Pseudoclavibacter-like subcutaneous infection: a case report
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Arthrobacter-like organisms, including Pseudoclavibacter organisms, have rarely been documented as being responsible for infection in humans.
An 81-year-old French man developed a subcutaneous infection despite antibiotic treatment combining clindamycin and metronidazole for chronic wound infection. A skin biopsy showed numerous polymorphonuclear cells and no bacteria, but a subcutaneous swab yielded numerous polymorphonuclear cells, a few Gram-positive cocci, Gram-negative cocci, and Gram-positive rods. The Gram-positive rod sequence exhibited 99% sequence similarity with uncultured Pseudoclavibacter sp. [GenBank:EF419350] and 99% sequence similarity with uncultured Pseudoclavibacter sp. [GenBank:EF419347]. The genetic data and unique peptide profile of this Pseudoclavibacter-like isolate, determined by matrix-assisted laser desorption ionization-time of flight mass spectrometry, underscored its uniqueness.
Pseudoclavibacter-like organisms are identifiable in cutaneous and subcutaneous infections in humans.
KeywordsPseudoclavibacter 16S rRNA gene MALDI-TOF identification skin infection
Pseudoclavibacter is an emerging bacterial genus created a few years ago to accommodate environmental Brevibacterium organisms . Indeed, Arthrobacter-like bacteria have rarely been isolated in patients, and a Pseudoclavibacter organism has been reported to be isolated only once, from an aortic valve of a 74-year-old man .
Identification of the isolate was made possible only after 16S rRNA gene sequence analysis, as the isolate was not reactive on identification strips and did not exhibit any identifying phenotype. The 16S rRNA gene sequence comparison indicated that this isolate is representative of a previously uncultured organism. This case illustrates a new paradigm in using 16S rRNA gene sequence-based identification of organisms in clinical microbiology laboratories. Indeed, most of the emerging bacteria have been described previously on the basis of an original bacterial isolate exhibiting a 16S rRNA gene sequence with < 98.7% sequence similarity with any other sequence [4, 6, 7]. In our case report, however, the 16S rRNA gene sequence was already available in GenBank before we recovered the isolate. Indeed, extensive genomic and metagenomic explorations of complex environmental and mucosa-associated flora yielded a tremendous amount of the original 16S rRNA gene sequence from as-yet-uncultured organisms [8, 9]. In our case report, isolation of an organism exhibiting a 16S rRNA gene sequence identical to that of a previously uncultured organism underscores the uniqueness of this isolate.
In the case of our patient, the Pseudoclavibacter-like organism was most probably involved in his clinical infection, since this Gram-positive rod was observed in the presence of pus during the direct examination of a subcutaneous specimen. It grew in pure culture from a patient who was taking two antibiotics to which the Pseudoclavibacter-like organism was found to be resistant, thus supporting the hypothesis that growth of the Pseudoclavibacter-like organism was indeed selected by the antibiotic treatment. Also, Pseudoclavibacter sp. and other Arthrobacter-like organisms have never been reported as potential contaminants of culture, and Pseudoclavibacter spp. have not been isolated in our laboratory, with the exception of this patient. The 16S rRNA gene sequence of identical Pseudoclavibacter-like organisms was found in the diseased skin of patients with psoriasis before we obtained the first isolate . This fact and the data presented in this case report suggest that Pseudoclavibacter-like organisms are organisms involved in skin diseases. Pseudoclavibacter-like organisms are bacterial organisms identifiable in cutaneous and subcutaneous infections in humans on the basis of a unique peptide profile obtained by MALDI-TOF analysis and unique 16S rRNA gene sequencing.
Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
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