In vitro response to bactericidal activity of cell wall-active antibiotics does not support the general opinion that enterococci are naturally tolerant to these antibiotics
| Autor: | A. Grossato, Roberta Fontana, Marco Ligozzi, E. A. Tonin |
|---|---|
| Přispěvatelé: | Fontana, R, Grossato, A, Ligozzi, M, Tonin, ENRICO ANGELO |
| Jazyk: | angličtina |
| Rok vydání: | 1990 |
| Předmět: |
medicine.drug_class
Antibiotics Microbial Sensitivity Tests Penicillins Enterococcus faecalis Microbiology Minimum inhibitory concentration Daptomycin Cell Wall Vancomycin medicine Pharmacology (medical) Piperacillin Pharmacology Minimum bactericidal concentration Bacteria biology Drug Resistance Microbial biology.organism_classification Anti-Bacterial Agents Penicillin Infectious Diseases Ampicillin Peptides Research Article medicine.drug |
| Popis: | The incidence of tolerance and paradoxical response to bactericidal activity of penicillin was investigated in 50 clinical isolates of Enterococcus faecalis. Of the isolates tested, 86% exhibited the paradoxical phenomenon whereby there were more survivors at high than at low concentrations above the MIC. Low penicillin concentrations caused decreases equal to or higher than 99.9% in 11 strains, from 99.9 to 99.5% in 23 strains, and lower than 99.5% in 9 strains. Of the total strains, 14% were killed to the same extent by all concentrations above the MIC. The bactericidal activities of other beta-lactams (ampicillin and piperacillin) and other cell wall inhibitors (vancomycin and daptomycin) were also tested against some of these strains. In general, beta-lactams exhibited the best bactericidal activity at 2 x MIC. Piperacillin was the most active, as at 2 x MIC it reduced the original inoculum by 99.9% or more in most of the strains. No concentration of vancomycin above the MIC caused 99.9% killing of the strains, whereas daptomycin was bactericidal at 8 x MIC in most cases. Paradoxical response to bactericidal activity of beta-lactams was abolished by incubation of the inoculum with 2 x MIC before exposure to higher antibiotic concentrations. These findings suggest that enterococci are not always tolerant to cell wall-active antibiotics and that accurate in vitro bactericidal tests may be useful for the choice of appropriate therapy for infections caused by these microorganisms. |
| Databáze: | OpenAIRE |
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