Blastoschizomyces capitatus infection in an immunocompetent man

February 1, 2007

Blastoschizomyces capitatus is an emerging pathogen that causes infection primarily in patients who have immune system dysfunction. The author reports a case of pulmonary blastoschizomycosis in an immunocompetent man who was successfully treated with voriconazole.

The case

A 64-year-old man was admitted to the hospital with fever, cough, and dyspnea. His cough was productive of a moderate amount of yellow-brown sputum and had developed 2 weeks earlier. The patient reported subjective fever, chills, fatigue, night sweats, and dyspnea at rest during the past week, and he had a 20-lb weight loss over the past month.

The patient was a heavy cigarette smoker and admitted to excessive consumption of alcohol. His history was notable for chronic obstructive pulmonary disease. At the time of presentation, he was not taking medications and he had no recent history of travel, contact with sick persons, or chemical exposure. The patient's sexual history revealed that he was homosexual.

Initial examination showed a temperature of 39.6ºC (103.3ºF), pulse rate of 110 beats per minute, respiration rate of 26 breaths per minute, blood pressure of 112/66 mm Hg, and oxygen saturation of 89% by pulse oximetry on ambient air. Physical examination revealed bilateral temporal muscle wasting. No lymphadenopathy was noted. A chest examination revealed diffuse bilateral rhonchi and crackles. Findings from the remainder of the patient's physical examination were unremarkable.

Laboratory studies were significant for a leukocyte count of 13,200/µL, with 85% neutrophils. Arterial blood gas analysis on room air showed a partial arterial oxygen pressure of 64 mm Hg. Results of serum chemistry, including transaminase levels, were normal. A chest radiograph showed hyperinflated lungs and diffuse nodular infiltrates (Figure 1). The patient was treated with supplemental oxygen, intravenous moxifloxacin, 400 mg daily; ceftriaxone, 1 g every 12 hours; and albuterol and ipratropium every 6 hours.

Blood and sputum cultures were negative, as were test results for HIV antibody and Legionella urinary antigen. After 5 days of therapy, the patient remained febrile and hypoxemic and required supplemental oxygen. A CT scan of the chest showed patchy central-lobular, nodular infiltrates (Figure 2).

On hospital day 7, bronchoscopy with protected brush sampling (PBS) and bronchoalveolar lavage (BAL) of the right middle lobe was performed; Gram stain demonstrated many neutrophils but no organisms. Stains for fungal elements, Mycobacterium, and Pneumocystis jiroveci, as well as cultures for viral and bacterial pathogens, were negative. On hospital day 9, fungal cultures of specimens obtained by BAL and PBS grew a yeast organism, which was identified as B capitatus by conventional methods and morphology, then confirmed by metabolic characteristics.

All antibiotics were discontinued, and the patient was given voriconazole, 200 mg daily; he completed a 7-day course in the hospital. He became afebrile and was weaned off oxygen, and his cough and dyspnea improved. Two acid-fast bacilli cultures (BAL fluid and sputum) grew Mycobacterium avium-intracellulare (MAI), but the patient was not treated for MAI infection. He was discharged on a 14-day regimen of voriconazole.

Discussion

B capitatus is the most likely pathogen responsible for pulmonary infection in our patient. The isolation of B capitatus from BAL and PBS makes specimen contamination unlikely. The patient's lack of response to wide-spectrum antibiotics and his clinical improvement after antifungal treatment also strongly suggest the presence of primary B capitatus pulmonary infection.

MAI was the only other pathogen identified; however, our patient clinically improved without specific treatment of MAI infection. Although moxifloxacin has some activity against MAI,1 the patient's clinical improvement was noted only after moxifloxacin was stopped and voriconazole was started, suggesting that MAI infection was not responsible for clinical manifestations of pulmonary disease.

B capitatus is a soil saprophyte that is a rare cause of invasive infections in immunocompromised patients,2 but infection in an immunocompetent patient is extremely rare. To my knowledge, only one previous report has described B capitatus pneumonia in an immunocompetent patient.2 Prolonged neutropenia, corticosteroid therapy, and leukemia are risk factors for B capitatus infection. B capitatus infection is also associated with cytotoxic chemotherapy, prolonged antibiotic use, and indwelling vascular devices. Systemic infections and localized infections in the lungs, esophagus, liver, bone, and meninges have been described.2-4

Morphologic characteristics of B capitatus include septate hyphae with narrow angle branching and annelloconidia (conidia with tapered ends). Microscopic examination of infected tissues may reveal a necrotic center with fungal elements that may invade the vasculature. Visualization of blastoconidia in a histologic section supports the diagnosis of invasive infection. The inflammatory infiltrate surrounding the fungal elements may be variable; it is occasionally associated with hemorrhage.

Although fluconazole, itraconazole, and amphotericin B can be used, resistance to these antifungal agents has been reported. In vitro susceptibility has been shown with caspofungin and voriconazole.4,5 Because there are no clinical trials to guide antifungal treatment in immunocompetent patients, such treatment requires close follow-up.

References:

REFERENCES

1. Bakker-Woudenberg IA, van Vianen W, van Soolingen D, et al. Antimycobacterial agents differ with respect to their bacteriostatic versus bactericidal activities in relation to time of exposure, mycobacterial growth phase, and their use in combination. Antimicrob Agents Chemother. 2005;49:2387-2398.

2. Wills TS, Degryse A, Lavina J, Sinnott JT. Blastoschizomyces capitatus pneumonia in an immunocompetent male. South Med J. 2004; 97:702-704.

3. Christakis G, Perlorentzou S, Aslanidou M, et al. Fatal Blastoschizomyces capitatus sepsis in a neutropenic patient with acute myeloid leukemia: first documented case from Greece. Mycoses. 2005;48:216-220.

4. Romano A, Giordano S, Di Carlo P, et al. Pulmonary infection caused by Blastoschizomices capitatus [in Italian]. Infez Med. 2005; 13:187-191.

5. Martino R, Salavert M, Parody R, et al. Blastoschizomyces capitatus infection in patients with leukemia: report of 26 cases. Clin Infect Dis. 2004;38:335-341.