Is Infection by Dermatophilus congolensis Underdiagnosed?

Abstract

Dermatophilus congolensis, which affects animal species, is an uncommon human infection. Few cases, mainly in tropical areas, have been reported. We describe the first human infection in Spain in a traveler returning from Central America. Diagnosis of human infection may be underestimated in people in contact with animals. CASE REPORTIn September 2009, a 26-year-old woman came to the Tropical Diseases Service, Hospital Carlos III, Madrid, Spain, with skin lesions on her right wrist and no other symptoms. Two months prior to her presentation, the patient spent 15 days in Costa Rica working as a volunteer on a dairy farm. She reported close contact with animals, including feeding and milking cows, as well as drinking raw milk. She did not report any other contact with livestock in Spain, either professionally or in leisure activities. The patient had been vaccinated against diphtheria and tetanus in 2003. In addition, she was vaccinated against hepatitis B (third dose), hepatitis A (first dose), typhoid fever, and rabies 2 weeks before her trip. She followed a correct malaria prophylaxis with chloroquine. No other previous medical history was of interest. Five days after her arrival in Costa Rica, she noticed a vesicular eruption over a scratched area on her right wrist that evolved to pustules and crust 4 days later. The eruption relapsed on several occasions and was painful and itchy. Neither fever nor lymph node swelling was present. She had begun self-treatment with topical gentamicin and corticosteroid ointment 1 month before medical consultation, with a mild improvement. The patient's physical examination revealed five erythematous, desquamative lesions of less than 0.5 cm in diameter and with elevated edges. Topical treatment was discontinued, and a sample for microbiological analysis was taken. One month later, the lesions had disappeared.Swab samples were taken from the lesions and sent to our laboratory for bacterial and fungal culture analyses. They were directly inoculated in blood and chocolate agar, thioglycolate broth, Sabouraud chloramphenicol, and Sabouraud cycloheximide (Actidione)-chloramphenicol agar. Blood and chocolate agar and thioglycolate broth were incubated at 35°C in an aerobic atmosphere, the chocolate agar was incubated in air supplemented with 5% CO 2 , and the blood agar was also incubated in an anaerobic atmosphere. Sabouraud chloramphenicol and Sabouraud cycloheximide-chloramphenicol agar plates were incubated at 32°C. After 24 h, a pure culture of tiny, point-like, smooth, creamy white-colored, beta-hemolytic colonies adherent to the media grew in aerobic blood agar and chocolate agar. Gram staining showed hypha-like, branching filaments with "train track" form and clusters of sporangia as well as coccoid Gram-positive forms, mostly in chains (Fig. 1). After 48 h, crowded colonies became yellowish and mucoid, with a great variation in colonial morphology, e.g., pulvinate, umbonate, or cake crumb-like (Fig. 2). At that time, released sporangia were the main finding in the Gram sta...

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