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Biomedical subjects

M John Albert

Publications and source records attributed to M John Albert.

At least 19 recordsLinked to original sources
PubMed2006

Persistence, transmission, and virulence characteristics of Aeromonas strains in a duckweed aquaculture-based hospital sewage water recycling plant in Bangladesh.

The persistence and transmission of Aeromonas in a duckweed aquaculture-based hospital sewage water treatment plant in Bangladesh was studied. A total of 670 samples from different sites of the hospital sewage water treatment plant, from feces of hospitalized children suffering from diarrhea, from environmental control ponds, and from feces of healthy humans were collected over a period of three years. In total, 1,315 presumptive Aeromonas isolates were biochemically typed by the PhenePlate rapid screening system (PhP-AE). A selection of 90 representative isolates was further analyzed with PhenePlate (PhP) extended typing (PhP-48), fatty acid methyl ester analysis, and amplified fragment length polymorphism (AFLP) fingerprinting. In addition, the prevalence of the putative virulence factors hemolysin and cytotoxin and the presence of the cytolytic enterotoxin gene (AHCYTOEN) were analyzed. Aeromonas was found at all sites of the treatment plant, in 40% of the samples from environmental control ponds, in 8.5% of the samples from hospitalized children suffering from diarrhea, and in 3.5% of samples from healthy humans. A significantly high number of Aeromonas bacteria was found in duckweed, which indicates that duckweed may serve as a reservoir for these bacteria. PhP-AE typing allowed identification of more than 192 distinct PhP types, of which 18 major PhP types (MTs) were found in multiple sites and during several occasions. AFLP fingerprinting revealed the prevalence of genotypically indistinguishable Aeromonas isolates among certain PhP MTs recovered from different sampling occasions and/or at multiple sites. Hemolytic and cytotoxic activities were observed in 43% of the tested strains, whereas 29% possessed the cytolytic enterotoxin gene AHCYTOEN. Collectively, two specific MTs associated with diarrhea were shown to exhibit high cytotoxicity. Furthermore, all tested isolates of these major types were positive for the cytolytic enterotoxin gene. In conclusion, our data indicate that certain phenotypically and genotypically stable clonal lineages of Aeromonas have persisted in the treatment system for a prolonged period and might spread from the hospitalized children suffering from diarrhea to fish produced for human consumption through the sewage water treatment system.

Aeromonas↗
PubMed2006

High prevalence and level of resistance to metronidazole, but lack of resistance to other antimicrobials in Helicobacter pylori, isolated from a multiracial population in Kuwait.

BACKGROUND: The primary treatment regimen for Helicobacter pylori infection for Kuwaitis does not contain metronidazole, but that for expatriates does. There is also increasing failure of antimicrobial therapy. AIM: To determine the susceptibility of H. pylori from upper gastrointestinal biopsies of Kuwaitis and non-Kuwaitis to find out if differences existed in the susceptibilities of the isolates from the two different populations. METHODS: The susceptibilities of 96 H. pylori isolates were tested against metronidazole, amoxicillin, clarithromycin and tetracycline by the E test. The rdxA gene was analysed from selected metronidazole-susceptible and metronidazole-resistant strains to find out polymorphism and the basis of metronidazole resistance. RESULTS: Approximately, 70% of isolates from both populations were metronidazole resistant with 65% isolates showing high minimum inhibitory concentration values of >256 mug/mL. No resistance to the other three antimicrobials was found. There were novel nonsense and missense mutations with no deletion in the rdxA gene by insertion of mini-IS605. CONCLUSIONS: The prevalence and level of metronidazole resistance in H. pylori in the two populations was high with no difference, in spite of different treatment regimens. Metronidazole resistance in this transitional country appeared to be independent of prior metronidazole use for treatment of H. pylori infection.

Anti-Bacterial Agents↗
PubMed2006

Implementation of good clinical practice guidelines in vaccine trials in developing countries.

The practicalities when applying the ICH GCPs (International Conference on Harmonization 1996 Good Clinical Practices [EU, MHLW, FDA. International Conference on Harmonization Guideline for Good Clinical Practice; 1997] in less developed countries (ldcs) are seldom discussed and we found no guidelines as how to "adapt" them. Below we illustrate how ICH GCP principles can be implemented in different settings. We have recently conducted in Asia (Hechi, China; Karachi, Pakistan; Hue, Vietnam; North Jakarta, Indonesia and Kolkata, India) large-scale cluster-randomized effectiveness evaluations of the Vi polysaccharide typhoid fever vaccine (Vi PS project) among approximately 200,000 individuals(1)[Acosta CJ, Galindo CM, Ali M, Abu-Elyazeed R, Ochiai RL Danovaro-Holliday MC et al. A multi-country cluster randomized controlled effectiveness evaluation to accelerate the introduction of Vi polysaccharide typhoid vaccine in developing countries in Asia: rationale and design. TMIH 2005;10(12):1219-1228]. There is no doubt on the importance of ICH GCP in its contribution to ethical and scientifically sound clinical research. However, when the ICH GCP is implemented in ldcs some considerations must be made in order to adequately tailor them. Vaccine trials in ldcs are a frequent setting for such challenges because of the increased global interest conducting health research in such countries. The ICH GCP principles are discussed below within the framework of this recent typhoid fever vaccine study experience.

Developing Countries↗
PubMed2006

Aetiology of diarrhoea in a birth cohort of children aged 0-2 year(s) in rural Mirzapur, Bangladesh.

The incidence of aetiology-specific diarrhoea and the pathogenicity of infectious agents in a birth cohort (n=252) in rural Bangladesh were determined. Stool specimens or rectal swabs were collected from diarrhoeal cases over two years and routinely on a monthly basis. Stool samples from children with diarrhoea were compared with stool samples from children without diarrhoea to calculate rates of isolation and pathogenicity of agents. In total, 1750 stool specimens from diarrhoea patients and 5679 stool specimens from children without diarrhoea were tested. An infectious agent was identified in 58% of the stool specimens from diarrhoea patients and 21.6% of the stool specimens from children without diarrhoea. The most commonly-isolated pathogens from all specimens were enterotoxigenic Escherichia coli (ETEC), enteroadherent E. coli, Shigella, Campylobacter jejuni, Giardia, and rotavirus. ETEC (ST and LT-ST toxin), enterotoxigenic Bacteroides fragilis, Shigella, and rotavirus were associated more with disease than with asymptomatic infections. Aetiology-specific infections were associated with acute episodes. The isolated enteropathogens were essentially the same as those found in other tropical rural settings. Enterotoxigenic B. fragilis was also identified as a pathogen. Ongoing vaccine efforts focusing on Shigella, rotavirus, and ETEC would be useful.

Bacterial Infections↗
PubMed2005

PorA protein of Campylobacter jejuni is not a cytotoxin mediating inflammatory diarrhoea.

Campylobacter jejuni is a major food-borne pathogen and a leading cause of diarrhoea. A cytotoxin is most likely involved in the pathogenesis of inflammatory diarrhoea due to C. jejuni. A 45-kDa outer membrane protein encoded by the porA gene was reported to exhibit cytotoxic activity for cultured mammalian cells in vitro. We cloned and expressed the porA gene in Escherichia coli BL21 codon plus RIL strain using the fusion vector pGEX-4T-1. The fusion protein solubilised in urea in denatured form or solubilised in Empigen BB in native form or their thrombin-cleaved products did not exhibit cytotoxic activity for Chinese hamster ovary (CHO) cells. The urea-solubilised fusion protein did not induce fluid accumulation in the rabbit ileal loop assay. All 76 clinical isolates of Campylobacter spp. tested were positive for porA by PCR, but only 13 isolates were positive for cytotoxin on CHO cells. Both cytotoxin-positive as well as cytotoxin-negative strains expressed PorA as determined by immunoblot analysis. These findings show that the porA gene product of C. jejuni is not a cytotoxin mediating inflammatory diarrhoea.

Animals↗
PubMed2005

Ciprofloxacin resistance and its molecular mechanism in Campylobacter spp. isolated in Kuwait.

Campylobacter spp. are an important cause of diarrhea in Kuwait. Because susceptibility data for ciprofloxacin and erythromycin, the two recommended drugs for treatment, are not available for this part of the world, 64 Campylobacter spp. isolates obtained from human diarrheal stools in Kuwait during 2000--2003 were studied for susceptibility to these antimicrobials by E-test. The utility of a simple mismatch amplification mutation assay (MAMA) PCR to detect base substitution in the gyrA gene mediating resistance to ciprofloxacin was also explored. Approximately, 53% (34/64) of the isolates were resistant to ciprofloxacin (MIC, 4-64 microg/ml) and 5% (3/64) to erythromycin (MIC>256 microg/ml). MAMA PCR showed a Thr-86-to-Ile mutation in gyrA gene of 23/26 ciprofloxacin-resistant C. jejuni, and in all resistant C. coli. Sequencing of PCR product showed that two resistant strains of C. coli studied had Thr-86-to-Ile (ACT--> ATT) gyrA mutation and three resistant strains of C. jejuni studied had Thr-86-to-Ile (ACA--> ATA) gyrA mutation. In addition, all the three C. jejuni strains had silent mutations. Thus, ciprofloxacin is of limited use for treatment in Kuwait and MAMA PCR is a useful assay to study gyrA mutation. Because Kuwait has a large expatriate population of workers, it can be a focus of spread of antimicrobial resistance.

Campylobacter↗
PubMed2005

Isolation and characterization of provisional serovar Shigella boydii E16553 from diarrhoeal patients in Bangladesh.

In previous studies with strains of the Shigella dysenteriae provisional serovars E22383 and E23507 from diarrhoeal stools from patients in Bangladesh, two strains of Shigella species were identified as Shigella boydii provisional serovar E16553 by a reference laboratory. Further tests with an antiserum to an international type strain of the provisional serovar E16553 identified an additional 15 isolates. None of the isolates reacted with antisera to the established Shigella serovars or any other provisional serovars reported so far and all showed biochemical reactions typical of S. boydii. All of the isolates harboured the 140 MDa invasion plasmid, had the ipaH gene and produced keratoconjunctivitis in the guinea pig eye. All isolates were susceptible to ampicillin, sulfamethoxazole-trimethoprim, nalidixic acid, ciprofloxacin and mecillinam but eight strains were resistant to tetracycline. A single PFGE type (type A) was shown for all 17 clinical isolates, indicating a common source of origin. The pulsotype of the Bangladeshi isolates was closely related to that of a Japanese strain but was different from that of the type strain. On the basis of these biochemical, serological and virulence markers, and diverse geographical origin, it is recommended that the provisional status of serovar E16553 be changed and that it be included in the international serotyping classification scheme as S. boydii 19.

Animals↗
PubMed2005

Critical factors influencing the occurrence of Vibrio cholerae in the environment of Bangladesh.

The occurrence of outbreaks of cholera in Africa in 1970 and in Latin America in 1991, mainly in coastal communities, and the appearance of the new serotype Vibrio cholerae O139 in India and subsequently in Bangladesh have stimulated efforts to understand environmental factors influencing the growth and geographic distribution of epidemic Vibrio cholerae serotypes. Because of the severity of recent epidemics, cholera is now being considered by some infectious disease investigators as a "reemerging" disease, prompting new work on the ecology of vibrios. Epidemiological and ecological surveillance for cholera has been under way in four rural, geographically separated locations in Bangladesh for the past 4 years, during which both clinical and environmental samples were collected at biweekly intervals. The clinical epidemiology portion of the research has been published (Sack et al., J. Infect. Dis. 187:96-101, 2003). The results of environmental sampling and analysis of the environmental and clinical data have revealed significant correlations of water temperature, water depth, rainfall, conductivity, and copepod counts with the occurrence of cholera toxin-producing bacteria (presumably V. cholerae). The lag periods between increases or decreases in units of factors, such as temperature and salinity, and occurrence of cholera correlate with biological parameters, e.g., plankton population blooms. The new information on the ecology of V. cholerae is proving useful in developing environmental models for the prediction of cholera epidemics.

Animals↗
PubMed2005

A phase II dose-increasing study of sitamaquine for the treatment of visceral leishmaniasis in Kenya.

Sitamaquine (WR6026) is an 8-aminoquinoline in development for the oral treatment of visceral leishmaniasis (VL). This was an open-label, dose-increasing study to determine the dose-response and safety profile for sitamaquine in Kenyan patients with VL caused by Leishmania donovani. Patients (mean age 15.9 [range = 5-47] years) received sitamaquine daily for 28 days at one of four doses: 1.75 (n = 12), 2.0 (n = 61), 2.5 (n = 12), or 3.0 (n = 12) mg/kg/day. The primary efficacy outcome was cure (absence of parasites on splenic aspirate) in the intent-to-treat population at day 180. Cure was achieved in 79 (83%) of 95 patients overall, and in 11 (92%) of 12, 49 (80%) of 61, 9 (82%) of 11, and 10 (91%) of 11 patients at sitamaquine doses of 1.75, 2.0, 2.5, or 3.0 mg/kg/day, respectively. The most frequent adverse events during active treatment were abdominal pain (12 [12%] of 97) and headache (11 [11%] of 97), and one patient in each of the 2.5 mg/kg/day and 3.0 mg/kg/day dose groups had a severe renal adverse event. The effects of sitamaquine on the kidney need further investigation. Sitamaquine was efficacious and generally well tolerated in Kenyan patients with VL.

Adolescent↗
PubMed2004

Suppressive effect of zinc on antibody response to cholera toxin in children given the killed, B subunit-whole cell, oral cholera vaccine.

In a previous study, children aged 2-5 years old in Bangladesh were supplemented orally with a single dose of Vitamin A (200,000 IU) and a placebo for zinc (zinc equivalent to 20 mg of elemental zinc) everyday for 42 days (group A), zinc and a placebo for Vitamin A (group Z), zinc and Vitamin A (group AZ) or both placebos (group P). All children were orally immunised with two doses of the killed cholera vaccine containing whole cells and a recombinant B subunit of cholera toxin (CT). The number of children who responded with > or = 4-fold vibriocidal antibody (a proxy indicator of protection against cholera) was significantly greater among the zinc-supplemented groups than among the non-zinc-supplemented groups, while Vitamin A supplementation did not appear to have any effect. The sera from these children were assayed for antibody to CT. Antibody to CT is known to exert a synergistic protective effect against cholera in animal studies, and offer significantly higher short-term protection against cholera and significant short-term protection against enterotoxigenic Escherichia coli diarrhoea in humans on oral immunisation with the cholera vaccine. Children who received zinc had significantly reduced levels of serum antibodies to CT than children who received placebos only. Factorial analysis showed a trend for zinc showing a reduction in the number of children responding with CT-antibody, while Vitamin A did not appear to have any effect. Thus, zinc enhanced vibriocidal antibody response, but suppressed CT-antibody response, suggesting that zinc supplementation has different modulating effects on vibriocidal antibody response and CT-antibody response.

Administration, Oral↗
PubMed2004

Vibrio cholerae (non-O1, non-O139) sepsis in a child with Fanconi anemia.

A 9-year-old female child who was a known case of Fanconi anemia was admitted to hospital because of fever and gastrointestinal symptoms. Blood culture at the time of admission yielded growth of Gram-negative curved rod that was identified as Vibrio cholerae (non-O1, non-O139), whereas repeated fecal cultures were negative for enteropathogens. To our knowledge, this is the first case of V. cholerae (non-O1, non-O139) septicemia associated with Fanconi anemia.

Anti-Bacterial Agents↗
PubMed2004

SepL, a protein required for enteropathogenic Escherichia coli type III translocation, interacts with secretion component SepD.

Enteropathogenic Escherichia coli (EPEC), an important cause of infantile diarrhoea in the developing world, disrupts host cell microvilli, causes actin rearrangements and attaches intimately to the host cell surface. This characteristic phenotype, referred to as the attaching and effacing (A/E) effect, is encoded on a 36 kb pathogenicity island called the locus of enterocyte effacement (LEE). The LEE includes genes involved in type III secretion and translocation, the eae gene encoding an outer membrane adhesin known as intimin, the tir gene for the translocated intimin receptor, a regulator and various genes of unknown function. Among this last group is sepL. To determine the role of SepL in EPEC pathogenesis, we constructed and tested a non-polar sepL mutant. We found that this sepL mutant is deficient for A/E and that it secretes markedly reduced quantities of those proteins involved in translocation (EspA, EspB and EspD), but normal levels of those proteins presumed to be effectors (Tir, EspF and EspG). Despite normal levels of secretion, the mutant strain was unable to translocate EspF and Tir into host cells and formed no EspA filaments. Fractionation studies revealed that SepL is a soluble cytoplasmic protein. Yeast two-hybrid and affinity purification studies indicated that SepL interacts with the LEE-encoded protein SepD. In contrast to SepL, we found that SepD is required for type III secretion of both translocation and effector proteins. Together, these results demonstrate that SepL has a unique role in type III secretion as a functional component of the translocation system that interacts with an essential element of the secretion machinery.

Bacterial Adhesion↗
PubMed2004

The role of epidemiology in the introduction of vi polysaccharide typhoid fever vaccines in Asia.

Despite the availability of at least two licensed typhoid fever vaccines--injectable sub-unit Vi polysaccharide vaccine and live, oral Ty21a vaccine--for the last decade, these vaccines have not been widely introduced in public-health programmes in countries endemic for typhoid fever. The goal of the multidisciplinary DOMI (Diseases of the Most Impoverished) typhoid fever programme is to generate policy-relevant data to support public decision-making regarding the introduction of Vi polysaccharide typhoid fever immunization programmes in China, Viet Nam, Pakistan, India, Bangladesh, and Indonesia. Through epidemiological studies, the DOMI Programme is generating these data and is offering a model for the accelerated, rational introduction of new vaccines into health programmes in low-income countries. Practical and specific examples of the role of epidemiology are described in this paper. These examples cover: (a) selection of available typhoid fever vaccines to be introduced in the programme, (b) generation of policy-relevant data, (c) providing the 'backbone' for the implementation of other multidisciplinary projects, and (d) generation of unexpected but useful information relevant for the introduction of vaccines. Epidemiological studies contribute to all stages of development of vaccine evaluation and introduction.

Asia↗
PubMed2003

Supplementation with zinc, but not vitamin A, improves seroconversion to vibriocidal antibody in children given an oral cholera vaccine.

To investigate whether micronutrient supplementation could improve the vibriocidal antibody response of children to a killed oral cholera vaccine, 2-5-year-old children were randomly assigned to receive vitamin A and zinc (AZ group), vitamin A and a placebo (A group), zinc and a placebo (Z group), or both placebos (P group). All children received 2 doses of the vaccine. The number of children who had a > or = 4-fold increase in vibriocidal antibody was significantly greater in the AZ group than in the P group (P = .025-.028). Factorial analysis suggested that the proportion of children with a > or = 4-fold increase in vibriocidal antibody titer was significantly greater in the zinc-supplemented groups than in the groups that did not receive zinc (P = .013-.048) and that vitamin A supplementation did not have a significant effect. Thus, supplementation with zinc improves seroconversion to vibriocidal antibody and, hence, has the potential to improve the efficacy of oral cholera vaccine in children.

Administration, Oral↗
PubMed2003

Lack of polymorphism in a Vibrio cholerae O139-specific DNA region encoding the somatic antigen in strains isolated during 1993-1998.

Vibrio cholerae O139 Bengal emerged as a second aetiologic agent of cholera in South Asia in late 1992. This new serogroup arose from a Vibrio cholerae O1 strain by deletion of the chromosomal region encoding O1 specificity and acquisition of a novel 35-kb region encoding the O139 specificity. Previous studies indicated significant phenotypic and genotypic changes in O139 isolates over the years since its first appearance. This prompted us to study possible polymorphism in the 35-kb novel region encoding the O139 specificity. A total of 17 V. cholerae O139 isolates originating from different countries and years in South Asia and China, and a single unrelated V. cholerae O139 isolate from Argentina were studied. The 35-kb chromosomal region was amplified as two fragments of 12 and 23 kb in an extended PCR from all isolates. These amplicons were then treated separately with seven different restriction enzymes and separated by agarose gel electrophoresis. The South Asian and Chinese isolates gave identical patterns for the same enzymes, but different patterns for different enzymes, thus exhibiting no polymorphism in the 35-kb region. However, the Argentine isolate gave distinct patterns for most of the enzymes confirming its different origin. This data indicated that the portion of the chromosome encoding the O139 antigen specificity is highly conserved. As found in previous studies, the early O139 isolates were resistant to trimethoprim-sulfamethoxazole (TMP-SMX) and vibriostatic compound, O/129, and CAMP- haemolysin positive. The isolates of later years diverged exhibiting different patterns by pulsed-field gel electrophoresis (PFGE), and becoming susceptible to TMP-SMX and O/129, and CAMP-haemolysin negative.

Anti-Bacterial Agents↗
PubMed2003

DNA-level characterization of Helicobacter pylori strains from patients with overt disease and with benign infections in Bangladesh.

The complex relation between the genotype of Helicobacter pylori and its association with clinical outcome is not well understood. Studies in the West have showed that strains expressing certain virulence factors (vacAs1, vacAm1, and cagA) are associated with duodenal ulcer disease. However, the H. pylori genotype is known to vary with geographic region. In the present study, we compared several virulence markers (cagA, vacA, and iceA) and neutral markers (IS605, IS606, and IS608) in H. pylori strains isolated from 65 adult patients with peptic ulcer (PU) and 50 patients with nonulcer dyspepsia (NUD). PCR tests indicated that cagA is present in 75% of the strains from patients with PU compared to 55% in patients with NUD, and 80% of the isolates from patients with PU carried potentially toxigenic vacAs1 alleles of the vacuolating cytotoxin gene (vacA) compared to 60% in isolates from patients with NUD. However, no significant difference in any other virulence marker was observed in isolates from both groups. Phylogenetic analysis of the vacA middle region and the 5' end of the cagA gene indicates that Bangladeshi isolates are more closely related to H. pylori isolates from India and are different from isolates from East Asia.

Adult↗
PubMed2002

The structure of the O-chain of the lipopolysaccharide of a prototypal diarrheagenic strain of Hafnia alvei that has characteristics of a new species under the genus Escherichia.

The structure of the O-polysaccharide of the lipopolysaccharide from a diarrheal strain isolated in Bangladesh was studied with sugar, and methylation analysis, NMR spectroscopy, mass spectrometry and partial acid hydrolysis. The strain was first designated as Hafnia alvei, but later found to be a possible new species in the genus Escherichia. Two different polysaccharides were detected, a major and a minor one. The structure of the major polysaccharide is given below, while the structure of the minor one was not investigated. The structure of the repeating unit was established as The structure does not resemble any of the previously investigated lipopolysaccharide O-chains from Escherichia coli or H. alvei, but could fit in either group based on types of sugar residues and acidity. Phenotypic microbiological studies cannot definitely assign it to either species of the two genera. Genetic hybridization studies indicate that the Bangladeshi isolates may require a new species designation under the genus Escherichia.

Carbohydrate Conformation↗