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

Clin Microbiol Infect. 2014 Jul;20(7):O428-34. doi: 10.1111/1469-0691.12456. Epub 2013 Dec 16.

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.

Keywords: Aeromonas dhakensis; Aeromonas hydrophila; Caenorhabditis elegans; antimicrobial susceptibility; biofilm; cytotoxicity.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aeromonas / classification*
  • Aeromonas / isolation & purification*
  • Aeromonas / pathogenicity
  • Aeromonas / physiology
  • Aged
  • Animals
  • Anti-Bacterial Agents / pharmacology
  • Biofilms / growth & development
  • Caenorhabditis elegans / microbiology
  • Caenorhabditis elegans / physiology
  • Ceftriaxone / pharmacology
  • Cell Survival
  • DNA Gyrase / genetics
  • DNA-Directed RNA Polymerases / genetics
  • Female
  • Fibroblasts / microbiology
  • Fibroblasts / physiology
  • Gentamicins / pharmacology
  • Gram-Negative Bacterial Infections / epidemiology*
  • Gram-Negative Bacterial Infections / microbiology*
  • Humans
  • Imipenem / pharmacology
  • Male
  • Microbial Sensitivity Tests
  • Middle Aged
  • Molecular Sequence Data
  • Prevalence
  • Sequence Analysis, DNA
  • Soft Tissue Infections / epidemiology
  • Soft Tissue Infections / microbiology
  • Survival Analysis
  • Taiwan / epidemiology
  • Wound Infection / epidemiology
  • Wound Infection / microbiology

Substances

  • Anti-Bacterial Agents
  • Gentamicins
  • Imipenem
  • Ceftriaxone
  • DNA-Directed RNA Polymerases
  • DNA Gyrase

Associated data

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