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
56 results
Search Results
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Item Impact of the biotic and abiotic components of low mineralized natural mineral waters on the growth of pathogenic bacteria of human origin: A key to self-control of spa water quality(Journal of Hydrology, 2018) Sevillano Fernández, David; Romero Lastra, Patricia T.; Casado Gómez, Inmaculada; Alou Cervera, Luis; González Hidalgo, Natalia; Collado Yurrita, Luis Rodolfo; Domínguez Gordillo, Adelaida Africa; Arias, Caridad M.; Corvillo Martín, Iluminada; Armijo Castro, Francisco; Romero Martín, Margarita; Maraver Eyzaguirre, Francisco De PaulaIn order to assess the role of the biotic and abiotic components of natural mineral water (NMW) in the spread of allochthonous bacteria in non-thermal spa facilities, we examined the effect of low mineralized NMWs on the growth of several commensal and pathogenic human strains. These NMWs were collected from two Spanish spring spas and had different microbiological characteristics. Microorganisms were exposed to untreated, filtered and autoclaved NMWs at the temperatures of 22 °C and 37 °C for 2 days, mimicking the early stage of starvation. Starvation stress was controlled by the effect identified after incubation in saline. Changes in culturability after exposure were used as a measure of the water’s antibacterial effect. The specific biotic and abiotic effect of NMWs on the suppression of bacterial growth was estimated after excluding the bacterial response to starvation stress, characteristic of this natural oligotrophic environment. The incubation temperature strongly modulated both the consequences of starvation and the impact of the natural biotic and abiotic components of NMWs on the growth of commensal and pathogenic bacteria. A temperature of 22 °C conferred cross-protection of microorganisms to starvation and NMW abiotic stress, whereas a temperature of 37 °C decreased the tolerance to both, and had a negative influence on the abundance and diversity of NMWs microflora. This temperature-dependent behaviour of the allochthonous and autochthonous bacteria explained the different culturability of microorganisms after exposure to untreated NMWs at 22 °C (≈1–2.4 log colony forming units per ml -CFU/ml- mean reduction) and at 37 °C (≈1.8–3.2 log CFU/ml mean reduction). Discarding the effect of starvation, we estimated that the antibacterial effect of NMWs at the temperature of 22 °C was mainly driven by the microecosystem of NMWs, which explained ≥95% of NMW response. In contrast, at optimal temperatures for the growth of commensal and pathogenic microorganisms, ≥60% of the antibacterial response of NMWs was associated with the abiotic components of NMWs. The biotic and abiotic components of NMWs self-preserve the quality of water, preventing the progression of human pathogenic organisms that can occasionally cause water colonization. The influence of the intrinsic components of NMWs on the suppression of microbial growth is strongly modulated by environmental temperature.Item Effect of the Medium Composition on the Zn2+ Lixiviation and the Antifouling Properties of a Glass with a High ZnO Content(Materials, 2017) Esteban Tejeda, Leticia; Palomares, Francisco; Cabal, Belén; López Píriz, Roberto; Fernández, Adolfo; Sevillano Fernández, David; Alou Cervera, Luis; Torrecillas, Ramón; Moya, JoséThe dissolution of an antimicrobial ZnO-glass in the form of powder and in the form of sintered pellets were studied in water, artificial seawater, biological complex media such as common bacterial/yeast growth media (Luria Bertani (LB), yeast extract, tryptone), and human serum. It has been established that the media containing amino acids and proteins produce a high lixiviation of Zn2+ from the glass due to the ability of zinc and zinc oxide to react with amino acids and proteins to form complex organic compounds. The process of Zn2+ lixiviation from the glass network has been studied by X-ray photoelectron spectroscopy (XPS). From these results we can state that the process of lixiviation of Zn2+ from the glass network is similar to the one observed in sodalime glasses, where Na+ is lixiviated to the media first and the fraction of Zn that acts as modifiers (~2/3) is lixiviated in second place. After the subsequent collapse of the outer surface glass layer (about 200–300 nm thick layer) the dissolution process starts again. Antifouling properties against different bacteria (S. epidermidis, S. aureus, P. aeruginosa, E. coli, and M. lutea) have also been established for the glass pellets.Item A New Biocompatible and Antibacterial Phosphate Free Glass-Ceramic for Medical Applications(Scientific Reports, 2014) Cabal, Belén; Alou Cervera, Luis; Cafini, Fabio; Couceiro, Ramiro; Sevillano Fernández, David; Esteban Tejeda, Leticia; Guitián, Francisco; Torrecillas, Ramón; Moya, José S.In the attempt to find valid alternatives to classic antibiotics and in view of current limitations in the efficacy of antimicrobial-coated or loaded biomaterials, this work is focused on the development of a new glass-ceramic with antibacterial performance together with safe biocompatibility. This bactericidal glass-ceramic composed of combeite and nepheline crystals in a residual glassy matrix has been obtained using an antimicrobial soda-lime glass as a precursor. Its inhibitory effects on bacterial growth and biofilm formation were proved against five biofilm-producing reference strains. The biocompatibility tests by using mesenchymal stem cells derived from human bone indicate an excellent biocompatibility.Item Enhanced In Vivo Activity of Cefditoren in Pre-Immunized Mice against Penicillin-Resistant S. pneumoniae (Serotypes 6B, 19F and 23F) in a Sepsis Model(PLoS One, 2010) Cafini, Fabio; Yuste, Jose; Giménez, María José; Sevillano Fernández, David; Aguilar, Lorenzo; Alou Cervera, Luis; Ramos Sevillano, Elisa; Torrico, Martha; González Hidalgo, Natalia; García, Ernesto; Coronel, Pilar; Prieto Prieto, José; Michael OttoBackground: Specific antibodies are likely to be present before S. pneumoniae infection. We explored cefditoren (CDN) total and free values of serum concentrations exceeding the MIC (t>MIC) related to efficacy in a mice sepsis model, and the effect of specific gammaglobulins on in-vitro phagocytosis and in-vivo efficacy. Methodology/principal findings: We used three pneumococcal isolates (serotype, MIC OF CDN): Strain 1 (6B, 1 microg/ml), Strain 2 (19F, 2 microg/ml) and Strain 3 (23F, 4 microg/ml). Hyperimmune serum (HS) was obtained from mice immunized with heat-inactivated strains. In-vitro, phagocytosis by HS diluted 1/10 in presence/absence of sub-inhibitory concentrations was measured by flow cytometry including fluorescent bacteria and a neutrophil cell line. In-vivo dose-ranging experiments with HS (dilutions 1/2-1/16) and CDN (6.25 mg/kg-100 mg/kg tid for 48 h) were performed to determine the minimal protective dilution/dose (highest survival) and the non-protective highest dilution/dose (highest mortality: HS-np dilution and CDN-np dose) over 7 days. Efficacy of CDN-np in animals pre-immunized with HS-np (combined strategy) was explored and blood bacterial clearance determined. The CDN measured protein binding was 86.9%. In-vitro, CDN significantly increased phagocytosis (vs. HS 1/10). In non pre-immunized animals, t>MIC values for CDN of approximately 35% (total) and approximately 19% (free) were associated with 100% survival. Significant differences in survival were found between HS-np alone (< or = 20%) or CDN-np alone (< or = 20%) vs. the combined strategy (90%, 60% and 60% for Stains 1, 2 and 3), with t>MIC (total/free) of 22.8%/14.3%, 26.8%/16.0%, and 22.4%/12.7% for Strains 1, 2 and 3, respectively. Prior to the second dose (8 h), median bacterial counts were significantly lower in animals surviving vs. dead at day 7. Conclusions/significance: In mice (CDN protein binding similar to humans) total t>MIC values of approximately 35% (approximately 19% free) were efficacious, with a decrease in the required values in pre-immunized animals. This reinforces that immunoprotection to overcome resistance may provide lifesaving strategies.Item Efficacy of simulated cefditoren versus amoxicillin-clavulanate free concentrations in countering intrastrain ftsI gene diffusion in Haemophilus influenzae(Antimicrobial Agents and Chemotherapy, 2011) González Hidalgo, Natalia; Aguilar, Lorenzo; Sevillano Fernández, David; Giménez, María José; Alou Cervera, Luis; Cafini, Fabio; Torrico, Martha; López, Ana María; Coronel, Pilar; Prieto Prieto, JoséThis study explores the effects of cefditoren (CDN) versus amoxicillin-clavulanic acid (AMC) on the evolution (within a single strain) of total and recombined populations derived from intrastrain ftsI gene diffusion in β-lactamase-positive (BL+) and β-lactamase-negative (BL−) Haemophilus influenzae. DNA from β-lactamase-negative, ampicillin-resistant (BLNAR) isolates (DNABLNAR) and from β-lactamase-positive, amoxicillin-clavulanate-resistant (BLPACR) (DNABLPACR) isolates was extracted and added to a 107-CFU/ml suspension of one BL+ strain (CDN MIC, 0.007 μg/ml; AMC MIC, 1 μg/ml) or one BL− strain (CDN MIC, 0.015 μg/ml; AMC MIC, 0.5 μg/ml) in Haemophilus Test Medium (HTM). The mixture was incubated for 3 h and was then inoculated into a two-compartment computerized device simulating free concentrations of CDN (400 mg twice a day [b.i.d.]) or AMC (875 and 125 mg three times a day [t.i.d.]) in serum over 24 h. Controls were antibiotic-free simulations. Colony counts were performed; the total population and the recombined population were differentiated; and postsimulation MICs were determined. At time zero, the recombined population was 0.00095% of the total population. In controls, the BL− and BL+ total populations and the BL− recombined population increased (from ≈3 log10 to 4.5 to 5 log10), while the BL+ recombined population was maintained in simulations with DNABLPACR and was decreased by ≈2 log10 with DNABLNAR. CDN was bactericidal (percentage of the dosing interval for which experimental antibiotic concentrations exceeded the MIC [ft>MIC], >88%), and no recombined populations were detected from 4 h on. AMC was bactericidal against BL− strains (ft>MIC, 74.0%) in DNABLNAR and DNABLPACR simulations, with a small final recombined population (MIC, 4 μg/ml; ft>MIC, 30.7%) in DNABLPACR simulations. When AMC was used against the BL+ strain (in DNABLNAR or DNABLPACR simulations), the bacterial load was reduced ≈2 log10 (ft>MIC, 44.3%), but 6.3% and 32% of the total population corresponded to a recombined population (MIC, 16 μg/ml; ft>MIC, 0%) in DNABLNAR and DNABLPACR simulations, respectively. AMC, but not CDN, unmasked BL+ recombined populations obtained by transformation. ft>MIC values higher than those classically considered for bacteriological response are needed to counter intrastrain ftsI gene diffusion by covering recombined populations.Item Activity of simulated serum concentrations of daptomycin versus vancomycin during the first 24h of treatment in the presence of physiological albumin concentrations against vancomycin-susceptible, -tolerant or -intermediate-resistant Staphylococcus aureus(International Journal of Antimicrobial Agents, 2011) Torrico, Martha; Aguilar, Lorenzo; Sevillano Fernández, David; Giménez, María José; Alou Cervera, Luis; González Hidalgo, Natalia; Cafini, Fabio; Cleeland, Roy; Prieto Prieto, JoséIn order to determine whether reduced susceptibility or tolerance to vancomycin in Staphylococcus aureus influences the activity of daptomycin by simulating serum concentrations in the first 24h of treatment in the presence of physiological concentrations of human albumin, a computerised pharmacodynamic simulation was performed using Mueller-Hinton broth with 4 g/dL human albumin concentrations. For daptomycin, the media was adjusted to physiological ionised calcium concentrations by adding 100 μg/mL Ca(2+). Protein binding was measured. Six S. aureus isolates were used, comprising one vancomycin-susceptible S. aureus (VSSA), three vancomycin-tolerant strains, one heteroresistant vancomycin-intermediate S. aureus (hVISA) and one homogeneous vancomycin-intermediate S. aureus (VISA). Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of daptomycin increased eight times when determined in the presence of albumin (MIC(ALB) and MBC(ALB), respectively). Measured protein binding was 86.6% (C(max)) and 86.5% (C(min)) for daptomycin and 51.6% (C(max)) and 42.2% (C(min)) for vancomycin. Similar values were obtained for fAUC/MIC (where fAUC is the area under the concentration-time curve obtained with extrapolated concentrations using the highest protein binding rate experimentally obtained) and AUC/MIC(ALB) for each antibiotic. Daptomycin showed early (≤ 6 h) bactericidal activity [maximal effect (E(max)) >4 log(10) reductions in initial inocula] against all strains. Vancomycin produced an E(max) of 2.3 log(10) reductions at 8h against the VSSA and reductions ≤1.8 log(10) for the other strains in the 8-24h period. Pharmacodynamic parameters were fAUC/MBC from 8.0 to 15.6 (vancomycin) and from 56.0 to 111.6 (daptomycin) for tolerant strains, and fAUC/MIC of 126.8 and 63.3 for vancomycin and 222.6 and 113.2 for daptomycin against hVISA and VISA strains, respectively. Against the study strains (vancomycin-susceptible, -tolerant, heteroresistant or intermediate), daptomycin, in contrast to vancomycin, exhibited early bactericidal activity despite its high protein binding.Item Influence of the MBC/MIC ratio on the antibacterial activity of vancomycin versus linezolid against methicillin-resistant Staphylococcus aureus isolates in a pharmacodynamic model simulating serum and soft tissue interstitial fluid concentrations reported in diabetic patients(Journal of Antimicrobial Chemotherapy, 2013) González Hidalgo, Natalia; Sevillano Fernández, David; Alou Cervera, Luis; Cafini, Fabio; Gimenez, María José; Gómez-Lus Centelles, María Luisa; Prieto Prieto, José; Aguilar, LorenzoObjectives: To explore serum and tissue pharmacodynamics of linezolid versus vancomycin against methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates with different MBC/MIC ratios. Methods: Five strains (vancomycin MIC/MBCs, mg/L) were used: TOL-1 (2/≥64), TOL-2 (1/16), LT-1 and LT-2 (1/8) and NT (1/2). The linezolid MIC/MBC for all strains was 2/≥64 mg/L. A two-compartment dynamic computerized device was used (inocula 10(7) cfu/mL). Free concentrations obtained in serum and interstitial fluid with twice-daily regimens of 1 g of vancomycin or 600 mg of linezolid were simulated over 48 h. ABBCs (differences between control growth curves and killing curves of bacteria exposed to antibiotics; log10 cfu × h/mL) and log10 reductions in initial inocula were calculated. Results: In serum simulations, vancomycin (AUC0-24/MIC = 251.8 for TOL-1 and 503.6 for the remaining strains) was bacteriostatic against strains with MBC/MIC ≥8, but bactericidal against NT. In interstitial fluid simulations (AUC0-24/MIC = 54.6 for TOL-1 and 109.2 for the remaining strains), initial inocula grew in all cases. Linezolid, both in serum (AUC0-24/MIC = 87.0) and in interstitial fluid (AUC0-24/MIC = 130.6) simulations, reduced initial inocula ≥2.2 log10 for all strains (apart from LT-1 in serum simulations that showed a bacteriostatic profile). ABBCs were similar in serum and interstitial fluid with linezolid, but significantly lower in interstitial fluid simulations with vancomycin. Conclusions: From the pharmacodynamic perspective (serum concentrations), vancomycin tolerance should include MBC/MIC ≥8 since strains exhibiting this ratio showed bacteriostatic profiles similar to those obtained with isolates with MBC/MIC ratios of 16 or 32. Insufficient concentrations of vancomycin at the simulated infected site were linked to bacteriological failure. Free concentrations of linezolid at the infection site pharmacodynamically covered MRSA.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 Survival of human pathogenic bacteria in different types of natural mineral water(Journal of Water and Health, 2012) Serrano, Concepción; Romero Martín, Margarita; Alou Cervera, Luis; Sevillano Fernández, David; Corvillo Martín, Iluminada; Armijo Castro, Francisco; Maraver Eyzaguirre, Francisco De PaulaThe aim of this study was to determine the survival of human pathogens (Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa) in five natural mineral waters (NMWs) with different properties and mineralization levels. Five NMWs from four Spanish spas with different dry residue at 110 °C were used: A = 76,935 mg/L; B = 1,827 mg/L; C = 808.4 mg/L; D = 283.8 mg/L; and E = 170.4 mg/L. An initial inoculum of 1 × 106 colony forming units (cfu)/mL was used for survival studies. Distilled water, chlorinated tap water and Mueller–Hinton broth were used as controls. Colony counts in all different waters were lower than those achieved with Mueller–Hinton broth over all incubation periods. A direct effect between the bacterial survival and the level of mineralization water was observed. The NMW E with low mineralization level along with the radioactive properties showed the highest antibacterial activity among all NMWs.Item Efficacy of intraoperative antiseptic scrub after nail removal surgery(Journal of the European Academy of Dermatology and Venereology, 2012) Becerro De Bengoa Vallejo, Ricardo; Losa Iglesias, Marta; Alou Cervera, Luis; Sevillano Fernández, David; Prieto Prieto, José