Título

MALDI-TOF MASS SPECTROMETRY: REDUCING TIME FOR ETIOLOGIC DIAGNOSIS IN BACTERIAL ENDOPHTHALMITIS

Objetivo

To describe the use of matrix-assisted laser desorption ionization - time of flight (MALDI-TOF) mass spectrometry (MS) for rapid identification (ID) of causative agents of endophthalmitis from vitreous humor-inoculated blood culture bottles (BCBs).

Método

This prospective study, conducted at Hospital das Clinicas from the University of Sao Paulo, included patients with clinical suspicion of endophthalmitis from October 2015 to November 2016. Vitreous samples obtained after biopsy or vitrectomy were inoculated in BCBs (Bactec Pediatric Plus, Becton Dickinson and Co., USA) and incubated in the Bactec FX system™ at 35°C for 5 days. Positive BCBs were seeded in culture plates. Aliquots from positive BCBs and microorganisms grown on culture plates were submitted for a protein extraction protocol for direct ID by MALDI-TOF MS. Final microorganisms’ ID and turnaround time (TAT) of both protocols (direct and grown in plates) were compared. P values ≤ 0.05 were considered statistically significant.

Resultado

Forty-one samples of vitreous humor from 31 patients were analyzed. Endophthalmitis cases were mainly associated with phacoemulsification (n=11) and trauma (n=4). The most prevalent agents were Staphylococcus spp. (41.4%). Thirty seven of 41 positive BCBs (90.2%) had correct species ID by direct MALDI-TOF MS analysis: 31 of 35 (88.5%) samples with Gram-positive pathogens and all samples with Gram-negative pathogens (n=6). Median TAT for pathogen identification by standard culture method and direct MALDI-TOF MS analysis from BCBs was 43.9h and 14.4h, respectively (p<0.001). Median TAT reduction for pathogen identification by direct MALDI-TOF MS analysis was 31.7h and 26h for samples with Gram-positive and Gram-negative bacteria, respectively (p=0.3).

Conclusão

Direct ID by MALDI-TOF MS of positive vitreous humor-inoculated BCBs could be a new alternative for clinical laboratories to hasten the etiologic diagnosis of bacterial endophthalmitis.