Connection between food and antibiotic-resistant bacteria

New research collaboration between University of California at Berkeley and the Centers for Disease Control and Prevention will study whether food is a significant source of the antibiotic-resistant bacteria that cause urinary tract infections, the most common bacterial infections in the developed world, which disproportionately affect women.

Lee Riley, professor of infectious diseases at the UC Berkeley School of Public Health

''Understanding the role the microbiome plays in antibiotic-resistant infections is necessary to protect the public's health,'' says CDC director Tom Frieden. ''We think it is key to innovative approaches to combat antibiotic resistance, protect patients and improve antibiotic use.''

Treatment of urinary tract infections has become more difficult in recent years because E. coli, the most common bacteria that cause urinary tract infections, have become increasingly resistant to commonly used antimicrobial agents. Researchers do not know how big a role food plays in spreading the antibiotic-resistant forms of the bacteria, which is the key question Riley's team aims to answer.

''Understanding what proportion of multidrug-resistant urinary tract infections are attributable to food sources will change the way we calculate the burden of foodborne disease and the impact of antimicrobial use in food animal husbandry,'' Riley said.

An estimated 11 per cent of women in the United States report at least one physician-diagnosed urinary tract infection per year. Some urinary tract infections are acquired by the introduction of particular strains of E. coli into the bladder during sex, but these infections can also occur when E. coli are ingested, colonize in the intestine and then spread to the bladder.

In 1999, when Riley's lab began investigating how urinary tract infections were acquired, they found that in three geographically diverse communities, a single E. coli strain, called clonal group A, accounted for nearly half of the drug-resistant urinary tract infections in women. The strain was also found in 30 per cent of males in the study. The widespread prevalence of a single strain, which is known to have resistance to common antibiotics, suggested the E. coli was spread by an outbreak and not by sex.

''That was when we first suspected transmission from food,'' Riley said.

Riley's lab at UC Berkeley will coordinate with the CDC to compare the infection-causing E. coli found on campus with the US Food and Drug Administration's meat E. coli database, and then work with the CDC to analyze the data.

''We think that if antibiotics contaminate food, then their potential to cause drug-resistant urinary tract infections is a huge public health issue.'' Riley said.

The CDC awarded $560,000 to the research project, which is led by Lee Riley, a professor of infectious diseases at the UC Berkeley School of Public Health. The study is one of 34 projects the CDC is funding with $14 million through its Broad Agency Announcement to support activities related to the CDC Antibiotic Resistance Solutions Initiative and implement the tracking, prevention and antibiotic stewardship activities outlined in the National Action Plan for Combating Antibiotic-Resistant Bacteria.

The goal of these projects is to find new approaches to combat antibiotic resistance, including research on how the microorganisms that are naturally found in the human body, called the microbiome, can be used to predict and prevent infections caused by drug-resistant organisms.

The new funding will allow Riley's team to continue the investigation they started 17 years ago. The new study seeks to get a clear picture of the influence of food or diet on the spread of multidrug-resistant E. coli that increase a woman's risk for urinary tract infections. In the study, the team will collect urine samples from patients at UC Berkeley's Tang Center (University Health Services) with urinary tract infections to estimate the prevalence of drug-resistant E. coli strains. The researchers will also study the genes of these strains and look for clues about how diet and behavior impact the acquisition of these bacteria. The researchers will then compare E. coli from the patients to E. coli found in locally consumed retail meat to see if there is any overlap.