Clinical Consultation: Preventing MRSA infections in the ICU

Using topical agents to prevent MRSA infections in the ICU What topical decontamination regimens are most appropriate to use in the ICU when methicillin-resistant Staphylococcus aureus (MRSA) is a concern?

MRSA is the second most common pathogen isolated in the ICU setting, associated with 52.9% of nosocomial infections.¹ Colonization of patients with S aureus (methicillin-sensitive and methicillin-resistant) has been found to be important for the development of subsequent infections, including bacteremia.^2-4 The primary reservoir of S aureus in humans is the anterior nares and, to a lesser extent, the perineum and skin.^5,6 As a result, topical antibiotics and antiseptics have been used to eradicate colonization in a variety of patient populations in an effort to prevent infection and to control transmission of MRSA.

Intranasal mupirocin(Drug information on mupirocin) ointment, applied 2 or 3 times daily for 3 to 5 days, has been the most extensively studied regimen for decolonization of MRSA. In several studies, mupirocin has been used effectively to prevent catheter-related staphylococcal infections in patients receiving hemodialysis and long-term ambulatory peritoneal dialysis.^5,7 One study also showed that use of mupirocin in patients colonized with S aureus significantly decreased surgical site infections after cardiovascular surgery.⁸

Two other studies of mupirocin treatment before surgical procedures showed no significant decrease in surgical site infections overall, although the incidence of S aureus infections was decreased in patients who were previously colonized with S aureus.^9,10 In addition, mupirocin use in colonized nonsurgical patients did not significantly decrease overall hospital infections.¹¹

The combination of chlorhexidine(Drug information on chlorhexidine) body wash and mupirocin intranasal treatment appears to be more effective in eradicating MRSA colonization than either treatment alone. Eradication was reported in 25% of those who received intranasal mupirocin twice daily for 5 days and a daily bath with chlorhexidine for 7 days, compared with 18% of those who received placebo intranasal ointment and a week of daily baths with chlorhexidine.¹²

Another study screened for MRSA carriage in patients newly admitted to a medical ICU and treated carriers with whole-body washings with 4% chlorhexidine on alternate days with or without intranasal mupirocin.⁶ The incidence of ICU-acquired colonization and infection significantly decreased after implementation of the MRSA control program.⁶

In the ICU, mupirocin has also been used as part of topical decontamination regimens. In one study, mupirocin or placebo was added to a topical decontamination regimen of tobramycin, polymyxin E, and amphotericin B(Drug information on amphotericin b).¹³ The rate of pneumonia was significantly lower in patients treated with mupirocin, primarily because of a lower frequency of S aureus infections.

A recent study by Camus and coworkers¹⁴ compared mupirocin with chlorhexidine alone or in combination with tobramycin(Drug information on tobramycin)/ polymyxin versus placebo for decontamination in intubated patients. The combination of mupirocin/chlorhexidine and tobramycin/ polymyxin was associated with a significant decrease in infections.¹⁴

The results of these studies must be tempered by the knowledge that widespread decolonization thera-py has been followed by increas- ing rates of mupirocin-resistant MRSA.^15,16 Mupirocin resistance, MRSA recolonization, and superinfection with other resistant bacteria or yeast remain significant concerns when topical decontamination regimens are applied broadly in the ICU setting.

The use of prophylactic topical antimicrobials to prevent infection and transmission is clearly an important infection control intervention in the setting of MRSA outbreaks. However, further studies evaluating the cost, benefit, and risk of resistance development in targeted ICU populations are necessary to support the routine widespread use of these decolonization regimens.