Utility of MALDI-TOF mass spectrometry in an outbreak investigation of acute endophthalmitis following intravitreal injection

Bevacizumab, a recombinant humanized monoclonal antibody to inhibit tumour angiogenesis, is available for off-label use for treating choroidal neovascularization. Outbreaks have been reported after use of this drug, either because of contamination during manufacturing or the practice of multiple doses being administered from a single vial to different patients. In our institute we investigated one endophthalmitis outbreak following intravitreal injection of bevacizumab, rapidly identified the Stenotrophomonas maltophilia as the causative agent, and established the contaminated bevacizumab vial as the source using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF-MS) typing. The study emphasizes the need for early diagnosis of the source and pathogen for appropriate control measures.