Postantibiotic Effect (PAE)
Baytril induces a postantibiotic effect (PAE), a period of persistent growth suppression of bacteria in vitro after an antiinfective has been removed from the culture medium (7).
During this period, bacterial metabolism still is decreased and bacteria are more susceptible to phagocytosis (9). For Staphylococcus aureus it has also been proposed that energy-dependent efflux mechanisms for fluoroquinolones are depressed (10).
The duration of the PAE depends on the concentration of enrofloxacin in the culture medium, cell density in the culture, and the time of exposure to the drug (maximum of 2 hours for Staph. aureus). In general, the PAE for enrofloxacin is around 3 hours for the most relevant pathogens at drug concentrations of 8 x MIC (7).
Experiments in a mouse model suggest that PAEs under in vivo conditions are almost twice as long compared to in vitro results. It can be concluded that in vitro PAEs may underestimate the real conditions (7).
References
| (7) |
Wetzstein HG, DeJong A: In vitro bactericidal activity and post antibiotic effect of fluoroquinolones used in veterinary medicine. Suppl Compend Contin Educ Pract Vet 18 (2): 22-29, 1996. |
| (9) |
Novelli A, Mazzei T, Fallani S, et al: Postantibiotic leucocyte enhancement of fleroxacin compared to ciprofloxacin on S. aureus and S. epidermidis strains. Pharmacol Res 26 (suppl 1): 305, 1992. |
| (10) |
Piddock LVJ: New quinolones and Gram-positive bacteria. Antimicrobial Agents and Chemotherapy 38: 163-169, 1994. | |
