Moreno Romo, Miguel ÁngelGarcía Soto, SilviaHernández, MartaBárcena Asensio, María CarmenRodríguez Lázaro, DavidUgarte Ruiz, MaríaDomínguez Rodríguez, Lucas José2024-11-292024-11-292019Moreno, M. A., García-Soto, S., Hernández, M., Bárcena, C., Rodríguez-Lázaro, D., Ugarte-Ruíz, M., & Domínguez, L. (2019). Day-old chicks are a source of antimicrobial resistant bacteria for laying hen farms. Veterinary microbiology, 230, 221–227. https://doi.org/10.1016/j.vetmic.2019.02.0070378-11351873-254210.1016/j.vetmic.2019.02.007https://hdl.handle.net/20.500.14352/111250Antimicrobial resistant bacteria are rarely detected in laying hens and the objective of this longitudinal study was to test day-old chick as a source. Four different commercial batches raised on the same farm were monitored from day-old chick to laying hens using Escherichia coli as a model. Ten colonies from each of the eight samplings per batch were tested for antimicrobial susceptibility using 14 antimicrobials. Overall (313 isolates), higher resistance percentages were detected for tetracycline (26.8%), followed by sulphonamides (16.3%), ampicillin (16.0 %) and quinolones (10.9% and 9.3% for ciprofloxacin and nalidixic acid, respectively). Resistance percentages of bacteria from day-old chicks were higher than those of pullets and hens (p < 0.05) for tetracycline, sulphonamides, trimethoprim and chloramphenicol. Forty different phenotypic resistance profiles were detected, led by fully susceptible (182 isolates; 58.1%), and followed by single tetracycline (28 isolates; 8.9%) and ciprofloxacin/ nalidixic acid (11 isolates; 3.5%) profiles. By whole-genome sequencing, 17 genes and mutations of five chromosomal genes related to resistance were detected, the most frequent being tetA, blaTEM-1B and sul1. Using multilocus sequencing analysis, 58 different MLST types were detected, most of them only in a particular sample. The ST155 (27/142) was the most frequently detected, followed by ST10 (19/142) and ST48 (9/142). The fate on the farm of the detected E. coli populations in old-day chicks was not clear, but our data suggest that they did not remain in the predominant faecal population of pullets and laying hens.engAttribution 4.0 Internationalhttp://creativecommons.org/licenses/by/4.0/journal articlehttps://doi.org/10.1016/j.vetmic.2019.02.00730277158restricted access636.09Escherichia coliEgg productionAntibioticWGSMLTSAntimicrobial resistanceVeterinaria3109 Ciencias Veterinarias