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Tuesday, February 9, 2010

Maggot treatment hampered by bacteria

Filed under medical treatments I did not want to know about and certainly did not want to post a picture of:

Lucilia sericata (green bottle fly maggots) have been used since ancient times to clean and heal wounds. The practice was revived in the 1990’s, and is now relatively common, going under the name Maggot Debridement Therapy (MDT). The maggots ingest only necrotic (dead) tissue, effectively cleaning wounds. At the same time, they promote healing and reduce inflammation by secreting antimicrobial compounds into the wound.

Unfortunately, maggots infected with the bacteria Pseudomonas aeruginosa die without completing their wound care tasks. Anders Schou Andersen and his team from the University of Copenhagen in Denmark showed that the inter-bacterial communication system known as 'quorum sensing' was indirectly responsible for the maggot deaths.

Quorum sensing allows bacteria to converge into ‘biofilms’, sheets of cells that stick to surfaces and are exceeding difficult to kill. These bacterial conglomerations also produce potent toxins that kill maggots and other organisms.

When the scientists used genetically modified Pseudomonas without a functional quorum sensing system, the maggots were much less susceptible to the bacteria. It is important to note that the researchers did not protect the maggots by chemically blocking bacterial signaling, but rather relied on mutant bacteria for their tests. The bacteria that patients are likely to encounter during treatment would almost certainly have wild-type (normal) quorum sensing. In order to ensure that MDT is successful, doctors will have to first rid the wound site of pathogenic bacteria, which isn’t always an easy task.