title: Presence of both heterogeneous vancomycin-intermediate resistance and β-lactam antibiotic-induced vancomycin resistance phenotypes is associated with the outcome in methicillin-resistant Staphylococcus aureus bloodstream infection.
abstract: BACKGROUND
  Although the individual expression of heterogeneous vancomycin-intermediate resistance (hVISA) and β-lactam antibiotic-induced vancomycin resistance (BIVR) phenotypes has been associated with treatment failure and recurrence in methicillin-resistant Staphylococcus aureus (MRSA) infections, the effect of the co-expression of these phenotypic profiles on clinical outcome has not been fully elucidated. The aim of this study was to determine the impact of the combination of hVISA and BIVR phenotypes on the clinical outcome in MRSA bacteremia.
  
  
  METHODS
  One hundred and sixty-two MRSA blood isolates from a 21-y period, 1987-2007, were randomly selected. Screening for hVISA was done by the macromethod Etest and confirmed by population analysis profiles. BIVR was identified using Mu3 agar containing 4 μg/ml of vancomycin.
  
  
  RESULTS
  Thirty (18.5%) and 39 (24.1%) of the 162 MRSA blood isolates were positive for the hVISA and BIVR phenotypes, respectively. Eighteen (11.1%) isolates possessed both hVISA and BIVR phenotypes (hVISA(+)/BIVR(+)). In a subset of patients who received initial treatment with glycopeptides, only the patients whose isolates were hVISA(+)/BIVR(+) displayed a significantly higher mortality rate in comparison to those with non-hVISA(+)/BIVR(+) (80.0% vs 31.3%, p = 0.004). The presence of both hVISA and BIVR phenotypes was a predictor of mortality using a logistic regression analysis (p = 0.025).
  
  
  CONCLUSIONS
  The combined phenotype of hVISA and BIVR was associated with a higher probability of mortality in patients with MRSA bacteremia. Further prospective studies are warranted to delineate the clinical significance of the combined phenotype of hVISA and BIVR.
authors.affiliation: Division of Oncology, Department of Medicine, Fukuoka University School of Medicine, Fukuoka University School ofMedicine, Fukuoka, Japan. takattol@cis.fukuoka-u.ac.jp
authors.forename: Tohru
authors.initials: T
authors.lastname: Takata
authors.forename: Motoyasu
authors.initials: M
authors.lastname: Miyazaki
authors.forename: Maki
authors.initials: M
authors.lastname: Futo
authors.forename: Shuji
authors.initials: S
authors.lastname: Hara
authors.forename: Shouichi
authors.initials: S
authors.lastname: Shiotsuka
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Kamimura
authors.forename: Hisae
authors.initials: H
authors.lastname: Yoshimura
authors.forename: Akira
authors.initials: A
authors.lastname: Matsunaga
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nishida
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Ishikura
authors.forename: Takahiko
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Kazuo
authors.initials: K
authors.lastname: Tamura
authors.forename: Brian T
authors.initials: BT
authors.lastname: Tsuji
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016470:Bacteremia / Q000188:drug therapy / Q000382:microbiology*; D015897:Comorbidity; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects* / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D010641:Phenotype; D012189:Retrospective Studies; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000382:microbiology*; D016896:Treatment Outcome; D020713:Vancomycin Resistance; D047090:beta-Lactams / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D047090:beta-Lactams