Methicillin-resistant Staphylococcus aureus (MRSA) strains belonging to sequence type (ST) 398 are being reported with increasing frequency in Europe and other countries. This MRSA type has been isolated from colonized and infected animals and humans. The aim of this study was to determine the prevalence of nasal MRSA carriage in pigs and pig workers. A total of 300 pigs from 15 different farms were sampled in the slaughterhouse of Tenerife. A total of 54 pig workers were screened for MRSA: 20 belonged to farms whose pigs had been sampled and 34 to the slaughterhouse. The percentage of positive samples of MRSA in pigs was 85.7%. The overall prevalence of nasal MRSA carriage in pig workers was 9.3%. All MRSA isolates from pigs and humans belonged to one clonal group showing multilocus sequence type (MLST) 398. Two types of Staphylococcal Chromosome Cassette (SCCmec) were found, IV and V. In conclusion, the prevalence of MRSA in nasal samples from pigs and pig workers in Tenerife was high. We therefore consider it essential to deepen epidemiological study of this strain of animal origin, as well as to increase surveillance and control measures at all stages of the food chain.

The problem of emerging resistant microorganisms such as Methicillin-Resistant Staphylococcus aureus (MRSA) associated to livestock is closely linked to improper use of antimicrobial agents. The aim of this study is to find out the prevalence and characteristics of these strains, as well as their evolution in healthy pigs on the Island of Tenerife, Spain. Between October 2009 and December 2010, 300 pigs from 15 wean-to-finishing farms were screened. Between 1 September 2017 and 31 March 2018, a new sampling was performed collecting 125 nasal swabs from pigs belonging to the same farms and under the same conditions as the previous study. MRSA antibiotic resistant patterns were studied. Results: Prevalence of MRSA isolates was 89.6%. All isolates belonged to Sequence Type 398 (ST398), a livestock related strain. All strains studied were resistant to beta-lactamic non-carbapenemic antibiotics and sensitive to teicoplanin, linezolid, vancomycin, rifampicin, quinupristin-dalfospristin, and mupirocine. Between 2009/2010–2017/2018 a significant increase in resistance to gentamicin, tobramycin, trimethoprim-sulfomethoxazole, clindamycin, Fosfomycin, and tigecycline antibiotics was observed in isolated MRSA strains compared to the previous period. We consider a major control and surveillance program of antibiotic use in veterinary care is needed in order to reduce the presence of MRSA strains in livestock and control this significant multi-resistance increase.

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Background: Livestock-associated methicillin-resistant Staphylococcus aureus (MRSA) such as the MRSA ST398 strain has spread all over the World and the most worrying aspect of this fact appears to be its capacity to easily spread to humans. The excessive use of antibiotics has made swine a reservoir of MRSA. The aim of the present study was to determine the antibiotic resistance profile of MRSA samples isolated from healthy swine of the island of Tenerife (Spain). Methods: A total of 256 MRSA isolates from swine samples and five MRSA isolates from pig worker samples were investigated for MRSA antibiotic resistant patterns. Results: Analysis of the susceptibility status of MRSA pig isolates revealed that 39 isolates were resistant to one antibiotic, 71 isolates were resistant to two antibiotics and 96 isolates were resistant to three or more antibiotics. SCCmec typing revealed the presence of types IV and V. Isolates having SCCmec IV had an increased resistance to the antimicrobial agents tested than those having SCCmec V. We observed significant differences when comparing the most common resistance patterns and SCCmec type. Conclusions: MRSA isolated from humans showed similar resistance to those isolated from pigs, excepting erythromycin, since all the workers’ isolates were sensitive to this antibiotic. The evolution of new MRSA clones has emphasized the need for infection control practices in animals and humans in close contact.