Abstract
Red onion skin (Allium cepa var ascalonicum) contains various ingredients that may function as antibacterial agents against microorganisms, as well as anti-inflammatory and immunomodulator agents for host cells, such as macrophages. Pseudomonas aeruginosa found in the oral cavity is commensal bacteria that may turn into opportunistic pathogen by utilizing its virulence factors such as motility and adhesion to the host cell. The purpose of this study was to investigate the effect of red-onion-skin ethanolic extract towards P. aeruginosa ATCC 9027 on the motility and adhesion ability, furthermore, to know its effect on the macrophage phagocytosis. The research was conducted into three parts of experiment using red-onion-skin ethanolic extract. Extract-induced bacterial motility test was carried out on semi-solid media, stained using 0.1% crystal violet, then the radial length of the bacterial movement was measured. The bacterial adhesion index to buccal cells was calculated after incubated for two hours and stained with Gram stain. Phagocytic activity of the host cells on P. aeruginosa was done by exposing the extract to the mouse peritoneal macrophages, then the phagocytosed bacteria were counted after Giemsa staining. Statistical test results from the three experiments showed significant differences between the test groups compared to the control groups (p <0.05). It was concluded that the red onion-skin ethanolic extract not only affects P. aeruginosa by reducing swarming motility and preventing bacterial adhesion to buccal epithelial cells, but also induces the host cells by increasing the ability of macrophage phagocytosis to these bacteria.
Highlights
Pseudomonas aeruginosa is a Gramnegative, motile, rod-shaped bacteria that lives in an aerobic and anaerobic environment (Burrows, 2012), and is a cause of nosocomial infections because it may turn from oral commensal bacteria to opportunistic pathogen (Lister et al, 2009)
The aims of the study were to investigate the effects of red onion skin ethanolic extract on P. aeruginosa motility and its attachment to buccal epithelial cells, to study the ability of macrophage phagocytosis against P. aeruginosa in vitro
The radial measurements of bacterial swarming motility showed a reduction in bacterial motility along with the increase of red onion skin extract concentration (Figure 1)
Summary
Pseudomonas aeruginosa is a Gramnegative, motile, rod-shaped bacteria that lives in an aerobic and anaerobic environment (Burrows, 2012), and is a cause of nosocomial infections because it may turn from oral commensal bacteria to opportunistic pathogen (Lister et al, 2009). P. aeruginosa can be found in subgingival plaque, gingival sulcus epithelium and buccal epithelial cells (Caldas et al, 2015). In certain conditions these bacteria may turn into pathogens and worsen the infection of the oral cavity. Pseudomonas aeruginosa has flagella and type IV pili (Conrad et al, 2011) which play a role in swarming motility and as a virulence factor (Wu et al, 2011) by binding to epithelial cells. PilA protein in pili binds to glycolipids and glycoproteins asialoGM1 and GM2 (Albrecht et al, 2002; Johnson et al, 2011), whereas PILY1 binds to calcium in the epithelial cell integrins (Johnson et al, 2011)
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