Identification error of Aeromonas aquariorum: A causative agent of septicemia

Abstract

24A genetic re-identification of seven Aeromonas blood isolates revealed that phenotype-based 25 identification systems misidentified 5 (71.4%) isolates. In Aeromonas strains, A. aquariorum 26 was the most common misidentified-organism and showed the most potent cytotoxic 27 activities against human blood cell lines, suggesting that the correct identification of A. 28 aquariorum is important. 29 30 / 12The genus Aeromonas is comprised of oxidase-positive, glucose-fermenting, gram-negative 31 rods that are widely distributed in freshwater, estuarine and marine environments and causes 32 a variety of human illnesses such as enterocolitis and septicemia (Figueras, 2005; Janda & 33 Abbott, 2010; Morinaga, et al., 2011). We previously reported that Aeromonas septicemia 34 occurred frequently in hospitalized patients with underlying diseases including malignancy in 35 Japan (Morinaga, et al., 2011). Phenotypical differentiation of the genus Aeromonas or its 36 species has been recognized to be difficult because of the non-uniform biochemical reactions, 37and can lead to misidentification (Abbott, Cheung, & Janda, 2003; Aravena-Roman, Harnett, 38 Riley, Inglis, & Chang, 2011; Figueras, 2005; Figueras, Beaz-Hidalgo, Senderovich, Laviad, 39 & Halpern, 2011). The acid production from arabinose and the production of urocanic acid 40 and sodium dodecyl sulfate have been proposed for discriminating A. aquariorum from other 41 species (Esteve, Alcaide, & Blasco, 2012), but the molecular identification has been 42 emphasized as an alternative method for the correct identification (Figueras, Beaz-Hidalgo, 43 Collado, & Martínez-Murcia, 2011; Puthucheary, Puah, & Chua, 2012). To examine the 44 clinical importance of the correct identification, we molecularly re-identified the isolates 45 included in our previous report and evaluated the virulence genes and cytotoxicity on human 46 cell lines. 47Seven Aeromonas strains recovered from 7 cases with septicemia (one strain did not 48 regrowth) (Morinaga, et al., 2011) were re-identified by sequencing the rpoD gene using 49 4 / 12 primers and conditions previously described (Soler, et al., 2004). The sequences obtained 50 were independently aligned using Mega5 program with the sequences of the type and 51 reference strains of all members of the genus Aeromonas taken from our in-house data base 52 (A. J. Martinez-Murcia, et al., 2011). Percentage similarity was calculated using the Ez 53Taxon pairwise alignment tool (Chun, et al., 2007). Genetic distances and clustering were 54 determined using Kimura's two parameter model (Kimura, 1980) and the evolutionary tree 55 was constructed by the neighbour-joining method (Saitou & Nei, 1987) / 12The cytotoxicity was expressed as the median lethal dose (LD 50 ) of triplicate 87 experiments (Table 1)

Aeromonas dhakensis pneumonia and sepsis in a neonate Risso’s dolphin Grampus griseus from the Mediterranean Sea

“…The expected genus-characteristic resistance against ampicillin was observed for our A. dhakensis strain. Also the results obtained for the susceptibility analysis of the rest of the antimicrobials tested agreed with those reported by other authors, showing that the cephalo sporins (third and fourth generation), monobactams, carbapenems, aminoglycosides, fluoroquinolones, sulphonamides, polypeptides and amphenicols tes ted were highly effective against this microorganism (Figueras et al 2009, Esteve et al 2012, Wu et al 2012, Chen et al 2013, Morinaga et al 2013.…”

“…This bacterium was also occasionally isolated from stranded elephant seals, California sea lions and harbour seals (Thornton et al 1998). It is possible that the A. hydrophila identified phenotypically in those studies could belong, after a genetic identification, to A. dhakensis (synonym of A. aquariorum), as occurred in previous studies (Figueras et al 2009, Aravena-Román et al 2011, Morinaga et al 2013). In our case, pathologic and bac teriologic examination revealed an acute haemorrhagic-necrotizing pneumonia and sepsis associated with A. dhakensis, which was recovered in pure culture from lung, liver, spleen, kidney and blood.…”

“…In our case, pathologic and bac teriologic examination revealed an acute haemorrhagic-necrotizing pneumonia and sepsis associated with A. dhakensis, which was recovered in pure culture from lung, liver, spleen, kidney and blood. Virulence genes detected in our strain (GMV-704), like the alt, aer, lip and ser genes, have been previously recor ded with variable prevalence (27− 100%) in A. dhakensis isolates (Fi gue ras et al 2009, Puthucheary et al 2012, Chen et al 2013, Morinaga et al 2013). The fact that the A. dhakensis GMV-704 strain showed β-haemolysis on sheep blood agar and possessed the aer and lip genes implicated in the production of 72…”

“…Studies in marine mammals that use these phenotypic identification methods to characterize Aero monas isolates will probably uncover the prevalence of A. dhakensis under A. hydrophila. However, A. dhakensis can be easily recognised using molecular identification with the sequences of housekeeping genes as shown in different studies (Figueras et al 2009, Beaz-Hidalgo et al 2010, AravenaRomán et al 2011, Esteve et al 2012, Puthucheary et al 2012, Sedlá ek et al 2012, Wu et al 2012, Chen et al 2013, Morinaga et al 2013, Soto-Rodriguez et al 2013. The housekeeping genes rpoD and gyrB were shown to be very useful .…”

Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry Can Accurately Differentiate Aeromonas dhakensis from A. hydrophila, A. caviae, and A. veronii

“…Although clinical infections caused by A. dhakensis have been reported in Taiwan (7), this species have been recovered from aquatic environments and clinical samples globally (8,9). However, the prevalence of clinical infections caused by A. dhakensis is underestimated due to the possibility of this species being misidentified as A. hydrophila by the phenotype-based identification system (9,10).…”