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Synergism between Medihoney and rifampicin against methicillin-resistant Staphylococcus aureus (MRSA).

Müller P, Alber DG, Turnbull L, Schlothauer RC, Carter DA, Whitchurch CB, Harry EJ - PLoS ONE (2013)

Bottom Line: Combinational treatment of chronic wounds with manuka honey and common antibiotics may offer a wide range of advantages including synergistic enhancement of the antibacterial activity, reduction of the effective dose of the antibiotic, and reduction of the risk of antibiotic resistance.Methylglyoxal (MGO), believed to be the major antibacterial compound in manuka honey, did not act synergistically with rifampicin and is therefore not the sole factor responsible for the synergistic effect of manuka honey with rifampicin.Our findings support the idea that a combination of honey and antibiotics may be an effective new antimicrobial therapy for chronic wound infections.

View Article: PubMed Central - PubMed

Affiliation: The ithree institute, University of Technology Sydney (UTS), Sydney, New South Wales, Australia.

ABSTRACT
Skin and chronic wound infections caused by highly antibiotic resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) are an increasing and urgent health problem worldwide, particularly with sharp increases in obesity and diabetes. New Zealand manuka honey has potent broad-spectrum antimicrobial activity, has been shown to inhibit the growth of MRSA strains, and bacteria resistant to this honey have not been obtainable in the laboratory. Combinational treatment of chronic wounds with manuka honey and common antibiotics may offer a wide range of advantages including synergistic enhancement of the antibacterial activity, reduction of the effective dose of the antibiotic, and reduction of the risk of antibiotic resistance. The aim of this study was to investigate the effect of Medihoney in combination with the widely used antibiotic rifampicin on S. aureus. Using checkerboard microdilution assays, time-kill curve experiments and agar diffusion assays, we show a synergism between Medihoney and rifampicin against MRSA and clinical isolates of S. aureus. Furthermore, the Medihoney/rifampicin combination stopped the appearance of rifampicin-resistant S. aureus in vitro. Methylglyoxal (MGO), believed to be the major antibacterial compound in manuka honey, did not act synergistically with rifampicin and is therefore not the sole factor responsible for the synergistic effect of manuka honey with rifampicin. Our findings support the idea that a combination of honey and antibiotics may be an effective new antimicrobial therapy for chronic wound infections.

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Enhanced antibacterial activity of rifampicin-honey combination treatment against S. aureus.(A) Time-kill curves for S. aureus NCTC8325 in CaMHB. Bacteria were incubated in 7% Medihoney, 0.2 µg/ml rifampicin, or both. A growth control using just CaMHB is included as indicated. Rif: rifampicin; *: below detection limit (<50 CFU/ml). (B) Filter discs containing 4 µg of rifampicin were placed on S. aureus NCTC8325 spread on TSA plates containing no honey (TSA), 5% sugar solution (sugar), 5% manuka honey, or 5% Medihoney. The shown plates were incubated at 37°C for 24 h. Red arrows denote rifampicin resistant colonies that appeared on the TSA and sugar control plates, but not on Medihoney or manuka honey plates. Minimum inhibitory concentrations of break-through colonies (clones 1–3) were determined against Medihoney and rifampicin (see Fig. 4). (C) Sensitivity of different S. aureus strains to rifampicin and honey using the agar disc diffusion assay. Diameter (in mm) of zones of inhibition around 4 µg-impregnated rifampicin discs on TSA plates without honey (red bars), and in the presence of either 5% sugar solution (blue bars), 5% manuka honey (green bars) or 5% Medihoney (black bars).
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pone-0057679-g001: Enhanced antibacterial activity of rifampicin-honey combination treatment against S. aureus.(A) Time-kill curves for S. aureus NCTC8325 in CaMHB. Bacteria were incubated in 7% Medihoney, 0.2 µg/ml rifampicin, or both. A growth control using just CaMHB is included as indicated. Rif: rifampicin; *: below detection limit (<50 CFU/ml). (B) Filter discs containing 4 µg of rifampicin were placed on S. aureus NCTC8325 spread on TSA plates containing no honey (TSA), 5% sugar solution (sugar), 5% manuka honey, or 5% Medihoney. The shown plates were incubated at 37°C for 24 h. Red arrows denote rifampicin resistant colonies that appeared on the TSA and sugar control plates, but not on Medihoney or manuka honey plates. Minimum inhibitory concentrations of break-through colonies (clones 1–3) were determined against Medihoney and rifampicin (see Fig. 4). (C) Sensitivity of different S. aureus strains to rifampicin and honey using the agar disc diffusion assay. Diameter (in mm) of zones of inhibition around 4 µg-impregnated rifampicin discs on TSA plates without honey (red bars), and in the presence of either 5% sugar solution (blue bars), 5% manuka honey (green bars) or 5% Medihoney (black bars).

Mentions: To confirm the synergistic activity between rifampicin and Medihoney, time-kill experiments were performed (Fig. 1A). With an initial inoculum of 107 CFU/mL, 7% Medihoney alone (sub-MIC level) slowed down bacterial growth. However, growth of bacteria then increased and by 24 h, bacterial growth in the presence of 7% Medihoney was at the same level as no treatment. Rifampicin alone also completely inhibited bacterial growth up to 8 h of incubation. However, even at 0.2 µg/mL (∼5×MIC) the CFU/mL count increased dramatically after 8 h to levels of growth similar to that observed in the untreated cultures at 24 h. This is due to the attainment of resistance to this antibiotic by S. aureus (see below). A combination of 7% Medihoney and 0.2 µg/mL rifampicin yielded a >2-log10 decrease in CFU/mL compared to rifampicin or Medihoney alone, and this was sustained up to 48 h (Fig. 1A). This is considered to be a synergistic activity [43]. Similar results were observed with rifampicin plus manuka honey at the same concentrations (data not shown).


Synergism between Medihoney and rifampicin against methicillin-resistant Staphylococcus aureus (MRSA).

Müller P, Alber DG, Turnbull L, Schlothauer RC, Carter DA, Whitchurch CB, Harry EJ - PLoS ONE (2013)

Enhanced antibacterial activity of rifampicin-honey combination treatment against S. aureus.(A) Time-kill curves for S. aureus NCTC8325 in CaMHB. Bacteria were incubated in 7% Medihoney, 0.2 µg/ml rifampicin, or both. A growth control using just CaMHB is included as indicated. Rif: rifampicin; *: below detection limit (<50 CFU/ml). (B) Filter discs containing 4 µg of rifampicin were placed on S. aureus NCTC8325 spread on TSA plates containing no honey (TSA), 5% sugar solution (sugar), 5% manuka honey, or 5% Medihoney. The shown plates were incubated at 37°C for 24 h. Red arrows denote rifampicin resistant colonies that appeared on the TSA and sugar control plates, but not on Medihoney or manuka honey plates. Minimum inhibitory concentrations of break-through colonies (clones 1–3) were determined against Medihoney and rifampicin (see Fig. 4). (C) Sensitivity of different S. aureus strains to rifampicin and honey using the agar disc diffusion assay. Diameter (in mm) of zones of inhibition around 4 µg-impregnated rifampicin discs on TSA plates without honey (red bars), and in the presence of either 5% sugar solution (blue bars), 5% manuka honey (green bars) or 5% Medihoney (black bars).
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Related In: Results  -  Collection

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pone-0057679-g001: Enhanced antibacterial activity of rifampicin-honey combination treatment against S. aureus.(A) Time-kill curves for S. aureus NCTC8325 in CaMHB. Bacteria were incubated in 7% Medihoney, 0.2 µg/ml rifampicin, or both. A growth control using just CaMHB is included as indicated. Rif: rifampicin; *: below detection limit (<50 CFU/ml). (B) Filter discs containing 4 µg of rifampicin were placed on S. aureus NCTC8325 spread on TSA plates containing no honey (TSA), 5% sugar solution (sugar), 5% manuka honey, or 5% Medihoney. The shown plates were incubated at 37°C for 24 h. Red arrows denote rifampicin resistant colonies that appeared on the TSA and sugar control plates, but not on Medihoney or manuka honey plates. Minimum inhibitory concentrations of break-through colonies (clones 1–3) were determined against Medihoney and rifampicin (see Fig. 4). (C) Sensitivity of different S. aureus strains to rifampicin and honey using the agar disc diffusion assay. Diameter (in mm) of zones of inhibition around 4 µg-impregnated rifampicin discs on TSA plates without honey (red bars), and in the presence of either 5% sugar solution (blue bars), 5% manuka honey (green bars) or 5% Medihoney (black bars).
Mentions: To confirm the synergistic activity between rifampicin and Medihoney, time-kill experiments were performed (Fig. 1A). With an initial inoculum of 107 CFU/mL, 7% Medihoney alone (sub-MIC level) slowed down bacterial growth. However, growth of bacteria then increased and by 24 h, bacterial growth in the presence of 7% Medihoney was at the same level as no treatment. Rifampicin alone also completely inhibited bacterial growth up to 8 h of incubation. However, even at 0.2 µg/mL (∼5×MIC) the CFU/mL count increased dramatically after 8 h to levels of growth similar to that observed in the untreated cultures at 24 h. This is due to the attainment of resistance to this antibiotic by S. aureus (see below). A combination of 7% Medihoney and 0.2 µg/mL rifampicin yielded a >2-log10 decrease in CFU/mL compared to rifampicin or Medihoney alone, and this was sustained up to 48 h (Fig. 1A). This is considered to be a synergistic activity [43]. Similar results were observed with rifampicin plus manuka honey at the same concentrations (data not shown).

Bottom Line: Combinational treatment of chronic wounds with manuka honey and common antibiotics may offer a wide range of advantages including synergistic enhancement of the antibacterial activity, reduction of the effective dose of the antibiotic, and reduction of the risk of antibiotic resistance.Methylglyoxal (MGO), believed to be the major antibacterial compound in manuka honey, did not act synergistically with rifampicin and is therefore not the sole factor responsible for the synergistic effect of manuka honey with rifampicin.Our findings support the idea that a combination of honey and antibiotics may be an effective new antimicrobial therapy for chronic wound infections.

View Article: PubMed Central - PubMed

Affiliation: The ithree institute, University of Technology Sydney (UTS), Sydney, New South Wales, Australia.

ABSTRACT
Skin and chronic wound infections caused by highly antibiotic resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) are an increasing and urgent health problem worldwide, particularly with sharp increases in obesity and diabetes. New Zealand manuka honey has potent broad-spectrum antimicrobial activity, has been shown to inhibit the growth of MRSA strains, and bacteria resistant to this honey have not been obtainable in the laboratory. Combinational treatment of chronic wounds with manuka honey and common antibiotics may offer a wide range of advantages including synergistic enhancement of the antibacterial activity, reduction of the effective dose of the antibiotic, and reduction of the risk of antibiotic resistance. The aim of this study was to investigate the effect of Medihoney in combination with the widely used antibiotic rifampicin on S. aureus. Using checkerboard microdilution assays, time-kill curve experiments and agar diffusion assays, we show a synergism between Medihoney and rifampicin against MRSA and clinical isolates of S. aureus. Furthermore, the Medihoney/rifampicin combination stopped the appearance of rifampicin-resistant S. aureus in vitro. Methylglyoxal (MGO), believed to be the major antibacterial compound in manuka honey, did not act synergistically with rifampicin and is therefore not the sole factor responsible for the synergistic effect of manuka honey with rifampicin. Our findings support the idea that a combination of honey and antibiotics may be an effective new antimicrobial therapy for chronic wound infections.

Show MeSH
Related in: MedlinePlus