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Influence of acid adaptation on the survival of Salmonella enteritidis and Salmonella typhimurium in simulated gastric fluid and in Rattus norvegicus intestine infection

Perez, Karla Joseane, Ceccon, Raquel Valim, Malheiros, Patricia da Silva, Jong, Erna Vogt, Tondo, Eduardo Cesar
Journal of food safety 2010 v.30 no.2 pp. 398-414
Rattus norvegicus, Salmonella enteritidis, Salmonella typhimurium, acid tolerance, adaptation, exposure, feces, gastric juice, humans, infection, intestines, mayonnaise, microorganisms, mortality, pH, rats, salmonellosis, serotypes, viability, vinegars, virulence, Brazil
The aim of this study was to investigate the influence of acid adaptation in the survival of Salmonella Enteritidis (SE86) and Salmonella Typhimurium (ST99) during exposure to simulated gastric fluid (SGF) and in intestinal infection of Rattus norvegicus. Acid-adapted and nonadapted Salmonella strains were exposed to SGF (pH 1.5) and were inoculated by gavage in adult rats. Results indicated that acid-adapted SE86 survived significantly better (P < 0.05) than nonadapted SE86, nonadapted ST99 and acid-adapted ST99 in SGF. Nonadapted microorganisms were observed in higher counts in feces than acid-adapted strains, while acid-adapted microorganisms demonstrated higher counts in intestine samples, suggesting intestinal invasion capacity. Acid-adapted SE86 was recovered in higher counts from ileum-cecum junction than the other microorganisms. Salmonella Enteritidis has been identified as the most frequent serovar involved with the foodborne outbreaks in Brazil. In Southern Brazil, a specific strain of Salmonella Enteritidis (SE86) has been involved with more than 90% of the salmonellosis occurring in the last years, and the main food vehicle is home-made mayonnaise frequently added with different quantities of vinegar, which can cause acid adaptation in Salmonella cells. The results of this work indicate that SE86 presented higher acid adaptation, which contributed to higher survival rates in simulated gastric fluid and better intestinal colonization. These results could be related to human virulence and the frequent involvement of this strain with foodborne outbreaks in southern Brazil.