In vitro susceptibility of four antimicrobials against Riemerella anatipestifer isolates: a comparison of minimum inhibitory concentrations and mutant prevention concentrations for ceftiofur, cefquinome, florfenicol, and tilmicosin.

Yafei Li,Xian Mei,Jiaxiong Zeng,Wei Liu,Yanan Zhang,Huanzhong Ding,Zhenling Zeng

doi:10.1186/s12917-016-0796-3

Yafei Li, Xian Mei + Show 5 more

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https://doi.org/10.1186/s12917-016-0796-3

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Abstract

BackgroundMutant prevention concentration (MPC) is an alternative pharmacodynamic parameter that has been used to measure antimicrobial activity and represents the propensities of antimicrobial agents to select resistant mutants. The concentration range between minimum inhibitory concentration (MIC) and MPC is defined as mutant selection window (MSW). The MPC and MSW parameters represent the ability of antimicrobial agents to inhibit the bacterial mutants selected. This study was conducted to determine the MIC and MPC values of four antimicrobials including ceftiofur, cefquinome, florfenicol and tilmicosin against 105 Riemerella anatipestifer isolates.ResultsThe MIC50/MIC90 values of clinical isolates tested in our study for ceftiofur, cefquinome, florfenicol and tilmicosin were 0.063/0.5、0.031/0.5、1/4、1/4 μg/mL, respectively; MPC50/ MPC90 values were 4/64、8/64、4/32、16/256 μg/mL, respectively. These results provided information on the use of these compounds in treating the R. anatipestifer infection; however, additional studies are needed to demonstrate their therapeutic efficacy.ConclusionBased on the MSW theory, the hierarchy of these tested antimicrobial agents with respect to selecting resistant subpopulations was as follows: cefquinome > ceftiofur > tilmicosin > florfenicol. Cefquinome was the drug that presented the highest risk of selecting resistant mutant among the four antimicrobial agents.

Highlights

Mutant prevention concentration (MPC) is an alternative pharmacodynamic parameter that has been used to measure antimicrobial activity and represents the propensities of antimicrobial agents to select resistant mutants
MPC values were higher than minimum inhibitory concentration (MIC) because of exposure to higher density of bacterial inoculum
MIC values of ceftiofur ranged from ≤0.008 to 8 μg/mL, with MIC50 and MIC90 values of 0.063 μg/mL and 0.5 μg/mL respectively; cefquinome had the MIC values ranging between ≤0.008 to 16 μg/mL, with MIC50 of 0.031 μg/ mL and MIC90 of 0.5 μg/mL respectively; florfenicol had the MIC values ranging from 0.125 to 16 μg/mL, with MIC50 of 1 μg/mL and MIC90 of 4 μg/mL respectively; tilmicosin had the MIC values ranging from 0.031 to 64 μg/mL, with MIC50 of 1 μg/mL and MIC90 of 4 μg/ mL respectively

Summary

Introduction

Mutant prevention concentration (MPC) is an alternative pharmacodynamic parameter that has been used to measure antimicrobial activity and represents the propensities of antimicrobial agents to select resistant mutants. The MPC and MSW parameters represent the ability of antimicrobial agents to inhibit the bacterial mutants selected. Riemerella anatipestifer has been one of the most troublesome etiological agents and causes heavy loss in duck industry. It occurs worldwide, especially in Southeast Asia [1]. People have been making great efforts to find new strategies to prevent or control R. anatipestifer infection, since much work has been done concentrating on the identification of factors associated with virulence [1, 3, 4] and immunogenic characterization based on outer membrane protein A in recent years [5,6,7]. Due to the concern of high incidence of Riemerella anatipestifersis and increasingly severe drug resistance or reduction of susceptibility, obtaining new treatment information and promising results with antimicrobial agents seems necessary [8,9,10]

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