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.