Dissemination of antibiotic multi-resistant Salmonella isolates in Portuguese piggeries

Abstract number: 1733_12

Antunes P., Pestana N., Réu C., Peixe L.

Objectives: To study susceptibility to different antibiotics and to characterise the genetic determinants of antimicrobial resistance in Salmonella isolated from Portuguese piggery in order to assess the contribution of this type of animal exploration to the burden of mobile resistance genes and multidrug resistant clones previously observed in human and food products.

Methods: Dry faeces samples collected in 2006 from 2 pig farms in the Center and South of Portugal were positive for the presence of Salmonella (reference method ISO 6579:2002). Antibiotic susceptibility was study by disk diffusion method (CLSI) to 10 antimicrobial agents. Different antibiotic resistant phenotypes were selected for further studies. Detection and characterisation of class 1 integrons was performed by PCR, RFLP (TaqI) and sequencing. Resistance genes were searched by PCR. Conjugation assays and clonality analysis (PFGE-XbaI) were performed.

Results: All the Salmonella isolates recovered were resistant to one (tetracycline) or more antimicrobial agents (streptomycin, gentamicin, ampicillin, nalidixic acid, chloramphenicol, tetracycline, sulfonamides or trimethoprim). Characterisation of class 1 integrons revealed the presence of an array of gene cassettes (dfrA12, aadA) in isolates of S. typhimurium which also carried sul1, sul2 and sul3 genes and in isolates of S. Rissen, carrying sul1. The isolates of both serotypes were clonally related to strains previously observed in human and foodborne isolates widely disseminated in Portugal. Interestingly, MDR isolates of the S. Rissen clone were recovered from both piggeries studied. Other resistance genes (blaTEM, aac(3)-IV, tetA) were identified in the MDR isolates, but not integrated as gene cassettes.

Conclusion: Piggeries are in our country a source of MDR Salmonella isolates. Intensive use of several antimicrobial agents in this type of animal production seems to contribute to the selection of widely disseminated MDR clones.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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