Antimicrobial resistance and R-plasmid in Salmonella spp from swine and abattoir environments

Pesquisa Veterinária Brasileira

Reis, Eliane M.F.³  Quintaes, Bianca R.³  Lázaro, Norma S.¹  Tibana, Anita²  Hofer, Ernesto³  Rodrigues, Dália P.³ 

[1] Universidade Federal Rural do Rio de Janeiro, Seropédica, Brasil;Universidade Federal do Rio de Janeiro, Rio de Janeiro;Departamento Bacteriologia, Rio de Janeiro

关键词: Salmonella;    swine;    antimicrobial resistance;    R-plasmid.;   

DOI  :  10.1590/S0100-736X2004000200001

来源: Colegio Brasileiro de Patologia Animal-CBPA

【 摘 要 】

Salmonella serovars isolated from swine are of particular interest not only because of the pathogenic potential for this animal species, but also due to its relevance with regard to public health. On basis of the profile of resistance to antimicrobials, 13 Salmonella strains were selected which belonged to the serovars Muenster (7), Derby (4), Typhimurium (1), and Braenderup (1). They were isolated from healthy swine as well as from the abattoir environment in the state of Rio de Janeiro. All strains of Salmonella were subjected to bacterial conjugation, and the E. coli K12 Nalr Lac+ F standard strain was used as receptor, with the purpose to verify the ability to transfer the resistance marks. Gene transfer phenomenon was detected in seven strains, and except SalmonellaTyphimurium which transconjugated to Sm, Tc and Su, the remaining ones were characterized by transferring mark Su only. By plasmidial analysis of strains used and their respective transconjugants, 63 Kb plasmid was found, which was probably related to S. Typhimurium resistance. Index terms: Salmonella, swine, antimicrobial resistance, R-plasmid. RESUMO Sorovares de Salmonella isolados de suinos são de particular interesse não só pelo potencial patogênico para esta espécie animal, como também pela sua relevância em Saúde Pùblica. Com base no perfil de resistência aos antimi-crobianos foram selecionadas 13 amostras de Salmonella pertencentes aos sorovares Muenster (7 amostras), Derby (4), Typhimurium (1) e Braenderup (1), isoladas de suinos sadios e do ambiente de abatedouro no Estado do Rio de Janeiro. As amostras foram submetidas a conjugação bacteriana, utilizando como receptora E.coli K12 55 Nal r Lac+ F -, com a finalidade de verificar a capacidade da transferência de marcos de resistência. O fenômeno de transferência gênica foi detectado em 7 amostras e, com exceção de Salmonella Typhimurium que transconjugou para Sm, Tc e Su, as demais se caracterizaram por transferir somente o marco Su. Na análise plasmidial das amostras doadoras e suas respectivas transconjugantes foi revelado um plasmídio de 63 Kb, provavelmente relacionado com a multirresistência de S. Typhimurium. Termos de indexação: Salmonella, suínos, resistência antimicro-biana, plasmidios R.    INTRODUCTIONSalmonella serovars other than those related to disease are being identified in clinically healthy swine by the time of slaughter (Costa et al. 1972, Zebral et al. 1974, Lázaro et al. 1997). This fact has implications on Public Health, in so far as a considerable number of such serovars are also isolated from outbreaks of human salmonellosis (Hofer & Reis 1994, Lirio et al. 1998).Its significance does not only lie on the attributes of virulence, but also on the capability of resistance to antimicrobials shown by some strains, as well as of the transfer of this feature through plasmids (Ishiguro et al. 1980, Simmons et al. 1988, Heffernan 1991).The quick and widespread drug-resistance mediated by plasmidial genes in Salmonella isolates has been reported worldwide. During the past few decades, various countries have witnessed a significant increase in human isolates of multiresistant salmonellae (Holmberg et al. 1984, Carvalho & Hofer 1989, Rivera et al. 1991, Asensi & Hofer 1994, Ling et al.1998), as well as animal isolates (Hampton et al. 1995, Millemann et al. 1995, Alaniz et al. 1997, Izumiya et al. 2001). Of particular interest is the fact that most plasmids acquire their resistance genes through transposons, whether from an other plasmid in the strain, from the chromosome or plasmids carried by other bacterial strains which are present in the host (Threlfall & Frost 1990). In the light of this, research was carried out which concentrated essentially on R factors of Salmonella, by means of conjugation tests (Timoney 1978, Vinhas & Almeida 1984, Simmons et al. 1988, Sant'Ana et al. 1995).In view of the complexity of the factors associated with the dissemination of resistant Salmonella strains, this paper has the purpose of assessing the capability to transfer marks of resistance to antimicrobials by means of bacterial conjugation as well as by analysis of the plasmidial profile of Salmonella isolated from clinically healthy swine, and also originating from the environment where these animals were slaughtered, in the state of Rio de Janeiro.   MATERIALS AND METHODSFor the conjugation experiments 7 samples were selected belonging to serovar Muenster; 4 samples of serovar Derby, one belonging to serovar Typhimurium , and one to serovar Braenderup. These were isolated from swine and the abattoir environment; they were resistant and/or multiresistant to sulphonamide (Su), streptomycin (Sm) and tetracycline (Tc) (Table 1).  Conjugation experiments. For the determination of R factors in the samples under study, the methodology used was the one described by Dias & Hofer (1985). Conjugation was performed using as recipient Escherichia coli K12 55, F- Lac+ Nalr, susceptible to all drugs except nalidix acid. Transconjugants were seleted on MacCon

【 授权许可】

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