July 2019
Volume 60, Issue 9
Free
ARVO Annual Meeting Abstract  |   July 2019
Rapid Pathogen Identification with Matrix Assisted Laser Desorption-Ionization Time-of-Flight Mass Spectrometry and Rapid Antimicrobial Susceptibility Testing with Vitek 2 in In-Vitro Endophthalmitis without Prior Culture
Author Affiliations & Notes
  • Lindsay Chun
    University of Chicago Pritzker School of Medicine, Chicago, Illinois, United States
    Department of Ophthalmology and Visual Science, University of Chicago Medical Center, Chicago, Illinois, United States
  • Laura Dolle-Molle
    Clinical Microbiology Laboratory, University of Chicago Medical Center, Chicago, Illinois, United States
  • Dominique Missiakas
    Department of Microbiology, University of Chicago, Chicago, Illinois, United States
  • Olaf Schneewind
    Department of Microbiology, University of Chicago, Chicago, Illinois, United States
  • Kathleen Beavis
    Clinical Microbiology Laboratory, University of Chicago Medical Center, Chicago, Illinois, United States
    Department of Pathology, University of Chicago Medical Center, Chicago, Illinois, United States
  • Dimitra Skondra
    Department of Ophthalmology and Visual Science, University of Chicago Medical Center, Chicago, Illinois, United States
  • Footnotes
    Commercial Relationships   Lindsay Chun, None; Laura Dolle-Molle, None; Dominique Missiakas, None; Olaf Schneewind, None; Kathleen Beavis, None; Dimitra Skondra, None
  • Footnotes
    Support  Illinois Society for the Prevention of Blindness, Calvin Fentress Award - University of Chicago Pritzker School of Medicine
Investigative Ophthalmology & Visual Science July 2019, Vol.60, 3256. doi:
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      Lindsay Chun, Laura Dolle-Molle, Dominique Missiakas, Olaf Schneewind, Kathleen Beavis, Dimitra Skondra; Rapid Pathogen Identification with Matrix Assisted Laser Desorption-Ionization Time-of-Flight Mass Spectrometry and Rapid Antimicrobial Susceptibility Testing with Vitek 2 in In-Vitro Endophthalmitis without Prior Culture. Invest. Ophthalmol. Vis. Sci. 2019;60(9):3256.

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

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Abstract

Purpose : Culture-based microbiological techniques currently used for endophthalmitis diagnosis are slow, costly, and of suboptimal sensitivity. Matrix Assisted Laser Desorption-Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) and automated antimicrobial susceptibility test systems (AST, VITEK 2) can rapidly identify and establish antimicrobial susceptibility profiles, respectively, of organisms grown in culture. We investigated the ability of MALDI-TOF MS and VITEK 2 to bypass culture and directly analyze intraocular samples from in-vitro endophthalmitis.

Methods : Vitreous humor (VH) aspirated from porcine eyes was inoculated with different concentrations of methicillin-resistant Staphylococcus aureus (MRSA), and incubated at 37°C as a model of in-vitro endophthalmitis. Samples were centrifuged into bacterial pellets to concentrate the bacterial load. Bacterial pellets were directly analyzed with MALDI-TOF MS (Vitek MS), spotting portions of bacterial pellets onto the target plate. For VITEK 2 analysis, bacterial pellets were loaded into cartridges (VITEK 2 AST-GP67 cartridge) per manufacturer’s instructions. MRSA colonies traditionally grown in culture were used as positive control for analysis for MALDI-TOF MS and VITEK 2 per protocol.

Results : MALDI-TOF MS achieved accurate pathogen identification with confidence values of up to 99.9% from bacterial pellets and positive control within <30 minutes of sample processing. The minimum bacteria needed for positive identification from direct analysis was 7.89x103cfu/μl with 96.1% confidence value. VITEK 2 gave an AST profile up to 94.4% identical to the positive control analyzed per standard protocol. The minimum bacteria needed for positive AST profiles was 7.00x104cfu/μl, and this analysis gave an AST profile that was 88.9% identical to the AST profile of the positive control.

Conclusions : Our findings suggest that direct analysis of in-vitro endophthalmitis samples without prior culture with MALDI-TOF MS and VITEK 2 could serve as novel, fast, and adjuvant methods for rapidly identifying the pathogen and antimicrobial susceptibilities with high sensitivity and gain-of-time of hours to days compared to traditional methods. Further pre-clinical and clinical studies are needed to validate their clinical use.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

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