To the Editor: In November 2007, a 69-year-old man with fever was hospitalized at the Northern Hospital in Marseilles, France. He also had diabetes, high blood pressure, and alcohol and tobacco addictions. In September 2007, he had received a diagnosis of laryngeal cancer, which required 2 chemotherapy treatments through a central venous catheter (CVC), the second of which he had received 6 days before his November visit. Prostatic cancer, diagnosed 1.5 years earlier, had been treated by radiotherapy. At the time of the November admission, he had leukopenia (1.77 × 10⁹ leukocytes/L with 0.49 × 10⁹ polymorphonuclear cells/L) and an elevated C-reactive protein level (151 mg/L). The patient was admitted with a preliminary diagnosis of drug-induced febrile granulocytosis; the origin of his fever remained unclear. Blood for culture was first collected from a peripheral vein and on the next day was collected from a peripheral vein and from the CVC. Gram-positive rods grew in the aerobic bottle from the CVC sample. The microorganism was identified by biochemical tests using API Coryne strip (bioMérieux, Marcy-l’Etoile, France) as Rhodococcus spp. (94% similarity). The day after hospital admission, the patient was empirically treated with intravenous ticarcillin-clavulanate, 5 g 3×/day; ciprofloxacin, 200 mg 2×/day; and granulocyte colony–stimulating factor. One day later, fever resolved and the polymorphonuclear cell count was within normal limits. Oral antimicrobial drug therapy was continued for 1 week.

Bacterial identification of the strain was performed by 16S rRNA sequencing. We obtained a 1,464-bp sequence, which was found to differ at only 2 nt positions from that of Gordonia sputi (GenBank accession no. X80634). We concluded that our patient had catheter-related bacteremia caused by G. sputi because he was immunocompromised and had a CVC. We ruled out a contaminant because the organism did not belong to the normal flora of human skin and because fever resolved after treatment with antimicrobial drugs.

The genus Gordona was first described in 1971, for coryneform bacteria isolated from sputum of patients with pulmonary disease or from soil (1). It is a member of the mycolic acid–containing group consisting of genera Corynebacterium, Dietzia, Gordonia, Mycobacterium, Nocardia, Rhodococcus, and Tsukamurella. The genus has been revised several times by rearrangements with the genera Rhodococcus and Nocardia, and the name Gordona was changed to Gordonia in 1997. The genus belongs to suborder Corynebacterineae within the order Actinomycetales and currently contains 27 recognized species; only 7 have been described in human disease. Species are identified by molecular analysis.

Gordonia spp. cause a wide spectrum of disease in humans ( 2–10; Table). Neurologic and vascular infections in immunocompromised and immunocompetent patients have been reported. Cutaneous and respiratory infections, otitis externa, osteitis, and arthritis have reportedly occurred only in immunocompetent patients. Bacteria have most often been isolated from blood samples. Bacteremia has started from underlying disease such as a sequestrated lung (4) or acute cholecystis (5) or has been related to coronary artery surgery (2) and frequently to CVCs (2,3,6). Catheter removal has been recommended for treatment of Gordonia spp. infections in children (6), but the recommendation varied for adults. Six cases of infection in children have been described (6), appearing as bacteremia, ventriculitis, and brain abscess.

Microbiologic diagnosis of Gordonia spp. remains difficult. Biochemical profiles can lead to incorrect identification of isolates as Rhodococcus spp. (2,4–6,9) and sometimes Corynebacterium spp. (3) or Nocardia spp. (6). Identification at the genus and species levels is presently obtained by 16S rRNA sequence comparisons.

No recommendation for antimicrobial drug susceptibility testing has been unanimously approved, but these microorganisms seem to be susceptible to many antimicrobial drugs (6). Previous studies suggest a combination of penicillins and aminoglycosides as a suitable therapy for Gordonia-related bacteremia (3). Carbapenem or fluoroquinolone in combination with an aminoglycoside can also be used (6). Antimicrobial drug susceptibility is similar to that of Rhodococcus spp., for which Gordonia spp. are usually incorrectly identified. However, although vancomycin is often used to treat Rhodococcus spp. infections, in a previous study 11% of Gordonia spp. isolates were resistant (6). Treatment must therefore be evaluated specifically for each patient.

Gordonia spp. are environmental bacteria whose implication in human disease seems to be increasing. Phenotypic identification of bacteria included in this genus is difficult, and they are often poorly identified as Rhodococcus spp. or Corynebacterium spp. Molecular identification of Gordonia spp. by using 16S rRNA gene sequence comparison enables their characterization in human disease because the method is more accurate. The fact that these bacteria are often associated with medical devices highlights their role as nosocomial agents. Gram-positive bacilli must, therefore, not be systematically considered as contaminants, especially if associated with medical devices, and should be thoroughly identified by molecular methods in addition to biochemical tests.

Top

Related Links

• More Letter Articles