Background:Antibiotic resistance is one of the main concerns of public health, and the
whole world is trying to overcome such a challenge by finding novel therapeutic modalities and
approaches. This study has applied the sequence hybridization approach to the original sequence
of two cathelicidin natural parent peptides (BMAP-28 and LL-37) to design a novel HLM peptide
with broad antimicrobial activity.Methods:The physicochemical characteristics of the newly designed peptide were determined. As
well, the new peptide’s antimicrobial activity (Minimum Inhibitory Concentration (MIC), Minimum
Bacterial Eradication Concentration (MBEC), and antibiofilm activity) was tested on two
control (Staphylococcus aureus ATCC 29213, Escherichia coli ATCC 25922) and two resistant
(Methicillin-resistant Staphylococcus aureus (MRSA) ATCC BAA41, New Delhi metallo-beta-
lactamase-1 Escherichia coli ATCC BAA-2452) bacterial strains. Furthermore, synergistic
studies have been applied to HLM-hybridized peptides with five conventional antibiotics by
checkerboard assays. Also, the toxicity of HLM-hybridized peptide was studied on Vero cell lines
to obtain the IC50 value. Besides the percentage of hemolysis action, the peptide was tested in
freshly heparinized blood.Results:The MIC values for the HLM peptide were obtained as 20, 10, 20, and 20 μM, respectively.
Also, the results showed no hemolysis action, with low to slightly moderate toxicity action
against mammalian cells, with an IC50 value of 10.06. The Biomatik corporate labs, where HLM
was manufactured, determined the stability results of the product by Mass Spectrophotometry (MS)
and High-performance Liquid Chromatography (HPLC) methods. The HLM-hybridized peptide
exhibited a range of synergistic to additive antimicrobial activities upon combination with
five commercially available different antibiotics. It has demonstrated the biofilm-killing effects in
the same concentration required to eradicate the control strains.Conclusion:The results indicated that HLM-hybridized peptide displayed a broad-spectrum activity
toward different bacterial strains in planktonic and biofilm forms. It showed synergistic or additive
antimicrobial activity upon combining with commercially available different antibiotics.