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. 2025 Jun 11;13(6):1354.
doi: 10.3390/microorganisms13061354.

Nasal Colonizers from Sows in the Federal District of Brazil Showed a Diverse Phenotypic Resistance Profile

Luciana Lana Rigueira  1   2 , Fabiano José Ferreira de Sant'Ana  1 , Bruno Stéfano Lima Dallago  1 , Rômulo Salignac Araújo de Faria  1 , Maurício Macedo Rodrigues  1 , Pau Obregon-Gutierrez  3 , Virginia Aragon  3 , Simone Perecmanis  1
Affiliations

Nasal Colonizers from Sows in the Federal District of Brazil Showed a Diverse Phenotypic Resistance Profile

Luciana Lana Rigueira et al. Microorganisms. .

Abstract

Antimicrobial resistance (AMR) is a major public health concern influenced by antimicrobial use (AMU) in animal production systems. In swine, metaphylactic treatments may contribute to the emergence and dissemination of resistance genes. In this study, we isolated bacteria from the nasal cavities of 50 sows across 10 farms in the Federal District, Brazil. A total of 132 bacterial isolates were obtained and tested for phenotypic resistance to 23 antimicrobials using the disk diffusion method. Resistance was detected against all tested antimicrobials, with an overall resistance rate of 55.6% (1605/2888 tests). The highest resistance rates were observed for bacitracin (92.4%) and penicillin (79.2%), while lower resistance rates were found for aminoglycosides. Most isolates exhibited multidrug resistance to 7-9 classes of antimicrobials, including strains of Staphylococcus, Escherichia coli, and Klebsiella-all of which are relevant in the context of One Health. Actinobacillus suis showed the highest resistance levels among all identified species. AMR was positively correlated with both the duration and the number of antimicrobial agents used in feed, reinforcing the need for prudent AMU practices. The use of autogenous vaccines against Pasteurella multocida was associated with reduced lung lesions, underscoring the value of vaccination in disease control. AMR surveillance programs may benefit from including bacterial colonizers from the microbiota, though further studies are necessary to better understand the resistance dynamics of these commensals.

Keywords: antimicrobial resistance; metaphylaxis; nasal microbiota; swine.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Percentage of antimicrobial resistance per bacterial species. Nasal isolates from sows from ten farms were tested for antimicrobial susceptibility. The results are presented as box-plots, with a horizontal line indicating the median value and the box representing the middle 50% of the observed values. The results are organized by bacterial species and represent the percentage of resistance (the number of tests giving a resistance result with respect to the total number of tests). The farms are represented with different colors following the legend on the right of the graph. Raw data can be found in Tables S1 and S3.
Figure 2
Figure 2
Percentage of antimicrobial resistance per farm. Nasal isolates from sows from ten farms were tested for antimicrobial susceptibility. The results are presented as box-plots, with a horizontal line indicating the median value and the box representing the middle 50% of the observed values. The results are organized by farm and presented in percentage of resistance (the number of tests giving a resistance result with respect to the total number of tests in each bacterial species). The bacterial species are represented with different colors following the legend on the right of the graph. Raw data can be found in Tables S1 and S3.
Figure 3
Figure 3
Distribution of number of resistances, including MDR (multi-drug resistance), in the bacterial isolates from the nasal cavities of sows obtained in this study.
See this image and copyright information in PMC

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