Postantibiotic effects and postantibiotic sub-MIC effects of erythromycin,roxithromycin, tilmicosin, and tylosin on Pasteurella multocida

When intermittent dosing is used during treatment, the concentrations of an tibiotics fluctuate and subinhibitory concentrations may occur between dose s. Postantibiotic effects (PAEs) and postantibiotic subinhibitory effects ( PA SMEs) on bacteria may provide additional, valuable information for the r ational use of a drug in clinical practice. In this study tilmicosin was th e most active antibiotic tested against P. multocida type D with MICs rangi ng from 4-16 mg/l. Roxithromycin and tilmicosin induced a statistically sig nificantly longer PAE than did tylosin against P. multocida types A and D ( P < 0.05). The duration of PAEs and PA SMEs were proportional to the concen trations of drugs used for exposure. The PA SMEs were substantially longer than PAEs on P. multocida. Tilmicosin had a longer PA SME compared with ery thromycin, roxithromycin and tylosin for P. multocida, The computerized inc ubator used in the present study provided an efficient and convenient deter mination of PAE and PA SME, allowing frequent measurements of the bacterial growth. (C) 2001 Elsevier Science B.V. and International Society of Chemot herapy, All rights reserved.