title: Methicillin-resistant and methicillin-susceptible Staphylococcus aureus in dairy sheep and in-contact humans: An intra-farm study.
abstract: Staphylococcus aureus is involved in a wide variety of diseases in humans and animals, and it is considered one of the most significant etiological agents of intramammary infection in dairy ruminants, causing both clinical and subclinical infections. In this study, the intra-farm prevalence and circulation of methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) were investigated on an Italian dairy sheep farm previously identified as MRSA-positive by testing bulk tank milk (first isolation in 2012). Human samples (nasal swabs, hand skin samples, and oropharyngeal swabs) from 3 persons working in close contact with the animals were also collected, and the genetic characteristics and relatedness of the MRSA isolates from human and animal sources within the farm were investigated. After 2yr from the first isolation, we confirmed the presence of the same multidrug-resistant strain of MRSA sequence type (ST)1, clonal complex (CC)1, spa type t127, staphylococcal cassette chromosome mec (SCCmec) type IVa, showing identical pulsed field gel electrophoresis (PFGE) and resistance profiles at the farm level in bulk tank milk. Methicillin-resistant S. aureus isolates were detected in 2 out of 556 (0.34%) individual milk samples, whereas MSSA isolates were detected in 10 samples (1.8%). The MRSA were further isolated from udder skin samples from the 2 animals that were MRSA-positive in milk and in 2 of the 3 examined farm personnel. All MRSA isolates from both ovine and human samples belonged to ST(CC)1, spa type t127, SCCmec type IVa, with some isolates from animals harboring genes considered markers of human adaptation. In contrast, all MSSA isolates belonged to ruminant-associated CC130, ST700, spa type t528. Analysis by PFGE performed on selected MRSA isolates of human and animal origin identified 2 closely related (96.3% similarity) pulsotypes, displaying only minimal differences in gene profiles (e.g., presence of the immune evasion cluster genes). Although we observed low MRSA intra-farm prevalence, our findings highlight the importance of considering the possible zoonotic potential of CC1 livestock-associated MRSA, in view of the ability to persist over years at the farm level. Biosecurity measures and good hygiene practices could be useful to prevent MRSA spread at the farm level and to minimize exposure in the community and in categories related to farm animal industry (e.g., veterinarians, farmers, and farm workers).
authors.affiliation: Istituto Zooprofilattico Sperimentale del Lazio e della Toscana "M. Aleandri," General Diagnostic Department, National Reference Laboratory for Antimicrobial Resistance, Via Appia Nuova 1411, 00178 Rome, Italy.
authors.forename: V
authors.initials: V
authors.lastname: Carfora
authors.affiliation: Istituto Zooprofilattico Sperimentale del Lazio e della Toscana "M. Aleandri," Centro di Referenza Nazionale per la Qualità del Latte e dei Prodotti Derivati degli Ovini e dei Caprini, Via Appia Nuova 1411, 00178 Rome, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Giacinti
authors.affiliation: Istituto Zooprofilattico Sperimentale del Lazio e della Toscana "M. Aleandri," Centro di Referenza Nazionale per la Qualità del Latte e dei Prodotti Derivati degli Ovini e dei Caprini, Via Appia Nuova 1411, 00178 Rome, Italy.
authors.forename: D
authors.initials: D
authors.lastname: Sagrafoli
authors.affiliation: Istituto Zooprofilattico Sperimentale del Lazio e della Toscana "M. Aleandri," Centro di Referenza Nazionale per la Qualità del Latte e dei Prodotti Derivati degli Ovini e dei Caprini, Via Appia Nuova 1411, 00178 Rome, Italy.
authors.forename: N
authors.initials: N
authors.lastname: Marri
authors.affiliation: Istituto Zooprofilattico Sperimentale del Lazio e della Toscana "M. Aleandri," Centro di Referenza Nazionale per la Qualità del Latte e dei Prodotti Derivati degli Ovini e dei Caprini, Via Appia Nuova 1411, 00178 Rome, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Giangolini
authors.affiliation: Istituto Zooprofilattico Sperimentale del Lazio e della Toscana "M. Aleandri," General Diagnostic Department, National Reference Laboratory for Antimicrobial Resistance, Via Appia Nuova 1411, 00178 Rome, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Alba
authors.affiliation: Istituto Zooprofilattico Sperimentale del Lazio e della Toscana "M. Aleandri," General Diagnostic Department, National Reference Laboratory for Antimicrobial Resistance, Via Appia Nuova 1411, 00178 Rome, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Feltrin
authors.affiliation: Istituto Zooprofilattico Sperimentale del Lazio e della Toscana "M. Aleandri," General Diagnostic Department, National Reference Laboratory for Antimicrobial Resistance, Via Appia Nuova 1411, 00178 Rome, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Sorbara
authors.affiliation: Istituto Zooprofilattico Sperimentale del Lazio e della Toscana "M. Aleandri," General Diagnostic Department, National Reference Laboratory for Antimicrobial Resistance, Via Appia Nuova 1411, 00178 Rome, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Amoruso
authors.affiliation: Istituto Zooprofilattico Sperimentale del Lazio e della Toscana "M. Aleandri," General Diagnostic Department, National Reference Laboratory for Antimicrobial Resistance, Via Appia Nuova 1411, 00178 Rome, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Caprioli
authors.affiliation: Istituto Zooprofilattico Sperimentale del Lazio e della Toscana "M. Aleandri," Centro di Referenza Nazionale per la Qualità del Latte e dei Prodotti Derivati degli Ovini e dei Caprini, Via Appia Nuova 1411, 00178 Rome, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Amatiste
authors.affiliation: Istituto Zooprofilattico Sperimentale del Lazio e della Toscana "M. Aleandri," General Diagnostic Department, National Reference Laboratory for Antimicrobial Resistance, Via Appia Nuova 1411, 00178 Rome, Italy. Electronic address: antonio.battisti@izslt.it.
authors.forename: A
authors.initials: A
authors.lastname: Battisti
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000072480:Farms; D006801:Humans; D008712:Methicillin / Q000494:pharmacology; D016106:Methicillin Resistance; D055624:Methicillin-Resistant Staphylococcus aureus / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D012756:Sheep; D013203:Staphylococcal Infections / Q000662:veterinary; D013211:Staphylococcus aureus / Q000187:drug effects / Q000302:isolation & purification*
chemical_list: D000900:Anti-Bacterial Agents; D008712:Methicillin
keywords: clonal complex 1; dairy sheep; livestock-associated methicillin-resistant Staphylococcus aureus; zoonosis