FormaÃÃo de biofilme em aÃo inoxidÃvel por Aeromonas hydrophila e Staphylococcus aureus sob diferentes condiÃÃes de cultivo / Biofilm formation by Aeromonas hydrophila and Staphylococcus aureus on stainless steel AISI 304 in different conditions of cultivation

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

The microbial biofilm formation in surfaces used in food processing, like stainless steel, has been the focus in several researches in function of the injuries of its occurrence. These communities can act as constant point of contamination and cause other losses, as surface corrosion. In this context, Staphylococcus aureus and Aeromonas hydrophila are considered due these potential capacities to attach and form biofilm. The relevance of these species is associated to public health concerns and food deterioration. Based on the exposit, the aim of this research was to verify the capability of biofilm formation of Staphylococcus aureus and Aeromonas hydrophila in mono and multi-specie cultivation, using stainless steel AISI 304 as substrate and skim milk as aqueous phase, in three temperatures: 4, 7 and 18ÂC. To monocultivation investigation were inoculated, approximately, 108 CFU/mL of BHI of each microorganism in 1000 mL of milk, in separated Becker, with a final population density of 105 CFU/mL. Inoculation only occurred in the initial time. Each Becker, containing 1000 mL of milk, one sterilized magnetic bar, ten 10x20 mm sterilized chips of stainless steel AISI 304 was incubated, under 60 rpm of agitation, for 10 days at 4, 7 e 18ÂC, respectively. At each 48 hours 2 chips were collected and milk, Becker, and magnetic bar were substituted. Enumeration of sessile cells of S. aureus and A. hydrophila was conducted by plating in Baird-Parker agar and m-Aeromonas selective agar, added of ampicilin, respectively. Multi specie cultivation investigations were conducted as described above, with the difference of both microorganisms had been inoculated in the same Becker. Complementary studies included the generation time, enumeration of planktonic cells and visualization of chips by scanning electron microscopy. Treatments were set in a completely randomized split-plot design, with time in plot. Data were analyzed by statistic software SASÂ (SAS Institute, 2007). S. aureus, in mono-cultivation, formed biofilm at 18ÂC in 48 hours and at 7 in four days. At 4ÂC only was observed attachment in stainless steel. In multi-specie cultivation with A. hydrophila, the performance of S. aureus was inferior. In this condition S.aureus only formed biofilm at 18ÂC, two log units less tan mono-specie cultivation. A. hydrophila formed biofilm in all conditions. With the exception of 4ÂC, in all temperatures the biofilm was formed in 48 hours. To 4ÂC it formed in 4 days. At 18ÂC, the presence of S. aureus reduced the number of sessile cells in two log units after 6 days, when compared with mono-specie cultivation performance of A. hydrophila.

ASSUNTO(S)

microbiologia de alimentos aÃo inoxidÃvel aeromonas hydrophila biofilm aeromonas hydrophila staphylococcus aureus biofilme stainless steel staphylococcus aureus

ACESSO AO ARTIGO

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