A Three-Hour “Physical Development” Cup‐Plate Assay for Penicillin*

Goyan, Frank M.; Dufrénoy, Jean; Strait, L. A.; Pratt, Robertson; Juntunen, Toinie

doi:10.1002/jps.3030360302

Cited by 14 publications

(15 citation statements)

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“…Experimental results show that the threshold for activity of alkaline phosphatase and for dehydrogenase obtains at about 0.01 unit per ml, which corresponds to the concentration of penicillin previously estimated to occur at the margins of inhibition zones on assay plates (Pratt and Dufrenoy, 1948a). The principle that is involved in the rapid assays on plates (Goyan, Dufrenoy, Strait, and Pratt, 1947;Pratt and Dufrenoy, 1947c;Pratt, Goyan, Dufrenoy, and Strait, 1948) applies equally well to assays by the serial dilution method. Either the triphenyltetrazolium chloride reagent for dehydrogenases or the TPP reagent for alkaline phosphatase can be used to define the threshold between bacteriostatic and subbacteriostatic concentrations of penicillin after a much shorter period of time than is required for estimation of the end point by means of turbidimetry.…”

Section: Experiments and Resultsmentioning

confidence: 99%

Cytochemical Mechanisms of Penicillin Action

Dufrénoy

Pratt

1948

J Bacteriol

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Section: Experiments and Resultsmentioning

confidence: 99%

Cytochemical Mechanisms of Penicillin Action

Dufrénoy

Pratt

1948

J Bacteriol

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“…Some were incubated according to the standard 16-hour method. Others were seeded, preincubated for 3 hours, cylindered, and then subjected to a second incubation period of 3 hours with penicillin, according to the modified cylinder plate method involving physical development (Goyan, Dufrenoy, Strait, and Pratt, 1947). The test organism used was Staphylococcus aureus NRRL strain 313 (same as FDA strain 209P).…”

Section: Methodsmentioning

confidence: 99%

Cytochemical Mechanisms of Penicillin Action

Pratt

Dufrénoy

1947

J Bacteriol

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In a previous paper we described the gross appearance of penicillin assay plates after chemical treatments which reveal sharp boundaries around the zones of inhibition (Dufrenoy and Pratt, 1947). Most of the tests that were described are effective following exposure of the test organisms to penicillin for periods as short as 2 to 3 hours, i.e., before zones of inhibition are discernible on untreated plates. Several of the tests may find application as rapid cylinder plate assay methods (Pratt and Dufrenoy, 1947). The sharp delineation of the inhibition zones was interpreted as an expression of a threshold effect; positive reactions for-SH groups and for OH=C-C==OH groups were obtained outside the zones of inhibition, but not inside. The evidence suggested an increase.of rH within the zones and that this increase was correlated with inhibition of dehydrogenase systems. Since there is strong evidence in the literature that dehy-I The execution of the work reported in this paper was made possible by a generous research grant from the

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“…It has been shown by application of appropriate reagents to standard agar penicillin assay plates after different periods of diffusion of penicillin that-SH groups and dienols are present outside the zones of inhibition, but are relatively scarce or are lacking inside the zones (Dufrenoy and Pratt, 1947). The results indicated)hat a threshold effect involving an--SH;=S-S equilibrium exists at the boundaries of the inhibition zones.…”

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confidence: 99%