Frequency, Resistance Patterns, and Serotypes of Salmonella Identified in Samples from Pigs of Colombia Collected from 2022 to 2023

The objective of this study was to determine the frequency of Salmonella in pig samples analyzed at the Veterinary Diagnostic Unit of the Faculty of Agricultural Sciences of the University of Antioquia, Colombia, between 2022 and 2023. Out of 5820 serum samples analyzed using indirect enzyme-linked immunosorbent assay, 63.76% were positive. Additionally, Salmonella was isolated and identified in a separate group of 848 samples (feces, tissues, etc.) with a positivity rate of 23.47%. Eight serotypes were identified, with the most common being Salmonella enterica subsp. enterica serotype Typhimurium (49.2%), followed by its monophasic variant I 4,[5],12:i:- (23%), and serotype Choleraesuis (18%). Antimicrobial susceptibility profiles of 105 isolates were evaluated using the Kirby–Bauer method, which demonstrated higher resistance (100%) to ampicillin, tiamulin, penicillin, tylosin, and erythromycin (these were the least tested), followed by florfenicol (44/54), doxycycline (4/5), spectinomycin (18/25), amoxicillin (32/46), chloramphenicol (2/3), tetracycline (2/3), and enrofloxacin (34/64), with lower resistance observed for fosfomycin (2/38) and ceftiofur (5/35). Multi-drug resistance was observed in 59% (62/105) of the isolates. The high proportion of Salmonella and the levels of resistance to various drugs raise significant concerns, indicating potential deficiencies in responsible antimicrobial use and management practices on pig farms in the region.