Staphylococcus aureus is a known major cause of foodborne illnesses, and milk and dairy products are often contaminated by enterotoxigenic strains of this bacterium. A number of typing techniques are available to help trace the source and transmission rates of S. aureus from foods. Such techniques include restriction fragment length polymorphism analysis (RFLP), pulse-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Recently, multiple-locus variable-number tandem-repeat (MLVA) was developed as a new generation protocol to subtype food-borne pathogens. The aim of the paper was to evaluate, using MLVA, the genetic differences among S. aureus isolated from raw milk and dairy products of North Italy. The study employed a total of 101 S. aureus strains isolated from 19 different provinces in 7 regions (Emilia Romagna, Liguria, Lombardia, Piemonte, Veneto, Trentino Alto Adige and Valle d'Aosta). The strains were from different raw milk and dairy products, and came from different animal species (79 isolates from cow and 22 from goat) with no evident problems of mastitis. The MLVA profile (combination of the six primers spa, clfA, clfB, sdr, sspA and coa) of S. aureus isolates produced 4 to 7 bands, approximately between 100 and 1.200 bp. The genomic variability in the S. aureus strains was considerable; in fact MLVA analysis revealed a high number (91) of MLVA patterns obtained for the 101 isolates studied here. Cluster analysis showed that with a 30% similarity cut-off value, 5 major clusters and 27 strains do not fall into any cluster. MLVA polymorphism was found to be a useful technique to discriminate several genetic variants in the S. aureus isolates, but no correlation was observed between the clusters obtained and the strains isolated from the different regions. The present study is the first in Italy to use MLVA to study the polymorphism of S. aureus isolated from different dairy products.
Application of multiple-locus variable-number tandem-repeat analysis (MLVA) to type Staphylococcus aureus isolated from North Italian dairy products
Stefano Morandi;Milena Brasca;
2008
Abstract
Staphylococcus aureus is a known major cause of foodborne illnesses, and milk and dairy products are often contaminated by enterotoxigenic strains of this bacterium. A number of typing techniques are available to help trace the source and transmission rates of S. aureus from foods. Such techniques include restriction fragment length polymorphism analysis (RFLP), pulse-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Recently, multiple-locus variable-number tandem-repeat (MLVA) was developed as a new generation protocol to subtype food-borne pathogens. The aim of the paper was to evaluate, using MLVA, the genetic differences among S. aureus isolated from raw milk and dairy products of North Italy. The study employed a total of 101 S. aureus strains isolated from 19 different provinces in 7 regions (Emilia Romagna, Liguria, Lombardia, Piemonte, Veneto, Trentino Alto Adige and Valle d'Aosta). The strains were from different raw milk and dairy products, and came from different animal species (79 isolates from cow and 22 from goat) with no evident problems of mastitis. The MLVA profile (combination of the six primers spa, clfA, clfB, sdr, sspA and coa) of S. aureus isolates produced 4 to 7 bands, approximately between 100 and 1.200 bp. The genomic variability in the S. aureus strains was considerable; in fact MLVA analysis revealed a high number (91) of MLVA patterns obtained for the 101 isolates studied here. Cluster analysis showed that with a 30% similarity cut-off value, 5 major clusters and 27 strains do not fall into any cluster. MLVA polymorphism was found to be a useful technique to discriminate several genetic variants in the S. aureus isolates, but no correlation was observed between the clusters obtained and the strains isolated from the different regions. The present study is the first in Italy to use MLVA to study the polymorphism of S. aureus isolated from different dairy products.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
