Postantibiotic effect in Escherichia coli determined with real-time metabolic monitoring - PubMed (original) (raw)

Postantibiotic effect in Escherichia coli determined with real-time metabolic monitoring

J M Libby. Antimicrob Agents Chemother. 1998 Jan.

Abstract

Metabolic activity was used to quantify the delay in recovery of Escherichia coli after limited exposures to cefotaxime and piperacillin. This was measured with a microphysiometer, a device which measures changes in pH in the cellular environment, which in turn reflects the metabolic activity of the cells. The antibiotics were rapidly pumped into and flushed from each cellular environment. The length of time that the bacteria were exposed to either antibiotic was determined by programmed valve changes. Metabolic activity was measured during periods in which the instrument's pumps were off. Graphical analysis of the data was used to determine the postantibiotic effect. The lengths of the postantibiotic effects of both drugs (95 to 101 min) determined with the microphysiometer corresponded with the reappearance of short, highly motile cells in significant numbers.

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Figures

FIG. 1

FIG. 1

Metabolic profile resulting from growth of E. coli in the microphysiometer (A) and delay of metabolic profiles following exposures to cefotaxime (B).

FIG. 2

FIG. 2

Short, motile rod forms became more numerous, as illustrated in these photographic progressions, taken 60, 75, 90, and 105 min after removal of piperacillin (a to d, respectively) and cefotaxime (e to h, respectively). Negative control cultures had a similar appearance at all time intervals examined and consisted almost entirely of short, motile rods (i). Magnifications, ×400.

FIG. 2

FIG. 2

Short, motile rod forms became more numerous, as illustrated in these photographic progressions, taken 60, 75, 90, and 105 min after removal of piperacillin (a to d, respectively) and cefotaxime (e to h, respectively). Negative control cultures had a similar appearance at all time intervals examined and consisted almost entirely of short, motile rods (i). Magnifications, ×400.

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