Decreasing the occurrence of hospital-acquired antibiotic resistant Staphylococcus aureus infections by reducing the use of a commonly prescribed class of antibiotics.

45th ICAAC
A meeting of the American Society for Microbiology

December 16-19, 2005, Washington, DC
For more information on any presentation at the 45th ICAAC contact Jim Sliwa, ASM Office of Communications at


EMBARGOED UNTIL: Friday, December 16, 3:00 p.m. EST
(Session 51, Paper K-552)
Karl Madaras-Kelly
Idaho State University
Pocatello, ID, United States
Phone: 208-422-1146



Hospital acquired infections caused by Methicillin-resistant Staphylococcus aureus(MRSA) are associated with significant morbidity and mortality. Traditional interventions such as hand washing and isolation of patients with MRSA infections have been effective at containing MRSA in some hospitals, however the overall trend in hospital acquired MRSA infection is increasing nationally.  Previous studies have determined an association between the use of a commonly prescribed class of antibiotics, the fluoroquinolones, and the subsequent development of infections caused by MRSA.   The purpose of this study was to encourage physicians to use other antibiotics in place of the fluoroquinolones in an attempt to decrease hospital-acquired MRSA infections.   Hospital-wide use of fluoroquinolone antibiotics were decreased by 35%, and the rate of hospital acquired MRSA infections declined by about one- half.  Analysis revealed that the intervention to decrease use of fluoroquinolone antibiotics was associated with the reduction in MRSA infections.  


This intervention and analysis was conducted in a small Veterans Affairs hospital in Boise Idaho by a multi-disciplinary  team of infectious diseases practitioners.  The infectious diseases team observed a potential relationship between the use of fluoroquinolone antibiotics and MRSA infections, and designed the intervention.  Dr Madaras-Kelly is an Associate Professor of Pharmacy  at Idaho State University and a pharmacist with expertise in antibiotics.  Pam Lewis is the hospital Infection Control practitioner, and Dr Stevens is a Professor of Medicine for the University of Washington and an Infectious Diseases physician.  Dr Madaras-Kelly designed the intervention and study, Pam Lewis and Dennis Stevens assisted in data collection and implementation of the intervention, and Richard Remmington, adjunct Assistant Professor at Boise State University, a biostatistician, conducted the statistical analysis.  The work was partially (~ 1/3) funded by an unrestricted educational grant from Wyeth Pharmaceuticals.  This work will be presented at the 45th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC), New Orleans, LA on September 21rst, 2005.  In addition, this work was accepted for publication in the journal of Infection Control and Hospital Epidemiology on August 7th, 2005 and is in press.


In May of 2003, The Society for Healthcare Epidemiology of America (SHEA) published guidelines for preventing nosocomial transmission of multidrug-resistant strains of Staphylococcus aureus and Enterococcus .  One of the SHEA recommendations suggested that “institutions with endemic MRSA should consider limiting the use of broad-spectrum antibiotics, especially fluoroquinolones”, based upon previous studies implicating and association between use of fluoroquinolone antibiotics.


In July of 2003, a computer-generated intervention designed to limit the use of inpatient fluoroquinolone antibiotics was implemented at this VA facility.  Text describing the SHEA recommendation related to fluoroquinolone use and MRSA infection was inserted into the electronic physician order entry screen for inpatient antibiotics.


Prior to the intervention, a fluoroquinolone antibiotic called levofloxacin was the most frequently prescribed antibiotic in the hospital.  Nationally, levofloxacin has been the second most frequently prescribed inpatient antibiotic in hospitals over the past several years.  After the  intervention,  the prescribing of all fluoroquinolone antibiotics decreased by ~ 35% with levofloxacin use decreased by about 50%.   Physicians chose to prescribe different antibiotics in place of fluoroquinolones.


After the intervention, health care-associated MRSA infections declined significantly from 1.37 cases / 1000 hospital patient days to 0.63/ 1000 hospital patient days, or about 50%. In the analysis of this intervention 80 infections or about three years of  MRSA  related infections were studied: two years before the intervention and one year afterwards. 


The analysis revealed that the fluoroquinolone levofloxacin was strongly associated with the MRSA infections, and the intervention to decrease use of fluoroquinolone antibiotics was associated with the reduction in MRSA infections.


Despite previous studies identifying fluoroquinolone antibiotics as a risk factor for developing MRSA infections, few studies have been designed to study the impact of reducing exposure to this risk factor. 


Physicians and health care personnel involved in formulating policies relating to hospital-acquired infections and antibiotic prescribing should be interested in the results of this study. This prevention strategy has appeal in that it may be easier to alter prescribing habits as opposed improving health care workers hand-washing practices, a behavior that has been difficult to change.


However there are several potential concerns that need to be considered when interpreting this study.  First, infections caused by other bacteria, which fluoroquinolone antibiotics are usually effective against, increased.  Second, the design of this study  only permitted identification of an association between the fluoroquinolone directed intervention and the reduction in MRSA infections, and does not prove cause and effect.  The intervention needs to be repeated in other health care settings, and further prospective studies are warranted.