Characterization and Clinical Manifestations of Arcanobacterium phocae Infections in Marine Mammals Stranded Along the Central California Coast
IAAAM Archive
Shawn Johnson1; Frances Gulland1; Judy Lawrence1; Spencer Jang2; Juliet Herrera2; Melissa Miller3; David Casper4
1The Marine Mammal Center, Marin Headlands, Sausalito, CA, USA; 2Diagnostic Microbiology Laboratory, Veterinary Medical Teaching Hospital, University of California, Davis, CA, USA; 3Marine Wildlife Veterinary Care and Research Center, California Department of Fish and Game, Santa Cruz, CA, USA; 4Long Marine Laboratory, Santa Cruz, CA, USA


Between 1994 and 2000, 141 Arcanobacterium phocae isolates were recovered from marine mammals that stranded along the central California coast. Arcanobacterium phocae was cultured from tissue sites with abnormal discharge or evidence of inflammation in 66 California sea lions (Zalophus californianus), 50 Pacific harbor seals (Phoca vitulina richardii), 19 northern elephant seals (Mirounga angustirostris), five southern sea otters (Enhydra lutris nereis), and one common dolphin (Delphinus delphis). The overall prevalence of A. phocae among cultured stranded marine mammals was 8%. Although common, this is the first report of A. phocae in the Pacific Ocean. Sequence analysis of a portion of the 16S ribosomal RNA gene confirmed recent isolates as A. phocae1. All A. phocae isolates were non-motile, catalase-positive, gram-positive coccobacilli or short rods that were beta-hemolytic on blood agar within 24 hours of inoculation. A reverse CAMP reaction resulted with Staphylococcus aureus and a positive CAMP reaction with Rhodococcus equi. Prior to phylogenetic testing and the routine use of the esculin hydrolysis and motility tests, A. phocae isolates had been misidentified as Listeria ivanovii. Arcanobacterium phocae was commonly isolated from superficial abscesses but occasionally was associated with systemic infections. Isolates were often present in mixed bacterial infections and were susceptible to all antimicrobial agents tested. Arcanobacterium phocae is most likely an opportunistic pathogen that can cause severe infection in animals with wounds or other pre-existing disease.


1.  Ramos CP, G Foster, MD Collins. 1997. Phylogenetic analysis of the genus Actinomyces based on 16S rRNA gene sequences: description of Arcanobacterium phocae sp. nov., Arcanobacterium bernardiae comb. nov., and Arcanobacterium pyogenes comb. nov. International Journal of Systematic Bacteriology 47:46-53.

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Shawn P. Johnson
The Marine Mammal Center, Golden Gate National Recreation Area
Sausalito, CA, USA

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