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Biomedical subjects

D G Ahearn

Publications and source records attributed to D G Ahearn.

At least 73 records · Page 4Linked to original sources
PubMed1988

Incidence and persistence of Pseudomonas aeruginosa in whirlpools.

Pseudomonas aeruginosa was isolated from seven commercial and two residential whirlpools that were treated with halogens. None of the commercial whirlpools was constantly maintained at appropriate disinfection levels. Superchlorination or the draining, cleaning, disinfection, and refilling of whirlpools markedly reduced densities of P. aeruginosa in whirlpool water, but the bacterial populations were rapidly reestablished (less than 10(3) cells per ml) when disinfectant concentrations decreased below recommended levels (chlorine, 3.0 ppm [3.0 micrograms/ml]; bromine, 6.0 ppm). P. aeruginosa in the water was replenished from various sources, such as hoses used to fill the whirlpool and the biofilm in the filter and piping of the whirlpool systems. Daily monitoring and adjustment of chemical characteristics (regardless of bather load) were essential for controlling densities of P. aeruginosa.

Bromine↗
PubMed1987

Physical and biological parameters that determine the fate of p-chlorophenol in laboratory test systems.

Shake-flask and microcosm studies were conducted to determine the fate of para-chlorophenol (p-CP) in water and sediment systems and the role of sediment and nonsediment surfaces in the biodegradation process. Biodegradation of p-CP in estuarine water samples in shake flasks was slow over incubation periods of 300 h. The addition of detrital sediment resulted in immediate and rapid degradation evidenced by the production of 14CO2 from [14C]p-CP. The addition of sterile sediment, glass beads, or sand resulted in approximately four to six times more CO2 evolution than observed in the water alone. Densities of p-CP-degrading bacteria associated with the detrital sediment were 100 times greater than those enumerated in water. Bacteria in the water and associated with the sediment after preexposure of both water and sediment of p-CP demonstrated enhanced biodegradation. In some microcosms, p-CP was degraded completely in the top 1.0 cm of intact sediment beds. Sediment reworking activities by benthic invertebrates from one site were sufficient to mix p-CP deep into the sediment bed faster than biodegradation or molecular diffusion. p-CP was persistent at lower depths of the sediment, possibly a result of reduced oxygen conditions preventing aerobic biodegradation.

Bacteria↗
PubMed1987

Adherence of Pseudomonas aeruginosa to hydrophilic contact lenses and other substrata.

Nonmucoid Pseudomonas aeruginosa isolated from corneal ulcers and contact lens cases and solutions were examined for their ability to adhere to polystyrene, glass, and hydrophilic contact lenses of varying water content and polymer composition. Adherence to the various substrates was strain specific. Adherence also was influenced by hydrophobicity and chemical composition of the substratum, as well as pH and electrolyte concentration. An extracellular polymeric adhesive appeared to be involved in the firm attachment of cells to soft contact lenses.

Bacterial Adhesion↗
PubMed1987

Association of Pseudomonas and Serratia corneal ulcers with use of contaminated solutions.

The wetting and soaking solutions and contact lens cases of eye clinic patients commonly were contaminated with gram-negative bacteria during their use. Serratia marcescens occurred most frequently in preserved solutions, whereas Pseudomonas aeruginosa was most often recovered from home-prepared saline. The bacteria were recovered at densities of greater than 10(6) cells per ml and typically persisted in the solutions. Eight patients who developed bacterial keratitis during 1986 used solutions contaminated with the etiological agents of the infections. Improper hygienic practices of the patients and failure of some preservative systems were implicated in the development of the infections.

Adult↗
PubMed1986

Association of fungi with extended-wear soft contact lenses.

Fungi were isolated from 11 extended-wear soft contact lenses. In two cases, fungi had penetrated through the contact lens and the same fungus was cultured from corneal ulcers. In four cases, fungal growth on and in the soft contact lens matrix was associated with conjunctivitis and punctate fluorescein staining of the corneal epithelium.

Contact Lenses↗
PubMed1986

High-performance liquid chromatography of mycolic acids as a tool in the identification of Corynebacterium, Nocardia, Rhodococcus, and Mycobacterium species.

High-performance liquid chromatography of bromophenacyl esters of mycolic acid was used as an aid to assign a particular organism to one of four mycolic acid-containing genera. A gradient elution system, with methanol and chloroform, was used to distinguish representative mycolic acid patterns for the genera Corynebacterium, Rhodococcus, Nocardia, and Mycobacterium.

Actinomycetales↗
PubMed1986

Morphology and ultrastructure of fungi in extended-wear soft contact lenses.

Filamentous fungi of the genera Acremonium, Aspergillus, Alternaria, Cladosporium, Curvularia, and Fusarium penetrated the matrix of soft contact lenses both during normal usage and in laboratory studies. Growth of the fungi within the lens matrix increased with increasing water content of the lens. Hyphae within the lens were coiled. Some species penetrated completely through the lens within 96 h. More frequent cleaning and disinfection of extended-wear soft contact lenses is recommended.

Acremonium↗
PubMed1986

Antibiograms, serotypes, and plasmid profiles of Pseudomonas aeruginosa associated with corneal ulcers and contact lens wear.

Pseudomonas aeruginosa was isolated from the corneal scrapings of 11 of 14 patients with gram-negative corneal ulcers and from salt tablet-prepared saline solutions from 6 of these patients wearing soft contact lenses. Comparison of physiological properties, antibiograms, serotypes, and plasmid profiles for five of the patients indicated that the isolates from the ulcer and the saline solution of a given patients were of the same strain. Improper hygienic practices of contact lens wearers appeared to be a major factor in the epidemiology of pseudomonad corneal ulcers.

Adult↗
PubMed1985

Antimicrobial activities of N-chloramines and diazolidinyl urea.

A combination of MICs of an N-chloramine, a simple chlorinated amino acid, and diazolidinyl urea gave synergistic activity against bacteria, but not fungi. The two compounds at a higher concentration, 0.1 and 0.3%, respectively, gave synergistic inhibition of fungi; kill times were 1 h for Trichophyton tonsurans, 3 h for Aspergillus niger and Fusarium moniliforme, and 6 h for Aspergillus fumigatus.

Anti-Infective Agents, Local↗
PubMed1984

In vitro susceptibilities of sucrose-negative Candida tropicalis, Candida lusitaniae, and Candida norvegensis to amphotericin B, 5-fluorocytosine, miconazole, and ketoconazole.

The MICs and minimal lethal concentrations of four antimycotics, amphotericin B, 5-fluorocytosine, miconazole nitrate, and ketoconazole, were determined for 25 yeast isolates representing species uncommonly implicated in candidiasis. A microdilution procedure was employed with complex and synthetic media. The isolates, in general, were susceptible to the same antimicrobial agents shown to be effective against Candida albicans, but differences between some of the species in relative susceptibilities to the antifungal agents were noted. Isolates of atypical sucrose-negative Candida tropicalis were similar in their susceptibility patterns to typical isolates of the species. Relative resistance to amphotericin B, miconazole nitrate, and ketoconazole was noted for two Candida lusitaniae isolates, but all strains were susceptible to 5-fluorocytosine. Candida norvegensis isolates were more resistant to miconazole and ketoconazole than C. albicans clinical isolates. The microtiter system was satisfactory for determining minimal inhibitory concentrations, but the system is not recommended for detecting finite differences in drug susceptibilities or for detecting drug synergism.

Amphotericin B↗
PubMed1984

Disseminated candidiasis caused by a sucrose-negative variant of Candida tropicalis.

A patient suffering from leukemic transformation of a non-Hodgkin's lymphoma developed fatal disseminated candidiasis caused by a sucrose-negative variant of Candida tropicalis. The results of histopathological tests showed massive tissue invasion in many organs. The course of infection and the tissue morphology of the etiological agent were indistinguishable from those of C. albicans and typical C. tropicalis strains.

Abscess↗
PubMed1983

Candida ciferrii and Candida chiropterorum isolated from clinical specimens.

Ten clinical yeast isolates submitted to the Centers for Disease Control from diverse geographic areas were identified as Candida ciferrii and Candida chiropterorum. The association of C. ciferrii with clinical specimens, particularly its repeated isolation from a case of onychomycosis, suggests that this species may be an etiological agent of superficial yeast infections.

Adult↗
PubMed1982

Characterization of atypical Candida tropicalis and other uncommon clinical yeast isolates.

Clinical yeast isolates representing alpha-glucoside-deficient variants of Candida tropicalis, C. lusitaniae, atypical C. albicans, and Saccharomyces cerevisiae were characterized. Additional physiological tests, including cellobiose fermentation, rhamnose assimilation, and triphenyl tetrazolium chloride reduction, are recommended for the detection and presumptive identification of uncommon Candida spp. in the clinical laboratory.

Candida↗
PubMed1981

Pseudomonas corneal ulcers associated with soft contact-lens wear.

Seven Pseudomonas corneal ulcers in six patients were associated with soft contact-lens wear and use of saline solutions prepared from distilled water and sodium chloride tablets. The same species of Pseudomonas isolated from the corneal ulcers were also isolated from the home-prepared saline and in one instance from the water used to prepare the saline solution. In three of the six patients, the pseudomonad isolated from the corneal ulcer was of the same serotype and biochemically identical to the pseudomonad from the patients' saline solution. Commercially available distilled water, even brands recommended for use with soft contact lenses, was found to be contaminated with gram-negative bacteria before use. Clinical histories disclosed that all patients inappropriately used the home-prepared saline as a wetting agent, or eyedrop, or bath, after thermal disinfection of the contact lens. Self-inoculation of the eye with contaminated saline is a hazard for soft contact-lens wearers who use home-prepared saline solution.

Adolescent↗
PubMed1981

Serotyping Cryptococcus neoformans by immunofluorescence.

Four serotypes of Cryptococcus neoformans designated A, B, C, and D are currently recognized. Although an agglutination test is most often used to serotype C. neoformans in cultures, this test is not appropriate for typing the fungus in fixed tissues. A study to prepare fluorescent-antibody reagents for typing C. neoformans in cultures and to determine whether they can be used to type this fungus in fixed tissues was carried out. Antisera to one strain belonging to each of the four serotypes were prepared in rabbits by intravenous injection of whole Formalin-killed cryptococci. Each antiserum was labeled with fluorescein isothiocyanate and then adsorbed with cells of each of the heterologous serotypes. The adsorbed conjugates were then tested against six serotype A isolates and five isolates of each of the other three serotypes. Labeled serotype A or D antiserum adsorbed with either B or C cells stained the A and D, but not the B or C, isolates. Labeled serotype B antiserum adsorbed with A cells stained the B and C, but not the A or D, isolates. Labeled A antiserum absorbed with D cells differentiated A from D; labeled C antiserum absorbed with B cells differentiated C from B. Of the 21 test isolates, 17 could be serotyped in paraffin sections of tissues of experimentally infected mice.

Animals↗
PubMed1980

Loss of effectiveness of preservative systems of mascaras with age.

The preservative systems of unused, anhydrous mascaras were challenged periodically with microorganisms, using a modified membrane procedure. Shelf life of preservative activity against Pseudomonas aeruginosa varied for different brands from as little as 1 month to over 36 months. Generally, P. aeruginosa grew in mascaras after the mascaras were challenged first with Staphylococcus epidermidis or Candida albicans.

Candida albicans↗
PubMed1979

Evaluation of industrial yeasts for pathogenicity.

Eleven yeasts representative of species of industrial interest were compared with Candida albicans for their potential pathogenicity for untreated and cortisone-treated mice. Only C. tropicalis produced a progressive infection similar to that produced by C. albicans. Candida lipolytica, Torulopsis spp., and Hansenula polymorpha were not recovered from mice 6 days after inoculation. Kluyveromyces fragilis, C. pseudotropicalis, C. utilis, C. guilliermondii and C. maltosa were recovered from mice but did not produce evidence of infection.

Animals↗