Extended-spectrum β-lactamase (ESBL) Escherichia coli (E. coli) is a common cause of urinary tract, bloodstream, and various other infections resistant to commonly prescribed antibiotics. Because different strains exist, knowing where ESBL is spreading more rapidly can give clinicians an advantage in treating an E. coli diagnosis.

Matthew Smith, MD, a fellow in the Health Services Research and Development Service (HSR&D) Iowa City VA Health Care System (ICVA), is first author on a recent paper for Infection Control & Hospital Epidemiology that mapped over the course of a decade where ESBL infections occur, down to the county level. Additional authors include Associate Professor of Geographical and Sustainability Sciences Margaret Carrel, PhD, Professor of Internal Medicine Eli Perencevich, MD, MS, and Associate Professor of Infectious Diseases Michihiko Goto, MD, MSCI.

The article, Spatiotemporal distribution of community-acquired phenotypic extended-spectrum beta-lactamase Escherichia coli in United States counties, 2010–2019, uses an unusually large and detailed data set over a prolonged period of time, a nationwide analysis of ten years’ worth of data from each state’s county.

“Local clinicians and providers in areas with high levels of resistance might change which antibiotics they reach for first when they see an E. coli infection if they don’t yet have data about which antibiotics work best,” Smith said. “For researchers, this data can provide some clues as to where ESBL resistance is developing and how it spreads over time.”

The prevalence of ESBL E. coli in the United States has steadily increased over time, but at a slower pace than in other parts of the world such as Asia where ESBL rates often exceed 20–50%, rather than the 8–10% ESBL rate the team discovered in the study.

“Perhaps that is because of more responsible antibiotic stewardship practices in the US, or a lower population density—it’s hard to say,” Smith said. “The number one driver of antibiotic resistance is simply how much the antibiotic is used. Thus, in general, you tend to see resistance develop in major population centers first.”

Resistance occurred not just in urban areas, but in rural areas, too, leading the team to theorize that antibiotic use in livestock may be another factor driving resistance in rural areas. Although more research would need to be done to establish a link between antibiotic use in livestock and ESBL E. coli, the study does raise the possibility of this phenomenon.