¹Haematology Department, Osmangazi University Medical School, Meselik, Eskisehir, Turkey. E-mail: melhak@hotmail.com

Chryseobacterium indologenes is a rare human pathogen although commonly found in soil, plants, foodstuffs and water sources, including those in hospitals. Formerly known as Flavobacterium indologenes, CDC group II b, it has been documented as associated with a variety of clinical infections most often in immunocompromised patients.¹ The majority of the reported cases in the literature have been from Taiwan. We describe a case of catheter-related bacteremia caused by C. indologenes during bone marrow transplantation. This is, to the best of our knowledge, the first report of a bone marrow transplant recipient developing catheter-related bacteremia due to C. indologenes outside of Asia.

A 52-year-old male patient was admitted to our institution in March 2004 with clinical signs of pancytopenia. A diagnosis of myelodysplastic syndrome (MDS, normal karyotype, subtype RAEB-T by the French–American–British Classification) was made, and induction chemotherapy was begun with cytarabine and daunorubicine. On attaining remission with this induction regimen, he received two courses of consolidation therapy; firstly with cytarabine and secondly with mitoxantrone and etoposide. The patient remained in complete remission and was discharged in August 2004.

In November 2004, he presented with fever, and bone marrow aspiration at that time revealed 64% blasts. He received reinduction therapy with cytarabine, mitoxantrone, etoposide and granulocyte colony-stimulating factor (G-CSF). He remained in complete hematological remission with this regimen and underwent bone marrow transplantation from his HLA-matched brother. The conditioning regimen of BUCY2 (Busulfan and Cytoxan) was started after a Hickman catheter was implanted. The patient had been on amphotericin B owing to previous history of mycotic infection when he developed a fever of 39°C on day 1. Empirical antimicrobial treatment was started with ceftazidime and amikacin. Fever persisted up to 3 days after the initiation of antimicrobial therapy and necessitated the addition of ciprofloxacin and vancomycin. Amikacin was discontinued. In spite of the broad antimicrobial coverage, the patient remained febrile and developed a reddened, warm, swollen appearance of the face and neck. On day 7, blood cultures taken from a vein and via a Hickman catheter grew C. indologenes. The isolate was identified by the Vitek GNI system (bioMeriux Vitek, USA). The susceptibility patterns, determined by the disc diffusion method, showed sensitivity to piperacillin/tazobactam. The organism was resistant to gentamicin, cefepime, imipenem, tobramycin, ticcarcillin and aztreonam. Antibiotic therapy was changed to piperacillin/tazobactam supplemented with ciprofloxacin, vancomycin and amphotericin B. Ceftazidime was discontinued. However, 3 days after the completion of this antimicrobial regimen, the fever persisted. In view of the diagnosis of catheter-related septicemia, the Hickman catheter was removed. The patient defervesced shortly after the removal of the catheter and remained afebrile over the next 5 days.

Thirteen days post transplant, the patient developed veno-occlusive disease and subsequently acute renal failure, necessitating hemodialysis. The patient died on day 23 post transplantation of multiorgan system failure. No autopsy was permitted.

Forty-two human infections due to C. indologenes have been reported in the English language literature to date.^{2, 3, 4, 5, 6, 7, 8} Only four of the reported cases arose outside of Asia.^{2, 5, 7, 8} The clinical symptoms included are bacteremia, keratitis and cellulitis. It is noteworthy that most of the patients were immunocompromised. Underlying factors included neoplastic diseases, diabetes mellitus, uremia and burn wound. Twenty-one of these patients had intravasculer catheter-related bacteremia.

C. indologenes is a nonfastidious, oxidase-positive, gram-negative bacillus that is not normally part of the human microflora.^{3, 9} Chryseobacterium species are typically found in soil and water. In the hospital environment, the bacterium can survive in water systems and on wet surfaces.⁴ Indwelling vascular catheters, prosthetic valves, feeding tubes and medical devices involving fluid may create potential reservoirs for chryseobacteria. Primarily opportunistic pathogenes, they infect mainly immunocompromised patients.¹⁰ We suggest that our patient acquired the infection from bathroom taps at the transplant unit as the organism also cultured from here.

C. indologenes is characterized by a limited spectrum of antimicrobial sensitivity.⁴ Resistance to a wide range of commonly used antimicrobial agents has been reported: aminoglycosides, tetracyclines, chloramphenicol, erythromycin, clindamycin and teicoplanin. However, some fluoroquinolones have shown favorable results.¹⁰ Piperacillin, cefoperazone, ceftazidime and cefepime are usually effective drugs of choice against isolates of C. ndologenes⁵ Antimicrobial susceptibility testing is important as the organism is characterized by multiple drug resistance.

It is generally accepted that indwelling catheters should be removed if the clinical symptoms do not improve despite appropriate antiobiotic treatment. However, improvement of indwelling device-related infections caused by C. indologenes without the removal of the device has been reported.⁹ The present case supports the theory that catheter-related infections caused by C. indologenes are not successfully treated while catheters remain in place but only using antiobiotics. We suggest that the possibility of persistent colonization of the implanted catheters, especially for an immunocompromised host, should alert clinicians caring for patients with these infections.

To the best of our knowledge, this is the first report of a bone marrow transplant recipient developing C. indologenes bacteremia due to the organism, outside Asia. We conclude that catheter-related bacteremia caused by C. indologenes is a clinically serious situation that requires removal of the catheter.