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Model-dependent efficacy of sequential phage-antibiotic-antifungal therapy against dual-species biofilms
Marta Gliźniewicz1, Barbara Dołęgowska1, Kamila Dubrowska2
1Department of Laboratory Medicine, Chair of Microbiology, Immunology and Laboratory Medicine, Pomeranian Medical University in Szczecin, Powstańców Wielkopolskich 72, Szczecin, 70-111, Poland.
Abstract:
The rising rate of antimicrobial resistance presents a major global health risk. Staphylococcus aureus and Candida albicans often co-infect and create dual-species biofilms, which increase virulence and reduce the effectiveness of treatment of human infections. This study explores the potential of sequentially and simultaneously administering ciprofloxacin (CIP), caspofungin (CASP), and bacteriophages (AD) as an alternative method to control dual-species biofilms. The therapeutic approach was tested using biofilms formed in ex vivo fluids (human urine [HU] and heat-inactivated human plasma blood [HIP-B]) and an in vivo model (Galleria mellonella larvae). In the HIP-B model, the microbial loads of both S. aureus and C. albicans tended to decrease across treatment combinations. Notably, the AD→CIP + CASP and CIP + CASP→AD regimens produced the largest reduction in biofilm biomass, reaching up to 40%. Conversely, the therapy was ineffective in the HU model: although microbial counts showed slight reductions, these were not statistically significant, and no decrease in biofilm biomass was observed. Using Galleria mellonella larvae as a model, the strongest protective effect was seen with the CIP + CASP→AD sequence. This combination achieved the highest median survival and the greatest reduction in mortality risk. The simultaneous triple therapy (AD + CIP + CASP) was nearly as effective. In summary, the three-factor therapy shows variable effectiveness depending on the infection environment. These results highlight the importance of testing phage-based combination therapies in the specific biological environments in which they are intended to act, as treatment efficacy proved to be strongly model-dependent.
Insights
This study tested a combination therapy of ciprofloxacin (CIP), caspofungin (CASP), and bacteriophages (AD) against dual-species biofilms. The triple therapy showed variable effectiveness, with the CIP+CASP→AD sequence being most effective in an insect model.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Antimicrobial resistance is a growing global health threat.
- Dual-species biofilms of *Staphylococcus aureus* and *Candida albicans* are linked to increased virulence and treatment challenges.
- Novel therapeutic strategies are needed to combat resistant microbial infections.
Purpose of the Study:
- To evaluate the efficacy of sequential and simultaneous administration of ciprofloxacin (CIP), caspofungin (CASP), and bacteriophages (AD) against *S. aureus* and *C. albicans* dual-species biofilms.
- To assess the therapeutic potential in different *ex vivo* and *in vivo* models.
Main Methods:
- Biofilms were formed in human urine (HU) and heat-inactivated human plasma blood (HIP-B) for *ex vivo* testing.
- An *in vivo* model using *Galleria mellonella* larvae was employed to assess treatment outcomes.
- Microbial loads and biofilm biomass were quantified to determine treatment effectiveness.
Main Results:
- In the HIP-B model, combination therapies reduced microbial loads, with AD→CIP+CASP and CIP+CASP→AD regimens decreasing biofilm biomass by up to 40%.
- The therapy was largely ineffective in the HU model, showing no significant reduction in microbial counts or biofilm biomass.
- In the *Galleria mellonella* model, the CIP+CASP→AD sequence demonstrated the strongest protective effect, significantly increasing median survival and reducing mortality risk.
Conclusions:
- Phage-based combination therapy exhibits variable efficacy depending on the biological environment.
- Treatment effectiveness is strongly model-dependent, highlighting the need for context-specific evaluation of antimicrobial strategies.
- Further research is crucial to optimize phage-based combination therapies for specific clinical applications.
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