Characterisation of Escherichia coli isolated from raw milk cheeses

Abstract

The aim of this work was: (i) to verify the level of Escherichia coli in Pannerone and Valtrompia Formaggella, two artisanal Italian raw-milk cheeses ripened for less than 60 days; (ii) to phenotypically and genotipycally type the E. coli isolates; (iii) to detect the presence of E. coli O157:H7 and of intestinal enteropathogenic E. coli by PCR. The levels of E. coli in the cheeses ranged from 3.89 to 8.47 log CPU g-1. No E. coli O157:H7 was detected in 25 g of cheese. The 76 E. coli strains (68 cheese isolates and 8 reference strains) were widely diverse, since a high number of both PCR fingerprinting profiles and Phenetplate™ phenotypes were shown. Within the 68 cheese isolates, no toxin production and virulence-associated genes were shown by multiplex PCR. Non-pathogenic E. coli were isolated at high levels in raw-milk cheeses, where they may contribute to the development of desirable characteristics of some of these products, e.g. Pannerone.