Biofilms and Coronavirus Reservoirs: a Perspective Review.

Bats are a key reservoir of coronaviruses (CoVs), including the agent of the severe acute respiratory syndrome, SARS-CoV-2, responsible for the recent deadly viral pneumonia pandemic. However, understanding how bats can harbor several microorganisms without developing illnesses is still a matter under discussion. Viruses and other pathogens are often studied as stand-alone entities, despite that, in nature, they mostly live in multispecies associations called biofilms-both externally and within the host. Microorganisms in biofilms are enclosed by an extracellular matrix that confers protection and improves survival. Previous studies have shown that viruses can secondarily colonize preexisting biofilms, and viral biofilms have also been described. In this review, we raise the perspective that CoVs can persistently infect bats due to their association with biofilm structures. This phenomenon potentially provides an optimal environment for nonpathogenic and well-adapted viruses to interact with the host, as well as for viral recombination. Biofilms can also enhance virion viability in extracellular environments, such as on fomites and in aquatic sediments, allowing viral persistence and dissemination. Moreover, understanding the biofilm lifestyle of CoVs in reservoirs might contribute to explaining several burning questions as to persistence and transmissibility of highly pathogenic emerging CoVs.

Pseudonajide peptide derived from snake venom alters cell envelope integrity interfering on biofilm formation in Staphylococcus epidermidis.

BACKGROUND: The increase in bacterial resistance phenotype cases is a global health problem. New strategies must be explored by the scientific community in order to create new treatment alternatives. Animal venoms are a good source for antimicrobial peptides (AMPs), which are excellent candidates for new antimicrobial drug development. Cathelicidin-related antimicrobial peptides (CRAMPs) from snake venoms have been studied as a model for the design of new antimicrobial pharmaceuticals against bacterial infections. RESULTS: In this study we present an 11 amino acid-long peptide, named pseudonajide, which is derived from a Pseudonaja textilis venom peptide and has antimicrobial and antibiofilm activity against Staphylococcus epidermidis. Pseudonajide was selected based on the sequence alignments of various snake venom peptides that displayed activity against bacteria. Antibiofilm activity assays with pseudonajide concentrations ranging from 3.12 to 100 µM showed that the lowest concentration to inhibit biofilm formation was 25 µM. Microscopy analysis demonstrated that pseudonajide interacts with the bacterial cell envelope, disrupting the cell walls and membranes, leading to morphological defects in prokaryotes. CONCLUSIONS: Our results suggest that pseudonajide's positives charges interact with negatively charged cell wall components of S. epidermidis, leading to cell damage and inhibiting biofilm formation.

Peptides as a strategy against biofilm-forming microorganisms: Structure-activity relationship perspectives.

Biofilm forming microorganisms substantially enhance their virulence and drug resistance causing and alternatives are need to combat this health problem. In this context, peptides are an exceptional strategy in drug design and pharmaceutical innovation due to their diverse chemical features, biological activity and biotechnological relevance. Therefore, this study proposes a comprehensive assessment of a wide range of peptides, targeting biofilms. It provides chemical and molecular information and a Structural Activity Relationship perspective in order to delineate minimal requirements for antibiofilm activity and contributing to the development of new antibiofilm agents. In light of this, it was possible to propose a peptide design model (X1-X2-X3-X4-X5-X6-X7-X8-X9-X10-X11-X12-X13-X14-X15-X16-X17-X18-X19-X20) to be tested in the war against resistant microorganisms.

Toxicological evaluation of Pterocaulon polystachyum extract: a medicinal plant with antifungal activity.

Pterocaulon polystachyum DC is a native species to southern Brazil, Paraguay, Uruguay and northeastern Argentina. It is utilized to treat animal problems popularly diagnosed as "mycoses". The antifungal and amebicidal activity of its hexane extract has been previously reported, although there are no studies confirming the safety of this plant for therapeutic purposes to date. Hence, this study investigates the toxic effects of a hexane extract of Pterocaulon polystachyum administered as acute and subacute oral treatments. After acute treatment the extract caused alterations in biochemical parameters, morphological alterations in tissues and was genotoxic, according to the comet assay; neither mortality nor visible signs of lethality were seen in mice. Similarly subacute treatment caused important differences in biochemical parameters and tissues, between control and treated groups. The results also revealed genotoxicity in kidney tissue, though no mutagenicity was detected by the micronucleus test. No animal died during the treatment period.

Neurobehavioral and genotoxic parameters of duloxetine in mice using the inhibitory avoidance task and comet assay as experimental models.

Duloxetine is a potent inhibitor of serotonin and noradrenaline reuptake, with weak effects on dopamine reuptake, used in the treatment of major depression. It has been recognized that some antidepressants can affect memory in humans, but there is not study that report the duloxetine effect on memory using the inhibitory avoidance. The aim of this work was to investigate the effect of duloxetine on short- and long-term memory (STM and LTM) in the inhibitory avoidance task in mice. Duloxetine (10 and 20 mg/kg; i.p.) administered before or after the inhibitory avoidance training was not able to produce effects on STM e LTM (p>0.05). The group that received MK-801 (0.0625 mg/kg), an NMDA receptor antagonist, showed an impairment in STM and LTM (p<0.01). These effects were not reversed by duloxetine administration (p=0.114 and p=0.06, respectively). Duloxetine effect on memory 5 days after i.p. administration was also investigated. After this treatment both duloxetine doses used were unable to affect STM or LTM in the inhibitory avoidance task (p=0.371 and p=0.807, respectively). DNA damages were evaluated in brain tissues and blood by the comet assay, after subacute treatment (10 or 20 mg/kg by 5 days). Duloxetine did not induce genotoxic effects. However, when the cells were treated ex vivo hydrogen peroxide, a pro-oxidant effect on brain tissue from treated animals was observed with significantly higher DNA damage in comparison to untreated animals, suggesting increased susceptibility to injuries by reactive oxygen species in brain after treatment with duloxetine. Duloxetine did not produce any effect on memory after acute and subacute administration, suggesting that this antidepressant does not affect either memory acquisition or consolidation.