Biomedical subjects

V Prado

Publications and source records attributed to V Prado.

At least 55 records · Page 3Linked to original sources

PubMed1994

Molecular evolution of a Y-chromosomal repetitive sequence family in the genus Mus.

A 522-base-long Y-chromosomal sequence was isolated from a BALB/c genomic library and was designated "BF046." It is repeated about 200 times in the male genome, and a difference was detected between the Mus musculus musculus and the M. m. domesticus type Y chromosomes. BF046-related sequences were present over the entire length of the Y chromosome as visualized by in situ hybridization. Southern blot analysis against DNAs isolated from eight species in the genus Mus showed that BF046-related sequences were amplified in the Y chromosomes of three closely related species: M. musculus, M. spicilegus, and M. spretus. To gain insight into the stability of the BF046 sequence family, we isolated 18 additional clones from these three mouse species and compared their sequences. The M. musculus sequences differed from the M. spicilegus and M. spretus sequences by two indels. The remaining parts of the sequences were very similar, but both parsimony and distance-based analytical methods divided the sequences into the same four subgroups, with each species having its own subgroup(s). Thus, the Y chromosomes of M. musculus, M. spicilegus, and M. spretus can be distinguished from one another.

Animals↗

PubMed1994

Acute gastroenteritis in Latin America.

In Latin America, acute gastroenteritis remains to be an important cause of morbidity in adults and a major cause of morbidity and mortality in children. A child under 5 years of age belonging to a low income segment of the Latin American population will develop 5 to 10 bouts of diarrhea every year. The bacterial and viral enteropathogens associated with acute diarrhea are reviewed in this article. Updated information on epidemiologic, clinical, and pathogenic aspects for the relevant enteropathogens is discussed with special emphasis on regional data when available. The current diarrheogenic E. coli classification is particularly discussed. A diagnostic approach to acute gastroenteritis for both the clinical and research laboratories in Latin America as well as guidelines for treatment are proposed.

Acute Disease↗

PubMed1994

[Hemolytic uremic syndrome in childhood: study of several factors potentially related with its genesis].

We measured circulating immune complexes, tumor necrosis factor and antineutrophil cytoplasmatic antibodies in sera coming from 25 patients during the acute reactant phase of the classical form of hemolytic uremic syndrome, aiming to elucidate a potential participation of these parameters in the pathogenesis of the disease. Circulating immune complexes were elevated in the 18 patients in whom they were measured. Tumor necrosis factor was not elevated and antineutrophil cytoplasmatic antibodies were not detected. It is concluded that these results rule out the participation of antineutrophil cytoplasmatic antibodies in the pathogenesis of the disease and that the role of circulating immune complexes, although elevated, remains undefined.

Antigen-Antibody Complex↗

PubMed1993

Epidemiologic studies of Escherichia coli diarrheal infections in a low socioeconomic level peri-urban community in Santiago, Chile.

The incidence of diarrhea due to six categories of diarrheogenic Escherichia coli was determined in two pediatric cohorts in a low socioeconomic level community in Santiago, Chile, with access to chlorinated water. An age cross-sectional cohort of 340 children aged birth to 47 months was assembled. A newborn cohort was assembled by enrolling 10-12 newborns monthly for 12 months. Episodes of diarrhea were detected by twice weekly household visits. E. coli from stool cultures of cases and matched controls were hybridized with DNA probes specific for enterotoxigenic, enteroinvasive, enteropathogenic, enterohemorrhagic, enteroaggregative, and diffuse adherence E. coli. Overall, the incidence of diarrhea was low (2.1 episodes/infant/year). Nevertheless, a putative E. coli enteropathogen was found in a large proportion of diarrheal episodes, particularly during the summer. In both cohorts, enterotoxigenic E. coli were important pathogens. Enteropathogenic E. coli were incriminated during the first year of life in the newborn cohort, where they were found significantly more often in cases (p = 0.021) than in controls; beyond this age, isolation rates were similar. In contrast, the relative risk of isolation of diffuse adherence E. coli increased with age in the age cross-sectional cohort, where, overall, the difference in rate of isolation between cases and controls was significant (p = 0.0024). Enteroinvasive and enterohemorrhagic E. coli were isolated infrequently. Enteroaggregative E. coli were encountered equally in cases and controls. Facile transmission of E. coli enteropathogens is occurring in this community despite the availability of potable water.

Case-Control Studies↗

PubMed1993

Assessment of enterotoxin production by Yersinia enterocolitica and identification of a novel heat-stable enterotoxin produced by a noninvasive Y. enterocolitica strain isolated from clinical material.

Twenty-eight clinical isolates of Yersinia enterocolitica were investigated for their abilities to produce heat-stable enterotoxin (YST). All 21 invasive strains (serogroup O3 biotype 4) carried the previously described gene for YST (yst), with toxin detectable in culture supernatants from 20 strains. One of seven noninvasive, biotype 1A strains also had enterotoxic activity, despite failure to hybridize with a probe for yst. The toxin produced by this noninvasive (serogroup O6) strain resembled YST in terms of molecular size, heat stability, and solubility in methanol. It differed from YST, however, with respect to regulation of its production by temperature and its mechanism of action, which did not appear to involve cyclic GMP.

Animals↗

PubMed1993

Hemolytic uremic syndrome: co-infection with two different serotypes of Shiga-like toxin producing Escherichia coli.

We report a case of a child who developed Hemolytic Uremic Syndrome in whom two Shiga-like toxin (SLT)-producing Escherichia coli strains of different serotypes and genotypes, were simultaneously isolated from stools. In addition, one of these strains represented a new toxin producing serotype. Strain 1 belonged to serotype O157: H7, biotype D, produced SLT II and was susceptible to all antibiotics tested. This strain hybridized with gene probes for SLT II, fimbrial adhesion (EHEC factor) and attaching and effacing factor (eae). Strain 2 belonged to serotype 025: K2: H2, produced SLT II and had a multiresistant antibiotic susceptibility pattern. This strain hybridized with the EHEC gene probe but not with SLT I, SLT II and eae gene probes. Free fecal SLT II cytotoxin was detected in stools of the child and his father, suggesting that the infection may have been acquired from a household contact.

Bacterial Toxins↗

PubMed1993

[Comparative in vitro activity of new oral macrolides against Streptococcus pyogenes strains].

Some recently introduced macrolides have several clinical advantages over erythromycin. Azithrommcin, a prototype of these new macrolides could be a good alternative for the treatment of streptococcal pharyngitis, even over penicillin, whose failure rate can be as high as 30%. The aim of this study was to evaluate the in vitro susceptibility of 120 strains of S pyogenes isolated between 1990 and 1992 (40 per year), from diverse infections (specially tonsillitis). We determined Minimal Inhibitory Concentrations (MIC) of azithromycin, clarithromycin, roxithromycin, erythromycin and penicillin using the agar dilution method and the Minimal Bactericidal Concentration (MBC) by tube dilution for azythromycin and erythromycin. The MIC 90 for the new macrolides ranged from 0.03 to 0.12 microgram/ml, and was 0.03 microgram/ml for erythromycin and penicillin (not different). All strains were susceptible to all antibiotics and the date of isolation did not influence susceptibility. The MBC for azithromycin was 0.12 microgram/ml (identical to its MIC), which demonstrates the bactericidal effect of this antibiotic. It is concluded that this in vitro data supports the potential role of these new macrolides in the treatment of streptococcal infections.

Anti-Bacterial Agents↗

PubMed1993

[Pathogenic potential of vibrio cholerae 01 isolated from the Mapocho river and Aguada ditch].

The pathogenic potential of 20 strains of Vibrio Cholerae 01 isolated from the Mapocho river and Aguada ditch in Santiago, Chile was studied using a rabbit intestinal loop biological model. The presence of cholera toxin (CT) was previously found by the detection of CT gene, ELISA and passive reserve agglutination in only one of these strains. After 24 h of intestinal loop inoculation, the 20 strains showed enterotoxic activity. In four of these strains the secretory reaction was particularly intense. In these same four strains, the presence of cholera toxin was detected after the passage through the animal model. Thus, the number of cholera toxin producing strains increased after the inoculation in intestinal loops. These results suggest that the enterotoxic activity of strains that do not produce CT is given by the new cholera toxin (NCT). It is concluded that most of the strains of Vibrio Cholerae isolated from Mapocho river and its affluents are producers of NCT toxin, that some strains recover the capacity to produce CT after colonization of intestinal loops of living organisms and that the additive effects of CT and NCT may explain the intense enterotoxic activity of the strains that produce CT.

Animals↗

PubMed1993

[Tolerance and immunogenicity of an oral dose of CVD 103-HgR, a live attenuated Vibrio cholerae 01 strain: a double-blind study of Chilean adults].

CVD 103-HgR is an attenuated, AB+, live, recombinant vaccine strain, developed by deletion of the toxA gen in a virulent Vibrio cholerae 01, Inada classical strain (569B). In phase II studies conducted to date, CVD 103-HgR has been well tolerated and immunogenic in volunteers from both industrialized countries and cholera-endemic areas. In this study of safety, immunogenicity and excretion, 81 Chilean adults were randomly allocated to receive, in a double blind fashion, a single oral dose of 5 x 10(9) FU of CVD 103-HgR or placebo, (5 x 10(9) heat-killed E. Coli K12 organisms), in 100 ml of buffered water. Side effects were assessed by daily visits to the participants. Immunogenicity, (vibriocidal seroconversion), was investigated in blood drawn before and on days 8 and 28 after immunization, while stool cultures to assess excretion of the vaccine strain were performed on specimens obtained on days 1 and 7. None of the participants, (40 vaccinees and 41 placebo recipients), experienced untoward effects during 30 minutes of close surveillance after ingestion of the preparation; upon follow up, neither adverse events were more frequently reported by the vaccinees. 34/40 vaccinees, and 2/41 participants receiving placebo had a significant raise, (> = fourfold), in their vibriocidal titers; (85 vs 2%, p < 0.001). The peak postimmunization geometric mean titer, (222), was ten fold higher than the baseline vibriocidal titer. The vaccine strain was recovered in stool cultures from 8 participants, one of them excreted the strain in both specimens. We conclude that CVD-103-HgR is safe and immunogenic in Chilean adults.

Administration, Oral↗

PubMed1993

[Antimicrobial activity of amoxicillin versus amoxicillin/clavulanic acids. In vitro study against S aureus, H influenzae and A baumanii strains].

The aim of this study was to compare in vitro activity, measuring minimal inhibitory concentration, of amoxicillin or its combination with clavulanic acid against 109 strains of Acinetobacter baumanii, 104 strains of Hemophilus influenzae and 94 strains of Staphylococcus aureus. All these were obtained from different hospitals of the Santiago Metropolitan Region. Amoxicillin-clavulanic acid association did not improve the activity of amoxicillin against Acinetobacter. The association was not active against methicillin resistant strains of S aureus; instead, it significantly increased the activity of amoxicillin against methicillin susceptible strains. All the H influenzae strains were susceptible to the combination.

Acinetobacter↗

PubMed1992

Enterohemorrhagic Escherichia coli associated with hemolytic-uremic syndrome in Chilean children.

A clinicoepidemiological study was undertaken to determine if enterohemorrhagic Escherichia coli (EHEC) was associated with hemolytic-uremic syndrome (HUS) in children in Santiago, Valdivia, and Temuco, Chile. Prospective surveillance detected 20 hospitalized cases of HUS in children less than 4 years of age in these cities from March 1988 to March 1989. Each HUS patient was matched (by sex and age) with two control children (hospitalized elective-surgery patients). To detect EHEC, DNA from stool culture isolates of E. coli was detected by hybridization with biotin-labelled DNA probes specific for the EHEC virulence plasmid, Shiga-like toxin I (SLT-I) or SLT-II. Stool cultures from 6 of 20 cases (30%) and from 2 of 38 controls (5.3%) yielded EHEC (P = 0.0158). EHEC isolates from all HUS cases hybridized with the EHEC plasmid probe and with probes for SLT-I or -II (or both). The serogroups of the isolates included O157, O26, and O111. EHEC causes HUS in Chile, and the biotinylated gene probes are practical diagnostic tools for epidemiologic studies.

Bacterial Toxins↗

PubMed1991

Epidemiologic patterns of acute diarrhea and endemic Shigella infections in children in a poor periurban setting in Santiago, Chile.

To prepare a field site for evaluating preventive interventions against endemic shigellosis, the authors followed prospectively a cohort of 360 children (90 each of children aged 0-11, 12-23, 24-35, and 36-47 months) in Santa Julia, a low socioeconomic area in Santiago, Chile, from November 1986 through April 1989 with twice weekly household visits for diarrheal disease; infants replaced children who reached 60 months of age. Coprocultures on 2 consecutive days from children with diarrhea and from age-matched controls within the cohort were cultured for Shigella. Bacteriologic surveillance was also maintained in the health center and children's hospital serving Santa Julia. In this community, where all households had access to potable water (68% inside) and all but 3% had access to a toilet, but where there was marked crowding, the overall incidence of diarrheal disease in the cohort was low (2.26 episodes/12 child months of observation in children aged 0-11 months and 2.09 in those aged 12-23 months), yet Shigella infections were common. Shigella accounted for 10% of diarrheal episodes in the cohort (vs. 3.2% isolation rate in controls, p less than 0.0001). The incidence of shigellosis in children aged 12-47 months was 0.16 cases per 12 child months of observation; in the first 5 years of life, a child had a 67% chance of experiencing shigellosis. Shigella sonnei, Shigella flexneri 2a, and S. flexneri 6 caused greater than 79% of the infections. Shigella occurred more often in hospitalized cases of diarrhea than in age-matched cases detected in the health center or by household surveillance (p less than 0.0001). An initial episode of Shigella diarrhea did not diminish overall the risk of subsequent shigellosis but did confer 72% protection (p = 0.05) against illness due to the homologous serotype. The high rate of both S. sonnei and S. flexneri shigellosis in a population with a low background rate of diarrhea makes Santa Julia an appropriate site for assessing the efficacy and effectiveness of measures to reduce Shigella infections.

Acute Disease↗

PubMed1991

Yersinia enterocolitica isolated from two cohorts of young children in Santiago, Chile: incidence of and lack of correlation between illness and proposed virulence factors.

Yersinia enterocolitica was isolated from children in two cohorts in Santiago, Chile. In a cohort containing a cross section of children aged 0 to 4 years, Y. enterocolitica was isolated from stool samples of 1.1% of children with diarrhea and 0.2% of age-matched control children. In a subgroup of this cohort from which weekly stool samples were obtained from all children irrespective of clinical status, 6% of children had asymptomatic Yersinia infections. In a birth cohort (with a greater representation of children less than 1 year of age and a significantly higher rate of diarrhea), Y. enterocolitica was isolated from 1.9% of children with diarrhea and 0.6% of controls (P = 0.05). Biogroup 1A strains (which lacked traditional phenotypic and molecular markers for pathogenicity) were isolated from seven children with diarrhea but from no control children in the birth cohort (P = 0.02). All other isolates, including all isolates from asymptomatic children, were "pathogenic" strains in biogroup 4, serogroup O3; no association between these isolates and occurrence of disease was found. Y. enterocolitica is found among young children in Santiago, with asymptomatic infections not uncommon occurrences. However, questions about the association between previously described virulence factors and diarrheal illness remain.

Bacterial Typing Techniques↗

PubMed1990

Practical and economical method for using biotinylated DNA probes with bacterial colony blots to identify diarrhea-causing Escherichia coli.

A simple and economical method was developed for using biotinylated DNA probes to hybridize with bacterial colonies belonging to the various categories of diarrhea-causing Escherichia coli. Simplification and cost containment were achieved by using Whatman no. 541 filter papers instead of nitrocellulose, by minimizing the concentration of proteinase K (an expensive but necessary reagent used to pretreat the colony blots prior to hybridization with biotin-labeled DNA probes) and by reusing hybridization solution containing labeled probe DNA. After exposing the colony blots to lysing solution and steam, followed by lysozyme (1.5 mg/ml), sucrose (25%), and proteinase K (10 micrograms/ml) treatments, biotinylated probes were used to detect enterotoxigenic, enteropathogenic, enterohemorrhagic, diffuse adherence, and enteroinvasive categories of diarrhea-causing E. coli with a high level of sensitivity and specificity. Three independent observers who were experienced in reading DNA blots recorded remarkably similar results, while less satisfactory results were obtained when the blots were read by an inexperienced observer. This technique will be useful in laboratories in which radioactive isotopes are unavailable or impractical and in which budgets are restricted.

Biotin↗

PubMed1990

[Haemophilus influenzae carriers among child care personnel: its prevalence and the efficacy of enoxacin in its elimination].

In a previous study we observed that 6% of adult and 18% of children contacts of H. influenzae infected patients became carriers of the bacillus. We studied 1296 adults involved in children care, 398 from day care centers and 898 from hospitals in Santiago. A pharyngeal sample was cultured in chocolate agar plus bacitracin (300 mg/ml) and incubated at 37 degrees C in a 5-10% CO2 atmosphere for 18-24 h. Isolates of H influenzae were biotypified and serogrouped according to international recommendations. We observed that 2.4% of subjects were H influenzae carriers. Thirty carriers were treated with 2 doses of enoxacin, 440 mg. All became free of H influenzae at a 30-day follow-up.

Adult↗

PubMed1989

Trimethoprim resistance in enterobacteria isolated in Chile.

Four hundred strains of enterobacteria, isolated before the introduction of trimethoprim as a single agent in Chile, were studied. One hundred and thirty six strains (34%) were resistant to greater than or equal to 8 mg/l of trimethoprim and 118 of these (87%) were also resistant to sulphamethoxazole (156 mg/l). Plasmids were detected in 79% of the trimethoprim-resistant strains; 56% of the strains carried two or more plasmids. Trimethoprim resistance could be transferred by conjugation in 66% of the plasmid-carrying strains; this resistance was co-transferred with a variety of other antibiotic resistance determinants.

Chile↗

PubMed1989

[In vitro activity of ampicillin and ampicillin-sulbactam on diverse bacteria].

A foremost mechanism of bacterial resistance to penicillin and its derivatives is the chromosomal or plasmid mediated production of B-lactamase. Inhibitors of these enzymes like sulbactam may help overcome this problem. We tested the in vitro activity of ampicillin alone or in association with sulbactam (1:1 ratio) against enterobacteriaceae, aeromonae, Hemophilus influenzae, staphylococci and Streptococcus fecalis, isolated from patients suffering different infectious diseases. The Kirby-Bauer method was used to evaluate susceptibility and MIC was determined by agar dilution techniques. Most enterobacteriaceae and aeromonae were resistant to ampicillin. The association was effective against shigellae and Yersinia enterocolitica. 28% of H. influenzae strains were resistant to ampicillin alone but were susceptible to the association. 30% of resistant staphylococci became sensitive to the association.

Ampicillin↗

PubMed1989

[Campylobacter pylori in children and adults subjected to endoscopy, correlation of endoscopic, bacteriologic and histopathologic findings].

Campylobacter pylori has been associated to peptic ulcer and gastritis. We investigated the presence of C pylori in 17 children and 50 adults who needed endoscopy to investigate upper gastrointestinal symptoms. Gram stain, Whartin-Starry stain and the urease test were used to identify the germ; best results were obtained with the Gram stain. C pylori was present in 5.8% of children and 88% of adults, including all patients with peptic ulcer and 36 out of 39 with histologic evidence of gastritis. However, the germ was also found in 79% of patients with a normal mucosa. Our results suggest that C pylori is frequently present in gastric mucosa of children and adults with upper gastrointestinal problems. Further studies are needed to elucidate its possible pathogenic role in gastritis or peptic ulcer.

Adolescent↗