Bacteremia Due to a Novel Microbacterium Species in a Patient with Leukemia and Description of Microbacterium paraoxydans sp. nov

Abstract

A yellow-pigmented coryneform rod was isolated from the blood of a child with acute lymphoblastic leukemia who was perfused with a central venous catheter. The culture bottles were positive twice, at a 2-month interval. The isolate was identified as a Microbacterium sp. and studied along with five other similar strains. Phenotypic, chemotaxonomic, and genetic characteristics indicated that they are closely related to Microbacterium oxydans but that they belong to a distinct species, for which the name Microbacterium paraoxydans sp. nov. is proposed. The type strain of M. paraoxydans is CF36T ‫؍‬ DSM 15019 T . The G؉C content of its DNA is 69.9 mol%. CASE REPORTA 5-year-old boy was diagnosed with acute lymphoblastic leukemia in December 1994 and included in the Fralle 93 protocol. The child achieved hematologic remission 6 weeks after induction chemotherapy was initiated. He was seen as an outpatient and responded well to treatment in the following years. However, at a March 1997 consultation, the patient had a febrile episode when being perfused with the Port-a-cath system. Clinical examination showed no septic localization. The leukocyte count was 10,860/ml, with an absolute neutrophil count of 8,850/ml. One set of blood cultures was collected from the Port-a-cath, and the aerobic bottle culture yielded yellow-pigmented colonies of gram-positive coryneform rods. The boy received ceftriaxone (1 g) intravenously once, followed by cefadroxil 500 mg twice a day for 7 days. Because of a persistent fever, cefadroxil was given for another week and immunosuppressive drugs were discontinued during the same period. The patient's history was unremarkable for the next 2 months, and no blood culture was performed when he came for his monthly visits. In June 1997, the child was presented for consultation as subfebrile and complaining of fatigue. A physical examination revealed no focus of infection, and the leukocyte count was not elevated. One set of blood cultures was taken from the Port-a-cath, and the aerobic vial revealed the same gram-positive coryneform rods, subsequently identified as Microbacterium sp. Catheter-related bacteremia was diagnosed, and the central venous catheter was removed. Ampicillin (100 mg/kg/day) was given intravenously perioperatively, with the first dose given 24 h prior to surgery. The patient's clinical condition improved rapidly afterwards. The Port-a-cath was cultured on Columbia blood agar. Within 24 h at 37°C, a pure culture of yellow-pigmented colonies of a nonfermentative, gram-positive, somewhat discolored rod had grown. Unfortunately, subcultures were lost and no further examination could be performed.The strain isolated from the patient's blood cultures, labeled CF36, was a yellow-pigmented, motile coryneform with an oxidative metabolism, proteolytic activity, and cellular fatty acids of the branched type. These general features are suggestive of the genus Microbacterium, which includes both fermentative and oxidative species, the latter formerly called Aureobacterium (13).The 16S rRN...

Interstitial pulmonary inflammation due to Microbacterium sp. after heart transplantation

“…Laboratories should always be alert to the possibility of a novel organism when different commercial or conventional systems do not agree on the identification of an isolate. Our results confirm that 16S rRNA gene sequencing provides a powerful tool for the definitive identification of clinical coryneform bacterial isolates (Funke et al, 1994;Grove et al, 1999;Laffineur et al, 2003;Lau et al, 2002;Tang et al, 2000).…”

“…Although Laffineur et al (2003) reported a Microbacterium isolate from a bronchial aspirate, to our knowledge, this is the first detailed study regarding the isolation of a Microbacterium sp. from interstitial pulmonary inflammation.…”

“…The first documented case of catheter-related Microbacterium bacteraemia was reported by Lau et al (2002). Formal identification at the species level and description of M. paraoxydans was achieved by Laffineur et al (2003) for a yellow-pigmented coryneform rod isolated from the blood of a patient with leukaemia. In almost all described Aureobacterium or Microbacterium infections, patients were immunocompromised and/or suffering debilitating diseases.…”

“…Phenotypic characteristics of the study isolate and available information for closely related Microbacterium spp. and L. aquatica (Behrendt et al, 2001;Funke et al, 1994;Grove et al, 1999;Laffineur et al, 2003;Lau et al, 2002;Nolte et al, 1996;Schumann et al, 1999) +, Positive; 2, negative; (+), delayed positive; V, variable; NA, not available; y, yellow; yw, yellow/white; GEL, gelatin; URE, urea; AES, aesculin; GLU, glucose; RIB, ribose; XYL, xylose; MAN, mannitol; MAL, maltose; LAC, lactose; SAC, sucrose; GLY, glycerol. carried out using MEGA software version 3.0 (Kumar et al, 2004), using the Kimura two-parameter model as a method of substitution and the neighbour-joining method to construct the phylogenetic tree.…”

Identification of a bacterial strain isolated from the liver of a laboratory mouse as Microbacterium paraoxydans and emended description of the species Microbacterium paraoxydans Laffineur et al 2003

“…In order to examine phenotypic congruence of our isolate C57-33 with the other six strains M. paraoxydans [25] and to identify differentiating traits these strains and type strains of related species were sujected to chemotaxonomic and physiological characterisations.…”