Hadjilouka Agni, Paramithiotis Spiros, Drosinos Eleftherios H
Laboratory of Food Quality Control and Hygiene, Department of Food Science and Human Nutrition, Agricultural University of Athens, Iera Odos 75, 118 55, Athens, Greece.
Curr Microbiol. 2018 Jul;75(7):857-865. doi: 10.1007/s00284-018-1458-4. Epub 2018 Feb 21.
The aim of the present study was to apply descriptive, phylogenetic, recombination, and selection analyses on alignments of the Listeria Pathogenicity Island 1 (LIPI-1) of 1/2a and 4b Listeria monocytogenes isolates of different origin in order to gain insights into the evolution of this virulence gene cluster. For that purpose, a total of 19 L. monocytogenes isolates (9 meat isolates, serotype 1/2a; 5 meat isolates, serotype 4b; 5 strawberry isolates, serotype 4b) that have been previously separated at strain level were subjected to sequencing of their LIPI-1. Descriptive analysis revealed extensive nucleotide diversity mostly in the intragenic regions. The actA gene of 1/2a and 4b meat isolates and the hly gene of the 4b strawberry isolates exhibited the higher diversity; limited diversity was observed in prfA and plcA genes of the 4b isolates and mpl gene of the 1/2a isolates. Phylogenetic analysis of the complete island resulted in two major clusters that were consistent with serotype assignment of the isolates. Moreover, effective discrimination between serotypes was obtained by plcA, plcB, mpl, actA and the intergenic regions plcA-prfA and plcA-hly. In all cases but plcB and plcA-prfA 4b isolates were also differentiated according to their source of isolation as well. Selection analysis revealed that the island consisted of randomly evolving DNA with the exception of prfA gene of 1/2a isolates and actA gene of 4b meat isolates for which purifying selection or population expansion was indicated. Finally, no statistically significant evidence for recombination has been observed.
本研究的目的是对不同来源的1/2a和4b型单核细胞增生李斯特菌分离株的李斯特菌致病岛1（LIPI-1）序列进行描述性、系统发育、重组和选择分析，以便深入了解这个毒力基因簇的进化。为此，对之前已在菌株水平分离的总共19株单核细胞增生李斯特菌（9株肉类分离株，血清型1/2a；5株肉类分离株，血清型4b；5株草莓分离株，血清型4b）进行了LIPI-1测序。描述性分析显示，大部分核苷酸多样性存在于基因内区域。1/2a和4b型肉类分离株的actA基因以及4b型草莓分离株的hly基因表现出较高的多样性；在4b型分离株的prfA和plcA基因以及1/2a型分离株的mpl基因中观察到有限的多样性。对整个致病岛的系统发育分析产生了两个主要簇，这与分离株的血清型分类一致。此外，通过plcA、plcB、mpl、actA以及基因间区域plcA-prfA和plcA-hly能够有效区分血清型。在所有情况下，除了plcB和plcA-prfA外，4b型分离株也可根据其分离来源进行区分。选择分析表明，除了1/2a型分离株的prfA基因和4b型肉类分离株的actA基因显示出纯化选择或群体扩张外，该致病岛由随机进化的DNA组成。最后，未观察到统计学上显著的重组证据。
