Phenotypic diversity of Edwardsiella tarda isolated from different origins

Outer Membrane Proteins form Specific Patterns in Antibiotic-Resistant Edwardsiella tarda

Outer membrane proteins of Gram-negative bacteria play key roles in antibiotic resistance. However, it is unknown whether outer membrane proteins that respond to antibiotics behave in a specific manner. The present study specifically investigated the differentially expressed outer membrane proteins of an antibiotic-resistant bacterium, Edwardsiella tarda, a Gram-negative pathogen that can lead to unnecessary mass medication of antimicrobials and consequently resistance development in aquaculture and a spectrum of intestinal and extraintestinal diseases in humans. The comparison of a clinically isolated strain to the laboratory derived kanamycin-, tetracycline-, or chloramphenicol-resistant strains identified their respective outer membrane proteins expression patterns, which are distinct to each other. Similarly, the same approach was utilized to profile the patterns in double antibiotic-resistant bacteria. Surprisingly, one pattern is always dominant over the other as to these three antibiotics; the pattern of chloramphenicol is over tetracycline, which is over kanamycin. This type of pattern was also confirmed in clinically relevant multidrug-resistant bacteria. In addition, the presence of plasmid encoding antibiotic-resistant genes also alters the outer membrane protein profile in a similar manner. Our results demonstrate that bacteria adapt the antibiotic stress through the regulation of outer membrane proteins expression. And more importantly, different outer membrane protein profiles were required to cope with different antibiotics. This type of specific pattern provides the rationale for the development of novel strategy to design outer membrane protein arrays to identify diverse multidrug resistance profiles as biomarkers for clinical medication.

Comparative proteomic study of Edwardsiella tarda strains with different degrees of virulence

Edwardsiella tarda is an enteric opportunistic pathogen that causes a great loss in aquaculture. This species has been described as a phenotypical homogeneous group; in contrast, serological studies and molecular typing revealed a wide heterogeneity. In this work, a proteomic study of differential expression of a virulent isolate from turbot cultured in the Norwest of Spain in comparison with an avirulent collection strain was performed in order to recognize proteins involved in virulence. One hundred and three proteins that presented different abundance were successfully identified and classified into 11 functional categories according to their biological processes: amino acid, carbohydrate and lipid metabolism, tricarboxylic cycle, stress response and protein fate, protein synthesis, biogenesis of cellular components, cell rescue defence and virulence, cell membrane and transport, signal transduction and purine and pyrimidine metabolism. Twenty three protein spots detected only in turbot isolate were identified. It was shown that the same proteins appeared in different spots in the two isolates. Mass spectra obtained by MALDITOF/TOF of some of these proteins and DNA sequencing explained the changes as a result of different amino acid sequences. Several proteins related with the virulence of E. tarda (FliC, ArnA or FeSODI) were only detected in the turbot European isolate. This article is part of a Special Issue entitled: HUPO 2014.

Adhesive and invasive capacities of Edwardsiella tarda isolated from South American sea lion

Edwarsiella tarda is a zoonotic bacterium that can be isolated from humans, animals and the environment. Although E. tarda is primarily considered a fish pathogen, it is the only species of its genus considered to be pathogenic for humans as well. A survey of zoonotic intestinal bacteria in fresh feces from South American sea lions (SASL) Otaria flavescens, reported E. tarda as the most frequently isolated species. In this study, we used HEp-2 cells to establish in vitro the adherence and invasive ability of 17 E. tarda strains isolated from SASL fecal material. All the strains were able to adhere and invade HEp-2 cells with adhesion and invasion percentages ranging from 56 to 100% and 21 to 74%, respectively. Despite the expression of these pathogenic factors, further investigation is needed to determine whether this bacterium could play a role as primary pathogen for this and other species of pinnipeds.