The AI-2/luxS Quorum Sensing System Affects the Growth Characteristics, Biofilm Formation, and Virulence of Haemophilus parasuis

Abstract

Haemophilus parasuis (H. parasuis) is a kind of opportunistic pathogen of the upper respiratory tract of piglets. Under certain circumstances, virulent strains can breach the mucosal barrier and enter the bloodstream, causing severe Glässer's disease. Many virulence factors are found to be related to the pathogenicity of H. parasuis strain, but the pathogenic mechanism remains unclear. LuxS/AI-2, as a kind of very important quorum sensing system, affects the growth characteristics, biofilm formation, antibiotic production, virulence, and metabolism of different strains. In order to investigate the effect of luxS/AI-2 quorum sensing system on the virulence of H. parasuis, a deletion mutant strain (ΔluxS) and complemented strain (C-luxS) were constructed and characterized. The results showed that the luxS gene participated in regulating and controlling stress resistance, biofilm formation and virulence. Compared with wild-type strain, ΔluxS strain decreased the production of AI-2 molecules and the tolerance toward oxidative stress and heat shock, and it reduced the abilities of autoagglutination, hemagglutination, and adherence, whereas it increased the abilities to form biofilm in vitro. In vivo experiments showed that ΔluxS strain attenuated its virulence about 10-folds and significantly decreased its tissue burden of bacteria in mice, compared with the wild-type strain. Taken together, the luxS/AI-2 quorum sensing system in H. parasuis not only plays an important role in growth and biofilm formation, but also affects the pathogenicity of H. parasuis.

Antivirulence properties and related mechanisms of spice essential oils: A comprehensive review

“…Anginosus , as well as acid resistance and transcription of many virulence genes in Sc. Agalactiae , are also reported to be controlled by AI‐2‐based QS, making QS inhibition an interesting antibacterial strategy (Ma et al., 2017; Wang et al., 2015; Yadav et al., 2018; Zhang et al., 2019; Zhao, Xue, Shang, Sun, & Sun, 2010). Here, we take V. harveyi as a typical example to explain this AI‐2‐based QS system (Martin‐Rodriguez et al, 2015).…”

Effect of cAMP Receptor Protein Gene on Growth Characteristics and Stress Resistance of Haemophilus parasuis Serovar 5

“…The UKD fragment obtained in this way was then inserted into a pk18mobsacB plasmid with BamHI and SalI restriction enzymes to generate the recombinant plasmid pk18crp-UKD. The recombinant plasmid was introduced into HPS5 by the nature transformation method as previously described (Zhang et al, 2012b(Zhang et al, , 2019Wang et al, 2013) with some modifications. Briefly, 20 µl of cAMP (8 mM) was added to 20 µl wild-type suspension in logarithmic phase (OD 600 value at 0.9).…”

“…Finally, the cells were incubated at 37 • C for 24-48 h. To verify the construction results of the crp mutant, the UKD sequence, kanamycin resistance cassette gene, and crp gene were amplified and then verified by sequencing. The growth characteristics of the wild-type and crp mutant strains were measured (Wang et al, 2017;Zhang et al, 2019). The wild-type and crp mutant strains were cultured in 5 ml fresh T/V/S medium overnight and then diluted with the same medium until the OD 600 value had reached 0.4.…”

“…The autoagglutination ability of HPS5 and crp was determined as described in previous studies with some modifications (Huang et al, 2016;Zhang et al, 2019). HPS5 and crp were grown in 15 ml T/V/S medium overnight and cultured to stationary phase and then transferred into 15 ml sterile tubes, and the OD 600 value was adjusted to ∼0.8.…”

“…H. parasuis could be classified into at least 15 serotypes. In general, serotypes 1, 5, 10, 12, 13, and 14 are considered as highly virulent serovars; 2, 4, and 15 as moderately virulent; with serovars 3, 6, 7, 8, 9, and 11 regarded as non-virulent (Jin et al, 2006;Zhang et al, 2019). In China, the most prevalent serotypes are serovars 4 and 5, followed by 13, 14, and 12; 12% of isolates are non-typable (Cai et al, 2005).…”