Pine needles are used in folk medicine to treat liver disease, gastrointestinal diseases, nervous system disease,
circulatory diseases, and skin problems. The present study was to evaluate the antibacterial activity of methanol (MeOH)
extract of pine needles against some cariogenic and periodontal bacteria. The chekerboard and time-kill tests were used
for the combined evaluations. The MIC and MBC values for MeOH extract against all tested oral bacteria were in the
ranges 0.25-4 mg/mL and 1-16 mg/mL, respectively. The range of MIC50 and MIC90 of MeOH extract was 0.0625-2 mg/mL
and 1-16 mg/mL, respectively. Significant synergies were observed by the MeOH extract with ampicillin or gentamicin
combinations at FICI ranged all 0.5. Furthermore, 2-6 hours of treatment with 1/2 MIC of MeOH extract with 1/2 MIC of
antibiotics resulted in an increase in the rate of killing in units of CFU/ml to a greater degree than was observed with
MeOH extract alone. These results demonstrated that MeOH extract of pine needles enhanced the efficacy of ampicillin
and gentamicin in vitro, which had potential for combinatory therapy of patients infected with oral pathogens.
Keywords: Antibacterial activity, minimum bactericidal concentrations, minimum inhibitory concentrations, synergistic effect,
pine needle (Pinus densiflora).
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