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H N Williams

Publications and source records attributed to H N Williams.

At least 19 recordsLinked to original sources
PubMed2000

A proposal for the reclassification of Bdellovibrio stolpii and Bdellovibrio starrii into a new genus, Bacteriovorax gen. nov. as Bacteriovorax stolpii comb. nov. and Bacteriovorax starrii comb. nov., respectively.

Bdellovibrios are unique bacteria with the ability to prey upon a wide variety of susceptible Gram-negative bacteria. Micro-organisms exhibiting this trait have been included in the genus Bdellovibrio despite their isolation from diverse habitats and relatively unstudied taxonomic relatedness. In this study, 16S rDNA sequences were compared from known terrestrial Bdellovibrio species, Bdellovibrio bacteriovorus 100T, Bdellovibrio stolpii Uki2T and Bdellovibrio starrii A3.12T in order to study their phylogenetic relationship. The two sequences from B. stolpii Uki2T and B. starrii A3.12T were 90.0% similar to each other but exhibited only 81.7% and 81.2% similarity, respectively to B. bacteriovorus 100T. Phylogenetic analysis indicated that B. bacteriovorus 100T clustered in a separate clade from B. starrii A3.12T and B. stolpii Uki2T, demonstrating only a distant relationship between B. bacteriovorus 100T and the other two recognized type species. DNA-DNA hybridization experiments also demonstrated <4% hybridization between these three species. On the basis of the results obtained from the phylogenetic analysis and DNA-DNA hybridization studies, it is proposed that B. stolpii Uki2T and B. starrii A3.12T should be transferred to a new genus, Bacteriovorax gen. nov. as Bacteriovorax stolpii comb. nov. and Bacteriovorax starrii comb. nov., respectively. It is also proposed that the type species for the new genus Bacteriovorax should be Bacteriovorax stolpii comb. nov.

Base Composition↗
PubMed1997

Effects of temperature, salinity, and substrate on the colonization of surfaces in situ by aquatic bdellovibrios.

Recent studies suggest that surfaces are a more conducive habitat than the water column for the proliferation of bdellovibrios in the aquatic environment. The effect of temperature and salinity on the colonization of bdellovibrios on oyster shell, glass, and polystyrene surfaces in situ was investigated over an annual cycle. Sterile surfaces were suspended in various bodies of water for intervals ranging from 24 to 120 h. The results revealed that bdellovibrios associated with different types of surfaces over a broad temperature and salinity range. After 24 h of submersion in waters with temperatures from 9.0 to 26.7(deg)C, the ranges in log(inf10) values per square centimeter for the three surfaces were as follows: oyster shell, 2.2 to 2.5; glass, 0.3 to 2.2; and polystyrene, 0.7 to 1.6. Bdellovibrios were not recovered from surfaces submerged in water at temperatures below 8(deg)C during the 120-h experimental cycle. The number of bdellovibrios and culturable bacteria on oyster shells was significantly higher than the numbers on glass and polystyrene at all time intervals. The number of bdellovibrios was positively correlated with temperature and salinity on all surfaces. A positive correlation between the number of recoverable bacteria and temperature was observed, but the results with respect to salinity were diverse. The numbers of bdellovibrios recovered from oyster shells (up to 48 h) and water samples were significantly increased at salinities greater than 11(permil) compared to those in lower-salinity environments. The results of this study reveal that like many other bacteria in the aquatic environment, bdellovibrios prefer to associate with surfaces. This association provides the predators a rich source of prey bacteria in surface biofilms and perhaps protection in the gel-like matrix of the biofilm.

Journal Article↗
PubMed1996

Molecular techniques reveal high prevalence of Legionella in dental units.

Legionella bacteria are ubiquitous in freshwater aquatic systems, and humans are infected by them primarily through inhalation of contaminated aerosols. This study analyzed a total of 47 water samples from dental lines in private dental offices and university and hospital dental clinics for Legionella using the polymerase chain reaction, direct fluorescent antibody staining and culture techniques. The typical temperature of dental waterlines (23 C) combined with Legionella's ability to form biofilms, stagnation of the water in the lines and a low chlorine residual all potentially create a unique niche for this microorganism.

Colony Count, Microbial↗
PubMed1995

Bacterial succession within a biofilm in water supply lines of dental air-water syringes.

Biofilms have been implicated as reservoirs for bacterial contamination of water delivered by dental air-water syringes. A 6-month study was done of bacterial colonization and biofilm formation in plastic water supply lines connected to dental air-water syringes. Changes in biofilm flora were observed by both scanning electron microscopy and bacteriologic culture. By day 7, many rod- and spiral-shaped bacteria had colonized the ridged surface of the luminal wall of the tubing, as revealed by scanning electron microscopy. By day 30, individual microcolonies were embedded in extracellular polymeric material. By day 120, these microcolonies had begun to coalesce, and by day 180 the biofilm had developed into a multilayered, heterogeneous mixture of microcolonies. The mean aerobic plate counts of colony-forming units of planktonic and biofilm populations were, in log10 values, 5.9 +/- 0.54/mL and 4.2 +/- 0.82/cm2, respectively. Early colonizers were predominantly Pseudomonas spp., but included Pasteurella, Moraxella, Ochrobactrum, and Aeromonas spp. Flavobacterium and Acinetobacter spp. were observed later. Many of these organisms are opportunistic pathogens. These results demonstrate the longitudinal dynamics of biofilm formation.

Biofilms↗
PubMed1995

Contribution of biofilm bacteria to the contamination of the dental unit water supply.

The authors studied the contribution of bacterial biofilm to the contamination of the dental unit water supply, as well as the effects of flushing and sodium hypochlorite treatment on reducing the number of contaminants. This study demonstrated that biofilm in the dental tubing was the primary source of contaminated water delivered by dental units.

Biofilms↗
PubMed1995

Bacterial contamination of the water supply in newly installed dental units.

Bacterial contamination of the water supply of newly installed dental units was investigated. Water samples were collected from water supply lines to the dental operatories prior to connection of the dental units. Within hours following connection, and continuing for up to the 6 months of the study, water samples were obtained from the air-water syringe of the units. The samples were serially diluted 10-fold and plated on culture media for quantitative analysis. The formation of bacterial biofilm in the dental water supply tubing was monitored by scanning electron microscopy. The results of these studies revealed that the building's water supply to the dental units was contaminated prior to connection to the units. The water supply from the air-water syringe was therefore contaminated as well. The number of contaminant bacteria in the dental unit water supply increased for several weeks and then stabilized. The lumen of the dental tubing became progressively contaminated with bacterial biofilm, which subsequently became the primary reservoir for maintenance of the contamination of the dental unit water supply.

Bacteria↗
PubMed1994

Evaluation and use of a low nutrient medium and reduced incubation temperature to study bacterial contamination in the water supply of dental units.

A low nutrient medium, dilute peptone, and reduced incubation temperatures (25 or 30 degrees C) were used to recover bacteria from dental unit water supply. Significantly greater numbers of bacterial colony-forming units were recovered on the dilute peptone medium than on the enriched media, blood agar or trypticase soy agar. Lower incubation temperatures yielded greater numbers of colony-forming units on all media. The bacterial population in dental unit water supply following stagnation in the supply lines and flushing of the lines was studied using dilute peptone incubated at 25 degrees C. No significant differences in the numbers of colony-forming units were found in stagnant water versus fresh water. Flushing the water lines for 10 min did not significantly reduce the numbers of colony-forming units.

Agar↗
PubMed1992

Bdellovibrios in Callinectus sapidus, the Blue Crab.

Bdellovibrios were recovered from the gill tissue of all of 31 crabs sampled and from all samples of epibiota obtained from the ventral shell surface of 15 crabs. The results suggest that the blue crab is a reservoir for bdellovibrios. The association with crabs may be an important factor in the ecology of the bdellovibrios.

Journal Article↗
PubMed1991

Serogrouping of halophilic bdellovibrios from chesapeake bay and environs by immunodiffusion and immunoelectrophoresis.

Little has been reported on the serological relationship of halophilic bdellovibrios (Bd). Immunodiffusion analysis performed with rabbit or mouse Bd antisera developed against eight halophilic Bd isolates and one terrestrial Bd isolate, when reacted with soluble antigen preparations of 45 isolates of halophilic Bd, allowed separation into seven serogroups, which were distinct from the terrestrial isolate. Soluble antigen preparations of prey bacteria, Vibrio parahaemolyticus P-5 (P-5) and Escherichia coli ML 35 (ML 35), exhibited no reactivity with the antisera by immunodiffusion. Immunoelectrophoresis revealed the presence of three distinct antigens in homologous reactions and one shared antigen in heterologous Bd reactions. Shared antigens were noted between halophilic and terrestrial Bd, in addition to between halophilic Bd strains, indicating the possible existence of an antigen(s) which may be shared among all Bd. Again, no shared antigen was noted when P-5 or ML 35 was allowed by immunoelectrophoresis to react with the antisera. Prey susceptibility testing of the seven distinct groups of halophilic Bd, using 20 test prey, produced essentially identical spectra for each group, indicating that this was not a useful technique in delineating the Bd. While immunoelectrophoresis was able to demonstrate an antigen common to all Bd tested, immunodiffusion was able to delineate strains on the basis of a "serogroup specific" antigen. This suggests that immunological tools may serve as important means to study the taxonomy of halophilic Bd, as well as in the formation of a clearer taxonomic picture of the genus Bdellovibrio.

Journal Article↗
PubMed1991

Factors affecting the stability of sodium hypochlorite solutions used to disinfect dental impressions.

Increased concern over the transmission of acquired immunodeficiency syndrome, hepatitis B, herpes, and other diseases has prompted research into the disinfection of dental impressions. Among the factors to be considered when dental impressions are disinfected is the stability of the disinfectant solutions during storage and use. This study is concerned with the effect on disinfectant solutions of repeated immersion of alginate dental impressions taken in metal trays. The effects of the impression materials, metal trays, and dilution were evaluated, and the impact of light, heat, and storage were also addressed. The findings indicated that in the test solutions, although considerable chlorine was consumed during the disinfection procedures, bactericidal activity was maintained, while in the control solution both chlorine content and bactericidal activity were remarkably stable.

Dental Impression Materials↗
PubMed1990

Efficiencies of recovery of bdellovibrios from brackish- water environments by using various bacterial species as prey.

A total of 44 bacterial species subdivided into 10 trial experiments have been used as prey for the recovery of bdellovibrios from samples of water from a brackish tidal pond and an aquarium saltwater tank. In an initial investigation, the recovery efficiency of each of the test bacterial species was compared with that of a designated standard prey, Vibrio parahaemolyticus P-5. The results revealed that in each case strain P-5 yielded an equal or significantly greater number of plaques of bdellovibrios than the test prey with but a single exception, strain CS5. In repeat experiments, CS5 yielded fewer plaques than P-5. To determine whether the use of multiple bacterial species compared with a single species as prey would increase the number of PFU of bdellovibrios recovered, material from plaques appearing on each of the test prey in the respective trials was sequentially subcultured onto two respective agar plates, the first containing as prey V. parahaemolyticus P-5 and the second containing the initial test organism. In nearly every case, subculture of plaques from lawns of the test prey to P-5 resulted in plaque formation. On the basis of the results, the use of several test prey and P-5 did not result in the recovery of any more bdellovibrio PFU than the use of P-5 alone. In this study, V. parahaemolyticus P-5 was observed to be the most efficient prey for the recovery of bdellovibrios from moderate salt water.

Journal Article↗
PubMed1989

Multi-centre clinical trial of nedocromil sodium in reversible obstructive airways disease in adults: a general practitioner collaborative study.

The efficacy of nedocromil sodium (2 x 2 mg puffs twice a day) was assessed in a multi-centre, double-blind parallel group placebo-controlled study of 159 adult patients with chronic reversible obstructive airways disease. Over two-thirds of the patients had been maintained on or used an inhaled bronchodilator prior to the study. During a 4-week baseline period, patients stopped using their current respiratory therapy, with the exception of oral bronchodilators, and were established on a maintenance regimen of inhaled salbutamol (2 puffs 4-times daily with additional doses as needed). Patients then received either nedocromil sodium or placebo in place of the maintenance salbutamol regimen and inhaled salbutamol was allowed only on an as needed basis during a 12-week double-blind period. Daily diary records were made by patients of symptom severity, morning and evening peak expiratory flow rate, and salbutamol usage. The doctor assessed overall severity of the patient's condition at 4-weekly intervals, and both patients and doctor assessed treatment effectiveness at the end of the trial. Total symptom severity (night-time symptoms, morning tightness and daytime symptoms) was reduced and morning and evening PEFR improved throughout in the nedocromil sodium-treated patients, although evening PEFR returned nearly to the baseline in the final 4 weeks of the study. The reduction in combined day and night-time inhaled bronchodilator use from the baseline was significantly greater in the nedocromil sodium-treated patients and these patients were significantly (p less than 0.05) improved compared to the placebo-treated patients on each of the three occasions that the physicians assessed disease severity. Of the 40 patients withdrawn during the double-blind period of the study (26 on nedocromil sodium, 14 on placebo), 9 and 7 patients, respectively, were withdrawn because of the onset of uncontrolled asthma, and 4 and 2 patients, respectively, because of suspected adverse reactions to treatment. A total of 21 patients treated with nedocromil sodium recorded unusual symptoms (9 commented on taste, 5 had nausea and vomiting) compared with 16 patients on placebo. Overall, nedocromil sodium was considered to be moderately or very effective in at least 50% of the patients, although no significant differences were seen between treatments in either the patients' or physicians' assessment.

Administration, Inhalation↗
PubMed1986

The isolation of fungi from laboratory dental pumice.

Samples of used dental laboratory pumice from the two dental laboratories were cultured for the isolation of fungi. The resulting supernatant fluid from sedimentation of each pumice sample after suspension in sterile saline was serially diluted and plated onto Sabouraud agar. After incubation, fungal colonies observed were enumerated, isolated, and identified. The mean number of fungal colonies recovered from 10 pumice samples in laboratories I and II was 51.0 X 10(2) and 22.6 X 10(2), respectively. In both laboratories the predominant fungi recovered were Aspergillus niger and Fusarium sp. Other fungi recovered included Cephalosporium and Penicillium species and A. flavus. Many of these organisms have been involved in human disease. It is suggested that the presence of fungi in used dental laboratory pumice presents an unhygienic condition in the dental laboratory and may place dental laboratory technicians and denture patients at increased risk of fungal sensitization and disease.

Aspergillus niger↗
PubMed1984

Distribution of bdellovibrios in the water column of an estuary.

The distribution of bdellovibrios in the water column of the Miles River has been studied. Water samples were collected every 4 h over a 24-h period from five depths in the water column. The samples were cultured for the recovery of bdellovibrios lytic against Vibrio parahaemolyticus. Environmental parameters, i.e., salinity, temperature, turbidity, and dissolved oxygen (DO) were measured for each sample. Bdellovibrios were observed to be uniformly distributed at all depths measured in the water columns. There were no significant differences between the number of bdellovibrios recovered at the various depths. There were significant differences between the number of bdellovibrios recovered at various sampling times. However, no basis for these significant differences could be established. No association was found between the number of bdellovibrios recovered and the environmental parameters measured. Of interest was the observation that the distribution of the aerobic bdellovibrios did not correlate with DO measurements. The results suggest that neither depth nor DO content influenced the recovery of bdellovibrios from the Miles River.

Bdellovibrio↗
PubMed1983

Acinetobacter contamination of laboratory dental pumice.

Micro-organisms of the genus Acinetobacter, implicated as opportunistic pathogens, have been recovered from dentures after laboratory repair. A study was undertaken to determine if Acinetobacter could be isolated from used dental pumice. Cultural studies demonstrated that Acinetobacter calcoaceticus variety lwoffi was present in high numbers in used pumice and was a major gram-negative microbial contaminant.

Acinetobacter↗