Ear Infections Linked to Drug-Resistant 'Superbug'
TUESDAY Oct. 16, 2007 -- An emerging "superbug" that causes ear infections in children and is resistant to multiple antibiotics can only be treated with an adult medication, researchers report.
Two Rochester, N.Y., pediatricians report finding a multiple antibiotic-resistant strain of Streptococcus pneumoniae that caused ear infections in nine children in their practice over three years. The only antibiotic that was effective in treating these infections was levofloxacin, which isn't approved by the U.S. Food and Drug Administration for use in children.
"We found a superbug causing ear infections in Rochester -- the Legacy strain -- that's resistant to all antibiotics approved by the FDA for use in children," said the study's lead author, Dr. Michael Pichichero, a professor of microbiology, immunology and pediatrics at the University of Rochester Medical Center, and a private practice pediatrician with the Legacy Pediatric Group.
The resistant infections accounted for only 1.5 percent of the ear infections in their practice, Pichichero noted.
The findings are published in the Oct. 17 issue of the Journal of the American Medical Association.
Pneumococcal infections are caused by S. pneumoniae, and can include ear infections, sinus infections, pneumonia, meningitis and bloodstream infections. Some of these infections can be life-threatening. Young children are most susceptible to pneumococcal infections, according to the U.S. Centers for Disease Control and Prevention. Fortunately, the serious forms of the disease are rare, causing about 4,500 illnesses each year. However, pneumococcal infections cause more than 3 million ear infections each year, according to the CDC.
While a vaccine (brand name Prevnar) is available that covers seven strains of pneumococcal disease, a strain dubbed serotype 19A isn't currently one of them. However, the vaccine's manufacturer, Wyeth Pharmaceuticals, reports that it's currently in phase III trials of the next generation vaccine, which does include serotype 19A.
"Prevnar is a fantastic vaccine that is taking care of the top seven strains of pneumococcal disease, but after you've knocked down the other strains, of course others will become more prominent," Pichichero explained.
Dr. Peter Paradiso is vice president of scientific affairs for Wyeth Pharmaceuticals. He said, "When we developed Prevnar, we had hoped that the response to serotype 19F would provide some cross-protection against 19A." When it became clear that there was no cross-protection, and other strains needed to be addressed, Wyeth added six more strains to the next generation vaccine. The company plans to begin the regulatory filings needed for FDA approval sometime in 2009, after the phase III trials are completed, he said.
In the meantime, Pichichero said physicians need to do more ear tap procedures to identify which bacteria are causing antibiotic-resistant ear infections. Doing so, he said, would help avoid the unnecessary use of antibiotics and allow for a more targeted approach to treating ear infections.
From 2003 until 2006, Pichichero and his colleagues saw just over 1,800 youngsters with ear infections, according to the study. Of those children, 212 had ear taps, known as tympanocentesis, a procedure that draws fluid out from behind the ear drum. Much like when a tooth cavity is filled, children are given local anesthetic to make the procedure pain-free.
Using this procedure, the doctors found that 59 of the ear infections were caused by S. pneumoniae. One particular strain of the bacterium -- serotype 19A -- had developed a new genotype that was resistant to all of the antibiotics approved for use in children. Pichichero and his colleague, Dr. Janet Casey, dubbed this the Legacy strain. Nine children were found to be infected with this strain.
The only antibiotic effective against this superbug is levofloxacin (brand name, Levaquin). But, levofloxacin has never been approved for use in children. Pichichero said that because previous studies on young animals have suggested that the drug might cause irreversible damage to growing cartilage, the "FDA has put significant barriers for the use of the antibiotics in children." No such effects have been found in adults, and it's a commonly used antibiotic in adults.
However, in these nine pediatric cases, no other treatments were effective, and the children were at risk of losing their hearing. Since Pichichero had been involved in previous research on levofloxacin's use in children, he knew the correct dose to administer, and it was effective.
But, he cautioned, because the drug hasn't been well studied in children, "I would not allow a child to receive levofloxacin unless I knew for sure [that it was the Legacy strain]."
Dr. Katherine Poehling, a pediatrician at Brenner Children's Hospital at Wake Forest University Baptist Medical Center, said the new findings are worrisome, but "nine cases out of 1,800 doesn't make me panic. We've always had some ear infections that are very hard to treat, but they usually aren't serotyped to figure out what they are."
Poehling, who's been involved in research on the current pneumococcal vaccine, added that the "pneumococcal conjugate vaccine has been extraordinarily successful, and children continue to benefit from this vaccine."
Paradiso agreed, adding that the current vaccine has caused a dramatic -- 99 percent -- reduction in infections in the serotypes that are covered by the vaccine.
The CDC recommends that the current vaccine be given to all infants younger than 24 months of age at 2, 4, and 6 months of age, followed by a booster dose at 12-15 months of age.
To learn more about pneumococcal disease in children and the available vaccine, visit the U.S. Centers for Disease Control and Prevention.
Posted: October 2007