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2011 OMIG Abstract 11

Laboratorial investigation of an endophthalmits outbreak caused by
Streptococcus mitis group after intravitreal injection of Avastin

P.J.M. Bispo, M. Diaz, E. Perez, E.C. Alfonso, H. Flynn, R. Goldberg, D. Miller
Bascom Palmer Eye Institute, University of Miami, Miami, FL

Purpose: To characterize phenotypic and genotypic profile of alpha-hemolytic Streptococcus recovered from patients who developed acute onset endophthalmits after intravitreal injection of Avastin.

Methods: Alpha-hemolytic Streptococcus isolated from intraocular fluids of five patients (n=6 isolates) and from Avastin syringes within the same lot (n=2 isolates) were analyzed by biochemical tests (API and Vitek 2), antimicrobial susceptibility testing (Etest) and partial sequencing of the gene groEL, which encodes the 60 kDa heat-sock 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 samples as Streptococcus mitis/oralis group with probabilities ranging from 94% to 99%. All isolates were susceptible to levofloxacin and vancomycin and intermediate resistant to penicillin. Sequence analysis permitted final species identification for only one isolate as S. oralis and placed all the other within the mitis group. Bayesian analysis of partial groEL sequences revealed two major clusters with posterior probability of 100%. The minor cluster grouped two genetically identical isolates from two different patients. The other cluster grouped all the other isolates together within three small subclusters, the first including two genetically identical isolates from two 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: Definitive speciation of closely related Streptococcus mitis group is difficult and often requires a polyphasic taxonomy approach. Phylogeny inference using groEL sequences strongly suggests the Avastin as the common source vehicle of this outbreak.

Disclosure: N

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