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A method is described for the microbiological assay of folic acid activity in serum with Lactobacillus casei as test organism and a modified medium in which the organism gives a greater growth response than in media previously detailed. The results of experiments carried out to validate the use of this medium are shown. In 94 control subjects levels of folic acid activity in the serum ranged fr...

Treatment of a pharmaceutical preparation of vitamin B(12) and tetracycline with an ion-exchange resin by the batch method differentially adsorbed tetracycline, making possible a statistically reproducible microbiological assay of vitamin B(12) by the standard Escherichia coli plate method.

The universal acceptance of the animal growth-promoting properties of some antibiotics and their wide usage in formulated commercial feeds requires that simple, rapid and reliable analytical methods be available for control purposes. Of the several antibiotics used in poultry rations, penicillin exerts its growth-promoting properties at levels considerably lower than other antibiotics (2 grams ...

A fully automated method for the measurement of serum pyridoxal has been developed. Acid phosphatase was used for dephosphorylation and precipitation of the serum proteins was not required. A chloramphenicol-resistant strain of L. casei was used as the test organism and this removed the need for sterilization. The method gives highly reproducible results, and is suitable for population and inst...

The present work reports a simple, fast and sensitive microbiological assay applying the turbidimetric method for the determination of ciprofloxacin hydrochloride (CIPRO HCl) in ophthalmic solutions. The validation method yielded good results and included excellent linearity, precision, accuracy and specificity. The bioassay is based on the inhibitory effect of CIPRO HCl upon the strain of Stap...