AUTHOR=Huang Li , Wang Mingshu , Mo Ting , Liu Mafeng , Biville Francis , Zhu Dekang , Jia Renyong , Chen Shun , Zhao Xinxin , Yang Qiao , Wu Ying , Zhang Shaqiu , Huang Juan , Tian Bin , Liu Yunya , Zhang Ling , Yu Yanling , Pan Leichang , Rehman Mujeeb Ur , Chen Xiaoyue , Cheng Anchun 

TITLE=Role of LptD in Resistance to Glutaraldehyde and Pathogenicity in Riemerella anatipestifer

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.01443

DOI=10.3389/fmicb.2019.01443

ISSN=1664-302X

ABSTRACT=<p><italic>Riemerella anatipestifer</italic> is a gram-negative bacterium that causes disease in ducks and other birds. Despite being an important pathogen in poultry, the pathogenesis and drug resistance mechanisms of this bacterium are poorly understood. An analysis of our unpublished RNA-Seq data showed that <italic>lptD</italic>, a gene encoding one of the lipopolysaccharide transport components, is transcribed at higher levels in strain CH-1 than in strain ATCC11845. In addition, strain CH-1 has been shown to display broader drug resistance than strain ATCC11845. Since LptD is involved in LPS biogenesis and drug resistance, we wondered if <italic>lptD</italic> is associated with increased <italic>R. anatipestifer</italic> resistance to glutaraldehyde, a disinfectant used in the production industry. In this study, the minimal inhibitory concentration (MIC) of glutaraldehyde for strain CH-1 was determined to be 0.125% (vol/vol), whereas an MIC of 0.05% (vol/vol) was observed for strain ATCC11845. Furthermore, the level of <italic>lptD</italic> transcription in strain CH-1 was consistently 2-fold higher than that observed in strain ATCC11845. Moreover, <italic>lptD</italic> transcription was upregulated in both strains at a subinhibitory concentration of glutaraldehyde. The role of <italic>lptD</italic> in <italic>R. anatipestifer</italic> was further assessed by constructing an ATCC11845 mutant strain with low <italic>lptD</italic> expression, <italic>R. anatipestifer</italic> ATCC11845 <italic>lptD</italic><sup>−</sup>. The growth of <italic>R. anatipestifer</italic> ATCC11845 <italic>lptD</italic><sup>−</sup> was severely impaired, and this strain was more susceptible than the wild-type strain to glutaraldehyde. Moreover, compared to the wild-type strain, <italic>R. anatipestifer</italic> ATCC11845 <italic>lptD</italic><sup>−</sup> exhibited decreased biofilm formation and was more sensitive to duck serum. Finally, low <italic>lptD</italic> expression led to decreased colonization in ducklings. These results suggest that LptD is involved in <italic>R. anatipestifer</italic> glutaraldehyde resistance and pathogenicity.</p>