J. D. FULLER, D. E. LOW AND J. C. DE AZAVEDO; Mount Sinai / Princess Margaret Hospitals, University of Toronto, Toronto, Canada. Department of Laboratory Medicine and Pathobiology

Streptococcus iniae was first identified in 1976 and is recognized as an important fish pathogen in the aquaculture industry, primarily in tilapia and rainbow trout. Since early 1996, 12 cases in Canada of upper limb cellulitis in humans have been associated with S. iniae infection following percutaneous injury while handling fish. We have recently shown that S. iniae adheres to cultured larynx epithelial cells (HEp-2) and furthermore, is internalized within these cells. Using a standardized internalization assay, the number of bacteria internalized was 3 logs less (cfu/ml) than the number of HEp-2-associated bacteria (internalized and surface-adherent). No difference was found in either adherence or internalization between fish and human isolates. In comparison to other invasive streptococcal species, S. iniae was found to adhere 1 log less (cfu/ml) than both group A (GAS) and group B streptococci (GBS) but exhibited a similar internalization efficiency to GBS. Levels of S. iniae adherence and internalization using MRC-5 fibroblast cells were comparable to levels observed using HEp-2 cells. We hypothesize that direct invasion of eukaryotic tissue is an important step in the pathogenesis of S. iniae.

Presented at:

38^th INTERSCIENCE CONFERENCE ON ANTIMICROBIAL AGENTS AND CHEMOTHERAPY (ICAAC), San Diego, CA., Sept 20-29, 1998.