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EDIN-B (epidermal cell differentiation inhibitor-B; also termed C3Stau) is an exotoxin of Staphylococcus aureus which ADP-ribosylates and inactivates Rho GTP binding proteins. The EDIN-B gene (edin-B) and the gene for exfoliative toxin D (etd) make up the central part of a recently described pathogenicity island. Here we evaluated the prevalence and genetic organization of the edin-B/etd pathogenicity island in invasive S. aureus isolates, and characterized edin-B transcription and EDIN-B production using artificial constructs transduced in S. aureus strains RN6390 and Newman. We found that eight out of 121 (7%) S. aureus blood culture isolates harbour edin-B, which is organized in three novel variants of the original edin-B/etd pathogenicity island. In the serum of patients infected with edin-B-positive S. aureus, significant titres of anti-EDIN-B antibodies could be detected. Regulation of edin-B transcription depended on the sarA but not on the agr regulatory system. Furthermore, retrieval of EDIN-B protein secreted by S. aureus RN6390 required the presence of [alpha]2-macroglobulin to inhibit the activity of extracellular proteases. These data suggest that the EDIN-B toxin is produced during human infection, is part of a highly variable pathogenicity island and can be controlled by the sarA gene regulon and secreted bacterial proteases. DOI 10.1099/mic.0.030304-0

Pseudomonas aeruginosa PtxR enhances the expression of the exotoxin A gene toxA. The expression of ptxR itself, which occurs from two promoters (P1 and P2), is not completely understood. We have recently demonstrated that the ptxR upstream region contains potential binding sites for multiple regulators, including the virulence factor regulator Vfr. In this study, we identified within the ptxR upstream region, a 25 bp sequence to which Vfr specifically binds. The sequence is located 20-44 (32.5) bp 5' of the ptxR P2 promoter, and overlaps a potential binding site for the iron-starvation sigma factor PvdS. We also show that, throughout the growth cycle, deletion of vfr reduces ptxR expression from the P2 promoter in the P. aeruginosa strain PAO1 by four- to eightfold, but does not affect ptxR expression from P1. Further, loss of Vfr eliminates the PtxR-induced enhancement in the synthesis of exotoxin A and the metalloproteinase LasB. Our results suggest that Vfr modulates toxA and lasB expression in PAO1 through PtxR. A model defining the relationships between these different genes is presented.

Research has been conducted on Bacillus thuringiensis strains. The ability of these strains to give beta-exotoxin I has been examines via the study of their crystal toxin profiles and the role of the cry gene in beta-exotoxin I synthesis has been investigated and discussed.

Research has been conducted on the Pseudomonas aeruginosa exotoxin A. The incorporation of the tryptophan analogues into the catalytic domain of this exotoxin has been carried out and the results of the spectral analysis are described.

Research identifies a new group of Staphylococcus aureus exhibiting density-sensing agr system phenotype and its early activation in the exponential phase. Data further suggest that the new group includes most of the exfoliatin-producing strains.

Rat skeletal muscles were analyzed after the infusion of cholera toxin (CTX) and pertussis toxin (PTX) to determine the effects of the bacterial exotoxins on muscle glucose transport. Rat skeletal muscle exhibited impaired glucose transport 25 hours after the infusion of CTX and PTX. However, inhibition of insulin- and muscle contraction-mediated glucose transport was more significant after CTX infusions compared to PTX. Furthermore, CTX infusions in rat skeletal muscles increased free fatty acid and adenosine 3',5'- cyclic monophosphate.

Exotoxin A is an exoproduct of Pseudomonas aeruginosa that can form transmembrane pores in phospholipid bilayers. However, its effect on fluid reabsorption in the airspaces of the lung has not been elucidated. To determine this effect, exotoxin A was instilled in varying doses in the lung epithelium. Results showed a dose-dependent increase in the fluid transport across the lung epithelium. This uptake was shown to be dependent on the uptake of sodium across the epithelium. It is concluded that exotoxin A induces fluid removal from the air spaces by the lung epithelium.