Identification of Austwickia chelonae as cause of cutaneous granuloma in endangered crocodile lizards using metataxonomics

Haiying Jiang; Xiujuan Zhang; Linmiao Li; Jinge Ma; Nan He; Haiyang Liu; Richou Han; Huiming Li; Zhengjun Wu; Jinping Chen

doi:10.7717/peerj.6574

Identification of Austwickia chelonae as cause of cutaneous granuloma in endangered crocodile lizards using metataxonomics

PeerJ. 2019 Mar 13:7:e6574. doi: 10.7717/peerj.6574. eCollection 2019.

Authors

Haiying Jiang^{1

2

3}, Xiujuan Zhang², Linmiao Li², Jinge Ma², Nan He⁴, Haiyang Liu⁴, Richou Han², Huiming Li², Zhengjun Wu⁵, Jinping Chen²

Affiliations

¹ South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, Guangdong, China.
² Guangdong Key Laboratory of Animal Conservation and Resource Utilization, Guangdong Public Laboratory of Wild Animal Conservation and Utilization, Guangdong Institute of Applied Biological Resources, Guangzhou, Guangdong, China.
³ University of Chinese Academy of Sciences, Beijing, China.
⁴ Guangdong Luokeng Shinisaurus crocodilurus National Nature Reserve, Shaoguan, Guangdong, China.
⁵ Guangxi Key Laboratory of Rare and Endangered Animal Ecology, Guangxi Normal University, Guilin, Guangxi, China.

Abstract

The crocodile lizard (Shinisaurus crocodilurus Ahl, 1930) is an endangered reptile species, and in recent years many have died from diseases, especially the rescued and breeding individuals. However, pathogens underlying these diseases are unclear. In this study, we report our effort in rapidly identifying and isolating the pathogen that causes high mortality in crocodile lizards from Guangdong Luokeng Shinisaurus crocodilurus National Nature Reserve. The typical symptom is cutaneous granuloma in the infected crocodile lizards. Metagenomic next-generation sequencing (mNGS) is a comprehensive approach for sequence-based identification of pathogenic microbes. In this study, 16S rDNA based mNGS was used for rapid identification of pathogens, and microscopy and microbe isolation were used to confirm the results. Austwickia chelonae was identified to be the dominant pathogen in the granuloma using 16S rDNA based mNGS. Chinese skinks were used as an animal model to verify the pathogenicity of A. chelonae to fulfill Koch's postulates. As expected, subcutaneous inoculation of A. chelonae induced granulomas in the healthy Chinese skinks and the A. chelonae was re-isolated from the induced granulomas. Therefore, A. chelonae was the primary pathogen that caused this high mortality disease, cutaneous granuloma, in crocodile lizards from Guangdong Luokeng Shinisaurus crocodilurus National Nature Reserve. Antibiotics analysis demonstrated that A. chelonae was sensitive to cephalothin, minocycline and ampicillin, but not to kanamycin, gentamicin, streptomycin and clarithromycin, suggesting a possible treatment for the infected crocodile lizards. However, surgical resection of the nodules as early as possible was recommended. This study is the first report of pathogenic analysis in crocodile lizards and provides a reference for disease control and conservations of the endangered crocodile lizards and other reptiles. In addition, this study indicated that mNGS of lesions could be used to detect the pathogens in animals with benefits in speed and convenient.

Keywords: Austwickia chelonae; Dermatosis; Granuloma; Infection; Lizard; Next-generation sequencing (NGS).

Grants and funding

This project was supported by the Planning Funds of Science and Technology of Guangdong Province (2016B070701016), the Guangzhou Science Technology and Innovation Commission (201804020080), the Training Fund of Guangdong Institute of Applied Biological Resources for PhDs, Masters and Postdoctoral Researchers (GIABR-pyjj201604), the GDAS Special Project of Science and Technology Development (2019GDASYL-0105046, 2018GDASCX-0107 and 2017GDASCX-0107) and the Special Funds for Forestry Development and Protection of Guangdong Province (2017). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.