Chapter 49 - Aeromonas

Abstract

The genus Aeromonas covers a diverse group of gram-negative, nonspore-forming, facultatively anaerobic, rod-shaped bacilli that commonly occur in aquatic and terrestrial environments as well as aquatic animals, birds, and humans. Of the 36 Aeromonas species identified to date, 19 are implicated in human illnesses, and four (Aeromonas caviae, Aeromonas dhakensis, Aeromonas veronii, and Aeromonas hydrophila) are responsible for up to 96.5% of clinical isolations. Depending on the immune status of affected individuals, human aeromoniasis may present as gastroenteritis, wound, and soft tissue infections, bacteremia and sepsis, and other diseases (pneumonia, peritonitis, and meningitis). Mechanistically, aeromonads employ certain structural components (e.g., flagella, pili/fimbriae, capsule, S-layer, lipopolysaccharides, and outer membrane proteins) for motility, adherence, colonization, and evasion of host defense; and secrete a large number of toxins, enzymes, and other proteins for invasion and sabotage of host immune attack. Diagnosis of human aeromoniasis involves phenotypic and genotypic techniques, and its treatment is currently based on antibiotic therapy. With antimicrobial resistance becoming an increasingly important issue, there is urgency to find novel therapeutics for Aeromonas spp. Improving our understanding on the molecular mechanisms of Aeromonas infection through the application of omics approaches is thus critical in helping realize this goal. We update knowledge of new Aeromonas species, Aeromonas species in human illnesses, diagnosis methods of matrix-assisted laser desorption/ionization time of flight mass spectrometry, and antimicrobial profiles of Aeromonas.