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G D Fay

Publications and source records attributed to G D Fay.

9 recordsLinked to original sources
PubMed1974

Methods for detecting indole production by gram-negative nonsporeforming anaerobes.

To help select the most appropriate method for detecting indole production with anaerobic gram-negative bacilli, several recommended methods were compared. Indole was measured both quantitatively and qualitatively after varying periods of incubation. Studies evaluated the results obtained in different media, the effect of adding glucose and/or tryptophan, the requirement for strict anaerobiasis, and the effects of reducing the total volume of broth. A 1-ml amount of thioglycolate broth without glucose but with 0.02% tryptophan gave optimal results after 2 to 7 days of incubation in anaerobic (Gas-Pak) jars. The majority of clinical isolates will give strong positive tests after 1 to 2 days but a few require 3 to 7 days of incubation. Prolonged incubation was required more frequently with conventional methods.

Aerobiosis↗
PubMed1972

Quality control of antimicrobial disc susceptibility testing with a rapid method compared to the standard methods.

A rapid method for assay of antimicrobial agents in human serum was modified to provide a method for rapidly assessing the activity of antimicrobial discs being used for susceptibility testing. Each morning, discs are taken from the clinical laboratory's working supply and are applied directly onto test plates which have been inoculated, preincubated, and stored in a refrigerator. Inhibitory zones can be measured within 5 to 6 hr, i.e., before that day's batch of tests is to be set up. If the zone of inhibition for any agent is more than 2 standard deviations below the mean, the discs are discarded and another cartridge is selected from the stock supply for that day's susceptibility tests. In this way, discs of questionable potency are discarded before they are used for testing, rather than waiting until the next day as is usually done with the standard methods. The rapid control test yields zones which are slightly smaller and somewhat more variable than with the standard Kirby-Bauer or agar overlay methods, but the slight decrease in precision is outweighed by the advantages of rapidity and simplicity.

Methods↗
PubMed1972

Rapid ornithine decarboxylase test for the identification of enterobacteriaceae.

Conventional methods for detecting ornithine decarboxylase activity require an extended period of incubation. However, with a few simple modifications, accurate results were obtained within a few hours rather than several days. The broth medium was modified, primarily by omitting glucose and by decreasing the pH to 5.5. A 1-ml amount of this broth was inoculated with one colony and then overlaid with sterile mineral oil. Within 2 to 4 hr, the pH increased if ornithine was decarboxylated, thus changing the color of the internal pH indicator to a dark purple. If the amino acid was not decarboxylated, the pH decreased to pH 5.0 to 5.2, enough to give a definite yellow color. With 347 selected clinical isolates, the rapid test gave results identical to those obtained in 1 to 4 days with Moeller's decarboxylase medium. Less reliable results were obtained with Difco's decarboxylase medium with 0.3% agar which was stabinoculated and read after 18 to 24 hr without a mineral oil seal. The rapid ornithine decarboxylase test represents a simple, accurate technique which is well suited for the clinical microbiology laboratory.

Bacteriological Techniques↗
PubMed1972

Efficiency of a transport medium for the recovery of aerobic and anaerobic bacteria from applicator swabs.

The survival of four aerobic and four anaerobic pathogens was evaluated quantitatively on cotton swabs and calcium alginate swabs stored in dry tubes as compared with swabs stored in Amies Transport Medium without charcoal. Survival of the pathogens was markedly improved when stored in Amies Transport Medium, although there was considerable loss of viability after a few hours of storage.

Aerobiosis↗