Arcobacter butzleri in sheep ricotta cheese at retail and related sources of contamination at the industrial dairy plant

This study aimed to evaluate Arcobacter species contamination of industrial sheep ricotta cheese purchased at retail and to establish
if the dairy plant environment may represent a source of contamination. A total of 32 sheep ricotta cheeses (1.5 kg/pack)
packed in a modified atmosphere were purchased at retail, and 30 samples were collected in two sampling sessions performed in
the cheese factory from surfaces in contact with food and from surfaces not in contact with food. Seven out of 32 samples
(21.9%) of ricotta cheese collected at retail tested positive for Arcobacter butzleri at cultural examination; all positive samples
were collected during the same sampling and belonged to the same batch. Ten surface samples (33.3%) collected in the dairy
plant were positive for A. butzleri. Cluster analysis identified 32 pulsed-field gel electrophoresis (PFGE) patterns. The same
PFGE pattern was isolated from more than one ricotta cheese sample, indicating a common source of contamination, while more
PFGE patterns could be isolated in single samples, indicating different sources of contamination. The results of the environmental
sampling showed that A. butzleri may be commonly isolated from the dairy processing plant investigated and may survive
over time, as confirmed by the isolation of the same PFGE pattern in different industrial plant surface samples. Floor contamination
may represent a source of A. butzleri spread to different areas of the dairy plant, as demonstrated by isolation of the same
PFGE pattern in different production areas. Isolation of the same PFGE pattern from surface samples in the dairy plant and from
ricotta cheese purchased at retail showed that plant surfaces may represent a source of A. butzleri postprocessing contamination
in cheeses produced in industrial dairy plants.