Salmonella enterica isolated from a Brazilian beef production chain: Prevalence, virulence genotypes, sanitizer and antimicrobial susceptibility, and biofilm formation ability

In Brazil, meat production holds significant economic importance for the domestic market and international exports. Ensuring the microbiological safety of meat products requires continuous monitoring through the production chain. In this context, the present study aimed to: (i) evaluate the occurrence of Salmonella spp. in slaughterhouses and beef cuts at retail stores in southern Brazil; (ii) determine the isolates’ susceptibility to antimicrobials and sanitizers; (iii) assess their potential for biofilm formation; and (iv) test the efficacy of essential oils in removing established biofilms. A total of 100 bovine carcasses were sampled, and Salmonella spp. was detected in six (6%) of them. Contamination was identified after the final washing (4%), after evisceration (2%), and after bleeding (1%). No Salmonella spp. was detected in beef cuts from retail stores or in fecal samples from slaughterhouse employees. All isolates were identified as Salmonella enterica subsp. enterica serovar Agona and carried the virulence genes hilA and invA; three isolates also harbored spvC , pefA , and sefA . Antimicrobial susceptibility testing revealed that all isolates were susceptible to ampicillin, amoxicillin, ceftazidime, tobramycin, tetracycline, sulfamethoxazole/trimethoprim, and chloramphenicol. Intermediate susceptibility was observed for imipenem, and one isolate also showed intermediate susceptibility to ciprofloxacin. Among the sanitizers tested – peracetic acid, benzalkonium chloride, chlorhexidine, and sodium hypochlorite – only chlorhexidine was effective, with a minimum inhibitory concentration (MIC) of 8 µg.mL -1 . The isolates demonstrated the ability to form biofilms on stainless steel coupons at 4 °C, 25 °C, and 37 °C after 24 h of incubation. Among the essential oils evaluated, only white thyme oil was effective, exhibiting inhibition zone of 18–26 mm, a MIC and minimum bactericidal concentration (MBC) of 29.06 mg.mL -1 (3.125%), and excellent efficacy in removing Salmonella biofilm from stainless steel. These findings underscore the importance of rigorous hygiene and sanitary control measures in cattle slaughterhouses to mitigate the risk of Salmonella contamination and persistence. • Salmonella Agona was detected in bovine carcasses at slaughter in Southern Brazil. • Salmonella isolates presented spvC , pefA , and sefA genes. • The isolates showed potential for biofilm formation on stainless steel coupons. • White thyme essential oil displayed high efficacy in the removal of Salmonella biofilm.