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Enterotoxin gene profiles of S taphylococcus aureus isolated from milk and dairy products in I taly
Author(s) -
Bianchi D.M.,
Gallina S.,
Bellio A.,
Chiesa F.,
Civera T.,
Decastelli L.
Publication year - 2014
Publication title -
letters in applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.698
H-Index - 110
eISSN - 1472-765X
pISSN - 0266-8254
DOI - 10.1111/lam.12182
Subject(s) - staphylococcus aureus , enterotoxin , microbiology and biotechnology , micrococcaceae , biology , food science , gene , bacteria , genetics , escherichia coli
Staphylococcal foodborne intoxication, occurring after consumption of staphylococcal enterotoxins ( SE s) in food, is considered one of the most common forms of bacterial foodborne outbreaks worldwide. Milk and dairy products account for 5% of all the incriminated foods in staphylococcal outbreaks, referring to E urope. The distribution of genes encoding for enterotoxins in S taphylococcus aureus strains is highly variable, with some carried on stable regions of the chromosome and others carried on mobile genetic elements. The aim of this study was to analyse the distribution of genes encoding for SE s in Staph. aureus strains isolated from milk and dairy products. In the period from January 2010 to June 2011, a total of 1245 dairy samples (848 of raw milk and 397 of dairy products) were collected and analysed for detection of genes encoding for 11 SE s and SE l s ( SEA , SEB , SEC , SED , SEE , SEG , SEH , SEI , SER SE l J and SE l P) according to the procedures of the Italian National Reference Laboratory for coagulase‐positive Staphylococci including Staph. aureus . Staphylococcus aureus strains were isolated in 481 (39%) samples. Of the 481 isolates of Staph. aureus tested, 255 (53%) were positive for one or more SE genes, and thirty‐five different enterotoxin gene profiles were distinguished among the isolates. ser gene, found in 134 (28%) of the isolates, was the most frequent, followed by sed (25%) and selj genes (25%). The identification of new SE s increased the isolation frequency of enterotoxigenic staphylococci, thus suggesting that the pathogenic potential of Staph. aureus may be of greater importance than previously thought. Further studies are needed to quantify the expression of these new enterotoxins, and to assess their contribution to foodborne disease burden. Significance and Impact of the Study The analyses targeted 11 staphylococcal enterotoxins genes and 35 different enterotoxin gene profiles were distinguished among the isolates. A total of 255 Staph. aureus isolates were positive for one or more SE genes while ser gene was the most prevalent. In 93% of the isolates bearing genes located on the enterotoxin gene cluster ( n = 89), both seg and sei genes were present.