Daily Chlorhexidine Use in Patients with MRSA Does Not Increase Antibiotic Resistance

According to a recent study published online by the journal Infection Control & Hospital Epidemiology, patients admitted to an intensive care unit (ICU) and bathed daily with chlorhexidine (CHG) were found to have higher prevalence of qacA/B genes in methicillin-resistant staphylococcus aureus (MRSA) isolates recovered from anterior nares. However, the study found no evidence that long-term daily use of CHG led to high levels of antibiotic resistance in bacteria on patients’ skin.

Researchers from Washington University of St. Louis (WUSTL) performed a retrospective cohort study of patients admitted to the ICU at Barnes-Jewish Hospital in St. Louis from 2005 through 2012, reviewing 504 randomly selected isolates of MRSA from surveillance cultures to determine drug resistance resulting from daily CHG use. CHG is an antibacterial soap commonly used for patient body washing in hospital settings.

Based on the findings of several meta-analyses, up to 30 percent of all patients admitted to ICUs in US hospitals develop a hospital acquired infection. Earlier research has demonstrated that CHG helps reduce the incidence of MRSA infections in hospitalized patients by as much as 20 percent. However, to date, little is known about the effects of daily CHG use on the prevalence of the qacA/B genes, which are known to increase to resistance to CHG in MRSA isolates.

Among the 504 randomly selected isolates in the WUSTL study (184 of which—36.5 percent—were SCCmec type IV), 7.1 percent (n=36) were qacA/B positive and 6.9 percent (n=35) were resistant to mupirocin, a topical antibacterial agent. During the study period, the authors identified a significant upward trend in the prevalence of qacA/B at one point, with prevalence increasing from a low of 1.5 percent in 2009 to a high of 16.9 percent in 2009-10; by the final year of the study period (2012), however, prevalence had declined to 7.7 percent. The highest prevalence of SCCmec type IV—52.4 percent—was recorded in 2012. Among the study population, patients with qacA/B-positive MRSA isolates were more likely to be resistant to mupirocin (25 percent) than those with qacA/B-negative isolates (5.6 percent).

In general, the authors attributed the increased prevalence of resistant MRSA isolates at various points during the study to patients entering the ICU already colonized with qacA/B or SCCmec type IV, perhaps as a result of exposures during prior admissions. In their concluding remarks, they noted that further research to evaluate the effects of universal CHG daily bathing on MRSA qacA/B genes among hospitalized patients is needed before any recommendations can be made regarding the future role for the cleaner. Given the lack of evidence for the development of antibiotic resistance in patients bathed daily with CHG, the authors see no need for hospitals to discontinue its use at present, based on their findings.

In a statement released at the time of study publication, lead author and Associate Professor of Medicine in the Division of Infectious Diseases at WUSTL and Hospital Epidemiologist at Barnes-Jewish Hospital in St. Louis David Warren, MD, MPH, said, “There has been concern in the healthcare community about the impact of routine, daily CHG bathing on fostering the spread of bacteria resistant to this agent. We did not see sustained increase in MRSA resistant to CHG [in our study].”

Brian P. Dunleavy is a medical writer and editor based in New York. His work has appeared in numerous healthcare-related publications. He is the former editor of Infectious Disease Special Edition.