We report an unusual case of Mycobacterium peregrinum bacteremia and infection of an automatic implantable cardioverter defibrillator that was originally misidentified as a Nocardia sp. due, in part, to its partially acid-fast staining characteristic, morphology, and odor. The misdiagnosis had a direct effect on patient care, though the patient was subsequently successfully treated.
CASE REPORTA 74-year-old white male was admitted with a past history of ischemic cardiomyopathy, coronary artery disease, hypertension, and a recent diagnosis of nonsustained ventricular tachycardia requiring placement of an automatic implantable cardioverter defibrillator (AICD) 6 weeks earlier. He presented to our institution with persistent erythema and a history of a pustule around the AICD insertion site on his left chest wall. The patient stated he immediately noted erythema around the insertion site after AICD placement and was prescribed a 10-day course of cephalexin at a 3-week follow-up with his cardiologist. Subsequently, he noted a pustule along the suture line and was admitted for further evaluation and management. On physical examination he was nontoxic in appearance and afebrile, his vital signs were stable, and his physical examination was within normal limits except for the left chest area. The left chest wall was erythematous in an area of 4 to 5 cm where the AICD site had been inserted subcutaneously; there was a deep purple discoloration along the incision line, and the area was warm to touch and minimally tender to palpation. There was no obvious pustule or purulent discharge along the incision, and the surrounding area was not fluctuant. Laboratory data were unremarkable except for a creatinine level of 1.7 mg/dl, which was his baseline. Blood cultures were drawn on admission, and empirical vancomycin was begun. On the day of admission he underwent extraction of the AICD and the leads in the electrophysiology laboratory. Deep-pocket tissue and superficial wound specimens were sent for routine bacterial, fungal, and acid-fast bacillus cultures.The described wound specimens and two sets of blood cultures were submitted to the microbiology laboratory for bacterial culture. Direct Gram-stained smears of the wound cultures demonstrated rare to few polymorphonuclear leukocytes with no organisms seen. After 4 days of incubation, growth was detected in both blood cultures and in the thioglycolate broth media of both wound cultures.On the fifth hospital day, Gram-stained smears of the wound broth cultures were reported as having gram-positive rods. One day later, growth was detected on the sheep blood and chocolate agar plates, and no growth was detected on the MacConkey agar plate. Colonies were tan, flat, and dry and upon further incubation became wrinkled in appearance and exhibited a musty odor. The Vitek Identification System (bioMérieux, Hazelwood, MO) was unable to identify the isolate. The isolate was subcultured to Columbia agar for identification using the API CORYNE system (bioMérieux, Hazelwood, MO), but it t...