A comparative study of clinical Aeromonas dhakensis and Aeromonas hydrophila isolates in southern Taiwan: A. dhakensis is more predominant and virulent

Abstract

Aeromonas dhakensis, often phenotypically identified as Aeromonas hydrophila, is an important human pathogen. The present study aimed to compare the clinical and biological features of A. dhakensis and A. hydrophila isolates from human wounds. A total of 80 Aeromonas wound isolates collected between January 2004 and April 2011 were analysed. The species was identified by the DNA sequence matching of rpoD and gyrB (or rpoB if necessary). Most of the Aeromonas isolates were identified as A. dhakensis (37, 46.3%), and 13 (16.3%) as A. hydrophila. Both species alone can cause severe skin and soft-tissue infections. More A. dhakensis isolates were found in wounds exposed to environmental water (32.4% vs 0%, p 0.042). More biofilm formation was noted among A. dhakensis isolates (mean optical density at 570 nm, 1.23 ± 0.09 vs 0.78 ± 0.21, p 0.03). The MICs of ceftriaxone, imipenem and gentamicin for A. dhakensis isolates were higher (p <0.0001, <0.04, and <0.01, respectively). The survival rates of Caenorhabditis elegans co-incubated with A. dhakensis from day 1 to day 3 were lower than those of worms infected with A. hydrophila in liquid toxicity assays (all p values <0.01). Isolates of A. dhakensis exhibited more cytotoxicity, as measured by the released leucocyte lactate dehydrogenase levels in human normal skin fibroblast cell lines (29.6 ± 1.2% vs 20.6 ± 0.6%, p <0.0001). The cytotoxin gene ast was primarily present in A. hydrophila isolates (100% vs 2.7%, p <0.0001). In summary, A. dhakensis is the predominant species among Aeromonas wound isolates, and more virulent than A. hydrophila.

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.…”

“…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…”

“…in human clinical and environmental isolates in Australia, Taiwan and Malaysia (Aravena-Roman et al 2011, Puthucheary et al 2012, Chen et al 2013, Figueras & Beaz-Hidalgo 2015. This study indicates another potential host for A. dhakensis, now considered the second-most prevalent Aeromonas pathogenic species in humans after A. ca viae and before A. veronii (Figueras & Beaz-Hidalgo 2015), and an emerging pathogen in freshwater fish (Orozova et al 2009, Esteve et al 2012, Soto-Rodriguez et al 2013.…”

“…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

“…dhakensis and A. aquariorum represented the same taxon (11,12). Although accurate identification of Aeromonas species could be achieved using the nucleotide sequences of housekeeping genes (7,10), these molecular methods are labor-intensive and timeconsuming. Recently, several studies have shown that the matrixassisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) can rapidly and accurately identify different Aeromonas species (13)(14)(15).…”