"It only delivers nitric oxide. The rest remains trapped in the material, which can be washed out of the wound," Mascharak said. "We think it could be used as a sprayable powder for treating battlefield wounds."
Acinetobacter baumannii has earned the nickname "Iraqibacter" because it has caused so many serious infections in soldiers wounded in Iraq. Some strains of the bacteria are resistant to virtually all antibiotics. Mascharak's lab tested their compound against a strain, isolated from a soldier injured in Afghanistan, that showed resistance to nine of 11 antibiotics tested.
To test the photoactive compound, the researchers developed a laboratory model of skin and soft-tissue infections. A standard antibacterial assay involves growing bacteria on the surface of an agar plate (a petri dish with a layer of firm, gelatin-like growth medium). In an infection, however, bacteria are not only on the surface but also deeper within the skin or soft tissues. "We realized that there wasn't a good model for in vitro testing of antibiotics against soft-tissue infections," Heilman said.
To more closely mimic the conditions in an infected wound, Heilman mixed bacteria into a warm solution of "soft brine agar" and poured that onto agar plates to solidify. The bacteria then grew throughout a 1.1-millimeter-thick layer of soft agar, allowing growth and colonization to occur in a manner similar to that seen in skin and soft-tissue infections.
Heilman then applied the aluminosilicate powder, with and without the photoactive manganese nitrosyl compound, to a defined area of the plates before shining visible light on them. The released nitric oxide effectively cleared the bacteria from the tr
|Contact: Tim Stephens|
University of California - Santa Cruz