[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: Introduction. This study explores effects of pH and inoculum size on imipenem versus tigecycline activity against E. coli, B. fragilis and E. faecalis, both in individual and mixed cultures. Methods. MIC/MBCs (mg/L) of tigecycline and imipenem were 0.12/≥16 and 4/4 for E. coli, 0.12/0.5 and ≥16/≥16 for B. fragilis, and 0.12/≥16 and 2/≥16 for E. faecalis, respectively. Killing curves in supplemented Brucella broth were performed at pH 7 or 5.8, with two final inocula (≈105 or ≈107 cfu/ml) of each isolate (individual cultures) and with 1:1:1 mixed inocula. Tubes were 48h incubated at 37ºC in anaerobiosis. Final concentrations (estimated concentrations in colon) were 1.50 mg/L for tigecycline and 26.40 mg/L for imipenem, with antibiotic-free curves as controls. Experiments were performed in triplicate. Results. Imipenem showed inoculum effect against E.coli and B. fragilis, with reductions in initial inocula in experiments with standard inocula contrasting with increases in experiments with high inocula (both individual and mixed cultures). Against E. faecalis no inoculum effect for imipenem was observed in individual cultures, with marked reductions in initial inocula regardless inoculum size. However in mixed experiments the indirect protection of E. faecalis by the two gramnegatives resulted in bacterial regrowth. This protection was inoculum-dependant since it occurred with high but not with standard inocula. Tigecycline reduced initial inocula of the three isolates regardless culture type (individual/mixed) or experimental conditions (pH/inocula size), with lower reductions for the tolerant E. faecalis. Conclusion. Carbapenemase activity was inoculum-dependant for self-protection and indirect protection of E. faecalis.
Revista espanola de quimioterapia: publicacion oficial de la Sociedad Espanola de Quimioterapia 09/2013; 26(3):220-225. · 0.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The aim of the study was to investigate biofilm formation in Gram negative bacteria and to quantify biofilm production applying a new developed technique that made possible to compare results about biofilm formation within the different Gram negative bacteria species. A total of 153 Gram negative strains corresponding to 12 different bacterium species were studied applying a variation of the optic density measurement technique reported by Stepanovic et al. Data obtained with optic density analysis allow to classify microorganisms in strong biofilm developers, moderate biofilm developers, weak biofilm developers and no biofilm developers. The results were expressed in two ways, using in both cases the same statistical method: without standardization, where controls were different depending on the day optic density measurements were performed, and standardized using a correction factor, using the same control for every strain of all our bacterium species in our study, which allows result homogenization. The obtained results in our study after data analysis and standardization show that over the 153 Gram negative strains in our study, 105 of them were no biofilm developers, representing 63.75% of all the studied bacterium genera. We consider that standardization and quantification of biofilm development in Gram negative bacteria can be useful in clinical practice, because biofilm development ability can lead or focus the gold treatment of pathologies produced by these microorganisms.
Revista espanola de quimioterapia: publicacion oficial de la Sociedad Espanola de Quimioterapia 06/2013; 26(2):97-102. · 0.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: OBJECTIVES: 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.
Journal of Antimicrobial Chemotherapy 05/2013; · 5.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Introduction. In cystic fibrosis, the Pseudomonas aeruginosa cells grow inside the thick mucus layer. In spite of being an obligate aerobe, P. aeruginosa is able to grow in a limited oxygen environment. Bacterial cells could be suddenly exposed to high oxygen levels due to the movements of the mucus mass. The aim of study was to determine the impact of a previous anaerobic incubation on the antimicrobial susceptibility of P. aeruginosa strains isolated from patients with cystic fibrosis. Materials and Methods. Four P. aeruginosa strains were used in this study (ATCC 23389 and 3 clinical isolates). The disk diffusion method was used to determine the antimicrobial susceptibility. Results. The anaerobic pre-incubation produced changes on the susceptibility in all studied strains. All susceptible strains after an aerobic incubation remained susceptible after an anaerobic incubation except one clinical strain, which became resistant to betalactams. The response was strain-dependent and the most significant increase in susceptibility was observed in two of the three clinical isolates when ciprofloxacin was used. Conclusions. The antimicrobial susceptibility of P. aeruginosa strains varies after their exposure to anaerobic conditions. Treatments promoting mucus fluidization could contribute to increase the antimicrobial efficacy.
Revista espanola de quimioterapia: publicacion oficial de la Sociedad Espanola de Quimioterapia 12/2012; 25(4):269-73. · 0.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: the aims of the study were to explore the activity of total and free (according to protein binding) maximal concentrations achieved in serum after multiple doses of voriconazole 400/200 mg and anidulafungin 200/100 mg against Aspergillus fumigatus and Aspergillus flavus and the human albumin or serum effects on antifungal activity.
Time-kill curves were performed with two A. fumigatus and two A. flavus strains at voriconazole and anidulafungin Cmax concentrations using different media: a) RPMI broth (Cmax-RPMI); b) RPMI with human serum (Cmax-HS), and c) RPMI with human albumin (Cmax-HAlb). In parallel, free-drug (fCmax) concentrations considering theoretical protein binding were performed in RPMI broth. Aspergillus metabolic activity was measured by the XTT reduction assay.
Voriconazol or voriconazole plus anidulafungin reduced >88.4% the metabolic activity of Aspergillus sp. at Cmax-RPMI and fCmax after 48 h of exposition. Anidulafungin alone showed poor metabolic reductions (<80.1% at Cmax- RPMI and <15% at fCmax). Anidulafungin activity, but not voriconazole activity alone or combined decreased in presence of HS or HAlb (more pronounced in A. flavus strains and HAlb). However, anidulafungin Cmax-HS or Cmax-HAlb against A. fumigatus strains were significantly more active (p<0.05) than fCmax in RPMI. These species and culture medium-dependent impact of human protein binding in the activity of anidulafungin was related to macroscopic and microscopic differences among mycelial mat grown in RPMI, HS or HAlb in whose XTT retention was different.
Synergism could not be demonstrated due to the high activity showed by voriconazole. Protein binding has not impact on voriconazole activity and this impact is considerably less than predicted by free concentration extrapolated from theoretical binding rate on anidulafungin. The XTT colorimetric assay needs to be standardized for use with Aspergillus spp. since without DMSO extraction the activity of echinocandins in a free-human protein RPMI medium could be overestimated.
Revista espanola de quimioterapia: publicacion oficial de la Sociedad Espanola de Quimioterapia 03/2012; 25(1):47-55. · 0.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper reports the effect of soda-lime-glass-nAg coating on the viability of an in vitro biofilm of Streptococcus oralis. Three strains (ATCC 35037 and two clinical isolates from periodontitis patients) were grown on coated with glass, glass containing silver nanoparticles, and uncoated titanium alloy disks. Two different methods were used to quantify biofilm formation abilities: crystal violet staining and determination of viable counts. The influence of the surface morphology on the cell attachment was studied. The surface morphology was characterized by scanning electron microscopy (SEM) and using a profilometer. SEM was also used to study the formation and the development of biofilm on the coated and uncoated disks. At least a >99.7% inocula reduction of biofilm respect to titanium disks and also to glass coated disks was observed in the glass-nAg coated disks for all the studied strains. A quantitative evaluation of the release of silver was conducted in vitro to test whether and to what extend the biocidal agent (silver) could leach from the coating. These findings suggest that the biofilm formation of S. oralis strains is highly inhibited by the glass-nAg and may be useful for materials which require durable antibacterial effect on their surfaces, as it is the case of dental implants.
PLoS ONE 01/2012; 7(8):e42393. · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Specific antibodies mediate humoral and cellular protection against invading pathogens such as Streptococcus pneumoniae by activating complement mediated immunity, promoting phagocytosis and stimulating bacterial clearance. The emergence of pneumococcal strains with high levels of antibiotic resistance is of great concern worldwide and a serious threat for public health.
Flow cytometry was used to determine whether complement-mediated immunity against three antibiotic-resistant S. pneumoniae clinical isolates is enhanced in the presence of sub-inhibitory concentrations of cefditoren and ceftriaxone. The binding of acute phase proteins such as C-reactive protein and serum amyloid P component, and of complement component C1q, to pneumococci was enhanced in the presence of serum plus either of these antibiotics. Both antibiotics therefore trigger the activation of the classical complement pathway against S. pneumoniae. C3b deposition was also increased in the presence of specific anti-pneumococcal antibodies and sub-inhibitory concentrations of cefditoren and ceftriaxone confirming that the presence of these antibiotics enhances complement-mediated immunity to S. pneumoniae.
Using cefditoren and ceftriaxone to promote the binding of acute phase proteins and C1q to pneumococci, and to increase C3b deposition, when anti-pneumococcal antibodies are present, might help reduce the impact of antibiotic resistance in S. pneumoniae infections.
PLoS ONE 01/2012; 7(9):e44135. · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This 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 (DNA(BLNAR)) and from β-lactamase-positive, amoxicillin-clavulanate-resistant (BLPACR) (DNA(BLPACR)) 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 DNA(BLPACR) and was decreased by ≈2 log₁₀ with DNA(BLNAR). 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 DNA(BLNAR) and DNA(BLPACR) simulations, with a small final recombined population (MIC, 4 μg/ml; ft>MIC, 30.7%) in DNA(BLPACR) simulations. When AMC was used against the BL⁺ strain (in DNA(BLNAR) or DNA(BLPACR) 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 DNA(BLNAR) and DNA(BLPACR) 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.
Antimicrobial Agents and Chemotherapy 04/2011; 55(6):2788-94. · 4.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In 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.
International journal of antimicrobial agents 03/2011; 37(4):332-8. · 3.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To evaluate cefditoren in inducer-substrate combinations to screen for AmpC induction.
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.
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).
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.
Revista espanola de quimioterapia: publicacion oficial de la Sociedad Espanola de Quimioterapia 06/2010; 23(2):72-5. · 0.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This 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.
International journal of antimicrobial agents 05/2010; 36(2):137-44. · 3.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
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.
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.
PLoS ONE 01/2010; 5(8):e12041. · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Odontogenic infections are polymicrobial. This study explores the in vitro killing activity by concentrations similar to those found in crevicular fluid of tinidazole in combination with amoxicillin/clavulanic acid, clindamycin and levofloxacin against four groups of high-density mixed inocula of anaerobes (Prevotella buccae, Fusobacterium nucleatum, and Veillonella spp.) and facultative (Capnocytophaga spp. and Streptococcus spp.) isolates of periodontal pathogens.
Killing curves were assessed under strict anaerobic conditions with antibiotics alone and in combination with tinidazole at concentrations similar to those achieved in crevicular fluid against approximately 10(7) colony forming units (CFU)/ml inoculum (1:1:1:1:1 proportion of the five bacterial isolates) of the four bacterial groups. Group 1 did not include beta-lactamase-producing strains; groups 2, 3, and 4 included one, two, and three beta-lactamase-producing strains, respectively.
In single-drug experiments, at 48 hours, tinidazole alone did not show significant killing of the entire bacterial population, whereas reductions in the initial inocula > or =2.09 log(10) CFU/ml with clindamycin, > or =3.26 log(10) CFU/ml with amoxicillin/clavulanic acid, and > or =3.83 log(10) CFU/ml with levofloxacin were obtained. When combined with tinidazole, reductions were significantly higher for all antibiotics: > or =5.28 log(10) CFU/ml with clindamycin, > or =4.78 log(10) CFU/ml with amoxicillin/clavulanic acid, and > or =6.17 log(10) CFU/ml with levofloxacin.
In addition to its high activity against anaerobic periodontal pathogens, tinidazole offered synergism with other antibiotics against the large strict anaerobic subpopulation and the small facultative subpopulation of a high-density mixed inocula of odontogenic pathogens under strict anaerobic conditions, similar to those of odontogenic infections.
Journal of Periodontology 01/2010; 81(1):131-8. · 2.40 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study explored the influence of vancomycin tolerance and protein binding on the bactericidal activity of vancomycin versus daptomycin (protein binding 36.9% vs. 91.7%, respectively) against four vancomycin-tolerant methicillin-resistant Staphylococcus aureus (MRSA) [minimum inhibitory concentration/minimum bactericidal concentration (MIC/MBC)=0.5/16, 1/32, 2/32 and 1/32microg/mL for vancomycin and 1/1, 1/2, 2/2 and 2/4microg/mL for daptomycin]. Killing curves were performed with vancomycin/daptomycin concentrations equal to serum peak concentrations (C(max)) (65.70/98.60microg/mL) and trough concentrations (C(min)) (7.90/9.13microg/mL) in the presence and absence of a physiological human albumin concentration (4g/dL), controlled with curves with the theoretical free drug fraction of vancomycin/daptomycin C(max) (41.45/8.18microg/mL) and C(min) (4.98/0.76microg/mL). Vancomycin C(max) and C(min) concentrations, regardless of the media, showed a bacteriostatic profile not reaching a reduction of 99% or 99.9% of the initial inocula during the 24-h experimental time period. Daptomycin antibacterial profiles significantly differed when testing C(max) and C(min). C(max) was rapidly bactericidal (< or =4h) with >5 log(10) reduction in the initial inocula for all strains, regardless of the presence or not of albumin or the use of concentrations similar to free C(max). C(min) exhibited similar final colony counts at 0h and 24h in curves with albumin, but with >3 log colony-forming units (CFU)/mL reduction at < or =4h for strains with an MIC of 1microg/mL and ca. 2 logCFU/mL reduction at < or =6h for strains with an MIC of 2microg/mL. This activity was significantly higher than the activity of the free C(min) fraction. The results of this study reinforce the idea that pharmacodynamics using concentrations calculated using reported protein binding are unreliable. Daptomycin exhibited rapid antibacterial activity against vancomycin-tolerant MRSA isolates even against those with high daptomycin MICs in the presence of physiological albumin concentrations.
International journal of antimicrobial agents 12/2009; 35(2):131-7. · 3.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To determine C(max) tigecycline activity in the presence/absence of physiological concentrations of human albumin with free fraction concentrations as controls.
Killing curves (final inoculum: 1.0-5.0 x 10(7) cfu/mL) were performed with 0.88 mg/L final concentrations (serum C(max) after a 100 mg 1 h infusion) in Mueller-Hinton broth supplemented with Ca(2+) and Mg(2+) (MH) and in MH with 4 g/dL human albumin. Controls were curves in MH with concentrations similar to the free fraction (fC(max) = 0.17 mg/L) calculated using protein binding. Activity was measured as log(10) initial inoculum reduction (log(10) initial inoculum-log(10) at 12 h/24 h). Target strains (tigecycline MIC/MBC; mg/L) were: methicillin-resistant Staphylococcus aureus heteroresistant to vancomycin (0.12/0.25); Enterococcus faecium (0.12/0.25); Escherichia coli producing extended-spectrum beta-lactamase (0.12/0.25); and Acinetobacter baumannii (0.25/1).
At 24 h the fC(max) produced mean decreases of < or =0.1 cfu/mL for all strains, in contrast to the bactericidal activity (mean >3 log(10) reduction) provided by C(max) concentrations in the presence or absence of albumin for E. coli and E. faecium, and an activity nearly bactericidal for S. aureus (mean approximately 2.8 log(10) reduction). In the case of the A. baumannii isolate the C(max) in the presence or absence of albumin produced a mean reduction of 2.56 log(10) cfu/mL at 12 h (time of one dosing interval), with a bacteriostatic profile when considering 24 h colony counts (similar counts at 0 and 24 h).
Correcting the total concentration for the reported literature binding values is unreliable since tigecycline antibacterial activity was greater than that suggested by the free fraction of the drug.
Journal of Antimicrobial Chemotherapy 12/2009; 64(6):1230-3. · 5.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The aim was to study the pharmacodynamics of cefditoren, amoxicillin/clavulanic acid and cefuroxime against mixed Haemophilus influenzae strains.
Isolates [MICs (mg/L) of cefditoren, cefuroxime and amoxicillin/clavulanic acid] used were: one beta-lactamase-negative (beta(-); 0.015, 1 and 1), one beta-lactamase-positive (beta(+); 0.03, 4 and 8) and two strains exhibiting ftsI gene mutations [one beta(-) ampicillin-resistant (BLNAR; 0.015, 8 and 4) and one beta(+) amoxicillin/clavulanic acid-resistant (BLPACR; 0.03, 8 and 4)]. A computerized pharmacodynamic model simulating free antibiotic concentrations (calculated considering reported percentages of protein binding) of 400 mg twice-daily cefditoren, 500 mg twice-daily cefuroxime and 875/125 mg three times daily amoxicillin/clavulanic acid was used to explore antibacterial activity against initial mixed inocula with 25% of each strain. Areas under bacterial curves (AUBCs) from 0 to 24 h (log cfu.h/mL) were calculated and differences between values in antibiotic-free (AUBC(K)) and in antibiotic simulations determined (ABBC(0-24) = AUBC(K0-24)-AUBC(0-24)).
In antibiotic-free medium, total population increased by 1.7 log(10) cfu/mL from 0 to 24 h: final composition approximately 90% beta(-), approximately 6.5% beta(+), approximately 2.5% BLNAR and approximately 1% BLPACR. At the end of antibiotic simulations, the predominant population was BLPACR followed by beta(+) after amoxicillin/clavulanic acid or BLNAR after cefuroxime exposures. ABBC(0-24) was higher (P < 0.01) for cefditoren compared with cefuroxime or amoxicillin/clavulanic acid whether considering total population (70.4 versus approximately 33), beta(+) (77.8 versus approximately 52), BLNAR (66.1 versus 18.6-30.4) or BLPACR (40.8 versus approximately 0).
Cefditoren offered higher antibacterial effect than cefuroxime and amoxicillin/clavulanic acid against a mixed population of H. influenzae strains due to its higher activity against beta-lactamase-producing strains and those carrying ftsI gene mutations.
Journal of Antimicrobial Chemotherapy 04/2009; 63(6):1215-22. · 5.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Among 165 Spanish Haemophilus influenzae isolates with mutations in the ftsI gene (ftsI(+)) (2005 to 2007), 73% were beta-lactamase negative and 26.7% were positive. The proportion of beta-lactamase-negative isolates to beta-lactamase-positive isolates was 2:1 to 4:1 in general, versus 1:3 in pediatric hospitals. Among 44 beta-lactamase-positive strains, 8 strains produced ROB-1 (5 from the pediatric hospital). beta-Lactamase-positive ftsI(+) strains were phylogenetically closer than were beta-lactamase-negative strains.
Antimicrobial Agents and Chemotherapy 11/2008; 53(1):267-70. · 4.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To phenotypically and genotypically characterize 11 strains (isolated in four different centres) exhibiting penicillin MIC of 8-32 mg/L among isolates of the SPICE project. Nine isolates were from Romania (9/162; 5.56%) and two from Poland (2/305; 0.66%).
In vitro susceptibility was determined in triplicate by microdilution (CLSI guidelines), and additionally, MICs of penicillin, cefotaxime and amoxicillin were confirmed in triplicate by agar dilution. Multilocus sequence typing (MLST), PFGE and gene amplification and sequencing were performed.
For the nine Romanian isolates, MICs were >/=16 mg/L for penicillin, cefotaxime and amoxicillin, >/=32 mg/L for cefuroxime and cefpodoxime, 4-8 mg/L for cefditoren and >/=128 mg/L for erythromycin and gentamicin. All isolates were non-susceptible to imipenem (MIC = 0.5-1 mg/L) and susceptible to levofloxacin (MIC = 0.5-1 mg/L) and vancomycin (MIC = 0.25-0.5 mg/L). These Romanian strains presented a new cluster in the 595-600 region of PBP2X (YSGIQL-->LSTPWF) conferring 98% homology with Streptococcus mitis PBP2X, with a new MurM allele (seven strains) with eight amino acid changes versus R6. PBP nucleotide sequences were highly conserved suggesting a common origin. Allelic profiles of two strains gave sequence type 321, three strains exhibited a single- and four a double-locus variance. MLST-predicted serotype was 23F in all but one strain (19F), but three strains were 19A by Quellung.
The multidrug high resistance (precluding adequate oral therapy in children), its origin, the prevalence found in Romania and the presence of non-vaccine (7-valent) serotypes should worry the medical community because of a possible clonal diffusion that would limit therapeutic alternatives.
Journal of Antimicrobial Chemotherapy 10/2008; 62(6):1234-40. · 5.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Activity of simulated cefditoren urinary concentrations was determined against seven Escherichia coli isolates. Bactericidal activity was obtained from 4 to 24 h against TEM-1 (penicillinase production/hyperproduction), TEM-34 (IRT-6), and TEM-116 (extended-spectrum beta-lactamase [ESBL]) and from 6 to 8 h against SHV/TEM-116 (ESBL) but never against SHV/TEM-1 (ESBL). Extension of bactericidal activity depended on the resistance genotype/phenotype tested.
Antimicrobial Agents and Chemotherapy 04/2008; 52(3):1184-6. · 4.57 Impact Factor