854 - Infection Prevention vs. Antimicrobial Stewardship: Does Nasal Povidone-Iodine Interfere with Methicillin Resistant Staphylococcus aureus (MRSA) Screening?

Background: As part of universal decolonization, intensive care unit (ICU) patients may receive intranasal mupirocin to reduce MRSA infections.  However, due to concerns about widespread use of mupirocin promoting resistance, some have proposed a bactericidal antiseptic, povidone-iodine (P-I), as an alternative.  There are few data as to whether either agent reduces the sensitivity of MRSA nares screening. This study aimed to discern whether intranasal P-I interferes with MRSA screening via polymerase chain reaction (PCR) and/or culture.

Methods: We performed a prospective proof-of-concept cohort study at our >1200-bed, community-based academic health care system, enrolling 20 patients who screened MRSA-positive by PCR on admission to a medical ICU, medical-surgical ICU, or medical stepdown unit.  All patients received twice-daily intranasal P-I (7.5%) for 5 days or until unit discharge.  We obtained follow-up nasal MRSA PCR tests after 4-6 days, and confirmed all PCR results with MRSA cultures using CHROMagar™.  We calculated sensitivity of MRSA PCR at follow-up using culture as the gold standard.

Results: Twenty patients were enrolled, with a median age of 72 years (range, 53-91).  Most (75%) were admitted with active infection, and 40% had known MRSA history.  All baseline PCRs were confirmed by positive culture. Patients underwent a mean of 8.1 (range, 4-13) nasal P-I applications prior to follow-up testing.  At follow up, 16/20 (80%) remained MRSA-positive via both PCR and culture. Of the 4 patients with negative follow-up results, 1 was both PCR-/culture-, 2 were PCR+/culture- and 1 was PCR-/culture+.  All 4 had received ≥1 doses of vancomycin, and one person had received ≥1 doses of linezolid.  The sensitivity of MRSA PCR at follow-up was 94%.

Conclusion: MRSA PCR remains highly sensitive even after multiple applications of P-I, and may be more sensitive than culture.  If clinicians wish to screen for MRSA for stewardship or other purposes, receipt of nasal P-I should not be a deterrent.  However, the fact that most patients remained culture-positive after 4-13 applications raises concerns that P-I is less effective than mupirocin for clearing nasal colonization.  We recommend using quantitative cultures to further investigate the effectiveness of nasal P-I.