Aeromonas | Book
"a comprehensive review" (Ringgold)
"well-written, informative" (Frontiers Microbiol.)
Caister Academic Press
Department of Molecular and Cell Biology, University of Connecticut, USA
viii + 230
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The genus Aeromonas comprises a fascinating group of organisms linked to infections in humans, fish and other animals. Members of the genus are widespread in aquatic environments and can colonize a wide variety of animals in a benign or even beneficial manner.
Dedicated to the genus Aeromonas, this book provides a comprehensive overview of current knowledge and authoritative research on the organisms, their taxonomy, ecology and pathogenicity. Written by a team of prominent scientists under the expert editorship of Joerg Graf, the topics covered include taxonomy, fish pathogens, infections in humans, beneficial associations, antigen structures, virulence mechanisms, molecular diagnostics and Aeromonas in food and water.
Packed with practical information and state-of-the-art science this concise volume is an essential handbook for everyone involved with Aeromonas research or clinical diagnosis and is a recommended purchase for all microbiology and clinical libraries.
"This book brings together experts on this genus in order to serve as a comprehensive review of the current studies pertaining to Aeromonas." from Ringgold (February 2015).
"Overall, I found the book timely ... Chapters are well-written, informative, well-referenced, and represent a valuable resource for scientist community in the Aeromonas field, including insights into relevant diagnostic methodologies. I particularly like the inclusion of chapter five on the beneficial Aeromonas-animal asssociations" from Frontiers in Microbiology (2015) 6: 1-2.
Table of contents
1. Introduction and Overview
Since its description by Kluyver and van Niel in 1936, the taxonomic structure of the genus Aeromonas has been drastically reshaped each time new technological advances were made in bacterial systematics. Modern Aeromonas taxonomy started off at the end of the 1970s essentially relying on physiological and biochemical characterization and DNA-DNA hybridizations, the latter still being considered the ‘golden standard' for delineation of bacterial species. The original ‘four-species concept' encompassing Aeromonas hydrophila, Aeromonas caviae, Aeromonas sobria and Aeromonas salmonicida was soon expanded with multiple DNA hybridization groups (HGs), most of which were later given the species status. The introduction of 16S rRNA gene sequence analysis and amplified fragment length polymorphism (AFLP) fingerprinting in the 1990s allowed to characterize the phylogenetic and genotypic diversity of larger sets of Aeromonas isolates, and facilitated the description of several new Aeromonas species or the synonymization of existing taxa. Next, the availability of bacterial whole-genome sequences allowed to evaluate single-copy protein-encoding housekeeping genes such as gyrB and rpoD as alternative molecular markers in Aeromonas taxonomy. Compared to the 16S rRNA gene, these markers display a higher taxonomic resolution and can be combined in a multi-locus sequence approach to construct a stable phylogenetic framework to rapidly and reliably recognize new Aeromonas taxa and thus avoid new nomenclatural problems.
3. Aeromonas Fish Pathogens
An increasing range of aeromonads, including A. allosaccharophila, A. bestiarum, A. caviae, A. hydrophila, A. jandaei, A. salmonicida, A. schubertii, A. sobria biovar sobria and A. veronii biovar sobria, have become associated with disease of predominantly freshwater fish in most countries. The diseases caused include fin/tail rot and generalised septicaemias often with high mortality rates. Diagnosis has progressed from phenotypic and serological approaches to molecular methods, the latter of which may be extremely sensitive and specific. Pathogenicity mechanisms include surface associated, e.g. the surface (S) layer, diffusible, e.g. proteases, and subcellular components, including lipopolysaccharide and outer membrane proteins. Disease control has progressed from use of antimicrobial compounds to include vaccines, probiotics, immunostimulants and plant products.
4. Aeromonas infections in humans
Maria José Figueras and Roxana Beaz-Hidalgo
Even though the last review about the taxonomy, pathogenicity and infections produced by Aeromonas was published fairly recently, in 2010, eight new species have since then been incorporated into the genus. Interestingly during this period the species Aeromonas dhakensis, that resulted from the reclassification of Aeromonas aquariorum and Aeromonas hydrophila subsp. dhakensis, became a relevant clinical species when sequences of housekeeping genes were used for identification. This species prevailed in Malaysia above the typical dominating clinical species Aeromonas caviae and Aeromonas veronii, or showed an almost equal frequency in Australia or Taiwan. The most frequent clinical presentation remained gastroenteritis, and arguments in favour of considering Aeromonas a true enteropathogen are provided. Other common presentations like wound and soft tissue infections have continued to be reported and seemed to prevail in European studies, while bacteraemia affecting patients that have hepatobiliary disease or cirrhosis continued to be dominating in Asia (Thailand, Taiwan etc). New cases of necrotizing fasciitis, pneumonia after near drowning and infections after leech therapy have also been reported during this period. This chapter pretends to make clinicians more familiar with the infections produced by these bacteria providing tools for their correct identification.
5. Aeromonas, a Multifaceted Microbe: Beneficial Associations with Animals
One fascinating aspect of Aeromonas spp. is that they are not only pathogens but also form commensal and beneficial associations with different animals. Indeed even one species can be found in association with a wide range of animals that are commensal, beneficial or pathogenic, which depends on the host is colonized. This diversity of associations provides an opportunity for investigating the underlying mechanisms of non-pathogenic microbe-host interactions and for gaining insights into the evolution of virulence. Among the Aeromonads, the best-studied symbiotic interaction is that of Aeromonas spp. with medicinal leeches, e.g. Hirudo verbana. Recent work has revealed that Aeromonas spp. induce the proper development of the gut in Zebrafish, which is in stark contrast to the ulcerative syndrom and other diseases in fishes and suggests the importance of the location in determining the outcome of the assocations. There is also circumstantial evidence that Aeromonas spp form non-pathogenic associations with different species of mosquitoes and also vampire bats.
6. Aeromonad Antigenic Structures
Jennifer Parker and Jonathan Shaw
Within their cell envelope bacteria of the genus Aeromonas have numerous components that help them colonize and survive within diverse environments. Both polar and lateral flagella help in the initial colonization process, with polar flagella being required in liquid surroundings and lateral flagella for the migration across and interaction with surfaces. Glycosylation of the polar flagellar filament is essential for its function, however the full biological role for this is not yet understood. Following the initial interaction with a surface through flagellar mediated motility, filamentous and non-filamentous adherence factors are employed, with the MSHA type IV pilus system playing a major role. However, in non-filamentous strains a number of outer membrane proteins have been proposed to be important in the adherence process. Following colonization, more invasive isolates of the aeromonads that are frequently isolated from cases of bacteraemia or wound infections are able to employ a series of other cell envelope factors that protect them against the host's immune response. These factors include lipopolysaccharide, capsule and the S-layer.
7. New Developments on the Virulence Mechanisms of Aeromonas hydrophila
Elena V. Kozlova, Duraisamy Ponnusamy, and Ashok K. Chopra
This chapter covers new virulence factors/mechanisms that are associated with infections caused by Aeromonas species. We focused primarily on the type 3 secretion system (T3SS) effector AexU, which has ADP-ribosyltransferase and GTPase-activating protein activities and operates by inhibiting NF-κB in the host cells. Emphasis was also placed on the T6SS and its effectors Hemolysin coregulated protein (Hcp) and Valine-glycine-repeat G (VgrG) family protein members in terms of their roles in the pathogenesis of Aeromonas infections. While Hcp inhibits bacterial phagocytosis, VgrG1 through its carboxyl-terminal vegetative insecticidal protein-2 (VIP-2) domain, leads to ADP ribosylation of host cell actin, thus preventing its polymerization and cytotoxicity in the eukaryotic cells. Finally, the role is discussed of three quorum-sensing systems (AI-1-AI-3) in modulating bacterial virulence through second messenger cyclic-diguanylate monophosphate (c-di-GMP).
8. Molecular Diagnostics by Genetic Methods
Antonio Martínez-Murcia and Brigitte Lamy
This chapter deals with most, if not all, genetic methods used for classification and molecular diagnostics of Aeromonas species. These methods include currently used strategies designed for identifying strains at the species level from pure cultures, for detection of species on complex samples, e.g. waters or food, and for genotyping strains. The genus Aeromonas represents one of the best examples to illustrate applications of molecular biology techniques in microbiology, as it early took the benefits from cutting-edge molecular biology developments to be deeply renovated and, at the same time, represents a particularly difficult example of application for molecular diagnostic microbial methods due to its complex historical taxonomy, recent changes, increasing number of new species descriptions, and their extremely close phylogenetic relationships. We have reviewed past, current and new genetic methods, aiming to give an overview and opinions about advantages and disadvantages, performance and limitations. After a brief description of the principles of the procedures, each method is illustrated by applications either in clinical diagnosis, microbial ecologic issues, epidemiologic surveys, population diversity studies, or in taxonomy rearrangements and new taxa descriptions. Present trends and future perspectives of new revolutionary technology, expected at short and medium term, are also discussed.
9. Occurrence and Virulence Potential of Aeromonas in Food and Water
Christopher J. Grim
Aeromonas is ubiquitous in surface waters. In terms of water distribution systems, elevated temperatures in surface waters lead to proliferation and regrowth of the organisms, especially in systems that are prone to biofilm development and in the extreme periphery, where free chlorine levels are low. Maintenance of chlorine levels at 0.3 mg/L or above, use of ground water sources, and biofilm and biofouling control are essential to prevent regrowth of Aeromonas in these systems. Food commodities are easily contaminated with Aeromonas, likely from exposure to contaminated water. In contrast to the seasonal distribution in surface waters, the psychrotrophic tolerance of aeromonads allows for their survival and proliferation in refrigerated foods.
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(EAN: 9781908230560 9781908230577 Subjects: [microbiology] [bacteriology] [medical microbiology] [environmental microbiology] )