Ana Paola Zogbi

Background/Objectives: The expansion of intensive swine production in Córdoba, Argentina, underscores the need to assess the risks associated with antimicrobial (AM) use, whose extensive application has driven antimicrobial resistance, a major global threat within the One Health framework. This study aimed to characterize AM use practices and evaluate the epidemiological resistance profiles (non-wild-type phenotypes, NWT) of commensal Escherichia coli of fecal origin from swine farms, using epidemiological cut-off values (ECOFFs) as a surveillance criterion. Methods: An observational cross-sectional study was conducted in 19 farrow-to-finish farms in Córdoba during 2023. Information on AM use (prophylaxis, metaphylaxis, treatment) across production categories was collected. A total of 437 E. coli isolates were obtained from fecal samples, and minimum inhibitory concentrations (MICs) were determined for 10 AMs of critical importance for human and animal health. NWT phenotypes were classified according to EUCAST ECOFFs, and multidrug resistance (MDR) was assessed. Results: AM use was frequent and predominantly prophylactic (89.5% of farms), mainly through mass medication (66.3%), with macrolides and amoxicillin being the most commonly administered AMs. NWT proportions were extremely high (90–92%) for ampicillin, tetracyclines, and chloramphenicol and substantial for ciprofloxacin (50.6%), sulfamethoxazole (68.2%), and trimethoprim (44.9%). Extended-spectrum β-lactamase (ESBL)-producing phenotypes were detected. Alarmingly, 92% of isolates were classified as MDR E. coli, with homogeneous distribution across production categories. Conclusions: Findings reveal intensive and largely empirical AM use that has consolidated a stable intestinal resistome in the swine population. High MDR levels, even in categories with limited direct AM exposure or involving banned compounds, suggest that co-selection and horizontal gene transfer are key drivers of resistance. This scenario highlights the urgent need to strengthen integrated surveillance and promote prudent AM use strategies under the One Health approach to preserve therapeutic efficacy.

La diarrea posdestete (DPD) es un importante problema sanitario y económico en la producción porcina, donde Escherichia coli enterotoxigénica (ETEC) constituye uno de los principales agentes causales, provocando diarrea y retraso en el crecimiento, lo que conlleva un mayor uso de antimicrobianos y, en consecuencia, un incremento del riesgo de resistencia bacteriana. El objetivo de este estudio fue aislar cepas de E. coli a partir de muestras fecales de lechones con DPD en granjas de la provincia de Córdoba, Argentina, describir su perfil de resistencia a antimicrobianos de importancia crítica en salud pública y/o animal, y realizar su caracterización genotípica. Se recolectaron 69 muestras de hisopado rectal en seis establecimientos, con una tasa de aislamiento de E. coli del 97%. Se observó un perfil de resistencia preocupante, con altos niveles frente a betalactámicos (98,5%), fenicoles (88%), tetraciclinas (86,6%) y aminoglucósidos (34,3%). Además, 62 cepas (92,5%) fueron clasificadas como multirresistentes. De los 67 aislamientos obtenidos, el 70% correspondió a cepas ETEC, con alta prevalencia de los genes estII (74,5%) y estI (63,8%), asociados a la producción de toxinas. También se detectaron genes de adhesión como fedA (21,3%), faeG (14,9%), aidA (25,5%) y astA (14,9%). Estos resultados evidencian la fuerte presión de selección ejercida sobre las poblaciones bacterianas en los sistemas productivos, favoreciendo la persistencia y diseminación de cepas multirresistentes, y subrayan la necesidad de implementar medidas de control más estrictas para reducir su propagación en la producción porcina, con implicancias directas para la salud pública y bajo el enfoque de Una Salud.