Dodgy tummy from eating oysters? Curcumin is the answer!

Vibrio parahaemolyticus is a gram negative bacteria which can be found in brackish and marine environments, most notably along coastlines when the water temperatures reach their peak during the summer months. It has been known to infect humans via a range of different pathways including through open cuts and wounds, and through areas such as the eyes and ears, and has even been linked to a few deaths in the Hurricane Katrina disaster. However, the most common problem associated with this bacteria is the cause of gastroenteritis in humans when undercooked or raw oysters are ingested. There have been many documented outbreaks of this, and when looking at the evergrowing problem of climate change, the outbreaks appear set to become more frequent. Thoughts of reducing levels of Vibrio parahaemolyticus before consumption of raw oysters have been in circulation for some time, and usually involve the use of non-thermal methods to decontaminate the pathogen.

Wu et al (2016) also thought about this, and set out to reduce the levels of Vibrio parahaemolyticus using antimicrobial photodynamic therapy (aPDT) – a photochemical reaction involving the interaction of a photosensitizer (PS), visible light and oxygen, as this has been shown to destroy bacterial cells of other gram negative bacteria. Curcumin was also added as it has been shown to become activated by visible light and inhibit the growth of bacterial cells. Thus, the objective was to find out if curcumin-mediated photodynamic action would inactivate Vibrio parahaemolyticus cells. The experiment was divided into four groups: negative control (no PS, no light irradiation, L-S-), LED irradiation (no PS, same irradiation as aPDT samples, L+S-), curcumin treatment (10mM, PS, no irradiation, L-S+) and LED irradiation plus curcumin treatment (5mM, 10mM, 20mM, L+S+).

The results showed that curcumin-mediated photodynamic action significantly killed Vibrio parahaemolyticus cells. The viability of Vibrio parahaemolyticus significantly reduced in L+S+ group compared to L-S- group, with a lethal rate of 100% at the 10mM and 20mM concentrations. The viability was also significantly reduced in L+S+ group compared with L-S+ group. This showed that curcumin-mediated photodynamic action worked faster and was better at inactivating the bacterial cells with both LED irradiation plus curcumin treatment, especially at the higher curcumin concentrations.

I think this paper has opened a gateway for other scientists to continue this work using this method to inactivate Vibrio parahaemolyticus cells, and future work to inactivate the bacteria whilst inside the oysters may even show the number of human cases infected with the bacteria from these oysters to significantly decrease. The method they used on this particular pathogen hadn’t been used before this study, and yet it proved to be successful in giving the results the scientists were hoping for. Due to this, I expect to see this method utilized in other similar studies in the near future.

Reviewed paper: Wu, Juan., Mou, Haijin., Xue, Changhu., Leung, Albert Wingnang., Xu, Chaunshan., and Tang, Qing-Juan. (2016). Photodynamic effect of curcumin on Vibrio parahaemolyticus. Photodiagnosis and Photodynamic Therapy. 15: 34-39.  http://www.sciencedirect.com/science/article/pii/S1572100016300539