Polyphasic Characterisation of Cedecea colo sp. nov., a New Enteric Bacterium Isolated from the Koala Hindgut

Abstract

The Cedecea genus is comprised of six rarely isolated species within the Enterobacteriaceae family. Representatives are Gram-negative motile bacilli, and are typically oxidase-negative, lipase-positive and resistant to colistin and cephalothin. In this study, a putative novel Cedecea species (designated strain ZA_0188T), isolated from the koala hindgut, was characterised using a polyphasic taxonomic approach. Maximum average nucleotide identity (ANI) and 16S ribosomal RNA (rRNA) similarity scores well below thresholds of species demarcation were reported, at 81.1% and 97.9%, respectively. Multilocus phylogenetic analysis indicated strain ZA_0188T was most similar to but divergent from recognised Cedecea species. The isolate’s genomic G+C content was determined as 53.0 mol%, >1% lower than previously reported in Cedecea. Phenotypically, strain ZA_0188T was distinct from recognised Cedecea species such as colistin- and cephalothin-sensitive, lipase-, sorbitol-, sucrose-, and Voges-Proskauer-negative, and melibiose-, arabinose-, arginine-, and rhamnose-positive. In preliminary experiments, strain ZA_0188T exhibited cellulase activity and high-level tolerance to eucalyptus oil compared to other enteric species surveyed. Collectively, these findings suggest that strain ZA_0188T represents a novel enteric species, for which the name Cedecea colo is proposed.

Refractory otitis media and otitis externa in a koala (Phascolarctos cinereus) treated with total ear canal ablation and lateral bulla osteotomy

“…Y. regensburgei has recently been identified as a novel pathogen in farmed American alligators (Alligator mississippiensis), causing acute mortality secondary to pneumonia and septicaemia. 30 The 16S rRNA gene sequence of Y. regensburgei is closely related to the bacteria Siccibacter turicensis, a normal component of the wild kangaroo gut microbiota responsible for cellulose degradation 31 ; however, while other members of the Enterbacteriaceae family have been routinely identified in the hindgut and pouch of the koala, and are able to withstand high concentrations of eucalyptus oil compared with other enteric bacteria, 32 Y. regensburgei has not previously been cultured and is unlikely to be a normal commensal organism in this species (personal communications: Professor I Macreadie via email 23 June 2020; Professor K Belov via email 26 June 2020). To the authors' knowledge, this report of Y. regensburgei otitis media combined with otitis externa in a koala represents the first clinical infection described in the literature outside of humans and alligators.…”

Siccibacter turicensis from Kangaroo Scats: Possible Implication in Cellulose Digestion

“…Cells for matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectroscopy (MS) analysis were prepared and analysed using a Bruker Biotyper (Preston, Vic., Australia) [ 15 ]. The S. turicensis mass spectrum was added to the RMIT University Bruker library for rapid identification of S. turicensis .…”

Expanding spectrum of opportunistic Cedecea infections: Current clinical status and multidrug resistance

“…Environmental sources of Cedecea constituting potential reservoirs for infection are numerous. Similar to other genera in the Enterobacteriaceae family, Cedecea species have been detected in diverse ecological niches, including aquatic habitats (Chun et al, 2017;Chan and Tan, 2017), soil or agricultural dusts (Pande et al, 2000), plants (Akinsanya et al, 2015), retail food (Chan et al, 2014;Ye et al, 2017), insect vectors (Hegde et al, 2019;Mitri et al, 2020), human gut microbiome (Human Microbiome Project Consortium, 2012), and non-human animals (Boath et al, 2020;Kateete et al, 2013). In a case of leg ulcer infection and bacteremia, Dalamaga et al (2008b) speculated that transmission of the C. davisae pathogen occurred from direct exposure of the patient's minor leg lesion with lake water prior to hospitalization.…”