Biofilms, sedimented microbial communities embedded in a
biopolymer matrix cause vast majority of human
bacterial infections and many severe complications such as chronic inflammatory diseases and
cancer. Biofilms' resistance to the host immunity and
antibiotics makes this kind of
infection particularly intractable.
Antimicrobial peptides (AMPs) are a ubiquitous facet of innate immunity in animals. However, AMPs activity was studied mainly on planktonic bacteria and little is known about their effects on biofilms. We studied structure and anti-biofilm activity of
AMP complex produced by the maggots of blowfly Calliphora vicina living in environments extremely contaminated by biofilm-forming germs. The complex exhibits strong cell killing and matrix destroying activity against human pathogenic
antibiotic resistant Escherichia coli, Staphylococcus aureus and Acinetobacter baumannii biofilms as well as non-toxicity to human immune cells. The complex was found to contain AMPs from
defensin,
cecropin, diptericin and
proline-rich
peptide families simultaneously expressed in response to
bacterial infection and encoded by hundreds
mRNA isoforms. All the families combine cell killing and matrix destruction mechanisms, but the ratio of these effects and antibacterial activity spectrum are specific to each family. These molecules dramatically extend the list of known anti-biofilm AMPs. However, pharmacological development of the complex as a whole can provide significant advantages compared with a conventional one-component approach. In particular, a similar level of activity against biofilm and planktonic bacteria (MBEC/MIC ratio) provides the complex advantage over conventional
antibiotics. Available methods of the complex in situ and in vitro biosynthesis make this idea practicable.