OmpW overexpression in meropenem-exposed Acinetobacter baumannii persister cells enhances virulence and reveals a
Bin Liu1,2, Junan Wang1,2, Jincheng Hu1,2
1Respiratory and Critical Care Medicine Department, The First Affiliated Hospital, Hainan Medical University, Haikou, Hainan, China.
Objective:
Acinetobacter baumannii is one of the most drug-resistant microorganisms in hospital-acquired infections. The treatment of choice for A. baumannii infections is carbapenems (e.g., meropenem). However, A. baumannii can develop resistance to all clinical antibiotics associated with the formation of persister cells. We first assessed the virulence and differential expression levels of outer membrane protein W (OmpW) in A. baumannii persister cells and A. baumannii regular cells in vivo and in vitro after exposure to meropenem.
Methods:
Persister cells were confirmed using a standard method. OmpW characterization was performed using western blot analysis, and OmpW expression was detected using real-time polymerase chain reaction (PCR) after ribonucleic acid (RNA) extraction. An A. baumannii virulence assay was performed using the Galleria mellonella larvae model. Relative expression was calculated using the 2-ΔΔCT method.
Results:
The presence of bona fide A. baumannii persister cells was confirmed after 48 h of meropenem exposure at 15 μg/mL, with levels reaching 0.3216% of the initial bacterial population and a survival fraction of 0.081%. OmpW genes were highly expressed at more than 2.68-fold (p = 0.01) with meropenem exposure at 1 μg/mL and 8.61-fold (p = 0.0005) with meropenem exposure at 15 μg/mL. There was a significant difference in the lethal dose 50% (LD50) at 24 h postinfection between persister cells (2.01 × 105 CFU/larva) and regular cells (4.73 × 105 CFU/larva) at p < 0.05. Similarly, there was a significant difference between the LD50 at 48 h for persister cells (1.61 × 105 CFU/larva) and regular cells (4.08 × 105 CFU/larva) at p < 0.05. However, there was no statistically significant difference in the LD50 at 72, 96, and 120 h postinfection.
Conclusion:
OmpW overexpression in meropenem-exposed A. baumannii persister cells enhances virulence and reveals a candidate target for preventing and controlling A. baumannii persister cells.
Insights
Meropenem-exposed Acinetobacter baumannii persister cells show increased outer membrane protein W (OmpW) expression, enhancing virulence. This suggests OmpW as a potential target for combating drug-resistant bacterial infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Acinetobacter baumannii is a significant cause of hospital-acquired infections, notorious for its multidrug resistance.
- Carbapenems like meropenem are primary treatments, but A. baumannii can develop resistance, partly through persister cell formation.
- Outer membrane protein W (OmpW) role in A. baumannii persister cell virulence is not fully understood.
Purpose of the Study:
- To investigate the virulence of A. baumannii persister cells compared to regular cells.
- To analyze the differential expression of outer membrane protein W (OmpW) in persister cells after meropenem exposure.
- To assess OmpW as a potential therapeutic target against A. baumannii persister cells.
Main Methods:
- Confirmation of A. baumannii persister cells following meropenem treatment.
- Western blot analysis for OmpW protein characterization.
- Real-time PCR for OmpW gene expression quantification after RNA extraction.
- Galleria mellonella larvae model for in vivo virulence assays.
Main Results:
- Meropenem exposure induced bona fide A. baumannii persister cells (0.3216% of population).
- OmpW gene expression significantly increased (2.68-fold to 8.61-fold) with meropenem concentrations.
- Persister cells exhibited significantly higher virulence (lower LD50) in Galleria mellonella larvae at 24 and 48 hours post-infection.
Conclusions:
- OmpW is overexpressed in meropenem-exposed A. baumannii persister cells.
- Increased OmpW expression correlates with enhanced bacterial virulence.
- OmpW represents a promising candidate target for developing strategies to control A. baumannii persister cells.
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