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M Blanco

Publications and source records attributed to M Blanco.

At least 145 records · Page 8Linked to original sources
PubMed1996

Prevalence and characteristics of Escherichia coli serotype O157:H7 and other verotoxin-producing E. coli in healthy cattle.

From February to July of 1994, 328 faecal samples from 32 herds were collected and verotoxin-producing Escherichia coli (VTEC) found on 84% of the farms. The proportion of animals infected varied from 0-63%. VTEC were recovered from 52 (20%) of 257 cows and from 16 (23%) of 71 calves. Although the VTEC belonged to 25 different serogroups, 7 (O8, O20, O22, O77, O113, O126 and O162) accounted for 46% of strains. Nearly 45% of the strains. Nearly 45% of the 83 bovine VTEC strains belonged to serogroups associated with haemorrhagic colitis and haemolytic uraemic syndrome in humans. However, only 2 (2%) of 83 VTEC strains isolated from cattle belonged to enterohaemorrhagic E. coli (EHEC) serotypes (O26:H11 and O157:H7), and only 8 (10%) were positive for the attaching and effacing E. coli (eae) gene sequence. Polymerase chain reaction (PCR) showed that 17 (20%) of VTEC strains carried VT1 genes, 43 (52%) possessed VT2 genes, and 23 (28%) carried both VT1 and VT2 genes. Characterization of VTEC isolates revelated a heterogeneous population in terms of serogroup and toxin type in the positive herds. This study confirms that healthy cattle are a reservoir of VTEC, but, the absence of eae genes in most bovine VTEC strains suggests that they may be less virulent for humans than eae-positive EHEC.

Animals↗
PubMed1996

The Hha protein as a modulator of expression of virulence factors in Escherichia coli.

We constructed hha derivatives from both a clinical uropathogenic Escherichia coli isolate (strain FVL4) and a wild E. coli strain causing bovine diarrhea (strain CCB21) and analyzed the effect of the hha allele on the expression of the different virulence factors exhibited by these strains. Expression of hemolysin and of the Vir antigen was altered in hha mutants. Whereas production of hemolysin by strain FVL4 was repressed both at a low temperature and at high osmolarity, the hha allele accounted for a significant increase of hemolysin production under these conditions. Also, the low temperature-sensitive expression of the Vir adhesin was modified in hha mutants, which were able to express this adhesin at a low temperature. Expression of other virulence factors, such as cytotoxic necrotizing factor type 1 and 2 toxins, remained unmodified in hha derivatives of strains FVL4 and CCB21.

Adhesins, Bacterial↗
PubMed1996

O serogroups, biotypes, and eae genes in Escherichia coli strains isolated from diarrheic and healthy rabbits.

A total of 305 Escherichia coli strains isolated from diarrheic and healthy rabbits in 10 industrial fattening farms from different areas of Spain were serotyped, biotyped, and tested for the presence of the eae gene and toxin production. The characteristics found in strains isolated from healthy rabbits were generally different from those observed in E. coli strains associated with disease. Thus, strains with the eae gene (74% versus 22%); strains belonging to serogroups O26, O49, O92, O103, and O128 (64% versus 12%); rhamnose-negative strains (51% versus 5%); and rhamnose-negative O103 strains with eae genes present (41% versus 1%) were significantly (P < 0.001 in all cases) more frequently detected in isolates from diarrheic animals than in those from healthy rabbits. Whereas a total of 35 serogroups and 17 biotypes were distinguished, the majority of the strains obtained from diarrheic rabbits belonged to only four serobiotypes, which in order of frequency were O103:B14 (72 strains), O103:B6 (16 strains), O26:B13 (12 strains), and O128:B30 (12 strains). These four serobiotypes accounted for 48% (112 of 231) and 5% (4 of 74) of the E. coli strains isolated from diarrheic and healthy rabbits, respectively. Only six strains were toxigenic (three CNF1+, two CNF2+, and one VT1+). We conclude that enteropathogenic E. coli strains that possess the eae gene are a common cause of diarrhea in Spanish rabbit farms and that the rhamnose-negative highly pathogenic strains of serotype O103:K-:H2 and biotype B14 are especially predominant. Detection of the eae gene is a useful method for the identification of enteropathogenic E. coli strains from rabbits. However, a combination of serogrouping and biotyping may be sufficient to accurately identify the highly pathogenic strains for rabbits.

Adhesins, Bacterial↗
PubMed1996

Amino acids critical for the functions of the bovine papillomavirus type 1 E2 transactivator.

The N-terminal domain of the bovine papillomavirus type 1 E2 protein is important for viral DNA replication, for transcriptional transactivation, and for interaction with the E1 protein. To determine which residues of this 200-amino-acid domain are important for these activities, single conservative amino acid substitutions have been generated in 17 residues that are invariant among all papillomavirus E2 proteins. The resulting mutated E2 proteins were tested for the ability to support viral DNA replication, activate transcription, and cooperatively bind to the origin of replication with the E1 protein. We identified five mutated proteins that were completely defective for transcriptional activation and either were defective or could support viral DNA replication at only low levels. However, several of these proteins could still interact efficiently with the E1 protein. In addition, we identified several mutated proteins that were unable to efficiently cooperatively bind to the origin with the E1 protein. Although a number of the mutated proteins demonstrated wild-type activity in all of the functions tested, only 3 out of 17 mutated viral genomes were able to induce foci in a C127 focus formation assay when the mutations were generated in the background of the entire bovine papillomavirus type 1 genome. This finding suggests that the E2 protein may have additional activities that are important for the viral life cycle.

Amino Acid Sequence↗
PubMed1996

Recurrent mutations in the vasopressin-neurophysin II gene cause autosomal dominant neurohypophyseal diabetes insipidus.

We examined the nucleotide sequence of the arginine vasopressin-neurophysin II gene in three kindreds with autosomal dominant neurohypophyseal diabetes insipidus. Each of the three different mutations identified represents a recurrence of a mutation previously described to cause this disease. These mutations are all transitions (C1761-->T, G1859-->A, and G279-->A) that encode amino acid substitutions Pro24-->Leu, Gly57-->Ser (both in neurophysin II), and Ala-->Thr (in the last amino acid at the C-terminus of the signal peptide). The presence of these mutations in genomic DNA was confirmed by alterations in restriction endonuclease recognition sites. A linkage map of distal chromosome 20 was constructed. To examine the possibility that these apparent recurrent mutations arose independently rather than by an ancestral founder mutation, we analyzed family origins, two polymorphic markers on chromosome 20 in close proximity with this gene (the oxytocin/XbaI restriction fragment length polymorphism and the D20S57 polymorphic CA repeat microsatellite), and/or the occurrence of a de novo mutation in our three families and in four additional families previously reported. Our results suggest that one of our families may share an ancestral founder mutation with one previously reported family, but that in the remainder of the families with identical mutations, these mutations probably arose independently.

Alleles↗
PubMed1996

The effect of intravenous metoclopramide on blood pressure in normotensive and hypertensive subjects.

In the present study we evaluated the effect of intravenous metoclopramide on blood pressure in normotensive (untrained, football players, runners) and hypertensive subjects. There was a decrease in blood pressure only observed in untrained female subjects and this was greater in hypertensive subjects. In football players and runners the decrease in blood pressure was not statistically significant. There was no significant effect on heart rate. The probable mechanism of this new pharmacological effect of metoclopramide is unknown, however, research is now in progress to define its mechanism of action.

Adult↗
PubMed1996

Detection of enterohaemorrhagic Escherichia coli O157:H7 in minced beef using immunomagnetic separation.

Enterohaemorrhagic Escherichia coli (EHEC) O157:H7 has been recently recognized as a human pathogen associated with haemorrhagic colitis and haemolytic uraemic syndrome. Most outbreaks of haemorrhagic colitis resulted from the consumption of undercooked minced beef or raw milk. Dairy cattle have been identified as a reservoir of EHEC O157: H7. In this study E. coli O157 specific antibody, coated on magnetic beads, was used to concentrate and release EHEC O157:H7 from meat samples. A survey of retail fresh minced beef and hamburger samples using this procedure revealed that 3 (5%) of 58 beef samples were positive for EHEC O157:H7. Two of the strains produced both VT1 and VT2 verotoxins, and one produced only VT2. Immunomagnetic separation is a sensitive and simple technique for the isolation of E. coli O157 from food, and could be useful for a further elucidation of the epidemiology of this organism. The relatively high prevalence of EHEC O157:H7 in beef samples may constitute a risk for public health. Thus, a suitable epidemiologic control and effective methods of prevention should be applied.

Animals↗
PubMed1995

Artificial neural networks for multicomponent kinetic determinations.

An artificial neural network (ANN) procedure that uses the scores of a principal component model as input data was tested for calibration in the resolution of binary mixtures from kinetic measurements. The results thus obtained are compared with those provided by partial least-squares (PLS) regression and principal component regression (PCR). The ANN was first applied to simulated single wavelength kinetic curves. The effect of experimental variability was considered by assuming rate constants to fit a normal distribution curve. An amount of instrumental noise was also added to the simulated curves. Both linear and nonlinear systems were tested. Non-linearity was assumed to result from interactions between analytes and modeled by introducing a multiplicative term in the rate equation. The results provided by the three methods on linear systems were comparable; in the presence of interactions between analytes, however, the ANN method clearly outperformed the other two. The ANN method was also used to resolve mixtures of Fe(III), Co(II), and Zn(II) by displacement from their EGTA complexes with 4-(2-pyridylazo)resorcinol (PAR) using a stopped-flow injection assembly including a diode array detector. Preliminary experiments revealed the Co(II) and Zn(II) displacement reactions to be pseudo-first-order and that of Fe(III) to be a multistep process that departed from the linear behavior of the other two. Again, the results obtained with ANN were better than those provided by PCR and PLS.

Calibration↗
PubMed1995

Growth factors and stromal support generate very efficient retroviral transduction of peripheral blood CD34+ cells from Gaucher patients.

We have achieved high-efficiency gene transfer into nonmobilized peripheral blood (PB) CD34+ cells from patients with Gaucher's disease using a clinically acceptable retroviral supernatant transduction protocol. In our studies, bone marrow (BM) and PB CD34+ cells were transduced using a high titer (10(8) particles/mL) retroviral supernatant once a day for 4 consecutive days in the presence of interleukin-3 (IL-3), IL-6, and stem cell factor (SCF), with or without an irradiated allogeneic BM stromal layer. The growth factors alone resulted in 29% +/- 10% gene transfer of PB CD34+ clonogenic cells in contrast with 71% +/- 17% gene transfer efficiency using stroma with the growth factors; a 2.5-fold increase. The increase in gene transfer efficiency was less prominent when BM CD34+ cells were used (40% +/- 16% without and 57% +/- 8% with stroma, a 1.5-fold increase). The overall transduction efficiency of both PB and BM CD34+ cells was lower when the cells were transduced over a stromal cell layer without added growth factors. The combination of IL-3, IL-6, and SCF with stroma transduced 75% of primitive long-term culture initiating cells (PB LTC-ICs) in comparison with 34% of LTC-ICs when IL-3, IL-6, and SCF were used without stromal support. Using this clinically acceptable supernatant/cytokines/stroma transduction protocol, correction of the glucocerebrosidase (GC) deficiency in the progeny cells of PBLTC-ICs from Gaucher's-disease patients has been accomplished. Efficient transduction of the PB CD34+ cells using this transduction protocol may allow repeated delivery of "GC-corrected" hematopoietic stem and progenitor cells to Gaucher's-disease patients.

Antigens, CD↗
PubMed1995

Detection of oxidative mutagens in strains of Escherichia coli deficient in the OxyR or MutY functions: dependence on SOS mutagenesis.

The Escherichia coli strain IC3821, a delta oxyR derivative of WP2 uvrA trpE65, was more sensitive to mutagenicity promoted by t-butyl hydroperoxide and cumene hydroperoxide than the isogenic oxyR+ control. Mutagenicity of menadione, a redox cycling quinone, was clearly detected in the delta oxyR strain, whereas only a slight mutagenic response was observed in the oxyR+ strain. Plumbagin, another quinone structurally similar to menadione, was not mutagenic to any of the strains. These mutagenic responses appeared to involve the SOS processing of oxidative DNA lesions and were mediated by MucA/B proteins more efficiently than by UmuD/C. In cells lacking mutagenesis proteins, induction of SOS-independent mutations by the two alkyl hydroperoxides required a deficiency in the MutY DNA glycosylase and was increased by the presence of the delta oxyR mutation. In contrast, the two quinones assayed were unable to induce SOS-independent mutations in the MutY-deficient strains.

Benzene Derivatives↗
PubMed1995

Increased mutability by oxidative stress in OxyR-deficient Escherichia coli and Salmonella typhimurium cells: clonal occurrence of the mutants during growth on nonselective media.

Escherichia coli and Salmonella typhimurium strains deficient in the OxyR-regulated adaptive response to oxidative stress were used to study the mode in which spontaneous SOS-dependent mutations are generated in a distressed bacterial population. When assayed on supplemented selective medium, the E. coli strain IC3821 (trpE65), carrying the delta oxyR30 mutation and containing the plasmid pRW144 (mucA/B), showed a frequency of spontaneous Trp+ revertants similar to that of the oxyR+ control. Instead, the IC3821 strain exhibited an enhancement in the clonal occurrence of spontaneous revertants arising at random during growth on a nonselective medium. A similar enhancement was observed for the S. typhimurium strain TA4125 (hisG428 delta oxyR2). The mutator effect observed in oxyR- cells would be induced by an increased background of reactive oxygen species; it provides a model for studying the mutability of a cell population constantly exposed to mutation-inducing agents. In the IC3821 strain, revertants were induced by t-butyl hydroperoxide with higher efficiency than in oxyR+. We suggest that strain IC3821 could be useful for the detection of SOS-dependent mutagenesis induced by chemical oxidants.

Adaptation, Biological↗
PubMed1995

Toxigenic Escherichia coli in Spanish piggeries from 1986 to 1991.

Four-hundred and fourteen faecal samples from pigs with diarrhoea, oedema disease or healthy pigs, were collected from 65 piggeries located in different areas of Spain from 1986 to 1991. A total of 1334 Escherichia coli cultures were isolated from the pigs and studied for production of heat-labile (LT) and heat-stable (STa) enterotoxins, verotoxin (VT) and for type 1 (CNF1) and type 2 (CNF2) cytotoxic necrotizing factors. Strains producing enterotoxins (P < 0.001) or verotoxin (P < 0.05) were associated with enteric diseases of pigs. In the majority (82.3%) of piglets with strains, producing verotoxin the strains were also positive for production of STa enterotoxin. The most frequent toxin detected was STa. Although we isolated strains producing CNF1 from 1.5% of sick pigs, they were not statistically associated (P < 0.7) with enteric disease. Pigs may constitute a natural reservoir of CNF1 producing E. coli strains in Spain; their presence in the porcine intestine may be of significance in public health because such strains have been associated with human extraintestinal infections.

Animals↗
PubMed1995

[Alveolar lipoproteinosis treated by bronchopulmonary lavage].

Alveolar lipoproteinosis is a rare disease, a review of the Spanish Medical Index for 1971 to June 1994 showing only 9 reported cases. The intra-alveolar deposit of lipoprotein-type matter produces severe hypoxemia and favors infection by opportunistic germs. Treatment with massive bronchial lavage (MBL) removes the matter from the alveolar space, improves gas exchange and decreases the risk of infection. We report a case of primary alveolar lipoproteinosis treated with MBL in which the patient developed infections by Aspergillus fumigatus before lavage and after starting steroid treatment. The procedure was performed without complications, with significant clinical and gasometric improvement. The natural evolution of this disease is poorly understood. Spontaneous remissions have been observed, and as MBL is not a risk-free procedures, its use in treatment is controversial. We believe that when severe hypoxemia is present, MBL should be used early, when the risk is slight; MBL improves gas exchange and probably reduces the risk of opportunistic infection.

Adult↗
PubMed1995

[Enterotoxigenic, verotoxigenic, and necrotoxigenic Escherichia coli in food and clinical samples. Role of animals as reservoirs of strains pathogenic for humans].

Toxigenic Escherichia coli of human and animal origin have been classified into three categories: enterotoxigenic E. coli (ETEC), verotoxigenic E. coli (VTEC), and necrotoxigenic E. coli (NTEC), ETEC are a major cause of infant diarrhoea in less-developed countries and frequently cause colibacillosis in domestic animals. Human ETEC strains may synthesize LT-I and/or STa enterotoxins and they may possess the colonization factors CFA/I to CFA/IV; porcine strains synthesize LT-I, STa and/or STb, and possess the colonization antigens K88, P987, K99 or F41; and bovine strains are usually STa producers harbouring on the bacterial surface K99 or F41 colonization factors. There is a high host-specificity, because of that ETEC from animals are not pathogen for humans. VTEC strains may produce three mainly types of verotoxins (VT1, VT2, VT2vp1) that are functionally and structurally related to the shiga toxin. The VTEC of human and bovine origins produce VT1, VT2 or both, whereas VT2vp1 is elaborated by E. coli that cause edema disease in swine. The VTEC strains belonging mainly to serotypes O157:H7 or H-, O26:H11 and O111:H-, are now considered to be the major cause of two human syndromes of hitherto unknown cause: hemorrhagic colitis and hemolytic uremic syndrome. Most outbreaks of VTEC infection occurred in USA, Canada and United Kingdom during the last ten years and have been linked to consumption of undercooked ground beef, and, to a lesser extent, to the drinking of unpasteurized milk. Thus, the principal reservoir of VTEC is the intestinal tract of cattle. By contrast, it is presumed that human beings are the major reservoir of ETEC, and that contaminated water is a principal vehicle for transmission of ETEC infections. NTEC strains are able to elaborate two types of cytotoxic necrotizing factors (CNF1 and CNF2). Strains of human origin usually produce CNF1, whereas bovine NTEC generally synthesize CNF2. NTEC strains are not responsible for food-associated outbreaks of gastroenteritis, but CNF1 and CNF2 are very good markers of the source of food contamination.

Animals↗
PubMed1995

[Virulence factors and 0 serogroups of Escherichia coli as a cause of community-acquired urinary infections].

BACKGROUND: The aim of this study was to determine the virulence factors and 0 serogroups of E. coli strains that cause community acquired urinary tract infections (UTI). METHODS: We examined 103 E. coli strains isolated from the urine of patients with UTI. The following virulence factors were investigated using phenotypic techniques: the alpha-haemolysin (Hly), the cytotoxic necrotizing factor type 1 (CNF-1) and the mannose-resistant haemagglutination (MRHA) types III, IVa and IVb expressed by P fimbriated E. coli. Serotyping of 0 antigen was carried out by means of a microtechnique using 163 antisera. RESULTS: Fifty-five (53%) of the 103 E. coli strains examined showed some of the virulence factors investigated in this study; 41% of the strains were Hly+, 28% were CNF-1+ and 48% expressed MRHA types III, IVa or IVb. The uropathogenic strains characterized belonged to 27 different 0 serogroups. However, 68% were from one of 10 serogroups (01, 02, 04, 06, 09, 018, 027, 073, 075 and 077) and 36% were from one of only 3 serogroups (02, 04 and 06). Furthermore, the virulence factors were concentrated in strains belonging to the 3 serogroups most frequently detected. Thus, 36 (97%) of the 37 strains of these 3 serogroups showed virulence factors, versus only 19 (29%) of 66 belonging to other serogroups (p < 0.001). CONCLUSIONS: Our results support the special pathogenicity theory and suggest that many cases of community acquired UTI may be caused by a limited number of uropathogenic E. coli strains that produce toxins (Hly+ and/or CNF-1+) and possess P fimbriae or P-related adhesins (with MRHA types III, IVa or IVb), and that usually belong to 02, 04 and 06 serogroups.

Community-Acquired Infections↗
PubMed1994

Processing of MucA protein is required for spontaneous and benzo[a]pyrene-induced reversion of the Escherichia coli trpA23 missense mutation by G.C-T.A transversions: effect of a deficiency in the MutY DNA glycosylase.

We have studied the influence of the processing of MucA protein on the occurrence of base substitution mutations. Escherichia coli strains carrying the trpA23 missense mutation and having a full deletion of the chromosomal umuD/C operon were transformed with plasmids encoding the MucB protein together with either wild-type MucA or the nonprocessable MucA202 protein. The efficient reversion of the trpA23 allele by G.C-T.A transversions in benzo[a]pyrene (B[a]P)-treated cells required the function of a matured MucA protein. This processed protein was also necessary for the occurrence of G.C-T.A transversions targeted at spontaneous DNA lesions and for the SOS mutator effect dependent on the constitutive coprotease activity of the RecA730 protein. In contrast, G.C-T.A transversions reverting trpA23 were spontaneously generated by an SOS-independent mechanism in cells deficient in the MutY DNA glycosylase.

Bacterial Proteins↗
PubMed1994

Mutability of Salmonella tester strains TA1538 (hisD3052) and TA1535 (hisG46) containing the UmuD' and UmuC proteins of Escherichia coli.

We have studied the mutability of Salmonella typhimurium tester strains carrying plasmids in which either the umuDC or the umuD'C operon of Escherichia coli have been cloned. Reversion of the hisD3052 frameshift mutation by benzo[a]pyrene (B[a]P), aflatoxin B1 (AFB1) and 1-nitropyrene (1-NP), was very efficiently promoted by UmuD' (the activated form of UmuD) and UmuC proteins. In contrast, UmuD'C proteins promoted a moderate reversion of the missense hisG46 allele by B[a]P, and were not effective in mediating this reversion by AFB1. The Salmonella tester strain carrying the hisD3052 allele and containing the E. coli UmuD'C proteins has a sensitivity toward frameshift mutagens similar to that of the MucAB containing strain TA98, and may be useful for obtaining a high level of mutants generated by the SOS mutagenic mechanism in the absence of MucAB proteins.

Aflatoxin B1↗