A conserved KL2-capsule-related phage-resistant mechanism in carbapenem-resistant Acinetobacter baumannii is surmountable by a rationally selected dual-phage cocktail
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Updated: Apr 21, 2026
Author Spotlight: Advancing Antibiotic Resistance Research Using an Efflux-Deficient Bacterial Strain and a Single-Copy Gene Expression System
Published on: January 5, 2024
Yong Shao1, Zhu Gao1, Hongyang You1
1School of Life Science and Technology, Southeast University, Nanjing, China.
Introduction:
As the use of bacteriophages to combat drug-resistant bacteria increases, phage resistance, which may lead to infection recurrence, has gradually gained attention. The intricate mechanisms underlying phage resistance, which are crucial for improving the efficacy of phage therapy, have not yet been fully delineated. This research focuses on uncovering the mechanisms of phage resistance and formulating robust strategy to address infections caused by carbapenem-resistant Acinetobacter baumannii (CRAB).
Methods:
A specific bacterium-phage pair (CRAB strain MRAB11 and lytic phage MRABP9) was employed. Phage-resistant strains were isolated and subjected to whole-genome sequencing, followed by comparative genomics analysis. A novel phage targeting phage-resistant strains, was screened and combined with MRABP9. The efficacy of the phage combination was validated in bacterial liquid growth and in mouse wound CRAB infection model. The antimicrobial spectra of phage MRABP9 and the phage combination were evaluated using multi-center clinical A. baumannii isolates, and the fitness of phage-resistant strains was determined.
Results:
All sequenced phage-MRABP9-resistant strains harbored mutations on KL2 locus under both in vitro and in vivo conditions. A novel phage MRABphi22 targeting phage-resistant strains was introduced and its combination with phage MRABP9 effectively inhibited the growth and phage resistance development of CRAB, demonstrating promising efficacy in mouse wound infection treatment. The fitness of phage-resistant isolates in terms of antibiotic resistance, virulence and growth rate, was diminished, with dual-phage resistant strains bearing higher fitness costs.
Conclusions:
The mechanism underlying the response of MRAB11 to phage MRABP9 invasion exhibits high consistency on KL2 locus and is surmountable by a well-designed dual-phage cocktail. This study offers valuable guidance for future experimental design of clinical phage therapy, and points out potential therapeutic phage candidates for treating CRAB infections.
Insights
Phage resistance in carbapenem-resistant Acinetobacter baumannii (CRAB) is overcome by a dual-phage therapy targeting specific mutations. This combination therapy effectively treats CRAB infections and reduces resistance development.
Area of Science:
- Microbiology
- Genomics
- Infectious Diseases
Background:
- Phage therapy is emerging as a strategy against drug-resistant bacteria.
- Phage resistance can lead to treatment failure and infection recurrence.
- Understanding phage resistance mechanisms is critical for effective phage therapy.
Purpose of the Study:
- To investigate the mechanisms of phage resistance in carbapenem-resistant Acinetobacter baumannii (CRAB).
- To develop a robust strategy to overcome phage resistance in CRAB infections.
- To evaluate the efficacy of a dual-phage combination therapy.
Main Methods:
- Isolated phage-resistant CRAB strains and performed whole-genome sequencing.
- Conducted comparative genomics to identify resistance mechanisms.
- Screened a novel phage and combined it with an existing phage (MRABP9) for synergistic efficacy.
- Validated the dual-phage combination in vitro and in a mouse wound infection model.
Main Results:
- Phage-resistant CRAB strains consistently showed mutations in the KL2 locus.
- A dual-phage combination (MRABP9 and MRABphi22) effectively inhibited CRAB growth and prevented resistance.
- The combination therapy demonstrated significant efficacy in a mouse wound infection model.
- Phage-resistant isolates exhibited reduced fitness, with dual-resistance conferring higher fitness costs.
Conclusions:
- CRAB resistance to phage MRABP9 is linked to KL2 locus mutations.
- A dual-phage cocktail targeting these mutations is a viable strategy to overcome resistance.
- This approach provides guidance for clinical phage therapy design against CRAB infections.
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