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SSI success story may be undercut in 'real world'
Other New Eng Jrl study endorsed without caveats
By Dean L. Winslow, MD, FACP, FIDSA, Chief, Division of AIDS Medicine, Santa Clara Valley Medical Center; Clinical Professor, Stanford University School of Medicine.
Synopsis: In total, 6,771 patients underwent screening for Staphylococcus aureus nasal colonization using real-time polymerase chain reaction (PCR). Of those, 1,251 patients were positive, 917 were enrolled in the trial, and 808 subsequently underwent a surgical procedure. The enrolled patients were treated with nasal mupirocin ointment plus body chlorhexidine baths (or placebo). Rates of S. aureus infection were 3.4% in the mupirocin-chlorhexidine group vs. 7.7% in the placebo group.
Source: Bode LGM, et al. Preventing surgical-site infections in nasal carriers of Staphylococcus aureus. N Engl J Med 2010; 362:9-17.
In this prospective, randomized, placebo-controlled trial from the Netherlands, 6,771 patients were screened on admission to the hospital for the presence of Staphylococcus aureus nasal colonization using real-time PCR. Of those, 1,251 patients were positive for S. aureus and 917 were included in the intent-to-treat analysis. A total of 808 underwent a surgical procedure. Staph strains identified in this study were all methicillin- and mupirocin-susceptible. Patients were randomized to twice daily intranasal mupirocin (vs. placebo) plus daily baths with chlorhexidine scrub (vs. placebo soap) for five days beginning shortly after admission. The rate of S. aureus infections was 3.4% in the mupirocin-chlorhexidine group and 7.7% in the control group.
The beneficial effect of decolonization was most pronounced for deep surgical-site infections (four vs. 16). No difference in overall mortality was seen between the groups; however, three patients who underwent cardiothoracic surgery and developed staph infections died. Hospital length of stay was significantly shorter in the intervention vs. control group (12.2 vs. 14 days). Molecular typing of isolates obtained from wound infections was performed, and the results were compared to the pre-treatment nasal isolates from the same cases to determine whether the infection was of endogenous or exogenous origin. Twelve endogenous infections were seen in the decolonization group vs. 25 in the control group. Four vs. six exogenous infections were seen in the decolonization vs. control groups, respectively.
This is an important study that demonstrates that rapid screening using PCR can identify a population of patients where relatively simple and benign interventions can have a significant impact on a clinical outcome. The use of both intranasal mupirocin plus chlorhexidine scrubs was important for the simultaneous elimination of both nasal and extranasal carriage. The study nicely demonstrates positive results in the context of a carefully controlled experimental design.
However, it is likely that, in the real world, results might not be as positive for several reasons. These include the difficulty of performing five consecutive days of decolonization immediately prior to surgery in all cases, particularly when surgery is urgently performed. It is not known whether shorter periods of decolonization would be as successful, since only a small number of patients in this study had surgery performed during the first five days of hospitalization. The authors also mention that in patients who had prolonged hospitalizations, repeat decolonizations might be necessary. Another concern is that the increasing prevalence of mupirocin resistance in S. aureus, which has sbeen shown to limit the effectiveness of mupirocin decolonization, might make this intervention less effective in the United States. One last caveat is that this study looked at short-term decolonization and its effect on reducing surgical-site infections. Larger studies looking at decolonization in targeted populations of surgical patients that incorporate cost-effectiveness analysis would be of interest.
A much more common problem infectious disease specialists see in the clinic is the patient referred because of recurrent furuncles, usually due to MRSA. I have been very disappointed over the years with the efficacy of decolonization (using combinations of systemic antibiotics such as rifampin ± trimethoprim/sulfamethoxazole, antiseptic scrubs, and intranasal mupirocin) in reducing the frequency of recurrences. I suspect that this is due to fairly rapid recolonization with pathogenic Staphylococci following completion of the decolonization regimen.