Publicação
Characterization of Staphylococcus aureus phages active against dormant cells
| Resumo: | The reduced effectiveness of antibiotics against S. aureus, especially due to antibiotic tolerance in dormant cells, has become a significant concern in healthcare, particularly in nosocomial infections. While phage therapy has gained renewed interest, its use is often hindered by the difficulty of targeting dormant cells, which are less susceptible to infection due to their low metabolic activity. This work investigates the potential use of phages, alone and in combination with antibiotics, to target these cells and enhance their antibiotic susceptibility. Three myovirus-like phages were isolated from wastewater, with the SA-P2H phage showing the most promising results. SA-P2H infected over 83% of the strains tested. Genomic analysis revealed SA-P2H as a virulent phage, supported by its similarity to other virulent Kayvirus phages, including phage K and JD007, known for their broad ability to infect diverse S. aureus strains. Treatment of S. aureus stationary cells (48-hour subculture), used as a model for dormant cells, for 24 hours with SA-P2H initially resulted in a 1 log reduction in CFU/mL, which improved to a 3.8 log reduction in later assays, reinforcing the potential of SA-P2H as a versatile therapeutic candidate. Doxycycline was selected for combination treatments as it showed no activity against late stationary cells but remained effective against exponential cells. However, the simultaneous application of SA-P2H and doxycycline resulted in antagonistic interactions, reducing bacterial levels by 2.5 log. The sequential treatment, with the antibiotic added 6 hours after the phage, achieved a 3.5 log reduction but showed no statistically significant improvement over phage treatment alone. While the combination with the phage did not enhance doxycycline’s activity, SA-P2H proved to be highly effective in targeting S. aureus late stationary cells, making it a strong candidate for phage-based therapies. Notably, the increased efficacy of SA-P2H over time suggests that spontaneous mutations during phage propagation may have enhanced its infectivity. Future studies will aim to further explore the interaction between SA-P2H and dormant cells, optimize phage-antibiotic combinations by exploring alternative antibiotics and adjusting dosage and timing, and confirm these potential mutations. |
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| Autores principais: | Matos, Beatriz da Silva |
| Assunto: | Bacteriophages Staphylococcus aureus Kayvirus Dormant cells Antibiotics Doxycy-cline Phage-antibiotic synergy Bacteriófagos Células dormentes Antibióticos Doxiciclina Sinergia fago-antibiótico |
| Ano: | 2024 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | The reduced effectiveness of antibiotics against S. aureus, especially due to antibiotic tolerance in dormant cells, has become a significant concern in healthcare, particularly in nosocomial infections. While phage therapy has gained renewed interest, its use is often hindered by the difficulty of targeting dormant cells, which are less susceptible to infection due to their low metabolic activity. This work investigates the potential use of phages, alone and in combination with antibiotics, to target these cells and enhance their antibiotic susceptibility. Three myovirus-like phages were isolated from wastewater, with the SA-P2H phage showing the most promising results. SA-P2H infected over 83% of the strains tested. Genomic analysis revealed SA-P2H as a virulent phage, supported by its similarity to other virulent Kayvirus phages, including phage K and JD007, known for their broad ability to infect diverse S. aureus strains. Treatment of S. aureus stationary cells (48-hour subculture), used as a model for dormant cells, for 24 hours with SA-P2H initially resulted in a 1 log reduction in CFU/mL, which improved to a 3.8 log reduction in later assays, reinforcing the potential of SA-P2H as a versatile therapeutic candidate. Doxycycline was selected for combination treatments as it showed no activity against late stationary cells but remained effective against exponential cells. However, the simultaneous application of SA-P2H and doxycycline resulted in antagonistic interactions, reducing bacterial levels by 2.5 log. The sequential treatment, with the antibiotic added 6 hours after the phage, achieved a 3.5 log reduction but showed no statistically significant improvement over phage treatment alone. While the combination with the phage did not enhance doxycycline’s activity, SA-P2H proved to be highly effective in targeting S. aureus late stationary cells, making it a strong candidate for phage-based therapies. Notably, the increased efficacy of SA-P2H over time suggests that spontaneous mutations during phage propagation may have enhanced its infectivity. Future studies will aim to further explore the interaction between SA-P2H and dormant cells, optimize phage-antibiotic combinations by exploring alternative antibiotics and adjusting dosage and timing, and confirm these potential mutations. |
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