Biofilm formation by Salmonella Enteritidis at different incubation temperatures

ABSTRACT

Background: The genus Salmonella, associated with poultry products, is considered the leading cause of foodborne outbreaks in humans in many countries. In Brazil, Salmonella Enteritidis (SE) is the serovar remains as one most frequentlyisolated from humans, and it is also a major serovar found in animals, food, animal feed, and environmental samples, despiteall the efforts to control this pathogen. Also, the bacterium is able to form biofilms on different surfaces, protecting cellsfrom both cleaning and sanitizing procedures in the food industries. This study aimed to verify the ability of SalmonellaEnteritidis isolates to form biofilm on polystyrene at different incubation temperatures.Materials, Methods & Results: A total of 171 SE samples were isolated from foodborne outbreaks (foods and stool cultures) and poultry products between 2003 and 2010. The biofilm-forming ability of samples was measured at four differenttemperatures (3°C, 9ºC, 25ºC, and 36ºC), for 24 h, simulating temperatures usually found in poultry slaughterhouses. Later,200 μL of each bacterial suspension was inoculated, in triplicate, onto 96-well, flat-bottomed sterile polystyrene microtiterplates, washed, after that, the biofilm was fixed with methanol. The plates were dried at ambient temperature, stained with2% Hucker’s crystal violet. Afterwards, absorbance was read using an ELISA plate reader and the optical density (OD)of each isolate was obtained by the arithmetic mean of the absorbance of three wells and this value was compared withthe mean absorbance of negative controls (ODnc). The following classification was used for the determination of biofilmformation no biofilm production, weak biofilm production, moderate biofilm production and strong biofilm production.Results demonstrated all isolates from stool cultures and foods involved in foodborne outbreaks, at least one of the fourtemperatures tested, were able to form biofilm...