Thousands of children are diagnosed each year with hydrocephalus, a condition in which the body can’t properly drain the fluid that builds up around the brain. Physicians commonly treat hydrocephalus by implanting a shunt in the brain to carry the excess fluid to other parts of the body.
Shunts save lives, but too often they also lead to infections that can require multiple surgeries and leave patients hospitalized for weeks.
Physicians don’t know why shunt infections are so common, or why they sometimes come back over and over again. But an investigator at Seattle Children’s Research Institute may have found a clue to this longstanding mystery.
In a study published today in PLOS ONE, Tamara Simon, MD, MSPH, and her colleagues outline a discovery that could help understand, treat and prevent future infections. Researchers used genetic sequencing to conduct the first-ever inventory of microbiota – the complex assortment of bacteria and fungi – found in the cerebrospinal fluid of eight children with shunt infections. They identified a surprisingly large and diverse variety of pathogens, including many never before associated with shunt infections. This suggests that many different pathogens may conspire to drive the infections.
“We’ve always thought shunt infections were caused by a single organism that’s raging out of control,” said Simon, a principal investigator in the Center for Clinical and Translational Research at Seattle Children’s Research Institute, and assistant professor at the University of Washington. “Now we’re learning that maybe our whole model of thinking should change, and that there might be something we can do to prevent these infections altogether.”
Biofilms may contribute to shunt infections
Simon’s team identified more than 100 organisms in the cerebrospinal fluid samples they examined, including methylopbacterium jeotgali and species of paenibacillus and bacillus. Simon suspects that the presence of biofilms – diverse communities of organisms that grow on shunts and other medical devices – may explain not only the unexpectedly large number of pathogens, but also why many of them haven’t previously been linked to shunt infections.
The organisms in biofilms live on a device’s surface and many of them go in and out of dormancy. This means they can’t be detected by the bacterial cultures doctors use to pinpoint the cause of a shunt infection. Those cultures identify only bacteria that are free-floating and actively proliferating, and don’t detect fungi.
Simon’s research could help uncover why shunt infections can persist even when they’re treated aggressively. Shunt infections account for up to 2,400 pediatric hospital admissions each year in the U.S., and between 12 and 26 percent of children will suffer a reinfection.
The most common treatment is to temporarily remove a patient’s shunt and deliver intravenous antibiotics for days or weeks. But the antibiotics that doctors select are aimed at only the pathogens they find in the cultures, and not the broader set of organisms that Simon’s team identified.
“If we tailor treatment to just one organism, we might miss the problem of this underlying mass of biofilms,” Simon said.
Pursuing better treatments
Simon and her colleagues recommend physicians use a broader set of cultures – including cultures that detect fungi and anaerobic bacteria – when evaluating shunt infections.
Simon hopes to follow up this study with a similar one looking at a much larger number of patients. If her research confirms biofilms contribute to shunt infections, it could lead to innovative ways to treat those infections – or prevent them entirely.
Researchers could investigate the possibility of preventing infections by putting antibiotics on a shunt before it’s implanted. Or when shunts are reinserted after a patient is treated for an infection, researchers could examine whether moving the shunt to another area of the brain could stop the infection from coming back.
“Our study is just a first step,” Simon said. “But if we keep finding diverse organisms on shunt biofilms, it could help us find ways to reduce infection risk – and that’s really exciting.”
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