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The effects of macrolide and quinolone antibiotics in methicillin-resistant Staphylococcus aureus biofilm growth
M K Dasgupta1, H Shishido, S Salama
1University of Alberta, Edmonton, Canada.
Abstract:
Recent studies demonstrate that 14-membered macrolides increase permeability and destruction of Pseudomonas biofilms. The effect of a macrolide antibiotic, erythromycin, on methicillin-resistant Staphylococcus aureus (MRSA) biofilm on Silastic catheter materials in comparison with two different quinolone antibiotics, sparfloxacin (SPFX) and a new quinolone, SYN 1193, was examined. Two different MRSA strains were grown in biofilm, using Mueller-Hinton broth with and without the addition of 10% pooled normal human serum (PNHS), in a modified Robbins device, at 37 degrees C for 24, 48, and 72 hours. Two different clinical MRSA strains were used and minimum bactericidal concentration (MBC) were determined at the time intervals mentioned. Three different dosages of each antibiotic were tested: 5.0, 20.0, and 50.0 micrograms/mL. In addition, a constant dosage of SPFX and SYN 1193, in combination with varying dosages of erythromycin, was tested under similar experimental conditions. SYN 1193 demonstrated the highest MBC in comparison to SPFX; addition of PNHS did not alter the effect of SYN 1193. However, erythromycin alone and in combination with SPFX and SYN 1193 had no effect on MBC. We conclude that (1) macrolide antibiotic erythromycin has poor MRSA biofilm permeability and killing in comparison to SPFX and SYN 1193, and (2) SYN 1193 had the highest MBC to MRSA biofilm.
Insights
Erythromycin showed poor effectiveness against methicillin-resistant Staphylococcus aureus (MRSA) biofilms. The new quinolone SYN 1193 demonstrated the highest bactericidal concentration against MRSA biofilms.
Area of Science:
- Microbiology
- Infectious Diseases
- Biomedical Engineering
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant threat due to biofilm formation on medical devices.
- Macrolide antibiotics are known to affect Pseudomonas biofilms, but their efficacy against MRSA biofilms is less understood.
- Quinolone antibiotics, including sparfloxacin (SPFX) and SYN 1193, are potential agents for combating MRSA infections.
Purpose of the Study:
- To compare the efficacy of erythromycin, SPFX, and SYN 1193 against MRSA biofilms on Silastic catheter materials.
- To evaluate the impact of pooled normal human serum (PNHS) on antibiotic activity against MRSA biofilms.
- To determine the minimum bactericidal concentration (MBC) of these antibiotics at various time points.
Main Methods:
- MRSA strains were cultured in a modified Robbins device to form biofilms on Silastic catheters.
- Antibiotic efficacy was assessed by determining the MBC of erythromycin, SPFX, and SYN 1193 at 24, 48, and 72 hours.
- Combinations of erythromycin with SPFX or SYN 1193 were also tested.
Main Results:
- SYN 1193 exhibited the highest MBC against MRSA biofilms, outperforming SPFX.
- The presence of PNHS did not significantly alter the efficacy of SYN 1193.
- Erythromycin, both alone and in combination with SPFX or SYN 1193, showed no significant effect on MRSA biofilm killing.
Conclusions:
- Erythromycin demonstrates limited efficacy in penetrating and eradicating MRSA biofilms compared to quinolones.
- SYN 1193 is a potent agent against MRSA biofilms, showing the highest MBC.
- These findings suggest that quinolone antibiotics, particularly SYN 1193, may be more effective than erythromycin for treating MRSA biofilm infections on catheters.