Anatomo-pathological investigations in pigs of the Piedmont region (Northern Italy) for infectious diseases surveillance in an antimicrobial resistance perspective

Intensive breeding responds to the expanding market demand and animal health must be guaranteed to safeguard human and Public Health. Pig farming has grown in the last decades, leading to increased animal stress, pathogens dissemination, and the consequent use of antibiotics and the spread of antimicrobial-resistant bacteria. The present study aimed to describe the anatomopathological findings observed during necropsies performed from 2019 to 2021 on deceased pigs from five intensive breeding farms in northwestern Italy also reporting bacterial isolations, antimicrobial susceptibility testing, and virological results. Weaned pigs (WP) (N = 143) represented the majority of the carcasses, while the remaining part (N = 49) were fattening pigs (FP). Most of WP were affected by systemic disease (N = 79, 55.2 %), whereas 49 % of FP were affected by respiratory disease (N = 24). Streptococcus suis was the most frequently isolated microorganism in respiratory (around 20 % in both WP and FP) and systemic cases (25.3 % in WP and 33.3 % in FP). Enteric disorders were attributable to Brachyspira spp. and Escherichia coli in WP and FP (44.5 % and 55.5 %, respectively). Escherichia coli was considered to be the second causative agent of systemic disease (22.8 %) in WP. Streptococcus suis and monophasic Salmonella Typhimurium were isolated and demonstrated a high rate of multi-drug resistance (84 % and 100 %, respectively): the first showed resistance mainly against tetracyclines (100 %), lincosamides (88 %) and macrolides (84 %), whereas the latter to tetracyclines, sulfametox-trimethoprim, ampicillin, florfenicol, and enrofloxacin. Necropsy and microbiological assays are powerful tools for disease surveillance programs, highlighting potential risks for public health.