Citation:

Genthner, F., J. Upadhyay, R. CAmpbell, AND B. Genthner. ANOMIALIES IN TH ENUMERIATION OF STARVED BACTERIA ON CULTURE MEDIA CONTAINING NALIDIXIC ACID AND TETRACYCLINE. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-90/515 (NTIS PB91206870).

Description:

Culturable counts of antibiotic resistant, genetically engineered fluorescens were determined on antibiotic-containing plate count agar during starvation in water. he mean of the colony counts on plate count agar with or without tetracycline (4.9 x 106 ml) was significantly higher than mean colony counts on plate count agar containing either nalidixic acid or nalidixic acid plus tetraclycline (2.5 x 10 6 ml-1). fter 20 days of starvation the highest mean colony counts continued to be obtained on plate count agar (7.2 x 10 6 ml-1) with slightly, but significantly, lower counts obtained on plate count agar containing either nalidixic acid (5.6 x 10 6 ml-1) or tetraclycline (1.5 x 10 6 ml-1). ombination of nalidixic acid and tetracycline in plate count agar, however, dramatically reduced colony counts (8.3 x 10 2 ml-1) after this starvation period. he addition of catalase to plate count agar containing nalidixic acid and tetracycline negated the effect caused by this combination. hen colony counts obtained over the entire 20 day incubation were considered, the addition of MgSO4 to plate count agar containing nalldixic acid and tetracycline resulted in a significant increase in colony counts.

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