Prevalence, antimicrobial resistance and detection of resistance genes of Escherichia coli and Salmonella spp. isolated from captive European wild boars reared in Brazil

Abstract

The expansion of invasive European wild boar ( Sus scrofa scrofa ) populations in Brazil and the increasing commercialization of this species raise concerns about their role as reservoirs of zoonotic and antimicrobial-resistant bacteria. This study aimed to determine the prevalence, antimicrobial resistance profiles, and detection of virulence and resistance genes in Escherichia coli and Salmonella spp. isolated from captive wild boars. A total of 100 rectal swab samples were collected from animals raised on commercial farms in Goiás State, Brazil. One Salmonella isolate (1%) was detected and identified as serotype O:6,8, showing phenotypic resistance to ampicillin, amoxicillin, and sulfonamides, but no virulence or resistance genes were detected. E. coli was isolated from 56% of samples, with 98.2% of isolates classified as multidrug-resistant and all presenting antimicrobial resistance index values above 0.2. High resistance rates were observed for sulfonamides (96.8%), tetracycline (92.1%), amoxicillin (87.3%), ampicillin (85.7%), doxycycline (81.0%), whereas most isolates remained susceptible to ceftriaxone. Virulence genes were detected in a subset of isolates, including tsh (29.8%), papC (12.3%), and iss (7.0%), with some isolates presenting gene combinations associated with increased pathogenic potential. The eae gene was not detected, and no β-hemolytic activity was observed. These findings indicate a low occurrence of Salmonella but a high prevalence of multidrug-resistant and potentially pathogenic E. coli in captive wild boars, highlighting their potential role as reservoirs of antimicrobial resistance within a One Health context.

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