A rare but aggressive strain of multi-drug-resistant E. coli bacteria, dubbed E. coli ST131, could be responsible for up to 1 million bladder infections and for more than 3,000 deaths a year from infections that started out in the urinary tract, estimated Dr. James R. Johnson, an infectious disease expert at the Veterans Affairs Medical Center in Minneapolis.
"I think it’s high time to worry," said Johnson, who adds that the new strain is one resistance gene away from being untreatable. "Before, resistant strains were wimpy. Now, we have a winner."
Most people think of E. coli as a diarrhea-causing gut bug that harms people who eat tainted hamburger or spinach. But E. coli that occurs outside the intestine is far more common — and causes far more infection and death, Johnson said.
Extra-intestinal E. coli is responsible for about 80 percent to 90 percent of the urinary tract infections that occur annually. Most respond to common treatments: guzzling gallons of water, swilling quarts of cranberry juice, and, if all else fails, heading to the doctor for a quick course of antibiotics.
But in a recent study based on a national sample, Johnson found that although the E. coli ST131 strain accounted for only about 17 percent of E. coli isolates overall, it accounted for more than 50 percent of bacteria resistant to more than one antibiotic, including the top two types used to treat most urinary tract infections, or UTIs.
It also was responsible for nearly 70 percent of resistance to the biggest guns of mainline UTI treatment, fluoroquinolones and extended-spectrum cephalosporins.
E. coli ST131 is included in a category of E. coli bacteria that produces enzymes that disable antibiotics, known as extended-spectrum beta-lactamase, or ESBL, bugs thought to cause the hardest-to-treat infections. A few years ago, ESBLs were rare, noted Dr. Thomas “Mac” Hooton, a professor of medicine and infectious disease expert at the University of Miami.
"Now, ESBL is like a second-language," Hooton said. "I guarantee you that this will be something we’re seeing in five or 10 years and it will be all over the place."
The E. coli ST131 findings add to the growing concerns about drug-resistance in common infections such as UTIs. For nearly two decades, doctors and scientists have watched — and worried as resistance mounted.
First came the trimethoprim-sulfamethoxazole or TMP/SMX drugs, brands such as Septra and Bactrim, which fell out of favor when they started developing resistance, now gauged to be about 20 percent, doctors say. Then came the fluoroquinolones, the stronger, widely prescribed drugs such as Cipro and Floxin, which were once invincible, but now show overall resistance in perhaps 10 percent of cases in some places, though the level can vary widely.
The vast majority of those who get urinary tract infections — typically young, healthy women who’ve become sexually active — will continue to be treated as they always have. They’ll likely receive a TMP/SMX antibiotic such as Septra or Bactrim or a prescription for nitrofurantoin, an old-line UTI drug, known as Macrobid or Macrodantin, which is back in favor because resistance remains very low.
But more young women — perhaps 1 in 10, Owens estimated — might find that the first drug they take doesn’t work. And maybe the second drug won’t work, either.
In some of those cases, or for patients who’ve taken antibiotics previously, or those who have other health problems, the situation could get serious. Their infections may become chronic, or they may worsen markedly, requiring hospitalization and aggressive treatment. In very rare cases, the infections could become life-threatening or even deadly.
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