Molecular Characterization of Clinical Isolates of Aeromonas Species from Malaysia

Abstract

Background Aeromonas species are common inhabitants of aquatic environments giving rise to infections in both fish and humans. Identification of aeromonads to the species level is problematic and complex due to their phenotypic and genotypic heterogeneity. Methodology/Principal Findings Aeromonas hydrophila or Aeromonas sp were genetically re-identified using a combination of previously published methods targeting GCAT , 16S rDNA and rpoD genes. Characterization based on the genus specific GCAT -PCR showed that 94 (96%) of the 98 strains belonged to the genus Aeromonas . Considering the patterns obtained for the 94 isolates with the 16S rDNA-RFLP identification method, 3 clusters were recognised, i.e. A . caviae (61%), A. hydrophila (17%) and an unknown group (22%) with atypical RFLP restriction patterns. However, the phylogenetic tree constructed with the obtained rpoD sequences showed that 47 strains (50%) clustered with the sequence of the type strain of A. aquariorum , 18 (19%) with A. caviae , 16 (17%) with A. hydrophila , 12 (13%) with A. veronii and one strain (1%) with the type strain of A. trota . PCR investigation revealed the presence of 10 virulence genes in the 94 isolates as: lip (91%), exu (87%), ela (86%), alt (79%), se r (77%), fla (74%), aer (72%), act (43%), aexT (24%) and ast (23%). Conclusions/Significance This study emphasizes the importance of using more than one method for the correct identification of Aeromonas strains. The sequences of the rpoD gene enabled the unambiguous identication of the 94 Aeromonas isolates in accordance with results of other recent studies. Aeromonas aquariorum showed to be the most prevalent species (50%) containing an important subset of virulence genes lip/alt/ser/fla/aer . Different combinations of the virulence genes present in the isolates indicate their probable role in the pathogenesis of Aeromonas infections.

Characterization and antimicrobial susceptibility of motile aeromonads isolated from freshwater ornamental fish showing signs of septicaemia

“…However, expression of the putative virulence-associated factors in Aeromonas appears to be affected by environmental conditions (Tso & Dooley 1995, Merino et al 1998, making the detection of true virulent strains difficult. Nevertheless, screening for virulence genes has been used in many studies as a practical approach for evaluating the genetic potential of aeromonads to express virulence factors (Puthucheary et al 2012). In agreement with previ-ous studies (Nawaz et al 2010, Hu et al 2012, Yi et al 2013, we found high heterogeneity in the distribution of toxin genes among the tested isolates, with a heterogeneous distribution forming 18 different virulence gene combinations.…”

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

“…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 .…”

Complexity of β-lactamases among clinical Aeromonas isolates and its clinical implications

“…8 A. aquariorum has been associated with a wide spectrum of human diseases, such as septicemia, skin soft tissue infections, and gastroenteritis, 23 and was widely distributed in clinical and environmental specimens. 24,25 A. aquariorum and A. hydrophila subsp. dhakensis are closely related species based on a phylogenetic analysis of the gyrB, rpoD, and rpoB genes, 26,27 and an identical phenotypic profile of the inability to produce acid from L-arabinose.…”