Scientists identify common gastro culprit with surprising results in babies

Scientists at UNSW have analysed bacterial pathogens in patients with gastroenteritis, with an emerging pathogen Aeromonas knocking Salmonella from second place as a leading cause of gastro.

In children younger than 18 months, the Aeromonas was the number one leading cause of the illness, the research published in Microbiology Spectrum shows.

“Our results have found that Aeromonas are the second most prevalent enteric bacterial pathogens across all age groups, and are in fact the most common enteric bacterial pathogens in children under 18 months,” says UNSW Associate Professor and co-author of the study Li Zhang. 

The findings are significant because when stool samples from gastro patients are sent to diagnostic laboratories, Aeromonas pathogens are not routinely tested for.  

Zhang says given the high rates, Aeromonas should be included on the common enteric bacterial pathogen examination list.

The researchers analysed data (including faecal samples) from more than 340,000 patients with gastroenteritis between 2015 and 2019, using PCR testing methods.

The analysis reveals Campylobacter had the highest detection rate (513 per 10,000 samples), followed by Aeromonas (255 per 10,000 samples), Salmonella (145), Yersinia (57), and Shigella (50). 

Gastroenteritis – commonly known as gastro – is a contagious short-term illness triggered by the infection and inflammation of the digestive system that causes vomiting and diarrhoea.  

By grouping samples based on age groups, the scientists were able to determine the Aeromonas infections were particularly predominant among young children and adults over 50 years old, as well as a small peak in adults 20-29.

Those three infection peaks based on patient age is also a highly unusual pattern for bacterial pathogens, which generally have one peak age, Zhang says.

Salmonella infection was previously believed to be the number two cause of gastro after Campylobacter.

Other studies suggest Aeromonas infections can be more severe than other pathogens, and may be more likely to require treatment with antibiotics. Zhang says, this is another reason to test for Aeromonas, as it is known to be resistant to penicillin.

In addition to further research identifying Aeromonas pathogens in more detail, the scientists are looking to identify the source of infection to enable effective prevention strategies. 

“We already know of at least five different species of Aeromonas cause gastrointestinal infections in Australia,” she says.

That research will involve collecting Aeromonas samples from the environment, food and from recreational and drinking water sources, comparing the genetics of the bacteria with those of infected patients.

Previous research from the Zhang team demonstrated that the majority of Aeromonas enteric infections in Australia were locally acquired, with no history of overseas travel.  

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