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Systemic infections due to Fusarium species are increasingly reported in immunosuppressed patients. The majority of these infections have a very poor outcome, especially if the host defenses do not recover. However, the pattern of infection as well as the prognosis may vary according to the species involved. In this paper, we report the first known case of fungemia due to Fusarium sacchari.

Case report. A 40-year-old man received a cadaveric renal transplant. During surgery, there was an accidental rupture of the bladder and a drain was inserted into the bladder. The patient was started on corticosteroids and azathioprine. A few days later, acute graft rejection was diagnosed and anti-OKT3 was added to the immunosuppressive therapy. On the 11th postoperative day, the patient developed a low-grade fever and leukocytosis. Three blood samples (10 ml each) were taken from peripheral veins at intervals of 15 min. Each blood culture sample was processed as follows. Each of two vented aerobic bottles containing 45 ml of brain heart infusion broth received 5 ml of blood from one sample. The bottles were incubated at 37°C, and after 6 to 24 h of incubation, blind subcultures were made. For the subculture, we used a biocontainment hood to inoculate plates of blood agar. New subcultures were performed only if an alteration in the broth was observed (hemolysis, turbidity, etc.). Both the bottles and the plates were produced in-house following strict quality control measures regarding sterility. After 5 days of incubation, two bottles were turbid and subcultures were performed. The subcultures were made by taking 0.5 ml of the liquid from the bottle with disposable syringes and inoculating it into four tubes containing one of the following solid media: brain heart infusion agar (Merck KgaA, Darmstadt, Germany), Sabouraud dextrose agar (Difco Laboratories, Detroit, Mich.), mycobiotic agar (Difco), and Niger seed agar. Fusarium colonies grew abundantly in all subcultures. They formed numerous confluent colonies, with more than 10 colonies in each tube. The patient had no central venous catheter, was well, and had no skin lesions or other complaints. On the 24th postoperative day, two blood samples were taken (15 min apart) from the peripheral veins; the four blood culture bottles were positive for the same Fusarium sp. A sample of urine was taken for culture and was negative. The patient's creatinine was checked and found to be 11 mg/dl, allowing us to start with a small dose of amphotericin B (0.5 mg/kg of body weight daily). During his course of treatment, the patient remained afebrile, with no evidence of deep-seated infection. Amphotericin B was discontinued after two other sets of blood cultures were negative. A cumulative dose of 500 mg of amphotericin B was administered. The patient was discharged.

Mycological study and diagnosis. Isolates from different bottles were cultured on potato dextrose agar and oatmeal agar at 25°C in the dark. Colonies on oatmeal agar attained a diameter of 58 to 60 mm after 7 days. They were flat and white, with sparse aerial mycelium. On potato dextrose agar over the same incubation period, the colonies reached 57 to 60 mm in diameter and were densely cottony, white at first but soon becoming pastel red at the center and with whitish aerial mycelium and dark violet substrate mycelium towards the edges. The reverse was brownish red to violet brown. The isolates did not develop macroconidia in any medium, but microconidia were abundant. They were produced in false heads from prostrate conidiophores with mono- and polyphialides (Fig. 1) which measured 10 to 23 µm by 2.8 to 4 µm. Microconidia were oval, ellipsoidal, more or less cylindrical or allantoid, and commonly aseptate, measuring 5 to 11 µm by 2 to 3.5 µm (Fig. 1B and C), or very rarely septate (one to two septa), measuring 11 to 14 µm by 2.8 to 4 µm. A representative isolate of the strain is maintained in the mycology laboratory at the Faculty of Medicine in Reus, University Rovira i Virgili, Tarragona, Spain, as FMR 6487. 

View larger version (89K): [in this window] [in a new window]   FIG. 1.   Fusarium sacchari FMR 6487. (A) Polyphialide; (B and C) microconidia and mono- and polyphialides. Magnification by Nomarski optics, ×1,600.

Antifungal susceptibility testing. The strain was tested to determine its susceptibility to six antifungal drugs (amphotericin B, itraconazole, miconazole, fluconazole, ketoconazole, and flucytosine) (Table 1). As all the isolates showed the same growth pattern, very similar colonies, and practically identical microscopic features, only one isolate was tested. Tests were carried out by a previously described microdilution method (10), mainly according to the guidelines for yeast of the National Committee for Clinical Laboratory Standards by using RPMI 1640 medium (buffered to pH 7.0 with 0.165 M morpholinepropanesulfonic acid), an inoculum of 1.1 × 10⁶ CFU/ml, an incubation temperature of 30°C, a second-day reading (48 h), and an additive drug dilution procedure. Three different criteria were used to define the MIC: (i) the lowest drug concentration that showed prominent (approximately 50%) growth inhibition, (ii) the lowest drug concentration that matched a 75% inhibition standard, and (iii) the lowest concentration at which no growth occurred. To determine the minimum fungicidal concentration (MFC), 10 µl from each of the wells at or above the MIC was plated on Sabouraud glucose agar. The plates were incubated at 25°C for 72 h. The MFC was defined as the lowest drug concentration at which no colonies developed on the agar plate.