title: Difference in agr dysfunction and reduced vancomycin susceptibility between MRSA bacteremia involving SCCmec types IV/IVa and I-III.
abstract: BACKGROUND
  Dysfunction of agr, with reduced susceptibility or hetero-resistance to vancomycin, is thought to be associated with a worse outcome of methicillin-resistant Staphylococcus aureus (MRSA) bacteremia (MRSAB). However, the difference in agr dysfunction according to the SCCmec type in MRSA infection is undetermined. We compared the prevalence of agr dysfunction, reduced vancomycin susceptibility and the outcomes of SCCmec IV/IVa and I-III MRSAB.
  
  
  METHODS
  The study included 307 cases of MRSAB. SCCmec types were determined by multiplex PCR. The clinical and microbiological features and outcomes of 58 SCCmec IV/IVa MRSAB were compared with those of 249 SCCmec I-III MRSAB.
  
  
  RESULTS
  Compared with SCCmec I-III MRSAB, SCCmec IV/IVa MRSAB was associated with lower rates of agr dysfunction (3% vs. 43%), vancomycin minimum inhibitory concentration (MIC) = 2 µg/mL (3% vs. 15%), and hetero-resistance to vancomycin (0% vs. 8%) (all P<0.05). However, the 30-day and S. aureus-related mortality in patients with SCCmec IV/IVa MRSAB were not different from those in patients with SCCmec I-III MRSAB in multivariate analyses (HR 1.168, 95% CI 0.705-1.938; HR 1.025, 95% CI 0.556-1.889).
  
  
  CONCLUSIONS
  SCCmec IV/IVa MRSAB was associated with lower rates of agr dysfunction and hetero-resistance to vancomycin and a lower vancomycin MIC, compared with SCCmec I-III MRSAB. However, the outcomes of SCCmec IV/IVa MRSAB did not differ from those of SCCmec I-III MRSAB.
authors.affiliation: Department of Infectious Diseases, Chonnam National University Medical School, Gwang-ju, Republic of Korea.
authors.forename: Hee-Chang
authors.initials: HC
authors.lastname: Jang
authors.forename: Seung-Ji
authors.initials: SJ
authors.lastname: Kang
authors.forename: Su-Mi
authors.initials: SM
authors.lastname: Choi
authors.forename: Kyung-Hwa
authors.initials: KH
authors.lastname: Park
authors.forename: Jong-Hee
authors.initials: JH
authors.lastname: Shin
authors.forename: Hyon E
authors.initials: HE
authors.lastname: Choy
authors.forename: Sook-In
authors.initials: SI
authors.lastname: Jung
authors.forename: Hong Bin
authors.initials: HB
authors.lastname: Kim
mesh_terms: D016470:Bacteremia / Q000097:blood / Q000188:drug therapy / Q000382:microbiology* / Q000401:mortality; D001426:Bacterial Proteins / Q000378:metabolism*; D006801:Humans; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification* / Q000187:drug effects* / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D015999:Multivariate Analysis; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000097:blood / Q000188:drug therapy / Q000382:microbiology / Q000401:mortality; D015534:Trans-Activators / Q000378:metabolism*; D014640:Vancomycin / Q000494:pharmacology* / Q000627:therapeutic use
chemical_list: C095698:Agr protein, Staphylococcus aureus; D001426:Bacterial Proteins; D015534:Trans-Activators; D014640:Vancomycin