No abstract

The level of reproducibility for replicate determinations of drug sensitivity was significantly greater for liquid than for solid cultures and decreased markedly with the density of colonies upon seeded agar plates. Inocula of Escherichia coli and Pseudomonas aeruginosa were significantly less sensitive towards chlorhexidine when derived from liquid rather than solid culture. We therefore suggest that only liquid cultures be used for the preparation of challenge inocula for regulatory tests of antimicrobial activity.

Chemically defined and semi‐defined media were designed for the preservative‐efficacy testing micro‐organisms designated by the United States Pharmacopoeia, in which the organisms went into the stationary phase of growth at an optical density (E470) of 1.0, because of depletion of a single carbon, nitrogen or phosphate source. Aspergillus niger was grown on solid media containing concentrations of these nutrients which limited the rates of mycelial development and sporulation density. The ability of the micro‐organisms to survive and grow in the presence of chlorhexidine diacetate, benzalkonium chloride and thiomersal varied markedly with the nutrient‐depletion of the inocula. No universal pattern of sensitivity emerged among microorganisms. Only A. niger showed little overall change in preservative sensitivity. These results highlight the need to define more adequately growth media and conditions for the production of inocula for antimicrobial challenge tests.

Folic acid and multivitamin tablets containing Aspergillus flavus Penicillia spp. and Cladosporia spores were prepared at a compression pressure of 148 MN/m2 and stored at 35°C under different relative  humidifies (75,85, and 95)% within air tight containers, to study the effect of storage condition on them, as well as ,the estimation of the microbial level of the raw materials intended to be used in the two kinds of tablets . Result showed that some raw materials derived from natural origin were heavily contaminated with microorganism compared to that of synthetic origin ,the results also indicated the effect of relative humidity , types of fungal spore , and the hygroscopic nature of exicpient upon survival. Multivitamin tablets showed more survival than folic acid tablets and this is due to the presence of more nutrients. No aflatoxin was obtained from both multivitamin and folic tablets at 35°C temperature; this is due to the temperature which is not an optimum temperature for aflatoxin B1 production. Key words: Storage conditions of tablet, fungal spores

No abstract