Characterization of β-lactam antagonist in supplement C

Woolfrey, Bert F.; Gresser-Burns, Mary E.; Ehresman, David J.; Lally, R T

doi:10.1016/0732-8893(88)90093-4

Cited by 1 publication

(3 citation statements)

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“…For strain 1034 (Fig. 1B) 34,1990 i00.0005 B on May 10, 2018 by guest http://aac.asm.org/ Downloaded from 0.2, and 0.2%, respectively, indicating that the strain was somewhat more rapidly and progressively killed than strain 1034 was. The paradoxical effect was distinct for all the curves, with peaks increasing proportionately over the time of ampicillin action.…”

Section: Methodsmentioning

confidence: 99%

“…We previously developed the ADPC method (34,36,38) to provide an alternative to broth dilution methodology for assessing bactericidal action. The uniqueness of the ADPC method is that the inoculum CFU is immobilized in an agar gel matrix during the action of and after the inactivation of the antimicrobial agent, thus potentially avoiding variations in minor technical factors that are known to influence markedly the results of broth dilution methods.…”

Section: Discussionmentioning

confidence: 99%

“…influenzae strains. Of the 20 ampicillin-susceptible nontypeable H. influenzae isolates studied, 15 were obtained through the courtesy of Timothy F. Murphy (17) (34,35) we encountered some loss of ampicillin activity in ADPC plates made with MHA and 1% supplement C (Difco Laboratories, Detroit, Mich.) as a consequence of various lots of supplement C containing small amounts of P-lactamase. To avoid this problem in the present study, ADPC panels were prepared with the recently introduced HTM (12).…”

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Ampicillin killing curve patterns for ampicillin-susceptible nontypeable Haemophilus influenzae strains by the agar dilution plate count method

Woolfrey

Enright

1990

Antimicrob Agents Chemother

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Ampicillin killing curve patterns for 20 strains of ampicillin-susceptible nontypeable Haemophilus influenzae were determined by the agar dilution plate count method. The paradoxical effect was detected in the 24-h killing curve patterns for each strain. For the biphasic effect, minimum survivor percentages (maximum killing) occurred over a narrow range of ampicillin concentrations immediately above the MIC, with survivor percentages then rising rapidly to peak at --loglo-unit increment higher. The 24-h minimum survivor percentages for the 20 strains ranged from -0.01% (rapid killing) to >10% (slow killing). In comparison with the previous results for typeable strains, the present findings suggest that nontypeable stains are, on average, killed much more slowly. Based on the initial 24-h killing curve patterns for the 20 strains, 4 strains were selected as putative representatives of the range of bactericidal responses encountered. These strains were then studied to examine the reproducibility of the 24-h patterns and to determine sequential killing curves. These patterns were found to be reproducible and served to characterize the relative killing responses of the strains. In the sequential studies of three of the four strains, tiny colonies having the gross and microscopic characteristics of L-forms were found to be present on the agar dilution plate count plates prior to the application of penicillinase at 48 and 72 h. Such colonies reverted to vegetative forms within 24 to 48 h after application of penicillinase to the panels. Of particular interest was the observation that the paradoxical effect was manifested both by the L-form colonies and by the reverted vegetative colonies. The late development of L-forms was observed for both rapidly and slowly killed strains.In a previous study (35) we described ampicillin killing curve patterns for type b Haemophilus influenzae strains as determined by the agar dilution plate count (ADPC) method. Killing curve patterns were found to be strain dependent and ranged from strains that were killed slowly to others that were killed rapidly. The paradoxical effect (7) was demonstrated at some time during the killing sequence for each strain studied. We present here a similar study of ampicillin killing curve patterns for ampicillin-susceptible nontypeable H. influenzae strains. MATERIALS AND METHODSStudy design. Twenty ampicillin-susceptible nontypeable H. influenzae strains were studied. On retrieval from stock culture, each strain was confirmed to by nontypeable H. influenzae and ampicillin susceptible by standard microbiological methods. Several 24-h killing curve patterns were then determined by the ADPC method for each strain (35). On the basis of the 24-h patterns, several putative rapidly to slowly killed strains were studied further to determine the reproducibility of the 24-h patterns and to determine patterns of sequential killing after various times of ampicillin action.H. influenzae strains. Of the 20 ampicillin-susceptible nontypeable H. influenzae isolates stu...

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Section: Methodsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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