Evidence of the wide circulation of multi-drug resistant enteric strains in lesser kestrel (Falco naumanni)

This study was aimed to assess the circulation of antimicrobial-resistant, Gram-Negative enteric bacteria in wild birds. Specifically, cloacal swabs were collected from 32 lesser kestrels (Falco naumanni) hosted in the apulian wildlife rescue centre in July 2021. All samples were collected upon admittance as part of the routine diagnostic procedures. Swabs were incubated in tryptic soy broth (TSB) with enrofloxacin (enr), selected on McConkey agar with enr, and identified biochemically or by MALDI-TOF. Susceptibility of isolates to the most common antibiotic classes was ascertained by the disc diffusion method. Only one out of 32 samples (3,12%) showed no bacteria growth. From the remaining 31 birds, 41 enr-resistant strains were isolated, specifically 23 Escherichia coli, 10 Proteus mirabilis, 6 Klebsiella pneumoniae, 1 Citrobacter freundii, and 1 Enterobacter cloacae. Out of them, 39 (95.12%) were resistant to three or more antibiotics.In detail, 35 strains were resistant to tet, 32 to amp, and 25 to sxt or streptomycin (str). No cst-resistant strain was isolated except for P. mirabilis, naturally resistant. No strain was resistant to ipm, but 7 were resistant to the fourth-generation cephalosporin cefepime (fep). Those data suggest a wide circulation of multi-drug resistant (MDR) strains, some of them with clinical relevance, in birds that were never treated with antibiotics. Considering its migratory habits, and its position at the top of the food chain, F. naumanni should be considered an important indicator of the flow of MDR bacteria between anthropic and wild environments, providing useful information in a One Health view. "The antibiotic names have been abbreviated according to the indications of the British Society for Antimicrobials Chemotherapy, unless otherwise specified".