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Biomedical subjects

S N McDermott

Publications and source records attributed to S N McDermott.

13 recordsLinked to original sources
PubMed1990

Use of urea filter paper disc to detect urease activity in Enterobacteriaceae by multipoint replication techniques.

A new method of detecting urease activity in Enterobacteriaceae was developed. An 8.5 cm filter paper disc impregnated with 20% urea and 0.5% bromocresol purple was placed on the surface of a glucose fermentation plate after inoculation with a multipoint replicator and overnight incubation. This method was compared with the commercially prepared Mast urea agar (Multipoint) and Fuscoe's Urea Plate Medium. A total of 240 routine isolates of Enterobacteriaceae were tested for urease activity using the three methods. Sixty five isolates were positive by the three methods while 33 isolates gave differing results. The urea disc method was more sensitive for detecting urease activity in isolates of Klebsiella species, Morganella morganii, and Yersinia enterocolitica. It also overcame the problem associated with the other two media of diffusion of alkali end products through the medium.

Bacteriological Techniques↗
PubMed1989

New datum handling methods for the quality control of antibiotic solutions and plates used in the antimicrobial susceptibility test.

Quality control programs are described for monitoring both the antibiotic solutions and the plates used in the dilution antimicrobial susceptibility test. For the quality control of antibiotic solutions, a simple comparative disk diffusion assay is used in which the data are expressed as zone ratios calculated from the following formula: zone ratios = mean zones of inhibition for disks impregnated with antibiotic under test/mean zones of inhibition of previously prepared quality control disks impregnated with the same antibiotic. The rejection limits set for this method are twice as stringent as for MIC estimation, and its precision is four times greater. For quality control of the antibiotic agar plates, fluid was absorbed directly into filter paper disks placed on the surface of the medium. These disks were then transferred to a seeded plate to produce zones of inhibition. These zones of inhibition were then converted to zone ratios by dividing the zone of inhibition for the individual antibiotics by the mean of the total zones of inhibition for all the antibiotics tested on the same plate. We further normalized these data by expressing each entry as a standard normal deviate calculated from the mean and standard deviation of the cumulative data for each individual antibiotic. The use of zone ratios reduced batch-to-batch variation, and standard normal deviate values gave a uniform result for convenience. The method has a sensitivity equal to that of an MIC estimation if it were possible to estimate the MICs of antibiotics at these low levels.

Anti-Bacterial Agents↗
PubMed1984

The use of membrane filters applied directly to the surface of agar plates for the isolation of Campylobacter jejuni from feces.

Cellulose triacetate membrane filters applied directly to the surface of non-selective blood agar plates were found to be as effective as the use of antibiotic media in isolating Campylobacter jejuni from patients with diarrhea. This method was used in parallel with selective media in the examination of 1000 specimens of feces. Campylobacters were isolated from 56 specimens using all methods. The membrane filter method detected 50 (89%), 45 of which were C. jejuni, and selective media 45 strains of C. jejuni (80%). Membrane filters used in this way can result in the detection of most cases of campylobacter enteric infection and can be used by small laboratories with limited access to selective media. They may also facilitate the isolation of antibiotic sensitive campylobacters.

Agar↗
PubMed1979

Enterocolitis due to Yersinia enterocolitica in South Australia.

From August 1976 to July 1977, all faecal specimens (3298) sent to the Enteric Department of the Institute of Medical and Veterinary Science, Adelaide were selectively cultured for Yersinia enterocolitica. Yersinia enterocolitica was isolated from three patients with diarrhoea, one of whom acquired her infection overseas. These organisms were not isolated from faecal or lymph node material collected from a limited number of sheep and pigs found to have enteritis at the time of slaughter. Enteric infection due to Yersinia enterocolitica does not appear to be common in Australia and selective culture methods using cold enrichment techniques do not appear to be justified especially in laboratories handling specimens derived mainly from adults.

Adult↗
PubMed1973

Aerobic bacteria occurring in the hind-gut of the cockroach, Blatta orientalis.

Methods are described for the isolation and identification of aerobic bacteria occurring naturally in the hind-gut of the cockroach Blatta orientalis captured from a number of wild sources, to establish whether or not human pathogens occurred naturally within the gut. During the investigation an organism was frequently found which could not be classified in any described species, and for which we propose the name Escherichia blattae.

Aerobiosis↗
PubMed1973

Laboratory transmission of enterobacteriaceae by the oriental cockroach, Blatta orientalis.

Methods of maintaining and feeding and of infecting cockroaches with pathogenic organisms were investigated.Cockroaches fed on known concentrations of Escherichia coli O119, Esch. coli O1, Alkalescens Dispar O group 2 and Shigella dysenteriae 1 (Shiga's Bacillus) were maintained in Petri dishes. The effect of various diets on the survival of these organisms within the hind-gut and faeces was observed. With a ;normal' diet of gruel Esch. coli O119 was isolated for up to 20 days, Esch. coli O1 for 17 days and ADO 2 for 15 days. Sh. dysenteriae 1 was isolated only sporadically to the third day.

Animals↗