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Vet Microbiol. 2019 Mar;230:221-227. doi: 10.1016/j.vetmic.2019.02.007. Epub 2019 Feb 13.

Day-old chicks are a source of antimicrobial resistant bacteria for laying hen farms.

Author information

1
VISAVET Health Surveillance Centre, Universidad Complutense, Avda. Puerta de Hierro s/n, 28040, Madrid, Spain; Departamento de Sanidad Animal, Facultad de Veterinaria, Universidad Complutense, Avda. Puerta de Hierro s/n, 28040, Madrid, Spain. Electronic address: mamoreno@ucm.es.
2
VISAVET Health Surveillance Centre, Universidad Complutense, Avda. Puerta de Hierro s/n, 28040, Madrid, Spain.
3
Laboratorio de Biología Molecular y Microbiología, Instituto Tecnológico Agrario de Castilla y León, 47071, Valladolid, Spain; Área de Microbiología, Departamento de Biotecnología y Ciencia de los Alimentos, Universidad de Burgos, 09001, Burgos, Spain.
4
Área de Microbiología, Departamento de Biotecnología y Ciencia de los Alimentos, Universidad de Burgos, 09001, Burgos, Spain.
5
VISAVET Health Surveillance Centre, Universidad Complutense, Avda. Puerta de Hierro s/n, 28040, Madrid, Spain; Departamento de Sanidad Animal, Facultad de Veterinaria, Universidad Complutense, Avda. Puerta de Hierro s/n, 28040, Madrid, Spain.

Abstract

Antimicrobial 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.

KEYWORDS:

Antibiotic; Antimicrobial resistance; Egg production; Escherichia coli; MLST; WGS

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