title: New insights in Staphylococcus pseudintermedius pathogenicity: antibiotic-resistant biofilm formation by a human wound-associated strain.
abstract: BACKGROUND
  Staphylococcus pseudintermedius is an opportunistic pathogen recognized as the leading cause of skin, ear, and post-operative bacterial infections in dogs and cats. Zoonotic infections have also recently been reported causing endocarditis, infection of surgical wounds, rhinosinusitis, and catheter-related bacteremia. The aim of the present study is to evaluate, for the first time, the pathogenic potential of S. pseudintermedius isolated from a human infection. To this end, strain DSM 25713, which was recently isolated from a wound of a leukemic patient who underwent a bone marrow transplantation, was investigated for biofilm formation and antibiotic-resistance under conditions relevant for wound infection.
  
  
  RESULTS
  The effect of pH (5.5, 7.1, and 8.7) and the presence of serum (diluted at 1:2, 1:10, and 1:100) on biofilm formation was assessed through a crystal violet assay. The presence of serum significantly reduced the ability to form biofilm, regardless of the pH value tested. In vitro activity of eight antibiotics against biofilm formation and mature 48 h-old biofilms was comparatively assessed by crystal violet assay and viable cell count, respectively. Antibiotics at sub-inhibitory concentrations reduced biofilm formation in a dose-dependent manner, although cefoxitin was the most active, causing a significant reduction already at 1/8xMIC. Rifampicin showed the highest activity against preformed biofilms (MBEC90: 2xMIC). None of the antibiotics completely eradicated the preformed biofilms, regardless of tested concentrations. Confocal and electron microscopy analyses of mature biofilm revealed a complex "mushroom-like" architecture consisting of microcolonies embedded in a fibrillar extracellular matrix.
  
  
  CONCLUSIONS
  For the first time, our results show that human wound-associated S. pseudintermedius is able to form inherently antibiotic-resistant biofilms, suggestive of its pathogenic potential, and consistent with recent reports of zoonotic infections.
authors.affiliation: Department of Medical, Oral, and Biotechnological Sciences, "G. d'Annunzio" University, Via Vestini 31, Chieti, 66100, Italy. ariannapompilio@yahoo.it.|Center for Research on Ageing, "G. d'Annunzio" University Foundation, Chieti, Italy. ariannapompilio@yahoo.it.
authors.forename: Arianna
authors.initials: A
authors.lastname: Pompilio
authors.affiliation: Department of Medical, Oral, and Biotechnological Sciences, "G. d'Annunzio" University, Via Vestini 31, Chieti, 66100, Italy. serenadenicola@gmail.com.|Center for Research on Ageing, "G. d'Annunzio" University Foundation, Chieti, Italy. serenadenicola@gmail.com.
authors.forename: Serena
authors.initials: S
authors.lastname: De Nicola
authors.affiliation: Department of Medical, Oral, and Biotechnological Sciences, "G. d'Annunzio" University, Via Vestini 31, Chieti, 66100, Italy. vale.crocetta@tiscali.it.|Center for Research on Ageing, "G. d'Annunzio" University Foundation, Chieti, Italy. vale.crocetta@tiscali.it.
authors.forename: Valentina
authors.initials: V
authors.lastname: Crocetta
authors.affiliation: Center for Research on Ageing, "G. d'Annunzio" University Foundation, Chieti, Italy. guarnie@unich.it.|Department of Neuroscience and Imaging, "G. d'Annunzio" University, Chieti, Italy. guarnie@unich.it.
authors.forename: Simone
authors.initials: S
authors.lastname: Guarnieri
authors.affiliation: Clinical Microbiology and Virology, "Spirito Santo" Hospital, Pescara, Italy. vsavini2013@gmail.com.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Savini
authors.affiliation: IRCCS Arcispedale, "Santa Maria Nuova", Reggio Emilia, Italy. edoardo.carretto@asmn.re.it.
authors.forename: Edoardo
authors.initials: E
authors.lastname: Carretto
authors.affiliation: Department of Medical, Oral, and Biotechnological Sciences, "G. d'Annunzio" University, Via Vestini 31, Chieti, 66100, Italy. gdibonaventura@unich.it.|Center for Research on Ageing, "G. d'Annunzio" University Foundation, Chieti, Italy. gdibonaventura@unich.it.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Di Bonaventura
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects*; D002440:Cefoxitin / Q000494:pharmacology; D024901:Drug Resistance, Multiple, Bacterial; D006801:Humans; D006863:Hydrogen-Ion Concentration; D012293:Rifampin / Q000494:pharmacology; D013203:Staphylococcal Infections / Q000382:microbiology; D013210:Staphylococcus / Q000187:drug effects* / Q000302:isolation & purification / Q000472:pathogenicity* / Q000502:physiology; D013530:Surgical Wound Infection / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; D002440:Cefoxitin; D012293:Rifampin