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Biomedical subjects

S K Sethi

Publications and source records attributed to S K Sethi.

At least 37 records · Page 2Linked to original sources
PubMed1988

Identification of enterotoxigenic Escherichia coli using alkaline phosphatase-labeled synthetic oligodeoxyribonucleotide probes.

Alkaline phosphatase-conjugated synthetic oligodeoxyribonucleic acid probes were used to detect enterotoxigenic Escherichia coli strains containing either the heat stable or heat labile toxin genes. Both of the synthetic probes detected as little as 5 ng of purified plasmid DNA bearing the appropriate toxin gene. In addition, both probes could detect 5 X 10(6) toxigenic bacteria by colony hybridisation. No cross reactivity was observed between probes. When 197 clinical isolates of Escherichia coli were examined for toxigenicity using bioassays, 13 heat stable and 17 heat labile toxin strains were identified. Of the 13 heat stable toxin strains, 12 were positive using the heat stable toxin synthetic probe (sensitivity, 92%; specificity, 98%) while 16 of 17 bioassay heat labile toxin positive samples were identified using the heat labile toxin synthetic probe (sensitivity, 94%; specificity, 97%). Alkaline phosphatase-conjugated synthetic probes with high sensitivity and specificity should provide a rapid means of identifying toxigenic Escherichia coli.

Alkaline Phosphatase↗
PubMed1988

Acute gastroenteritis: clinical features according to etiologic agents.

The clinical manifestations in 595 children hospitalized with gastroenteritis during a 15-month time frame were studied. They were divided into eight groups according to etiologic agent: rotavirus (203 patients); Salmonellae (98); Escherichia coli (55); Campylobacter (36); Shigella (22); combined rotavirus and salmonellae (44); combined rotavirus and other bacteria (26); and no pathogen (111). The mean duration of diarrhea was shortest in the rotavirus and "no pathogen" groups (4.8 and 5.6 days, respectively) and longest with pure and mixed salmonella infections (12.3 and 12.9 days, respectively). Associated manifestations were most frequent with salmonellae and least frequent with rotavirus and E. coli infections. Malnutrition also was most common with salmonellae and lowest with rotavirus and E. coli. There were no differences in the frequency of hypernatremia. Hyponatremia was most frequently encountered with salmonella (25% compared to 9% in the rest of the patients). Evidence of septicemia was found in 22 patients, 21 of whom were in the salmonella groups. The four deaths in this series (0.7%) also were in the salmonellae groups. The clinical severity of salmonella infection in developing countries, particularly in young and malnourished children, warrants attention to more intensive management. The selective use of antibiotics may help reduce the mortality and morbidity of gastroenteritis.

Anti-Bacterial Agents↗
PubMed1987

Detection of Shiga-like (SL) toxins of enteropathogenic Escherichia coli (EPEC) of human, porcine, calf, and lamb origin on Vero and HeLa S3 cells: a comparative study.

One hundred and forty eight strains of human, porcine, calf and lamb origin belonging to different enteropathogenic O:H serotypes isolated in 13 countries in four continents were tested for production of Shiga, Shiga-like (SL) and other cytotoxins on Vero cells and HeLa (S3 subline) cells in tissue cultures. Altogether, 45% human strains and 89% porcine strains were defined as strong toxin producers (toxin titre greater than or equal to 1:100) on Vero or HeLa S3 cells while 31% of human and 9% porcine strains were regarded as moderate to weak toxin producers (toxin titre less than 1:100). Twenty three percent of human and 1.5% of porcine strains were negative for Shiga or SL-toxin. Polymyxin release of Shiga or SL toxins from bacterial colonies of blood agar grown cultures is recommended as it is simple and effective method facilitating the detection of even low levels of toxins in EPEC or non-EPEC strains. Of the ten strains from calves and lambs, only four were strong toxin producers when cell-free culture supernatants were tested while a polymyxin release method showed that 8 strains were strong toxin producers. One strain was negative by both methods. The high proportion of Shiga/SL toxin negative strains in all O:H serotypes of human origin (but not of porcine origin, especially O 139 serogroup) suggests that systematic studies should continue to look for new toxins in freshly isolated strains grown under in vivo like conditions, e.g. in iron depleted culture media.

Animals↗
PubMed1986

Non-haemagglutinating fimbriae of enteropathogenic Escherichia coli (EPEC).

Two hundred and thirteen Escherichia coli strains originating in 12 countries were included in the study. Of these, 157 were classical enteropathogenic E. coli (EPEC) serotypes, 54 belonged to O138, O139 and O141 serogroups i.e. porcine edema disease strains and two strains were of serogroup O157 associated with haemorrhagic colitis. Surface hydrophobicity was determined by the salt aggregation test (SAT). Haemagglutination was assayed against erythrocytes of six animal species with strains grown under conditions known to promote expression of haemagglutinins. Sixty three EPEC strains were hydrophobic i.e. SAT value less than or equal to 0.1-1.6, and of these 15 did not haemagglutinate. Fimbriae were abundant on non-haemagglutinating strain 2178/58 (O26) when grown in nutrient broth. Fewer fimbriae per cell were present after growth on nutrient agar. Heat- and protease treatment reduces the surface hydrophobicity of EPEC strains. We propose that EPEC strains may carry a number of different surface proteins which determine binding to intestinal cells in a similar way as hydrophobic non-haemagglutinating fimbriae determine binding to rabbit intestinal brush borders, cf rabbit EPEC strain RDEC 1.

Animals↗
PubMed1986

Analysis of mutagens from cooked foods by directly combined liquid chromatography-mass spectrometry.

Directly combined high performance liquid chromatography-mass spectrometry (LC/MS) has been studied as a method of analysis of heterocyclic aromatic mutagens in cooked foods, in the parts per billion concentration range. Identification and semiquantitative estimation of mutagens is based on accurate measurement of chromatographic retention (k') and molecular weight-selective detection of mutagens, which are protonated during passage of the chromatographic eluant into a thermospray interface of a quadrupole mass spectrometer. Standard chromatographic retention (k') values in two reversed-phase systems and data from thermospray mass spectra from nine mutagens are reported. An isolation scheme employing CH3OH extraction, acid-base partition, cellulose-trisulfo-Cu-phthalocyanine adsorption, and normal-phase HPLC was used prior to LC/MS analysis. Initial applications have been demonstrated in the analysis of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) in broiled salmon flesh. Levels measured were estimated to be in the range 0.2 to 0.4 microgram/kg IQ and 0.4 to 0.9 microgram/kg MeIQ. The method is judged to be generally applicable with minimal sample prefractionation to detection of mutagens at the parts per billion level in cooked foods.

Animals↗
PubMed1985

Septicaemia in a teaching hospital in Kuwait--I: Incidence and aetiology.

During a period of 18 months of study, blood cultures were performed on 3845 patients in hospital with clinical signs of infection. Among these, 214 (5.6%) episodes of septicaemia were diagnosed which correspond to 10.9/1000 hospital admissions. About 80% of the episodes were due to Gram-negative organisms, most common of which were Escherichia coli (19.6%), Salmonella spp (16.5%) and Klebsiella spp (15.1%). Gram-positive organisms implicated in 20% of episodes were mainly Staphylococcus aureus (9.3%) and enterococci (4.9%). Of all the septicaemias 62.0% were community-acquired with Salmonella spp. being the organism most commonly implicated. Hospital-acquired infections were mainly due to Serratia spp, Pseudomonas spp and Flavobacterium spp. The antibiotic resistance pattern of the organisms showed that hospital-acquired organisms had relatively high resistance to most antibiotics as compared with community-acquired organisms.

Cross Infection↗
PubMed1985

Isolation and characterization of a novel nucleoside, 7-beta-D-ribofuranosylhypoxanthine, from the urine of a chronic myelogenous leukemia patient.

A novel nucleoside, in the amount of 400 micrograms, was isolated from a 24-h collection of urine of a chronic myelogenous leukemia patient. On the basis of ultraviolet, nuclear magnetic resonance, and mass spectrometry and chromatography, its structure was established to be 7-beta-D-ribofuranosylhypoxanthine. The ultraviolet and mass spectral data and the thin layer chromatographic mobilities of the natural material were identical to those of a synthetic sample. High performance liquid chromatographic retention times and the coinjection high performance liquid chromatography of the natural material with the synthetic samples of the alpha and beta-anomers of 7-ribofuranosylhypoxanthines further confirmed the identity of the isolated material as 7-beta-D-ribofuranosylhypoxanthine.

Adult↗
PubMed1984

The photochemistry of d(T-A) in aqueous solution and in ice.

When d(T-A) is irradiated at 254 nm in aqueous solution an internal photoadduct is formed between its constituent adenine and thymine bases. The resultant photoproduct, designated TA*, arises from a singlet excited state precursor; a similar photoreaction is not observed with d(C-A) or d(T-G). In contradistinction, irradiation of d(T-A) in frozen aqueous solution yields a dimeric photoproduct in which two d(T-A) molecules are coupled together by a (6-4) photoadduct linkage between their respective thymine bases. Both photoproducts have been extensively characterised by a combination of electron impact and fast atom bombardment mass spectrometry, UV, CD, 1H NMR and fluorescence spectroscopy. Acid treatment of TA* gives 6-methylimidazo[4,5-b]pyridin-5-one whose identity was established by an independent chemical synthesis involving photorearrangement of 6-methyl-imidazo[4,5-b]pyridine N(4)-oxide. A tentative mechanism is presented to account for the acid degradation of TA*. The structure of the dimeric ice photoproduct follows from its cleavage, by snake venom phosphodiesterase, to 5'-dAMP and the (6-4) bimolecular photoadduct of thymidine; on acid hydrolysis it gives adenine and 6-(5'-methyl-2'-oxopyrimidin-4'-yl) thymine.

Circular Dichroism↗
PubMed1984

Pseudoreplica electron microscopy for the detection of rotavirus: comparison with high-speed centrifugation electron microscopy and ELISA.

Three-hundred and sixty-three stool specimens from patients with diarrhoea were examined for rotaviruses to compare the sensitivity of the pseudoreplica technique (PSD-EM) to that of high-speed centrifugation EM (HSC-EM) in relation to a commercially available (Rotazyme, Abbott) enzyme-linked immunosorbent assay (ELISA). In ELISA-positive cases, both methods were of equal sensitivity. However, in borderline (+/-) and ELISA-negative specimens, PSD-EM detected 31 of 48 (64.6%) and 18 of 229 (8%) positive specimens respectively, compared to only 22 of 48 (45.8%) and one of 229 (0.4%) positives detected by HSC-EM. PSD-EM detected a significantly higher number of positives compared to HSC-EM (p less than 0.05). In view of its simplicity, sensitivity and the fact that a relatively large number of specimens could be processed compared to HSC-EM, we consider that PSD-EM is a much better procedure for routine screening and diagnosis of viral gastroenteritis than HSC-EM.

Centrifugation↗
PubMed1984

Acute diarrhoea and rotavirus infections in young children in Kuwait.

The role of rotavirus infections in acute diarrhoea in young children was studied over a period of one year. Rotavirus was detected by electron microscopy and enzyme immunoassay methods in 40.2% of faecal specimens from 343 children with acute diarrhoea and in 4.7% of 86 controls. The infections were most common in children aged 2-12 months (42.3%). Twelve per cent of the rotavirus infected children were also infected with bacterial enteropathogens (Salmonellae, Shigellae and enteropathogenic Escherichia coli). The incidence of rotavirus infections was not related to sex, socio-economic or nutritional status of children. Rotavirus-associated diarrhoea differed in several clinical parameters from bacterial associated and nonspecific diarrhoea. Rotavirus was detected throughout the year but was most frequent during months with little rainfall and low humidity (March-May). Our results suggest that in Kuwait, rotavirus infection is a major cause of childhood diarrhoea.

Acute Disease↗
PubMed1984

Structure and biological activity of ascamycin, a new nucleoside antibiotic.

A newly isolated strain of Streptomyces sp. produces a new nucleoside antibiotic, ascamycin and the corresponding dealanyl derivative. The structure of ascamycin was determined to be 2-chloro-9-beta-[5-O-(N-L-alanyl)sulfamoyl-D-ribofuranosyl]-adenine. Remarkable selective toxicity of ascamycin compared to the dealanyl derivative was accounted for on the basis of a dealanylating enzyme present in the envelope of sensitive bacteria. After dealanylation, it becomes permeable to cell membrane.

Adenosine↗
PubMed1983

Formation of an adenine-thymine photoadduct in the deoxydinucleoside monophosphate d(TpA) and in DNA.

A photoadduct is formed between the adenine (A) and thymine (T) bases of the deoxydinucleoside monophosphate d(TpA) when it is irradiated at 254 nanometers in aqueous solution. Treatment of the photoadduct with acid converts it specifically into a fluorescent hydrolysis product, C7H7N3O, incorporating the position-8 carbon of adenine and the methyl group of thymine. Isolation of the fluorescent hydrolysis product from acid hydrolyzates of oligo- and polydeoxyribonucleotides has shown that the photoadduct is formed by ultraviolet irradiation of d(pTpA), d(TpApT), d(TpApTpA), poly(dA-dT), and both single- and double-stranded DNA.

Adenine↗
PubMed1983

Determination of active hydrogen content by fast atom bombardment mass spectrometry following hydrogen-deuterium exchange.

Fast atom bombardment mass spectrometry following hydrogen--deuterium exchange in [hydroxy-2H3]glycerol and 2H20 has been studied as a means of establishing active hydrogen content in molecules of unknown structure. Nucleotides, carbohydrates, one peptide and complex antibiotics, in the mass region to 1500 daltons and 29 exchangeable hydrogens were examined, with a correct hydrogen count unambiguously measured in every case. The method is experimentally simple and applicable on a microgram scale, to salts and a variety of polar compounds of biological origin.

Anti-Bacterial Agents↗
PubMed1982

A naturally occurring pyrimidodiazepine in Drosophila: chemical and spectral properties and relationship to drosopterin.

The structure of an intermediate, in drosopterin biosynthesis, as 6-acetylpyrimidodiazepine has been confirmed by high-resolution mass spectra, 13C NMR, chemical ionization mass spectra, and chemical properties. A trivial name of 6-acetylhomopterin is suggested and should replace the term "quench spot" used heretofore. The structure of drosopterin includes, in part, a pyrimidodiazepine, a compound that consists of a fused six- and seven-membered heterocyclic ring system. Earlier studies demonstrated that 6-acetylhomopterin strongly stimulated the enzymatic synthesis of drosopterin and related eye pigments by preparations from Drosophila. The occurrence in nature is quite limited for diazepines; drosopterin and homopterin are the first examples in eukaryotes.

Animals↗
PubMed1982

Gastroenteritis in a regional hospital in Kuwait: some aspects of the disease.

A review of the clinical course of gastroenteritis in 274 hospitalized children revealed a severe form of the disease. Eight-eight per cent were aged 12 months or under and 20% had severe associated malnutrition. The commonest clinical manifestations were diarrhoea (100%), dehydration (98.9%), vomiting (81.4%) and fever (77.7%). Pathogens were isolated from 75.2% of cases (rotavirus 24.5%, Escherichia coli 20.8%, salmonellae 20%, shigellae 6.2%, campylobacter 2.2% and Yersinia enterocolitica in 1.5%). Septicaemia was confirmed in 12 patients (4.4%) and strong clinical evidence of septicaemia was present in 36 more cases (13%). Dehydration was isonatraemic in 68%, hyponatraemic in 21% and hypernatraemic in 11% of cases. There was a clear association between septicaemia and hyponatraemia. The overall mortality rate was 1.8%. Data from our study show that the use of intravenous hyperalimentation, and/or antibiotics in the management of gastroenteritis in selected patients, can significantly reduce morbidity and mortality.

Anti-Bacterial Agents↗