Previously rare form of bacteria now predominates
Pastor Dale Morgan
Previously rare form of bacteria now predominates*
By Anita Manning, USA TODAY
A previously rare form of bacteria that causes ear infections and more
serious illnesses such as pneumonia and meningitis is now the
predominant strain, possibly because a widely used vaccine has knocked
out the competition.
Scientists at a meeting in San Diego of the Infectious Diseases Society
of America reported Friday that in a study of eight U.S. children's
hospitals, a strain of Streptococcus pneumoniae bacteria known as 19A
accounted for nearly half the cases of serious pneumococcal infection in
children.
The pneumonia vaccine Prevnar, routinely given to babies, protects
against seven strains of the bacteria that once caused about 90% of
serious pneumococcal illnesses in children. Since its introduction in
2000, rates of these illnesses have dropped by about 85%, said pediatric
infectious disease specialist Sheldon Kaplan of Texas Children's
Hospital and Baylor College of Medicine, Houston.
But that decline has leveled off in the last three years, he says,
because bacterial strains that are not included in the vaccine,
particularly 19A, are causing illnesses.
In the study, Kaplan says, the eight hospitals reported between 400 and
500 cases of serious pneumococcal disease each year between 1993 and
2000. Cases dropped to a low of 149 in 2004, and the number has crept
steadily up to 177 last year. "That's still a marked reduction," he
says, "but the isolates causing 97% of invasive infections are
non-vaccine types, and 19A is causing half of those."
Why that's happening isn't clear. Wide use of the vaccine could have
created an environment in which 19A could "pick up the slack, or take
over in the nose," where the organisms reside, Kaplan said. About 30% of
people carry pneumococcal bacteria harmlessly in their nose.
But another paper presented at the meeting reported an upswing of 19A in
Korea, where the vaccine is not used, so clearly that was not a factor,
Kaplan says.
An added concern, he says, is that some forms of 19A have developed
resistance to commonly used antibiotics, Kaplan says, though they seem
to be occurring in some countries and regions and not in others.
Vaccine maker Wyeth is testing a new pneumococcal vaccine that contains
13 strains, including 19A, says Peter Paradiso, vice president for
scientific affairs. Clinical trials should be completed by the end of
2008, he says. Other companies also are developing vaccines with more
bacterial strains.
There are plenty to include. Kaplan says there are more than 90 strains
of the bacteria, so researchers are looking at ways to make a vaccine
that targets all of them.
Meanwhile, he says, parents should make sure their kids are immunized,
not only to protect them, but also to prevent infection in others.
Researchers from the Centers for Disease Control and Prevention reported
at the meeting that since the vaccine was introduced, there has been a
75% to 80% reduction in pneumococcal infection — caused by strains
included in the vaccine — of unvaccinated adults.