Molecular analysis of artisanal Italian cheeses reveals Enterococcus italicus sp. nov.

Abstract

The taxonomic positions of seven atypical Enterococcus strains, isolated from artisanal Italian cheeses, were investigated in a polyphasic study. By using 16S rRNA gene sequencing, DNA-DNA hybridization and intergenic transcribed spacer analysis, as well as by examining the phenotypic properties, the novel isolates were shown to constitute a novel enterococcal species. Their closest relatives are Enterococcus sulfureus and Enterococcus saccharolyticus, having a 16S rRNA gene sequence similarity of 96?7 %. This group of strains can be easily differentiated from the other Enterococcus species by DNA-DNA hybridization and by their phenotypic characteristics: the strains do not grow in 6?5 % NaCl, and they do not produce acid from L-arabinose, melezitose, melibiose, raffinose or ribose. The name Enterococcus italicus sp. nov. is proposed for this species, with strain DSM 15952 T (=LMG 22039 T ) as the type strain.Enterococci constitute a large proportion of the autochthonous bacteria associated with the mammalian gastrointestinal tract and can cause infection from this endogenous source. The incidence of infections caused by enterococci, together with the increasing difficulty of treating such infections because of multiple antibiotic resistance, put these organisms, especially Enterococcus faecium and Enterococcus faecalis, among the emerging human pathogens (Morrison et al., 1997;Robredo et al., 2000). However, enterococci are ubiquitous and can be found as free-living micro-organisms in soil, on plants and in large numbers in dairy products, where, in some cases, they predominate with respect to lactobacilli and lactococci (Franz et al., 1999;Giraffa, 2002). The presence of enterococci in dairy products has long been considered as an indicator of inadequate sanitary conditions during the production and processing of milk. In contrast, many authors suggest that enterococci may have a potentially desirable role in some cheeses, because of their proteolytic and lipolytic activities, in the development of typical flavours and for the production of enterocins with anti-Listeria activity (Ennahar & Deschamps, 2000;Giraffa et al., 1997). The important question is whether enterococci originating from food and from community sources possess an equally pathogenic potential, or whether differences in pathogenicity exists, perhaps in relation to the different species. In this context, correct species identification is of great importance to both medical and food microbiologists.Since the revival of the genus Enterococcus by Schleifer & Kilpper-Bälz (1984), phylogenetic studies have established, on the basis of 16S rRNA gene sequences, the presence of at least four 'species groups' (Devriese et al., 1993;Devriese & Pot, 1995;Stiles & Holzapfel, 1997) For these reasons, a polyphasic approach is desirable for correctly identifying 'unusual' enterococcal strains. Today, some aspects of the taxonomic and genotypic diversity within the genus Enterococcus can also be further investigated through the use of recently developed molec...

Phylogeny and Identification of Enterococci by atpA Gene Sequence Analysis

“…T and E. italicus LMG 22039 T were highly related, having about 100% 16S rRNA gene sequence similarity and an analogous atpA sequence similarity, which suggests that E. saccharominimus and E. italicus might be synonymous species (10,39 T constituted distinct branches. E. solitarius is phylogenetically more closely related to Tetragenococcus than to the other enterococci (11,20).…”

Enterococcus camelliae sp. nov., isolated from fermented tea leaves in Thailand

“…T and E. saccharolyticus ATCC 43076 T (Fortina et al, 2004 T (97.0 %) (Fortina et al, 2004). Lower sequence similarities (,97 %) were found to other described species of the genus Enterococcus (Fig.…”

“…T and E. saccharolyticus ATCC 43076 T (Fortina et al, 2004). The DNA G+C content of the strain was 37.8 mol%.…”

“…The enterococci comprise an important group of lactic acid bacteria found ubiquitously in the environment, the gastrointestinal tract, traditional fermented foods and dairy products. The classification of the genus Enterococcus has undergone considerable changes as a consequence of the increasing number of species and also improvements in methods to discriminate between species (Baele et al, 2000;Merquior et al, 1994;Naser et al, 2005 (Fortina et al, 2004), by comparison of partial sequences for three housekeeping genes, phenylalanyl-tRNA synthase a subunit (pheS), RNA polymerase a subunit (rpoA) and the a subunit of ATP synthase (atpA), and as confirmed by DNA-DNA hybridization (Naser et al, 2006). In the present paper, we describe a novel Enterococcus strain from fermented tea leaves ('miang') based on phenotypic and chemotaxonomic characteristics, DNA-DNA relatedness and 16S rRNA and rpoA gene sequence analysis.…”

Designation of the Provisional New Enterococcus Species CDC PNS-E2 as Enterococcus sanguinicola sp. nov., Isolated from Human Blood, and Identification of a Strain Previously Named Enterococcus CDC PNS-E1 as Enterococcus italicus Fortina, Ricci, Mora, and Manachini 2004

“…Overall, the results of 16S rRNA gene sequencing, SDS-PAGE analysis of WCP profiles, and DNA-DNA reassociation experiments indicated that strain ATCC BAA-780 (CDC PNS-E1) corresponds to Enterococcus italicus, a new species that was proposed to designate a group of isolates recovered from artisanal Italian cheese (4). Comparative analysis of the 16S rRNA gene sequence of our isolate ATCC BAA-780 also showed species-level similarity with the sequence of Enterococcus saccharominimus, confirming the recent finding reported by Naser et al (7) that E. italicus and E. saccharominimus (also represented by isolates obtained from dairy products) are a single species.…”