Scientists studying the spread of antimicrobial resistance (AMR) in Australian commercial pig operations have some good news for both their pig farmers, and the wider community. The absence of genes resistant to drugs used to treat critically sick people means that AMR may not be as widespread as some feared.
Concern remains, however, because the research does show that the universally present gut bacteria Escherichia coli is primed to acquire these AMR genes. The research, published in Microbial Genomics, supports The Food and Agriculture Organisation recommendations that, globally, animal husbandry practices need to change to avoid the spread of AMR.
“The role played by food animal production practices in the spread of AMR has been hotly debated but is likely to be significant,” says Steven Djordjevic, Professor of Infectious Disease at the University of Technology Sydney (UTS) ithree institute.
Djordjevic, the study’s senior author, says that, based on the outcomes of the research, bacteria from food production animals should be monitored in the context of public health, and that alternative strategies to using antibiotics in intensive animal farming be implemented.
“The results will help in assessing the potential risk to human health from consuming pork products, and the management of pig waste and its risk to the environment,” Djordjevic says.
Although a study of only two commercial pig farms in NSW, the UTS study is the first detailed genomic analysis of multi-drug resistant (MDR) E. coli from commercial piggeries in Australia. Whilst E. coli is a normal member of healthy gut bacteria in pigs, humans, and other animals, it can cause serious urinary tract, kidney and blood infections in humans. By 2050, it is predicted that E. coli will be responsible for more than three million fatal MDR infections in humans every year.
“Pig production routinely involves antibiotic use to treat disease and to stop it spreading,” ithree institute PhD student and lead author Cameron Reid says.
“Our research shows that E. coli isolated from these commercial pig farms carry highly mobile drug resistance, and both the bugs and the genes may be passed to us through food and environmental pathways.
“The genes they carry can rapidly spread to bacteria more suited to causing human infections and the antimicrobial residues provide a selection pressure that promotes the exchange of AMR genes,” says Reid.
The project is part of Ausgem, a collaborative research partnership with the NSW Department of Primary Industries. The findings will serve as a point of reference in the identification and tracking of porcine E. coliand the mobile resistance genes they carry.
Djordjevic, who is Ausgem’s UTS research lead, says the results highlight the need to maintain our strict antimicrobial stewardship in relation to livestock production.
“Intensive pig production produces a mountain of MDR-contaminated manure, billions of tonnes worldwide, and that means a lot of it ends up in the environment. Pig waste can be a serious environmental contaminant and our research provides the first data on baseline rates of AMR from otherwise healthy pigs,” he says.
Although not covered in the study, Djordjevic adds that the results point to ways in which farming practices should be updated to decrease risk of bacteria acquiring MDR genes. These include: using probiotics in feed; improved animal husbandry; manure treatment processes; and the development of molecular tests for the rapid identification of MDR and emerging MDR pathogens.
“This research reiterates the One Health approach we’re fostering through the Ausgem collaboration. Human health is intimately connected to our surrounds. We need to upgrade the management of wastewater from hospitals, nursing homes, and food animal production facilities, including public sewage treatment processes, to remove residues. Moreover, concerted national and international approaches are needed to address the issue of drug resistance,” says Djordevic.
A new $4m joint investment into Ausgem by the NSW DPI and UTS aims to develop new technologies to fight major pests and infectious diseases.