Comunicación presentada en ICAR2010. I International Conference on Antimicrobial Research

3 de noviembre de 2010

Palomo G., Campos MJ., Ugarte-Ruiz M., Castilla C., Borge C., Vadillo S., Piriz S. y Quesada A.

Salmonellosis is the most important food-borne disease in the North Hemisphere. Although S. Enteritidis (from poultry sources) is the main responsible for human infections, S. Typhimurium (from pork products) has been increasing his prevalence in recent years. The transmission of antimicrobial resistance microorganisms from livestock animals to humans is well known, but not all production systems are equally responsible. In the case of swine-farming in Spain, a sharp contrast there exists between white and Iberian pigs, being the later associated to more extensive breeding management and, presumably, to a lower exposure to antimicrobial treatments.

The collection of strains analyzed in this work includes multi-resistant salmonellas isolated from white swine (WS; n=39) or Iberian swine (IS; n=94) at slaughterhouses by animal infectious diseases units of two Veterinarian Faculties (University of Cordoba and University Complutense of Madrid). In order to realize comparative studies with bacteria isolated from humans, 303 salmonella strains were isolated at the six hospitals of the Extremadura Health System. Interestingly, the number of S. Typhimurium isolates from humans was slightly higher than that of S. Enteritidis (113 over 102). The analysis of clonal relationships by PFGE revealed that three pulsetypes were the most prevalent (n>10), which are: S. Enteritidis EN02 (n=71), S. Typhimurium TY09 (18 from human clinical cases and 12 from WS) and S. Typhimurium TY19 (12 human strains).

Minimum inhibitory concentrations (MIC`s) have been calculated for the 23 antimicrobial agents which monitoring has been recommended by the EFSA (European Food Safety Agency). Almost all S. Typhimurium strains presented multi-resistant phenotypes, with little or no differences between WS, IS or human isolates. Among the genetic elements that carry antimicrobial resistance genes and that are involved in their horizontal transference, class 1 integrons have a remarkably important role, and thus, the resistance genes contained in gene-cassettes associated to class 1 integrase genes (int1) were screened by PCR on the Salmonella strains. These genetic elements were particularly abundant among S. Typhimurium from animals, mostly from WS, which presented a 47% of positive strains, in contrast to human isolates, where only one fifth were positives. Among twelve different RFLP profiles in which gene-cassettes were classified, only two were shared among S. Typhimurium from WS, IS and humans. The first was found associated mainly to the S. Typhimurium TY09 clone (only one strain from IS), whilst the second was detected in six different serovars (Brandenburg, Bredeney, Hindmarsh, Anatum, Choleraesuis and Typhimurium), facts that evidences their mobilization by horizontal transference. Finally, the high prevalence of S. Typhimurium might indicate an increasingly importance of pork meat as source of salmonella infections. This work evidences the real risk for spreading the antimicrobial multi-resistance and call the attention on the importance of considering animal production and management programmes when food chain surveillance are implemented

	Servicio de Zoonosis de Transmisión Alimentaria y Resistencia a Antimicrobianos (ZTA). Centro de Vigilancia Sanitaria Veterinaria (VISAVET). Universidad Complutense (UCM).

Enlace a ICAR2010. I International Conference on Antimicrobial Research