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Biomedical subjects

G S Hall

Publications and source records attributed to G S Hall.

At least 37 records · Page 2Linked to original sources
PubMed1997

Absence of skin alkaloids in captive-raised Madagascan mantelline frogs (Mantella) and sequestration of dietary alkaloids.

Mantelline frogs of the genus Mantella contain a variety of pumiliotoxin, allopumiliotoxin and homopumiliotoxin alkaloids in their skin. Pyrrolizidines, indolizidines and quinolizidines are also present. In contrast, captive-raised frogs (Mantella aurantiaca) have no alkaloids detectable in skin extracts. Frogs fed alkaloid-dusted fruit flies accumulate alkaloids into their skin. Thus, these mantelline frogs, like the neotropical dendrobatid frogs, appear dependent on dietary sources for their skin alkaloids and have the requisite alkaloid-sequestering system(s).

Alkaloids↗
PubMed1996

The emergence of Neisseria gonorrhoeae with decreased susceptibility to ciprofloxacin in Cleveland, Ohio: epidemiology and risk factors.

BACKGROUND: Until 1992, almost all strains of Neisseria gonorrhoeae that had been tested in the United States were susceptible to fluoroquinolones, including ciprofloxacin. However, among men with urethral gonococcal infections who attended one sexually transmitted disease clinic in Cleveland, Ohio, the prevalence of gonococci with decreased susceptibility to ciprofloxacin increased from 2% in 1991 to 16% in 1994. OBJECTIVE: To describe the emergence of and risk factors for gonococcal urethritis caused by gonococci with decreased susceptibility to ciprofloxacin. Resistance to ciprofloxacin was considered to be decreased if the mean inhibitory concentration was at least 0.12 microgram/mL, and was less than or equal to 0.25 microgram/mL; this definition did not equate with the definition of clinical resistance. DESIGN: Case-control study. SETTING: An urban sexually transmitted disease clinic. PARTICIPANTS: 51 case-patients and 106 controls. MEASUREMENTS: Pulsed-field gel electrophoresis was used to identify individual genotypes of ciprofloxacin-resistant and ciprofloxacin-susceptible isolates. RESULTS: 55 of the 746 isolates of N. gonorrhoeae that were tested (7.4%) had decreased susceptibility to ciprofloxacin, and the prevalence of N. gonorrhoeae with decreased susceptibility significantly increased during the study period. Case-patients were significantly less likely to have gram-negative diplococci seen on microscopic examination of urethral discharge (P < or = 0.01) and were less likely to be treated for gonococcal urethritis than were controls (P < or = 0.001). Molecular typing suggested the spread of a single genotype of N. gonorrhoeae. CONCLUSIONS: Strains of gonococci with decreased susceptibility to ciprofloxacin appear to have become endemic in Cleveland, Ohio. The clinical significance of these isolates is not clear, but the potential for the emergence of clinically important resistance may preclude the use of fluoroquinolones as an alternative treatment for uncomplicated gonorrhea.

Anti-Infective Agents↗
PubMed1996

Impact of chlorhexidine-silver sulfadiazine-impregnated central venous catheters on in vitro quantitation of catheter-associated bacteria.

To assess the impact of the antiseptic effects of silver sulfadiazine-chlorhexidine-impregnated central venous catheters on catheter culture systems, a series of in vitro experiments was performed. Segments of antiseptic and non-antiseptic-impregnated catheters were sonicated in thioglycolate broth and removed. After the addition of 10(3) CFU of Staphylococcus epidermidis per ml, aliquots of catheter-exposed broth were subcultured onto blood agar at 15-min intervals. Decreased mean colony counts were noted at 45 min for broth exposed to antiseptic-impregnated catheters compared with the colony counts for broth exposed to non-antiseptic-impregnated catheters (170 versus 540 CFU/ml). These effects, which were also demonstrated by the roll-plate method, were abrogated by the use of medium containing inhibitors of silver sulfadiazine and chlorhexidine. To assess the duration of the antiseptic effects, catheter segments were suspended for up to 14 days in phosphate-buffered saline, incubated with 10(6) CFU of S. epidermidis per ml, and cultured. Inhibition of bacterial growth by antiseptic-impregnated catheters disappeared after 14 days. These studies suggest that antiseptic compounds elute from catheters during broth- and solid medium-based culturing processes, making necessary the addition of inhibitors of these compounds in culture media. They further suggest that the antimicrobial effects of antiseptic-impregnated catheters wane within several days of placement.

Anti-Infective Agents, Local↗
PubMed1996

Bacterial contamination of anaerobic vitreous cultures: using techniques employed for endophthalmitis.

PURPOSE: To investigate the occurrence of contaminated cultures of vitreous specimens from non-infected eyes obtained using anaerobic techniques employed for endophthalmitis. METHODS: Vitreous specimens were obtained using meticulous sterile techniques employed for endophthalmitis from seventeen patients undergoing pars plana vitrectomy for non-infective indications: vitreous hemorrhage (12 eyes), retinal detachment (3), Coat's disease (1), and congenital dislocated lens(1). Vitreous specimens were inoculated in the operating room onto an anaerobic blood agar plate and into thioglycolate broth. Bacterial growth occurring before 10 days was considered positive. RESULTS: Three organisms were isolated from three separate eyes. One colony of Staphylococcus species was isolated on an anaerobic blood agar plate on day 3. A single colony of Propionibacterium acnes grew on an anaerobic blood agar plate on day 6. Alpha-hemolytic streptococci grew from thioglycolate broth on day 10. CONCLUSIONS: Growth as detected in this study might represent contaminating rather than an infecting organism in an eye suspected of having endophthalmitis.

Adult↗
PubMed1996

Primary processing of specimens and isolation and cultivation of mycobacteria.

Processing of specimens for mycobacteria need to proceed as rapidly as possible to provide 24 hour turnaround for smears and 21-day turnaround for the identification of Mycobacterium tuberculosis. If these goals are to be accomplished, a broth culture or microcolony plate method must be part of the media and in the planting process. Use of conventional solid media alone does not provide adequate turnaround time.

Bacteriological Techniques↗
PubMed1995

Minimum bactericidal concentrations of Propionibacterium acnes isolates from cases of chronic endophthalmitis.

Six isolates of Propionibacterium acnes recovered from cases of chronic infectious endophthalmitis following extracapsular cataract extraction were tested for antibiotic susceptibility. All isolates were susceptible to penicillin, cefazolin, and vancomycin with a macrobroth dilution method. Minimum bactericidal concentrations testing at 72 h revealed that six of six isolates were killed by < or = 1.0 micrograms of vancomycin/ml, one of six isolates by < or = 1.0 micrograms of penicillin/ml, and zero of six isolates by < or = 1.0 micrograms cefazolin/ml.

Anti-Bacterial Agents↗
PubMed1995

Deep tissue infections caused by Scopulariopsis brevicaulis: report of a case of prosthetic valve endocarditis and review.

Scopulariopsis brevicaulis is a saprophytic fungus that commonly causes onychomycosis but rarely causes deep tissue infection. To the best of our knowledge, this is the first reported case of endocarditis caused by S. brevicaulis. The infection persisted despite two aortic valve replacements, debridement, and prolonged therapy with several antifungal agents. The patient eventually died due to an acute myocardial infarction caused by ongoing prosthetic valve endocarditis. We review case reports of deep tissue infections due to Scopulariopsis species.

Aged↗
PubMed1995

Case report of Streptomyces endocarditis of a prosthetic aortic valve.

We describe the first case of prosthetic valve endocarditis due to a Streptomyces sp. The patient presented with fever, cutaneous embolic lesions, and bacteremia 3 months after aortic valve replacement. Treatment required valve replacement and a long course of parenteral imipenem.

Aortic Valve↗
PubMed1995

Symptomatic Mycobacterium avium complex infection of the central nervous system. A case report and review of the literature.

Mycobacterium avium complex infections rarely involve the central nervous system, even in patients with widely disseminated disease. We report a case of disseminated M. avium complex infection presenting with central nervous system symptoms in a patient with Hodgkin's disease. Neurologic findings included disorientation, nuchal rigidity, seizures, an extensor plantar response, cerebrospinal fluid studies consistent with meningitis, and eventually, coma and death. Organisms of the M. avium complex were cultured from several sites. Histopathologically, the central nervous system lesions consisted of small aggregates of lymphocytes and macrophages containing acid-fast organisms present in a predominantly perivascular location. In view of the life-threatening nature and potential treatability of this uncommon presentation of M. avium complex infection, we suggest that these organisms be sought in immunocompromised patients presenting with unexplained central nervous system symptoms.

Adult↗
PubMed1994

Clinical comparison of the Baxter MicroScan Yeast Identification Panel and the Vitek Yeast Biochemical Card.

To determine the reliability of the Baxter MicroScan Yeast Identification Panel, processed by the Walkaway-96, and the Vitek Yeast Biochemical Card, 150 clinical yeast isolates (30 Candida albicans, 67 Candida species, not albicans, 26 Torulopsis glabrata, 13 Cryptococcus neoformans, 4 Saccharomyces cerevisiae, 6 Trichosporon beigelii, 3 Rhodotorula species, and 1 Geotrichum species) were tested on both systems. Results were compared with those obtained by the API 20C and the appearance of yeast cells on cornmeal Tween-80 agar. After inoculation of each system, results were available in 4 hours with MicroScan panels, 24-48 hours with Vitek cards, and 72 hours with the API 20C strips. On initial testing, 101 (67%) and 128 (85%) isolates, respectively, were correctly identified by MicroScan and Vitek. After repeat testing, the number of correctly identified isolates increased to 123 (82%) by MicroScan and to 142 (95%) by Vitek. Yeasts most commonly misidentified were Candida tropicalis, T glabrata, and Candida parapsilosis by MicroScan and C tropicalis and T glabrata by Vitek.

Mycology↗
PubMed1994

Growth curve for Propionibacterium acnes.

We established growth curves for Propionibacterium acnes isolates recovered from eyes with chronic postoperative endophthalmitis. The growth curve plotted the average of the duplicate bacterial concentration against time. The generation time for P. acnes calculated from the growth curves was approximately 5.1 hours. The growth of P. acnes is slower than other anaerobic bacteria. This may account for its delayed appearance in culture of ocular specimens. It may also explain treatment failure if the concentration of an antibiotic injected into the vitreous does not remain at an effective level during the critical replicative phase of the organism.

Cataract Extraction↗
PubMed1993

Comparison of vidas Clostridium difficile toxin-A assay and premier C. difficile toxin-A assay to cytotoxin-B tissue culture assay for the detection of toxins of C. difficile.

Damage to the intestinal mucosa by Clostridium difficile (CD) is toxin mediated. Two enzyme immunoassays (EIAs) for toxin-A detection, the automated Vitek immunodiagnostic assay system CDA (Vidas CDA), and the Premier toxin A (Premier) were tested for their ability to detect toxin A in 301 stool samples and compared with an in-house tissue culture assay for toxin B (TCA). Of these 301 samples, 49 were TCA positive and 252 were TCA negative. Agreement between Vidas CDA and TCA on the initial run was 85% (255 of 301) and increased to 94% (278 of 296) when discordant samples were retested from available frozen specimens. Corresponding levels of agreement for Premier were 91% (272 of 301) and 98% (284 of 288), respectively. If tissue culture positivity at any titer was used as the sole criterion for positivity of the specimen, agreement with positive TCA before and after repeat testing was 57% (26 of 49) and 74% (34 of 46) for Vidas CDA and 65% (32 of 49) and 95% (36 of 38) for Premier. Agreement with negative TCA titers was good: 90% for Vidas CDA and 95% for Premier, and 98% for Vidas CDA and 99% for Premier after repeat testing. Predictive values positive and negative after repeat testing were, respectively, 88% and 96% for Vidas CDA, and 95% and 99% for Premier. Results for the automated and manual EIA methods for detection of C. difficile toxin A were obtained in 2.5 h as compared with 36-48 h for tissue culture.

Bacterial Proteins↗
PubMed1993

Aberrant Histoplasma capsulatum. Confirmation of identity by a chemiluminescence-labeled DNA probe.

A cottony, light tan, filamentous fungus with pear-shaped microconidia and lacking tuberculated macroconidia was isolated from a bronchial lavage specimen. Subculture on several media at 37 degrees C failed to convert the fungus to a yeast form after several weeks; attempts at in vivo conversion in mice were also unsuccessful. Sera obtained several months apart showed M bands with Histoplasma capsulatum (HC) antigen by immunodiffusion and an increase in complement fixation titers with mycelial and yeast phase antigens of HC. Parallel identity was obtained on two occasions with exoantigen culture confirmation reagents for HC from Immuno-Mycologics as well as one of identity with Nolan reagents. Extracts from four Chrysosporium spp. strains had no identity reactions with HC with either kit. The fungus was identified as HC by the Accuprobe Histoplasma chemiluminescence-labeled DNA probe directed at ribosomal RNA, whereas all four Chrysosporium spp. isolates tested negative. DNA probes are a fast and accurate method to confirm the identity of aberrant fungal isolates.

Aged↗
PubMed1993

Unpredictability of commercially available exoantigen culture confirmation tests in confirming the identity of five Blastomyces dermatitidis isolates.

Colonial and microscopic features of five fungal isolates from three patients suggested Blastomyces dermatitidis. Extracts from the mold forms of all isolates were tested on several occasions with commercially available Exoantigen immunodiffusion culture-confirmation test reagents and Nolan reagents. All three isolates from patient 1 were negative on four separate attempts with Exoantigen reagents using conventional ("slant") and "broth" extraction methods, and were also negative on one attempt with the Nolan reagents. The isolate from patient 3 was negative on three attempts using both reagent kits. The isolate from patient 2 was negative on four of five attempts with Exoantigen test reagents and positive on one attempt with Nolan reagents. Commercially prepared chemiluminescence-labeled DNA probes (Gen-Probe, San Diego, CA) directed at ribosomal RNA from B. dermatitidis and Histoplasma capsulatum confirmed all five isolates as B. dermatitidis. The cost and labor of the exoantigen and DNA Probe culture confirmation tests were evaluated. New methods for confirming the identity of cultural isolates of B. dermatitidis that are sensitive, specific, and commercially available are greatly needed.

Antigens, Fungal↗
PubMed1993

Quantitative and Qualitative Analysis of Bacteria in Er(III) Solution by Thin-Film Magnetopheresis.

Magnetic deposition, quantitation, and identification of bacteria reacting with the paramagnetic trivalent lanthanide ion, Er, was evaluated. The magnetic deposition method was dubbed thin-film magnetopheresis. The optimization of the magnetic deposition protocol was accomplished with Escherichia coli as a model organism in 150 mM NaCl and 5 mM ErCl(3) solution. Three gram-positive bacteria, Staphylococcus epidermidis, Staphylococcus saprophyticus, and Enterococcus faecalis, and four gram-negative bacteria, E. coli, Pseudomonas aeruginosa, Proteus mirabilis, and Klebsiella pneumoniae, were subsequently investigated. Quantitative analysis consisted of the microscopic cell count and a scattered-light scanning of the magnetically deposited material aided by the computer data acquisition system. Qualitative analysis consisted of Gram stain differentiation and fluorescein isothiocyanate staining in combination with selected antisera against specific types of bacteria on the solid substrate. The magnetic deposition protocol allowed quantitative detection of E. coli down to the concentration of 10 CFU ml, significant in clinical diagnosis applications such as urinary tract infections. Er did not interfere with the typical appearance of the Gram-stained bacteria nor with the antigen recognition by the antibody in the immunohistological evaluations. Indirect antiserum-fluorescein isothiocyanate labelling correctly revealed the presence of E. faecalis and P. aeruginosa in the magnetically deposited material obtained from the mixture of these two bacterial species. On average, the reaction of gram-positive organisms was significantly stronger to the magnetic field in the presence of Er than the reaction of gram-negative organisms. The thin-film magnetophoresis offers promise as a rapid method for quantitative and qualitative analysis of bacteria in solutions such as urine or environmental water.

Journal Article↗
PubMed1993

Probe technology for the clinical microbiology laboratory.

Molecular-based techniques, such as use of genetic probes, can greatly reduce turnaround time of the identification of some isolates in the clinical microbiology laboratory. For example, culture confirmation of an acid-fast bacillus such as Mycobacterium tuberculosis or Mycobacterium avium-intracellulare by a gene probe can be performed within hours of the isolation of the organism. Conventional methods might require more than 2 to 4 weeks for this identification. Identification of a mold, such as Histoplasma capsulatum, with a gene probe, can be done in less than 24 hours, with minimal growth available; conventional fungal identification takes 1 to 2 weeks or more. Whether a probe is used in the clinical microbiology laboratory depends on a number of factors including accuracy of the probe, cost, commercial availability, and ease of performance. In addition, the relevance of a more rapid result needs to be considered. A gene probe may be more specific than conventional methodologies, and this may increase its advantage. Direct specimen testing with probes is presently hampered by inadequate sensitivities. Prior amplification may decrease this limitation. It is hoped that methods will be available in the near future that provide amplification and probing of clinical specimens for laboratory diagnosis to be made within a short time following specimen collection.

Animals↗