Streptococcus canis infections in humans: retrospective study of 54 patients

This 5-year retrospective study reports 54 patients with infection, caused by Streptococcus canis, a pyogenic Lancefield group G streptococcus initially isolated from various animal sources. During 1997-2002, Streptococcus canis accounted for 1% of all streptococci isolated. The clinical signs, outcome and bacteriological characteristics were reviewed. All except eight were symptomatic. Clinical manifestations were: soft tissue infection (n=35), bacteremia (n=5), urinary infection (n=3), bone infection (n=2) and pneumonia (n=1). The course was favorable in 52 cases while two died from sepsis. Cultures were often polymicrobial (n=42, 77.8%) apart from hemocultures. The isolates were sensitive to most antibiotics. Presence of the bacteria did not always signify infection owing to the possible occurrence of colonization. The frequency of S. canis infections is rare and likely underestimated owing to the fact that streptococci are sought only on the basis of the Lancefield classification. The search for S. canis is recommended whenever patients present with symptoms evocative of exposure to a potentially contaminated animal.