Frequency, serotyping and antimicrobial resistance pattern of Salmonella from feces and lymph nodes of pigs

Abstract

Resumo.-[Isolamento, sorotipagem e padrões de resistência a antimicrobianos de Salmonella em fezes e linfonodos de suínos.] Nas últimas décadas, o aumento de cepas circulante de Salmonella concomitantemente a resistência microbiana tem despertado a preocupação dos órgãos de Saúde Pública. Deste modo, o objetivo do presente trabalho foi pesquisar a presença de Salmonella a partir de fezes (n=50), linfonodos mediastinos (n=50), mesentéricos (n=50) e submandibular (n=50) oriundos de um abatedouro suíno. As cepas isoladas foram sorotipadas e testadas quanto a resistência antimicrobiana. A presença de Salmonella isolada foram em 10% (20/200) do total de amostras, sendo 20% dos linfonodos submandibulares, 18% dos linfonodos mesentéricos e 2% das fezes. Os sorotipos encontrados foram S. Typhimurium (55%), S. enterica subsp. enterica 4,5,12: i: -(35%), S. Brandenburg (5%) e S. Salmonellosis is a foodborne disease caused by bacteria of the genus Salmonella, being pigs and pork-products potentially important for its occurrence. In recent decades, some serovars of Salmonella have shown increase of resistance to conventional antimicrobials used in human and animal therapy, with serious risks for public health. The aim of this study was to evaluate feces (n=50), mediastinal (n=50), mesenteric (n=50) and mandibular (n=50) lymph nodes obtained from slaughter houses for Salmonella spp. Positive samples were serotyped and subjected to an in vitro antimicrobial susceptibility test, including the extended-spectrum beta-lactamase (ESBL) production. Salmonella species were identified in 10% (20/200) of total samples. From these, 20% (10/50) were identified in the submandibular lymph nodes, 18% (9/50) in the mesenteric lymph nodes, 2% (1/50) in feces and 0% (0/50) in the mediastinal lymph nodes. The serotypes found were Salonella Typhimurium (55%), S. enterica subsp. enterica 4,5,12: i: -(35%), S. Brandenburg and S. Derby with 5% (5% each). All strains showed resistance to at least one antimicrobial; 90% were resistant to four or more antimicrobials, and 15% were multidrug-resistant. Resistance to ciprofloxacin, tetracycline and nalidixic acid was particularly prevalent amongst the tested serovars. Here, we highlighted the impact of pigs in the epidemiological chain of salmonellosis in domestic animals and humans, as well as the high antimicrobial resistance rates of Salmonella strains, reinforcing the necessity for responsible use of antimicrobials for animals as an emergent One Health issue, and to keep these drugs for human therapy approaches.

Multidrug-resistant Salmonella spp. in fecal samples of pigs with suspected salmonellosis in Antioquia, Colombia, 2019–2021

“…S. Typhimurium and its monophasic variant were the predominant serotypes and accounted for about 90% of all isolates. This finding is similar to the findings in other countries of the European Union, Brazil, China, Japan, and the United States ( 4 , 32 , 33 ). Although studies from other parts of the world also report Derby as another common serotype ( 34 ), we did not find this serotype in our study, nor did we detect S. Choleraesuis.…”

“…Of concern in our study was the high prevalence of MDR (44%) – much higher than a previous study in Colombia which reported MDR of 12% ( 11 ). MDR was significantly higher in S. Typhimurium than the other serotypes, similar to reports from Brazil and China ( 32 , 33 ). These trends could be a consequence of unregulated antimicrobial use in pig production ( 11 ), but further investigation on the levels of antimicrobial use in pig farming is needed to evaluate this hypothesis.…”

“…Chloramphenicol, ciprofloxacin, sulfamethoxazole–trimethoprim, and ceftriaxone are the first choices for treating salmonellosis in humans and are designated by WHO as critically and highly important for human medicine ( 27 ). Brazil, Korea, and Spain have observed similar resistance patterns with percentages of 80%, 94%, and 70%, respectively ( 32 , 34 ). Of concern in our study was the high prevalence of MDR (44%) – much higher than a previous study in Colombia which reported MDR of 12% ( 11 ).…”

Pathogenicity and Competitive Fitness of Salmonella enterica Serovar 4,[5],12:i:- Compared to Salmonella Typhimurium and Salmonella Derby in Swine

“…The rise in prevalence of Salmonella 4, [5],12:i:-in livestock and humans also raises the question of why the serovar has recently emerged and become increasingly prevalent. Salmonella 4, [5],12:i:-has repeatedly been reported to be more highly resistant to antimicrobials relative to S. Typhimurium (6,31,32), which may provide a significant advantage to its survival in swine operations with extensive antimicrobial drug use. Likewise, S. 4, [5],12:i:-is commonly resistant to heavy metals such as zinc and copper, which can be added to livestock feeds as an alternative to antibiotics to reduce bacterial infections (16,33).…”