Prevalence and molecular characteristics of Listeria monocytogenes in cooked products and its comparison with isolates from listeriosis cases / 医学前沿

This study aimed to investigate the prevalence and molecular characteristics of Listeria monocytogenes in cooked products in Zigong City, China. The overall occurrence of the L. monocytogenes in the ready-to-eat (RTE) shops and mutton restaurants surveyed was 16.2% (141/873). An occurrence of 13.5% was observed in RTE pork, 6.5% in RTE vegetables, and more than 24.0% in either cooked mutton or cooked haggis. Serotype 1/2b (45.4%), 1/2a (33.3%), and 1/2c (14.2%) were the predominant types. By comparing the clonal complexes (CCs) based on multilocus sequence typing (MLST) of the L. monocytogenes from cooked foods in Zigong City and 33 listeriosis cases from different districts of China, CC87, CC9, CC8, and CC3 were showed to be prevalent in cooked products and CC87 and CC3 were the first two frequent types in the 33 clinic-source strains. All CC87 stains harbored the newly reported Listeria pathogenicity island 4 (LIPI-4) gene fragment ptsA, and all CC3 strains possessed the Listeria pathogenicity island 3 (LIPI-3) gene fragment llsX. These may increase the occurrence of the strains belonging to CC87 and CC3 in listeriosis cases in China and also underline the risk of infection owing to the consumption of the cooked products from Zigong. ST619 (serotype 1/2b) harbored both llsX and ptsA, indicating a potential hypervirulent sequence type in Zigong.

The fecal bacterial community in diarrheal samples explored by 16S rRNA and PFGE analysis / 中国人兽共患病学报

The purpose of this research was to understand fecal micro-flora of Enterococcus-related diarrhea feces and the clone characteristics of isolated Enterococcus strains.Primer was designed according to 16S rRNA gene and integrated DNA extracted from patients' fecal samples was used as the template to amplify the conserved sequence of 16S rRNA by PCR.After the PCR product was purified and cloned into T vector to sequence,PFGE was used to analyze 20 out of 50 Enterococcus isolates from each specimen.The 16S rRNA gene sequencing analysis indicated that these 4 portions of diarrhea feces were dominated by Enterococcus faecium (>68%) and the isolates were clonal except only one portion.Although the basic flora characteristics of diarrhea feces could be revealed by 16S rRNA gene sequencing analysis and PFGE analysis,the pathogenicity and mechanism of Enterococcus were still waiting for further experimental exploration.