Aeromonas taiwanensis sp. nov. and Aeromonas sanarellii sp. nov., clinical species from Taiwan

Abstract

Two clinical Aeromonas strains (A2-50 T and A2-67 T ) recovered from the wounds of two patients in Taiwan could not be assigned to any known species of this genus based on their 16S rRNA gene sequences, which showed similarities of 99.6-99.8 % to those of the type strains of Aeromonas caviae, A. trota and A. aquariorum. The rpoD phylogenetic tree allocated these strains to two novel and independent phylogenetic lines, the neighbouring species being A. caviae, the type strain of which showed 93.2 % similarity (56 bp differences) to strain A2-50 T and 92.2 % (63 bp differences) to strain A2-67 T . A multilocus phylogenetic analysis of five housekeeping genes (gyrB, rpoD, recA, dnaJ and gyrA; 3684 bp) confirmed that the two strains formed independent phylogenetic lineages within the genus. These data, together with phenotypic characterization and DNA-DNA reassociation results, revealed that these strains represent novel Aeromonas species, for which the names Aeromonas taiwanensis sp. nov. (type strain A2-50 T 5CECT 7403 T 5LMG 24683 T ) and Aeromonas sanarellii sp. nov. (type strain A2-67 T 5CECT 7402 T 5LMG 24682 T ) are proposed.The genus Aeromonas includes facultatively anaerobic, Gramnegative, non-spore-forming bacilli or coccobacilli that are generally motile, usually oxidase-and catalase-positive, able to reduce nitrate to nitrite and generally resistant to the vibriostatic agent O/129 (2,4-diamino-6,7-diisopropylpteridine) (Abbott et al., 2003;Martin-Carnahan & Joseph, 2005). The genus belongs to the family Aeromonadaceae, order Aeromonadales, class Gammaproteobacteria The taxonomy of this genus is complex because, despite each species apparently having specific phenotypic characteristics, biochemical identification is laborious and very imprecise, showing poor correlation with genotypic identification (Borrell et al., 1998;Soler et al., 2003;Figueras, 2005;Ormen et al., 2005). The 16S rRNA gene sequence similarity among species of the genus is very high, ranging from 96.7 to 100 % (Martínez-Murcia et al., 1992Saavedra et al., 2006). Furthermore, this gene presents microheterogeneities Martínez-Murcia et al., 2005;Morandi et al., 2005;Alperi et al., 2008) that reduce its usefulness for identification (Alperi et al., 2008); such was the case for Aeromonas culicicola Alperi et al., 2008), now considered a synonym of A. veronii (Huys et al., 2005). However, several housekeeping genes have proven to have Abbreviation: MLPA, multilocus phylogenetic analysis.The GenBank/EMBL/DDBJ accession numbers for the 16S rRNA, gyrB, rpoD, recA, dnaJ and gyrA gene sequences of strains A2-50 T and A2-67 T are respectively FJ230077 and FJ230076, FJ807272 and FJ807277, FJ472928 and FJ472929, FJ472930 and FJ47931, FJ807270 and FJ807279 and FJ807274 and FJ807276. An unrooted 16S rRNA gene sequence-based maximum-parsimony phylogenetic tree, an unrooted MLPA minimum-evolution tree, details of differences in the 16S rRNA gene sequences of the novel strains and DNA-DNA hybridization results are available as supplementary material ...

Determination of Microbial Diversity of Aeromonas Strains on the Basis of Multilocus Sequence Typing, Phenotype, and Presence of Putative Virulence Genes

“…Recently, through an MLST approach using sequencing of five genes, several new species have been described (4,5,23); however, the numbers of isolates available for each of these new species are very limited. Coverage of all groups with a satisfactory number of isolates will be interesting and will allow a better definition of the genetic taxonomy (30).…”

The Family Aeromonadaceae

“…Subsequently, one or both of these markers have been used in support of many new species descriptions such as A. aquariorum (Martínez-Murcia et al 2008), A. tecta ), A. piscicola (Beaz-Hidalgo et al 2009), A. diversa (Miñana-Galbis et al 2010a), A. rivuli (Figueras et al 2011), A. fluvialis (Alperi et al 2010b), A. taiwanensis (Alperi et al 2010a), and A. sanarellii (Alperi et al 2010a) and to reassess the position of species with unclear or controversial phylogenetic affiliations (Saavedra et al 2006). In the slipstream of gyrB and rpoD, a series of other housekeeping genes have been proposed for phylogenetic analysis and identification of aeromonads.…”

“…In addition to phenotypic, genotypic, and/or phylogenetic evidence, all of these new descriptions incorporated DNA-DNA hybridizations to confirm the species status of the new genus members. In this way, species proposals were made for A. molluscorum (Alperi et al 2010a), and A. rivuli (Figueras et al 2011). An exception to this rule was the proposal of A. sharmana (Saha and Chakrabarti 2006), which did not include DNA-DNA hybridization values.…”

Untitled

“…They are Gram negative, short rod shape, oxidase and catalase positive, motile, facultative anaerobes, resistant to 0/129 vibriostatic agent and non-spore forming. Nineteen species of the genus have been identified till date 2, 3 .…”