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Biomedical subjects

M J Albert

Publications and source records attributed to M J Albert.

At least 55 records · Page 3Linked to original sources
PubMed1998

Heterogeneity in the organization of the CTX genetic element in strains of Vibrio cholerae O139 Bengal isolated from Calcutta, India and Dhaka, Bangladesh and its possible link to the dissimilar incidence of O139 cholera in the two locales.

After a lapse of 33 months, Vibrio cholerae O139, the new serogroup associated with cholera, has re-emerged in Calcutta, India and has become the dominant serogroup causing cholera from September 1996. In neighbouring Bangladesh, V. cholerae O1 biotype El Tor continues to be the dominant cause of cholera with the O139 serogroup accounting for only a small proportion of cases. Comparison of the phenotypic traits of representative O139 strains from Calcutta and Dhaka isolated between December 1996 and April 1997 showed similar phenotypic traits with the exception that Dhaka O139 strains were susceptible to streptomycin whilst Calcutta O139 strains were resistant. The Dhaka and Calcutta O139 strains displayed identical ribotypes but showed remarkable differences in the structure and organization of the CTX genetic element. In the Dhaka O139 strains, two copies of the CTX element were arranged in tandem and this resembled the pattern displayed by the 1992 epidemic strains of O139. The Calcutta O139 strains, in contrast, carried three copies of the CTX genetic element arranged in tandem with the loss of a conserved BglII restriction site in the RS1 element and the appearance of a new HindIII site in the same region. While there may be other factors, it appears that the reorganization of the CTX genetic element in the Calcutta O139 strains may have contributed to the resurgence of this serogroup in Calcutta.

Anti-Bacterial Agents↗
PubMed1998

Treatment of Helicobacter pylori infection in infants in rural Bangladesh with oral immunoglobulins from hyperimmune bovine colostrum.

BACKGROUND: Antibodies from hyperimmune bovine colostrum have been shown to be effective in treatment against a variety of microorganisms, including Helicobacter pylori in adults. AIM: To test this form of treatment in a small group of H. pylori infected children in a periurban community in Bangladesh. METHODS: Twenty-four infants, 4-29 months old (mean age 16.5+/-7.7 months) and infected with H. pylori, were treated with purified immunoglobulins from hyperimmune bovine colostrum for 1 month, in a placebo-controlled, double-blind pilot study. Diagnosis was established with 13C-urea breath test (UBT) before and after the treatment period and at a 1-month follow-up. RESULTS: None of the hyperimmune bovine colostrum-treated children became UBT negative. Five children initially positive in the UBT screening spontaneously became negative by the start of the study with hyperimmune bovine colostrum/placebo. At the end of the 1-month study period, three had became positive again. CONCLUSION: Hyperimmune bovine colostrum does not eradicate H. pylori infection in infants. Transient H. pylori infection is common among infants in high endemic areas, as is reinfection after clearance. This presents obstacles to evaluation of therapeutic investigations in young children in areas where H. pylori is prevalent.

Animals↗
PubMed1998

Enteric infections in an endemic area induce a circulating antibody-secreting cell response with homing potentials to both mucosal and systemic tissues.

Enteric infections induce a response of circulating pathogen-specific antibody-secreting cells (ASC). The expression of homing receptors (HRs) on these cells was studied in patients with diarrhea caused by Vibrio cholerae in Bangladesh, an area in which cholera is endemic. The gut HR, alpha4beta7, was expressed by approximately 80% of the ASC, indicating mucosal homing of these cells. However, the peripheral lymph node HR, L-selectin, was also expressed by approximately 80% of the ASC specific to either cholera toxin or O antigen. In earlier findings after oral immunization in nonendemic areas, alpha4beta7 has been expressed by approximately 100% and L-selectin by approximately 50% of the ASC. In comparison, the present data speak for a more systemic targeting of the immune response associated with long-lasting immunity in an endemic area. The results thus provide insight for the continued development and evaluation of vaccines.

Adolescent↗
PubMed1998

Increasing frequency of mecillinam-resistant shigella isolates in urban Dhaka and rural Matlab, Bangladesh: a 6 year observation.

A total of 14,915 shigella isolates obtained in 1991-1996 from patients attending the Dhaka (urban) and Matlab (rural) treatment centres of the International Centre for Diarrhoeal Disease Research, Bangladesh were examined for susceptibility to ampicillin, co-trimoxazole, nalidixic acid, mecillinam and ciprofloxacin by a disc diffusion method. There were no ciprofloxacin-resistant shigella isolates. The prevalence of resistance to ampicillin, co-trimoxazole and nalldixic acid varied between isolates. It increased to similar degrees in isolates from both Matlab and Dhaka. However, resistance to mecillinam was more prevalent among isolates from Matlab than from Dhaka. The increase in mecillinam-resistant shigellae in the community may have grave implications for the empirical treatment of shigellosis in Bangladesh and other developing countries.

Amdinocillin↗
PubMed1998

Small bowel and fecal microbiology in children suffering from persistent diarrhea in Bangladesh.

BACKGROUND: The etiology of persistent diarrhea in children is multifactorial. The objective of the current study was to ascertain the role of microorganisms in the etiology and pathogenesis of persistent diarrhea in a group of children in Bangladesh. METHODS: Enteric pathogens and total aerobic microflora were studied in the duodenal aspirates of 100 children with persistent diarrhea and compared with those in aspirates of 30 children with acute diarrhea, and those in aspirates of 15 healthy control children. The enteric pathogens in the stools of these children and in stools of an additional 38 patients with persistent diarrhea and 12 with acute diarrhea were also studied. RESULTS: Approximately two thirds of the patients with acute diarrhea and persistent diarrhea, and half of the control subjects had more than 10(5) organisms per milliliter of duodenal fluid. Significantly, more patients with persistent diarrhea had a greater variety of flora than did patients with acute diarrhea and control subjects. The predominant organisms in patients with acute diarrhea and in those with persistent diarrhea were Gram-negative rods, whereas those in control subjects were Gram-positive cocci. Significantly more acute diarrhea patients and persistent diarrhea patients had enteric pathogens isolated from stool than did control subjects. Diarrheagenic Escherichia coli, as a whole, were present in significantly more persistent diarrhea patients than in acute diarrhea patients and control subjects. Among diarrheagenic E. coli, enteroaggregative E. coli were significantly associated only with persistent diarrhea. Other organisms significantly associated with persistent diarrhea were Aeromonas spp. and Klebsiella spp. Some patients in the acute diarrhea and the persistent diarrhea groups had the same pathogens isolated from both the duodenal fluid and stool. CONCLUSIONS: In accordance with results of other studies, an association between enteroaggregative E. coli and persistent diarrhea was found in the present study. This suggests that therapy directed against enteroaggregative E. coli can be evaluated for management of some cases of persistent diarrhea.

Acute Disease↗
PubMed1998

Astrovirus infection in association with acute, persistent and nosocomial diarrhea in Bangladesh.

BACKGROUND: Diarrhea is an important public health concern in developing countries such as Bangladesh. Diarrhea in children that persists for 14 days or more occurs in 7% of patients in Bangladesh and frequently results in death. Astrovirus has been demonstrated as a cause of acute and nosocomial diarrhea and can be excreted for prolonged periods, yet its importance as a cause of diarrhea among children in a developing country like Bangladesh has not been investigated. METHODS: We tested 629 stool specimens from patients with acute diarrhea, 153 from patients with persistent diarrhea, 175 specimens from 76 patients hospitalized for diarrhea who were sampled repeatedly to detect nosocomial infection and 428 from nonhospitalized healthy children (controls). All children enrolled in the study were <5 years of age. Astrovirus was detected by enzyme immunoassay and other enteropathogens were detected by standard techniques. RESULTS: The detection of astrovirus increased significantly with the duration of diarrhea. Astrovirus was found in 23 (15%) specimens from patients with persistent diarrhea, 26 (4%) patients with acute diarrhea, but only 8 (2%) healthy controls. This trend remained when we limited our analysis to infants <12 months of age and to episodes in which astrovirus was the sole pathogen. Among patients with nosocomial diarrhea, 16% of postadmission specimens were positive for astrovirus when the admission specimen was negative. CONCLUSION: The observation that astrovirus is detected more frequently with diarrhea of increasing duration suggests the need for further studies to determine whether astrovirus plays a causative role in persistent diarrhea or is a secondary agent.

Acute Disease↗
PubMed1998

Successful treatment of rotavirus diarrhea in children with immunoglobulin from immunized bovine colostrum.

BACKGROUND: Oral ingestion of immunoglobulins in humans has been shown to be effective as prophylaxis against enteric infections. However, its therapeutic effect in children with infectious diarrhea has hitherto not been proven. We treated children with rotavirus diarrhea with immunoglobulins extracted from immunized bovine colostrum (IIBC) containing high titers of antibodies against four rotavirus serotypes. METHODS: In this double blind placebo-controlled trial, 80 children with rotavirus diarrhea were randomly assigned to receive orally either 10 g of IIBC (containing 3.6 g of antirotavirus antibodies) daily for 4 days or the same amount of a placebo preparation. The daily stool output (grams/kg/day), intake of oral rehydration solution (ml/kg/day), stool frequency (number of stools/day) and presence of rotavirus in stool were monitored for the 4 days during treatment. RESULTS: Children who received IIBC had significantly less daily and total stool output and stool frequency and required a smaller amount of oral rehydration solution than did children who received placebo (P < 0.05). Clearance of rotavirus from the stool was also earlier in the IIBC group compared with the placebo group (mean day, 1.5 vs. 2.9, P < 0.001). No adverse reactions from the colostrum treatment were observed. CONCLUSIONS: Treatment with antirotavirus immunoglobulin of bovine colostral origin is effective in the management of children with acute rotavirus diarrhea.

Administration, Oral↗
PubMed1998

Induction of fimbriated Vibrio cholerae O139.

Several fimbriated phases of Vibrio cholerae O139 strains were selectively induced and compared immunologically and biochemically with those of V. cholerae O1. Fimbrial antigens were detected on the surfaces of vibrio cells colonizing the epithelial cells of a rabbit small intestine. Convalescent-phase sera from six individuals infected with V. cholerae O139 revealed the development of antibody against the fimbrillin. These findings suggest that the fimbriae of V. cholerae O1 and O139 are expressed in vivo during infection and that consideration must be given to the use of fimbrial antigens as components of vaccines against cholera.

Animals↗
PubMed1998

Analysis of clinical and environmental strains of nontoxigenic Vibrio cholerae for susceptibility to CTXPhi: molecular basis for origination of new strains with epidemic potential.

Toxigenic Vibrio cholerae strains are lysogens of CTXPhi, a filamentous phage which encodes cholera toxin. The receptor for CTXPhi for invading V. cholerae cells is the toxin-coregulated pilus (TCP), the genes for which reside in a larger genetic element, the TCP pathogenicity island. We analyzed 146 CTX-negative strains of V. cholerae O1 or non-O1 isolated from patients or surface waters in five different countries for the presence of the TCP pathogenicity island, the regulatory gene toxR, and the CTXPhi attachment sequence attRS, as well as for susceptibility of the strains to CTXPhi, to investigate the molecular basis for the emergence of new clones of toxigenic V. cholerae. DNA probe or PCR assays for tcpA, tcpI, acfB, toxR, and attRS revealed that 6.85% of the strains, all of which belonged to the O1 serogroup, carried the TCP pathogenicity island, toxR, and multiple copies of attRS, whereas the remaining 93.15% of the strains were negative for TCP but positive for either one or both or neither of toxR and attRS. An analysis of the strains for susceptibility to CTXPhi, using a genetically marked derivative of the phage CTX-KmPhi, showed that all TCP-positive CTX-negative strains and 1 of 136 TCP-negative strains were infected by the phage either in vitro or in the intestines of infant mice. The phage genome integrated into the chromosome of infected V. cholerae O1 cells forming stable lysogens. Comparative analysis of rRNA gene restriction patterns revealed that the lysogens derived from nontoxigenic progenitors were either closely related to or distinctly different from previously described clones of toxigenic V. cholerae. To our knowledge, this is the first demonstration of lysogenic conversion of naturally occurring nontoxigenic V. cholerae strains by CTXPhi. The results of this study further indicated that strains belonging to the O1 serogroup of V. cholerae are more likely to possess the TCP pathogenicity island and hence to be infected by CTXPhi, leading to the origination of potential new epidemic clones.

Animals↗
PubMed1998

Characterization of the roles of hemolysin and other toxins in enteropathy caused by alpha-hemolytic Escherichia coli linked to human diarrhea.

Escherichia coli strains producing alpha-hemolysin have been associated with diarrhea in several studies, but it has not been clearly demonstrated that these strains are enteropathogens or that alpha-hemolysin is an enteric virulence factor. Such strains are generally regarded as avirulent commensals. We examined a collection of diarrhea-associated hemolytic E. coli (DHEC) strains for virulence factors. No strain produced classic enterotoxins, but they all produced an alpha-hemolysin that was indistinguishable from that of uropathogenic E. coli strains. DHEC strains also produced other toxins including cytotoxic necrotizing factor 1 (CNF1) and novel toxins, including a cell-detaching cytotoxin and a toxin that causes HeLa cell elongation. DHEC strains were enteropathogenic in the RITARD (reversible intestinal tie adult rabbit diarrhea) model of diarrhea, causing characteristic enteropathies, including inflammation, necrosis, and colonic cell hyperplasia in both small and large intestines. Alpha-hemolysin appeared to be a major virulence factor in this model since it conferred virulence to nonpathogenic E. coli strains. Other virulence factors also appear to be contributing to virulence. These findings support the epidemiologic link to diarrhea and suggest that further research into the role of DHEC and alpha-hemolysin in enteric disease is warranted.

Animals↗
PubMed1998

Induction of the lysogenic phage encoding cholera toxin in naturally occurring strains of toxigenic Vibrio cholerae O1 and O139.

In toxigenic Vibrio cholerae, the CTX genetic element which carries the genes for cholera toxin (CT) is the genome of a lysogenic bacteriophage (CTXPhi). Clinical and environmental strains of V. cholerae O1 or O139 and stools that were culture positive for cholera were analyzed to study the induction and transmission of CTXPhi. To our knowledge, this is the first report of the examination of CTXPhi in clinical materials and in naturally occurring strains. DNA probe analysis revealed that 4.25% (6 of 141) of the isolated V. cholerae strains spontaneously produced a detectable level of extracellular CTXPhi particles in the culture supernatants whereas another 34.04% (48 of 141) produced CTXPhi particles when induced with mitomycin C. CTXPhi isolated from 10 clinical or environmental strains infected a CT-negative recipient strain, CVD103, both inside the intestines of infant mice and under laboratory conditions. All culture-positive stools analyzed were negative for the presence of CTXPhi both in the DNA probe assay and by in vivo assay for the infection of the recipient strain in infant mice. These results suggested that naturally occurring strains of toxigenic V. cholerae are inducible lysogens of CTXPhi but that cholera pathogenesis in humans is not associated with the excretion of CTXPhi particles in stools, indicating that induction of the phage may not occur efficiently inside the human intestine. However, in view of the efficient transmission of the phage under conditions conducive to the expression of toxin-coregulated pili, it appears that propagation of CTXPhi in the natural habitat may involve both environmental and host factors.

Animals↗
PubMed1998

Association of Providencia alcalifaciens with diarrhea in children.

It has been demonstrated in previous studies that Providencia alcalifaciens can produce diarrhea by an invasive mechanism. In the present study, P. alcalifaciens was isolated from the stool specimens of 17 of 814 diarrheal children younger than 5 years of age (2.1%) and from those of 4 of 814 matched controls (0.49%) (P = 0.004), indicating that the organism is significantly associated with diarrhea. However, 71% of P. alcalifaciens-positive diarrheal children had simultaneous infections with other recognized enteric pathogens.

Child, Preschool↗
PubMed1998

Epidemiology, genetics, and ecology of toxigenic Vibrio cholerae.

Cholera caused by toxigenic Vibrio cholerae is a major public health problem confronting developing countries, where outbreaks occur in a regular seasonal pattern and are particularly associated with poverty and poor sanitation. The disease is characterized by a devastating watery diarrhea which leads to rapid dehydration, and death occurs in 50 to 70% of untreated patients. Cholera is a waterborne disease, and the importance of water ecology is suggested by the close association of V. cholerae with surface water and the population interacting with the water. Cholera toxin (CT), which is responsible for the profuse diarrhea, is encoded by a lysogenic bacteriophage designated CTXPhi. Although the mechanism by which CT causes diarrhea is known, it is not clear why V. cholerae should infect and elaborate the lethal toxin in the host. Molecular epidemiological surveillance has revealed clonal diversity among toxigenic V. cholerae strains and a continual emergence of new epidemic clones. In view of lysogenic conversion by CTXPhi as a possible mechanism of origination of new toxigenic clones of V. cholerae, it appears that the continual emergence of new toxigenic strains and their selective enrichment during cholera outbreaks constitute an essential component of the natural ecosystem for the evolution of epidemic V. cholerae strains and genetic elements that mediate the transfer of virulence genes. The ecosystem comprising V. cholerae, CTXPhi, the aquatic environment, and the mammalian host offers an understanding of the complex relationship between pathogenesis and the natural selection of a pathogen.

Cholera↗
PubMed1998

Detection of Shigellae from stools of dysentery patients by culture and polymerase chain reaction techniques.

In Bangladesh, the isolation rates of Shigella spp. range from 11% to 12% by the conventional culture technique. Since the sensitivity of this technique is low, the polymerase chain reaction (PCR) technique was used for detecting small number of Shigellae from patients' stools. Sensitivity and specificity of the two techniques were also compared. Stool samples were collected from 41 patients with dysentery who attended the Clinical Research and Service Centre of the ICDDR,B: Centre for Health and Population Research. All stool specimens were directly plated onto MacConkey, Salmonella-Shigella, Xylose lysin deoxycholate and Hectoen enteric agar media, and Shigellae were detected following standard procedures. DNA was extracted from the stool samples, and the target sequence of invasive plasmid antigen (ipa)H locus was amplified by PCR with 130 ng each of two primers (primer H8 [5'-GTTCCTTGACCGCCTTTCCGATAC-3'] and primer H15 [5'-GCCGGTCAGCCACCCTA-3']) following standard procedures. The amplified product was hybridized using an ipaH probe. The isolation rates of Shigella dysenteriae type 1, S. flexneri, S. sonnei, and S. boydii were, respectively, 17.1%, 19.5%, 4.9% and 2.4% by the conventional method. The results of the PCR technique showed that 700 bp fragment was generated in 18 of the 18 culture-positive and in 7 of the 23 culture-negative stools. One hundred twenty-three strains of Escherichia coli were also tested by PCR for identifying the enteroinvasive E. coli, but none of them yielded any positive result. This study showed that the sensitivity of the culture technique is 72% and specificity is 100%, when the PCR technique was considered as gold standard. Therefore, the PCR may be considered a more sensitive and specific technique than the conventional culture technique and has the potential to be employed in routine diagnosis of dysentery in clinical centres as well as in epidemiologic studies.

Bacteriological Techniques↗
PubMed1997

Structural analysis of the O-antigenic polysaccharide from Vibrio cholerae O10.

The structure of the O-antigenic polysaccharide part of the lipopolysaccharide isolated from Vibrio cholerae O10 has been determined. The main method used has been 1H- and 13C-NMR spectroscopy. Sugar and methylation analyses were also applied to the polysaccharide. The tetrasaccharide repeating unit of the polysaccharide was found to have the following structure: -->3)-alpha-D-ManpNAc-(1-->4)-beta-D-GlcpA-(1-->3)-beta-D-Ga lp-(1-->3)-beta-D-GlcpNAc-(1-->.

Carbohydrate Conformation↗
PubMed1997

Characterization of filamentous phages of Vibrio cholerae O139 and O1.

We have analyzed our collection of Vibrio cholerae O139 strains to determine whether filamentous phages are produced in their culture supernatants, and whether any replicative form of DNA is detectable in cell lysates. Two types of filamentous phage, designated fs1 (6.4 kb) and fs2 (8.5 kb), were found in strains of Vibrio cholerae O139, fs1 was commonly produced from clinical isolates of Vibrio cholerae O1. Infectious particles (filamentous phages) were inducible by subculture, mitomycin C, and cultivation in a ligated ileal loop of a rabbit. Type 4 fimbriae of Vibrio cholerae O1 sensitive to D-glucose and D-mannose were suggested to be receptors for fs1 and fs2. The genome of fs1 was revealed to encode a potential new enterotoxin homologous to zonula occludens toxin. Clarification of the relation of type 4 fimbriae and these filamentous phages will provide a new understanding of the colonization of Vibrio-cholerae O1 and O139. Thus the presence of a new enterotoxin encoded by the genome of filamentous phage like fs1 may clarify the pathogenesis of cholera toxin negative clinical isolates of Vibrio cholerae O1 and non-O1. Our findings combined with the earlier report by Ehara et al. [Microbio. Immunol. 37 (1993) 679-688] suggest that type 4 fimbriae of Vibrio cholerae O1 are important for the development of an effective vaccine against cholera.

Animals↗
PubMed1997

Intraarticular calcaneus fractures: a biomechanical comparison or two fixation methods.

OBJECTIVE: To compare the strength of fixation obtained using two unicortical 4.0 mm diameter cancellous screws versus two bicortical 3.5 mm diameter cortical screws in the fixation of intra-articular calcaneus fractures. DESIGN: In eight paired fresh frozen cadaver feet, the subtalar joint complex, consisting of the talus, interosseous ligaments, and calcaneus was removed as a unit. An oblique osteotomy of the calcaneus was then created in the sagittal plane. The two fragments were reduced and stabilized using either two unicortical 4.0 mm diameter cancellous screws or two bicortical 3.5 mm diameter cortical screws. A force was then applied to the medial calcaneal tuberosity until failure occurred. In all specimens testing was discontinued due to ligamentous failure, without causing bony disruption. RESULTS: In all specimens the forced applied to the calcaneus created a disruption of the interosseous ligaments across the subtalar joint and rotation of the calcaneus on the talus. Thus in each specimen, testing was discontinued due to interosseous ligamentous failure, without causing bony disruption. There was no statistically significant difference in force to failure between the specimens fixed with 3.5 mm diameter cortical screws as compared to those fixed with 4.0 mm diameter cancellous screws. CONCLUSIONS: The lack of a statistically significant difference in force to failure of the intra-articular calcaneus fractures fixed using 3.5 mm diameter cortical screws as compared to those fixed using 4.0 mm diameter cancellous screws and, the fact that the mode of failure was a disruption of ligaments rather than bony disruption suggest that either method of screw fixation is biomechanically adequate.

Aged↗