Staphylococcus aureus carriage among food handlers in a pasta company: pattern of virulence and resistance to linezolid

This study aimed at monitoring and characterize the Staphylococcus aureus carriage status of employees in a pasta company in order to evaluate the associated risk factors. Food handlers (n = 21) were sampled between 2013 and 2015 through nasal and hand swabs to determine the colonization status. Seven out of 21 employees (33%) were contaminated with S. aureus and the prevalence decreased to 9.5% over the last year. Only two persistent carriers were identified. Twenty-eight strains were isolated from both hand and nasal samples. Each of them was resistant to at least one class of antibiotics and the multidrug resistance strains were isolated from the nose. The highest resistance rate was observed towards penicillin G (79%) and to linezolid (64%) confirming the rapid spread of linezolid resistant strains recently described in Italy. The dominant toxin gene was sem (93%), which is usually not among the most prevalent, whereas the primary agr group was the agrIII (43%) and the most frequent spa type was t030 (39%). These results combined with the genomic macrorestriction analysis revealed high genetic diversity. The increased virulence, antibiotic resistance and molecular variability of isolates highlighted the importance of monitoring activity in food company to assess the potential associated risk of foodborne diseases.