Biomedical subjects

K Alam

Publications and source records attributed to K Alam.

At least 55 records · Page 3Linked to original sources

PubMed1993

Role of Shigella dysenteriae type 1 slime polysaccharide in resistance to serum killing and phagocytosis.

Shigella dysenteriae type 1 produce a slime polysaccharide when cultivated in vivo in adult rabbit ileal loops or in vitro in casamino acid yeast extract broth medium which promotes hemagglutination of these bacteria. Seven strains of S. dysenteriae 1 grown in vitro and in vivo and possessing slime polysaccharides resisted killing by normal human serum as compared to bacteria grown under conditions which do not stimulate the production of capsular polysaccharide and did not resist serum killing (mean survival 72% for in vitro growth and 73% for in vivo growth conditions favoring capsule production vs < 2% for growth conditions which do not favor capsule production; P < 0.001 for both comparisons). Similar differences were observed when killing was assessed by phagocytosis (62-78% vs < 2%; P < 0.001). We conclude that capsular polysaccharide may be an additional virulence factor of S. dysenteriae 1.

Animals↗

PubMed1992

DNA probe analysis of diarrhoeagenic Escherichia coli: detection of EAF-positive isolates of traditional enteropathogenic E. coli serotypes among Bangladeshi paediatric diarrhoea patients.

Escherichia coli isolates from all surveillance patients less than or equal to 20 months of age seen for diarrhoea at the Dhaka Clinical Treatment Facility of the International Centre for Diarrhoeal Disease Research, Bangladesh between March 1 and August 31, 1988, were collected and hybridized with DNA probes to assess the potential importance of diarrhoeagenic E. coli among paediatric patients in Bangladesh. Of 396 patients evaluated, 18% were infected with enteropathogenic E. coli (EPEC) adherence factor (EAF)-positive E. coli, 23% were infected with enterotoxigenic E. coli (ETEC), 9% were infected with Shiga-like toxin-positive E. coli, and 13% were infected with diffuse adhesiveness-positive E. coli. None were infected with enteroinvasive E. coli. Ten percent of patients were colonized with more than one type of potential diarrhoeagenic E. coli. The majority of EAF-positive isolates were of traditional EPEC O:H serotypes. Although this was not a case-control study, the large number of EPEC and ETEC, which are recognized enteric pathogens, suggests these organisms are important causes of diarrhoeal diseases in this pediatric population.

Bangladesh↗

PubMed1992

Sharing of virulence-associated properties at the phenotypic and genetic levels between enteropathogenic Escherichia coli and Hafnia alvei.

Seven strains of Hafnia alvei isolated from diarrhoeal stools of children resembled enteropathogenic Escherichia coli (EPEC) in that they produced attaching-effacing (AE) lesions in rabbit ileal loops and fluorescent actin staining in infected HEp-2 cells. In addition, a DNA probe from a chromosomal gene required by EPEC to produce AE lesions, hybridised to chromosomal DNA from all seven H. alvei strains. These findings indicate that there is a sharing of virulence-associated properties at the phenotypic and genetic levels by H. alvei and EPEC. H. alvei strains with these properties should be considered diarrhoeagenic.

Bacterial Adhesion↗

PubMed1992

Naturally occurring SLE anti-DNA antibodies recognize unique conformation on DNA-lysine photoadduct.

Native calf thymus DNA has been covalently modified with lysine under UV-A light. Human autoantibodies on purification through affinity column of native DNA linked to polylysyl-Sepharose 4B showed almost equal recognition of DNA and photoadduct. The recognition of DNA-lysine photoadduct by the affinity-purified autoantibodies might be helpful in understanding their origin in SLE vis-à-vis the role of positively charged amino acids in the pathogenesis of autoimmune diseases.

Animals↗

PubMed1992

Pathogenesis of Providencia alcalifaciens-induced diarrhea.

Providencia alcalifaciens is a member of the family Enterobacteriaceae. There are reports that P. alcalifaciens can cause diarrhea, but the mechanism(s) by which it causes diarrhea is known. We studied P. alcalifaciens isolated from a child and two adults with diarrhea for enteropathogenicity. The three isolates did not exhibit any characteristic adherence to cultured HEp-2 cell monolayers, and they did not produce enterotoxins, cytotoxins, or keratoconjunctivitis in the Sereny test. Two isolates invaded cultured HEp-2 cell monolayers, producing localized bacterial clusters and actin condensation. The pattern of actin condensation was different from that produced by enteropathogenic Escherichia coli but similar to that produced by Shigella flexneri. Invasion and actin condensation were poor for the third isolate. Histology of adult rabbit small intestinal loops inoculated with all three isolates revealed bacterial attachment to, penetration of, and microulcer formation on the surface epithelium and hyperemia, edema, and polymorphonuclear cell infiltration of lamina propria. All the isolates produced diarrhea in rabbits with removable intestinal ties, and some of these rabbits developed hindlimb paralysis. Intestinal histology of the rabbits with removable intestinal ties which developed diarrhea showed changes similar to that in adult rabbits on which ileal loop assays had been performed. Transmission electron microscopy of intestinal tissues also confirmed tissue penetration by the isolates. Nerve tissue histology of two rabbits that developed hindlimb paralysis showed focal mononuclear cell infiltration around peripheral nerve sheaths. It is concluded that some strains of P. alcalifaciens are enteropathogenic and that they cause diarrhea by invading the intestinal mucosal epithelium. However, the relevance to human disease of the hindlimb paralysis observed in this animal model is not clear.

Animals↗

PubMed1992

Characterization of Aeromonas caviae antigens which cross-react with Shigella boydii 5.

Live and boiled cells of 16 strains of Aeromonas caviae, isolated from patients with diarrhea, agglutinated with Shigella boydii 5 antiserum in a slide test. Further studies with seven selected strains showed agglutination with boiled cells in a tube test. Lipopolysaccharide antigen extracted from one of these strains cross-reacted with S. boydii 5 in enzyme-linked immunosorbent assay and immunoblot studies. Either all or the majority of the seven strains possessed properties deemed to be diarrheagenic.

Aeromonas↗

PubMed1992

Human autoantibody binding to multiple conformations of DNA.

Systemic lupus erythematosus and rheumatoid arthritis in humans are characterized by circulating and tissue fixed autoantibodies reactive with self antigens including nucleic acids and other nuclear components. Native calf thymus DNA (B-form), DNA.RNA hybrid (A-form), and left handed DNA (Z-form) were reactive with autoantibodies derived from SLE sera. Inhibition studies suggest that antibodies are recognizing multiple conformations presented by altogether different polymers and A- or Z-DNA might be the immunogenic stimulus for the production of antibodies cross reactive with native DNA.

Antibodies, Antinuclear↗

PubMed1992

Primary malignant lymphoma of the gastro-intestinal tract: a clinicopathological study of 24 cases.

Twenty-four cases of primary lymphoma of the gastro-intestinal tract were diagnosed during the period 1970 to 1991. There was a preponderance of males and the male to female ratio being 1.4:1. Age ranged from 9-70 years, mean 32.2 years. Small intestine was involved in 50% cases, large bowel in 9 cases (37.5%) and stomach in 3 cases (12.5%). There were 5 cases (20.8%) of Hodgkin's disease and 19 cases (79.2%) were of non-Hodgkin's lymphoma. All cases of gastric lymphoma complained of epigastric pain, weight loss and vomiting. In lymphoma of small intestine, 8 patients complained of pain associated with vomiting and 6 patients complained of distension of abdomen. In large bowel lymphoma, pain in right iliac fossa was complained by 4 patients and bleeding per rectum by 3 patients. Out of all the 24 cases, changes in bowel habit were noted in 15 patients and occult blood was positive in 13 cases. Palpable abdominal mass was noted in 14 patients. Histomorphologically, all the 3 cases in the stomach were of lymphocytic lymphoma diffuse type. Out of 19 non-Hodgkin's lymphoma, 15 were of lymphocytic lymphoma and 4 were of histiocytic lymphoma.

Adolescent↗

PubMed1992

Campylobacter jejuni bacteraemia in children with diarrhoea in Bangladesh: report of six cases.

Campylobacter jejuni was isolated from blood cultures from 6 of 6,275 diarrhoeal children seeking treatment at the Clinical Research Centre of the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B) between April 1989 and December 1990. The clinical records of these 6 children were reviewed. All children were male; 5 were less than 1-year old and were severely malnourished. Five patients presented with watery diarrhoea and one with bloody diarrhoea. Two children died in the hospital. All strains of Campylobacter isolated from the 6 children were negative for cell invasive properties as tested by the Sereny test. Of the two strains tested for serum bactericidal activity, one strain was serum sensitive (growth inhibition), and the other resistant. The ability of C. jejuni to cause bacteraemia suggests that the organisms may be responsible for diarrhoeal diseases especially in young and malnourished children. An early attempt to detect Campylobacter and start effective antimicrobial therapy is indicated.

Bacteremia↗

PubMed1992

Increased density of Helicobacter pylori on antral biopsy is associated with severity of acute and chronic inflammation and likelihood of duodenal ulceration.

An increased risk of ulcers and severity of inflammation with increased degree of Helicobacter pylori (HP) infection (biological gradient) would support the hypothesis that HP causes ulcers. A blinded pathologist evaluated antral biopsies obtained at endoscopy in 903 patients. The level of HP infection was assessed on Warthin Starry stain, and the severity of acute and chronic inflammation on hematoxylin and eosin graded from 0 to 3. The presence of duodenal ulcers was associated with increasing HP density (grade 0, 6%; grade 1, 16%; grade 2, 19%; and grade 3, 27%) (p less than 0.0001, Wilcoxon rank sum test). Only a weak association between HP and gastric ulcers was detected (p = 0.06, Wilcoxon rank sum test), and this association diminished after adjusting for other risk factors. An increased acute and chronic inflammatory response correlated with increasing HP concentration (p less than 0.0001, Cochran-Mantel-Haenszel correlation statistic. The presence of this biologic gradient supports the hypothesis that HP is pathogenic in duodenal ulcers and in acute and chronic gastritis.

Acute Disease↗

PubMed1991

Hafnia alvei, a probable cause of diarrhea in humans.

Hafnia alvei, a member of the family Enterobacteriaceae, was the only species of bacteria cultured from the stool of a 9-month-old child who was admitted with a 3-day history of watery diarrhea. The isolated strain of H. alvei failed to produce heat-labile or heat-stable enterotoxins or Shiga-like toxin I or II and did not invade HeLa cells, nor did it cause keratoconjunctivitis (determined by the Sereny test) in a guinea pig's eye. The strain, however, induced diarrhea in 8 of 12 adult rabbits with removable intestinal ties (removable intestinal tie-adult rabbit diarrhea [RITARD] assay) and in 1 of 2 orally fed animals. No diarrhea could be induced with Escherichia coli K-12 in eight RITARD assay rabbits and three orally fed rabbits, respectively. Microscopic examination of affected animals revealed moderate inflammatory cellular infiltration of the intestinal mucosa, in which bacterial attachment to the surface epithelium and loss of the microvillus border were evident in the ileum and colon. Electron microscopy demonstrated cellular modifications of the apical surface, with cupping or pedestal formation and increased terminal web density at sites of bacterial "attachment-effacement," a well-known characteristic and mechanism of diarrhea of enteropathogenic E. coli. Identical lesions were also induced by H. alvei in rabbit ileal loops, which ruled out naturally occurring rabbit enteropathogenic E. coli strains, which are known to produce similar lesions. It is concluded that at least some strains of H. alvei have the potential to cause diarrhea and that attachment-effacement is a virulence characteristic shared by bacteria other than E. coli.

Animals↗

PubMed1991

Localized adherence and attaching-effacing properties of nonenteropathogenic serotypes of Escherichia coli.

Traditional enteropathogenic Escherichia coli serotypes demonstrate a plasmid-mediated localized adherence in cultured HeLa or HEp-2 cells and induce an attaching-effacing intestinal lesion, both of which are considered pathognomonic and causes of diarrhea. This study describes three E. coli strains from infantile diarrhea which share these properties but belong to serotypes (O2:H2, O2:H25 and O15:H2) not considered enteropathogenic.

Animals↗

PubMed1990

Chromatographic enzyme immunoassay for T-2 toxin.

Both the active ester and maleimide moieties of the cross-linking reagent, N-[(gamma-maleimidobutyryl)oxy]succinimide (GMBS), were found to react with the primary amino groups on ribonuclease (RNase). This largely inactivated RNase towards a polymeric (but not monomeric) substrate. Citraconylating the RNase first, so that essentially only a single primary amino group remained to react with GMBS, overcame this problem. The subsequent maleimido-citraconyl-RNase was used to prepare a 1:1.1 M conjugate of anti-T-2 toxin Fab' and RNase (Fab'-RNase) in a 76% yield. The conjugate was used to detect as little as 0.1 microgram of T-2 toxin based on the ability of T-2 toxin to specifically displace Fab'-RNase complexed to a T-2 agarose affinity gel.

Chromatography↗

PubMed1989

Single-dose treatment of cholera with furazolidone or tetracycline in a double-blind randomized trial.

To evaluate single doses of 400 mg of furazolidone and 1 g of tetracycline given orally to patients with diarrhea due to Vibrio cholerae, we studied 87 adults in a randomized, double-blind, placebo-controlled trial. All patients received intravenous fluids for rehydration and no other drugs. The total volumes of stool (mean +/- standard deviation) during a 6-day period after treatment were significantly smaller in the tetracycline group (10.5 +/- 8.6 liters) than in the furazolidone group (20.9 +/- 15.9 liters) and the placebo group (19.1 +/- 10.5 liters) (P less than 0.01). The duration of diarrhea and volumes of intravenous fluids were also significantly reduced in the tetracycline group (P less than 0.05). However, there were no differences between the furazolidone and the placebo groups with regard to stool volume, intravenous fluid, and duration of diarrhea. Within 48 h of treatment, tetracycline significantly reduced the number of patients with positive stool cultures for V. cholerae (37%) compared with furazolidone treatment (96%) and the placebo (97%) (P less than 0.001). Although the tetracycline group had a significantly higher incidence (61%) of bacteriologic relapse (negative stool cultures on days 2 and 3, followed by positive cultures afterward) compared with that in the furazolidone group (40%) and the placebo group (33%), this was not associated with clinical relapse. There were no differences between the furazolidone and placebo groups with regard to any of the bacteriologic responses examined. These data indicate that a single dose of 1 g of tetracycline is effective in the treatment of cholera, but it is asymptomatic bacteriologic relapse. A single dose of 400 mg of furazolidone is not therapeutically effective in cholera.

Adult↗

PubMed1989

Parasitic, bacterial and viral pathogens isolated from diarrhoeal and routine stool specimens of urban Bangladeshi children.

Few data exist in Bangladesh on longitudinal, community-based studies of bacterial or parasitic pathogens identified in routine and diarrhoeal stools of urban dwelling children. We undertook the following study on 343 children of age less than 6 years who resided in one of 51 slum settings in Dhaka, Bangladesh, between October 1984 and February 1986. Specimens from diarrhoeal episodes and from routine stools obtained at 3-monthly intervals were examined for parasites, rotavirus and pathogenic bacteria. Parasites were isolated from 509 (51%) of the 1006 routine stools and from 95 (42%) of the 225 diarrhoeal stools. Isolation rates steadily increased with age. Ascaris lumbricoides and Trichuris trichiura accounted for approximately 80% of all parasitic isolates in routine and diarrhoeal stools. Giardia lamblia was isolated from 11% diarrhoeal stools. Entamoeba histolytica was an uncommon isolate (less than 1%). Bacterial pathogens were identified in 55 (24%) of the diarrhoeal stools but were identified in only 164 (16%) of the 1028 routine stools examined (P less than 0.01). Toxigenic Escherichia coli, Shigellae and Campylobacter were the most frequent isolates from diarrhoeal and routine specimens. This pathogen profile appears to be more in keeping with that from urban settings in other developing countries than from rural Bangladesh, suggesting that extrapolations from rural-based data should not be made for urban settings.

Age Factors↗

PubMed1987

Randomized controlled trial of berberine sulfate therapy for diarrhea due to enterotoxigenic Escherichia coli and Vibrio cholerae.

To evaluate the antisecretory activity of berberine sulfate (BS), we studied 165 adult patients with acute diarrhea due to enterotoxigenic Escherichia coli (ETEC) and Vibrio cholerae in randomized controlled trials. In patients with ETEC diarrhea who received 400 mg of BS in a single oral dose, the mean stool volumes were significantly less than those of the controls during three consecutive 8-hr periods after treatment (P less than .05). At 24 hr after treatment, significantly more patients who were treated with BS and had ETEC diarrhea stopped having diarrhea as compared with the controls (42% vs 20%, P less than .05). In patients with cholera who received 400 mg of BS, the mean 8-hr stool volume during the second 8-hr period after treatment declined to 2.22 liters, which was significantly less than the 2.79 liters found in the controls (P less than .05). However, patients with cholera who received 1200 mg of BS plus tetracycline did not have significant reduction in stool output compared with patients who received tetracycline alone. No side effects of BS were noted. These results indicated that BS is an effective and safe antisecretory drug for ETEC diarrhea, whereas the activity against cholera is slight and not additive with tetracycline.

Adult↗

PubMed1987

Comparison of prophylactic tetracycline and clioquinol in a rabbit model of intestinal infection with Vibrio cholerae and Escherichia coli.

The ability of tetracycline and clioquinol to prevent intestinal colonization of Vibrio cholerae and Escherichia coli was tested in a rabbit model. In the model 10(10) bacteria are given via oro-gastric tube following intravenous cimetidine and oral sodium bicarbonate and prior to intraperitoneal tincture of opium. Eighteen hours after challenge the rabbits are sacrificed, and the numbers of the challenge strain remaining in the jejunum and ileum are determined. Tetracycline interrupted the intestinal colonization of V. cholerae and E. coli. Clioquinol however, had minimal effect on the colonization process. Our studies demonstrate the efficacy of prophylactic tetracycline but do not support the use of clioquinol to prevent intestinal infection due to these organisms. This rabbit model may also be useful to study the efficacy of other antibiotics against these bacterial infections.

Animals↗

PubMed1984

Experimental studies on the pathogenicity of Vibrio mimicus strains isolated in Bangladesh.

Vibrio mimicus, a newly described species of the genus Vibrio has been isolated from stools of 14 patients with diarrhoea. Live cells of all the 14 strains tested caused accumulation of fluid in rabbit gut loops and diarrhoea in infant rabbits. Culture filtrates of all the strains caused increased capillary permeability in rabbit skin; however, five of the filtrates resembled cholera toxin in that they gave positive reactions in rabbit loops, chinese hamster ovarian and mouse adrenal cell monolayers and GM1 ELISA tests and were neutralized by cholera antitoxin. None of the strains produced heat-stable toxin or possessed invasive capability as determined by Sereny's test. Thus, V. mimicus strains were divided into a group which produced a toxin immunobiologically similar to cholera toxin and the rest producing a heat-labile toxin unrelated to that of V. cholerae.

Animals↗