Automated System for Analytical Microbiology II: Construction of System and Evaluation of Antibiotics and Vitamins

Tobramycin belongs to the aminoglycoside class of antibiotics. Assay procedures were investigated to determine the most suitable methods for the assay of tobramycin in blood, urine, and pharmaceutical preparations. The agar-plate assay was the method of choice for determinations in urine and serum. The turbidimetric assay was selected for the assay of pharmaceutical preparations. An extraction technique is described that minimizes problems encountered in the estimation of tobramycin in urine. Sample diluents, pH, and molarity were important and were variable depending on assay methods. Evidence is presented to show binding of tobramycin to a-cellulose susceptibility discs. Iron and sodium ions demonstrated potential inhibition of tobramycin in all assay methods tested.

“…5 produced a substantial decrease in assay sensitivity as the iron concentration was increased (Fig. 7).…”

Section: Resultsmentioning

confidence: 96%

Section: Methodsmentioning

confidence: 99%

Factors Influencing the Microbiological Assay of Tobramycin

Lamb

Mann

Simmons

1972

“…The Autoturb is an automated system for photometric microbiological analyses. An extensive description of the Autoturb has been given by Kuzel and Kavanagh (7).…”

Section: Methodsmentioning

confidence: 99%

Turbidimetric Bioassay for Carbenicillin

Stankewich

Upton

1973

A quantitative turbidimetric bioassay has been developed for carbenicillin with the use of a strain of Escherichia coli. The assay is relatively specific for carbenicillin and is not affected by 10% (wt/wt) benzylpenicillin. It has been demonstrated to be more precise than the plate diffusion assay. Since it is readily automated, it is also faster and less expensive. The influence of pH, time, and extent of growth on the assay has been evaluated.

“…Excellent precision can be achieved with a manual turbidimetric microbiological assay provided special care is taken in all of the operational details of the assay (1). A system for carrying out semiautomated photometric assay, the Autoturb System, has been reported to give a high order of precision for the assay of vitamins and antibiotics including cephalexin (2). This system has also been used for carbenicillin assay, resulting in increased speed and precision over the plates diffusion assay (7).…”

mentioning

confidence: 99%

“…The Autoturb, a semiautomated system for doing photometric assays described by Kuzel and Kavanagh, was used in these studies (2). In use, a carousel holding 40 tubes provides media blanks, samples of known concentration, standards, and unknown samples for each of two self-contained independent assays.…”

mentioning

confidence: 99%

Semiautomated Turbidimetric Microbiological Assay for Determination of Cefazolin

Pitkin¹,

Actor²,

Holl³

et al. 1974

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. Accuracy of the turbidimetric assay was evaluated by comparing data obtained from a chemical (hydroxylamine) and a biological (disk diffusion) assay. The available data show the turbidimetric assay to be a rapid, accurate, and reproducible method for determining the biological activity of cefazolin samples.