Antibiotic-resistant strains of Enterococcus isolated from Swedish and Danish retailed chicken and pork

Two hundred and seventy-seven Enterococcus isolates representing the predominating enterococcal flora of retailed chicken and pork were identified by phenotypical features, and by random amplified polymorphic DNA. The resistance to nine different antibiotics was determined. Enterococcus faecium was the most frequently occurring species in both Swedish and Danish chicken. Enterococcus faecalis and unidentified groups of Enterococcus dominated in pork. Seventy-three per cent of the Enterococcus isolates from Swedish chicken were resistant to one or more of the tested antibiotics. The corresponding values for Swedish pork, Danish chicken and Danish pork were 9%, 55% and 14%, respectively. Tetracycline resistance was most frequent in isolates from Danish pork and Swedish chicken, while erythromycin resistance was most frequent in Danish chicken. Strains with acquired vancomycin resistance, mainly Ent. faecium, were found only on Danish chicken, except for one isolate from Danish pork. All vancomycin-resistant isolates contained the vanA gene. Vancomycin resistance could be transferred to a vancomycin-sensitive Ent. faecium strain from four of nine tested donor strains.