Is Your Sushi Safe?

Although as a general rule, sushi is safe to eat if prepared properly, but bacteria in raw seafood can make you sick, and seafood can also spread bacteria that are resistant to antibiotics. Without heat treatment or the use of other antibacterial methods, the risk of bacterial levels becoming high increases sharply. 

“Bacteria in sushi, sashimi and cold-smoked fish products can pose a risk to people who eat such foods frequently, especially people with weak immune systems, children, and the elderly,” says Hyejeong Lee, Ph.D., Department of Biotechnology and Food Science at the Norwegian University of Science and Technology (NTNU). 

Scientists have shown concern over Listeria monocytogenes for some time, this is probably the most well-known pathogen that is related to raw or mildly processed seafood. This study checked for Aeromonas bacteria in fish products readily available on the market. 

“The goal was to gain more knowledge about Aeromonas in this type of seafood – both the bacteria’s role in the deterioration of the product and in causing disease. Furthermore, we wanted to see if raw seafood can spread antibiotic-resistant bacteria,” says Dr. Lee.

“The results show that the mild processing these fish products receive does not guarantee that the growth of Aeromonas bacteria will be inhibited,” says Lee. “The majority of these Aeromonas variants are possibly pathogenic and there are often several different risk factors associated with them,” she adds.

In other words, according to Lee, in this study, the processing of sushi, sashimi, and cold smoked fish was ineffective at preventing bacterial growth. However, Lee emphasizes that the risk of getting sick from Aeromonas is very small, especially among healthy people. 

“Aeromonas is often ignored when we talk about food safety. I think my research highlights that the food industry needs to pay more attention to these bacteria,” says Lee.

Although the risk is small, it still exists, and for those unfortunate enough to become sick another factor is in play that is even more of a concern. Aeromonas bacteria frequently exchange genetic material with other bacteria, and this is a greater concern if the genetic material comes from bacteria that are resistant to antibiotics. 

“Some strains of Aeromonas can also spread antibiotic resistance from one type of bacteria to another. Eating seafood infected by resistant bacteria is a likely way these bacteria can spread from marine animals and environments to humans,” Lee concludes.

Resistant bacteria are a growing global concern, and while they do not cause more disease than other bacteria they are becoming increasingly far more difficult to treat because not all types of antibiotics work against them. In an even worse, worse-case scenario some bacteria have become so effective that no antibiotics will work against them at all. 

“To combat the spread of antibiotic-resistant bacteria, it is important that we adopt a broad approach that looks at animal and human health, food production and the environment together in order to achieve better public health,” says Anita Nordeng Jakobsen, associate professor at NTNU’s Department of Biotechnology and Food Science.

Microorganisms are transferred between animals and humans via food and the environment, meaning that the reduced use of antibiotics alone is not sufficient enough to prevent bacterial proliferation. More preventive measures are required like systematically monitoring and taking samples in production environments, and implementing measures when multi-drug resistant bacteria are detected in animals, vaccination, and education including awareness-raising work in food production around the world. 

The most important method of tackling the problem of antibiotic-resistant bacteria is probably strict regulation and reforming food safety by authorities, this will involve looking at animal and human health, food production, and the environment. However, individuals can also make a difference by paying attention to how food is being prepared from start to finish, and choosing raw products from suppliers that only use small amounts of antibiotics in aquaculture such as Norway. Norway is among the best in the world when it comes to restrictive use in both the aquaculture industry and livestock farming.