Bactec™ blood culture bottles allied to MALDI-TOF mass spectrometry: Rapid etiologic diagnosis of bacterial endophthalmitis

Abstract

Purpose : To evaluate matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry (MS) for direct identification (ID) of the etiologic agents of endophthalmitis from vitreous humor-inoculated blood culture bottles (BCBs).

Methods : A prospective study was conducted in a tertiary hospital in São Paulo, Brazil. From October 2015 to November 2016, patients with clinical suspicion of endophthalmitis had vitreous humor samples inoculated in blood culture bottles (BCBs). Positive BCBs were initially seeded in culture plates according to standard procedures. After standard procedure, aliquots from positive BCBs were immediately submitted to a simple in-house protein extraction protocol for direct ID by MALDI-TOF MS. The microorganisms’ ID and turnaround time (TAT) by standard method and direct MALDI-TOF analysis were compared.

Results : Forty-one samples of vitreous humor from 31 patients were analyzed. In 90.2% of cases, direct MALDI-TOF MS analysis from positive BCBs successfully identified the pathogen. The median TAT for pathogen ID by standard subculture and direct MALDI-TOF MS analysis was 70.2 h (32.5 h-212.9 h) and 14.7 h (2.4 h - 94.0 h), respectively (p <0.0001). Box-and-Whiskers plot of the TAT for pathogen identification according to methodology is represented below (Direct: TAT for direct pathogen identification from vitreous humor-inoculated blood culture bottles by MALDI-TOF mass spectrometry. Standard: TAT for pathogen identification after subculture of from blood culture bottles).

Conclusions : Direct pathogen ID of vitreous humor-inoculated BCBs by MALDI-TOF MS is an accurate and useful technique for rapid ID of the causative agents of endophthalmitis.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.