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.
BACKGROUND
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 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.


RESULTS
The MIC50/MIC90values 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/ MPC90values 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.


CONCLUSIONS
Based 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.
Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, South China Agricultural University, Guangzhou, 510642, People's Republic of China.
Yafei
Y
Li
Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, South China Agricultural University, Guangzhou, 510642, People's Republic of China.
Yanan
Y
Zhang
Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, South China Agricultural University, Guangzhou, 510642, People's Republic of China.
Huanzhong
H
Ding
Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, South China Agricultural University, Guangzhou, 510642, People's Republic of China.
Xian
X
Mei
Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, South China Agricultural University, Guangzhou, 510642, People's Republic of China.
Wei
W
Liu
Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, South China Agricultural University, Guangzhou, 510642, People's Republic of China.
Jiaxiong
J
Zeng
Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, South China Agricultural University, Guangzhou, 510642, People's Republic of China. zlzeng@scau.edu.cn.
Zhenling
Z
Zeng
D000818:Animals; D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics / Q000494:pharmacology*; D002511:Cephalosporins / Q000493:pharmacokinetics / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial / Q000235:genetics; D004372:Ducks / Q000382:microbiology; D045826:Flavobacteriaceae Infections / Q000382:microbiology / Q000662:veterinary; D005777:Geese / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D009154:Mutation; D011201:Poultry Diseases / Q000382:microbiology; D060494:Riemerella / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D013839:Thiamphenicol / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000494:pharmacology; D015645:Tylosin / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D002511:Cephalosporins; C053503:ceftiofur; C035534:florfenicol; D013839:Thiamphenicol; C052319:tilmicosin; D015645:Tylosin; C068212:cefquinome
Minimum inhibitory concentration; Mutant prevention concentration; R. anatipestifer