Abstract
Biofilms form a complex layer with defined structures, that attach on biotic or abiotic surfaces, are tough to eradicate and tend to cause some resistance against most antibiotics. Several studies confirmed that biofilm-producing bacteria exhibit higher resistance compared to the planktonic form of the same species. Antibiotic resistance factors are well understood in planktonic bacteria which is not so in case of biofilm producing forms. This may be due to the lack of available drugs with known resistance mechanisms for biofilms. Existing antibiotics cannot eradicate most biofilms, especially of ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species). Insects produce complex and diverse set of chemicals for survival and defense. Antimicrobial peptides (AMPs), produced by most insects, generally have a broad spectrum of activity and the potential to bypass the resistance mechanisms of classical antibiotics. Besides, AMPs may well act synergistically with classical antibiotics for a double-pronged attack on infections. Thus, AMPs could be promising alternatives to overcome medically important biofilms, decrease the possibility of acquired resistance and treatment of multidrug-resistant pathogens including ESKAPE. The present review focuses on insect-derived AMPs with special reference to anti-biofilm-based strategies. It covers the AMP composition, pathways and mechanisms of action, the formation of biofilms, impact of biofilms on human diseases, current strategies as well as therapeutic options to combat biofilm with antimicrobial peptides from insects. In addition, the review also illustrates the importance of bioinformatics tools and molecular docking studies to boost the importance of select bioactive peptides those can be developed as drugs, as well as suggestions for further basic and clinical research.
Highlights
A biofilm is a layer of polymeric organic matter to which microorganisms like fungi and/or bacteria, are attached in a sessile form
Sojka et al (2016) isolated defencin-1 from A. melifera with strong antibacterial activity against both planktonic and biofilm cells of the bacterial pathogens such as S. aureus, S. agalactiae, P. aeruginosa and E. faecalis (MIC = 0.009-0.09 μM). Another broad-spectrum antimicrobial peptide coprisin isolated from Copris tripartitus has antibiofilm property against a wide range of pathogenic bacteria such as E. faecium, S. aureus, E. coli, S. mutans, P. aeruginosa (MIC = 1.7-3.4 μM) (Hwang et al, 2009)
Bacterial Lux operon encoded genetic factors, LuxR and LuxL are two well-known QSregulator genes during biofilm formation; as an example, the selective antibiofilm peptides were docked against the protein structure of S. aureus-LuxR (PDB ID: 3B2N) and recorded the binding affinity using HPEPDOCK tool with proper interaction (Figure 8)
Summary
A biofilm is a layer of polymeric organic matter to which microorganisms like fungi and/or bacteria, are attached in a sessile form. C-di-GMP plays a decisive role in the switch between planktonic and biofilm formation, as well as biofilm structure development through the synthesis of exopolysaccharides, adhesive pili, secretion of extracellular DNA, along with regulating cell death and survival. Sojka et al (2016) isolated defencin-1 (derived from defensin) from A. melifera with strong antibacterial activity against both planktonic and biofilm cells of the bacterial pathogens such as S. aureus, S. agalactiae, P. aeruginosa and E. faecalis (MIC = 0.009-0.09 μM) Another broad-spectrum antimicrobial peptide coprisin isolated from Copris tripartitus has antibiofilm property against a wide range of pathogenic bacteria such as E. faecium, S. aureus, E. coli, S. mutans, P. aeruginosa (MIC = 1.7-3.4 μM) (Hwang et al, 2009). Several models have been projected to elucidate the bacterial cell membrane disruption out of which, the Barrel-stave, Frontiers in Microbiology | www.frontiersin.org
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