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Loop-mediated Isothermal Amplification (LAMP) Assays for the Species-specific Detection of Eimeria that Infect Chickens
Published on: February 20, 2015
Mutant-prevention concentrations of enrofloxacin for Escherichia coli isolates from chickens
Qianxue Li1, Xingming Bi, Youjiang Diao
1Department of Basic Veterinary Science, College of Animal Science and Veterinary Medicine, Jilin University, Changchun 130062, PR China.
Objective:
To investigate the development of enrofloxacin resistance among Escherichia coli isolates obtained from chickens by determining mutant-prevention concentrations (MPCs) and sequence the quinolone resistance-determining regions (QRDRs) of gyrA and parC genes in selected isolates.
Sample Population:
15 chicken-derived E coli isolates.
Procedures:
For all isolates, MPC and minimal inhibition concentration (MIC) of enrofloxacin were determined. The MPCs and maximum serum drug concentrations attained with enrofloxacin doses recommended for treatment of E coli infections in chickens were compared. Mutation frequencies and QRDR sequence changes in gyrA and parC were also determined.
Results:
In 2 of 15 E coli strains, MPCs were low (0.016 and 0.062 microg/mL), MPC:MIC ratios were 2 and 4, and the GyrA and ParC proteins had no mutations. In 9 susceptible isolates with a GyrA point mutation, MPCs ranged from 2 to 16 microg/mL. For isolates with double mutations in GyrA and a single mutation in ParC, MPCs were > 32 microg/mL (several fold greater than the maximal plasma concentration of enrofloxacin in chickens); mutation frequencies were also much lower, compared with frequencies for single-mutation isolates.
Conclusions And Clinical Relevance:
For E coli infections of chickens, MPC appears to be useful for determining enrofloxacin-dosing strategies. The high MPC:MIC ratio may result in enrofloxacin-treatment failure in chickens infected with some wild-type gyrA E coli isolates despite the isolates' enrofloxacin susceptibility (MICs 0.125 to 1 microg/mL). For infections involving isolates with high MPCs, especially those containing mutations in gyrA and parC genes, treatment with combinations of antimicrobials should be adopted.
Insights
Mutant-prevention concentrations (MPCs) reveal enrofloxacin resistance in chicken E. coli. High MPCs indicate potential treatment failure and necessitate combination antimicrobial therapy for effective E. coli infection control in poultry.
Area of Science:
- Veterinary Microbiology
- Antimicrobial Resistance
- Poultry Health
Background:
- Enrofloxacin is crucial for treating Escherichia coli (E. coli) infections in chickens.
- Understanding enrofloxacin resistance mechanisms is vital for maintaining treatment efficacy.
- Mutant-prevention concentration (MPC) offers insights into antimicrobial resistance dynamics.
Purpose of the Study:
- To determine enrofloxacin resistance in chicken E. coli isolates using MPCs.
- To analyze mutations in gyrA and parC genes associated with resistance.
- To inform optimal enrofloxacin dosing strategies for poultry.
Main Methods:
- Analyzed 15 chicken-derived E. coli isolates.
- Determined enrofloxacin's mutant-prevention concentration (MPC) and minimal inhibitory concentration (MIC).
- Sequenced quinolone resistance-determining regions (QRDRs) of gyrA and parC genes.
Main Results:
- Two isolates showed low MPCs with no gyrA/parC mutations.
- Nine susceptible isolates with a gyrA mutation had MPCs ranging from 2 to 16 microg/mL.
- Isolates with multiple gyrA/parC mutations exhibited MPCs exceeding 32 microg/mL, surpassing chicken plasma concentrations.
Conclusions:
- MPC is valuable for guiding enrofloxacin dosing in chicken E. coli infections.
- High MPC:MIC ratios can lead to treatment failure even in susceptible isolates.
- Combination antimicrobial therapy is recommended for E. coli infections with high MPCs or gyrA/parC mutations.
