title: Impact of psm-mec in Methicillin-Resistant Staphylococcus aureus (ST764) Strains Isolated from Keratitis Patients.
abstract: Staphylococcus aureus is a predominant pathogen in keratitis, and the rate of methicillin-resistant S. aureus (MRSA) is increasing. In our previous study, genotypes of MRSA isolates from keratitis cases were classified into ST5 or ST764 lineage by multi-locus sequence typing. In this study, we examined the virulence properties of these MRSA keratitis isolates and its virulence determinants. There was no difference in the prevalence of virulence genes, such as adhesion and toxins, between ST5 and ST764 isolates. All ST5 isolates carried the intact psm-mec gene, which suppresses exotoxin production and colony spreading, but promotes biofilm formation. In contrast, all ST764 isolates had one point mutation in the psm-mec gene. Biofilm production in ST5 isolates was significantly higher than that in ST764 isolates, whereas colony spreading, hemolytic activity, and production of alpha-phenol-soluble modulins were higher in ST764 than in ST5 isolates. The toxicity of ST764 supernatants to corneal epithelial cells was higher than that of ST5 supernatants. These results suggest that the point mutation in the psm-mec gene contributes to the difference in virulence properties between ST5 and ST764 isolates in MRSA keratitis.
authors.affiliation: 1 Department of Ophthalmology, Ehime University Graduate School of Medicine , Toon, Japan .
authors.forename: Takashi
authors.initials: T
authors.lastname: Suzuki
authors.affiliation: 1 Department of Ophthalmology, Ehime University Graduate School of Medicine , Toon, Japan .
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Yamamoto
authors.affiliation: 2 Laboratory of Microbiology, Graduate School of Pharmaceutical Sciences, The University of Tokyo , Tokyo, Japan .
authors.forename: Chikara
authors.initials: C
authors.lastname: Kaito
authors.affiliation: 3 Department of Clinical Laboratory, Ehime University Hospital , Toon, Japan .
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Miyamoto
authors.affiliation: 1 Department of Ophthalmology, Ehime University Graduate School of Medicine , Toon, Japan .
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Ohashi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D015373:Bacterial Typing Techniques; D018441:Biofilms / Q000187:drug effects / Q000254:growth & development*; D002461:Cell Line, Transformed; D002470:Cell Survival / Q000187:drug effects; D003315:Cornea / Q000166:cytology / Q000187:drug effects; D017077:Culture Media, Conditioned / Q000633:toxicity; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects; D005260:Female; D015870:Gene Expression; D006801:Humans; D007634:Keratitis / Q000188:drug therapy / Q000382:microbiology / Q000473:pathology*; D008297:Male; D008712:Methicillin / Q000494:pharmacology; D016106:Methicillin Resistance / Q000235:genetics*; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects / Q000235:genetics* / Q000472:pathogenicity / Q000502:physiology; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D017354:Point Mutation; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000382:microbiology / Q000473:pathology*; D037521:Virulence Factors / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D017077:Culture Media, Conditioned; D037521:Virulence Factors; D008712:Methicillin
keywords: MLST; MRSA; Staphylococcus aureus; psm-mec; virulence