It’s a drink most people enjoy every day. But consuming it while taking common antibiotics may raise the risk of being sickened by deadly bacteria.

Scientists from three different nations examined nearly 100 chemical substances and observed their interactions with E. coli, a type of bacteria that can lead to symptoms such as diarrhea, cramps, and vomiting.

Their study revealed that coffee—or more precisely, caffeine—caused E. coli to absorb lower levels of common antibiotics like ciprofloxacin (Cipro), which is often used to treat a range of infections, including those of the urinary tract, skin, and respiratory system.

This makes the antibiotics less effective in treating infections caused by E. coli bacteria, known as antibiotic resistance. 

In some cases, antibiotic resistance makes bacterial infections impossible to treat, increasing the risk of death.

The impact of caffeine was found to be specific to E. coli, which affects over 250,000 Americans annually. However, caffeine did not diminish the effectiveness of antibiotic treatments for other similar bacteria, like salmonella. 

The findings come as about two-thirds of Americans report drinking coffee, one of the most prevalent sources of caffeine, every day along with tea and energy drinks.

The most common source of E. Coli is undercooked ground beef, where bacteria can spread during processing. Leafy greens like romaine and spinach are another major culprit, along with raw milk and other unpasteurized dairy. 

Caffeine in drinks like coffee may lower the effectiveness of common antibiotics, a new study has suggested (stock image)

E. coli bacteria can cause infections leading to bloody diarrhea, stomach cramps, nausea and vomiting.  

Most people recover within a week, but some people can become severely ill and develop a dangerous kidney condition called hemolytic uremic syndrome. 

About 265,000 Americans are sickened by E. coli every year and over 3,000 are hospitalized. The Centers for Disease Control and Prevention report about 61 deaths from the bacteria each year. 

The new study, published last month in the journal PLOS Biology, looked at 94 different chemical substances and their effects on E. coli and salmonella. The substances ranged from antibiotics to prescription drugs to everyday chemicals like caffeine.

The researchers evaluated the effect on transporter genes, which control what enters and leaves cells.

They found caffeine activates the protein Rob, which stops as much Cipro from entering cells, rendering it less effective.

Ana Rita Brochado, study author and biological engineer at the University of Tübingen in Germany, said: ‘Caffeine triggers a cascade of events starting with the gene regulator Rob and culminating in the change of several transport proteins in E. coli – which in turn leads to a reduced uptake of antibiotics such as ciprofloxacin.’ 

The team noted because the experiments were carried out with cell samples, it’s unclear if the same results would be true in human studies. However, they plan to conduct further research.

The study found caffeine affected the antibiotic ciprofloxacin (Cipro), which is filled about 4million times a year in the US (stock image)

It’s also unclear how much caffeine exactly would weaken antibiotics like Cipro against E. coli and if there are specific differences between caffeine sources like coffee and tea. 

Researchers estimate that 4million prescriptions for Cipro are filled every year, making it one of the most common antibiotics in drugs like amoxicillin and doxycycline. 

The researchers wrote: ‘Based on these findings, we foresee a challenging, but unavoidable and important task in mapping key determinants of transport functions across different bacteria.’