Antimicrobial resistance selection in avian pathogenic E. coli during treatment

Area of Science:

• Veterinary Microbiology
• Antimicrobial Resistance
• Poultry Health

Background:

• Colibacillosis, caused by avian pathogenic Escherichia coli (APEC), is a significant disease in poultry.
• Multidrug-resistant E. coli strains pose a growing threat, complicating treatment options.
• Understanding antimicrobial efficacy and resistance gene transfer is crucial for controlling poultry infections.

Purpose of the Study:

• To compare the microbiological efficacy of four antimicrobial treatments against experimental colibacillosis.
• To investigate the potential for antimicrobial resistance gene transfer during treatment.
• To evaluate the emergence of resistant E. coli isolates in internal organs of broilers.

Main Methods:

• Broilers were orally inoculated with multiresistant E. coli and subsequently infected with APEC.
• Birds received treatments including oxytetracycline, trimethoprim-sulphonamide, amoxicillin (AMX), or enrofloxacin (ENR).
• Internal organs were cultured on supplemented and non-supplemented media; molecular analysis was performed on resistant isolates.

Main Results:

• Enrofloxacin (ENR) significantly reduced APEC recovery (26%) compared to controls (47%).
• Other treatments showed no significant reduction in APEC recovery.
• Resistant isolates emerged, with one AMX-treated isolate showing potential plasmid-mediated resistance gene acquisition.

Conclusions:

• Enrofloxacin demonstrated superior microbiological efficacy in controlling experimental colibacillosis.
• Antimicrobial treatment can potentially drive the emergence and spread of resistant E. coli isolates.
• The study highlights the risk of acquiring resistance plasmids from the gut microbiota during treatment.