ABSTRACTStaphylococcal food poisoning, one of the most common food-borne diseases, results from ingestion of one or more staphylococcal enterotoxins (SEs) produced byStaphylococcus aureusin foods. In the present study, 64S. aureusisolates recovered from foods and food handlers, associated or not associated with food-poisoning outbreaks in Spain, were investigated. They were assigned to 31 strains byspatyping, multilocus sequence typing (MLST), exotoxin gene content, and antimicrobial resistance. The strains belonged to 10 clonal complexes (CCs): CC5 (29.0%), CC30 (25.8%), CC45 (16.1%), CC8, CC15 (two strains each), CC1, CC22, CC25, CC59, and CC121 (one strain each). They contained hemolysin genes (90.3%);lukED(77.4%); exfoliatin geneseta,etd(6.5% each), andetb(3.2%);tst(25.8%); and the following enterotoxin or enterotoxin-like genes or clusters:sea(38.7%),seb(12.9%),sec(16.1%),sed-seljwith or withoutser(22.9%),selk-selq(6.5%),seh,sell,selp(9.7% each),egc1(32.3%), andegc2(48.4%). The number ofseandselgenes ranged from zero to 12. All isolates carryingtst, and most isolates with genes encoding classical enterotoxins (SEA, SEB, SEC, and SED), expressed the corresponding toxin(s). Two CC5 isolates from hamburgers (spatype t002, sequence type 5 [ST5];spatype t2173, ST5) were methicillin resistant and harbored staphylococcal cassette chromosomemec(SCCmec) IVd. Six (19.4%) were mupirocin resistant, and one (spatype t120, ST15) from a food handler carriedmupA(MIC, 1,250 μg/ml). Resistance to ampicillin (blaZ) (61.3%), erythromycin (ermA-ermCorermC) (25.8%), clindamycin (msrA-msrB or msrB) (16.1%), tetracycline (tetK) (3.2%), and amikacin-gentamicin-kanamycin-tobramycin (aphAwithaacAplusaphDoraadD) (6.5%) was also observed. The presence ofS. aureusstrains with an important repertoire of virulence and resistance determinants in the food chain represents a potential health hazard for consumers and merits further observation.

IncA/C plasmids are responsible for multidrug resistance in an increasing number of relevant human and animal bacterial pathogens, and hence are regarded as an important threat to public health. Those found in the Spanish clone of Salmonella 4,5,12:i:- constitute a relevant example of short-term evolution, and could have been involved in the successful adaptation of this pathogen.

Salmonella enterica serovar Rissen is one of the most common serovars found in pigs and pork products in different countries, including Spain. However, information on the molecular bases of antimicrobial drug resistance and the population structure of Salmonella Rissen from different sources in Spain is limited. The present study focused on 84 isolates collected in Spain from pig and beef carcasses, foods and clinical samples associated with sporadic cases of gastroenteritis, and one outbreak. The majority of the isolates were resistant to tetracycline (73.8%), mainly conferred by tet(A). Resistances to streptomycin (aadA1-like, aadA2, and strAB), sulfonamides (sul1, sul2, and sul3), trimethoprim (dfrA1-like and dfrA12), ampicillin (blaTEM-1-like), and chloramphenicol (cmlA1-like) were also detected, with frequencies ranging from 12% to 20.2%. Most of the identified genes were carried by integrons, including three class 1 integrons of the sul1 type, a class 1 integron of the sul3 type, and the class 2 integron of Tn7. Two sul1 integrons, the sul3 integron, and the class 2 integron are first reported in Salmonella Rissen. Typing of the isolates with XbaI pulsed-field gel electrophoresis detected a major clone, which was circulating in humans and animals during the past decade, and was responsible for the outbreak. The obtained results are relevant for food safety and public health.

Complex genetic elements have apparently been responsible for the recruitment, assembly and dispersion of resistance genes among the highly diverse genomic types of S. Brandenburg, identified as causal agents of human salmonellosis in the Principality of Asturias, over recent years.

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