Biodiversity and characterization of indigenous coagulase-negative staphylococci isolated from raw milk and cheese of North Italy

• Published in: Food microbiology 2013-05, Vol.34 (1), p.106-111
• Main Authors: Ruaro, Angela, Andrighetto, Christian, Torriani, Sandra, Lombardi, Angiolella
• Format: Article
• Language: English
• Subjects: Animals; Antibiotic resistance; antimicrobial properties; Bacterial Proteins - analysis; Bacterial Proteins - metabolism; Biodiversity; Biological and medical sciences; Cattle; Cheese; Cheese - microbiology; cheese milk; cheeses; Coagulase - analysis; Coagulase - metabolism; Coagulase-negative staphylococci; Food Contamination - analysis; Food industries; Food microbiology; Fundamental and applied biological sciences. Psychology; genes; Goats; hemolysis; histidine decarboxylase; Italy; Milk; Milk - microbiology; Milk and cheese industries. Ice creams; Phylogeny; polymerase chain reaction; proteolysis; raw milk; Safety aspects; Sheep; Staphylococcus - classification; Staphylococcus - genetics; Staphylococcus - isolation & purification; Staphylococcus - metabolism; Staphylococcus aureus; Staphylococcus equorum; Staphylococcus lentus; Staphylococcus sciuri; Staphylococcus simulans; Staphylococcus xylosus; Technological properties; tyrosine decarboxylase
• ISSN: 0740-0020; 1095-9998
• DOI: 10.1016/j.fm.2012.11.013

The aim of the current study was to detect coagulase-negative staphylococci (CNS) in raw milk and cheeses produced in North Italy, and to analyze isolates for their biodiversity, safety aspects and technological properties. Molecular identification methods revealed a high biodiversity among isolates and assigned them to 17 species. The most recovered species were Staphylococcus equorum (12%), Staphylococcus lentus (12%), Staphylococcus simulans (12%), Staphylococcus sciuri (10%), and Staphylococcus xylosus (9%). The presence of ten transferable antibiotic resistance (AR) genes was verified by PCR and 19% of isolates were positive, with tet(K) being the most frequent gene (10%); interestingly, no strain carried multiple AR genes. Twenty-four isolates displayed hemolytic activity; tyrosine decarboxylase gene (tdcA) was found in two isolates, while histidine decarboxylase gene (hdcA) and enterotoxin genes (se) were not detected. Isolates were further characterized for the presence of some relevant technological properties; 16% of isolates displayed proteolytic activity and 39% lipolytic activity, while no one of the isolates was found to exhibit antimicrobial activity against Staphylococcus aureus. This study provided evidence of a low occurrence of safety hazards in CNS isolated from dairy products. ► The biodiversity of 77 CNS isolated from raw milk and cheese was investigated. ► Isolates were evaluated for safety aspects and relevant technological properties. ► Except for hemolysis, CNS showed a low incidence of potential pathogenicity traits. ► Multiple antibiotic resistance genes were not detected. ► Results suggest to investigate the use of CNS as adjunct cultures in cheesemaking.