Since the microbiological assay of the antibiotic content of serum generally requires 18 to 24 hr of incubation, results of such procedures may not become available in time to make appropriate adjustments in subsequent dosages of antibiotic. A 4-hr bioassay for determining concentrations of gentamicin in serum has been developed in which Staphylococcus aureus ATCC 6538P is used as the test orga...

The Autoturb System, a semiautomated system for photometric bioassay, was used to determine cefazolin content. Suitable conditions for the assay using Streptococcus faecalis ATCC 10541 as the indicator organism included a medium pH of 6.0 to 7.0 and an incubation time of 3 to 3.5 h at 36 C. Multiple independent assays of samples from a common batch showed the test to be highly reproducible. Acc...

This heterogeneous assay for tobramycin involves fluorescein-labeled tobramycin, which competes with native unlabeled tobramycin for anti-tobramycin binding sites. Bound and free labeled antigen are separated by precipitation with a second antibody. Fluorescence intensity of the resuspended precipitate is inversely proportional to native tobramycin concentration. Background interference was con...

a time similar assay methods were used to assess their concentrations in various types of materials. Such methods are time-consuming, require specialized experience, and are not particularly sensitive or accurate. Chemical methods which were developed later still lack sensitivity and are subject to inaccuracies owing to the necessity of a number of manipulations to remove interfering substances...

'rhe effects of freezinig on bacterial cultures have been investigated by numerous workers. The most commonly used method of preserving microorganisms is lvophilization (drying from the frozen state), but this is a drastic procedure for in most instances comparatively few organisms (2 to 3 per cent) survive the freeze drying process. Cultures preserved in this way have remained viable for as lo...

The calcium leucovorin assay was improved by adding THORAL germicide which resuspended the cells so that an accurate turbidity reading could be obtained.

AIMS To develop a sensitive, direct, automated method for the measurement of serum and red cell thiamin. METHODS A microbiological assay using a chloramphenicol resistant strain of Lactobacillus fermenti as the test organism was developed. Addition of chloramphenicol and cycloheximide to the assay medium suppressed bacterial and yeast contamination and enabled tests to be automated without re...

An agar diffusion method using paper disks on plates seeded with Clostridium perfringens and incubated anaerobically to assay serum levels of metronidazole is described. The lowest serum metronidazole concentration that could be measured was 0.7 mug/ml, and the average error was 4% for 5 mug/ml. This assay could measure metronidazole in the presence of gentamicin or in the presence of penicilli...

Since the eshablishment of p-aminobenzoic acid as a member of the B vitamin group, a considerable interest has been shown in methods of determination in natural materials. Since known chemical methods are not sufficiently sensitive, it became evident that microbiological tests should be the most practicable. The organism Clostridium acetobutylicum has been used (I) but no general assay procedur...

Within groups of similar proteins-for example whale-meat meals or fish meals of different manufacturethere may be large differences in nutritive quality but only relatively small differences in amino acid composition. From chemical and microbiological tests (Bunyan & Price, 1960; Ford, 1962) it appears that the differences in quality may not be specifically related to any one amino acid but ref...