OHSU School of Dentistry Examines Antimicrobial Drug Interactions

PORTLAND, Ore.—Researchers at the Oregon Health & Science University School of Dentistry have found that a light-detecting biosensor system can quickly and effectively determine whether antibacterial treatments are working in patients with periodontitis, a serious gum infection that can cause tooth loss and is associated with an increased risk of heart attack or stroke and other serious health problems.

The OHSU team also found that the anesthetics lidocaine and prilocaine, and the antiseptic chlorhexidine do not interfere with the antibiotic minocycline hydrochloride when it is used to treat periodontal disease, and that the drugs can actually complement the antimicrobial activity of such treatment.

The study comprises chapter five of the newly published “Periodontitis: Symptoms, Treatment and Prevention,” a collection of articles for dental and periodontology professionals and students. The book was released Oct. 1 and is available at novapublishers.com/catalog/product_info.php?products_id=11901.

Plaque-induced periodontitis—or inflammation of the gingiva with loss of tissue and bone—is typically treated non-surgically by scaling and root planing. An adjunct non-surgical therapy is the use of the antibiotic minocycline hydrochloride, which can be delivered directly into tooth pockets. The antiseptic chlorhexidine is typically used as a mouth rinse in conjunction with such antibiotic therapy. The anesthetics lidocaine and prilocaine are often applied directly to tooth pockets for numbing prior to scaling and root planning.

The goal of the OHSU study was to use a light-generating gene for development of an oral bacteria biosensor, and then examine the effect of minocycline hydrochloride either alone or in combination with lidocaine/prilocaine or chlorhexidine.

The OHSU team found that minocycline hydrochloride produced quick and effective results in treating periodontal infection. When lidocaine and prilocaine were added to the minocycline hydrochloride regimen, there was no interference with the potent antibacteriostatic activity of minocycline hydrochloride, but actually an additive antibacterial effect. The chlorhexidine rinse, in conjunction with either high or low doses of minocycline hydrochloride, also had an additive effect.

“We were pleased at the sensitivity of the bioluminescence-generating lux gene in the bacterial transformants and its use in determining antimicrobial activity. The biosensor system also allowed us to rapidly monitor inhibition of bacterial metabolism, which is promising,” said Curt Machida, Ph.D., principal investigator and professor of integrative biosciences and pediatric dentistry in the OHSU School of Dentistry. Machida’s lab also hosted the study.

The OHSU team included Machida; Viet Ton That, D.D.S., 2009 periodontology graduate; Sarah Nguyen, D.M.D. `04, third-year periodontology resident; David Poon, research assistant; Shawn Monahan, fourth-year dental student; Rebecca Sauerwein, second-year medical student; Dan Lafferty, research assistant and first-year dental student; Marie Teasdale, research assistant; Amanda Rice, fourth-year dental student; Winthrop Carter, D.D.S., periodontology department chair; Tom Maier, Ph.D., assistant professor of integrative biosciences and oral pathology and radiology.