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Biomedical subjects

S K Sethi

Publications and source records attributed to S K Sethi.

At least 19 recordsLinked to original sources
PubMed1995

Analysis of polycyclic aromatic hydrocarbons in metered dose inhaler drug formulations by isotope dilution gas chromatography/mass spectrometry.

Organic compounds extracted into metered dose inhalers (MDIs) from the rubber components of the metering valve are of increasing interest in the development of these formulations. Polycyclic aromatic hydrocarbons (PAHs) are a class of extractable organic compounds whose source is the carbon black commonly used as a reinforcing agent in rubber. The analytical method for PAHs described in this report employs "cold filtration" to remove the suspended drug substance and excipients, and gas chromatography/mass spectrometry (GC/MS) for separation and detection of individual PAHs. After filtration, stable isotope labelled analogues of target PAHs are spiked into the drug product to act as internal standards, correcting for recovery (termed "isotope dilution GC/MS"). Validation of the method was accomplished with respect to linearity, precision, limit of detection/quantitation, selectivity and ruggedness. Application to a variety of MDI drug product formulations revealed that certain PAHs are present at the ng/inhaler level.

Gas Chromatography-Mass Spectrometry↗
PubMed1990

Use of an alkaline phosphatase-labeled synthetic oligonucleotide probe for detection of Campylobacter jejuni and Campylobacter coli.

A commercially available synthetic nucleic acid probe (SNAP) conjugated to alkaline phosphatase was compared with standard culture techniques for detecting Campylobacter species. The SNAP was able to detect either 5 ng of C. jejuni DNA or 10(5) CFU of bacteria. The SNAP could also detect DNA extracted from 10(5) CFU in mock-infected stool samples. The SNAP detected C. jejuni and C. coli but showed no reactivity with C. laridis, C. fetus subsp. fetus, C. fetus subsp. venerealis, C. fennelliae, "C. upsaliensis," C. cinaedii, C. fecalis, C. hyointestinalis, C. mucosalis, or Helicobacter (Campylobacter) pylori. The SNAP also showed no cross-reactivity with other enteric pathogens. When applied to pure cultures, the SNAP detected 55 clinical isolates of C. jejuni and 11 clinical isolates of C. coli, with an accuracy of 100%. When applied directly to clinical specimens, the SNAP detected Campylobacter spp. in 19 of 23 culture-positive stool specimens (sensitivity, 82.6%; specificity, 100%). Pure cultures of the Campylobacter strains isolated from the four probe-negative, culture-positive stool specimens gave positive reactions with the SNAP. While the SNAP had excellent sensitivity and specificity for isolated bacterial colony isolates, the main limitation to the Campylobacter probe detection kit may be the sensitivity limit on direct detection of Campylobacter organisms in stools.

Alkaline Phosphatase↗
PubMed1989

Outbreak of neonatal listeriosis in a regional hospital in Kuwait.

Six newborns with Listeria monocytogenes infection were admitted to the same neonatal unit between 31 October and 3 December 1985. The index case, a preterm baby, was born to a mother who was febrile with an influenza-like illness at the time of delivery. This baby presented with Listeria sepsis and pneumonia. Another child was born from whose mother L. monocytogenes was isolated from the cervix with the same serotype as that in the CSF of her newborn. In the other cases blood and cervical cultures of the mothers were negative, while Listeria was isolated from the CSF of their babies. Five out of six infants developed meningitis between 9 and 12 days after birth. All isolates were serotype 4b and indistinguishable by phage typing. All babies were successfully treated without any major sequelae. Although cross-infection was strongly suggested, the source of the outbreak could not be established. This is the first documented report of human listeriosis in Kuwait.

Cross Infection↗
PubMed1989

Microbial etiology of acute gastroenteritis in hospitalized children in Kuwait.

During a period of 15 months 621 hospitalized children with acute gastroenteritis and 152 control children were investigated for etiologic agents of the disease. Putative enteropathogens were identified in 86% of the patients and 10% of the controls. Common viral agents associated with gastroenteritis among children included rotaviruses (45%) and enteric adenoviruses (4%). Bacterial pathogens infecting children were Salmonella serotypes (24%), enterotoxigenic Escherichia coli (9%), Campylobacter jejuni (7%), enteropathogenic E. coli (7%), Shigella (4%) and enterotoxigenic Aeromonas sp. (1%). The highest incidence of infections was observed in the 3- to 25-month age group. Mixed infections were observed in 12% of the patients. Viral gastroenteritis was clinically mild and of short duration. Upper respiratory tract infections, vomiting and watery stools were common features. In contrast bacterial gastroenteritis was more severe; stools were frequently bloody and abdominal pain, cramps, shock, convulsions and milk intolerance were predominant clinical features. Comparative analysis revealed differential features of bacterial and viral gastroenteritis which should help clinicians to make a tentative diagnosis and to start treatment early.

Acute Disease↗
PubMed1989

Detection of human rotavirus by using an alkaline phosphatase-conjugated synthetic DNA probe in comparison with enzyme-linked immunoassay and polyacrylamide gel analysis.

An alkaline phosphatase-conjugated synthetic oligodeoxyribonucleotide probe was compared with polyacrylamide gel electrophoresis (PAGE) detection of rotavirus RNA as well as an enzyme-linked immunosorbent assay (ELISA) for the detection of rotavirus in stools from young children with gastroenteritis. The synthetic probe did not cross-react with bacterial causative agents of diarrheal disease. Extraction of viral RNA from stool samples with a phenol-chloroform mixture was suitable for most samples. In some cases fecal pigments interfered with the reaction of the probe with viral RNA. The use of ion-exchange chromatography to further purify viral RNA removed contaminating pigments and increased the sensitivity of the probe assay. Of 260 stool specimens, 77 (30%) were positive for rotavirus when tested by PAGE analysis of rotavirus RNA. The synthetic probe identified 71 rotavirus specimens when RNA obtained by phenol-chloroform extraction followed by chromatographic purification was used (sensitivity, 91.0%; specificity, 96.7%). The ELISA results also agreed well with the electrophoretic analysis (sensitivity, 98.7%; specificity 94%) and the probe assay (sensitivity, 90%; specificity, 100%). Discordant results between the ELISA and the probe assay were examined further by electron microscopy and PAGE analysis of viral RNA. The positive and negative predictive values of the probe assay in comparison with PAGE were 92.2 and 96.1%, respectively. Rotaviruses showing both long and short RNA electrophoretic patterns were detected by the probe. The probe assay coupled with chromatographic purification of rotavirus RNA is an effective method for detecting rotavirus and compares favorably with PAGE analysis and ELISA.

Acute Disease↗
PubMed1988

Molecular epidemiology of human rotavirus infections based on genome segment variations in viral strains.

Molecular epidemiology of rotavirus infections in 621 hospitalized children was investigated by analysis of migration patterns of viral genomic ribonucleic acid (RNA) segments by electrophoresis in polyacrylamide gels. Based on migration patterns of RNA segments of 184 rotavirus strains, seven different electropherotypes were identified: 146 (79.3%) strains were "long," and 38 (20.7%) were "short" electropherotypes; 61% belonged to a single dominant "long" electropherotype, which persisted throughout the 15-month period of study, whereas six other cocirculating types appeared at varying intervals. Electrophoretic migration patterns of RNA from viral isolates of two patients suggested mixed infections with different rotaviruses. There was a lack of correlation between the electrophoretic migration of segments 10 and 11 and serologically defined subgroup specificity in three of the rotavirus strains. Rotavirus infections and different electropherotypes were observed throughout the year.

Child, Preschool↗
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↗