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Epidemiologists Blame Overpopulation , Climate Change to High Antibiotic Resistance in US Cities

A large crowd taking pictures beside an aircraft carrier. / Photo by: Bill Perno via Wikimedia Commons
 

A team of epidemiologists from the Boston Children’s Hospital and the University of Toronto in Canada can now definitely say that high local temperature and densely populated cities directly correlate to the high resistance of antibiotics across the US.

The findings were highlighted in the recent issue of Nature Climate Change journal.

It used to be that repeated exposure of patients to antibiotics in common bacterial strain was blamed for developing high antibiotic resistance. Today, the environmental landscape could be the culprit.

"The effects of climate are increasingly being recognized in a variety of infectious diseases, but so far as we know this is the first time it has been implicated in the distribution of antibiotic resistance over geographies," says Derek MacFadden, MD, an infectious disease specialist and research fellow at Boston Children's Hospital and the study's lead author.

The study explained that bacteria which caused infections in humans can acquire resistance to the antibiotics used against them. This antimicrobial resistance in bacteria and also in other microbes were regarded as the culprit in worldwide cases of morbidity. The running estimates showed death cases in the population.

Moreover, the study showed that the combination of climate (temperature), population density, factors on the distribution of antibiotic resistance across the states, and the increasing local temperature all played a significant role in the high capability of antibiotic resistance in common pathogens.

"Population growth and increases in temperature and antibiotic resistance are three phenomena that we know are currently happening on our planet," says Mauricio Santillana, Ph.D. a faculty member in the Computational Health Informatics Program at Boston Children's, an assistant professor at Harvard Medical School (HMS), and the study's co-senior author. "But until now, hypotheses about how these phenomena relate to each other have been sparse. We need to continue bringing multidisciplinary teams together to study antibiotic resistance in comparison to the backdrop of the population and environmental changes."

 

The Investigation

The research process involved collation of a huge database from several sources like hospitals, as well as laboratory and disease surveillance data containing information related to E. coli, K. pneumoniae, and S. aureus. The team focused on the documented period between 2013 and 2015. The information collated comprised.6 million bacterial pathogens culled from 602 records across 41 states and 223 facilities. Records revealed there were increasing prescription rates across geographic areas due to increased antibiotic resistance across the pathogens investigated.

Once this information was established, the team compared the database to the geographic coordinates and climate variation or how the climate fluctuates above or below the average over a period of time. The geographic coordinate system used referred to the three-dimensional spherical surface to locate areas on the earth.

They compared the database to the latitude coordinates against the mean (average temperature), median (middle temperature) and the local temperatures. It became evident that higher local temperatures equated to the strongest antibiotic resistance.

MacFadden stressed, "We also found a signal that the associations between antibiotic resistance and temperature could be increasing over time."

Based on the data, increases of 10°C to the low average temperature of the local area were found in close association with 4.2-percent, 2.2-percent, and 3.6-percent increases in antibiotic resistance to these respective strains -- E. coli, K. pneumoniae, and S. aureus.

John Brownstein, PhD, chief innovation officer and director of the Computational Epidemiology Group at Boston Children's, professor of pediatrics at HMS, and the paper's co-senior author said, "Estimates outside of our study have already told us that there will already be a drastic and deadly rise in antibiotic resistance in coming years,"

He added that “with the findings that climate change could be compounding and accelerating an increase in antibiotic resistance, the future prospects could be significantly worse than previously thought."

When measured against population density, the team equated the increase by 10,000 people per square mile with three to six percent respective increases in antibiotic resistance in E. coli and K. pneumoniae, both gram-negative species. On the other hand, population density appeared to have no effect on the gram-positive S. aureus.

Cefalexin antibiotics. / Photo by: Sage Ross via Wikimedia Commons
 

More Antibiotic Resistance Research

MacFadden pointed out that the transmission factor is the critical angle to pursue further scientific research. "As transmission of antibiotic-resistant organisms increases from one host to another, so does the opportunity for ongoing evolutionary selection of resistance due to antibiotic use."

The study also showed the team’s hypothesis that “the temperature and population density could act to facilitate transmission and thus increases in antibiotic resistance." This particular note would help future research in better understanding the behavior of bacteria and administration of antibiotic treatments to patients.

Brownstein further stressed that "the bottom line is that our findings highlight a dire need to invest more research efforts into improving our understanding of the interconnectedness of infectious disease, medicine, and our changing environment.”

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