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• Food-producing animals (lamb, veal and goat) are analysed for staphylococci nasal carriage. • S. aureus is detected in 29.7% of lamb, 12.5% of goat and 2.7% of veal animals tested. • MRSA of USA300 clone (ST8-PVL-positive) was detected in lamb and goat. • MSSA of lineages ST133 and ST522 carrying the virulence gene tst was found in lamb. • CoNS with relevant antibiotic resistance genes were detected in 28% of tested animals. This work aimed to determine the prevalence, diversity, antibiotic-resistance phenotype/genotype and virulence factors in staphylococci of farm-animals. Nasal samples of 117 farm-animals (calve: 72; lamb: 37; goat: 8) were collected from one slaughterhouse in La Rioja/Spain and cultured for staphylococci and methicillin-resistant Staphylococcus (MRS) recovery. Identification was performed by MALDI-TOF. Antimicrobial resistance phenotype/genotype was determined by susceptibility testing and specific PCRs. Molecular typing (spa -typing, multilocus-sequence-typing, agr -typing, SCC mec), and detection of 12 virulence genes and human Immune-evasive-cluster (IEC) genes were performed by PCR/sequencing in S. aureus. Two marker genes of arginine catabolic mobile element (ACME) were determined by PCR (USA300-MRSA detection). Staphylococci were identified in 50%, 54% and 21% of goat, lamb and calve samples, respectively. Among the 13 S. aureus isolates recovered, 11 were susceptible to all antimicrobials tested, and two were multidrug-resistant-MRSA [beta-lactams (blaZ , mecA), macrolides [(msr (A)/ msr (B)] and fluoroquinolones]. The MSSA harboured either tst or enterotoxin genes, while the MRSA harboured the lukF/lukS-PV genes. Five sequence-types were detected. The two MRSA strains (from lamb and goat) were typed as t5173/ST8/ agr -I/SCC mec -IVa/ACME-positive, corresponding to USA300 clone, and were IEC-B-positive. Among the 47 coagulase-negative staphylococci (CoNS), six species were identified, predominating S. simulans (n = 25) and S. sciuri (n = 11). Fifty-three percent of CoNS showed resistance to at least one antimicrobial agent (six multidrug-resistant strains), and the following resistance phenotypes/genotypes were detected: streptomycin [27.6%; ant(6)-Ia, str ], tetracycline [23.4%; tet (M), tet (L), tet (K)], clindamycin [19.1%; lnu (A), vgaA ], erythromycin [10.6%; erm (C), msr (A)/ msr (B)], chloramphenicol (8.5%; fexA), tobramycin (6.4%), penicillin-cefoxitin (4.3%; blaZ , mecA), and SXT (2.1%). The detection of the MRSA-USA300 lineage in food animals is worrisome and should be further monitored. [ABSTRACT FROM AUTHOR]

Methicillin-resistant Staphylococcus aureus (MRSA) CC398 is a livestock-associated (LA) lineage, mainly detected in swine. Its dissemination via the food-chain could be a food-safety issue. This work aimed to study the diversity of S. aureus lineages in pork-products, to determine the prevalence of MRSA and methicillin-susceptible S. aureus (MSSA) of lineage CC398, and to study the antimicrobial resistance phenotype/genotype and the virulence traits of recovered isolates. One hundred and one samples of pig-derived food were collected in Northern Spain for S. aureus isolation. Antibiotic resistance profile was analysed, and associated resistance genes were screened by PCR. Detection of CC398 lineage, spa -type, multilocus sequence-type, virulence factors, immune evasion cluster (IEC) genes, and phage ΦSa3 integrase was performed by PCR/sequencing. The prevalence of S. aureus and MRSA among pig-derived food was 33.6% and 21.8%, respectively. Thirty-nine S. aureus isolates were recovered and attributed to 19 spa -types and 12 STs, ST398 being the predominant lineage (n = 25; 64%). MRSA-CC398 isolates (n = 23) were mainly spa -t011 (n = 16) and 82.6% were multidrug-resistant (MDR). All MRSA-CC398 were tetracycline-resistant and IEC-negative and four hosted either eta , tst or sea gene. The two MSSA-CC398 isolates detected were spa -t5452, IEC-positive, and were resistant to penicillin (blaZ) and erythromycin/clindamycin (inducible) (ermT with/without ermC + msrA). Among the 14 non-CC398 isolates, only two were MRSA (ST8, PVL-positive, enterotoxin-positive, IEC-negative). The 12 MSSA isolates included two of lineage CC45 and IEC-positive. CC398 lineage is prevalent among S. aureus of pig-derived food (both MRSA and MSSA), LA-MRSA-CC398/t011 being the clone most represented. The presence of the IEC-positive MSSA-CC398 and MSSA-CC45 isolates in food products highlights the potential implication of handlers in transmission of foodborne pathogens. Moreover, given the high frequency of MDR isolates and virulence genes detected, hygienic practices should be improved to limit the dissemination risk of S. aureus via the food chain. • S. aureus and MRSA were detected in 33.6% and 21.8% of pig-derived food samples. • LA-MRSA CC398 (mostly spa -t011) found in 23% of pig-derived food, all MDR • S. aureus non-CC398 found in 16% of samples, with detection of toxigenic strains. • Human-adapted clones (MSSA-CC398, MSSA-CC45) detected, suggesting human contamination • Pig-derived food carry MDR and toxigenic S. aureus , of public health relevance. [ABSTRACT FROM AUTHOR]