First Line of Defense

Last fall’s announcement that virulent antibiotic-resistant staph infections had killed almost 19,000 patients in American hospitals and nursing homes in 2005 didn’t surprise George Allen. With colleagues David Bearden and Mark Christensen, the assistant professor in the OSU College of Pharmacy studies antibiotic effectiveness.

He focuses on a class of broad-spectrum antibiotics known as fluoroquinolones, which includes more than 30 drugs used against infections such as Legionnaires’ Disease, gonorrhea and hospital-acquired pneumonia. Some are used to treat methicillin-resistant Staphylococcus aureus, or MRSA, the culprit behind the Centers for Disease Control and Prevention announcement, and related strains known as community-associated MRSA (CA-MRSA).

CA-MRSA is more susceptible to a range of antibiotics than is hospital-acquired MRSA, says Allen. But, the optimal antibiotic for CA-MRSA infections is unknown. Moreover, the future risk of resistance to the fluoroquinolones and other antibiotics is poorly understood.

So in his lab, Allen and his students pump varying levels of antibiotics into solutions that contain infectious bacteria. For each antibiotic, they calculate the kill rate and test for the presence of newly acquired resistance. Using a novel concept called the mutant prevention concentration, they calculate the lowest effective dosage that will kill bacteria and avoid causing mutations that lead to resistance.

Allen has found that the fluoroquinolone moxifloxacin is effective in reducing further resistance in a certain strain of CA-MRSA, results that he presented at the 2006 annual meeting of the Society of Infectious Diseases Pharmacists. At the 2007 American College of Clinical Pharmacy annual meeting, one of Allen’s former doctor of pharmacy students, Cynthia Hankins, received the Best Student Poster award for her work on Neisseria gonorrhoeae, the bacterium that causes gonorrhea, for which few effective treatments exist.

Allen, Bearden and Christensen are also evaluating the effectiveness of a topical antiseptic, StaphAseptic, developed by Tec Laboratories of Albany, Oregon. They have found that StaphAseptic is more effective than two commonly available topical disinfectants against CA-MRSA.