Abstract
Purpose: :
To characterize the phenotypic and genotypic profiles of alpha-hemolytic streptococci recovered from patients who developed acute onset endophthalmitis after injection of Avastin.
Methods: :
Alpha-hemolytic streptococci isolated from intraocular fluids of 5 patients (n=6 isolates) and from Avastin syringe within the same lot (n=2 isolates) were analyzed by biochemical tests (Vitek 2), antimicrobial susceptibility testing (Etest) and partial sequencing of the gene groEL which encodes the 60 kDa heat-shock protein, highly conserved across species. Sequence similarity was searched in GenBank using the blastn program. Phylogenetic relationship among vitreous and Avastin isolates was inferred by Bayesian analysis using the general-time reversible (gamma-shaped) model of DNA substitution.
Results: :
Conventional biochemical tests identified the isolates from intraocular fluids and Avastin as Streptococcus mitis/oralis group (including mixed isolates in 1 patient) with probabilities ranging from 94% to 99%. All isolates were susceptible to moxifloxacin and vancomycin, but demonstrated intermediate resistance to penicillin. Sequence analysis permitted final species identification for 1 isolate as S. oralis and placed all the other within the S. mitis group. Bayesian analysis of partial groEL sequences revealed two major clusters with posterior probability of 100%. The minor cluster contained two genetically identical isolates from 2 different patients. The other cluster grouped all remaining isolates together within 3 small subclusters, the first including two genetically identical isolates from 2 different patients (posterior probability of 100%), the second and third included one patient and one Avastin isolate each, with posterior probabilities of 60% and 97% respectively.
Conclusions: :
Both conventional and molecular methods identified the outbreak isolates from patients and repackaged Avastin syringes as S. mitis/oralis group. Phylogeny inference using groEL sequences strongly implicates the repackaged Avastin syringes as the common source vehicle of this outbreak.
Keywords: endophthalmitis • injection