Salmonella and Salmonellosis in Southern Brazil: A Review of the Last Decade (pp. 175-191)
Authors: (E.C. Tondo, A.C. Ritter, Food Science and Technology Institute, Federal University of Rio Grande do Sul, ICTA/UFRGS, Brazil)
Abstract: Salmonella was identified as the first cause of food-borne diseases in the last decade in Brazil. Currently, Brazil is an important producer of pork and is the major poultry and beef exporter in the world. Brazilian animal products have been recognized worldwide, and to attend international standards the Brazilian food industries have been putting considerable effort in order to prevent food contamination, especially by Salmonella. A representative part of the Brazilian eggs, beef, poultry, and pork meats is produced in the State of Rio Grande do Sul (RS), in southern Brazil, where Salmonella was pointed out as the first cause of food-borne diseases for almost two decades. In this region, homemade mayonnaise was identified as the food preparation mostly involved with salmonellosis, and both meat and meat products were also identified as frequent vehicles for salmonellosis. A specific strain of Salmonella Enteritidis (named SE86) was identified as the responsible agent in more than 95 % of investigated food-borne diseases throughout the last decade. SE86 strains isolated from several outbreaks demonstrated the same DNA banding patterns when typed by PCR-methods and PFGE, suggesting that it is spread out through RS. SE86 demonstrated high percentages of sensitivity to many antibiotics; however, an increasing resistance to nalidixic acid and ampicillin has been identified. After exposure to sub-letal pHs, SE86 demonstrated a greater acid adaptation and also to be more acid-and-thermal-resistant than S. Typhimurium and S. Bredeney also isolated in RS State. Acid-adapted SE86 presents higher virulence than non-acid-adapted SE86 and acid-adapted S. Typhimurium in germ-free mice. This strain has shown to be able to form biofilms on stainless steel and polypropylene, and was more resistant to 200 and 400 ppm sodium hypochlorite than others Salmonella serovars, but was not more resistant than other S. Enteritidis isolated in countries such as Albania, Morocco, Pakistan and Zimbabwe. SE86 mutants (dps, rpoS) were constructed in order to investigate the involvement of these genes with oxidative stress caused by sodium hypochlorite exposure. The results demonstrated that both genes are expressed during such exposure;
however, dps was expressed in much higher amounts, increasing survival rates of SE86. Poultry meat produced in RS State demonstrated Salmonella prevalence of 4.4 % to 15 %, whilst expressively higher percentages of Salmonella were found in pork meat samples. Strains isolated from poultry and pork belonged to diverse serovars and, in general, demonstrated different patterns and higher antimicrobial resistance than SE86 isolated from salmonellosis.
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