The U.S. Centers for Disease Control and Prevention revealed on Thursday that an outbreak of bacterial infections occurred in people who received stem cell injections.

Bacterial Infection Outbreak

The CDC said that at least 12 patients in Arizona, Florida, and Texas were hospitalized after getting shots of stem cells derived from umbilical cord blood to treat problems such as back pain and joint pain.

Of the 12 patients, three were hospitalized for a month or longer. None died.

Contamination did not likely occurred at the clinics that gave the shots because investigators found bacteria in unopened vials provided by Liveyon, a California-based distributor of stem cell products manufactured by Genetech laboratory.

Liveyon voluntary recalled the stem cells in October after the U.S. Food and Drug Administration received reports of adverse reaction.

"The decision to stop shipment of Genetech products and implement the recall was to ensure the safety of all patients, regardless of whether the adverse reactions were product- related or the result of any procedural misuse of the product." the FDA said in a statement announcing the recall.

Last month, the FDA warned Genetech that it should not market the stem cells without regulators' approval. The agency also said that the small San Diego company has deviated from manufacturing requirements in a manner that could lead to bacterial contamination.

Stem Cells As Treatment For Diseases

Stem cells have the unique ability to develop into specialized cells such as bone cells, blood cells, and brain cells. Researchers are interested in these undifferentiated cells because of their potential to treat many diseases.

Earlier this year, scientists in the United Kingdom successfully used stem cell therapy to restore the eyesight of two patients with macular degeneration.

Clinical trials involving more than 100 multiple sclerosis patients also show the potentials of using stem cell treatments to stop fatal condition and improve the symptoms.

Stems cells are currently approved for use in a small number of medical procedures but in recent years, many private clinics started to promote their use for diseases where there is little evidence stem cell treatment can be safely and effectively used.

Last year, FDA announced a crackdown in businesses and doctors promoting stem cell injections for diseases such as arthritis and Alzheimer's disease.