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| Author(s): |
Meg da Silva Fernandes
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia de Alimentos |
| Defense date: | 2014-10-11 |
| Examining board members: |
Arnaldo Yoshiteru Kuaye;
Ernani Porto;
Maria Amelia de Jesus Piton;
Maristela da Silva do Nascimento;
Sérgio Bertelli Pflanzer Júnior
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| Advisor: | Dirce Yorika Kabuki; Arnaldo Yoshiteru Kuaye |
| Abstract | |
Enterococcus faecium and Enteroccus faecalis are opportunistic pathogens species that infect mainly immunocompromised individuals. These species are found in dairy products and are capable of forming biofilms on surfaces that contact with food. Their removal is highly dependent on the cleaning procedures. It is known that enterococci use the cell-cell communication (quorum sensing) to biofilm formation. The formation of mono- and multi-species biofilm, the effectiveness of sanitization procedures to control these biofilms and the production of signaling molecules of quorum sensing (AI-2) by strains of E. faecalis, E. faecium, Bacillus cereus and Listeria monocytogenes were evaluated in this work. The biofilms were grown on stainless steel coupons at various incubation temperatures (7, 25 and 39 °C) and times (0, 1, 2, 4, 6 and 8 days). After 1 and 8 days of contact at 25 and 39 °C, the coupons were subjected to different sanitation procedures: anionic tensioactive cleaning, acid-anionic tensioactive cleaning, sanitization, anionic tensioactive cleaning + sanitization, acidic- anionic tensioactive cleaning + sanitization and chlorinated alkaline cleaning. The sanitizers tested were: sodium hypochlorite (0.2%), peracetic acid (0.2%), quaternary ammonium (3%), and biguanide (1%). The detection of AI-2 molecules was performed by evaluating the luxS gene and biological bioluminescence assay. None of the microorganisms evaluated was able to form biofilms at 7 °C. Enterococcus sp. were able to form biofilms, with counts above 8 log CFU/cm2 for the temperatures of 25 and 39 °C after 8 days of contact. In multi-species culture, the temperature of 25 °C favored the development of L. monocytogenes biofilms (counts above 6 log CFU/cm2). On the other hand, at 39 °C it was observed a negative effect in the development of L. monocytogenes biofilms in mixed culture, with a significant reduction in counts over time (values below 0.4 log CFU/cm2). The counts of B. cereus, for both temperatures at different exposure times were below 4.1 log CFU/cm2. In contrast, the spore counts of B. cereus evolved over time, reaching scores of around 4.6 log CFU/cm2. The anionic tensioactive cleaning complemented by an aditional step (acid cleaning, acid cleaning + sanitization or sanitization) was able to remove mono- and multi-species biofilms in all tested conditions. The peracetic acid was the most effective sanitizer and the less efficient was biguanide. All strains of Enterococcus spp. and B. cereus showed the luxS gene and induced the phenomenon of bioluminescence in Vibrio harveyi BB170, indicating the presence of AI-2 autoinducers (AU) | |
| FAPESP's process: | 10/10507-7 - BIOFILM FORMATION, PATHOGENICITY AND QUORUM-SENSING IN STRAINS OF E. faecium AND E. faecalis ISOLATED IN PROCESSING OF RICOTTA. |
| Grantee: | Meg da Silva Fernandes |
| Support Opportunities: | Scholarships in Brazil - Doctorate |