Effect of honey on Streptococcus mutans growth and biofilm formation - PubMed (original) (raw)

Effect of honey on Streptococcus mutans growth and biofilm formation

Hani M Nassar et al. Appl Environ Microbiol. 2012 Jan.

Abstract

Because of the tradition of using honey as an antimicrobial medicament, we investigated the effect of natural honey (NH) on Streptococcus mutans growth, viability, and biofilm formation compared to that of an artificial honey (AH). AH contained the sugars at the concentrations reported for NH. NH and AH concentrations were obtained by serial dilution with tryptic soy broth (TSB). Several concentrations of NH and AH were tested for inhibition of bacterial growth, viability, and biofilm formation after inoculation with S. mutans UA159 in 96-well microtiter plates to obtain absorbance and CFU values. Overall, NH supported significantly less (P < 0.05) bacterial growth than AH at 25 and 12.5% concentrations. At 50 and 25% concentrations, both honey groups provided significantly less bacterial growth and biofilm formation than the TSB control. For bacterial viability, the results for all honey concentrations except 50% NH were not significantly different from those for the TSB control. NH was able to decrease the maximum velocity of S. mutans growth compared to AH. In summary, NH demonstrated more inhibition of bacterial growth, viability, and biofilm formation than AH. This study highlights the potential antibacterial properties of NH and could suggest that the antimicrobial mechanism of NH is not solely due to its high sugar content.

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Figures

Fig 1

Fig 1

S. mutans planktonic and biofilm cell growth absorbance values for NH and AH concentrations. The absorbance values of the 50% NH- and 50% AH-treated cultures as well as the 25% NH-treated culture were below 0.001. Horizontal lines, means and SEs of the TSB control; error bars, SEs; asterisks, significant differences (P ≤ 0.05) from the TSB control; boxed concentrations, significant difference between NH and AH groups for a specific concentration.

Fig 2

Fig 2

S. mutans growth curves for NH and AH concentrations compared to the TSB control. The graph shows absorbance values over a period of 12.5 h (45,000 s). Numbers in brackets next to groups indicate mean _V_max and mean maximum absorbance, respectively. An asterisk indicates that _V_max and maximum absorbance could not be calculated due to the influence of the high absorbance values of NH at 25% (N/A, not available). Note that there was no bacterial growth at this concentration.

Fig 3

Fig 3

S. mutans biofilm formation absorbance values for NH and AH concentrations after staining with crystal violet. Horizontal lines, means and SEs of the TSB control; error bars, SEs; asterisks, significant differences (P ≤ 0.05) from TSB control; boxed concentrations, significant difference between NH and AH groups for a specific concentration.

Fig 4

Fig 4

S. mutans viability presented as numbers of CFU in a logarithmic scale of selected concentrations of NH and AH. The viability of the 50% NH-treated sample was almost zero. Horizontal lines, means and SEs of the TSB control; error bars, SEs; asterisks, significant differences (P ≤ 0.05) from the TSB control; boxed concentrations, significant difference between NH and AH groups for a specific concentration.

Fig 5

Fig 5

S. mutans XTT viability assay absorbance values for NH, AH, and TSBS. Horizontal lines, means and SEs of the 1% TSBS control; error bars, SEs; asterisks, significant differences (P ≤ 0.05) from the 1% TSBS control. Groups with different letters were significantly different (P ≤ 0.05). Comparisons were made between solutions with the same concentration.

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