April 2014
Volume 55, Issue 13
Free
ARVO Annual Meeting Abstract  |   April 2014
Correlation of Phenotypic Expression of Methicillin Resistance with Genotype and In Vitro Susceptibility for mecA+ Staphylococcus epidermidis Endophthalmitis Isolates
Author Affiliations & Notes
  • Laura C Huang
    University of Miami Miller School of Medicine, Miami, FL
  • Jack Stringham
    Bascom Palmer Eye Institute, Miami, FL
  • James Wong
    University of Miami Miller School of Medicine, Miami, FL
  • Jorge Maestre
    Bascom Palmer Eye Institute, Miami, FL
  • Darlene Miller
    Bascom Palmer Eye Institute, Miami, FL
  • Harry W Flynn
    Bascom Palmer Eye Institute, Miami, FL
  • Footnotes
    Commercial Relationships Laura Huang, None; Jack Stringham, None; James Wong, None; Jorge Maestre, None; Darlene Miller, None; Harry Flynn, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science April 2014, Vol.55, 5784. doi:
  • Views
  • Share
  • Tools
    • Alerts
      ×
      This feature is available to authenticated users only.
      Sign In or Create an Account ×
    • Get Citation

      Laura C Huang, Jack Stringham, James Wong, Jorge Maestre, Darlene Miller, Harry W Flynn; Correlation of Phenotypic Expression of Methicillin Resistance with Genotype and In Vitro Susceptibility for mecA+ Staphylococcus epidermidis Endophthalmitis Isolates. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5784.

      Download citation file:


      © ARVO (1962-2015); The Authors (2016-present)

      ×
  • Supplements
Abstract

Purpose: To correlate the genotypic methicillin resistance conferred by the mecA gene with phenotypic expression of methicillin resistance among Staphylococcus (S) epidermidis isolates from endophthalmitis and in vitro susceptibility to ceftaroline, a new fifth generation cephalosporin, and other commonly used antimicrobials.

Methods: Etests and the VITEK 2 system were used to detect the presence and phenotypic expression of methicillin resistance among S. epidermidis isolates recovered from endophthalmitis. Results were compared with mecA genotype using polymerase chain reaction (PCR) and in vitro susceptibility to ceftaroline and vancomycin (Etests) and VITEK 2 breakpoints for gentamicin, daptomycin, linezolid, tigecycline, levofloxacin, and moxifloxacin. Additionally, antibiotic susceptibility was analyzed against the following subgroups: mecA+ with methicillin resistance (group A) and isolates that were mecA+ though clinically methicillin sensitive (group B).

Results: All 32 isolates recovered from 2010-2013 were mecA-genotype positive (100%), however, only 21/32 (65.6%) expressed methicillin resistance by conventional laboratory tests. Isolates were 100% susceptible to vancomycin (MIC90 3 μg/mL, N=32), ceftaroline (MIC90 0.38 μg/mL, N=32), linezolid (N=20), and tigecycline (N=20). The susceptibility of daptomycin (N=20) was 95%. Gentamicin susceptibility overall was 86.7% (26/30) of which group A had 78.9% (15/19) susceptible compared to 100% (11/11) in group B. A correlation between the phenotypic expression of mecA genotype and in vitro susceptibility was demonstrated for the fluoroquinolones. For levofloxacin, group A had 21.1% (4/19) susceptible in contrast to 81.8% (9/11) (p=0.001) in group B. For moxifloxacin, group A had 30% (3/10) susceptible compared to 80% (8/10) (p=0.025) in group B.

Conclusions: Routine laboratory methods may fail to detect heterogeneous and or low level expression of methicillin resistance among mecA+ S. epidermidis genotypes. This may have important implications for the correct selection and management of S. epidermidis endophthalmitis. The new fifth generation cephalosporin, ceftaroline, demonstrated low MIC values and may show promise as a therapeutic agent for methicillin resistant S. epidermidis.

Keywords: 513 endophthalmitis • 720 Staphylococcus • 422 antibiotics/antifungals/antiparasitics  
×
×

This PDF is available to Subscribers Only

Sign in or purchase a subscription to access this content. ×

You must be signed into an individual account to use this feature.

×