Comparison of enterococcal populations in animals, humans, and the environment--a European study.

The objectives of the present study were to generate knowledge of enterococcal populations in the food chain, by studying the population structure (in measures of abundance and diversity) among enterococci in different geographical regions and in different parts of the food chain, as well as the similarities between different enterococcal populations. Altogether, 2868 samples were collected from humans (healthy and hospitalised individuals and clinical isolates), animals (slaughterhouse carcasses and farm animals), and the environment (pig farms, sewage, and surface water) in four European countries—Sweden, Denmark, UK, and Spain. The samples were characterised with regard to presence and numbers of enterococci, and eight (for faecal samples) or 24 (for environmental samples) isolates per sample were phenotyped and preliminarily identified with the PhP-RF system. In total, more than 20,000 isolates were typed. A majority of the samples (77%) showed the presence of presumed enterococci. The diversities of enterococci in environmental samples were generally high, and also faecal samples normally showed presence of more than one enterococcal strain. The most common species found were Enterococcus faecium (33%), E. faecalis (29%), and E. hirae (24%), but different enterococcal populations differed in their species distribution. Clinical isolates, hospitalised patients, and hospital sewage in Sweden showed a clear dominance of E. faecalis (80%, 57%, and 54%, respectively) whereas healthy individuals and urban sewage contained less E. faecalis (39% and 40%, respectively). The species distribution among isolates from slaughterhouses varied between animal species and also between countries, but E. faecalis seemed to be mainly associated with broiler, and E. hirae with cattle and pigs.