Research paves way for life-threatening bacterial infection test

EU-funded researchers have demonstrated how a recently identified protein causes a simple bacterial infection to turn into a potentially fatal condition called rheumatic heart disease. The researchers are now using their newfound knowledge to develop a test system that will be able to identify the bacteria when the infection is still in its early stages.

The work, published in the open access journal PLoS (Public Library of Science) ONE, is supported through the ASSIST (Comprehensive approaches to understand streptococcal diseases and their sequelae to develop innovative strategies for diagnosis, therapy, prevention and control) project, which received EUR 1.48 million under the International cooperation budget line of the Sixth Framework Programme (FP6).

Every year, some 600 million people become infected with streptococcus bacteria; most of these people will suffer nothing worse than a sore throat. However, in a small percentage of cases, the infection triggers an autoimmune condition called rheumatic heart disease. Some 15 million children are diagnosed with rheumatic heart disease annually, making it a leading cause of cardiovascular disease in the young, especially in developing countries. Half a million children die of the disease every year.

Only a few strains of streptococcus cause rheumatic heart disease. If the infection is not adequately treated, these bacteria stick to collagen in the body. Collagen is a key component of our bones and cartilage and it strengthens the connective tissue of the skin, heart valves and blood vessels. When the bacteria stick to the collagen, the immune system becomes confused and attacks the collagen along with the invading bacteria, causing a condition known as rheumatic fever.

If left untreated, the heart valves, which are extremely rich in collagen, become inflamed and eventually stop working. At this point, a heart valve transplant may be the only treatment that can save a child's life.

In this latest study, scientists from Germany and Sweden show how a recently discovered protein called PARF, which is found on the surface of the bacteria, helps the bacterial cells to stick to the collagen.

"PARF means 'peptide associated with rheumatic fever'," explained Patric Nitsche-Schmitz of the Helmholtz Centre for Infection Research in Germany. "It is a small section from a bacterial surface protein, which is used by the streptococcus to adhere to our cells and cause disease."

Just 5% of Streptococcus pyogenes strains are able to cause rheumatic fever, and one of the aims of the ASSIST project is to develop a test that can quickly identify the small proportion of patients infected with these strains so that they can receive the intensive antibiotic treatment needed to prevent the development of rheumatic heart disease.

The researchers are now applying their understanding of the PARF protein sequence to develop a test strip that would react to the presence of PARF in a sample.

"We hope that this will soon give us a test system that we can use for examination of children on a routine basis," commented ASSIST project coordinator Professor Singh Chhatwal, also of the Helmholtz Centre for Infection Research. "This would save the lives of a lot of children."

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