Freshwater snails carry bacteria with antimicrobial resistance genes that could potentially transfer to human disease-causing pathogens, new research has found.
Researchers at Liverpool School of Tropical Medicine (LSTM) conducted the first metagenomic analysis of freshwater snail faeces, collected from 15 freshwater locations in Malawi, Uganda, Zanzibar and the UK.
Freshwater snails transmit parasitic infections to humans, but here the researchers investigated another way in which they may contribute to the burden of disease, identifying a critical but unexplored environmental reservoir of antimicrobial resistance.
They detected genes that are predicted to cause resistance to both first and last-resort antibiotics, such as carbapenems and colistin. They were able to link these genes, including blaOXA-48-like and mcr-like genes, to environmental bacteria. Similar resistance genes have previously emerged from environmental sources to be taken up by disease-causing bacteria.
These new findings illustrate that antimicrobial resistance genes are common in snail faeces, even in remote areas where last-resort antibiotics are not often used, and therefore represents a previously undescribed reservoir. If reliance on last-resort antibiotics increases due to rising resistance to other available treatments, these resistance genes could jump from such environmental reservoirs to pathogens in response.
The new findings, published in Microbial Genomics, highlight the importance of a One Health approach to disease surveillance and control.
Angus O’Ferrall, PhD candidate at LSTM and lead author on the study, said: “Freshwater snails are well known for transmitting parasitic diseases like schistosomiasis. They are able to do this across tropical and subtropical regions because they often thrive at sites used for washing and livestock access. In our study, we saw that their faeces contain bacteria with antimicrobial resistance genes that could potentially jump to pathogenic bacteria, rendering last-resort antibiotics ineffective.
“Improving access to safe water and sanitation in communities currently reliant on contaminated water could help reduce both the burden of parasitic infections and the emergence of antimicrobial resistance.”
Professor Adam Roberts, Professor of Microbiology at LSTM and senior author, said: “This One Health, antimicrobial resistance study shows the benefits of working across disciplines, with LSTM parasitologists undertaking the sampling and microbiologists leading on the bacterial genome analysis. It really demonstrates the benefit of sampling for everything you can, if you are going to the effort of sampling at all. These findings clearly show a point of intervention where access to clean water could help reduce human and animal exposure to bacteria containing potentially transferable, clinically important, antimicrobial resistance genes.”