; (c) amoxicillin produced 2.6 log10 decrease of initial inocula at 12 hr (T>MIC = 47.5%), but 1.1 log10 increase of initial inocula at 24 hr, with a significant population growing in plates with 4 mg/L amoxicillin. Antibiotic activity against mixed inocula (susceptible and resistant strains) depends on intrinsic activity (as well as its subsequent pharmacodynamic activity: T > MIC against resistant strains), and on possible selection of intra-strain-resistant subpopulations.Item Evaluation of two in vitro pharmacodynamic simulation models: microfiltration versus centrifugation–filtration(International Journal of Antimicrobial Agents, 2001) Alou Cervera, Luis; Sevillano Fernández, David; Bugella, Javier H.; Fuentes, Fernando; Gómez-Lus Centelles, María Luisa; Prieto Prieto, JoséPharmacodynamic in vitro models that simulate serum antimicrobial concentrations provide more information about the activity of an antibiotic than MICs or traditional time-kill methods. The aim of this study was to compare two pharmacodynamic simulation models using ATCC strains of five different species and five antibiotics. In the first model (Centriprep-10 system), a filtration-centrifugation process was used to eliminate the antibiotic; in the second model (microfiltration system) no centrifugation was necessary. The antibiotic concentrations tested were similar to those in serum after normal doses of cefuroxime, clarithromycin, ciprofloxacin, gentamicin and cefotaxime. No significant differences were observed in the killing rates between the models except in the case of Haemophilus influenzae and cefotaxime. The new microfiltration model had the following advantages: lack of the carry-over effect, the absence of centrifugation that could damage bacteria and the possibility of increasing the number of incubation periods to give a better fit of the kinetic profile of man.Item Exposure–response analysis of tigecycline in pharmacodynamic simulations using different size inocula of target bacteria(International Journal of Antimicrobial Agents, 2010) Sevillano Fernández, David; Aguilar, Lorenzo; Alou Cervera, Luis; Giménez, María José; González Hidalgo, Natalia; Torrico, Martha; Cafini. Fabio; Garcia-Rey, César; Garcia-Escribano, Natalia; Prieto Prieto, JoséThis study explored tigecycline exposure-bacterial responses in pharmacodynamic simulations (in vitro kinetic model) using different inocula. One meticillin-resistant vancomycin-heteroresistant Staphylococcus aureus, one Enterococcus faecium and one extended-spectrum beta-lactamase-producing Escherichia coli with equal tigecycline minimum inhibitory concentrations/minimum bactericidal concentrations (MICs/MBCs) (0.12/0.25 microg/mL) were used. A computerised pharmacodynamic bicompartmental model simulated three tigecycline twice-daily dosing regimens over 48h: 50mg (100mg loading dose); 100mg; and 150 mg. Areas under bacterial growth curves were calculated, and differences between the growth curve used as control and the killing curve of bacteria exposed to tigecycline (ABBC) were determined. With standard inocula [ca. 1 x 10(6)colony-forming units (CFU)/mL], linear increases in area under the concentration-time curve (AUC)/MIC (25.6 for 50mg, 53.76 for 100mg and 79.52 for 150 mg) produced linear increases in activity against Gram-positive organisms (mean ABBCs of 120.60, 143.20 and 195.80 log CFU x h/mL for S. aureus and of 95.75, 172.55 and 216.90 log CFUxh/mL for E. faecium, respectively), with the activity of the 150 mg regimen being significantly higher (P<0.01) than that of the other two regimens. ABBCs obtained with the 100mg regimen using standard inocula were similar to those obtained with the 150 mg regimen when using high inocula (ca. 1 x 10(7)CFU/mL). Against E. coli, the highest dosing regimen was required to obtain significant antibacterial activity compared with control (mean ABBCs of 145.75 log CFU x h/mL with standard inocula and 63.33 log CFU x h/mL with high inocula). An increase in tigecycline dosing appears to be an interesting therapeutic option to maximise antibacterial activity owing to its linear pharmacokinetics and pharmacodynamics, especially when severe infections with high bacterial load are suspected.