Manuela Maria Cavalcante Granja¹, Geísa Pinheiro Paes¹, Jefferson Viktor de Paula Barros Baêta¹, Thais Viana Fialho Martins¹, Guilherme Sávio de Barros Vasconcelos¹, Lucas Santos¹, Daniel Lúcio dos Santos¹, Walter Vieira Guimarães¹, José Lúcio dos Santos¹

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¹MICROVET - Microbiologia Veterinária Especial,Viçosa, Minas Gerais - BR. *Autor para correspondência: manuela@microvet.com.br

 

Palavras-chave: Salmonellosis, food safety, swine production.

 

Brazil is a global leader in pig farming, with over 90% of production concentrated in the South, Southeast, and Midwest regions. Despite advancements in biosecurity and sanitary practices, Salmonella spp. infections remain a major concern for public health and the swine production chain. Among the more than 2,600 known serovars, Salmonella Typhimurium and its monophasic variant (1,4,[5],12:i:-) are especially relevant due to their zoonotic potential, environmental persistence, and association with multi-drug resistance. The monophasic variant, increasingly reported worldwide, is linked to clinical diseases such as septicemia and enterocolitis in pigs during the nursery and growing phases. Its high isolation rate from carcasses, lymph nodes, and byproducts indicates widespread contamination from farm to slaughterhouse. The presence of resistance genes for tetracyclines, aminoglycosides, and sulfonamides further emphasizes the need for integrated control strategies. This study involved samples from pigs in Brazil’s major pig-producing regions collected between 2020 and May 2025. Tissues from the respiratory, hepatobiliary, and gastrointestinal systems were analyzed at the MicroVet Veterinary Diagnostic Laboratory. Salmonella spp. were identified using MALDI-TOF mass spectrometry, conventional serotyping, and PCR. The data were used to evaluate the distribution of S. Typhimurium and its monophasic variant across regions, years, and swine organ systems. The results show a clear shift in the prevalence of serovars over the past five years, with a sharp rise in the monophasic variant, which accounted for 99.7% of all S. Typhimurium isolates. In contrast, the classic S. Typhimurium serovar showed a declining trend: it was most prevalent in 2021 (43.4%) but dropped to 15.2% in 2024 and just 1.4% by May 2025. Geographically, 72.8% of isolates were from the South, followed by 14.5% from the Southeast and 12.7% from the Midwest. While this reflects regional production volumes, it may also indicate differences in biosafety practices, pig density, and production systems. In some southern slaughterhouses, S. Typhimurium appears in up to 30% of carcasses and waste, with increasing monophasic strain prevalence and antimicrobial resistance. Similar patterns are found in Southeast agro-industrial facilities, while the Midwest shows higher prevalence of both Typhimurium and Derby serovars, relevant for regional surveillance. Regarding organ type, intestinal samples had the highest isolation rate (69.3%), with a 99% dominance of the monophasic variant. Hepatobiliary tissues had a lower prevalence (6.42%). These findings reinforce the gastrointestinal origin and food safety relevance of S. Typhimurium. Additionally, 23.9% of isolates were from respiratory tissues, and 97.7% of these were monophasic, suggesting systemic bacterial spread and aligning with past reports of extraintestinal infections in clinically ill pigs. In conclusion, the monophasic variant of Salmonella Typhimurium has become the dominant strain in Brazil’s pig farming industry, demonstrating its adaptability, resistance, and capacity to cause systemic disease. This scenario underscores the urgent need for integrated monitoring, diagnostics, and control strategies, such as the development of autogenous vaccines, to reduce animal health risks and ensure food safety.

 

Referências

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• Almeida, F. et al. Virulence‐associated genes, antimicrobial resistance and molecular typing of Salmonella Typhimurium strains isolated from swine from 2000 to 2012 in Brazil. Journal of Applied Microbiology, v. 120, n. 6, p. 1677-1690, 2016.

• Bessa, M.C. el al. Prevalência de Salmonella sp em suínos abatidos em frigoríficos do Rio Grande do Sul. Pesquisa Veterinária Brasileira, v. 24, p. 80-84, 2004.

• Carneiro, A.M. Detecção de genes de resistência a fármacos antimicrobianos em genomas de Salmonella Typhimurium e variantes monofásicas. 2024. 

• Da Silva, D.G. et al. Use of organic acids to reduce Salmonella Typhimurium excretion in swine. Brazilian Journal of Veterinary Research and Animal Science, v. 60, p. e198402-e198402, 2023.

• Seribelli, A.AP et al. Insights about the epidemiology of Salmonella Typhimurium isolates from different sources in Brazil using comparative genomics. Gut Pathogens, v. 13, n. 1, p. 27, 2021.

• Pissetti, C. et al. Critically Important Antimicrobial Resistance Trends in Salmonella Derby and Salmonella Typhimurium Isolated from the Pork Production Chain in Brazil: A 16-Year Period. Pathogens, v. 11, n. 8, p. 905, 2022.

• Possebon, F.S. et al. Prevalence, antibiotic resistance, PFGE and MLST characterization of Salmonella in swine mesenteric lymph nodes. Preventive Veterinary Medicine, v. 179, p. 105024, 2020.

 

Tabela 1: Relationship between sample type and the isolation of Salmonella Typhimurium in pigs between 2021 and 2025 in the main producing regions of Brazil.

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Table 2. Quantitative isolation of Salmonella Typhimurium in pigs between 2021 and 2025 in the main producing regions of Brazil.

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