Biofilm formation mechanisms and targets for developing antibiofilm agents.

Biofilms are communities of microorganisms that are attached to a surface and play a significant role in the persistence of bacterial infections. Bacteria within a biofilm are several orders of magnitude more resistant to antibiotics, compared with planktonic bacteria. Thus far, no drugs are in clinical use that specifically target bacterial biofilms. This is probably because until recently the molecular details of biofilm formation were poorly understood. Bacteria integrate information from the environment, such as quorum-sensing autoinducers and nutrients, into appropriate biofilm-related gene expression, and the identity of the key players, such as cyclic dinucleotide second messengers and regulatory RNAs are beginning to be uncovered. Herein, we highlight the current understanding of the processes that lead to biofilm formation in many bacteria.

Agents that inhibit bacterial biofilm formation.

In the biofilm form, bacteria are more resistant to various antimicrobial treatments. Bacteria in a biofilm can also survive harsh conditions and withstand the host's immune system. Therefore, there is a need for new treatment options to treat biofilm-associated infections. Currently, research is focused on the development of antibiofilm agents that are nontoxic, as it is believed that such molecules will not lead to future drug resistance. In this review, we discuss recent discoveries of antibiofilm agents and different approaches to inhibit/disperse biofilms. These new antibiofilm agents, which contain moieties such as imidazole, phenols, indole, triazole, sulfide, furanone, bromopyrrole, peptides, etc. have the potential to disperse bacterial biofilms in vivo and could positively impact human medicine in the future.

Tailor-made LasR agonists modulate quorum sensing in Pseudomonas aeruginosa.

The primary quorum sensing system in the opportunistic pathogen Pseudomonas aeruginosa is regulated through the synthesis and secretion of N-3-oxo-dodecanoyl-L-homoserine lactone (C12) which binds the transcriptional activator LasR. In this study we report the design, synthesis and biological evaluation of new analogs of C12. Analysis of the autoinducer binding site cavity of LasR revealed a positively charged cavity near the center of bound C12. Accordingly, we synthesized two piperidine-C12 diastereoisomers and tested their biological activity. Both analogs proved to be strong LasR agonists that showed a synergistic effect when presented together with the natural ligand. Moreover, binding of the analogs resulted in phenotypic changes characteristic of QS controlled receptor activation.