Where human and animal sewage
Finding the perfect marker
Researchers identified several genetic markers for tracking fecal pollution. Using CrAssphage as a genetic marker was ideal as it is nearly nonexistent in animals. This bacteriophage is more abundant in humans than many other phages. Given this information, crAssphage was the ideal marker for researchers determining human fecal pollution levels in the environment. This marker is also key in determining whether the pollution is due to accumulation in the environment or a genetic selection of resistance.
Interpreting the data
The researchers concluded that the abundance of antibiotic-resistant genes correlated with fecal pollution levels rather than the selection of the resistant gene. Indian sediments had the highest occurrences of pollution due to high levels of pharmaceutical production. Hospitals and wastewater treatment plants had the highest occurrence of pollution throughout the United Kingdom and Singapore.
The researchers also concluded that wastewater treatment plants were highly effective at removing antibiotics from treated water. No longer being a viable carrier of antibiotic-resistant genes, this water would then be considered safe for expulsion. Release points of concentrated fecal matter tend to be hotspots for antibiotic accumulation. The result is a greater concentration of antibiotic-resistant genes.
Potential for future findings
This study is important beyond the concern for human health. Researchers are now looking to identify other fecal phage markers in livestock. Replication of this study could then determine if animals can pass antibiotic resistance on to human or other animals. It may also lead to the determination and regulation of sludge release levels in agriculture.
The Journal of Nature Communications released the full study on the Nature.com website.