Publication Database

Investigation of Vibrio and ESBL/AmpC-producing Enterobacteriaceae in retail seafood and inactivation of Vibrio in pure culture and mussel homogenates using high hydrostatic pressure (2018)

Art

Hochschulschrift

Autor

Vu, Thi Thu Tra (WE 8)

Quelle

Berlin, 2018 — viii, 96 Seiten

Verweise

URL (Volltext): https://refubium.fu-berlin.de/handle/fub188/23797

Kontakt

Institut für Lebensmittelsicherheit und -hygiene

Königsweg 69
14163 Berlin
+49 30 838 62551 / 52790
lebensmittelhygiene@vetmed.fu-berlin.de / fleischhygiene@vetmed.fu-berlin.de

Abstract / Zusammenfassung

Seafood is considered as an important food source which contains high nutritional values via e.g. proteins, vitamins and minerals. Therefore, seafood production and consumption has increased worldwide in recent decades. Despite the nutrient benefits, consumption of seafood containing human pathogens might pose a potential risk of foodborne illness. Pathogenic bacteria, viruses, parasites, chemicals, heavy metals and natural toxins have been found in seafood. Among different bacterial pathogens detectable in seafood, Vibrio spp. are the most commonly associated with human infections. Another public health hazard related to seafood is the rapid increase of antimicrobial resistance among zoonotic pathogens in aquatic population. The spread of antimicrobial resistant bacteria, especially ESBL/AmpC-producing Enterobacteriaceae to human through the food chain has been reported and become a major concern of public health because of increasing in the number and severity of infections, as well as the frequency of treatment failure. In this thesis, three studies were conducted with the objectives (i) to determine the prevalence of Vibrio spp., (ii) to determine the prevalence, to investigate the quantitative load, and to characterize ESBL/AmpC-producing Enterobacteriaceae in retail seafood in Berlin, Germany, and (iii) to investigate the effect of HHP on the inactivation of Vibrio spp. in pure culture as well as mussel homogenates. The seafood investigation results demonstrate a high prevalence of Vibrio spp. in retail seafood with 55% (95% CI: 47.2% - 62.8%), and positive samples were detected in all types of seafood investigated. V. alginolyticus was the most prevalent species (35.6%), followed by V. parahaemolyticus (27.5%), V. cholerae (6.3%) and V. vulnificus (0.6%). The storage conditions seemed to influence the prevalence of Vibrio spp. Among chilled samples, the prevalence of Vibrio spp. in unpacked samples was significantly higher than in packed samples (P = 0.006). Whereas, among packed samples, no significant difference in the prevalence of Vibrio spp. between chilled or frozen conditions was observed (P = 1). None of the V. cholerae and V. parahaemolyticus isolates carried virulence genes. However, this should not be neglected because of previous findings on pathogenic strains lacking these virulence markers. In parallel with detection of Vibrio spp., the presence of ESBL/AmpC-producing Enterobacteriaceae in retail seafood was also investigated. The obtained data reveal that ESBL/AmpC-producing Enterobacteriaceae were detected in 21.3% of seafood samples (95% CI: 14.8% - 27.7%). Of the positive samples, 91.2% contained an ESBL/AmpC-producing Enterobacteriaceae load of < 100 CFU/g (lower detection limit), whereas 8.8% contained counts of 100 to 1,000 CFU/g. K. pneumoniae and E. coli were the two predominant species among the 45 isolates. β-lactamase genes were detected in 39 isolates, of which 33 isolates carried ESBL/AmpC β-lactamase genes with the majority of isolates harbouring blaCTX-M (27.3%), blaCMY (21.2%) and blaDHA (21.2%) genes. The obtained results from HHP experiment indicate the efficacy of HHP inactivating Vibrio spp. in both pure culture and mussel homogenates. Significant increases in reductions of Vibrio spp. were observed when pressure levels increased in combination with longer processing times. The reduction levels were significant different among the respective Vibrio spp., and V. vulnificus was the most susceptible species to HHP. To achieve a > 5-log reduction in mussel homogenates, treatment at 350-450 MPa for ≥ 1 min at 25ºC for V. alginolyticus, V. cholerae and V. vulnificus, or 250 MPa for ≥ 3 min for V. vulnificus are required, while pressure levels of 350 MPa for ≥ 3 min or 450 MPa for ≥ 1 min should be applied for V. parahaemolyticus. Our research highlights the hazard potential of seafood containing both Vibrio spp. and ESBL/AmpC-producing Enterobacteriaceae in Germany. Further investigations along the seafood chain should be carried out to clarify the contamination route of Vibrio spp. and ESBL/AmpC-producing Enterobacteriaceae as well as the transmission of resistance genes among these bacteria. Additionally, application of effective post-harvesting methods like HHP is recommended to reduce the contamination level of Vibrio spp. in seafood and finally to ensure the food safety for human consumption.