Toe Gangrene Revealing Septicaemical Rat-bite Fever: About a 41 Day Old Infant

Rat-bite fever (RBF) is a systemic infectious disease. It is due to Streptobacillus moniliformis, a commensal bacterium of the nasopharyngeal mucosa of small rodents, in particular rats. This anthropozoonosis is rare in urban areas. The first clinical sign of infection is a fever, followed by polyarthritis and a rash. It can only start with skin signs, as in our observation. We report the case of a 41-day-old female infant who was the victim of a rat bite at one month of life in the upper nasal and labial areas. A rabies vaccine with local care has been made. The clinical course at 3 days after the bite was marked by a non-pruritic papulopustular rash, the vesiculo-bullous lesions in the bilateral and symmetrical legs evolved into inflammatory ulcerative necrotizing lesions in a geographic map of the lower 1/3 of the lower limbs with gangrenous lesions in the toes, an erythematous base on the face, hands and feet and discreet oral erosions, associated with generalized purpuric spots and fevers at 40°C. The biological assessment was carried out objectifying an inflammatory syndrome made of a leukocytosis at 26770/mm3, with neutrophils at 10842/mm3, CRP = 215 mg/L. The diagnosis of RBF was made by the isolation of a Gram-negative bacillus in a blood culture. The final identification of the germ was carried out by molecular biology (PCR of 16S rRNA). The lumbar puncture was negative and the cardiac ultrasound was without abnormality. Arterial and venous Doppler ultrasound of the lower limbs was normal. The diagnosis of rat bite fever having been retained. The infant was put on cefpodoxime IV for 3 weeks and metronidazole IV for 10 days. The clinical course at 3 months later, spontaneous amputation of gangrenous toes with residual skin scars was noted.