The genus Streptococci has undergone major revisions. Phenotypic and genetic studies have resulted in a number of taxonomic and nomenclature changes.1,2 Organisms historically classified as Streptococcus bovis or S. equinus are now represented by several biotypes. Some atypical variant strains of S. bovis isolated from humans and food have been reclassified as S. infantarius3 and are further divided into 2 subspecies S. infantarius subsp. infantarius and subsp. coli.4 Molecular characterizations have determined that S. bovis and S. equinus belong to a single species, hence the 'S. bovis/S. equinus complex'.5 The most recent proposal for the S. bovis/S. equinus complex is to be divided into 4 species: S. alactolyticus, S. equinus (containing 2 subspecies), S. gallolyticus (containing 3 subspecies) and S. infantarius (containing 2 subspecies).6 With these current taxonomic changes in mind, previous isolates identified as S. bovis from the blood of umans, animals and marine mammals with bacteremia, sepsis and endocarditis need further evaluation.
S. infantarius subsp. coli was recovered from seven sea otters with valvular endocarditis (heart valve) and/or with sepsis (multiple organs). From three of the seven sea otters S. infantarius subsp. coli was cultured from the colon or the small intestine. Eight isolates were identified as S. infantarius subsp. coli based on phenotypic characteristics and molecular methods. S. infantarius subsp. coli are gram-positive cocci arranged in pairs or short chains. Colonies observed after overnight incubation at 35C in an atmosphere of 5% CO2 on sheep blood agar were alpha hemolytic, round, clear and approximately 1 mm in size. Isolates were catalase negative and did not serologically type using a rapid latex test method, Streptex Kit (Remel Inc. Lenexa, KS), for detecting Lancefield group A,B,C,D,F or G. None of the isolates grew in 6.5% NaCl. Further phenotypic characteristics were determined by conventional physiologic tests, and both the API20 and the rapid ID32 STREP identification systems (BioMerieux, France). 16S rDNA gene sequence demonstrated 99-100% homology with S. infantarius subsp. coli for all eight isolates examined.
For antimicrobial susceptibility testing, the minimal inhibitory concentration (MIC) was determined utilizing a microdilution method with commercialized trays (Trek Diag. Sys., Cleveland, OH). The strains were susceptible to the majority of antibiotics tested. Pulse field gel electrophoresis studies are in progress to further compare relatedness of the different isolates.
James L. Bodkin (United States Geologic Survey, Alaska Science Center), Angela M. Doroff and Verena A. Gill (United State Fish and Wildlife Service, Anchorage, Alaska), Dr. Pamela Tuomi (Alaska Sea Life Center, Seward, Alaska) and Dr. Melissa A. Miller (Marine Wildlife Veterinary Care and Research Center, Department of Fish and Game, Santa Cruz, CA).
1. Facklam RR. 2002. What happened to the Streptococci: Overview of taxonomic and nomenclature changes. Clin Micro Rev. Vol. 15(4). 613-630.
2. Facklam RR. 2001. Newly described, difficult-to-identify, catalase-negative gram-positive cocci. Clin Micro Newsl. Vol 23(1). 1-7.
3. Bouvet A, et al. 1997. Streptococcus infantarius sp.nov. related to S. bovis and S. equinus. Adv Exp Med Biol. Vol 418. 393-395.
4. Schlegel L, et al. 2000. Streptococcus infantarius sp. nov., Streptococcus infantarius subsp. infantarius subsp. nov. and Streptococcus infantarius subsp. coli subsp. nov., isolated from humans and food. Int J Sys Evolut Microbiol Vol. 50. 1425-1434.
5. Schlegel L, et al. 2003. Reappraisal of the taxonomy of the Streptococcus bovis/Streptococcus equinus complex and related species: description of Streptococcus gallolyticus subsp. gallolyticus subsp. nov., S. gallolyticus subsp. macedonicus subsp. nov. and S. gallolyticus subsp. pasteurianus subsp. nov.. Int J Sys Evol Microbiol Vol. 53. 631-645.
6. Teixeira LM, et al., personal communication, Instituto de Microbiologia, Universidade Federal do Rio De Janeiro, Rio de Janeiro, Brazil.