Aeromonas: a book review

“Aeromonas” (Graf, 2015) is a new coming reference hardback and ebook that provides an overview on taxonomy, ecology, and pathogenicity of the genus Aeromonas, a group of bacterial species in the gamma subclass of the Proteobacteria (i.e., Gammaproteobacteria). Aeromonas is a Gram-negative, motile, and facultative anaerobic bacterium. Some of the members are associated to infections in humans, fish, and other animals, and are widespread in aquatic environments (Austin et al., 1996). The book consists of nine chapters that integrates contributions from 13 expert-scientists, under the editorship of Joerg Graf (University of Connecticut, USA) who attributes its conception and the groundwork to Amy HORNEMAN (University of Maryland, USA). The overview of the specific topics is broad while providing a concise and comprehensive text for everyone involved with Aeromonas research. The first chapter—Introduction and overview—describes the roots of research and the increasing interest of scientists in the Aeromonas field, and summarizes the chapter contents. This concisely represents an up-to-date state of the art of the covered topics that include taxonomy, fish pathogens, infections in humans, beneficial associations, antigen structures, virulence mechanisms, molecular diagnostics, and Aeromonas in food and water. Chapter two (Taxonomy) provides a more or less chronological history of the Aeromonas taxonomy and its major changes since 1891 (i.e., date of the first reference to Aeromonas-like organism in the literature) with technological advances, from DNA–DNA hybridization coupled with physiological and biotechnological characterization to fingertprinting, gene sequencing, and whole-genome sequencing analyses. This has resulted in a great expansion of the genus Aeromonas although several taxonomic controversies persist for reliable species identification. General recommendations to meet such identification is provided by the author, which is a good point of this chapter. Chapters three (Aeromonas fish pathogens) and four (Aeromonas infections in humans) are dedicated to Aeromonas diseases. The first diseases of fish are perhaps known from Aeromonas pathogens, including the two oldest known fish pathogens: the motile A. hydrophila and the non-motile A. salmonicida. By reviewing data on taxonomy, diagnosis, ecology, virulence factors, and disease control, the author of chapter three provides evidence that the number of Aeromonas fish pathogen species increases with increasing research efforts, although major gaps persist, primarily on their ecology. Chapter four weakens the controversial role of Aeromonas in causing diseases in humans. The authors further extend the Aeromonas disease range in humans, from gastroenteritis to other infections (nosocomial, bacteremia, pneumonias, and peritonitis). Chapter five (Aeromonas, a multifaceted microbe: beneficial associations with animals) is short but original compared to other single-genus book dedicated to pathogens, because it provides examples of benign or even benefial associations of Aeromonas-animal pairings, primarily the case for the digestive tract symbiosis between A. veronii and medicinal leeches, a fascinating topic. In chapter six (Aeromonas antigenic structures), an overview of the plethora of surface structures that facilitate interactions between Aeromonas and diverse hosts and evironments are elegantly given to the readers, including flagella, pili and fimbriae, lipopolysaccharide (LPS), outer membrane proteins, capsule, and the S-layer. The chapter is specifically focused on the recent findings on those external antigenic structures thought to have roles in Aeromonas pathogenesis, which offer targets for the development of vaccines. Chapter seven (New developments on the virulence mechanisms of Aeromonas hydrophila) covers new virulence factors and the relatedmolecular requirements for causing diseases, focusing primarily on the type III and IV secretion systems and the role of quorum-sensing systems in modulating Aeromonas virulence. Emphasis