High occurrence of multidrug-resistant Escherichia coli from Holstein-Friesian cattle in Northern Portugal: a One Health challenge

Background: Escherichia coli is currently a leading pathogen for deaths associated with antimicrobial resistance (AMR) [1]. AMR related to food-producing animals is a public health risk requiring a One Health approach [1,2]. Animals are major reservoirs of antibiotic resistant E. coli which can easily reach humans through the food chain, direct contact, or the environment [3]. Objective: To analyze the AMR profiles of E. coli in fecal samples from Holstein-Friesian cattle, as information on AMR from dairy farming in Portugal is scarce. Methods: Samples (n=112) collected from 7 different farms at Northern Portugal were pooled during February-March 2023 based on age group (8 calves and 8 cows per farm). Characteristic E. coli colonies were selected from MacConkey Agar supplemented with or without antibiotics (4 µg/ml cefotaxime; 3 µg/ml colistin), for confirmation by MALDI-TOF mass spectrometry and antimicrobial susceptibility testing (AST), according to EUCAST/CLSI guidelines. ESBL phenotype were searched using the Double-Disk Synergy Test. Results: Presumptive E. coli isolates (n=110) representing different farming production systems were obtained and 51 representatives were identified by MALDI-TOF and tested by AST. From both calves and cows, 95% and 63% of the E. coli isolates exhibited resistance to ≥1 antimicrobial classes and multidrug resistance (MDR, resistance to ≥3 antimicrobial classes), respectively. Isolates were mostly resistant to gentamycin (88%), ampicillin (72%), amoxicillin plus clavulanic acid (63%), tetracycline (63%) and cefotaxime (53%). Only two isolates showed susceptibility two all tested antibiotics. ESBL activity was observed in 21% of E. coli isolates. All analyzed pools were classified as MDR. Conclusions: This is one of the first studies on AMR rates of E. coli from dairy cattle in Northern Portugal. It reveals a high prevalence of MDR E. coli, which is a worrying finding and emphasize the need of a multisectoral One Health approach to minimize its impact.
Scientific Letters, Vol. 1 No. Sup 1 (2023)