Antimicrobial action of chelating agents: repercussions on the microorganism development, virulence and pathogenesis.

Infections caused by resistant microorganisms often fail to respond to conventional therapy, resulting in prolonged illness, increased treatment costs and greater risk of death. Consequently, the development of novel antimicrobial drugs is becoming more demanding every day since the existing drugs either have too many side-effects or they tend to lose effectiveness due to the selection of resistant strains. In view of these facts, a number of new strategies to obstruct vital biological processes of a microbial cell have emerged; one of these is focused on the use of metal-chelating agents, which are able to selectively disturb the essential metal metabolism of the microorganism by interfering with metal acquisition and bioavailability for crucial reactions. The chelation activity is able to inhibit the biological role of metal-dependent proteins (e.g., metalloproteases and transcription factors), disturbing the microbial cell homeostasis and culminating in the blockage of microbial nutrition, growth and development, cellular differentiation, adhesion to biotic (e.g., extracellular matrix components, cell and/or tissue) and abiotic (e.g., plastic, silicone and acrylic) structures as well as controlling the in vivo infection progression. Interestingly, chelating agents also potentiate the activity of classical antimicrobial compounds. The differences between the microorganism and host in terms of the behavior displayed in the presence of chelating agents could provide exploitable targets for the development of an effective chemotherapy for these diseases. Consequently, metal chelators represent a novel group of antimicrobial agents with potential therapeutic applications. This review will focus on the anti-fungal and anti-protozoan action of the most common chelating agents, deciphering and discussing their mode of action.

A state-trait analysis of alpha density and personality variables in a normal population.

In Study I eyes-open and eyes-closed percentage time resting alpha in normal young male adults was correlated positively with psychological test scores that reflected greater energy, feelings of confidence and control, and lesser social inhibition. Study II was consistent with Study I in that alpha density was related inversely to a projective measure of maladustment as well as measures of state and trait anxiety. The effects of visual stimulation on the size of the relationship between alpha and psychological trait measures suggested that this is a highly unstable relationship likely to appear only when experimental arrangements maximize the congruency betweey psychological states and traits. Finally, it was suggested that the application of a state-trait rationale to alpha phenomenon might be useful to organize the relationship between physiological and psychological variables and could serve as a starting point for conceptualizing the potential effects of biofeed-back applications.