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Biomedical subjects

A F de Castro

Publications and source records attributed to A F de Castro.

At least 19 recordsLinked to original sources
PubMed1997

Genes coding for enterotoxins and verotoxins in porcine Escherichia coli strains belonging to different O:K:H serotypes: relationship with toxic phenotypes.

Seventy-four E. coli strains isolated from piglets with diarrhea or edema disease in Spain were serotyped and examined for production of heat-labile (LT) and heat-stable (ST) enterotoxins (LT-I, LT-II, STaH, STaP, and STb) and verotoxins (VT1, VT2, and VT2v = VTe) by phenotypic (Vero cell assay and infant mouse test) and genotypic (colony hybridization and PCR) methods. In general, an excellent correlation was found between the results obtained with a PCR approach and those determined with biological assays. DNA probes used in the hybridization also showed a very good agreement with phenotypic results, with the exception of a VT1 probe that initially produced 10 false-positive reactions. The gene coding for STb (58 strains) was the most prevalent gene detected by PCR, followed by those coding for STa (46 strains), LT (19 strains), VT2v (11 strains), and VT1 (1 strain). Apparently, in Spain three seropathotypes are predominant: (i) O149:K91:H10 K88+ LT-I+ STb+, (ii) O141:K85ab:H- P987+ STaP+, and (iii) O138:K81:H14 or H- STaP+ VT2v+. We conclude that PCR is a fast, specific, and practical method for the identification of enterotoxin and VT genes in clinical and epidemiological studies.

Animals↗
PubMed1994

Genes coding for Shiga-like toxins in bovine verotoxin-producing Escherichia coli (VTEC) strains belonging to different O:K:H serotypes.

Forty-six verotoxin-producing Escherichia coli (VTEC) strains isolated from diarrhoeic and healthy calves in Spain were examined for DNA sequences homologous to genes for verotoxins (VT1 and VT2) and enterotoxins (LT-I, LT-II, STaH, STaP and STb). Hybridisation showed that 26 (57%) of VTEC strains carried VT1 genes, 13 (28%) possessed VT2 genes, and 7 (15%) carried both VT1 and VT2 genes. No VTEC strains hybridised with DNA probes for enterotoxins. A correlation was found between the serotype and type of VT produced. Thus, all strains of serotypes O26:K-:H11 (13 strains), O103:K-:H2 (3 strains) and O128:K?:H- (4 strains) hybridised with the VT1 probe only, whereas all strains of serotypes O4:K-:H4 (3 strains) and O113:K-:H21 (4 strains) were positive with the VT2 probe only. By contrast, O81:K?:H28 (2 strains) and O157:K-:H- (2 strains) strains hybridised with both VT1 and VT2 probes. One strain of serotype O157:K-:H7 was VT2 positive.

Animals↗
PubMed1993

Bluetongue virus: production and study of viral antigen for serological diagnosis.

A soluble antigen, produced from the culture supernatant of VERO cells infected with bluetongue virus serotype 4 (BTV-S4) and concentrated by sequential ultrafiltration with membranes with cut-off values 10(3) and 25 x 10(3) NMWP, showed complete identity to standard antigens when compared by agar gel immunodiffusion (AGID) and SDS-PAGE profiles, revealing that the main protein component responsible for the AGID reaction has a molecular weight of about 60 kDa corresponding probably to the NS1 protein.

Animals↗
PubMed1993

Rotavirus excretion in naturally infected pigs with and without diarrhoea.

Seven hundred and fifty faecal samples from piglets ranging from 1 to 60 days old were studied for the presence of group A rotavirus by polyacrylamide gel electrophoresis (PAGE) and by enzyme immunoassay (EIA). From 451 diarrhoeic pigs, 117 (25.94%) were positive for rotavirus and only 45 (15.05%) of 299 pigs without diarrhoea excreted the virus (P < 0.005). When these animals were separated into four age groups with regard to the presence or absence of diarrhoea, it was observed that the excretion of rotavirus was associated with diarrhoea in piglets, both before and after weaning.

Animals↗
PubMed1989

Viruses with bisegmented double-stranded RNA in pig faeces.

Viruses similar to the bisegmented double-stranded (ds) RNA picobirnaviruses described in human faeces and the intestinal contents of Oryzomys nigripes rats and guinea pigs were isolated from the faeces of pigs taken from several areas in the state of Sao Paulo, Brazil. Samples were collected from 912 pigs of several breeds, aged nine to 61 days, and assayed by polyacrylamide gel electrophoresis with silver staining and a combined enzyme immunoassay for rotavirus and adenovirus, using the simian rotavirus SA11 as control. Electrophoretic profiles resembling the bisegmented dsRNA viruses were detected in 106 pigs with 15.3 per cent occurring in animals with diarrhoea compared to 9.6 per cent in animals without diarrhoea.

Animals↗
PubMed1983

Factors affecting detection of Yersinia enterocolitica heat-stable enterotoxin by the infant mouse test.

With regard to the assay of heat-stable enterotoxin (ST) from Yersinia enterocolitica, we made a comparative study of the conventional infant mouse test read at 4 h and a modified infant mouse test read at 2 h. The influence of several factors, such as the medium used to prepare ST, lysing of bacterial cells from the broth cultures used to prepare ST, and the temperature at which the inoculated mice were kept during the test, was also investigated. Thus, with a few exceptions, Pai-Mors medium was more suitable than Casamino Acids-yeast extract medium, for the preparation of yersinial ST. Gut/carcass weight ratios obtained with lysed supernatants or with supernatants from whole cultures of Y. enterocolitica were similar, suggesting that most of the ST produced by this microorganism in broth cultures is extracellular. The amount of ST produced by Y. enterocolitica, as well as the ambient temperature at which inoculated mice were kept during the assay, was found to influence gut/carcass weight ratios obtained with both tests. Enterotoxigenicity and the temperature at which mice were kept were interrelated, such that for weakly enterotoxigenic strains there were no significant differences among gut/carcass weight ratios for the conventional and modified infant mouse tests carried out at 18 or 25 degrees C, but at 30 degrees C the values in the modified test were higher for most ST preparations with Pai-Mors medium. The influence of ambient temperature was more pronounced at 37 degrees C, since most strains produced negative results in the conventional test at this temperature. We conclude that the conventional infant mouse test is adequate for assaying yersinial ST, provided that the temperature at which mice are kept during the assay is fixed at around 25 degrees C.

Animals↗
PubMed1982

Detection of heat-labile (LT) enterotoxin of enterotoxigenic Escherichia coli by the radial immune hemolysis test: a modification for clinical use.

An adaptation for clinical purposes of a radial immune hemolysis test for the detection of the heat-labile (LT) enterotoxin of the enterotoxigenic Escherichia coli is described. The results correlated well with those from Vero cell assay and the passive immune hemolysis test. Because the test is easy, relatively cheap, and as sensitive as other standard procedures, for LT detection, it is particularly suitable for less-equipped laboratories. Also, a large number of E. coli strains may be examined daily by this technique.

Bacterial Toxins↗
PubMed1981

Single radial immune hemolysis test for detection of Escherichia coli thermolabile enterotoxin.

A single radial immune hemolysis test for the detection of thermolabile enterotoxin has been developed for routine purposes. Stationary cultures from enterotoxigenic Escherichia coli in Casamino Acids-yeast extract medium may be used for the detection of this enterotoxin, and under the conditions of the experiment, the single radial immune hemolysis test was as sensitive as the passive immune hemolysis test. The results obtained in the single radial immune hemolysis test agreed entirely with those obtained in the passive immune hemolysis test, and no false-positive reactions were obtained when cholera antitoxin diluted 1:80 was used. The assay is easy to perform, inexpensive, and specially designed for less-equipped laboratories.

Bacterial Toxins↗
PubMed1980

Relationship among enterotoxigenic phenotypes, serotypes, and sources of strains in enterotoxigenic Escherichia coli.

The relationship among O groups, O:H serotypes and enterotoxigenic phenotypes was examined in 76 Escherichia coli strains isolated in Brazil from different sources. Of the 17 heat-labile and -stable enterotoxin (LT/ST)-producing strains whose O antigens were identified, 15 belonged to serotypes O6:H16 (7 strains), O63:H- (5 strains), and O139:H28 (3 strains). All 11 ST strains were in group OO128PAC, which was represented by four O:H serotypes. The 23 LT strains with the O antigen identified were distributed among serotypes of 14 O groups. Colonization factor CFA/I was not found in any of the LT strains, but it was found in six LT/ST and three ST strains. On the whole, each E. coli O:H serotype had a particular fermentation pattern. LT/ST as well as ST strains were all isolated from patients with diarrhea, whereas LT strains were isolated from patients with diarrhea, normal children, food, and river water.

Bacterial Toxins↗
PubMed1980

Improvements in the passive immune hemolysis test for assaying enterotoxigenic Escherichia coli.

The sensitivity of the passive immune hemolysis test for the detection of heat-labile enterotoxin from Escherichia coli was increased when the test was carried out with Veronal-buffered saline plus Ca2+ and Mg2+ as diluent, instead of phosphate-buffered saline. The performance of the test was further improved by using stationary cultures to which mitomycin C had been added at the end of the lag phase.

Adrenal Glands↗
PubMed1980

[Infant mouse test for the assay of thermostable (ST) enterotoxin from Escherichia coli. Histological studies and influence of mice age (author's transl)].

Mices with different ages ranging 1 to 60 days old were inoculated with thermostable (ST) enterotoxin of Escherichia coli, either by intragastric injection through the abdominal wall or by intubation. Doses were proportional to body weight and values obtained for intestines/carcass weight ratios (RI/C) of inoculated mice showed that mice remained susceptible to the enterotoxin up to 16 days old, with RI/C values equal or greater than 0.085. Older mice were completely resistant to ST activity as RI/C values demonstrated. Histological observations showed that whole gut's fixation of inoculated mice was absolutely necessary since any handling of intestinal loops evoked artifactual alterations. Even though, alterations were found, probably of mechanical nature, caused by intestinal distension consequent to the increased fluid volume into gut's lumen. These alterations did not differ from those observed for both cholera and LT-E. coli enterotoxins, characterized by lymphatic and blood vascular dilatation within mucosae lamina propria, eventually shrinkage of lamna propria just below the epithelium as well epithelial's vacuolizations.

Age Factors↗