Evaluation of antimicrobial peptide-antibiotic combination treatment for tackling ocular and systemic infections
Barahim, Eman Khalid Smith, Ella P Yong, Sheau Ting Aung, Thet Tun Lakshminarayanan, Rajamani Mohammed, Imran Dua, Harminder S Wallace, Graham R Hombrebueno, Jose R
Barahim, Eman Khalid
Smith, Ella P
Yong, Sheau Ting
Aung, Thet Tun
Lakshminarayanan, Rajamani
Mohammed, Imran
Dua, Harminder S
Wallace, Graham R
Hombrebueno, Jose R
Abstract
Staphylococcus aureus is a leading cause of bacterial keratitis and antimicrobial resistance-associated death globally. This study aimed to evaluate the efficacy of CaD23, a human-derived hybrid antimicrobial peptide (AMP), in combination with antibiotics in treating S. aureus infections. The efficacy of CaD23 and six medically important antibiotics (amikacin, cefuroxime, chloramphenicol, fosfomycin, vancomycin and levofloxacin) was examined against six strains of methicillin-sensitive and methicillin-resistant S. aureus using a minimum inhibitory concentration (MIC) assay. CaD23-antibiotic interactions were evaluated using checkerboard and time-kill kinetics assays. 3,3'-dipropylthiadicarbocyanine iodide (DiSC3,5) cytoplasmic membrane depolarisation assay was performed to examine the mechanism of action. Overall, CaD23 exhibited good efficacy against all MSSA and MRSA (MIC = 16-32 μg/mL [6.7-13.3 μM]). Of 20 peptide-antibiotic-organism combinations, 19 (95%) combinations demonstrated positive interactions, with six (31.6%) and 13 (68.4%) exhibiting synergistic (FICI = 0.293-0.412) and additive effects (FICI = 0.521-0.890), respectively. CaD23 was able to achieve complete bacterial eradication significantly faster than cefuroxime and levofloxacin (15 min vs. 8-24 h). When used at a sub-MIC concentration, CaD23 could accelerate the killing of S. aureus of cefuroxime from 8-24 h to within 1 h and enhance the activity of levofloxacin by 90%. CaD23 was shown to rapidly depolarise the inner membrane of S. aureus within seconds of the treatment. In conclusion, CaD23-antibiotic combination therapy serves as a useful strategy for tackling drug-resistant ocular and systemic S. aureus infections.
MIDER Authors
Affiliations
University of Birmingham; University of Jeddah; Queen's Medical Centre; Sandwell and West Birmingham NHS Trust; et al.
Date
2026-06-20
Type
Article
Collections
Citation
Barahim EK, Smith EP, Yong ST, Aung TT, Lakshminarayanan R, Mohammed I, Dua HS, Wallace GR, Hombrebueno JR, Rauz S, Ting DSJ. Evaluation of Antimicrobial Peptide-Antibiotic Combination Treatment for Tackling Ocular and Systemic Staphylococcus aureus Infections. Int J Mol Sci. 2026 Jun 20;27(12):5573. doi: 10.3390/ijms27125573