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Biomedical subjects

D N Taylor

Publications and source records attributed to D N Taylor.

At least 109 records · Page 6Linked to original sources
PubMed1989

Determination by DNA hybridization of Shiga-like-toxin-producing Escherichia coli in children with diarrhea in Thailand.

Specific DNA probes were used to identify Shiga-like-toxin (SLT) I- and II-producing Escherichia coli from children less than 5 years of age with bloody diarrhea, in infants with diarrhea, and in controls of the same age without diarrhea in Thailand. At one hospital, SLT-producing E. coli was identified in 4 (7%) of 54 children with bloody diarrhea from whom other enteric pathogens were not identified and from 3 (6%) of 50 children without diarrhea. In the positive specimens, SLT-producing E. coli constituted only 0.3 to 4% of the 100 to 300 colonies on the replica blots. Non-toxin-encoding 933J and 933W bacteriophagelike DNA sequences were detected by colony hybridization with E. coli isolates from 18 (33%) of 54 children with bloody diarrhea and 23 (46%) of 50 controls. At another hospital, SLT-producing E. coli was not identified in 115 infants with diarrhea and 119 controls without diarrhea. One infant with diarrhea was infected with E. coli O76:H7 that hybridized with the enterohemorrhagic E. coli probe but not with the SLT probes. E. coli producing SLT I or SLT II was isolated in small numbers from a similar proportion of Thai children with bloody diarrhea in whom no other enteric pathogen was identified and from controls without diarrhea.

Bacterial Toxins↗
PubMed1989

Examination of colonies and stool blots for detection of enteropathogens by DNA hybridization with eight DNA probes.

We compared three methods for detecting enteropathogens in 416 children with diarrhea: (i) examination of 10 lactose-fermenting and all non-lactose-fermenting Escherichia coli (colony blots); (ii) examination of 300 colonies (replicate blots); and (iii) determination of the total bacterial growth of stools (stool blots). All specimens were spotted onto Whatman 541 filters and hybridized with specific radiolabeled DNA probes. Enterotoxigenic E. coli was detected in 38 patients by examining colony blots, in 52 patients by examining replicate blots, and in 45 patients by examining stool blots. Enteropathogenic E. coli adhesin factor was detected in 12 patients by colony blots, in 25 patients by replicate blots, and in 16 patients by stool blots. E. coli that hybridized with the enterohemorrhagic E. coli probe was detected in 2 patients by colony blots, in 11 patients by replicate blots, and in 0 patients by stool blots. Shiga-like toxin-producing E. coli was detected in 0 patients by colony blots, in 12 patients by replicate blots, and in 0 patients by stool blots. Shigella spp. were identified by standard bacteriological methods in 82 patients, and enteroinvasive E. coli was identified by colony blots in 11 patients (total, 93), by replicate blots in 56 patients, and by stool blots in 35 patients. Of 82 culture-confirmed Shigella infections, 45 were identified by examining replicate blots with the 17-kilobase-pair probe and 36 were identified by examination with the Ipa probe (P less than 0.05). Examining replicate blots with specific probes identified more enterotoxigenic E.coli (P < 0.005), enteropathogenic E.coli adhesion factor-producing E.coli (P < 0.001), and Shiga-like toxin-producing E.coli (P < 0.005) infections than examining colony blots. More Shigella and enteroinvasive E.coli infections were identified by standard bacteriological methods and examining colony blots with a specific probe than by examining replicate and stool blots (P < 0.001).

Adhesins, Escherichia coli↗
PubMed1989

The effects of cranial TENS on measures of autonomic somatic and cognitive activity.

Peripheral and central nervous system effects of the cranial application of sub-threshold transcutaneous electrical nerve stimulation (TENS), of sinusoid waveform passed between earlobe electrodes at an AC frequency of 100 Hertz, were investigated. In a single-blind study, each of thirty healthy volunteer subjects was administered one 30 minute treatment of either active TENS, placebo TENS or no treatment. Pretreatment to post-treatment changes in measures of autonomic activity (blood pressure, pulse rate, peripheral vasomotor activity), somatic activity (skeletal muscle tension), and anxiety were evaluated. Significant reductions in systolic blood pressure (p less than .05), diastolic blood pressure (p less than .01), pulse rate (p less than .05), peripheral vasomotor activity (marginally significant: p less than .07) and anxiety (p less than .05) were observed subsequent to active. TENS as compared to both placebo TENS and no TENS. No significant placebo TENS effect was observed. Possible mechanisms of action of this form of cranial TENS on the peripheral and central nervous system are discussed.

Adolescent↗
PubMed1989

Introduction and spread of multi-resistant Shigella dysenteriae I in Thailand.

Outbreaks of Shigella dysenteriae I occurred in northeastern Thailand in the fall of 1986 and again in the spring and fall of 1987 for the first time in over 20 years. The epidemic strain of S. dysenteriae I was resistant to tetracycline, streptomycin, chloramphenicol, and trimethoprim-sulfamethoxazole, but susceptible to ampicillin. Trimethoprim resistance was chromosomally encoded by type I dihydrofolate reductase. In Ubon Province, where 10,000 cases of dysentery were reported, there were 3-5 cases of dysentery per 1,000 residents during the peak months, with 2-5 hospitalizations per 100 cases of reported dysentery. There were 2 deaths among 101 hospitalized, culture-confirmed cases. The overall case-fatality rate among reported cases of dysentery in this province was 0.9%. In contrast to S. flexneri infections, which occurred predominantly among children less than 5 years old, S. dysenteriae I infections occurred in all age groups. The large number of susceptibles appeared to be important in allowing rapid spread of S. dysenteriae I. In 1 village, 46% of 434 villagers reported dysentery; S. dysenteriae I was isolated from 24 out of 81 (30%) individuals cultured. Based on the prevalence of IgG antibody to S. dysenteriae I lipopolysaccharide, it was estimated that 76% of the villagers had been infected.

Adult↗
PubMed1989

A comparison of methods for the isolation of Campylobacter species from stool specimens.

Eight methods used for isolation of Campylobacter species were compared. Using a combination of methods Campylobacter species were isolated from 30 (11%) of 270 children with diarrhea seen at Bamrasnaradura Infectious Disease Hospital, Nonthaburi, Thailand. The membrane filter method using a gas generating envelope at 37 degrees C identified 73% of the total positive specimens and was found to be the best isolation method for Campylobacter species from stool specimens. This method identified two strains that failed to grow on antibiotic containing media, and also gave a higher isolation rate of C. jejuni than could be isolated with conventional methods. The combination of the membrane filter method and a selective antibiotic method identified 90% of all isolates. At present the cost of the membrane filter method is higher than other methods. Therefore, the selective antibiotic method (Campy-BAP) with sheep blood under gas mixture at 42 degrees C is recommended for laboratories with limited supplies. Diagnosis by direct smear with 1% basic fuchsin revealed high degree of sensitivity and specificity. This rapid, inexpensive, and simple method could be used to make a presumptive diagnosis of Campylobacter enteritis when isolation methods are unavailable.

Campylobacter↗
PubMed1988

Etiology of diarrhea among travelers and foreign residents in Nepal.

A bacterial pathogen was isolated from 47% of 328 expatriate patients with diarrhea seen at two medical clinics in Nepal in 1986. Enterotoxigenic Escherichia coli (24%), Shigella (14%), and Campylobacter species (9%) were isolated most frequently. Enteroinvasive and adherence factor-positive E coli were isolated from 2% and 1% of patients, respectively. Giardia lamblia was detected in 12% of patients, rotavirus in 8%, and Cryptosporidium and Entamoeba histolytica each in 5%. Blastocystis hominis was present in 33% of patients but in only 9% of those who took trimethoprim-sulfamethoxazole. More than one enteropathogen was detected in 17% of patients. Patients with prolonged symptoms (longer than two weeks) were more likely to have Giardia (27%) and less likely to have Shigella (5%) than were patients with acute symptoms. The isolation rates of bacterial pathogens decreased with length of stay in Nepal. A wide variety of enteropathogens were detected in travelers to Nepal, and Shigella and protozoa were particularly important. Length of time abroad and duration of symptoms were important diagnostic considerations.

Adult↗
PubMed1988

Serological response to plasmid-encoded antigens in children and adults with shigellosis.

The immunological response to plasmid-encoded antigens of virulent Shigella was determined in Thai children less than 4 yr of age and in Thai adults by immunoblot analysis and ELISA. Forty-two percent (8/19) of Thai children and 4% (1/22) of Thai adults with shigellosis developed a greater than or equal to 4-fold rise in IgG antibody titer to water-extracted antigens of Shigella flexneri M90T by ELISA (p = 0.006). Two children and one lactating mother with shigellosis developed a 4-fold rise in serum IgA antibody titers to water-extracted antigens of M90T. The results of the ELISA were confirmed by immunoblot analysis in all of the 41 paired sera examined. Five patients developed IgA, and four developed IgM, antibodies as detected by immunoblot analysis, that were not detected by ELISA. The reciprocal log2 geometric mean titers of antibodies to plasmid-encoded antigens in acute sera was higher in Thai adults than Thai children: IgG 7,265 versus 1,659; IgM 879 versus 480; and IgA 662 versus 60 (p less than 0.001). Thai adults had high titers of antibodies to plasmid-encoded antigens in their acute sera, but were susceptible to Shigella infections, although they were historically less susceptible than Thai children.

Adult↗
PubMed1988

Application of DNA hybridization techniques in the assessment of diarrheal disease among refugees in Thailand.

The epidemiology and etiology of acute diarrheal disease were determined in a Hmong refugee camp on the Thai-Laotian border from April 11 to May 14, 1985. DNA hybridization techniques were used to detect Shigella species, enteroinvasive Escherichia coli, and enterotoxigenic E. coli. A monoclonal enzyme-linked immunosorbent assay was used to detect rotavirus, and standard microbiology was used to detect other enteropathogens. The age-specific diarrheal disease rates were 47 episodes per month per 1,000 children less than five years old and 113 episodes per month per 1,000 children less than one year old. Rotavirus, enterotoxigenic E. coli, Campylobacter, and Cryptosporidium were the predominant pathogens in children less than two years old. The DNA probe hybridized with 94% of 31 specimens identified as enterotoxigenic E. coli by the standard assays and with none of the specimens in which the standard assays were negative. The probe for Shigella and enteroinvasive E. coli hybridized in eight of 10 stools that contained Shigella and four of 314 stools from which Shigella and enteroinvasive E. coli were not isolated. The use of DNA probes allows specimens to be collected in remote areas with a minimum amount of equipment and technical expertise so that they can be easily transported to a central laboratory for further processing.

Acute Disease↗
PubMed1988

Evaluation of 500- and 1,000-mg doses of ciprofloxacin for the treatment of chancroid.

A randomized, double-blind study was performed comparing ciprofloxacin in a 500-mg single dose with 1,000 mg (500-mg doses given 12 h apart) for the treatment of chancroid in Thailand. Haemophilus ducreyi was isolated from 87 (48%) of 180 men with a clinical diagnosis of chancroid. For men with ulcers that were culture positive for H. ducreyi, rates of cure were 100% in the 500-mg group and 98% in the 1,000-mg group. For men with ulcers that were culture negative for H. ducreyi, rates of cure were 93% in the 500-mg group and 96% in the 1,000-mg group. The MIC of ciprofloxacin for 50% of isolates among 85 isolates of H. ducreyi was 0.007 micrograms/ml (range, 0.002 to 0.03 micrograms/ml). No significant adverse effects were detected in either group. These data indicate that both of these treatment regimens are equally effective therapies for chancroid in Thailand.

Adult↗
PubMed1988

Type II heat-labile enterotoxin-producing Escherichia coli isolated from animals and humans.

Heat-labile enterotoxin (LT)-producing Escherichia coli strains, as identified by the Y1 adrenal cell assay, were examined with a DNA probe coding for type I and type II LTs. Of 236 LT-producing E. coli isolates, 60% hybridized with LT-I, 17% hybridized with LT-II, and 23% did not hybridize with either probe and no longer produced LT as determined by the Y1 adrenal cell assay. These isolates presumably lost plasmids coding for LT-I during storage. A total of 75% of LT-producing E. coli isolates (27 of 36) from cows, 64% of LT-producing E. coli isolates (7 of 11) from buffalo, 31% of LT-producing E. coli isolates (4 of 13) from beef obtained in markets, and 2% of LT-producing E. coli isolates (3 of 168) from humans contained genes coding for LT-II. Genes coding for LT-II were not found in 50 LT-I-producing and heat-stable enterotoxin-producing E. coli isolates from 11 children with diarrhea and 44 LT-nonproducing and heat-stable enterotoxin-producing E. coli isolates from 12 other children with diarrhea. A total of 9% of LT-II-producing E. coli isolates (3 of 34) from cows and buffalo hybridized with DNA probes for genes coding for verocytotoxin 2 (VT2), and 18% (6 of 34) hybridized with a DNA probe coding for enterohemorrhagic E. coli (EHEC) adhesin fimbriae. E. coli SA-53, the original isolate in which LT-II was found, contained genes coding for VT2 and EHEC adhesin fimbriae. Five VT-producing, LT-II-producing E. coli isolates that hybridized with the EHEC probe did not contain DNA sequences coding for VT1 or VT2. LT-II-producing E. coli strains were frequently isolated from cattle and buffalo but were rarely isolated from humans.

Animals↗
PubMed1988

Influence of strain characteristics and immunity on the epidemiology of Campylobacter infections in Thailand.

To determine how strain differences and immunity affect the clinical expression of Campylobacter infections, we conducted a study of acute diarrheal disease in Thailand in which specimens from children with Campylobacter infections were cultured weekly for up to 12 weeks to determine the serotype-specific length of time of convalescent-phase excretion and rate of reinfection. Levels of immunoglobulin G to cell-surface antigens of C. jejuni were determined in another population of healthy children who were closely related by age and location to the children in the diarrheal disease study. Campylobacter species were initially isolated from 18% of 586 children under 5 years old with diarrhea; most isolates in Thailand belonged to serotypes commonly found in developed countries. C. coli was significantly less often associated with symptomatic infections and with bloody diarrhea than C. jejuni (P less than 0.001 and P = 0.045, respectively). The peak age of isolation and the peak level of immunoglobulin G to Campylobacter species occurred before 2 years of age. The mean duration of convalescent-phase excretion was 14 +/- 2 (standard error of the mean) days for children less than 1 year old and 8 +/- 2 days for children 1 to 5 years old (P = 0.02, t test). Infection with another Campylobacter serotype was found in 34% of 105 children during the 12-week follow-up period. The rate of reinfection in these children was 15% (range, 8 to 22%) each week. Hyperendemic exposure to Campylobacter species in Thailand confers immunity to infection that is associated with an early peak in specific serum antibodies and an age-related decrease in the case-to-infection ratio and duration of convalescent-phase excretion but does not prevent asymptomatic infections.

Age Factors↗
PubMed1988

Clinical and microbiologic features of Shigella and enteroinvasive Escherichia coli infections detected by DNA hybridization.

To determine the clinical and microbiologic features of Shigella and enteroinvasive Escherichia coli (EIEC) infections, we investigated 410 children with diarrhea and 410 control children without diarrhea who were seen at Children's Hospital, Bangkok, Thailand, from January to June 1985. Shigella spp. were isolated from 96 (23%) and EIEC were isolated from 17 (4%) of 410 children with diarrhea and from 12 (3%) and 6 (1%) of 410 control children, respectively. The isolation rates of both pathogens increased with age and peaked in children 3 to 5 years old from whom Shigella spp. were isolated from 38% and EIEC were isolated from 9%. Shigella spp. were isolated from 52% and EIEC were isolated from 7% of 91 children with bloody diarrhea and from 15 and 3% of 319 children with nonbloody diarrhea. Fifteen (65%) of 23 EIEC were lactose positive, and all belonged to recognized EIEC serotypes. Among children with diarrhea, the stool blots of 76% of 17 children infected with EIEC, 45% of 96 children infected with Shigella spp., and 1% of 297 culture-negative children hybridized with the 17-kilobase EcoRI digestion fragment of pRM17, a recombinant plasmid containing DNA derived from the 140-megadalton Shigella flexneri plasmid. Although EIEC colonies can be reliably detected by DNA hybridization, detection by stool blot is less sensitive. Shigella spp. and EIEC are important causes of endemic diarrhea among children greater than 1 year old in Thailand.

Age Factors↗
PubMed1988

Incidence of enteric adenoviruses among children in Thailand and the significance of these viruses in gastroenteritis.

In countries with temperate climates, enteric adenoviruses have been shown to be a substantial cause of pediatric gastroenteritis. To determine the incidence of adenovirus infection in a tropical climate, stools were collected from children under age 7 during a 1-year period at an outpatient clinic in Bangkok, Thailand. Stools from 1,114 children with gastroenteritis and from 947 children without gastroenteritis were tested. Each stool was tested for adenovirus group antigen and for specific enteric adenovirus types (Ad40 and Ad41) by monoclonal antibody enzyme immunoassays. We found that 4.4% (49 of 1,114) of children with gastroenteritis and 1.8% (17 of 947) of children without gastroenteritis were positive for adenovirus group antigen. In tests for specific enteric adenovirus types, 2.0% (22 of 1,114) of the tests were positive in children with gastroenteritis and 0.6% (6 of 947) were positive in children without gastroenteritis. There was a significant correlation (P less than 0.02) of gastroenteritis with nonenteric adenovirus types (27 of 1,114) as well as with specific enteric adenovirus types (P less than 0.01). By comparison, 19.7% of children with gastroenteritis and 0.7% of those without gastroenteritis were positive for rotavirus infection. In the adenovirus-infected children with gastroenteritis, there were coinfections with rotavirus only in those with nonenteric adenovirus infection (7 of 27 children). There were no significant differences in the association of bacterial or parasitic infections with either enteric or nonenteric adenovirus infections in either group of children studied. These data demonstrate that Ad40 and Ad41 are causes of gastroenteritis in this population, but among the spectrum of diarrheal etiologies, they may be proportionately less important than they are in countries with temperate climates.

Adenoviridae Infections↗
PubMed1988

A comparative field study of radiolabeled and enzyme-conjugated synthetic DNA probes for the diagnosis of falciparum malaria.

Synthetic, 21-base, DNA probes to the genome of Plasmodium falciparum were either 32P-labeled or enzyme-conjugated for comparative field studies. The sensitivity of both probes was compared with microscopy in the examination of blood samples from 97 Thai villagers, 47 Thai Rangers, and 19 malaria-free Bangkok residents. The probes were also used to monitor the therapeutic response of 18 of the Rangers during 7 days of treatment. The probes proved highly specific. Both probes had lower limits of detection of about 100 parasites per microliter blood. Thus, the low parasite densities in partially immune villagers from an endemic area were often missed, while higher parasite densities in the nonimmune Rangers were usually detected. As monitors of response to treatment, the probes paralleled microscopy in identifying reversion from positive to negative parasitemia. The enzymelabeled DNA probe as shown to perform similarly to the radiolabeled probe in populations with different malarial immune status and during curative treatment.

Alkaline Phosphatase↗
PubMed1988

Foods as a source of enteropathogens causing childhood diarrhea in Thailand.

Foods obtained in markets in Bangkok were cultured for bacterial enteric pathogens and examined for their similarity to strains isolated from children under 5 years of age in Bangkok in 1986. Salmonella was isolated from 17%, Campylobacter from 12%, and enterotoxigenic Escherichia coli (ETEC) from 3% of 510 foods examined. Campylobacter was isolated from 13.5%, ETEC from 13%, and Salmonella from 12% of 1,230 children under 5 years of age with diarrhea. Eighty-eight percent of children infected with Salmonella were infected with serotypes isolated from foods of animal origin. Six percent of children with Salmonella were infected with the same serotype containing plasmids with identical endonuclease restriction patterns as isolates from food. Eighty-seven percent of children with Campylobacter were infected with the same serotypes and biotypes found in food of animal origin. Thirty-one percent of heat-labile enterotoxin (LT) producing ETEC from foods containing genes coding for LT II, but LT II ETEC was not isolated from children. Twenty-one percent of ETEC isolated from foods vs. 53% isolated from children were resistant to 2 or more antibiotics (P less than 0.01). Salmonella and Campylobacter, but not ETEC, isolated from foods were similar to strains isolated from children. Foods of animal origin are an important source of Salmonella and Campylobacter in Thailand.

Animals↗
PubMed1987

Enteritis necroticans among Khmer children at an evacuation site in Thailand.

A severe illness characterised by bloody diarrhoea and intestinal dysfunction was recognised at an evacuation site on the Thai-Kampuchean border. From June, 1985, to July, 1986, the illness occurred in 62 Khmer children aged 10 months to 10 years (mean 4 years); it was characterised by bloody diarrhoea (94%), fever (90%), and abdominal pain (78%). The overall mortality rate was 58%. Among 16 children who died and underwent necropsy, small-intestinal necrosis of varying severity was found; in 5 of these children small-intestinal lesions with areas of full-thickness necrosis were seen that histologically resembled those in cases of enteritis necroticans (pigbel) in Papua New Guinea. Beta-toxin-producing Clostridium perfringens type C was isolated from 2 of 23 children from whom specimens for anaerobic cultures were collected, and antibodies to beta toxin were detected in 5 of 9 survivors but not in 10 healthy, age-matched control children. These cases show that enteritis necroticans can cause substantial morbidity and mortality outside Papua New Guinea.

Adult↗