Abstract

Beta-hemolytic streptococci have been isolated from Southern sea otters (Enhydra lutris nereis) stranded off the central coast of California (USA). These bacteria, implicated in debilitating pathological processes such as pneumonia, septicemia, abscesses and opportunistic infections of external wounds, have not been characterized to the species level. Other studies in marine mammals have identified Streptococcus phocae (Lancefield group C and F) and Streptococcus dysgalactiae subsp. dysgalactiae (Lancefield group G and L). These studies have been routinely used to base presumptive identifications of beta-hemolytic streptococci isolated from marine mammals. Due to substantial phenotypic variation within Southern sea otter isolates observed at the Veterinary Medical Teaching Hospital at the University of California, Davis, this study aims to characterize beta-hemolytic streptococci in Southern sea otters.

Between 1998 and 2002, thirty-five beta-hemolytic streptococcal isolates were cultured from inflammatory lesions during ante- and post-mortem examinations of Southern sea otters at California Department of Fish and Game, Santa Cruz. Standard microbiologic and molecular techniques were used for characterization. These isolates predominately expressed cell surface antigens consistent with Lancefield group F and G (35.3% and 47.1%, respectively). Fewer isolates were typed as Lancefield group C (5.9%) or remained untypeable (11.7%) by methods used. Phenotypic analysis by biochemical profiles (API Strep 20) was inadequate for identification to the species level. Sequence analysis of a portion of the 16s ribosomal RNA gene identified Lancefield group F isolates as Streptococcus phocae. Lancefield group G isolates were genotypically identified as S. phocae and Streptococcus dysgalactiae sp. A single isolate, untypeable by Lancefield serology, was also identified as S. phocae. This is the first report of S. phocae in Southern sea otters, the first report of S. phocae in marine mammals in the Pacific Ocean and the first description of the streptococcal species expressing Lancefield group G cell surface antigens. This study will be included in a larger survey of bacterial pathogens and normal flora of Southern sea otters.