AUTHOR=Gong Zelong , Shi Xiaolu , Bai Fang , He Xiaolong , Zhang Hanyun , Li Yubin , Wan Yu , Lin Yiman , Qiu Yaqun , Chen Qiongcheng , Hu Qinghua , Cao Hong 

TITLE=Characterization of a Novel Diarrheagenic Strain of Proteus mirabilis Associated With Food Poisoning in China

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.02810

DOI=10.3389/fmicb.2019.02810

ISSN=1664-302X

ABSTRACT=<p><italic>Proteus mirabilis</italic> is commonly considered to be an opportunistic pathogen causing urinary tract infections (UTIs) in humans. However, some strains of <italic>P. mirabilis</italic> were found to be associated with food poisoning outbreaks, with the pathogenic mechanism still unclear. In our study, we described a novel strain of <italic>P. mirabilis</italic> C02011 isolated from patients’ specimens in a food poisoning in China. In order to determine its gastrointestinal pathogenicity, experiments were performed to compare <italic>P. mirabilis</italic> B02005 strain (isolated from healthy people) and <italic>P. mirabilis</italic> American Type Culture Collection (ATCC) 29906 strain both <italic>in vitro</italic> [Caco-2 cells: bacterial adhesion and invasion assays, Giemsa staining, and transmission electron microscopy (TEM)] and <italic>in vivo</italic> [BALB/c mouse model: fecal character, colon injury, histological examination, immunochemistry, and western blotting (WB)]. According to the results, C02011 strain exhibited almost identical characteristics with B02005 strain in bacterial appearance and proliferation. <italic>In vitro</italic>, Caco-2 cells were infected with <italic>P. mirabilis</italic> C02011, B02005, and <italic>P. mirabilis</italic> ATCC 29906 strains. After that, Giemsa staining and TEM were used for observing the infection process of C02011 strain. Meanwhile, the adhesive abilities of different strains were rated as follows: <italic>P. mirabilis</italic> B02005 &gt; <italic>P. mirabilis</italic> C02011 &gt; <italic>P. mirabilis</italic> ATCC 29906 (<italic>P</italic> &lt; 0.01). Invasive abilities of different strains were rated as follows: <italic>P. mirabilis</italic> C02011 &gt; <italic>P. mirabilis</italic> B02005 &gt; <italic>P. mirabilis</italic> ATCC 29906 (<italic>P</italic> &lt; 0.01). <italic>In vivo</italic>, BALB/c mice were infected with <italic>P. mirabilis</italic> C02011 and B02005 strains. C02011 strain shows more virulence than B02005 strain in terms of the following indicators: (1) feces water content and fecal character; (2) colon length of mice; (3) histological examination on mouse intestine tissues; (4) ELISA for detecting TNF-α level in the colon; and (5) WB and immunohistochemistry (IHC) for detecting occludin protein expression in the colon. On the basis of these results, we firstly validated that the novel strain of <italic>P. mirabilis</italic> C02011 shows more gastrointestinal pathogenicity than the other strains isolated from a healthy individual. In addition, type IV secretion system (T4SS) was preliminarily confirmed to play an important role in the pathogenesis of diarrheal <italic>P. mirabilis</italic> isolated from the food poisoning incident.</p>