CARACTERIZAÇÃO E CONTROLO DE BIOFILMES DE L. MONOCYTOGENES E CAMPYLOBACTER SPP. EM ESTABELECIMENTOS DE PRODUÇÃO DE ALIMENTOS PRONTOS A CONSUMIR

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Listeria monocytogenes in the ready-to-eat meat-based food chain : characterization and preventive control measures assessment

Publication . Henriques, Ana Rita Barroso Cunha de Sá; Fraqueza, Maria João dos Ramos

In some studies, ready-to-eat meat-based food products (RTEMP) are considered the food vehicle with the highest risk of being contaminated with Listeria monocytogenes. One of the aims of this work was to assess L. monocytogenes presence in Portuguese ready-to-eat meat processing industries and retail establishments. Environment and final product samples were analyzed and an audit was performed in ten industrial facilities to determine the level of implementation of good hygiene and manufacturing practices. To identify likely sources of final products contamination, as well as to assess virulence-associated traits, phenotypic and genotypic characterization of L. monocytogenes isolates was performed. Selected isolates were also characterized for their biofilm-forming ability and subsequently tested for their biocide susceptibility using benzalkonium chloride, sodium hypochlorite and nisin. Finally, the genetic relation of L. monocytogenes strains isolated from RTEMP (at industrial and retail level) and from human listeriosis cases was assessed. L. monocytogenes frequency was high in industrial RTEMP and its occurrence was linked to high scored industries in the hygienic audit, being specifically related to inadequate hygiene and manufacturing practices. L. monocytogenes isolates were genetically diverse and serogroups IIa, IIb and IVb were frequent among them. The isolates also displayed a similar profile of major virulence-associated genes profile and a low level of antibiotic resistance. Most of the selected L. monocytogenes strains demonstrated to be moderate and strong biofilm-formers, particularly those from serogroups IIc and IVb. When treated with benzalkonium chloride and sodium hypochlorite, most of the strains in biofilm exhibited a reduction in cell counts, however it was not possible to determine the minimal bactericidal concentration within the tested range for nisin. Three resistant strains to commercially recommended concentrations for benzalkonium chloride and sodium hypochlorite were identified. Some particular RTEMP strains presented high similarity with clinical strains, suggesting their potential for human infection. Overall, the findings in this work provide valuable information on L. monocytogenes in RTEMP and RTEMP-related environments, also highlighting RTEMP as potential vehicles for human listeriosis.

2016-11-14Tese de doutoramento

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Fundação para a Ciência e a Tecnologia

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SFRH/BD/70711/2010