We report the first documented isolation of Wohlfahrtiimonas chitiniclastica from a human in the United States. Initially misidentified as Acinetobacter lwoffii by Vitek-2, the isolate was subsequently identified as W. chitiniclastica by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and 16S rRNA gene sequencing. While the clinical significance of the isolate in this case is unclear, it highlights the superior performance of MALDI-TOF MS for bacterial identification.
CASE REPORTA 26-year-old morbidly obese male courier worker was admitted with worsening right leg swelling and draining ulcers. He had developed lymphedema of the right leg during the preceding year after undergoing surgical correction of a right lower extremity varus deformity. A few weeks prior to the current admission, he had noticed right leg ulcers draining yellowish green serosanguineous fluid. On admission, he was afebrile and his white blood cell count was 11,100/l. He was found to have right lower extremity cellulitis.A swab was collected from the right leg and sent to the microbiology laboratory for wound cultures. The sample was inoculated onto blood, chocolate, and MacConkey agars and incubated under aerobic conditions at 37°C. Gram staining revealed many Gram-negative bacilli and moderate Gram-positive cocci. Four different organisms were isolated from the swab after growth. Microbial identification of each isolate was performed by using routine biochemical tests, including automated identification by the Vitek 2 system (bioMérieux, Marcy l'Etoile, France). The organisms were identified as Proteus vulgaris, Klebsiella pneumoniae, Acinetobacter lwoffii, and Staphylococcus aureus. The isolates were subsequently analyzed in triplicate by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) (RUO version 3.1, Bruker Biotyper; Bruker Daltonics, Bremen, Germany). Of note, the isolate identified as A. lwoffii by the Vitek 2 system was identified by MALDI-TOF MS as Wohlfahrtiimonas chitiniclastica, with identification log (score) values of 2.253, 2.296, and 2.229. Log (score)