PubMed Health⌕ Search

Biomedical subjects

L W Riley

Publications and source records attributed to L W Riley.

At least 73 records · Page 4Linked to original sources
PubMed1993

Isolation of Mycobacterium avium complex from bone marrow aspirates of AIDS patients in Brazil.

Mycobacterium avium complex (MAC) infection has not been reported as a major opportunistic infection among patients with AIDS in Latin America or Africa. In this study, 125 AIDS patients who had persistent fever, anemia, and leukopenia were examined among 2628 AIDS patients admitted to Instituto de Infectologia Emilio Ribas between May 1990 and April 1992. From the bone marrow aspirates of the 125 patients, MAC was isolated from 23 (18.4%) and Mycobacterium tuberculosis was isolated from 9 (7.2%). Between 1985 and 1990, only 11 MAC isolations among 60,000 cultures obtained from human immunodeficiency virus-seronegative patients were documented in São Paulo. Hence, the minimal estimated rate of MAC infection in AIDS patients in this city was 23/2628, or 0.88%. These findings suggest that MAC infection is an important opportunistic infection, especially among a subset of patients with AIDS in Brazil who have clinical characteristics and risk activities similar to those associated with MAC infections in North America and Europe.

AIDS-Related Opportunistic Infections↗
PubMed1993

Catalase-peroxidase gene sequences in isoniazid-sensitive and -resistant strains of Mycobacterium tuberculosis from New York City.

Isoniazid resistance in Mycobacterium tuberculosis is associated with lack of catalase-peroxidase activity. A recent study showed that some isoniazid-resistant M. tuberculosis strains have a complete deletion of the gene (katG) encoding this enzyme. To examine what proportion of clinical isolates of M. tuberculosis have katG deletion, katG sequences in 80 randomly selected isolates from New York City were analyzed. Polymerase chain reaction was used to amplify a 282-bp segment of M. tuberculosis katG and showed that 35 (90%) of 39 isoniazid-sensitive and 31 (76%) of 41 isoniazid-resistant strains contained katG sequences (P > .1). Ten multidrug and high-level isoniazid-resistant strains with identical restriction fragment length polymorphism patterns were also analyzed. All were found to have katG sequences. These findings suggest that mechanisms other than complete deletion of katG are involved in isoniazid resistance among most clinical isolates of M. tuberculosis from New York City.

Base Sequence↗
PubMed1991

Behavioural risk factors for acquisition of HIV infection and knowledge about AIDS among male professional blood donors in Delhi.

In 1989-90 a study was carried out in Delhi of the risk behaviours and epidemiological characteristics exhibited by 15 paid blood donors who were positive for human immunodeficiency (HIV) virus and on 100 paid seronegative donors. All the donors were male. Compared with the seronegative donors, a significantly greater proportion of seropositive donors were unmarried, had lived in at least two cities in the previous 5 years, donated blood at least once per month, were heterosexually promiscuous, and had visited a clinic for sexually transmitted diseases. Awareness about acquired immunodeficiency syndrome (AIDS) was poor, and even those donors who had heard of AIDS were ignorant about certain important aspects. The results indicate that, based on the risk factors identified in this study, there is a need to adopt more careful selection criteria for blood donors in India.

Acquired Immunodeficiency Syndrome↗
PubMed1990

HeLa cell invasion by a strain of enteropathogenic Escherichia coli that lacks the O-antigenic polysaccharide.

The interaction with HeLa cells of an enteropathogenic Escherichia coli (EPEC) strain and its plasmid-cured derivative strain was examined. An O111:NM EPEC strain B171 harbours a 54 megadalton plasmid (pYR111) necessary for the expression of both localized adherence (LA) to HeLa cells and the O-repeating side chain of the lipopolysaccharide. Under light microscopy, the plasmid-cured derivative strain B171-4 was observed to interact with HeLa cells in a pattern distinct from LA. Transmission electron microscopy showed that the bacteria were internalized by HeLa cells. In contrast, strain B171 induced pedestal-like projections and invaginations of the plasma membrane, but was never completely internalized. A quantitative assay to determine the number of internalized bacteria revealed that strain B171-4 was internalized at levels 30-70-fold higher than those of avirulent E. coli strains. Cytochalasin B reduced the levels of internalization of both strain B171-4 and an enteroinvasive E. coli strain (E11), but did not affect LA by strain B171. These results suggest that EPEC strain B171 may carry a specific chromosomally determined surface factor needed to initiate internalization by HeLa cells. However, a plasmid-determined factor alters the nature of this interaction; the combined effects of the chromosomal and plasmid determinants lead to the characteristic attachment of the bacteria in clusters on the surface of the eukaryotic cell.

Antigens, Bacterial↗
PubMed1990

Influence of the 60-megadalton plasmid on adherence of Escherichia coli O157:H7 and genetic derivatives.

The adherence of enterohemorrhagic Escherichia coli serotype O157:H7 and various genetic derivatives to Henle 407 intestinal and HEp-2 epithelial cell lines was examined by light and electron microscopy. The parent outbreak strain, 7785, harbors a 60-megadalton serotype-specific plasmid designated pO157 and adhered to both cell lines, as determined by light microscopy. A plasmidless derivative, 2-45, showed reduced adherence to both cell lines. After being labeled with Tn801, pO157 was transformed into E. coli C600, E. coli HB101, and E. coli GH42, and back into 2-45. Both E. coli C600 and HB101 transformants adhered weakly; full adherence was restored to the 2-45(pO157::Tn801) transformant. Transmission electron microscopy (EM) demonstrated the intimate attachment of HB101(pO157::Tn801) to Henle 407 cells which formed cuplike structures and areas of possible actin polymerization adjacent to adhering bacterial cells; scanning EM further extended these observations. EM studies of E. coli O157:H7 strains were hampered by extensive intestinal cell damage, presumably due to the action of Shiga-like toxins. EM also demonstrated that 7785 and its plasmidless derivative 2-45 were piliated and that no pili were apparent on HB101(pO157::Tn801) or GH42//(pO157::Tn801). The plasmid pO157 appears to modify the eucaryotic cell adherence of E. coli O157:H7 and to confer that adherence on E. coli HB101 through surface structures other than pili. These findings, when compared with other published reports, also suggest similarities between enterohemorrhagic and enteropathogenic E. coli adherence properties.

Bacterial Adhesion↗
PubMed1990

Comparison of alkaline phosphatase-conjugated oligonucleotide DNA probe with the Sereny test for identification of Shigella strains.

We compared an alkaline phosphatase-conjugated oligonucleotide DNA probe with the Sereny test to determine the sensitivity and specificity of the probe in detecting virulent Shigella strains. The probe hybridized with all 52 Sereny-test-positive strains (sensitivity, 100%) and 4 of 21 Sereny-test-negative strains (specificity, 81%). The probe did not hybridize with any of the Sereny-test-negative S. dysenteriae type 1 strains. This nonradioactive, synthetic probe provides a simple, rapid way to test a large number of strains simultaneously in a field setting, which will contribute to an improved understanding of the epidemiologic patterns of shigellosis in developing countries.

Alkaline Phosphatase↗
PubMed1990

[Risk factors for acute infantile diarrhea in a rural community in Chiapas, Mexico. A strategy for intervention].

A community-based, case-control study was conducted during the summer peak season for diarrhea in the highlands of Chiapas, Mexico, to identify risk and protective factors associated with acute diarrhea in children less than 6 years of age. To estimate the diarrheal morbidity rate, the community was divided into 13 sectors, each of about 20 households. A resident (volunteer mother) made daily visits to every household in her sector to identify new cases of diarrhea. During 3 weeks of surveillance, 63 children with diarrhea and 48 control children were identified. The diarrheal attack rate during this period for children less than 6 years of age was 30%. Analysis of 29 neighborhood-matched case-control pairs showed that children with diarrhea were more likely than their controls to have had a mother with diarrhea in the 2 weeks preceding the onset of the child's diarrhea (P less than 0.05; relative risk = 10). The association of childhood diarrhea with maternal diarrhea may serve as a focus for more detailed studies as well as an intervention that may be appropriate and effective for this community.

Adult↗
PubMed1990

Cholera outbreak in Delhi--1988.

Delhi experienced an outbreak of cholera during July-August 1988 which affected residents from all walks of life. A total of 1824 laboratory confirmed cholera cases were detected in two months period at I.D. Hospital, Delhi alone. The number of cholera cases in July-August 1988 was 5-10 times that of the same period during the previous years in the Capital. The outbreak was caused by Vibrio cholerae Ogawa biotype ElTor. Majority of the laboratory confirmed cases (about 74 per cent) were seen in children under the age of 15 years. Though the cases were spread all over Delhi, almost three-fourths of total cases were reported from two specific zones (Shahdara and Civil Lines). Most of the isolates were sensitive to all antibiotics tested. The proportion of isolates resistant to furazolidone during this outbreak was substantially higher than in previous years suggesting that the outbreak may have been caused by the introduction of a new strain rather than proliferation of endemic strain. The salient features of the outbreak are discussed.

Adolescent↗
PubMed1990

Risk factors for acute childhood diarrhea in the highlands of Chiapas, Mexico: a strategy for intervention.

A case-control study was conducted in the highlands of Chiapas, Mexico, to identify factors associated with acute diarrhea in children less than six years old. The study found that the diarrhea attack rate among the children surveyed during three weeks in the month of August (the peak diarrhea season) was approximately 30%, and that children whose mothers had diarrhea were especially likely to contract the illness themselves. The methods employed could prove relevant to studies in other areas, and the results obtained could provide the basis for more detailed study of the area involved--and for preventive action.

Case-Control Studies↗
PubMed1989

The epidemiologic patterns of drug-resistant Mycobacterium tuberculosis infections: a community-based study.

A community-based study of tuberculosis in Santa Clara County, California was conducted in order to identify community-specific determinants of drug-resistant Mycobacterium tuberculosis infections. From January 1984 through December 1986, 517 verified cases of tuberculosis were reported from the county. Drug susceptibility test results to isoniazid, streptomycin, ethambutol, and rifampin were available for 256 of the 517 cases. The frequency of resistance of M. tuberculosis isolates to one or more drugs was 27% for all cases and 25% for those who had had no previous antituberculosis treatment. Isolates from Asian immigrants had the highest frequencies of resistance (33 to 45%), and the Southeast Asian immigrants had a drug-resistant tuberculosis case rate greater than 30/100,000 population per year. In patients who had cavitary lung disease and who had a previous history of tuberculosis, drug-resistant tuberculosis was 3.5 times as likely to occur than in persons who had neither of these characteristics (p less than 0.001). For such patients, the positive predictive value of isolating resistant M. tuberculosis approached 90%. We believe these community-based findings will guide clinical and public health interventions specifically appropriate for the community.

Antitubercular Agents↗
PubMed1987

Plasmid-encoded expression of lipopolysaccharide O-antigenic polysaccharide in enteropathogenic Escherichia coli.

The role of a plasmid in the virulence activity of an enteropathogenic Escherichia coli (EPEC) strain belonging to serotype 0111:NM was examined. EPEC strain B171, which is resistant to chloramphenicol, streptomycin, sulfathiazole, and tetracycline, harbors a 54-megadalton plasmid, pYR111, and exhibits localized adherence (LA) with HeLa cells. Curing the plasmid yielded strain B171-4, which had lost the ability to exhibit LA, resistance to the antibiotics, and the lipopolysaccharide (LPS) O-antigenic polysaccharide. To confirm that these phenotypic characteristics were specified by pYR111, the plasmid was transferred by conjugation into a nalidixic acid-resistant strain of E. coli HB101. LA and antimicrobial resistance were expressed in most of the transconjugants examined. The O-polysaccharide side chains, antigenically reactive with O111-specific antiserum, were also expressed by the transconjugants. Although EPEC plasmids coding for both drug resistance and LA have been described, an EPEC plasmid encoding the expression of an LPS O antigen has not been previously reported. Similar findings described for some Shigella and Salmonella strains suggest that plasmid-encoded modification of the LPS in some enteric bacterial species may be more common than previously recognized and may contribute to the characteristic virulence activity of the organism.

Antigens, Bacterial↗
PubMed1987

Breast-feeding children in the household as a risk factor for cholera in rural Bangladesh: an hypothesis.

Vibrio cholerae 01 produces symptomatic and asymptomatic infections. In this study, we investigated a cholera epidemic in northern Bangladesh to specifically search for risks of developing symptomatic infection. A case-control study in six villages found that cases were more likely than controls to have in their family a child who was still breast-feeding and who had been asymptomatic during the epidemic. Among 24 case-control pairs with cholera-like diarrhea as cases, there were 11 discordant for the presence of such a child in the family, in 9 of them, the child was in the case-family (relative risk = 4.5, p = 0.033). Among 13 case-control pairs with laboratory-confirmed cholera as cases, there were 7 discordant for the presence of a breast-feeding child, and in 6 of them, the child was in the case-family (relative risk = 6, p = 0.06). Breast-feeding children in this area are usually kept naked, and defecate onto a cloth pad held against their buttocks by a family member who may be repeatedly exposed to the soiled cloth. Symptomatic infection with V. cholerae may depend on exposures to situations that augment the ingested dose of V. cholerae, and these findings led us to hypothesize that breast-feeding children, if infected, may play a substantial role (attributable risk = 55%) in facilitating such transmission in rural Bangladesh.

Adolescent↗
PubMed1986

Diarrhea associated with adherent enteropathogenic Escherichia coli in an infant and toddler center, Seattle, Washington.

During November 1983, the Seattle-King County Department of Public Health investigated an outbreak of diarrhea associated with enteropathogenic Escherichia coli, serogroup 0111:K58, in an infant and toddler day-care center. Of the 25 children in the center, ranging in age from 4 to 30 months (median age 11 months), diarrhea occurred in 14 characterized by watery, greenish stools. The median duration of diarrhea was 12 days. Two of the ill children were hospitalized because of severe dehydration. Stool cultures from the children diagnosed initially did not yield the common bacterial pathogens, parasites, or rotavirus. Stool cultures from 11 of 14 ill children and two of 11 well children (P less than .005), however, yielded an E coli serogroup, 0111:K58, which was not invasive or toxigenic by standard tests. The source of the organism was not identified. Although this organism has been recognized as a cause of diarrhea in newborn nurseries, this is the first published report of a documented outbreak of enteropathogenic E coli-induced diarrhea in a day-care center in the United States.

Child Day Care Centers↗
PubMed1984

Importance of host factors in human salmonellosis caused by multiresistant strains of Salmonella.

Antimicrobial resistance patterns of Salmonella isolates from persons in randomly selected urban and rural counties in the United States were examined along with clinical and epidemiological characteristics of the host. Multiresistant strains, isolated from 66 (12.2%) of 542 persons evaluated, were associated with five of 20 variables in univariate analyses: serotype heidelberg, host of Hispanic origin, host exposure to penicillins within four weeks before stool culture, age greater than or equal to 60 years, and regular antacid use. By multiple linear regression, the first three variables were each significantly associated with infections due to multiresistant Salmonella. One or more of the last three variables, thought to be host factors that may promote disease, were present for persons yielding 38% of multiresistant strains but only 12% of sensitive strains (P less than .001). The relatively large proportion of multiresistant Salmonella among isolates from persons with these risk factors suggests that to cause disease, resistant organisms are more dependent than are sensitive organisms on host characteristics.

Adolescent↗
PubMed1984

The significance of hospitals as reservoirs for endemic multiresistant Salmonella typhimurium causing infection in urban Brazilian children.

To identify possible sources of multiply drug-resistant Salmonella typhimurium among children in São Paulo, Brazil, we reviewed records of 470 children who had visited eight outpatient clinics from March 1981 to May 1982 and of 28 children who had been admitted to one referral hospital between June and November of 1982, and we examined plasmid profiles of the Salmonella isolates by agarose-gel electrophoresis. S. typhimurium was identified in 37 of these children. Case-control studies showed that children with S. typhimurium infections were more likely to have been hospitalized before onset of diarrhea than were either age-matched children without diarrhea (P = .031) or age-matched children with nonbacterial diarrhea (P = .035). Four distinct plasmid profiles, each of which was temporally clustered, were identified in 20 (67%) of 30 S. typhimurium strains isolated from previously hospitalized children and in two (28%) of seven strains from children not previously hospitalized. Each of three of these four profiles was associated with a different hospital, results suggesting that multiresistant-S. typhimurium infections in São Paulo are often nosocomially acquired.

Anti-Bacterial Agents↗
PubMed1984

Sporadic cases of hemorrhagic colitis associated with Escherichia coli O157:H7.

After two outbreaks of hemorrhagic colitis associated with a previously unrecognized pathogen, Escherichia coli O157:H7, a surveillance system was established to identify and study sporadic cases of this distinct clinical illness in the United States. Between August 1982 and April 1984, we identified 28 persons from 11 states who met our case definition and whose stool specimens yielded E. coli O157:H7. Patients ranged in age from 1 to 80 years. Seventeen patients required hospitalization. All patients recovered, although one developed hemolytic-uremic syndrome 7 days after the onset of bloody diarrhea. Detection of E. coli O157:H7 in stools from persons with hemorrhagic colitis was highly associated with collection of stool specimens within the first 6 days after onset of illness. All E. coli O157:H7 isolates produced a Vero cytotoxin. Hemorrhagic colitis caused by E. coli O157:H7 is widely distributed in the United States as a sporadic illness; clinicians should be aware of its distinctive clinical presentation, and should collect specimens promptly when the diagnosis is suspected.

Adolescent↗