| 1. |
- Hanberger, Håkan, et al.
(författare)
-
Pharmacodynamics of daptomycin and vancomycin on Enterococcus faecalis and Staphylococcus aureus demonstrated by studies of initial killing and postantibiotic effect and influence of Ca2+ and albumin on these drugs.
- 1991
-
Ingår i: Antimicrobial Agents and Chemotherapy. - : American Society for Microbiology. - 0066-4804 .- 1098-6596. ; 35:9, s. 1710-1716
-
Tidskriftsartikel (refereegranskat)abstract
- The pharmacodynamics of daptomycin and vancomycin on Enterococcus faecalis ATCC 29212 and Staphylococcus aureus ATCC 25923 were investigated by studying the postantibiotic effect (PAE) and initial killing. The influence of Ca2+ and albumin on these drugs was also evaluated. The PAE was studied by use of bioluminescence assay of bacterial ATP. Daptomycin at clinically achievable concentrations produced a dose-dependent PAE on E. faecalis (0.6 to 6.7 h) and S. aureus (1.0 to 6.3 h). The long PAE of daptomycin was seen simultaneously with a potent dose-dependent initial killing assayed by viable count determination. The initial change in bacterial ATP was not as extensive as the decrease in viability. Vancomycin at corresponding concentrations produced shorter PAEs on E. faecalis (0.5 to 1.0 h) and S. aureus (1.3 to 1.8 h). This coincides with a weak non-dose-dependent initial change in viability and intracellular ATP. The MICs of vancomycin were not influenced by different Ca2+ concentrations or by the addition of albumin to the broth. The MICs of daptomycin for both strains were lowered, and the PAEs were prolonged with increasing concentrations of Ca2+ in the broth. The PAE of daptomycin was Ca2+ dependent to the same extent as the MIC was. In the presence of physiological concentrations of albumin and free Ca2+, the PAEs of daptomycin on both strains were reduced and the MICs were increased in comparison with the results obtained in pure Mueller-Hinton broth with approximately the same free Ca2+ concentration. This decrease in daptomycin activity was considered to be due to the albumin binding of daptomycin. Despite the albumin binding of daptomycin, the PAE produced on E. faecalis and S. aureus in the presence of a physiological free Ca2+ concentration was still over 6 h at clinically achievable concentrations.
|
|
| 2. |
- Isaksson, Barbro, et al.
(författare)
-
Synergic post-antibiotic effect of amikacin in combination with beta-lactam antibiotics on gram-negative bacteria.
- 1991
-
Ingår i: Journal of Antimicrobial Chemotherapy. - : Oxford University Press. - 0305-7453 .- 1460-2091. ; 28:1, s. 25-34
-
Tidskriftsartikel (refereegranskat)abstract
- The post-antibiotic effect (PAE) of amikacin alone and in combination with ceftazidime, ceftriaxone and piperacillin was studied for two strains each of Pseudomonas aeruginosa and Serratia marcescens using a bioluminescent assay of bacterial ATP. Two models were used for combining beta-lactam antibiotics and amikacin: in one model the cultures were incubated with 32 mg/L of ceftazidime, 128 mg/L of ceftriaxone or 32 mg/L of piperacillin for 1 h. Different concentrations of amikacin (0.5-64 mg/L) were then added. Incubation of the combinations continued for one more hour. The antibiotics were eliminated by dilution. In the second model tested, one strain of S. marcescens was simultaneously exposed to amikacin and a beta-lactam antibiotic for 2 h. The PAEs produced by the drugs in combination were longer than the sum of the individual effects of the drugs when they were used alone. Results were equally good with both models. A synergic PAE was also found with amikacin concentrations close to the MIC in combination with low concentrations of ceftazidime, ceftriaxone and piperacillin.
|
|
| 3. |
- Isaksson, Barbro, et al.
(författare)
-
Synergistic post-antibiotic effect of amikacin and beta-lactam antibiotics on Enterococcus faecalis.
- 1991
-
Ingår i: Journal of Antimicrobial Chemotherapy. - : Oxford University Press. - 0305-7453 .- 1460-2091. ; 27, s. 9-14
-
Tidskriftsartikel (refereegranskat)abstract
- The in-vitro post-antibiotic effect (PAE) of amikacin alone and in combination with ceftazidime, ceftriaxone and piperacillin was studied for two strains of Enterococcus faecalis using a bioluminescent assay of bacterial ATP. The two strains of E. faecalis were resistant to amikacin, ceftazidime and ceftriaxone but sensitive to piperacillin. The bacterial cultures were incubated with the beta-lactam antibiotics for 1 h and concentrations of amikacin between 2-64 mg/l were then added. Thereafter, incubation continued with the combinations for one more hour. After dilution, regrowth was monitored by measuring bacterial ATP every hour. Increasing concentrations of amikacin (2-64 mg/l), ceftazidime (8-32 mg/l) and ceftriaxone (32-128 mg/l) resulted in little or no PAE (0-0.3 h) on these strains. PAEs of 0.5 to 1.6 h resulted from exposure to piperacillin (4-32 mg/l). In combination amikacin and piperacillin increased the PAE to 5.5 h. A synergistic PAE was also seen when the enterococci were exposed to amikacin combined with ceftazidime or ceftriaxone in concentrations close to the MICs of the latter antibiotics.
|
|
