Fifty antibacterial agents, mainly antibiotics, were examined by a high voltage electrophoretic technique which determined their migration distances in agar and agarose gels at both pH 6·0 and 8·0. Comparison of the different migration distances in the two gels formed the basis for identification. Bio‐autography, using Bacillus cereus var. mycoides or Micrococcus luteus, was used to visualize the antibiotics. The method was satisfactory for identifying many antibiotics in animal tissues and animal feeding stuffs, and was capable of distinguishing antibiotic activity from that of naturally occurring inhibitors often present in those materials. It has also been used to identify antibiotics in urine and pharmaceutical preparations, and a wider application in medical microbiology is indicated.
An assessment has been carried out of the relative performance of ten instruments for quantification of adenosine triphosphate (ATP) by the firefly luciferase assay. The instruments evaluated were Amersham Amerlite Analyser, Dynatech Tube Luminometer, Dynatech Multiplate Luminometer, Dynatech Camera Luminometer, Hamilton Lumicon, LKB 1250 Luminometer, LKB 1251 Luminometer, Lumac Biocounter M2010A, Turner 20 TD Luminometer and a prototype version of the CLEAR SpeedTech 2000. An 800-fold difference in sensitivity was found between the most sensitive (Lumac, Turner) and the least sensitive (Dynatech Tube) of the conventional instruments. The Dynatech Camera Luminometer which worked on a completely different principle to the other instruments was about 5000 times less sensitive than the best of the photomultiplier tube instruments. The relative sensitivity of the instruments was maintained regardless of whether solutions of ATP in water or trichloroacetic acid extracts of bacteria were analysed. An analysis of 960 ATP bioluminescence assays showed that data obtained from such measurements are normally distributed.
Inhibitory activity (detected by Bacillus cereus var. mycoides), identical with that encountered in survey samples, was induced in homogenized fresh chicken liver or pig kidney samples by incubating at 30°C. relative potency of each of three active components as detected by t.l.c./bio‐autography of extracts of freeze‐dried material was ascertained. Three strains of Streptococcus faecalis and a Lactobacillus sp. were responsible for production of the inhibitory activity, which was not produced by any of these organisms in synthetic liquid media.
(Hoeprich, 1960) and dip-slides (Mackey and Sandys, 1965) are used. Recently, the estimation of bacterial adenosine 5'-triphosphate (ATP) in urine by instrumental analysis (Alexander et al., 1976;Johnston et al., 1976) has added a new approach to the detection of significant bacteriuria, due to the speed with which results can be obtained.This paper describes a study in which the Coulter Counter was tested to determine its suitability for the rapid screening of urines for significant bacteriuria.
Material and methods
CULTURE METHODA total of 956 urine specimens, mainly from male and female inpatients, were studied. The specimens were those received in a diagnostic bacteriological service and were stored at 4'C before examination by "Present address: Laboratory of the Government Chemist,
Escherichia coli could be detected at a concentration of 105 cells/ml. Growth curves of the organism grown in filtered tryptone soya broth were made by taking viable and Coulter counts. Both curves were similar in shape and varied little during 10 h growth. Cell volume and volume distribution were seen to vary considerably however, volume reaching a stable minimum value of 0·61 μm3 after 8 h. The Coulter Counter was considered to be potentially useful for detecting significant bacteriuria.
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