Catheter-related blood stream infection caused by Tsukamurella Pulmosis.

A 42-year-old Japanese man with acute myelogenous leukemia (M0) who was undergoing aggressive chemotherapy (high-dose Ara-C) developed fever and chills. Two sets of aerobic culture of blood samples obtained from the central venous catheter prior to the start of the antimicrobial administration showed positive growth two days later. Gram staining revealed gram-positive rods (Fig. 1). The appearance of the colonies on chocolate agar is irregular, rough, dry and grey-to-white-colored colonies (Fig. 2). Since additional Kinyoun staining was positive, an initial diagnosis of infection caused by Nocardia species was made on the basis of the findings presented above. The central venous catheter was removed and culture of the catheter tip yielded growth similar to that of the blood culture. Molecular identification by sequencing analysis of th16S rRNA gene identified the isolate as Tsukamurella pulmosis. The patient was then started on treatment with a 4-week course of sulfamethoxazole/trimethoprim and imipenem, and follow-up blood cultures yielded no growth; no evidence of relapse of the infection was noted at the 6-month follow up either.

Fig. 1

Gram staining of blood cultures (×1000).

Fig. 2

Irregular, rough, dry and grey-to-white-colored colonies of the microorganism isolated from blood culture on chocolate agar.

Tsukamurella species are strictly aerobic gram-positve rods belonging to the order Actinomycetales, that are weakly acid-fact and related to other genera of this order, including Nocardia, Gordonia, Streptomyces, Rhodococcus, Mycobacterium, and Corynebacterium [1]. Tsukamurella infection was first described in 1971 by Japanese microbiologists, Tsukamura and Mizuno [2]. Tsukamurella has mainly been implicated in the development of catheter-related bloodstream infections in immunocompromised patients [3]. In a review, Bouza et al. reported that 12 of 14 patients with CR-BSI caused by Tsukamurella species were being treated for underlying malignancy, especially hematological malignancy, or were undergoing hemodialysis [4]. The isolates may be misidentified initially as Nocardia species, Corynebacterium species, Bacillus species, Rhodococcus species, or rapid growing mycobacterial species, especially when this organism is isolated from cases of pulmonary infections, because of the similarity of the findings on Gram staining, acid-fast staining, and microbiological characteristics [2], [4], [5].

No optimal therapy has been established yet. Tsukamurella species are usually susceptible to clarithromycin, amikacin, cipifofloxacin, rifampicin, imipenem, sulfamethoxazole, and vancomycin, but resistant to penicillin, oxacillin and cephalosporins [3], [4]. The optimal treatment duration is also unknown, however, a previous case series suggests that two to four weeks of treatment with removal of the culprit catheter might yield good outcomes [3], [4]; thus, not only the administration of appropriate antibiotic therapy, but also removal of the culprit catheters seems to be essential, as in the present case.

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Written informed consent was obtained from the patient for publication of this case report and accompanying images.

Declaration of Competing Interest

The author has no conflict of interest to disclose.