Characterisation of Listeria monocytogenes isolates from poultry by serotyping and phage typing

With the aim of improving the knowledge of Listeria monocytogenes types distributed in poultry, isolates collected from a hundred eviscerated and refrigerated chicken carcasses from four different slaughterhouse plants in northwest Spain were characterised by serotyping and phage typing. Forty-two phage patterns were observed. Flight phage patterns (43, 43/387, 43/387/4477/1652 and 43/19/387/575 for strains of serogroup 1/2 and 107, 108/107/47, 2389 and 2389/3274 for strains of serogroup 4) were the most common. Thus, thirty strains (56.60% of phage typeable strains) showed the above-mentioned or indistinguishable (less than or equal to1 major phage reaction differences for serogroup 1/2 strains or less than or equal to2 major differences for serogroup 4) patterns. A wide distribution of some L. monocytogenes phage types was observed because different chicken carcasses (including carcasses from different slaughterhouses) were contaminated with the same or indistinguishable L. monocytogenes phage types. Besides, more than one type (serogroup or phage type) of L. monocytogenes was detected in 43.75% of positive samples. This finding emphasised the usefulness of subtyping several Listeria monocytogenes isolates from the same food sample in epidemiological studies.