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J B Kaper

Publications and source records attributed to J B Kaper.

211 records · Page 12Linked to original sources
PubMed1982

Molecular epidemiology of Vibrio cholerae in the U.S. Gulf Coast.

Enterotoxigenic strains of Vibrio cholerae O-1, biotype El Tor, isolated from a case of cholera in Texas in 1973, an outbreak of cholera in Louisiana in 1978, and Louisiana sewage samples in 1980 and 1981 were analyzed for their genetic similarities. Chromosomal DNA was isolated from each strain, digested with restriction endonuclease, and analyzed by the Southern blot technique. A radioactive probe consisting of Escherichia coli heat-labile enterotoxin DNA detected cholera toxin gene sequences in these strains and demonstrated that the toxin gene sequence, if not the entire chromosomal DNA, is identical in these strains and distinctly different from other strains of V. cholerae isolated throughout the world. In addition, two strains of enterotoxigenic V. cholerae non-O-1 isolated from clinical cases, were analyzed and found to possess cholera toxin genes which differed in the DNA sequence from the V. cholerae O-1 strains. We concluded that a single strain of enterotoxigenic V. cholerae O-1 is resident in the U.S. Gulf Coast and that a second reservoir of cholera toxin genes exists in V. cholerae non-O-1 strains in Louisiana.

Cholera↗
PubMed1982

Vibrio parahaemolyticus and related halophilic Vibrios.

Approximately 30 years have elapsed since Dr. Fujino's original discovery that Vibrio parahaemolyticus (then termed Pasteurella parahemolytica) was the cause of "summer diarrhea" in Japan. Since that finding, V. parahaemolyticus has been established as a cause of gastroenteritis in numbers and places approaching global proportions. It has been isolated in marine and estuarine areas almost worldwide and despite its halophilic nature, V. parahaemolyticus has been isolated from saline-free waters. The relationship of this organism to the environment reveals a close association with other marine organisms especially copepods on which the Vibrios depend for survival in winter months and growth in summer months. There is a uniquely provocative disparity between human strains of V. parahaemolyticus which are Kanagawa phenomenon (KP) positive and the environmental strains which to a large extent are KP negative, the significance being that pathogenicity is measured according to the Kanagawa phenomenon (hemolytic activity) reaction. The hemolysin of the pathogenic strains is a thermostable, cardiotoxic protein, which thus far has not been implicated in the mechanism(s) which causes human gastroenteritis. The interest in this organism has been widened in recent years by the finding that similar organisms, V. alginolyticus, lactose positive vibrios and group F vibrios also cause serious disease in humans.

Animals↗
PubMed1981

Molecular characterization of environmental and nontoxigenic strains of Vibrio cholerae.

Environmental and nontoxigenic strains of Vibrio cholerae 0-1 were examined for genes homologous to genes encoding Escherichia coli heat-labile enterotoxin (LT). Restriction fragments encoding LT A and B subunits were isolated from the recombinant plasmid EWD299 and labeled in vitro with 32P. These probes were then hybridized to deoxyribonucleic acid extracted from strains of V. cholerae and visualized by autoradiography. None of the nontoxigenic strains of V. cholerae 0-1 from Louisiana, Alabama, Maryland, Guam, Brazil, Bangladesh, or Great Britain hybridized with the LT probes, whereas all toxigenic strains exhibited homology. In addition, strains of V. cholerae non-0-1, "group F" vibrios, V. vulnificus, and Aeromonas hydrophila were tested, and all were negative except two strains of V. cholerae non-0-1. The presence of plasmids did not correlate with toxigenicity or nontoxigenicity in any of the species examined. Thus, it appears that these strains are not simple nontoxigenic mutants, but rather do not possess any genetic material encoding cholera toxin. Such strains therefore cannot revert and serve as a reservoir of cholera.

Cholera Toxin↗
PubMed1980

Isolation of drug-resistant Aeromonas hydrophila from aquatic environments.

Antibiotic-resistant strains of Aeromonas hydrophila have been isolated from the natural environment in the Chesapeake Bay and areas surrounding Dacca and the Matlab region of Bangladesh. The Bangladesh strains carried resistance to chloramphenicol, streptomycin, and tetracycline, and 57% of them had a multiple streptomycin-tetracycline resistance phenotype correlated with the presence of a large plasmid. The Chesapeake Bay strains were resistant to polymyxin B ane tetracycline, but showed neither multiple resistance nor R-factor carriage. Twenty-five percent of the environmental strains were toxigenic in a Y-1 adrenal cell assay. Toxigenicity showed no positive correlation with drug resistance or with plasmid carriage. Environmental areas of heavy human impact appear to be associated with a higher incidence of antibiotic-resistant strains of aeromonads.

Aeromonas↗
PubMed1980

R-factor carriage in a group F vibrio isolated from Bangladesh.

Two group F vibrio organisms have been identified among a collection of vibrio strains isolated from the aquatic environment in Bangladesh. Neither group F strain produced a cholera-like enterotoxin. One of the isolates, BV12, contained an R plasmid conferring resistance to streptomycin and chloramphenicol.

Aeromonas↗
PubMed1978

Evaluation of the accuracy and precision of enumerating aerobic heterotrophs in water samples by the spread plate method.

Factors associated with accuracy and precision in the enumeration of aquatic aerobic heterotrophs by the spread plate method were evaluated by using a nested analysis of variance experimental design. Variances associated with individual components of the spread plate procedure were isolated, and optimal replications of each step were allocated. A practical scheme for optimal allocation of resources is proposed, consisting of four subsamples and two plates per subsample and yielding a total variance decrease of 70% from a single-subsample, 10-plate series. Data transformation was, in general, unnecessary for intraexperiment or intrasample statistical analysis, whereas interexperiment or intersample comparisons may require transformation of data. Rapid changes in the numbers of organisms in stored water samples were observed that were not reproducible and did not follow detectable trends, with increases or decreases in counts occurring in samples regardless of whether they were stored at room temperature or refrigerated, or stored in plastic or glass containers. Rapid sample handling is strongly recommended to minimize variations in the microbial populations of samples for aquatic environments.

Journal Article↗
PubMed1977

Ambient-temperature primary nonselective enrichment for isolation of Salmonella spp. from an estuarine environment.

A primary, nonselective, ambient-temperature enrichment procedure for isolation of Salmonella spp. is described. The procedure was superior to elevated-temperature selective enrichment for Salmonella when estuarine water samples were examined. Five Chesapeake Bay stations were monitored, over an 8-month period, for the presence of salmonellae. Of 72 water and sediment samples collected, 17 (23.6%) yielded Salmonella spp. Seven serotypes were identified among the isolates. A seasonal pattern was noted for the incidence of the salmonellae. A most probable number procedure, performed by membrane filtration and nonselective enrichment, yielded Salmonella most probable number indices as high as 110 per 100 g of sediment. The results suggest that new methods, such as the one described in this report, are required for isolation of human intestinal pathogens from estuaries and coastal waters.

Bacteriological Techniques↗
PubMedDate not supplied

Recombinant attenuated Vibrio cholerae strains used as live oral vaccines.

Although great strides have been made in the development of recombinant attenuated Vibrio cholerae vaccine strains, the task has not been as simple as once imagined. The initial vaccine candidates proved to be unexpectedly reactogenic but further derivatives, such as CVD103-HgR, are well-tolerated, immunogenic and protective after a single dose. In addition, this strain carries a selectable marker to distinguish it from wild strains and has been evaluated in a practical, lyophilized formulation (Levine et al., 1988b). While CVD103-HgR is being further evaluated in expanded trials, we are also investigating a new secretogenic factor which could possibly explain the diarrhoea seen with the earlier vaccine strains. Hopefully, these studies will achieve the long-sought goal of a safe and effective vaccine for the prevention of cholera.

Administration, Oral↗
PubMedDate not supplied

Recombinant nontoxinogenic Vibrio cholerae strains as attenuated cholera vaccine candidates.

An ideal vaccine does not yet exist to prevent cholera, a significant health problem in many less developed countries. Vibrio cholerae, the agent of epidemic and endemic cholera, colonizes the small bowel and secretes a potent enterotoxin that consists of a single A subunit, which stimulates adenylate cyclase activity, and five identical B subunits which bind to the ganglioside GM1 receptor of intestinal mucosal cells. Previous studies in man indicate that toxoid-derived antitoxic immunity by itself is insufficient to provide effective, long-lasting protection against cholera. Using recombinant DNA techniques we have now constructed a live, attenuated V. cholerae strain by deleting genes encoding the enterotoxin. Restriction enzyme fragments encoding cholera toxin were deleted in vitro from cloned vibrio chromosomal DNA and the resulting mutations introduced into the chromosome of a vibrio strain of proven immunogenicity. Recently, Mekalanos and coworkers have reported attenuated V. cholerae strains constructed by similar methods. It appears that recombinant DNA techniques offer a promising approach to the development of effective cholera vaccines.

Cholera Vaccines↗
PubMedDate not supplied

Vibrio cholerae vaccines.

Several approaches to the development of a safe and effective vaccine against Vibrio cholerae are currently being pursued. These candidate vaccines include (1) live V. cholerae strains attenuated by recombinant DNA techniques; (2) killed whole V. cholerae organisms plus purified cholera enterotoxin B subunit; and (3) cloned V. cholerae antigens in a Salmonella carrier strain. The first two approaches have been the most extensively studied in clinical trials, and all three types of vaccines are administered orally to maximize the stimulation of mucosal immunity. The live attenuated vaccine CVD103-HgR is inexpensive and was effective after a single dose but caused mild diarrhea in 4% of vaccinees. The killed whole cell plus B subunit vaccine is safe but requires the administration of multiple doses. The strong protective immunity conferred by the disease and the rapid progress recently achieved in vaccine development offer encouragement that a successful vaccine will soon be available.

Cholera Vaccines↗