Premium
A large potentiation effect of serum on the in vitro potency of tulathromycin against Mannheimia haemolytica and Pasteurella multocida
Author(s) -
Lees P.,
Illambas J.,
Potter T. J.,
Pelligand L.,
Rycroft A.,
Toutain P.L.
Publication year - 2017
Publication title -
journal of veterinary pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.527
H-Index - 60
eISSN - 1365-2885
pISSN - 0140-7783
DOI - 10.1111/jvp.12372
Subject(s) - potency , pasteurella multocida , minimum inhibitory concentration , minimum bactericidal concentration , antimicrobial , dose , pharmacodynamics , microbiology and biotechnology , in vitro , biology , in vivo , veterinary medicine , pharmacology , bacteria , pharmacokinetics , medicine , biochemistry , genetics
The antimicrobial properties of tulathromycin were investigated for M. haemolytica and P. multocida . Three in vitro indices of antimicrobial activity, minimum inhibitory concentration ( MIC ), minimum bactericidal concentration ( MBC ) and time‐kill curves, were established for six isolates of each organism. Each index was measured in two growth media: Mueller–Hinton broth ( MHB ) and calf serum. It was shown that MIC s and MBC s were markedly lower in serum than in MHB . MHB :serum ratios for MIC were 47:1 ( M. haemolytica ) and 53:1 ( P. multocida ). For both serum and MHB , adjustment of pH led to greater potency at alkaline compared to acid pH . Tulathromycin MIC was influenced by size of inoculum count, being 4.0‐ to 7.7‐fold greater for high compared to low initial counts. It was concluded that for the purpose of determining dosages for therapeutic use, pharmacodynamic data for tulathromycin should be derived in biological fluids such as serum. It is hypothesized that in vitro measurement of MIC in broth, conducted according to internationally recommended standards, may be misleading as a basis for estimating the in vivo potency of tulathromycin.