Antimicrobial peptide production in response to gut microbiota imbalance.

The gut microbiota presents essential functions in the immune response. The gut epithelium acts as a protective barrier and, therefore, can produce several antimicrobial peptides (AMPs) that can act against pathogenic microorganisms, including bacteria. Several factors cause a disturbance in gut microbiota, including the exacerbated and erroneous use of antibiotics. Antibiotic therapy has been closely related to bacterial resistance and is also correlated with undesired side-effects to the host, including the eradication of commensal bacteria. Consequently, this results in gut microbiota imbalance and inflammatory bowel diseases (IBD) development. In this context, AMPs in the gut epithelium play a restructuring role for gut microbiota. Some naturally occurring AMPs are selective for pathogenic bacteria, thus preserving the health microbiota. Therefore, AMPs produced by the host's epithelial cells represent effective molecules in treating gut bacterial infections. Bearing this in mind, this review focused on describing the importance of the host's AMPs in gut microbiota modulation and their role as anti-infective agents against pathogenic bacteria.

Promising strategies for future treatment of Klebsiella pneumoniae biofilms.

Klebsiella pneumoniae is a Gram-negative pathogenic bacterium that has the ability to aggregate as biofilm, representing one of the main agents in hospital infections, showing high rates of resistance to antibiotics. The K. pneumoniae biofilm aggregates are composed mainly of extracellular polysaccharides, eDNA and proteins. Besides, biofilms can attach to medical devices, such as endotracheal tubes and catheters, but are most dangerous on body surfaces. Here, we discuss the recent findings about the resistance mechanisms of K. pneumoniae biofilms, including genes and protein involved in 'classic', multidrug-resistant and hypervirulent strains, and also virulence factors. In addition, we also explore new strategies for possible treatment of these biofilms, and recently discovered molecules which may lead to future treatments.

Antimicrobial and proinflammatory effects of two vipericidins.

Hospital infections allied to bacterial resistance to antibiotics have become a major worldwide problem. In this context, antimicrobial peptides (AMPs) are presented as an alternative in the control of these resistant organisms. Besides antimicrobial effects, these molecules play a crucial role in immunity by acting as immunomodulators. These peptides can activate inflammatory cells to produce pro- and anti-inflammatory mediators. In this study we will show the activity against multi-drug resistant bacteria (MDRB) of two cathelicidins from South American pit vipers Bothrops atrox and Crotalus durissus terrificus, named batroxicidin and crotalicidin. It was observed that both peptides showed activity against MDRB and presented no hemolytic or cytotoxic activity. In addition, the ability of peptides to modulate the production of cytokines TNF-α, IL-10 and IL-6 was analyzed using Raw 264.7 cells in the presence of IFN-γ stimuli, and multi-resistant E. coli and K. pneumoniae antigens. An up-expression or down-expression of TNF-α, as well as the IL-10 mediator, was observed. The cytokine IL-6, on the other hand, presented only a down-regulation for Raw 264.7 cell groups. In conclusion, the results demonstrate that both peptides presented a predominantly proinflammatory characteristic to the inflammatory mediators dosed. Overall, even presenting a proinflammatory characteristic, these peptides are still promising for future research and development of new potential antimicrobial molecules.

Anxiolytic-like effect of a novel peptide isolated from the venom of the social wasp Synoeca surinama.

Pathological anxiety is among the most common psychiatric illnesses, but current treatment is highly limited. In this study, we investigated the potential anxiolytic-like effects of a peptide isolated from Synoeca surinama venom. Rats treated with this peptide spent more time exploring the open arms of elevated plus maze, which indicates an anxiolytic-like profile for this peptide. This study is the first to show the pharmacological use of S. surinama venom in the treatment of anxiety.