Antibacterial activity of vB_AbaM_PhT2 phage hydrophobic amino acid fusion endolysin, combined with colistin against Acinetobacter baumannii

Abstract

Phage lytic enzymes are promising antimicrobial agents. In this study, an endolysin derived from vB_AbaM_PhT2 (vPhT2), was identified. This endolysin represented the conserved lysozyme domain. Recombinant endolysin (lysAB- vT2) and hydrophobic fusion endolysin (lysAB-vT2-fusion) were expressed and purified. Both endolysins showed lytic activity against bacterial crude cell wall of Gram-negative bacteria. The MIC of lysAB-vT2-fusion was 2 mg/ml corresponding to 100 µM, while the MIC of lysAB-vT2 was more than 10 mg/ml (400 µM). Combination of lysAB-vT2-fusion with colistin, polymyxin B or copper was synergistic against A. baumannii (FICI value as 0.25). Antibacterial activity of lysAB-vT2-fusion plus colistin at the fractional inhibitory concentrations (FICs) revealed that it can inhibit Escherichia coli, Klebsiella pneumoniae and various strains of extremely drug-resistant A. baumannii (XDRAB) and phage resistant A. baumannii. The lysAB- vT2-fusion still retained its antibacterial activity after incubating the enzyme at 4, 20, 40 and 60 °C for 30 min. The lysAB-vT2-fusion could inhibit the mature biofilm, and incubation of lysAB-vT2-fusion with T24 human cells infected with A. baumannii led to a partial reduction of LDH release from T24 cells. In summary, our study highlights the antimicrobial ability of engineered lysAB-vT2-fusion endolysin, which can be applied for the control of A. baumannii infection.

Engineered endolysin of Klebsiella pneumoniae phage is a potent and broad-spectrum bactericidal agent against “ESKAPEE” pathogens

“…Notably, polymyxins primarily target bacterial membranes, disrupting their integrity and inducing cell death, rendering them as last-resort antibiotics for Gram-negative bacteria ( Briers et al, 2014 ). This finding aligns with the study by Sitthisak et al (2023) , which reported a synergistic interaction between an engineered endolysin from phage vB_AbaM_PhT2 and colistin against A. baumannii , with a FICI of 0.25. Similarly, the engineered EC340, derived from phage PBEC131 infecting Escherichia coli , demonstrated a synergistic effect exclusively with colistin and an additive effect with meropenem, tigecycline, chloramphenicol, azithromycin, and ciprofloxacin ( Hong et al, 2022 ).…”

Endolysins: a new antimicrobial agent against antimicrobial resistance. Strategies and opportunities in overcoming the challenges of endolysins against Gram-negative bacteria

“…And to slow the spread of antibiotic resistance by using fewer antibiotic treatments of low dosages ( Lai et al, 2020a ). Combined use of endolysin LysAB-vT2-fusion with colistin, polymyxin B, or copper showed synergistic against A. baumannii , which may be used for the control of A. baumannii infection ( Sitthisak et al, 2023b ).…”