Auritidibacter ignavus in ear discharge of paediatric patients: Two cases reports and literature review

INTRODUCTION

The development and research of new technologies for identifying microorganisms, has allowed the identification of hitherto unknown bacteria. Auritidibacter ignavus is a newly described Gram-positive rod possibly associated with otitis, although its role as an etiologic agent in otitis is currently controversial.

METHODS

We report two cases of recurrent otitis in paediatric patients in which A. ignavus was isolated and review the previous cases reported in the literature.

RESULTS

All the isolates were identified as A. ignavus by proteomic and genomic methods. Both patients recovered from their symptoms.

CONCLUSION

A. ignavus was recovered from ear discharges of paedriatic patients with chronic ear problems. All the cases previously reported in the literature were adults. More evidence is needed for the association between A. ignavus and otitis, since data regarding this species are still scarce.

Auritidibacter ignavus, an Emerging Pathogen Associated with Chronic Ear Infections

We describe detection of the previously rarely reported gram-positive bacterium Auritidibacter ignavus in 3 cases of chronic ear infections in Germany. In all 3 cases, the patients had refractory otorrhea. Although their additional symptoms varied, all patients had an ear canal stenosis and A. ignavus detected in microbiologic swab specimens. A correct identification of A. ignavus in the clinical microbiology laboratory is hampered by the inability to identify it by using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Also, the bacterium might easily be overlooked because of its morphologic similarity to bacterial species of the resident skin flora. We conclude that a high index of suspicion is warranted to identify A. ignavus and that it should be particularly considered in patients with chronic external otitis who do not respond clinically to quinolone ear drop therapy.

2011 based on features observed from Canadian and Swiss clinical isolates and whole-genome sequencing analysis

Auritidibacter ignavus is a Gram-stain-positive bacillus derived from otorrhea. Four strains derived from ear discharges in Canada and Switzerland, with features consistent with but distinguishable from Auritidibacter ignavus IMMIB L-1656^T (accession number FN554542) by 16S rRNA gene sequencing (97.5 % similarity), were thought to represent a novel species of the genus Auritidibacter. Auritidibacter ignavus DSM 45359^T (=IMMIB L-1656^T) was acquired to compare with Canadian and Swiss strains by whole-genome sequencing (WGS). Unexpectedly, those isolates were observed to be consistent with A. ignavus DSM 45359^T by WGS (ANIb scores >98 %), MALDI-TOF (Bruker), cellular fatty acid analysis and biochemically (some differences were observed). A nearly full 16S rRNA gene sequence could not be readily prepared from A. ignavus DSM 45359^T, even after multiple attempts. A 16S rRNA gene chimeric consensus sequence created from the genome assembly of A. ignavus DSM 45359^T had only 97.5 % similarity to that of A. ignavus IMMIB L-1656^T, implying that 16S rRNA sequence accession number FN554542 could not be replicated. We concluded that our isolates of members of the genus Auritidibacter were consistent with A. ignavus DSM 45359^T, did not represent a novel species, and that the sequence corresponding to FN554542 was not reproducible. By WGS, A. ignavus DSM 45359^T had genome of 2.53×10⁶ bp with a DNA G+C content of 59.34%, while genomes of Canadian and Swiss isolates ranged from 2.47 to 2.59×10⁶ bp with DNA G+C contents of 59.3-59.52 %. A. ignavus NML 100628 (=NCTC 14178=LMG 30897) did not demonstrate a rodcoccus cycle. Emendation of Auritidibacter ignavus was proposed based on these results.