[Show abstract][Hide abstract] ABSTRACT: A live oral cholera vaccine developed from a non-toxigenic Vibrio cholerae O1 El Tor strain VA1.3 was tested in a double-blind randomized placebo controlled study for safety and immunogenicity in 304 men aged between 16 and 50 years from Kolkata, India. A dose of 5 x 10(9)CFU (n=186) or a placebo (n=116) containing the diluent buffer was administered. The vaccine did not elicit adverse events except in two vaccine recipients with mild diarrhoea and vomiting. None excreted the vaccine strain. Vibriocidal antibody response developed in 105/186 (57%) and 5/116 (4%) in vaccine and placebo recipients, respectively. In a subgroup, anti-CT antibody rose (> or =2-folds) in 23/30 (77%) and 6/19 (32%) in vaccine and placebo recipients, respectively. These studies demonstrate that VA1.3 at a dose of 5 x 10(9) is safe and immunogenic in adults from a cholera endemic region.
[Show abstract][Hide abstract] ABSTRACT: Temperate phage PS166 infection of Vibrio eltor MAK757 resulted in complete changes in all biotype-specific determinants. About 10% of the PS166 lysogens of MAK757 lost their eltor-specific determinants, namely, the ability to produce soluble hemolysin, cell-associated hemagglutinin for chicken erythrocytes, and resistance to polymyxin B, as well as resistance to Mukherjee's group IV phage and sensitivity to eltor phage e4. These lysogens were found to have acquired the properties of classical strains, most significantly becoming sensitive to group IV phage but resistant to eltor-specific e4. The remainder of these lysogens, however, retained their parental biotype and serotype but acquired auxotrophy for glycine and histidine. The differential behavior of the two types of lysogen was due to the integration of the phage PS166 genome at different locations in the host chromosome. A 800-bp BglII fragment was found to contain the attP site. Phage PS166 has a polyhedral head (95 nm in diameter) and a contractile tail (98 nm in length). The phage chromosome is a linear double-stranded DNA of 110 kb and a G + C content of 58.7%.
[Show abstract][Hide abstract] ABSTRACT: Temperate phage PS166 lysogens of Vibrio eltor MAK757 biotype eltor belong to two major categories. Seventy percent of the lysogens acquire auxotrophy for glycine and histidine and maintain their parental biotype. About 10% of the lysogens become Cys(-) or Cys(-) Met(-) and are converted to the classical biotype with complete changes in all biotype-specific determinants. PCR and RFLP analysis revealed that in the latter lysogens, the phage genome integrated at the hlyA locus, whereas the same locus remained unaffected in lysogens that retained their parental biotype. These results suggest that the two types of lysogens arose due to integration of the phage genome at two different locations on the chromosome. A restriction map of the phage genome was constructed using AvaII and BglII. An 800-bp BglII fragment carrying the attP site, located at one of the termini of the phage genome, was used to distinguish the two classes of lysogen.
[Show abstract][Hide abstract] ABSTRACT: The disease cholera is an important cause of mortality in many developing countries. Though it can be controlled through improved sanitation, this goal is not easily attainable in many countries. Development of an efficacious vaccine offers the best immediate solution. A new oral candidate vaccine has been constructed from a non-toxigenic strain of Vibrio cholerae E1 Tor, Inaba, which is not only devoid of the cholera toxin (CT) virulence cassette but also is completely non-reactogenic in rabbit ileal loop assay. The strain, however, had toxR and tcpA genes. Through a series of manipulations, the ctxB gene of V. cholerae, responsible for the production of the 'B' subunit of the cholera toxin (CTB) was introduced into the cryptic hemolysin locus of the strain. The resulting strain, named vaccine attempt 1.3 (VA1.3), was found to be able to produce copious amounts of CTB. In the RITARD model this strain was found to be non-reactogenic and provided full protection against the challenge doses of both V. cholerae O1, classical and E1 Tor. In the immunized rabbit it invoked significant levels of anti-bacterial and anti-toxin immunity.
[Show abstract][Hide abstract] ABSTRACT: In the context of the reemergence of V. cholerae O1 in India and the recent evidence that O139 strains could have evolved from O1 E1 Tor strains, restriction fragment length polymorphism (RFLP) of the rRNA and the ctx genes and the antibiotic sensitivity profile of the two strains of V. cholerae, one an O1 and the other an O139, associated with mixed infection, were examined to determine their relatedness. Our results demonstrate that although the strains belonged to different clones of V. cholerae, they showed similar antibiotic sensitivity, profile indicating some exchange of genetic elements.
The Indian Journal of Medical Research 06/1998; 107:199-203. · 1.40 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present molecular evidence that a distinct genotype of Vibrio cholerae O1 which appeared in Calcutta, India, in September 1993 and which is characterized by a unique ribotype that is not found in the standardized ribotyping scheme of V. cholerae and that shows a specific pulsed-field gel electrophoresis profile may have spread to the west African country of Guinea-Bissau where it was responsible for an epidemic of cholera which began in October 1994 and continued into 1996.
Journal of Clinical Microbiology 03/1998; 36(3):843-4. · 3.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We studied the restriction fragment length polymorphism of the rRNA gene and CTX genetic element in Vibrio cholerae O139 Bengal, which resurged in Calcutta in September 1996 after a gap of 32 months. While the strains from this resurgence were indistinguishable from the earlier strains by ribotyping, the structure of the CTX genetic element present in the current O139 strains was found to be unconventional.
Journal of Clinical Microbiology 01/1998; 35(12):3348-50. · 3.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Sixty-one clinical strains of Vibrio cholerae O1 El Tor isolated in Calcutta before, during, and after the V. cholerae O139 Bengal outbreak were examined to see if the O1 strains of the post-O139 period were different from those in existence before. Comparison of the restriction fragment length polymorphism of the rRNA genes (ribotyping) and the CTX genetic element revealed that all "before" strains except 1 belonged to a single known ribotype, whereas all "after" strains except 2 belonged to a hitherto undescribed ribotype. Also, 23 of 25 "before" strains harbored two or more copies of CTX in tandem and also a "free" RS1 element away from CTX, whereas 19 of 21 "after" strains had a single copy of CTX and no free RS1 element. CTX occupied different chromosomal locations in "before" and "after" strains. These studies clearly showed that El Tor O1 strains, which displaced V. cholerae O139 in Calcutta, belonged to a new clone and suggested that there is a continuous genetic reassortment among El Tor strains of V. cholerae O1.
The Journal of Infectious Diseases 06/1997; 175(5):1134-41. DOI:10.1086/516453 · 6.00 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Abstract An unusual filamentous bacteriophage, VSK, containing single-stranded, circular DNA as its genome was isolated from Vibrio cholerae 0139 strains P07 and B04. Unlike other single-stranded DNA phages, VSK can integrate its genome into the chromosome of the host and enter into a lysogenic state. The double-stranded replicative form (RF) of the single-stranded phage DNA was isolated. A restriction map of the VSK RF DNA was constructed using HaeII, AvaII, ClaI and XbaI. By Southern blot analysis of the chromosomal DNA of the lysogen using labeled phage DNA as probe, the attachment site (attP) on the viral genome was also identified.
[Show abstract][Hide abstract] ABSTRACT: First attempt at cholera vaccination was made by Jaime Ferran in 1884. Since then, a variety of strategies and methods have been evolved to create a safe, efficacious vaccine against cholera. For the first few years emphasis was on the development of parenteral vaccines. However, as a result of accumulation of a tremendous amount of knowledge, not only on Vibrio cholerae-the causative agent, but also on its interaction with the host, emphasis has shifted towards the development of oral vaccines. Two such vaccines, one killed, a whole cell/B subunit combination vaccine and the other a live attenuated one, have shown promise. The combination vaccine in its present state of development confers only a transient protection in young children, while the live attenuated one produces adverse reaction. To combat these, various strategies are being evolved. In one attempt, a potential candidate vaccine strain has been constructed from a non-reactogenic clinical isolate of V. cholerae, which is devoid of all known major virulence genes and is also a good colonizer. In animal studies this construct has shown considerable promise. This review discusses the various strategies that have been employed so far in the quest for an ideal cholera vaccine.
The Indian Journal of Medical Research 08/1996; 104:60-75. · 1.40 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Sixty-nine strains of Vibrio cholerae O1 isolated at different times were analysed to investigate if there were any differences among the O1 strains isolated before, during and after the advent of the O139 serogroup. Of the 69 O1 strains examined, 68 belonged to the Ogawa serotype while one belonged to the Inaba serotype. With the exception of one strain all other strains of V. cholerae O1 belonged to the eltor biotype. A single O1 strain isolated before the emergence of the O139 serogroup could not be classified as either eltor or classical biotype because it was resistant to both classical and eltor specific bacteriophages. Marked variations in the susceptibility to antibiotics of V. cholerae O1 isolated during the different periods were observed. In addition, strains of V. cholerae isolated after the epidemic of serogroup O139 in Calcutta showed an expanding R-type with resistance to a variety of drugs as compared to the O1 strains isolated before the advent of the O139 serogroup. From this study, it is clear that there is a substantial mobility in genetic elements of V. cholerae O1 which necessitates a continuous monitoring to keep abreast of the changing traits of the etiologic agent of cholera.
Epidemiology and Infection 01/1996; 115(3):427-34. DOI:10.1017/S0950268800058581 · 2.54 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A temperate bacteriophage isolated from Vibrio cholerae O139, the new epidemic strain of cholera, was found to have a polyhedral head 65 nm in diameter and a rigid contractile tail 120 nm in length. The phage chromosome was a double-stranded DNA of 35 kb, with unique cohesive ends and had a G + C content of 58.8%. A restriction map of the phage DNA was constructed using the restriction endonucleases AvaI and BstEII. The phage, whose presence could be detected in nine out of 13 V. cholerae O139 isolates tested, was found to have identical chromosomal integration sites in all the strains. The phage attachment site (attP) was found to be located very close to one end of the genome.
[Show abstract][Hide abstract] ABSTRACT: Four outbreak strains of Vibrio cholerae O139 from endemic areas of India and Bangladesh were found to carry lysogenic phage(s). All of these phage(s) produced turbid plaques characteristic of lysogeny on V. cholerae MAK 757 (El Tor, Ogawa) cells as well as on their VcA-1 lysogens but were unable to infect V. cholerae 154 (classical) cells, the universal host for all classical phages. Colonies in the turbid plaques were O139 lysogens and these developed an auxotrophic requirement, mainly for purines suggesting the integration of the prophage into the host chromosome. The immunity profile of the O139 phage(s) was similar to that of phage alpha but differed in the sensitivity of the phage lysogen of V. cholerae MAK 757 to subsequent infection by phage beta.
Journal of Medical Microbiology 07/1995; 42(6):399-403. DOI:10.1099/00222615-42-6-399 · 2.25 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Four lines of evidence suggest that the recent outbreak strains of Vibrio cholerae 0139 could have emerged from serogroup 01 strains typified by isolates MOl and M0477 described in this paper, which are neither truly classical nor truly El Tor in their biotype attributes. Firstly, like all 0139 isolates, these 01 strains, isolated in Madras during and before the 0139 outbreak, were resistant not only to polymyxin B but also to all biotype- specific choleraphages, i.e. classical phage (Dl49 and El Tor phages e4 and e5. Secondly, the restriction fragment pattern (RFP) polymorphism displayed by these strains for the cholera toxin (ctx) gene, were identical with those produced by 0139 isolates but were different from those of 01 type strains, namely V. cholerae 569B (classical) and V. cholerae MAK757 (El Tor). Thirdly, all the 0139 isolates and the two 01 isolates carried an identical large number of copies of cholera toxin gene in their chromosomes. Finally, the outer-membrane protein profiles of strains MO 1 and M0477 were identical to those of 0 139 isolates but were different from those displayed by strains 569B and MAK757.
Journal of Medical Microbiology 01/1995; 42(1):20-25. DOI:10.1099/00222615-42-1-20 · 2.25 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Vibrio cholerae phage φ l49 codes tRNAs specific for twelve different amino acids. These tRNA genes are contained in two different HindIII
fragments 11 and 3.4 kb in size, of the phage genome. The 3.4 kb HindIII fragment was cloned inEscherichia coli using pBR328 as vector. The recombinant plasmid pNR347 produced nine of the twelve tRNA species (arginine, proline, serine,
tyrosine, histidine, lysine, leucine, tryptophan and aspartic acid) encoded in the phage genome.
Journal of Biosciences 06/1993; 18(2):195-205. DOI:10.1007/BF02703116 · 2.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A collection of Vibrio cholerae non-O1 isolated from the aquatic environs of Calcutta, a cholera-hyperendemic area, were examined for the production of cholera toxin (CT), Shiga-like toxins (Vero toxins), heat-stable enterotoxin, and hemolysins. Two (0.5%) V. cholerae non-O1 isolates produced CT. The DNA from both these isolates also hybridized with a DNA probe containing sequences encoding the A subunit of CT. None of the strains produced Shiga-like toxins or heat-stable enterotoxin. Hemolytic activity was observed in 89.7% of the strains, of which 36.1% exhibited biological activity in the suckling mouse. However, none of them produced a hemolysin that cross-reacted with the thermostable direct hemolysin of Vibrio parahaemolyticus. It appears from this study that a small percentage of environmental V. cholerae non-O1 strains do possess the potential for causing cholera-like diarrhea.
Applied and Environmental Microbiology 01/1989; 54(12):3180-2. · 3.67 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Non-pathogenic, environmental strain ofVibrio cholerae, ELTOR Ogawa EW6 carries a copy of the cholera toxin gene in its chromosome. Restriction enzyme digestion followed by Southern
blot analysis revealed that the structure of the cholera toxin gene in this organism is different from that found in the virulent
strains. The xbaI site which has been found to be conserved in the cholera toxin of the virulent strains examined so far,
is absent here. Results of the RNA dot blot analysis indicated that the cholera toxin gene in EW6 is transcribed much less
efficiently compared to the cholera toxin gene present in the virulent strainVibrio cholerae classical Inaba 569B.
Journal of Biosciences 03/1987; 11(1):231-238. DOI:10.1007/BF02704673 · 2.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Two lines of evidence suggest that a gene analogous to the recA gene of Escherichia coli exists in Vibrio cholerae and that its product serves a proteolytic function in the SOS response. Firstly, Southern blot hybridization using the recA gene of E. coli as a probe revealed a genomic sequence in V. cholerae which hybridized with the probe. Secondly, the SOS-like response in V. cholerae (as measured by beta phage induction) triggered by DNA damaging agents like Furazolidone could be blocked by Antipain, a protease inhibitor known to inhibit RecA protease action in E. coli. Maximal blocking effect of Antipain on beta phage induction occurred at 1 mM. At this concentration neither the viability of the host bacterium nor the lytic growth of a clear plaque mutant of the phage was affected by Antipain.
MGG - Molecular and General Genetics 02/1985; 200(3):439-41. DOI:10.1007/BF00425728