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Biomedical subjects

G J Dixon

Publications and source records attributed to G J Dixon.

At least 19 recordsLinked to original sources
PubMed1987

Effect of vidarabine in dimethyl sulfoxide vehicle on type 1 herpesvirus-induced cutaneous lesions in laboratory animals.

Vidarabine (9-beta-D-arabinofuranosyladenine) prepared in a 70% dimethyl sulfoxide vehicle was applied topically to type 1 herpesvirus-induced cutaneous lesions on guinea pigs and athymic nude mice. Treatments were 3 or 5 times daily for 7 days beginning 24 h after virus exposure. Against infections in guinea pigs induced by a thymidine kinase-positive virus strain, either treatment schedule effectively inhibited mean lesion score, lesion size, appearance of new lesions, and reduced lesion virus titers. Therapy was similarly effective against infections in guinea pigs induced by a thymidine kinase-negative virus strain, except that lesion virus titers were somewhat increased in animals treated 3 times daily. Treatment 5 times daily was most efficacious against both virus strains. Treatment 3 times daily of mice infected with a thymidine kinase-negative virus was not effective, but treatment 5 times daily significantly inhibited lesion score and size and reduced lesion virus titer by 37%. Toxicity controls exhibited no signs of skin irritation, although guinea pigs treated 5 times daily experienced some transient weight loss.

Animals↗
PubMed1975

Disk diffusion and serial dilution tests of susceptibility of some pathogenic gram-negative bacilli and enterococci to carbenicillin and ampicillin.

Tests for susceptibility to ampicillin and carbenicillin were performed with 35 strains each of Klebsiella, Enterobacter, Serratia, and Proteus, 71 strains of Pseudomonas aeruginosa, and 68 strains of enterococci by serial dilution and disk-diffusion tests employing 10(-3) dilutions of overnight cultures as inocula for both. Commercial 10-mug ampicillin and 50- and 100-mug carbenicillin disks, and freshly prepared 10-, 50-, and 75-mug ampicillin and 10- and 50-mug carbenicillin disks were used. Results were displayed as cumulative distribution curves for both minimal inhibitory concentrations and zone diameters, and as scattergrams for correlating them. Differences in susceptibility to the two antibiotics were small for Klebsiella, Enterobacter, and Serratia and large for the others. The freshly prepared and commercial disks of the same content gave comparable zones. There was good correlation of zone diameter with each disk and the minimal inhibitory concentration. Among the ampicillin disks tested, none was useful for Pseudomonas; with the other species, the 10-mug disk, as well as those with higher ampicillin content, could discriminate susceptible from resistant strains. However, only the 75-mug disk selected some Klebsiella strains susceptible to high concentrations. The 50- and 100-mug carbenicillin disks were equally discriminating for most strains, but the higher concentration was more selective for Klebsiella. The 10-mug carbenicillin disk was as effective as the 50- and 100-mug disks for discriminating among Enterobacter, Serratia, Pseudomonas, and Proteus, but not for Klebsiella or enterococci. The 10(-3) inoculum gave zone sizes considerably larger than those reported by other workers who used the standard Kirby-Bauer method.

Ampicillin↗
PubMed1971

Quantitative studies on fabrics as disseminators of viruses. V. Effect of laundering on poliovirus-contaminated fabrics.

The effects of laundering with both anionic and nonionic detergents in cold, warm, and hot water on poliovirus-contaminated cotton sheeting, cotton terry cloth, washable wool shirting, wool blanketing, dull nylon jersey, and dacron/cotton shirting were determined. The fabrics were exposed to virus by aerosolization and direct contact (pipette) in separate studies. Although the results varied with each factor used in the study, virus titers on all the fabrics were generally reduced considerably by the laundering process. When the fabrics were dried for 20 hr after laundering, an additional decline in virus titers was seen, often to below detectable levels. The type of detergent used made little difference in effect on virus titer reduction, but the hot wash water markedly reduced the detectable virus. Fabric type was not a major factor in the majority of the experiments, although virus tended to be eliminated more readily from the nylon jersey, and in warm water the virus persisted longer on wool blanketing material laundered in anionic detergent. Sterile fabrics of each type laundered with similar fabrics which contained virus often became contaminated by the virus during the laundering process. Virus titers ranging from undetectable to 10(3.9) cell culture 50% infectious doses/ml were obtained from samples of the rinse water after warm- and cold-water laundering.

Animals↗
PubMed1971

Potentially infectious agents associated with shearling bedpads: effect of laundering with detergent-disinfectant combinations on Staphylococcus aureus and Pseudomonas aeruginosa.

Glutaraldehyde-tanned woolskins which are used as bedpads to prevent decubitus ulcers were contaminated with Staphylococcus aureus (ATCC 6538) and Pseudomonas aeruginosa (ATCC 15442). Two methods of exposure, direct contact and aerosol, were used in separate experiments. Attempts were made to decrease the bacterial population placed on the woolskins by laundering them in a quaternary ammonium disinfectant, a phenolic disinfectant, or alkalinized glutaraldehyde, in combination with an anionic or nonionic detergent. The effect of a commercial detergent-sanitizer was also studied. Bacterial populations were significantly reduced in all experiments, but only laundering in glutaraldehyde in combination with either detergent resulted in maximum removal of bacteria. Viable bacteria were usually not detected in the rinse water (<1 viable organism/5 ml of rinse water).

Aldehydes↗
PubMed1970

Potentially infectious agents associated with shearling bedpads. I. Effect of laundering with detergent-disinfectant combinations on polio and vaccinia viruses.

Glutaraldehyde-tanned woolskin pads which are used for the prevention of decubitus ulcers in bed patients were experimentally contaminated with polio or vaccinia viruses. Two methods of exposure, direct contact and aerosol, were used in separate experiments. Attempts were made to remove or inactivate these virus contaminants by laundering the woolskins in a quaternary ammonium disinfectant, a phenolic disinfectant, or alkalinized glutaraldehyde, in combination with an anionic detergent or a nonionic detergent. The effect of a commercial detergent-sanitizer was also studied. The virus titers were significantly reduced in all experiments, but only laundering in glutaraldehyde in combination with either detergent lowered the vaccinia virus titers to below detectable limits. High concentrations of glutaraldehyde altered the texture of the wool and leather apparently by precipitating a component of the detergent onto the fibers. In all the poliovirus experiments, the virus was still detectable on either or both the wool and the leather of the pads after laundering. The rinse water from each experiment was tested for the presence of virus. No vaccinia virus was recovered, but poliovirus was demonstrated in titers up to 10(3) cell culture 50% infectious doses.

Animals↗
PubMed1970

Quantitative studies on fabrics as disseminators of viruses. IV. Virus transmission by dry contact of fabrics.

Cotton and woolen fabrics and fabrics of synthetic fibers were exposed by direct contact (pipette) and by aerosolization to poliovirus and to vaccinia virus in separate experiments, allowed to dry for 16 hr at 25 C in 35% relative humidity, and randomly tumbled with sterile swatches of the same fabrics for 30 min. By use of a HEp-2 cell assay system, up to 10(3.5) CCID(50) of poliovirus per ml and 10(4.4) CCID(50) of vaccinia virus per ml were recovered from the originally sterile fabrics as early as 1 to 10 min after contact. Maximum transfer of both viruses was achieved with wool blanket material, although high titers of vaccinia virus were recovered from all fabrics tested. Poliovirus placed on the fabrics in an aerosol tended to be transferred to the sterile fabrics at a greater rate than when it was placed on the fabrics by direct contact. The method of exposure had essentially no effect on the rate of transfer of vaccinia virus.

Aerosols↗
PubMed1969

Factors affecting the persistence of Staphylococcus aureus on fabrics.

The persistence of Staphylococcus aureus (Smith) on wool blanket, wool gabardine, cotton sheeting, cotton knit jersey, cotton terry cloth, and cotton wash-and-wear fabrics was studied. The fabrics were exposed to bacterial populations by three methods: direct contact, aerosol, and a lyophilized mixture of bacteria and dust having a high content of textile fibers. The contaminated fabrics were held in 35 or 78% relative humidities at 25 C. In general, the persistence time of S. aureus populations on fabrics held in 35% relative humidity was substantially longer when the fabrics were contaminated by exposure to aerosolized cultures or to dust containing bacteria than when contaminated by direct contact. In a 78% relative humidity, bacterial populations on the fabrics persisted for substantially shorter periods of time regardless of the mode of contamination or fabric type. Cotton wash-and-wear fabric (treated with a modified triazone resin) was the material on which populations of S. aureus persisted for the shortest time. This organism retained its virulence for Swiss mice after being recovered from wool gabardine swatches held 4 weeks in 35% relative humidity and 6 weeks in 78% relative humidity.

Animals↗
PubMed1969

Procedure for the evaluation of the virucidal effectiveness of an ethylene oxide gas sterilizer.

A quantitative, reproducible method was developed for the evaluation of the virucidal activity of test gases. Using this method, we determined the virucidal effectiveness of a Steri-Vac ethylene oxide gas sterilizer. Wool gabardine material was exposed to high concentrations of herpes simplex, vaccinia, parainfluenza, or polio viruses and was processed through the sterilizer. Two time-temperature cycles of the machine, 29 C for 180 min and 60 C for 48 min, were used in separate experiments. The viruses were exposed to the gas when freshly pipetted onto the fabric or when pipetted on the material and allowed to dry 16 to 24 hr. In two experiments carried out under each condition, the virus titers were reduced by the sterilization process to less than detectable limits. These titer reductions were for the herpes virus >/= 2.7 to 5.0 log, for vaccinia virus >/= 4.0 to 6.1 log, for parainfluenza virus >/= 1.8 to 4.9 log, and for poliovirus >/= 4.9 to 7.7 log. The observed reductions in virus titers were the same whether the virus-contaminated fabrics were sealed in polyethylene packages or held in open petri dishes during exposure to ethylene oxide.

Antisepsis↗
PubMed1969

Persistence of Salmonella typhimurium on fabrics.

The persistence of Salmonella typhimurium (V-31) on wool blanket, wool gabardine, cotton sheeting, cotton knit jersey, cotton terry cloth, and cotton wash-and-wear fabrics was studied. Three methods of exposure were employed to contaminate the fabrics: direct contact, aerosol, and a lyophilized mixture of bacteria and dust having a high content of textile fibers. After contamination, the fabrics were held in 35 or 78% relative humidity at 25 C. The persistence time of S. typhimurium on fabrics held in 35% relative humidity was substantially longer when the fabrics were contaminated by direct contact or by exposure to dust containing bacteria than when contaminated by exposure to aerosolized cultures. Viable bacterial populations persisted for 24 weeks at relatively high population densities on swatches of wool gabardine, cotton sheeting, cotton knit jersey, and cotton terry cloth exposed by direct contact and held in a humidity of 35%. In 78% humidity, bacterial populations persisted on the fabrics for relatively shorter periods of time regardless of the mode of contamination or fabric type. This organism retained its virulence for Swiss mice after being recovered from wool gabardine swatches held 8 weeks in humidities of 35 or 78% and from cotton terry cloth swatches held 6 weeks in the same humidities.

Aerosols↗
PubMed1968

Antiviral activity of carbobenzosy di- and tripeptides on measles virus.

A series of simple carbobenzoxy peptides showed high and consistent antiviral chemotherapeutic activity in cell culture. In general, greatest activity was found against the measles-distemper or herpesvirus groups, or both, but various representatives of the series had quantitatively and qualitatively different antiviral activities. Several of the compounds, showing the highest antimeasles activity, were investigated extensively. In human cell culture plaque assays, these compounds were active against measles virus at levels of from 15 to 500 mug/ml. At single doses of about 250 to 500 mg/kg, orally in three animal species, significant serum levels of drugs were detected in virus cell culture assays. The mode of action appeared to be therapeutic, as an effect was seen in cell systems infected for at least 24 hr before treatment.

Adenoviridae↗
PubMed1968

In vivo antiviral properties of biologically active compounds. II. Studies with influenza and vaccinia viruses.

The in vivo anti-influenza virus and antivaccinia virus activity of 156 biologically active compounds was determined. One of two criteria was used for evaluating activity against the influenza virus. The criteria were increase in survivor number and mean survival time, and reduction in virus-induced lung consolidation in treated, infected Swiss mice. Increase in survivor number and mean survival time were the criteria for evaluation of antivaccinia virus activity. Several drug doses were tested against two virus concentrations to demonstrate antiviral activity more clearly. Two compounds were considered significantly active against the influenza virus: DL-noformicin (NSC 72942) and amantadine hydrochloride (NSC 83653). Eleven compounds had reproducible activity against vaccinia virus: isatin-beta-thiosemicarbazone (NSC 721), 6-azauracil (NSC 3425), 9-alpha-fluoro-2alpha-methylhydrocortisone 21-acetate (NSC 12601), 5-[bis(2-chloroethyl)amino]uracil (NSC 34462), 5-iodo-2'-deoxyuridine (NSC 39661), streptonigrin (NSC 45383), N-methylisatin beta-thiosemicarbazone (NSC 69811), cytovirin (NSC 91770), 9-beta-D-arabinofuranosyladenine (NSC 404241), and 5-(mercaptomethyl)uracil (NSC 529351).

Alkylating Agents↗