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- Deciphering the Biodiversity of Listeria monocytogenes Lineage III Strains by Polyphasic Approaches
- Hanxin Zhao , Jianshun Chen , Chun Fang , Ye Xia , Changyong Cheng , Lingli Jiang , Weihuan Fang
- J. Microbiol. 2011;49(5):759-767. Published online November 9, 2011
- DOI: https://doi.org/10.1007/s12275-011-1006-4
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- 8 Scopus
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Abstract
- Listeria monocytogenes is a foodborne pathogen of humans and animals. The majority of human listeriosis cases are caused by strains of lineages I and II, while lineage III strains are rare and seldom implicated in human listeriosis. We revealed by 16S rRNA sequencing the special evolutionary status of L. monocytogenes lineage III, which falls between lineages I and II strains of L. monocytogenes and the non-pathogenic species L. innocua and L. marthii in the dendrogram. Thirteen lineage III strains were then characterized by polyphasic approaches. Biochemical reactions demonstrated 8 biotypes, internalin profiling identified 10 internalin types clustered in 4 groups, and multilocus sequence typing differentiated 12 sequence types. These typing schemes show that lineage III strains represent the most diverse population of L. monocytogenes, and comprise at least four subpopulations IIIA-1, IIIA-2, IIIB, and IIIC. The in vitro and in vivo virulence assessments showed that two lineage IIIA-2 strains had reduced pathogenicity, while the other lineage III strains had comparable virulence to lineages I and II. The IIIB strains are phylogenetically distinct from other subpopulations, providing additional evidence that this sublineage represents a novel lineage. The two biochemical reactions L-rhamnose and L-lactate alkalinization, and 10 internalins were identified as potential markers for lineage III subpopulations. This study provides new insights into the biodiversity and population structure of lineage III strains, which are important for understanding the evolution of the L. monocytogenes-L. innocua clade.
- Enterococcus faecium Isolated from Honey Synthesized Bacteriocin-Like Substances Active against Different Listeria monocytogenes Strains
- Carolina Ibarguren , Raúl R. Raya , María C. Apella , M. Carina Audisio
- J. Microbiol. 2010;48(1):44-52. Published online March 11, 2010
- DOI: https://doi.org/10.1007/s12275-009-0177-8
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- 39 Scopus
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Abstract
- Four Enterococcus faecium strains, isolated from honeycombs (C1 and M2d strains) and feral combs (Mori1 and M1b strains) secreted antimicrobial substances active against fourteen different Listeria spp. strains. The antimicrobial compound(s) present in the cell free supernatant were highly thermostable (121°C for 15 min) and inactivated by proteolytic enzymes, but not by α-amylase and lipase, thus suggesting a peptidic nature. Since the structural bacteriocin gene determinants of enterocins A and B were PCR amplified from the four E. faecium isolates, only the bacteriocin produced by strain C1 was further characterized: it showed a broad band of approximately 4.0-7.0 kDa in SDS-PAGE and was bactericidal (4 log decrease) against L. monocytogenes 99/287. L. monocytogenes 99/287R, a clone spontaneously resistant to the enterocin produced by E. avium DSMZ17511 (ex PA1), was not inhibited by the enterocin-like compounds produced by strain C1. However, it was inhibited in mixed culture fermentations by E. faecium C1 and a bacteriostatic effect was observed. The bacteriocin-producer Enterococcus strains were not haemolytic; gelatinase negative and sensitive to vancomycin and other clinically relevant antibiotics.
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