Abstract
The aim of this research was to test the antibacterial activity of Pinus pinaster aqueous bark ex- tract (PABE) and its basic components against multidrug-resistant isolates of Acinetobacter baumannii belonging to European clone I and II, isolated previously from the clinical outbreaks. The minimum bactericidal concentration of PABE against both clones of A. baumannii was 200 mg ml -1 , while lower concentrations showed high antibacterial activity. After 24 h of treatment with 100, 50 or 10 mg ml -1 of extract, the reduction in the number of A. baumannii isolates belonging to European clone I and II was 85.8 ± 2.5 %, 78.5 ± 1.1 %, 66.3 ± 2.5 % and 90.2 ± 1.7 %, 78.6 ± 1.2 %, 69.8 ± 0.7 %, respectively. Sev- eral basic components: caffeic acid, catechin, epicatechin, gallic acid and vanillin, detected in the extract by high performance liquid chromatography, contributed to the antibacterial activity of the extract against both clones of A. baumannii. However, the antibacterial activity of extract was higher than that of each tested basic component suggesting that proanthocyanidins, which were present in quite a large amount in the extract, might have also contributed to the activity of the extract. Antibacterial activity of PABE against A. baumannii reveals that complex and inexpensive natural product might be useful in combat against natu- rally competent bacteria that easily acquire resistance against antibiotics.
Highlights
Bark extracts of P. pinaster (PBEs) have a long history of ethnomedicinal use.[1]
The antibacterial activity of basic components against clone II (Table 3) was similar to those against clone I, except that the ferulic acid had no antibacterial activity against clone II
When basic substances were tested together against two clones of A. baumannii, the reductions of log Colony forming units (CFU) were 36.9 and 23.5 % for clone I and II, respectively. These results suggest that besides tested substances, some other substances such as proanthocyanidins, which were present in quite a large amount in the extract (Table 1), might have contributed to the antibacterial activity of extract, too
Summary
Bark extracts of P. pinaster (PBEs) have a long history of ethnomedicinal use.[1]. As a mixture of a large variety of substances, PBEs are reported to exhibit a wide range of biological activities, including antioxidative, antiinflamatory, antitumor, antiatherogenic, antiviral, antimicrobial, etc.[2]. Research on natural products represents convenient strategy to find extracts and bioactive compounds, based on which new, effective and less expensive treatments can be applied.[9] The aim of this study was to determine the antibacterial and bactericidal activity of P. pinaster aqueous bark extract (PABE) and its components against MDR A. baumannii isolated from the clinical outbreaks.
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