HealthDay News — According to a study published in Clinical Microbiology and Infection, medical marijuana may carry infectious bacteria and fungi that can pose a life-threatening risk to cancer patients who use it to ease the side effects of chemotherapy.

Researchers from the University of California at Davis became aware of this risk when a patient developed a rare and incurable fungal infection after using aerosolized marijuana — raw, blended marijuana inhaled as a mist. 

The patient ultimately died from a lung infection due to the fungus Mucor, according to his physician, Joseph Tuscano, MD, a professor of internal medicine in the Division of Hematology and Oncology at the university. 

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The patient had been using medical marijuana while he was receiving chemotherapy and stem cell therapy for cancer. To test their concern, the researchers had DNA analysis conducted to identify the fungi and bacteria contained in the samples from medical marijuana dispensaries.

Several different families of dangerous fungi were found in the medical marijuana, including Aspergillus, Cryptococcus, and Mucor. Bacteria found in the marijuana samples included Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Pseudomonas fluorescens, Pseudomonas putida, Acinetobacter baumannii, and Stenotrophomonas maltophilia.

The study authors warn against patients using inhaled forms of medical marijuana. They advise patients that consuming marijuana in baked goods is likely the best option, since the high temperatures involved in cooking would probably destroy the pathogens.


Thompson GR, Tuscano JM, Dennis M, et al. “A Microbiome Assessment of Medical Marijuana.” Clin Microbiol Infect. 2016. doi: 10.1016/j.cmi.2016.12.001. [Epub ahead of print]

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