A woman has been killed by a superbug that proved resistant to every antibiotic available in the US, the Centers for Disease Control and Prevention (CDC) has said.
The Nevada woman's condition was deemed incurable, and 26 different antibiotics were tested in vain before she died in September.
She was in her 70s, and had recently returned to the US after an extended visit to India, according to the CDC's Morbidity and Mortality Weekly Report. She had been hospitalised there multiple times before returning to the US and being admitted to an acute care hospital in Nevada in mid-August.
One week later local health authorities were notified that every possible medication had been tried without success. The CDC later determined that no drug currently on the market would have stopped the bacteria's spread.
"It was tested against everything that's available in the United States ... and was not effective," Dr Alexander Kallen, one of the report's authors told Stat, the health news website which first reported on the discovery of the superbug.
"I think it's concerning. We have relied for so long on just newer and newer antibiotics. But obviously the bugs can often [develop resistance] faster than we can make new ones," he added.
The sample sent to the CDC was found to contain New Delhi metallo-beta-lactamase (NDM), an enzyme that makes bacteria resistant to many antibiotics.
According to the CDC, "pan-resistant" bacteria are very uncommon, and "infection control contact precautions" are important in such situations, meaning patients will be isolated.
A different superbug was found in at least four patients in the US last year. It was found to be resistant even to colistin, considered the last resort among antibiotics because of its harmful side effects.
Fortunately that bug, known as mcr-1, was not found to be highly contagious.
The CDC considers antimicrobial resistance "one of the most serious health threats" currently facing the US.