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Biomedical subjects

J D Oliver

Publications and source records attributed to J D Oliver.

At least 91 records · Page 5Linked to original sources
PubMed1986

Plasmid carriage in Vibrio vulnificus and other lactose-fermenting marine vibrios.

A total of 42 clinical and environmental isolates of Vibrio vulnificus were examined for plasmid carriage. Of these, only five (12%) harbored plasmids, which were of various molecular weights. In contrast, 20 of 32 (62.5%) unidentified lactose-fermenting Vibrio spp. were found to possess plasmids with masses of 2.1 to 150 megadaltons. In these isolates, multiple plasmids were common, with an average of 2.25 plasmids per plasmid-containing strain. Attempts to demonstrate a correlation with the plasmids identified in the various Vibrio spp. and a variety of phenotypic traits, production of several enzymes potentially involved in virulence, cytotoxicity for Chinese hamster ovary cells, and mouse lethality were unsuccessful. A correlation was observed, however, between the presence of a 6.5-megadalton plasmid and resistance to pteridine 0/129. It was concluded that V. vulnificus, unlike most other Vibrio spp., shows a general lack of these extrachromosomal elements.

Animals↗
PubMed1984

Cryosensitivity of Escherichia coli and the involvement of cyclopropane fatty acids.

Strains of Escherichia coli proficient and deficient in cylopropane fatty acid synthesis were compared for fatty acid content, cryosensitivity, presence of freeze-thaw-induced wall and membrane damage, resistance to detergent-stimulated lysis and tolerance to salt and detergents during growth. The mutant populations synthesized much less cyclopropane fatty acids and were more resistant than the wild type to freezing and thawing in saline only, exhibiting less viability loss and less wall and membrane damage. While the resistance of the mutants to NaCl was unaltered, their detergent resistance was decreased under both growth and non-growth conditions. Although these physiological changes were associated with a lower cyclopropane fatty acid content in the mutant strains, it is proposed that the responses were due to the altered membrane fluidity of the mutants due to changes in their unsaturated fatty acid content.

Cyclopropanes↗
PubMed1984

Lipid Composition of a Psychrophilic Marine Vibrio sp. During Starvation-Induced Morphogenesis.

Qualitative and quantitative changes with time in phospholipids and fatty acids were examined after suspension of cells of a psychrophilic marine bacterium in nutrient-free artificial seawater at 5 degrees C. Viability was maintained throughout the 21-day examination period, with plate counts and acridine orange direct counts indicating a slight increase in cell number. Gravimetric data, however, showed a significant decrease in bacterial biomass during the 3-week study. Levels of ATP per cell also decreased significantly (59%) during the starvation period. Since starvation (resulting in dormancy) is probably the typical physiological state of marine bacteria, estimation of bacterial density in marine waters by using ATP data obtained from log-phase cells is probably inaccurate. Total lipid phosphate decreased (65%) during the starvation period, with phosphatidylethanolamine showing the greatest loss. A large increase (57%) in the neutral lipid fraction was also detected, especially during the first week of starvation. A selective increase in palmitoleate at the expense of myristate was detected in the membrane lipids. The effects of these changes on membrane fluidity and the possible consequences for these cells in the marine environment are discussed.

Journal Article↗
PubMed1984

Substrate degradation and pressure tolerance of free-living and attached bacterial populations in the intestines of shallow-water fish.

Bacterial populations attached to intestinal linings of shallow-water fish were compared to those free in the lumen for response to hydrostatic pressure and ability to degrade a variety of substrates. Results suggested that, unlike reports on gut-associated deep-sea bacteria, the two shallow-water populations were not significantly different in their pressure or substrate responsiveness.

Journal Article↗
PubMed1984

Role of heme compounds and haptoglobin in Vibrio vulnificus pathogenicity.

An induced peritonitis model was employed in mice to determine whether heme-containing molecules enhance the lethality of infections by Vibrio vulnificus. The lethality of intraperitoneal (ip) inocula of the bacteria was increased by concurrent injections (ip) of hemoglobin, methemoglobin, or hematin, but not by myoglobin. Similar results were obtained in mice with phenylhydrazine-induced hemoglobinemia, in which after ip injections of V. vulnificus, a direct correlation between lethality and levels of plasma hemoglobin was observed. In vitro studies indicated that the growth of V. vulnificus, which was limited in an iron-poor medium, was enhanced by the addition of hemoglobin in a manner similar to an inorganic iron source, ferric ammonium citrate. These results suggest that V. vulnificus is capable of extracting iron from hemoglobin for use as a nutrilite, thereby promoting growth and increased lethality in the in vivo models. Further studies with human serum cultures demonstrated that the growth of V. vulnificus was not decreased when hemoglobin added to the serum was completely complexed with haptoglobin; these results are in opposition to those with cultures of Escherichia coli. These results are discussed relative to the capacity of V. vulnificus to produce fatal human infections.

Animals↗
PubMed1983

Distribution of Vibrio vulnificus and other lactose-fermenting vibrios in the marine environment.

During the summer of 1981, 3,887 sucrose-negative vibrios were isolated from seawater, sediment, plankton, and animal samples taken from 80 sites from Miami, Fla., to Portland, Maine. Of these, 4.2% were able to ferment lactose. The lactose-positive strains isolated from the various samples correlated positively with pH and turbidity of the water, vibrios in the sediment and oysters, and total bacterial counts in oysters. Negative correlations were obtained for water salinity. Numerical taxonomy was performed on 95 of the lactose-fermenting environmental isolates and 23 reference strains. Five clusters resulted, with the major cluster containing 33 of the environmental isolates and all of the Vibrio vulnificus reference strains. The 33 isolates, which produced an acid reaction in lactose broth within hours of initial inoculation, represented 20% of all lactose-fermenting vibrios studied. These isolates were nearly identical phenotypically to clinical strains of V. vulnificus studied by the Centers for Disease Control, Atlanta, Ga., and by our laboratory, and their identification was confirmed by DNA-DNA hybridization studies. V. vulnificus was isolated from all sample types and from Miami to Cape Cod, Mass., and comparison of the environmental parameters of the eight subsites yielding this species with those of all 80 subsites revealed no significant differences. The majority of the isolates were obtained from animals, with clams providing most (84%) of these. On injection into mice, 82% of the V. vulnificus isolates resulted in death. Members of the remaining four clusters contained strains which differed from V. vulnificus in such phenotypic traits as luminescence and in urease or H(2)S production. None of the other reference cultures, including nine other Vibrio species, were contained in the remaining clusters, and these isolates could not be identified. Most of these were also lethal for mice. Phenotypic differences, potential pathogenicity, and geographic distribution of the five clusters were examined. It is concluded that V. vulnificus is a ubiquitous organism, both geographically and in a variety of environmental sources, although it occurs in relatively low numbers. The public health significance of this organism and of the other unidentified lactose-fermenting Vibrio species is discussed.

Fermentation↗
PubMed1983

Siderophore production by Vibrio vulnificus.

Previous studies in our laboratory, as well as clinical evidence, have suggested that increased iron levels in the host may be important in infections caused by the halophilic pathogen Vibrio vulnificus. To study iron acquisition, we induced siderophore production by growth in a low-iron medium, and biochemical testing indicated the production of both hydroxamate- and phenolate-type siderophores. The siderophores were extracted from growth filtrates with ethyl acetate (for phenolates) and phenol-chloroform-ether (for hydroxamates). These extracts enhanced the growth of V. vulnificus when the bacterium was grown in iron-limited medium. The ability of these siderophores to stimulate the growth of Salmonella typhimurium LT-2 enb-7 (a mutant deficient in the biosynthesis of enterochelin) and Arthrobacter flavescens JG-9 (a hydroxamate auxotroph) supported the conclusion that V. vulnificus produces both hydroxamate- and phenolate-type siderophores.

Arthrobacter↗
PubMed1982

Distribution and ecology of Vibrio vulnificus and other lactose-fermenting marine vibrios in coastal waters of the southeastern United States.

Water, sediment, plankton, and animal samples from five coastal sites from North Carolina to Georgia were sampled for their lactose-fermenting vibrio populations. Over 20% of all vibrios tested were sucrose negative and o-nitrophenyl-beta-D-galactopyranoside (ONPG) positive, suggesting identification as the human pathogen Vibrio vulnificus. These vibrios were isolated from all sample sites and sources (water, sediment, plankton, and animals). Correlations with several of 19 environmental parameters monitored at each site were found for total vibrios. The presence of ONPG-positive, sucrose-negative vibrios was correlated with hydrocarbon levels in the water and, in the case of plankton samples, with salinity. A total of 279 sucrose-negative, ONPG-positive isolates were subjected to numerical taxonomic analysis, which resulted in three major clusters. Cluster I corresponded to and included 11 reference strains of V. vulnificus. Cluster II contained the largest number (133) of isolates, of which the great majority were bioluminescent. Although having a resemblance to V. harveyi, the isolates were ONPG positive and many were H2S positive. Cluster III consisted of strains similar to the group F vibrios (V. fluvialis). Of all of the isolates, 55% were luminescent, of which over 20% were lethal when injected into mice. Problems involved in detecting lactose fermentation among marine vibrios and the potential pathogenicity of these organisms are discussed.

Animals↗
PubMed1981

Lethal cold stress of Vibrio vulnificus in oysters.

Studies were conducted on the survival of Vibrio vulnificus, an estuarine human pathogen, in oyster homogenates held at 4 degrees C. Results indicated a rapid and dramatic decrease in viability not attributable to either cold shock or the oyster homogenate alone but to a combination of the two. Such a decline was not observed with Vibrio parahaemolyticus. Chilled V. vulnificus cells were unable to repair themselves in brain heart infusion broth at 37 degrees C. V. vulnificus cells incubated on whole raw oysters at 0.5 degrees C also exhibited a decline in viability, but of a lesser degree. The effects of various plating media were also investigated. The data reported here suggest that oysters kept on ice are not likely to be a major factor in the epidemiology of V. vulnificus infection. It is further suggested that the standard method of homogenizing oysters for examining bacteriological quality should not be followed because toxic compounds are released from the oysters during this process.

Animals↗
PubMed1981

Edema and hemoconcentration in mice experimentally infected with Vibrio vulnificus.

Vibrio vulnificus (lactose-positive Vibrio), a recently recognized pathogenic marine species, produced extreme hemoconcentration and death within 3 to 6 h after subcutaneous or intraperitoneal injection of 10(8) viable cells into mice; hemotocrit values approached 70% (normal, 45%). About 1 ml of edema fluid accumulated at the site of each subcutaneous injection, and locally increased vascular permeability was demonstrated by a skin bluing assay, using Evans blue dye. A corresponding fluid accumulation did not occur in the peritoneal cavity after an intraperitoneal injection. Filter-sterilized supernatants of cultures grown under a variety of conditions did not produce local edema or lethality, nor did whole Vibrio cells killed by a variety of methods or disrupted by sonic oscillation. Edema fluids collected from infected mice and sterilized by filtration had no effect when they were injected subcutaneously or intraperitoneally into mice. Inocula of 10(9) viable cells of V. vulnificus contained within a diffusion chamber implanted subcutaneously did not produce skin bluing, edema, or lethality; Vibrio cells remained viable and virulent within these chambers for at least 2 weeks. These experiments suggested that vascular permeability changes in V. vulnificus infections may not be attributable to a diffusible toxin and may require direct contact between host cells and viable Vibrio cells.

Animals↗
PubMed1981

Role of iron in the pathogenesis of Vibrio vulnificus infections.

Infections with Vibrio vulnificus resulting in septicemia and high mortality have been correlated with pre-existing liver disease and hemochromatosis. As these conditions are associated with impaired iron metabolism and as iron availability in the host has been implicated in the pathogenicity of a number of bacterial infections, the role of iron as a possible factor in the pathogenesis of V. vulnificus was examined. Injection of mice with iron resulted in a lowering of the 50% lethal dose from 10(6) to 1.1 cells and in a reduction in the time of death postinfection. Elevated serum iron levels were also produced by damaging livers with injections of CCl4. The inoculum size required to kill these mice was directly correlated with serum iron levels. Since the portal of infection of this organism may be ingestion of contaminated seafood, the effects of iron upon orally induced infection were also studied. The effects of adding iron, transferrin, or Desferal (an iron chelate) upon the growth of V. vulnificus in human and rabbit sera were also examined. Iron appeared to be the limiting factor in the ability of this organism to survive or grow in mammalian sera. These results, both in vitro and in vivo, provided strong evidence that iron may play a major role in the pathogenesis of V. vulnificus.

Animals↗
PubMed1978

Experimental pathogenicity and mortality in ligated ileal loop studies of the newly reported halophilic lactose-positive Vibrio sp.

Laboratory animals were challenged subcutaneously, intraperitoneally, and intravenously with the halophilic lactose-positive Vibrio. Intraperitoneal inocula of 10(8) organisms proved to be rapidly lethal in mice, rats, and hamsters. The 50% lethal doese in ICR strain mice was estimatd to be 8 X 10(5) live cells, injected intraperitoneally or subcutaneously. Subtaneous inocula in mice resulted in severe local infections, characterized by gross edema, and for those animals surviving longer than 48 h, tissue necrosis. Intravenous, intraperitoneal, and subcutaneous injections of 10(8) cells in mice resulted in death within 3 to 6 h. These animals rapidly developed Vibrio bacteremia after injections. V. parahaemolyticus, studied for comparative purposes, produced no morbidity or mortality when injected subcutaneously. Injections of live lactose-positive Vibrio into ligated ileal loops in rats and rabbits consistently proved to be lethal with a high-density bacteremia resulting.

Animals↗
PubMed1974

Computer program designed to follow fluctuations in microbial populations and its application in a study of Chesapeake Bay microflora.

A computer program has been developed which performs cluster analysis of microorganisms using methods of numerical taxonomy. The program is designed to group related strains, identify the groups by reference to known strains, and calculate a hypothetical median organism (HMO) for each group. The HMO serves to condense taxonomic information and provides a tag for each strain cluster. Every strain in a group is compared with the HMO established for that group. A representative strain for the group is obtained by selection of the strain showing highest similarity to the HMO. New data sets can be compared with data sets of previous analyses. Hence, the occurrence of the same taxonomic groups within separate data sets can be determined. Quantitative or qualitative differences in distribution of taxonomic groups within or between data sets can be measured. The output from the computer is a graphical display, using an on-line plotter; thus, the investigator is provided with visual comparison of data sets. Results obtained from a study applying the computer program in an analysis of taxonomic data obtained for 43 bacterial strains isolated from Chesapeake Bay indicate the usefulness of this method of taxonomic analysis in microbial ecology.

Bacteria↗
PubMed1973

Extractable lipids of gram-negative marine bacteria: phospholipid composition.

Phospholipid compositions of 20 strains of marine and estuarine bacteria were determined. Results showed that phospholipids of marine bacteria differed very little from those of nonmarine organisms with phosphatidylethanolamine, phosphatidylglycerol, and diphosphatidylglycerol being the predominant phospholipids in all strains examined. Lyso-phosphatidylethanolamine occurred in significant quantities among a number of the marine bacteria, and two of the isolates contained significant quantities of poly-beta-hydroxybutyrate. Effects of age and growth temperature on the phospholipid composition were also investigated. It is suggested that phylogenetic relationships among bacteria may be correlated with phospholipid composition.

Age Factors↗