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Manuka honey has gained attention for its potential as an antimicrobial agent against various pathogens, including the opportunistic pathogen Mycobacterium abscessus. M. abscessus is a concern for individuals with compromised immune systems, such as those with cystic fibrosis, due to its drug-resistant nature and ability to evade the host immune response. Current treatments for M. abscessus infections are often ineffective, highlighting the need for new therapeutic options.
In a recent study, it was demonstrated that manuka honey is effective against M. abscessus and can enhance the inhibitory effect of the antibiotic amikacin. This prompted further investigation into the potential enhancement of other antibiotics, namely azithromycin and tobramycin, by the addition of manuka honey against M. abscessus complex.
Materials and Methods
Four different manuka honey samples with varying MGO (methylglyoxal) ratings were selected for the study. The honey samples were prepared as 1 g/mL stocks in sterile distilled water and filtered to remove larger particulates. M. abscessus cultures were grown in Middlebrook 7H9 broth at 37 °C for 72 hours.
A checkerboard assay was used to assess the synergy between manuka honey and either azithromycin or tobramycin. The concentrations of the antibiotics and honey were varied, and the plates were incubated at 37 °C for 96 hours. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined.
Results
The combination of manuka honey and azithromycin showed improved growth inhibition of M. abscessus complex compared to the antibiotics used alone. All four manuka honey samples tested exhibited improved activity when combined with azithromycin, with concentrations as low as 0.037 g/mL honey required for inhibition. The addition of manuka honey also reduced the concentration of azithromycin needed for growth inhibition.
Bactericidal activity was observed for three of the M. abscessus isolates when treated with the combination of manuka honey and azithromycin. The two higher-grade manuka honeys, MGO70 and MGO83, showed the most improved bactericidal activity. Notably, the macrolide-resistant M. abscessus subsp. bolletii exhibited improved inhibition and bactericidal activity in response to the combination of manuka honey and azithromycin.
In contrast, no improved activity was observed when tobramycin was combined with manuka honey against any of the M. abscessus isolates tested. Tobramycin did not exhibit the same enhancement as observed with azithromycin.
Discussion
The rise of M. abscessus infections poses a significant challenge, particularly for immunocompromised individuals. The findings of this study suggest that manuka honey has the potential to enhance the activity of azithromycin against M. abscessus. The combination of manuka honey and azithromycin resulted in improved growth inhibition and bactericidal activity, especially for the macrolide-resistant M. abscessus subsp. bolletii.
However, the combination of manuka honey and tobramycin did not show the same improvement in activity. This could be attributed to the differences in chemical structure and mode of action between tobramycin and amikacin. Further studies are needed to explore other antibiotic combinations with manuka honey and to optimize the concentrations for synergistic interactions.
The results of this study highlight the potential of manuka honey as a therapeutic option for M. abscessus infections, particularly in combination with azithromycin. Manuka honey’s antimicrobial properties and ability to enhance the activity of antibiotics make it a promising candidate for further research and development in the field of respiratory health.
In conclusion, manuka honey shows potential in improving respiratory health by enhancing the activity of antibiotics against M. abscessus. Further studies are needed to elucidate the mechanisms of this enhancement and optimize the concentrations for clinical applications. The findings of this study provide valuable insights into the potential of manuka honey as a therapeutic agent for respiratory infections caused by drug-resistant pathogens like M. abscessus.
Keywords: manuka honey, Mycobacterium abscessus, respiratory health, antimicrobial, azithromycin, tobramycin
