Genotypes, exotoxin gene content and antimicrobial resistance in Staphylococcus aureus recovered from foods and food-handlers.
Source
Department of Functional Biology, Microbiology Area, University of Oviedo. Julian Clavería 6, 33006 Oviedo, Spain.
Abstract
Staphylococcal food poisoning, one of the most common food-borne diseases, results from ingestion of one or more staphylococcal enterotoxins (SEs) performed by Staphylococcus aureus in foods. In the present study, 64 S. aureusisolates recovered from foods and food handlers, associated or not with food-poisoning outbreaks in Spain, were investigated. They were assigned to 31 strains by spa typing, MLST, exotoxin gene content, and antimicrobial resistance. The strains belonged to ten clonal complexes (CCs): CC5 (29.0%), CC30 (25.8%), CC45 (16.1%), CC8, CC15 (two strains each), CC1, CC22, CC25, CC59, and CC121 (one each). They contained haemolysin genes (90.3%); lukED (77.4%); exfoliatin genes: eta, etd (6.5% each) and etb (3.2%); tst (25.8%); and enterotoxin or enterotoxin-like genes or clusters: sea (38.7%), seb (12.9%), sec (16.1%), sed-selj±ser (22.9%), selk-selq (6.5%), seh, sell, selp (9.7% each), egc1 (32.3%), and egc2 (48.4%). The number of se/sel genes ranged from 0 to 12. All isolates carrying tst, and most isolates with genes encoding classical enterotoxins (SEA, SEB, SEC and SED), expressed the corresponding toxin(s). Two CC5 isolates from hamburgers (t002/ST5, t2173/ST5) were methicillin resistant and harboured SCCmec IVd. Six (19.4%) were mupirocin resistant and one (t120/ST15) from a food handler carried mupA (MIC 1250 μg/ml). Resistances to ampicillin (blaZ; 61.3%), erythromycin (ermA-ermC/ermC; 25.8%), clindamycin (msrA-msrB/msrB; 16.1%), tetracycline (tetK; 3.2%), and amikacin-gentamicin-kanamycin-tobramycin (aacA+aphD-aphA; 6.5%) were also observed.
The presence of S. aureus with an important repertoire of virulence and resistance determinants in the food chain represents a potential health hazard for consumers and deserves further observation.
