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Health Capsules
October 2006
Insight into Ear Infections

Chronic infection or inflammation of the middle ear, the area just behind the eardrum, is a common problem for children.  Technically called otitis media, this problem affects 3 of every 4 children at least once by their third birthday.  Almost half of those who get them will have 3 or more ear infections during their first 3 years.  A new study shows why the problem can be so persistent: bacteria can form a “biofilm” on the middle ear that helps them resist both the body’s defenses and antibacterial treatments.

A biofilm is a rich community of bacteria attached to a surface by sugars that the bacteria produce.  The structure created by the bacteria protects them from the body’s defense system.  Bacteria deep within the biofilm can also enter a metabolic state that makes antibiotics ineffective.

Previous studies showed that a biofilm grows on the middle-ear mucosa (MEM)—a mucus-secreting membrane in the middle ear—in chinchillas with otitis media.  Researchers funded by NIH wanted to see whether children with chronic otitis media also have biofilms on their MEMs.

The researchers took MEM biopsy specimens from 26 children, from 2½ to 14 years old, who were undergoing a surgical treatment for chronic otitis media.  For comparison, they took MEM specimens from three children and five adults undergoing another surgical procedure for the ear unrelated to otitis media.  They then looked at the samples using a high-tech microscope that uses laser light to produce a three-dimensional image of a specimen.

The researchers saw biofilms in 92% of the samples from children with otitis media.  They confirmed the presence of disease-causing bacteria in the biofilms.  In contrast, they didn’t see biofilms in specimens from the people without otitis media.

This study supports the idea that chronic cases of otitis media, so common in children, are caused by the formation of biofilms.  Recent research suggests that biofilms may also play a role in other types of chronic human infections.  In order to develop better treatments for such infections, researchers are now investigating how bacteria form biofilms, and how these structures help them to resist both the body’s defenses and antibiotic treatments.

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  Molecules in Blood Signal Preeclampsia

High levels of 2 proteins in the blood of pregnant women may be a warning sign of preeclampsia, a life-threatening complication of pregnancy.

Preeclampsia often occurs without warning.  It may begin with mild symptoms, but can progress to severe preeclampsia and then to eclampsia—dangerously high blood pressure and convulsions.  When preeclampsia is not severe, the high blood pressure it causes can usually be treated in the short term.  Unfortunately, the only cure for preeclampsia is delivery of the baby.

The levels of two proteins circulating in the blood called sFlt1 and PlGF appear to be involved in the development of preeclampsia.  Another protein called endoglin acts together with sFlt1 to induce a severe preeclampsia-like syndrome in pregnant rats.  Researchers thus set out to see whether endoglin might also be associated with preeclampsia in women.

They found that levels of endoglin were significantly higher in those women who, 2-3 months later, went on to develop preeclampsia.  An increased level of endoglin was usually accompanied by increased levels of sFlt1.  The risk of preeclampsia was greater for those women with the highest levels of both, but not for either alone.

High levels of both endoglin and sFlt1 early in pregnancy might be a useful early sign of preeclampsia.  However, attempts to develop drug treatments targeting these proteins need to proceed carefully.  Restoring normal blood pressure and blood flow to the mother could potentially harm the fetus.

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