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Biomedical subjects

M Tirado

Publications and source records attributed to M Tirado.

At least 19 recordsLinked to original sources
PubMed2001

[Failure of rapid serology for Helicobacter pylori as diagnostic method in primary care consultation].

OBJECTIVE: To evaluate the validity of a rapid serology test for diagnosing Helicobacter pylori infection in our area. DESIGN: Longitudinal, prospective study. SETTING: Urban primary care centre. MEASUREMENTS: As reference tests for defining the presence/absence of Helicobacter pylori, histology and the urease gastric mucous membrane test (Jatrox(R) test) were used. Both tests can be either positive or negative, without intermediate values. RESULTS: 47 consecutive patients were included. Histology (confirmed with the urease test) showed infection in 38 cases (80.85% prevalence). The results of rapid serology (95% CI) were: sensitivity 0.66 (0.51-0.81), specificity 1 (1-1), positive predictive value 1 (1-1), and negative predictive value 0.41 (0.2-0-61). CONCLUSIONS: In a population with high prevalence of infection, a positive in the rapid serology test confirms infection. However, a negative does not discount infection, which significantly reduces the test's overall diagnostic value. This confirms in the primary care context the findings of hospital-based studies.

Adult↗
PubMed2001

Electric manipulation of bioparticles and macromolecules on microfabricated electrodes.

Bioparticle separation, bioparticle enrichment, and electric field-mediated immune detection were carried out on microfabricated semiconductor chips utilizing ac and dc electric fields. Microscale separation on a chip surface having an active area of approximately 16 mm2 was demonstrated for a mixture of Bacillus globigii spores and Escherichia coli bacteria. Dielectrophoretic enrichment was performed by collecting target bioparticles from a flow stream in flow cells of 47.5 microL, achieving a 20-fold increase in the concentration of E. coli bacteria from a diluted sample, a 28-fold enrichment for peripheral blood mononuclear cells from red blood cells, and a 30-fold increase in white blood cells from diluted whole blood. The ability to manipulate and collect bioparticles and macromolecules at microfabricated electrodes with ac and dc fields was further illustrated in electric field-mediated immunoassays for analyzing the biological identities of E. coli bacteria and B. globigii spores. According to these results, the electric methods for manipulating bioparticles present themselves as viable techniques for novel biomedical applications in sample preparations and biochemical assays on microelectrode arrays.

Bacillus↗
PubMed2000

[Cost-effectiveness analysis of 2 strategies of Helicobacter pylori eradication: results of a prospective and randomized study in primary care].

BACKGROUND: To analyze cost-effectiveness of two different strategies to treat H. pylori infection in peptic ulcer in the primary care setting. PATIENTS AND METHODS: Consecutive patients with endoscopic diagnosis of peptic ulcer were randomized to one of two strategies: a) treatment during 7 days with omeprazole, tetracycline, metronidazole and bismuth subcitrate ("quadruple" therapy) and if failure second-line treatment with omeprazole, amoxycillin and clarithromycin during 7 days (OCA7), and b) initial treatment with OCA7 and if failure treatment with "quadruple therapy". End point was eradication 8 weeks after last treatment dose. Direct and indirect costs were estimated (euros, 1997) and a cost-effectiveness analysis using a decision-tree model was undertaken after real clinical data. 95% confidence intervals are given. RESULTS: After screening 255 patients, 97 were finally included. 48 patients were given strategy a and 49 strategy b. Eradication was obtained (intention-to-treat) in 72.9% (CI 95%: 58.2-84.7) in group a versus 91.8% (CI 95%: 80.4-97.7) (p < 0.05) in group b. Mean cost per case treated was lower in group a (237 versus 268 euros) but cost per case eradicated was lower in group b (320 versus 296 euros). The cost was primarily determined by efficacy. CONCLUSIONS: Treatment with OCA7 followed by rescue with "quadruple" therapy if failure is more efficient in our area that the inverse strategy. Efficiency is mostly determined by efficacy.

Adolescent↗
PubMed1998

Broad Frequency Range Study of the Dielectric Properties of Suspensions of Colloidal Polystyrene Particles in Aqueous Electrolyte Solutions.

The dielectric properties of suspensions of spherical polystyrene particles with radii of 34 and 50 nm, in aqueous electrolyte solutions were measured in the frequency range of 10 kHz to 30 GHz using HP 4192A impedance and 8753A network analyzers, and double path interferometers. The samples were prepared from the stock suspensions with a high particle concentration (volume fraction of 0.4), which were used either unchanged or diluted with increasing amounts of water down to a concentration of 0.05. The permittivity and total loss spectra showed three well-defined relaxation regions, which could successfully be interpreted using an existing model [Grosse, C., J. Phys. Chem. 92, 3905 (1988)] (corrected by including a term of counterion diffusion on the particle surface). A model spectral function was fitted to the data using seven free parameters: the static conductivity of the electrolyte solution, three parameters associated with the relaxation of the electrolyte solution, and just three parameters for the description of both the counterion and the Maxwell-Wagner relaxations. For different particle concentrations, the values of the surface conductivity (obtained from the Maxwell-Wagner parameters) remained essentially constant, while the low-frequency relaxation parameters exhibited very good agreement with theoretical predictions in Delgado, A. V., Arroyo, F. J., Gonzales-Caballero, F., Shilov, V. N., and Borkovskaya, Yu. B., Colloids Surf. A, in press. Copyright 1998 Academic Press.

Journal Article↗
PubMed1994

[Loss of antibiotic sensitivity of Pseudomonas aeruginosa strains during treatment].

BACKGROUND: Loss of sensitivity to betalactamic, quinolones and aminoglucoside antibiotics has been described during treatment of infections produced by strains of Pseudomonas aeruginosa. Sixteen nosocomial strains isolated over a year during which sensitivity to one or several antibiotics of the above mentioned groups had been lost during the course of treatment were studied. METHODS: The strains were identified by conventional techniques. Sensitivity to antibiotics was studied by determination of the minimum inhibitory concentration in solid medium, according to the guidelines of the National Committee for Clinical Laboratory Standards. Plasmidic beta-lactamases were identified by analytic isoelectric focusing. Hyperproduction of chromosomic lactamase was studied by a qualitative technique. The 0 antigens were studied against rabbit antisera. The pyocinetype was determined according to the Fyfe method. Plasmids were detected by alkaline lysis extraction and electrophoresis in agarose gel. RESULTS: The 16 strains in which changes in sensitivity were observed during the course of treatment represent 4.47% of all P. aeruginosa isolates during one year. Loss of sensitivity to betalactamic antibiotics was observed in 10 strains, in one to aminoglucosides, in two to ciprofloxacin, simultaneously to aminoglucosides and ciprofloxacin in one and to betalactamic and ciprofloxacin in another two. Six of the 13 patients (46%) required a change in antibiotic treatment. CONCLUSIONS: The convenience of following the sensitivity of the strains of Pseudomonas aeruginosa isolated in a patients is suggested to thereby avoid therapeutic failure and the potential danger of clonal dissemination of the strains which have lost sensitivity.

Adult↗
PubMed1993

Characterization of penicillinase-producing strains of Neisseria gonorrhoeae.

Twenty-three penicillinase-producing strains of Neisseria gonorrhoeae were characterized. All strains showed hybridization with a TEM-1 probe and production of a TEM-1 type beta-lactamase (pI 5.4) on isoelectric focusing. Eight strains also showed a beta-lactamase band of pI 5.5. The penicillin MICs for the strains producing only TEM-1 were in the range 4-16 micrograms/ml; MICs of the strains with the additional pI 5.5 band were > or = 128 micrograms/ml for seven strains and 4 micrograms/ml for an arginine-hypoxanthine dependent strain. The association of the high MICs with the presence of the pI 5.5 band was statistically significant. The pI 5.5 band could represent a new beta-lactamase type or a TEM-1 mutant.

Isoelectric Point↗
PubMed1989

[Efficiency of tazobactam as inhibitor of beta-lactamases, combined with piperacillin, against resistant strains to this penicillin].

We studied the efficacy of tazobactam (YTR 830), a new beta-lactamase inhibitor in combination with piperacillin (P) against 198 Enterobacteriaceae strains. A comparative study of susceptibility (MIC determined on Mueller Hinton agar; inoculum 10(4) cfu) was made with the combination amoxicillin (A) + clavulanic acid (CA). Of 181 strains resistant to P, 79.56% were susceptible to it in the presence of tazobactam (TZ). The characteristics of the beta-lactamases of 37 strains resistant to P + TZ (MIC greater than 40 micrograms/ml) were studied; 11 were hyperproducers of chromosomic beta-lactamase and 7 produced two types of plasmidic beta-lactamase. The MICs of TZ alone were uniform and high (64-128 micrograms/ml), independently of the characteristics of the strains beta-lactamase. Of 17 strains susceptible to P, the efficacy of P + TZ was significant among carriers of plasmidic beta-lactamase; there was practically no change in the P susceptibility among the non carriers. The efficacy of P + TZ was similar to that of A + AC against E. coli strains; it was higher against strains of Enterobacter, Citrobacter and Serratia.

Amoxicillin↗
PubMed1989

[Resistance caused by hyperproduction of chromosomal beta-lactamase in Pseudomonas aeruginosa].

From 120 Pseudomonas aeruginosa strains selected for their slight susceptibility to ceftazidime (MIC greater than or equal to 16 micrograms/ml) we studied the characteristics of beta-lactamases and their susceptibility to aminoglycoside and to beta-lactam antibiotics. The quantitative spectrum, chromosomic beta-lactamase hyperproduction and the isoelectric point of beta-lactamases were also studied as well as the MIC in solid medium, inoculum 5 x 10(4) cfu. About 14.7% of strains moderately susceptible to ceftazidime and 88.4% of those resistant, were hyperproducers of chromosomic beta-lactamases. All the strains were resistant to ureidopenicillins, cefotaxime and moxalactam, 55.8% to monobactams and 35% were also resistant to cefsulodine; all of them were susceptible to imipenem. In bacteria isolated from twelve patients a loss of susceptibility could be observed against ceftazidime and other beta-lactams. There was also an increase in chromosomic beta-lactamase production during the treatment with antibiotics.

Aminoglycosides↗
PubMed1989

[Type TEM beta-lactamase activity in a Neisseria meningitidis strain].

We studied the beta-lactamase activity characteristics of a penicillin G resistant N. meningitidis strain (MIC = 8 micrograms/ml) isolated from a septicemic process, in an eleven month old girl, attended in the Sabadell Hospital (Barcelona). The beta-lactamase substrate profile was broad-spectrum (it hydrolyses penicillin G and cephaloridine) and the nitrocefin hydrolysis was inhibited by clavulanic acid. The analytical isoelectric focusing of the enzyme showed that the isoelectric point of the main band and, the secondary bands, were compatible with those of the type TEM-1 standard enzyme. We also obtained a positive DNA-DNA hybridization with the TEM-1 beta-lactamase (pBR322 plasmid).

Humans↗
PubMed1986

Incidence of strains producing plasmid determined beta-lactamases among carbenicillin resistant Pseudomonas aeruginosa.

A total of 1056 strains of Pseudomonas aeruginosa isolated from human clinical specimens from patients was collected from eight laboratories in order to study the frequency of plasmid-determined beta-lactamase producers and the different enzymes represented. The strains from each laboratory comprised consecutive, non-repeated, clinical isolates. In the 166 strains selected because they were carbenicillin resistant, the isoelectric points of the beta-lactamases were studied by means of analytical isoelectric focusing and the different types of plasmid-determined beta-lactamases identified. Seventy-five of the strains (45.18%) were plasmid-mediated beta-lactamase producers; the frequency varied among laboratories from 0% to 100%. Overall the most frequently identified beta-lactamase type was PSE-1 (49.34%) followed by TEM-1 (37.34%). The remaining carbenicillin-resistant strains did not produce plasmid-determined beta-lactamases.

Carbenicillin↗