High-Frequency Detection of fosA3 and bla CTX-M- 55 Genes in Escherichia coli From Longitudinal Monitoring in Broiler Chicken Farms

Considering the worrying emergence of multidrug resistance, including in animal husbandry and especially in food-producing animals, the need to detect antimicrobial resistance strains in poultry environments is relevant, mainly considering a One Health approach. Thus, this study aimed to conduct longitudinal monitoring of antimicrobial resistance in broiler chicken farms, with an emphasis on evaluating the frequency of resistance to fosfomycin and β-lactams. was isolated from broiler chicken farms (cloacal swabs, meconium, poultry feed, water, poultry litter, and ) in northern Paraná from 2019 to 2020 during three periods: the first period (1st days of life), the second period (20th to 25th days of life), and third period (40th to 42nd days of life). Antibiogram tests and the detection of phenotypic extended-spectrum β-lactamase (ESBL) were performed, and they were confirmed by seaching for genes from the group. The other resistance genes searched were and . Some ESBL group strains were selected for ESBL identification by sequencing and enterobacterial repetitive intergenic consensus-polymerase chain reaction analysis. To determine the transferability of the and -carrying plasmids, strains were subjected to conjugation experiments. A total of 507 were analyzed: 360 from cloacal swabs, 24 from meconium samples, 3 from poultry feed samples, 18 from water samples, 69 from poultry litter samples, and 33 from samples. Among the strain isolate, 80% (406/507) were multidrug-resistant (MDR), and 51% (260/507) were ESBL-positive, with the group being the most frequent. For the gene, 68% (344/507) of the strains isolated were positive, deserves to be highlighted isolated from day-old chickens (OR 6.34, CI 2.34-17.17), when compared with strains isolated from other origins (poultry litter, , water, and poultry feed). This work alerts us to the high frequency of the gene correlated with the CTX-M-1 group (OR 3.57, CI 95% 2.7-4.72, < 0.05), especially the gene, in broiler chickens. This profile was observed mainly in day-old chicken, with a high percentage of that were MDR. The findings emphasize the importance of conducting longitudinal monitoring to detect the primary risk points during poultry production.