All of the travelers diagnosed with the life-threatening bacteria, carbapenem-resistant Pseudomonas aeruginosa or CRPA, had undergone invasive medical procedures.
"Infections caused by this particular drug-resistant Pseudomonas are rare in the United States and difficult to treat," the CDC said. Patients typically require long and "complex antibacterial drug combinations and courses" to defeat the infection.
The CDC has confirmed 11 cases, said lead investigator Dr. David Ham, medical officer for the CDC's Division of Healthcare Quality Promotion. Nine occurred between August and November; a case from 2015 was retrospectively identified, and one case is still under investigation.
Nearly half of the infected patients had undergone surgery at Grand View Hospital in Tijuana; the rest had undergone surgeries at other hospitals and clinics in the area. Ten of the procedures were weight-loss surgeries, Ham said.
The CDC says the Mexican government has closed Grand View Hospital "until further notice," but the agency still suggests that travelers not have surgery there until the authorities have confirmed that the drug-resistant bacteria are no longer present.
According to its latest survey of providers, about 72% of the patients who used medical tourism traveled for cancer, spine and other orthopedic treatments, followed by cosmetic and plastic surgery procedures, and cardiovascular and neurosurgeries.
Over 50% of the surgeries cost between $10,000 and $50,000, while 16% were between $50,000 and $100,000, the survey said.
There are significant risks in traveling abroad for medical treatment, the CDC cautions.
"Antibiotic resistance is a global problem, and resistant bacteria may be more common in other countries than in the United States," the agency warns.