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Virulence factors and genetic variability of Staphylococcus aureus strains isolated from raw sheep's milk cheese

Spanu, Vincenzo and Spanu, Carlo and Virdis, Salvatore and Cossu, Francesca and Scarano, Christian and De Santis, Enrico Pietro Luigi (2012) Virulence factors and genetic variability of Staphylococcus aureus strains isolated from raw sheep's milk cheese. International Journal of Food Microbiology, Vol. 153 (1-2), p. 53-57. eISSN 1879-3460. Article.

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DOI: 10.1016/j.ijfoodmicro.2011.10.015

Abstract

Contamination of dairy products with Staphylococcus aureus can be of animal or human origin. The host pathogen relationship is an important factor determining genetic polymorphism of the strains and their potential virulence. The aim of the present study was to carry out an extensive characterization of virulence factors and to study the genetic variability of S. aureus strains isolated from raw ewe's milk cheese. A total of 100 S. aureus strains isolated from cheese samples produced in 10 artisan cheese factories were analyzed for the presence of enterotoxins (sea-see) and enterotoxins-like genes (seh, sek, sel, sem, seo, sep), leukocidins, exfoliatins, haemolysins, toxic shock syndrome toxin 1 (TSST-1) and the accessory gene regulator alleles (agr). Strains were also typed using pulsed-field gel electrophoresis (PFGE). AMOVA analysis carried out on PFGE and PCR data showed that the major component explaining genetic distance between strains was the dairy of origin. Of the total isolates 81% had a pathogenicity profile ascribable to “animal” biovar while 16% could be related to “human” biovar. The biovar allowed to estimate the most likely origin of the contamination. Minimum inhibitory concentrations (MICs) of nine antimicrobial agents and the presence of the corresponding genes coding for antibiotic resistance was also investigated. 18 strains carrying blaZ gene showed resistance to ampicillin and penicillin and 6 strains carrying tetM gene were resistant to tetracycline. The presence of mecA gene and methicillin resistance, typical of strains of human origin, was never detected. The results obtained in the present study confirm that S. aureus contamination in artisan cheese production is mainly of animal origin.

Item Type:Article
ID Code:7363
Status:Published
Refereed:Yes
Uncontrolled Keywords:Staphylococcus aureus, cheeses, virulence factors, antibiotic resistance, molecular variance
Subjects:Area 07 - Scienze agrarie e veterinarie > VET/04 Ispezione degli alimenti di origine animale
Divisions:001 Università di Sassari > 01-a Nuovi Dipartimenti dal 2012 > Medicina Veterinaria
Publisher:Elsevier
eISSN:1879-3460
Deposited On:12 Apr 2012 09:59

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