Biomedical subjects

M Viñas

Publications and source records attributed to M Viñas.

At least 37 records · Page 2Linked to original sources

PubMed1997

The acrAB homolog of Haemophilus influenzae codes for a functional multidrug efflux pump.

Disruption of gene HI0894 or HI0895 in Haemophilus influenzae Rd, homologs of Escherichia coli acrAB multidrug efflux genes, caused hypersusceptibility to erythromycin, rifampin, novobiocin, and dyes such as ethidium bromide and crystal violet and increased accumulation of radioactive erythromycin, showing that these genes are expressed and contribute to the baseline level resistance of this organism through active drug efflux. The gene disruption did not produce detectable changes in susceptibility to several other antibiotics, possibly because rapid influx of small antibiotic molecules through the large H. influenzae porin channels counterbalances their efflux.

Anti-Bacterial Agents↗

PubMed1997

New fimbrial adhesins of Serratia marcescens isolated from urinary tract infections: description and properties.

Fimbriation, hemagglutination and adherence properties were studied in two strains of S. marcescens (ATCC 43820 and 43821) isolated from the urine of two hospitalized patients in two different hospitals. Studies were performed using electron microscopy (EM), fimbrial purification, recombinant DNA and hemagglutination techniques, hydrophobicity and tests of adherence to uroepithelial cells, catheters and glass. In EM, fimbriae of these two strains showed an inner channel and were 11 nm. thick and 0.76-1.08 microns long. Original strains and the clone GH42-pSF192 (recombinant DNA prepared using E. coli GH42 as recipient and the cosmid SuperCos 1 as a vector) versus negative control (E. coli GH42-SuperCos 1) showed mannose-resistant hemagglutination of tanned erythrocytes and yeast, high hydrophobicity (55.4 and 49.6% at 37C versus 22.8%) and high adherence to borosilicate glass (313,000 and 168,000 CFU/cm.2 versus 17,000 CFU/cm.2), catheters (4.7 x 10(6) and 1.0 x 10(6) CFU/cm.2 versus 3.9 x 10(4) CFU/cm.2) and uroepithelial cells (adherence indexes of 3.82 and 3.29 versus 1.25). The properties of the fimbriae studied were different from those previously described in the genus Serratia, and they were designated as MR/T.

Adhesins, Bacterial↗

PubMed1997

Molecular basis of antimicrobial resistance in non-typable Haemophilus influenzae.

Strains of the facultative anaerobe Haemophilus influenzae, both type b and non typable strains, are frequently multiresistant. The measurement of the antibiotic permeability of Haemophilus influenzae outer membrane (OM) shows that antibiotics can cross through the OM easily. Thus, enzymatic activity or efflux pumps could be responsible for multiresistance. An efflux system closely related to AcrAB of Escherichia coli is present in Haemophilus influenzae. However, their role in multiresistance seems irrelevant. Classical mechanisms such as plasmid exchange seems to be playing a major role in the multidrug resistance in Haemophilus influenzae.

Anti-Bacterial Agents↗

PubMed1997

The role of outer membrane in Serratia marcescens intrinsic resistance to antibiotics.

Three different porins from Serratia marcescens were described. They were named Omp1, Omp2 and Omp3 and their molecular weights were 42, 40 and 39 kDa respectively. Omp2 and Omp3 showed osmoregulation and thermoregulation in a similar way to OmpC and OmpF of Escherichia coli. Permeability coefficients of the outer membrane of this species were calculated following the Zimmermann and Rosselet method. P values were similar to those obtained in Escherichia coli, which suggests that the chromosomal beta-lactamase would play a major role in the resistance of Serratia marcescens to beta-lactam antibiotics. Both MIC values and permeabilities were modified by salycilates and acetylsalycilate. Synergism between the outer membrane and the beta-lactamase was also evaluated. When bacteria grew in the presence of a beta-lactam in the medium, the beta-lactamase accounted for most of the resistance.

Bacterial Outer Membrane Proteins↗

PubMed1997

[Functionality of von Willebrand factor present in Fanhdi: adhesion to the vascular subendothelium in vitro].

PURPOSE: To study the ability of VWF present in a plasma derived high purity factor VIII concentrate (> or = 100 UI FVIII/mg of protein, Fanhdi) to promote deposition and platelet adhesion on the injured vessel wall, as an indicator of the functionality of said VWF. MATERIAL AND METHODS: An in vitro perfusion system was employed. Adequate proportions of platelets and red cells were suspended in a human albumin solution. Aliquots of the studied product were added to obtain levels of 0.4 and 0.8 VWF:AG U/mL in the perfusates. As a comparative group, cryoprecipitate was assayed at similar VWF:Ag doses. Perfusions were performed on rabbit de-endothelialized abdominal aorta segments, placed in annular perfusion chambers, at 37 degrees C and at a flux of 140 mL/min (800 s-1) for 10 min. Results were evaluated as surface covered by platelets and as the percentage ratio between thrombus and surface covered by platelets. FVIII activity was determined by one stage clotting assay. VWF:RCo activity was determined by aggregometry and VWF:Ag by ELISA. RESULTS: The VWF:Ag/FVIII:C ratio of Fanhdi is 1.57, while VWF:Roc/FVIII:C ratio is 1.15. The values of platelet deposition obtained, expressed as times of increase in the surface covered by platelets, considering the basal value (without VWF added) as 1, were: Cryoprecipitate 0.4 = 1.93; Cryoprecipitate 0.8 = 2.21; Fanhdi 0.4 = 2.99; Fanhdi 0.8 = 3.40. The ratios between thrombus and surface covered are 13.23%, 23.84%, 42.23%, 21.93% and 26.25% respectively. CONCLUSIONS: These data show that VWF present in Fanhdi maintains a high degree of functionality, promoting platelet adhesion on subendothelium under flow conditions, after its incorporation into an albumin-platelet-red cell preparation and resulting in a significant increase in platelet adhesion when compared to the VWF-free basal control.

Animals↗

PubMed1996

Existence of a platelet-adhesion defect in patients with cirrhosis independent of hematocrit: studies under flow conditions.

A defect in hemostasis has been repeatedly reported in patients with cirrhosis. However, the nature of this defect has not been fully characterized. We explored adhesive and cohesive functions of platelets from cirrhotic patients at different stages of disease development. The response of platelets to standard activating agents was tested by aggregometric procedures. The interaction of platelets with subendothelial components was explored in a perfusion system in which blood was exposed (shear rate, 800/s; 10 minutes) to denuded segments of rabbit aorta. Platelet interactions in these perfusions were analyzed morphometrically. Results were always compared with those obtained in similar studies using blood obtained from healthy subjects. Aggregation studies showed abnormal responses for single or several agonists. Abnormalities in aggregation were more evident in patients with severe disease (Child-Pugh class C), although they occasionally were abnormal for single agonists (ADP or U46619) in patients with less severe disease (Child-Pugh classes A or B). All the patient classes showed impaired platelet-subendothelial interactions (P < .01 vs. healthy subjects) that were not justified by the relative thrombocytopenia present in the more severely affected patients. Experimental increases in hematocrit in patients at stages B and C did not improve platelet-subendothelial interactions. Platelets from cirrhotic patients interact defectively with subendothelial components under flow conditions. The adhesion defect is more evident and consistent than the aggregation defects and may already be present in patients with mild liver failure. This adhesion defect may contribute to the defective hemostasis observed in cirrhotic patients.

Adult↗

PubMed1996

Outer membrane permeability of non-typable Haemophilus influenzae.

The permeability to cephaloridine was studied in five Haemophilus influenzae strains (four non-typable and one type b) using the Zimmermann and Rosselet method. The beta-lactamase activity was due to a plasmid-encoded TEM-1 enzyme. High permeability coefficients were measured in all strains examined. No great differences in permeability coefficients were found, even between strains with marked differences in OMP electrophoretic profiles.

Bacterial Typing Techniques↗

PubMed1996

Clonality of multidrug-resistant nontypeable strains of Haemophilus influenzae.

The genetic structure of a population of multidrug-resistant nontypeable (unencapsulated) Haemophilus influenzae strains isolated at a hospital in Barcelona, Spain, was investigated by using multilocus enzyme electrophoresis to determine the allelic variation in 15 structural loci. In our study we have also included some antimicrobial agent-susceptible strains isolated at the same hospital. All enzymes were polymorphic for two to eight electromorphs, and the analysis revealed 43 distinct electrophoretic types among the 44 isolates. The mean genetic diversity of the entire population was 0.55. Multilocus linkage disequilibrium analysis of the isolates revealed a strong association between alleles, suggesting little possibility of recombination. Furthermore, the dendrogram and the allele mismatch distribution are typical of a population with no extensive genetic mixing.

Alleles↗

PubMed1996

The effect of O-antigen on transformation efficiency in Serratia marcescens.

Serratia marcescens is an enterobacterium that exhibits very low efficiency of transformation. According to previous work, neither the bacterium restriction system nor its nuclease production accounts for this low efficiency. Differences in the efficiency of transformation from plasmid DNA were found in wild type of S. marcescens and their O-deficient spontaneous mutant strains. This phenomenon seems to be independent of plasmid size. When electroporation was used, the survival of O-mutants was much lower than those of their parental strains, but the frequencies of transformation among survivors were much higher. This suggests that the presence of the O-antigen is responsible for the low transformation frequencies observed.

Cell Membrane↗

PubMed1995

Taxonomy and protein fingerprinting of halophilic Vibrio isolates from bivalves of the Ebre delta.

A total of 380 isolates of halophilic Vibrio and related bacteria isolated from shellfish bred in the Ebro delta (in northeastern Spain) were studied by biochemical characterization; this allowed the use of numerical taxonomy programs. All but 25 isolates fell into 12 phenotypes. The analysis of whole-cell electrophoretic fingerprints of 100 isolates confirmed the numerical analysis of biochemical and morphological traits.

Animals↗

PubMed1995

Serratia marcescens adherence: the effect of O-antigen presence.

The presence of O-antigen affects the adhesion of Serratia marcescens cells to inert and biological surfaces. Mutants defective in the O-side chain showed significant decreases in their ability to adhere to plastic and glass surfaces and to the surfaces of Foley urinary catheters, compared with their respective parental strains. Similar results were obtained when the ability to adhere human uroepithelial cells was tested.

Bacterial Adhesion↗

PubMed1995

Lipopolysaccharide recovery restores susceptibility levels towards beta-lactams in Serratia marcescens.

O-side chain-defective spontaneous mutants of Serratia marcescens, selected by phage resistance, showed lower MICs against various beta-lactams than did their parental strains. The recovery of their ability to produce O-antigen restored the original MIC values, as well as phage susceptibility. The permeability coefficients of wild-type, O- mutants, and revertants, demonstrated that O-antigen modifies the permeability of antibiotics in S. marcescens.

Anti-Bacterial Agents↗

PubMed1995

Modification by analgesics of the susceptibility to antibiotics in Serratia marcescens.

The influence of analgesics at low concentrations on permeability and beta-lactamase expression have been studied "in vitro". The effect of these drugs on major outer membrane proteins and the lipopolysaccharide was evaluated. Acetylsalicylate and paracetamol induced modifications in susceptibility to a large variety of antibiotics when tested at therapeutic concentrations. The results suggested that when analgesics and antibiotics are administered simultaneously, the interaction between both kinds of drugs can alter the response of microorganisms to antibiotics.

Acetaminophen↗

PubMed1993

Outer membrane proteins from Serratia marcescens.

The outer membrane proteins (OMPs) of several strains of Serratia marcescens have been studied by sodium dodecyl sulphate - urea - polyacrylamide gel electrophoresis. Four major OMPs, named Omp1, Omp2, Omp3, and OmpA (42, 40, 39, and 37 kDa, respectively), have been visualized. The relative proportions of Omp2 and Omp3 depend on cultural conditions (temperature of incubation, osmolarity, and nutrient availability).

Bacterial Outer Membrane Proteins↗

PubMed1993

The role of O-antigen in susceptibility of Serratia marcescens to non-immune serum.

Selection of phage-resistant strains to three different phages, kappa, FSB3 and FSB55, whose primary receptor was lipopolysaccharide, enabled several spontaneous O-defective mutants to be isolated and characterized. Strains ATCC 274 (0:14), 2170 (0:14) and NIMA (0:6) showed serum resistance, whereas their O-side chain defective mutants exhibited high serum susceptibility. Both alternate and classical activation pathways were involved in serum killing activity in Serratia marcescens.

Animals↗

PubMed1992

Epidemiology and molecular basis of penicillin-resistant Neisseria meningitidis in Spain: a 5-year history (1985-1989).

Penicillin-resistant (penr) clinical isolates of Neisseria meningitidis, which do not produce beta-lactamase, were first identified in Spain in 1985; the frequency of their recovery, which has been increasing in the past few years, reached 20% in 1989. Serogrouping, determination of serotypes and subtypes, and multilocus enzyme electrophoresis of the penr strains showed an extensive diversity. Resistance is due, at least in part, to a decreased affinity of penicillin-binding protein (PBP) 2 for penicillin. Similar low-affinity forms of PBP 2 are also found in penr isolates of Neisseria lactamica, Neisseria polysaccharea, and Neisseria gonorrhoeae. Genetic transformation of an N. meningitidis type strain to low-level penicillin resistance with DNA from resistant meningococci and other Neisseria species resulted in transformants that possessed low-affinity forms of PBP 2. These altered forms of PBP 2 have been shown to arise from recombinational events that replace parts of the PBP 2 gene with the corresponding regions from the PBP 2 genes of commensal Neisseria species.

Bacterial Proteins↗

PubMed1992

Genetic diversity of penicillin-resistant Neisseria meningitidis.

The genetic relatedness of 42 penicillin-resistant Neisseria meningitidis isolates obtained during a 2-year period from a single hospital was studied by multilocus enzyme electrophoresis and by restriction fragment length polymorphism (RFLP) analysis of penicillin-binding protein (PBP) 2 genes. The PBP 2 genes of 7 susceptible strains gave identical RFLP profiles. Sixteen different PBP 2 RFLP profiles were found among the 42 resistant strains, but 4 were found in greater than 1 resistant isolate. Multilocus enzyme electrophoresis revealed a high level of genetic diversity. Four clusters of resistant strains could be distinguished at a genetic distance of 0.75. Resistant strains with the most common PBP 2 RFLP profile were restricted to one of these clusters and may be derived from a common ancestral strain. However, resistant strains with the 3 other common RFLP profiles were distributed in two or more of the clusters.

Adolescent↗

PubMed1991

Lipopolysaccharide is the receptor for kappa phage in Serratia marcescens.

Kappa phage active on Serratia marcescens can form plaques on white and red strains with identical efficiencies. To identify the kappa phage receptor, the inactivation of the phage was studied after incubation with several bacterial subcellular fractions. The experiments demonstrated that kappa phage adsorbs to outer membrane fractions of susceptible cells. Proteinase K did not affect the rate of inactivation. Lipopolysaccharide proved to be the primary receptor for kappa phage. Prodigiosin content of the lipopolysaccharide fraction was low.

Adsorption↗