Search PubMed⌕ Search

Biomedical subjects

G D Roberts

Publications and source records attributed to G D Roberts.

At least 127 records · Page 7Linked to original sources
PubMed1980

Massive antigenemia during disseminated cryptococcosis.

Three cases of disseminated cryptococcosis associated with massive levels of cryptococcal antigen in the serum and cerebrospinal fluid are presented. These patients had antigen titers of at least 1:32,768. Titers of this magnitude have not previously been reported.

Adult↗
PubMed1979

Identification of clinical isolates of mycobacteria with gas-liquid chromatography alone.

Identification of 18 mycobacterial species was performed by analysis of profiles obtained by using gas-liquid chromatography. Organisms were saponified in methanolic NaOH, and the reaction mixture was treated with BF(3) in methanol and extracted with a hexane-chloroform mixture. An identification scheme was developed from 128 stock strains and tested against a collection of 79 clinical isolates. By using gas-liquid chromatographic profiles alone, 58% of specimens were correctly identified to species level, and an additional 41% were correctly identified to a group of two or three organisms. Use in a clinical laboratory over a 2-month period proved chromatography to be as accurate as and more rapid than concurrent biochemical testing. Of 81 isolates tested, 64% were identified to species level by chromatography alone. An additional 35% were differentiated to the same groups of two or three organisms as found in our analysis of stock strains. These groups consisted of: Mycobacterium tuberculosis, M. bovis, and M. xenopi; M. avium complex, M. gastri, and M. scrofulaceum; or M. fortuitum and M. chelonei. Identification to species level from these groups could usually be done by colonial morphology alone and could always be done by the addition of one selected biochemical test. This study demonstrated the practical application of gas-liquid chromatography in the identification of mycobacteria in a clinical laboratory. In particular, all strains of M. gordonae and M. kansasii were identified to species level. M. tuberculosis was definitively identified in 85% of cases. When it could not be definitely identified, the only alternatives were M. bovis and M. xenopi, both of which are rare causes of infection.

Chromatography, Gas↗
PubMed1979

Evaluation of the modified API 20C system for identification of clinically important yeasts.

The modified API 20C system (Analytab Products, Inc.) containing 19 carbohydrate assimilation tests was used to identify stock cultures of clinical isolates and routine clinical isolates from the Mayo Clinic mycology laboratory. The system provided correct identifications for 96% of the 505 organisms tested. The API 20C represents a commercial system useful for the identification of yeasts from clinical specimens. Although reliable, it is not a complete system and must be used in conjunction with microscopic morphological features for definitive identification. Since the system requires 72 h for identification, it is not designed for the rapid presumptive identification of such organisms as Cryptococcus neoformans; other biochemical tests must be used for this purpose.

Diagnosis, Differential↗
PubMed1978

False-positive complement-fixation serology in histoplasmosis. A retrospective study.

A review of the records of 79 consecutive patients who had a positive immunodiffusion or complement-fixation test for histoplasmosis showed 28 (35%) with false-positive serologic results in relation to their clinical significance. Twelve patients (15%) had complement-fixation titers of 1:32 or greater, without cultural or histological evidence of active infection. No common clinical or laboratory finding could be correlated with the presence of false-positive tests. The latter finding correlates well with the incidence of false-positive complement-fixation titers (12%) in the normal random patient population.

Adult↗
PubMed1978

Rapid urea broth test for yeasts.

A rapid, miniaturized, urea broth test useful for detecting urease activity of yeasts was compared to Christensen urea agar. All urease-producing yeasts tested were positive on both media; however, 60% were reactive in the urea R broth within 30 min, and the remainder were reactive within 4 h. This urea multiwell test may be useful as a rapid screening method for detecting urease-producing yeasts recovered from clinical specimens and as an adjunct test with other rapid methods of yeast identification.

Candida albicans↗
PubMed1977

Scleroma (rhinoscleroma) in a Nigerian maxillo-facial practice. Review and case reports.

Scleroma (rhinoscleroma), a chronic granulomatous disease of the upper respiratory tract, is endemic within a confined distribution of geographic foci. Sporadic cases and those arising in poorly defined foci may be unexpected and difficult to diagnose. Three cases from a maxillo-facial unit in northern Nigeria are described, of which two simulated intranasal neoplasms and the third had atypical clinical features. These cases form the first substantial description of scleroma in Nigeria, a country that is part of an indefinite focus of the disease. The epidemiology, clinical features, pathology and diagnosis of scleroma are reviewed.

Adult↗
PubMed1977

Evaluation of a caffeic acid-ferric citrate test for rapid identification of Cryptococcus neoformans.

An evaluation of a rapid caffeic acid-ferric citrate paper disk test for the identification of Cryptococcus neoformans, using 474 isolates of yeasts and yeastlike organisms, showed that 96.6, 97.7, and 98.3% of 176 isolates of C. neoformans produced brown to dark-brown pigment on disks incubated for 6 h at room temperature, 30 degrees C, and 37 degrees C, respectively. All C. neoformans produced brown to dark-brown pigment within 24 h. However, nonspecific pigmentation was encountered at all temperatures of incubation with one isolate of Trichosporon cutaneum and, at room temperature only, with one isolate of C. luteolus after 6 h. Other genera of yeasts produced similar pigmentation after 24 h at all temperatures. The age of the cultures tested or the types of media used before testing did not significantly affect the ability of C. neoformans to produce pigmentation at 37 degrees C. A positive test may prove useful for presumptive identification of C. neoformans, but a negative reaction should not be used to rule out an identification of this yeast. Since a number of false-negative and false-positive tests occur, it is necessary to confirm, by other biochemical tests, the identification of all organisms suspected of being C. neoformans, to reduct the serious risk of missing or misidentifying this important pathogen.

Caffeic Acids↗
PubMed1977

Prevalence of fungal complement-fixing antibodies in sarcoidosis.

The prevalence of fungal complement-fixing antibodies in sera from 58 patients with sarcoidosis was determined and compared to complement-fixing antibody titers in 50 sera from a normal control group and 50 antinuclear antibody-positive sera. Sera from 9 patients with sarcoidosis had complement-fixing antibody titers greater than 1:8 to Histoplasma yeast antigen; serum from one normal control subject had a titer greater than 1:8; and none of the antinuclear antibody-positive sera demonstrated titers greater than 1:8. There were no significant complement-fixing antibody concentrations observed against histoplasmin, blastomycin, and coccidioidin antigens in any serum from the 3 groups studied. The increase in antibody titers to the Histoplasma yeast antigen might have been related to the generalized increase in immunoglobulin concentrations noted in patients with sarcoidosis.

Antibodies, Fungal↗
PubMed1977

Cryptococcosis, with emphasis on the significance of isolation of Cryptococcus neoformans from the respiratory tract.

Cryptococcus neoformans was isolated from 65 patients: 11 had meningitis, 11 had disseminated cryptococcosis without meningitis, and 43 had C neoformans isolated from the respiratory tract. Predisposing conditions and the diagnostic value of cultures from various sites and of the latex agglutination test on cerebrospinal fluid and serum are analyzed for patients with extrapulmonary disease. Nine patients had pleural effusions; the effusion was cultured in six and yielded C neoformans in four. None of 11 deaths among 43 patients with respiratory tract isolates could be attributed to cryptococosis. The 32 survivors were nor treated with antifungal agents. Twenty-six of 43 patients with respiratory isolates had various bronchopulmonary disorders, with chronic obstructive pulmonary diseases and asthma the most common (28 percent). Seven of 28 patients (25 percent) with roentgenographically detected lung lesions had carcinoma of the lung. Roentgenographic evidence of a lung lesion and C neoformans grown from the respiratory tract warrant a further search for carcinoma of the lung.

Adult↗
PubMed1977

Should yeasts in respiratory secretions be identified?

Four hundred forty samples of sputa and bronchial washings were examined microscopically for evidence of pulmonary and oropharyngeal secretions. Most (88%) sputa showed definite evidence of oropharyngeal contamination, whereas bronchial washings showed much less frequent (21%) contamination. Culture results of the same specimens showed that yeasts (excluding dimorphic fungi) were recovered from 74% of the sputa and 25% of the bronchial washings. It seems that microscopic evidence of oropharyngeal contamination is a reliable index for predicting the presence of yeasts in respiratory secretions. Their presence in cultures of respiratory secretions probably represents "normal flora" except for Cryptococcus neoformans, and their routine identification is not warranted.

Evaluation Studies as Topic↗
PubMed1976

Studies on Alternaria allergens. I. Establishment of the radioallergosorbent test for measurement of Alternaria allergens.

The ability to covalently couple Alternaria allergens to microcrystalline cellulose particles has permitted not only the measurement of IgE antibodies to Alternaria in patient serums but also the identification of allergenic fractions from crude Alternaria extracts. Crude aqueous Alternaria extracts from 3 commerical suppliers were coupled to cellulose but failed to bind more than 5% of total radioactive counts (TRC) when reacted with serums from highly sensitive patients. Fractionation of a commercial extract through Sephadex G-25 showed that almost all allergenic activity was located in a protein- and carbohydrate-containing peak eluting at the column void volume. These fractions were pooled and coupled to cellulose to yield a RAST polymer which produced up to 20% TRC binding when tested with serums from over 100 Alternaria-sensitive patients, and only up to 1% TRC binding with 17 nonallergic serums. The study of commercial Alternaria extracts by chromatographic and Rast inhibition techniques showed that present extracts are neither qualitatively or quantitatively comparable.

Allergens↗
PubMed1976

Laboratory diagnosis of fungal infections.

Most hospitals do not perform mycologic examinations because laboratory personnel still believe in the "old wives' tale" that mycology is too difficult to do and that the fungi are too infectious to handle. This discussion presents methods suitable for use in laboratories of all sizes. It is hoped that laboratories will take the initiative in offering diagnostic mycology services routinely. Medical mycology can be both a challenge and a rewarding experience to those who choose to become involved.

Culture Media↗