From the Department of Medical Microbiology and Infectious Diseases, University Medical Center, Amsterdam (J.K.), and the Laboratory for Microbiology and Infection Control, Amphia Hospital, Breda (J.K.), The Netherlands; and the Infection Control Program, University of Geneva Hospitals and Medical School, Geneva, Switzerland (S.H.). Received March 9, 2009; accepted March 11, 2009; electronically published June 3, 2009. Infect Control Hosp Epidemiol 2009; 30:633-635 2009 by The Society for Healthcare Epidemiology of America. All rights reserved. 0899-823X/2009/3007-0003$15.00. DOI: 10.1086/599020 Approximately 100,000 invasive methicillin-resistant Staphylococcus aureus (MRSA) infections occurred in 2005 in the United States, and the number of associated deaths was estimated at 19,000, which is more than the corresponding annual number of associated deaths for human immunodeficiency virus (HIV) and AIDS. With the increasing number of community-onset MRSA infections, prevention of staphylococcal infections is now more important than ever. For more than 50 years, it has been known that carriage of S. aureus plays an important role in the pathogenesis of staphylococcal infections and represents a potential target for preventive interventions. One of the first reports (1952) that clearly demonstrated the relationship between S. aureus carriage and subsequent infection involved miners who experienced beat disorders of the knees and elbows. A carefully performed microbiological survey showed that there were 24 “heavy” carriers of S. aureus among 45 beat case patients, compared with 5 heavy carriers among 45 matched control subjects without disease (odds ratio, 9.1 [95% confidence interval {CI}, 3.1–26.5]). Phagetyping showed that, in the majority of cases, the carriage strain matched the strain that caused disease. Hospital-based studies in the 1950s and 1960s confirmed this relationship, especially for surgical patients. More recently, these studies have been repeated in various other patient populations—for example, dialysis patients, patients with HIV, organ transplant recipients, and critically ill patients with intravascular catheters—with similar results. It seems obvious that eradication of S. aureus carriage can reduce the risk for infection. This strategy has been studied in several groups of patients, and a recent Cochrane review aggregated the evidence with regard to the effect of eradication of carriage on the S. aureus infection rate. Eight randomized controlled trials studied the effect of mupirocin nasal ointment in various groups of patients. The pooled estimate showed a significant reduction of the S. aureus infection rate (relative risk [RR], 0.55 [95% CI, 0.43–0.70]; ). An P ! .001 analysis of subgroups showed a pronounced effect on surgical patients and on patients who were receiving dialysis, and this fact confirms results of a previously published systematic review. Recently, a large trial was completed in which patients were screened on hospital admission for S. aureus nasal carriage by means of a 2-hour polymerase chain reaction–based assay, and carriers were subsequently randomly assigned to mupirocin nasal ointment and chlorhexidine skin washings or to placebo. The treated carriers had a significantly lower S. aureus infection rate (RR, 0.42 [95% CI, 0.23–0.75]). In addition, the length of hospital stay was significantly shortened for the group of treated carriers (mean reduction of the length of stay, 1.8 days; ). Despite the evidence that P p .04 treatment of proven carriers lowers the S. aureus infection risk, there are several issues remaining. Patients who underwent elective surgery were probably the most important group to benefit from treatment of proven carriers. Because most studies of surgical patients have included both S. aureus carriers and S. aureus noncarriers, it is difficult to assess the overall effect of treatment of proven carriers. Moreover, some studies have found that the infection rate caused by microorganisms other than S. aureus was significantly higher among patients treated with mupirocin, compared with that for control subjects (RR, 1.38 [95% CI, 1.11–1.72]). This finding was based mainly on one large study of dialysis patients who were treated repeatedly. Compared with suppression or eradication of carriage of methicillin-susceptible S. aureus, suppression or eradication of MRSA carriage remains a more difficult task. Rather than being related to pathogen-associated factors that are not fundamentally different between most methicillin-susceptible S. aureus and MRSA clones, the frequent failure of eradication treatment is related to common characteristics of MRSA carriers, such as skin lesions, catheters, and comorbidities, that make MRSA
Read full abstract
Aug 1, 2010
Yuan Hu + 20
Open Access
