While in Ghana last October for the Fleming Fund Fellows kick off meeting, I met Prof Frank Aarestrup from the Technical University of Denmark who told me about a fascinating metagenomics project looking at AMR genes in sewage from across the globe. I was aware of his previous study looking at AMR genes in airplane sewage to look for the spread of MDR pathogens and they have subsequently looked for viruses. 
 
The rationale for looking in sewage is that current AMR surveillance focuses on a select bug-drug combinations mainly based on passive reporting of phenotypic laboratory results for specific pathogens isolated from human clinical infections. Urban sewage provides sampling from a large and mostly healthy population, which otherwise would not be feasible to monitor, does not require informed consent and has precedent in being useful for surveillance in the global polio eradication program.
 
This new study they used characterized the bacterial resistome from 79 sites in 60 countries and combined with AMU data. The study showed that by AMR gene abundance samples split in to two clusters; high-income countries in Europe/North-America/Oceania constituting one cluster and low-income countries in Africa/Asia/South-America constituting another cluster. The countries with most divergent distribution of AMR genes were Vietnam, India, and Brazil, which the authors suggest could be hot spots for emergence of novel AMR mechanisms.
 
Although the human air travel study by the authors showed that AMR genes are rapidly disseminated globally in this study it had no significant influence on AMR abundance.  Interestingly the authors noted that the total AMR abundance was highly correlated with a limited number of World Bank variables, mainly concerning sanitation suggesting local/national parameters paramount in establishing AMR genes in the population. These findings suggest that improving sanitation, health, and perhaps education should be the main strategy for limiting the global burden of AMR.
 
While this study has obvious limits this is an interesting attempt to look at the global picture and will be further improved with additional samples, especially bringing in environmental and agricultural samples.