Assessment of the Antibiotic Resistance Profile, Genetic Heterogeneity and Biofilm Production of Methicillin-Resistant <i>Staphylococcus aureus</i> (MRSA) Isolated from The Italian Swine Production Chain

• Main Authors: Pedro Rodríguez-López, Virginia Filipello, Pierluigi Aldo Di Ciccio, Alessandra Pitozzi, Sergio Ghidini, Federico Scali, Adriana Ianieri, Emanuela Zanardi, Marina Nadia Losio, Ancuta Cezara Simon, Giovanni Loris Alborali
• Format: Article
• Language: English
• Published: MDPI AG 2020-08-01
• Series: Foods
• Subjects: antibiotic susceptibility; antibiotic resistance; food safety; food hygiene; MRSA; prevalence
• Online Access: https://www.mdpi.com/2304-8158/9/9/1141

The main aim of the present study was to evaluate the level of antibiotic resistance, prevalence and virulence features of methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) isolated from heavy swine at abattoir level and farming environments in Lombardy (Northern Italy). With this scope, 88 different heavy swine farms were surveyed, obtaining a total of <i>n</i> = 440 animal swabs and <i>n</i> = 150 environmental swabs. A total of <i>n</i> = 87 MRSA isolates were obtained, with an overall MRSA incidence of 17.50% (<i>n</i> = 77) among animal samples and a 6.67% (<i>n</i> = 10) among environmental. Molecular characterisation using multilocus sequence typing (MLST) plus <i>spa</i>-typing showed that sequence type ST398/t899 and ST398/t011 were the most commonly isolated genotypes, although other relevant sequence types such as ST1 or ST97 were also found. A lack of susceptibility to penicillins, tetracycline and ceftiofur was detected in >91.95, 85.05 and 48.28% of the isolates, respectively. Resistance to doxycycline (32.18%), enrofloxacin (27.59%) and gentamicin (25.29%) was also observed. Additionally, a remarkable level of antibiotic multiresistance (AMR) was observed representing a 77.01% (<i>n</i> = 67) of the obtained isolates. Genetic analysis revealed that 97.70% and 77.01% of the isolates harboured at least one antibiotic resistance or enterotoxin gene, respectively, pointing out a high isolate virulence potential. Lastly, 55.17% (<i>n</i> = 48) were able to produce measurable amounts of biofilm after 24 h. In spite of the current programmes for antibiotic reduction in intensively farming, a still on-going high level of AMR and virulence potential in MRSA was demonstrated, making this pathogen a serious risk in swine production chain, highlighting once more the need to develop efficient, pathogen-specific control strategies.