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Does Caffeine Affect Bacteria?

author image Beth Greenwood
Beth Greenwood is an RN and has been a writer since 2010. She specializes in medical and health topics, as well as career articles about health care professions. Greenwood holds an Associate of Science in nursing from Shasta College.
Does Caffeine Affect Bacteria?
Caffeine has demonstrated some antibacterial activity. Photo Credit thawornnurak/iStock/Getty Images

Caffeine is an alkaloid of several plants, most notably Coffea arabica, from which coffee beans are harvested, and Camellia sinensis, which produces the leaves used for tea. You may be accustomed to thinking of caffeine as something you drink in coffee or perhaps take as a headache medicine, but caffeine is not only a drug. It helps protect the young tissues of the coffee plant from insect larvae and beetles. Caffeine also has an effect on some bacteria.

Caffeine versus Antibiotics

Caffeine has been tested for potential antibacterial effects on a number of bacteria. In research reported in the April-June 2011 “Journal of Global Infectious Disease,” caffeine and theophylline, which are both plant alkaloids, were tested against the antibiotics ampicillin sodium and cefotaxime sodium. Seven different bacteria, including species of staphylococcus, enterobacter, salmonella and E. coli, were used in the tests. At a concentration of 10 milligrams per milliliter, caffeine was more effective at inhibiting most of the bacterial strains than was the antibiotic ampicillin.

Caffeine at Low Concentrations

Another study reported in the 2009 “International Journal of Green Pharmacy” found caffeine to be even more effective against several strains of bacteria. The bacteria were all described as pathogenic – capable of causing disease. Strains tested included Staphylococcus aureus, Bacillus cereus, Escherichia coli , Proteus mirabilis , Klebsiella pneumonia and Pseudomonas aeruginosa. At only 2 milligrams per milliliter, purified caffeine from both coffee and tea plants showed antibacterial activity against all the bacteria tested.

Caffeine as a Food

Some bacteria can actually use caffeine as food. Caffeine contains carbon atoms, which some bacteria use for their nutritional requirements. The April-June 2011 article in the “Journal of Global Infectious Disease” reports that the bacteria Pseudomonas putida is able to remove and utilize 20 percent of the caffeine incorporated into culture media. The caffeine degradation takes about nine hours of incubation, and the bacteria uses caffeine as its sole source of carbon and nitrogen.

Making Bacteria Caffeine-Resistant

In another study reported in the 2008 issue of the “Research Journal of Microbiology,” researchers found that when caffeine was added to cultures containing E. coli, the bacteria grew long filaments. Other species of bacteria split apart when exposed to caffeine. The researchers found that by injecting bacteria not normally resistant to caffeine with material from bacteria that degraded or consumed caffeine, the injected bacteria could be made caffeine-resistant.

Caffeine and Oral Bacteria

Caffeine can inhibit some bacteria in the lab, but an experiment in the June 2008 “Canadian Journal of Microbiology” indicates it may not always have the same effect on all bacteria. Researchers evaluated the effects of several substances, including caffeine, on common oral bacteria. In these experiments, the caffeine showed no indication that it inhibited any of the bacteria, nor did any of the bacteria show any signs that they could consume the caffeine.

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