Comparison of fixed concentration and fixed ratio options for testing susceptibility of gram-negative bacilli to piperacillin and piperacillin/tazobactam
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Piperacillin combined with tazobactam was tested at both a fixed ratio (8:1) and fixed tazobactam concentration (4 µg/ml) against 2,685 consecutively isolated gram-negative bacilli and 56 highly piperacillin-resistant isolates. Tazobactam significantly enhanced the spectrum of piperacillin activity. Overall, at a concentration of 16 μg/ml piperacillin alone inhibited 78.8 % of theEnterobacteriaceae isolates compared to inhibition of 92.7 % and 95.5 % by the 8:1 ratio and fixed (4 µg/ml) tazobactam combinations, respectively. In MIC tests the two combination options performed comparably against both routine and highly piperacillin-resistant isolates. Synergistic inhibition was observed for comparable numbers of isolates with the two combination options, the most marked effect being seen in the more highly piperacillin-resistant isolates. Both testing options are supported by the available human pharmacokinetic data; however the 8:1 ratio of piperacillin to tazobactam may be preferable given that the clinical formulation contains the two compounds in an 8:1 ratio and this ratio is maintained in vivo.
KeywordsInternal Medicine Testing Susceptibility Marked Effect Pharmacokinetic Data Piperacillin
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- 4.Fuchs PC, Barry AL, Thornsberry C, Gavan TL, Jones RN In vitro evaluation of Augmentin by broth microdilution and disk diffusion susceptibility testing: regression analysis, tentative interpretive criteria, and quality control limits. Antimicrobial Agents and Chemotherapy 1983, 24: 31–38.Google Scholar
- 7.Jacobs MR, Aronoff SC, Johenning S, Shlaes DM, Yamabe S Comparative activities of the beta-lactamase inhibitors YTR 830, clavulanate, and sulbactam combined with ampicillin and broad spectrum penicillins against defined beta-lactamase-producing aerobic gram-negative bacilli. Antimicrobial Agents and Chemotherapy 1986, 29: 980–985.PubMedGoogle Scholar
- 8.Jones RN, Pfaller MA, Fuchs PC, Aldridge K, Allen SD, Gerlach EH Piperacillin/tazobactam (YTR 830) combination: Comparative antimicrobial activity against 5889 recent aerobic clinical isolates and 60Bacteroides fragilis group strains. Diagnostic Microbiology and Infectious Disease 1989, 12: 489–494.PubMedGoogle Scholar
- 10.Klastersky J, van der Auwerea P In vitro activity of sulbactam in combination with various beta-lactam antibiotics. Diagnostic Microbiology and Infectious Disease 1989, 12, Supplement 4: 1655–1695.Google Scholar
- 14.National Committee for Clinical Laboratory Standards Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically M7-A2. NCCLS, Villanova, PA, 1990.Google Scholar
- 15.Sanders CC, Iaconis JP, Bodey GP, Samonis G Resistance to ticarcillin-potassium clavulanate among clinical isolates of the familyEnterobacteriaceae; role of PSE-1 beta-lactamase and high level of TEM-1 and SHV-1 and problems with false susceptibility in disk diffusion tests. Antimicrobial Agents and Chemotherapy 1988, 32: 1365–1369.PubMedGoogle Scholar