Antibiotic Prescribing Habits Have Shifted According to Pathogen Prevalence Patterns

Alice Goodman

September 22, 2010

September 22, 2010 (Boston, Massachusetts) — The choice of which antibiotic to prescribe as initial empiric therapy for hospitalized patients with complicated skin and skin-structure infections has changed substantially over the past decade, suggesting that physicians are responding to an increase in methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, and Gram-negative infections in general. Multidrug use is also much more common than it was 10 years ago, according to a retrospective study reported here at the 50th Interscience Conference on Antimicrobial Agents and Chemotherapy.

The use of vancomycin — the most widely used drug for MRSA — increased dramatically, whereas the use of cefazolin and ampicillin/sulbactam — 2 drugs used to treat methicillin-susceptible S aureus — declined over the same period. Concomitantly, a marked increase was seen in prescribing pipericillin/tazobactam, a broad-spectrum antibiotic covering Gram-negative infections.

"These changes in initial antibiotic therapy in hospitalized patients undoubtedly reflect increasing concern about pathogen resistance and changes in treatment guidelines. Our objective was to see whether physicians are responding to the changing environment in infectious disease, and our study suggests that they are," said senior author David Weber, MD, professor of medicine, pediatrics, and epidemiology at the University of North Carolina in Chapel Hill.

The study used the Cerner Health Facts electronic database to identify 22,832 adult patients hospitalized for complicated skin and skin-structure infections in the United States between 2000 and 2009; 75% were hospitalized for acute infections, 18.3% for infections at the surgical site, and 6.6% for chronic infections.

A marked decrease over time was observed in the use of cefazolin (from 22.1% to 6.9%) and ampicillin/sulbactam (from 19.9% to 6.0%), whereas the use of vancomycin increased 4-fold (from 5.6% to 22.6%), and the use of piperacillin/tazobactam plus vancomycin increased more than 10-fold (from 0.9% to 12.9%. Piperacillin/tazobactam monotherapy increased more than 2-fold (from 2.8% to 6.5%).

Dr. Weber pointed out that the use of vancomycin as either a single agent or as part of a multidrug regimen increased from 16.5% in 2000 to 55.4% in 2009. During that time period, the use of piperacillin/tazobactam either as a single agent or as part of a multidrug regimen increased from 6.8% to 20.9%.

Over the same time period, the use of initial regimens providing coverage for P aeruginosa increased from 16.4% to 28.1%, and antibiotic regimens providing broad-spectrum coverage for Gram-negative infections increased from 22.1% to 36.1%.

Dr. Weber cited several limitations of this study: its retrospective design, the fact that its database might not be generalizable to all American hospitals, and the fact that it provided no information on why initial antibiotics were selected.

Commenting on this study, Vance Fowler, MD, associate professor at Duke University in Durham, North Carolina, said: "Multidrug-resistant pathogens are on the rise in critically ill patients who present to the hospital with life-threatening complications of skin and skin-structure infections. We want to make sure we are choosing antibiotics wisely."

"Physicians have to make an educated guess during the first 24 hours of hospitalization, and they get points for being right. You know antimicrobial resistance is climbing in the hospital setting, and your job is to ensure that the patient in the bed right now has the best chance to get the best therapy out of the gate," he continued.

"This study implies physicians are doing their job," Dr. Fowler stated.

Dr. Weber reports receiving financial support from Policy Analysis Inc and the Forest Research Institute of New York City. Dr. Fowler reports financial ties with Astellas, Cubist, Merck, Theravance, Pfizer, Novartis, Inhibitex, Arpida, Targanta, Wyeth, Ortho-McNeil, Vertex Pharmaceuticals, Leo Pharmaceuticals, NovaDigm, The Medicines Company, Baxter Pharmaceuticals, Biosynexus, and Johnson & Johnson.

50th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC): Abstract L1-1761. Presented September 14, 2010.