Antibiotic-resistant meningitis or severe, long-lasting joint infections: That’s what three U.S. “medical tourists” brought home after seeking out unapproved stem cell treatments in Mexico, according to a new report.

The germ involved in all three cases was Mycobacterium abscessus, explained a team led by Dr. Minh-Vu Nguyen, an infectious disease specialist at National Jewish Health in Denver. 

“Stem cell treatments have been linked to bacterial infections, and procedure-related infection risks associated with medical tourism are known,” Nguyen and colleagues warned in their report.  

All three patients contracted their infections in late 2022 or early 2023, and “as of March 28, 2024, treatment is ongoing for all three,” according to the report. 

According to the U.S. Centers for Disease Control and Prevention, M. abscessus “is part of a group of environmental mycobacteria and is found in water, soil, and dust. It has been known to contaminate medications and products, including medical devices.”

The bacterium typically infects soft tissue under the skin, but can also trigger serious lung infections, as well. 

It’s very difficult to transmit M. abscessus person-to-person, but “people with open wounds or who receive injections without appropriate skin disinfection may be at risk for infection by M. abscessus,” the CDC explained. 

“Infection with this bacterium usually does not improve with the usual antibiotics used to treat skin infections,” it noted.

The cases outlined in the new report began in late 2022, when a Colorado woman in her 30s showed up at two hospitals there with a form of meningitis caused by M. abscessus. In October of that year she’d visited a clinic in Mexico where she received stem cell treatments to purportedly treat her multiple sclerosis.

On returning home, she “subsequently experienced headaches and fevers, consistent with meningitis,” Nguyen’s team reported May 9 in the CDC journal Morbidity and Mortality Weekly Report.

A few months later, in the spring of 2023, physicians at a Colorado hospital treated two other patients found to be infected with M. abscessus. 

One, an Arizona man in his 60s, developed an infection in an elbow joint after returning home from stem cell treatments he received for his psoriatic arthritis at a clinic in Baja California, Mexico. 

A second patient, this time a Colorado man in his 60s, developed an M. abscessus infection in both knee joints “after receiving donor embryonic stem cell injections in both knees for osteoarthritis at a clinic in Guadalajara, Mexico, in October 2022,” the report’s authors said. 

Samples of the bacterium obtained from the first two patients show the strains are highly related. That suggests a common source — even thought the clinics where they received their stem cell treatments were 167 miles apart.  

Still, “attempts to identify the [contaminated] product or gather details about its administration have been unsuccessful to date,” Nguyen’s team noted, and Colorado health officials “attempted to contact clinics that performed the stem cell injections, but received no response.”

No new M. abscessus infections linked to the Mexican stem cell clinics have been detected. 

The bottom line, according to the report’s authors: “Providers and public health agencies need to be aware of the risk for M. abscessus infections from stem cell treatments for indications not approved by the Food and Drug Administration and maintain vigilance for similar cases. They also are advised to provide guidance for persons considering medical tourism.”

More information

Find out more about the hazards of medical tourism at the CDC.

SOURCES: Morbidity and Mortality Weekly Report, May 9, 2024; U.S. Centers for Disease Control and Prevention