Effect of washing on the antimicrobial efficacy of povidone-iodine containing products against Staphylococcus aureus

Background: Nasal carriage of Staphylococcus aureus (SA) is a known risk factor for health care associated infections. Reducing nasal colonization prior to surgery with intranasal mupirocin has been used to decrease this risk; however, treatment takes 5 days and resistance has been reported. Povidone-iodine (PI) products can potentially reduce or eradicate SA in the nares prior to surgery, but the bioavailability of PI is diminished by proteins in nasal secretions.

Objective: The aim of this study was to determine the efficacy of a newly formulated mucoadhesive PI antiseptic using a porcine mucosal model designed to simulate mucocilliary clearance in the nares.

Methods: Ex-vivo porcine vaginal mucosal tissue was treated with a 3M^TM Skin and Nasal Antiseptic PI containing formulation or Betadine solution for 5 min. [PI solution has similar antistaphylococcal efficacy using ex-vivo porcine nasal vs. vaginal mucosa.] Tissues were washed with saline or saline containing 2% porcine mucin for 2 min and repeated after 15 min (to mimic mucocilliary clearance). Tissue was then infected with methicillin sensitive SA (MN8) 1 x 10⁶ CFU/tissue (5mm). Tissue was incubated at 37^oC for 1h; treated to neutralize PI, homogenized, and plated.

Results:

Betadine and 3M Skin and Nasal Antiseptic completely killed SA (>5 log reduction in CFU/tissue) without washes. Betadine solution had minimal effects on SA following saline washes; whereas, the 3M muco-adhesive PI nasal antiseptic reduced bacterial counts >3 log CFU/tissue (99.9%) by 1 h. Mucin 2% further reduced efficacy of Betadine, whereas, the 3M PI antiseptic was unaffected.

Treatment	Log reduction (CFU/tissue explant)*
	Betadine	3M Nasal Antiseptic
No wash	5.33 (0)	5.33 (0)
Saline	0.48 (0.13)	3.19 (1.27)§
Mucin 2%	0.10 (0.15)	3.65 (1.28)§

*Average (+/- SEM) from untreated controls

^§Statistically significantly different, p<0.05, n=3

Conclusions: Evidence suggests that washing reduces efficacy of PI containing antiseptics. The 3M Skin and Nasal Antiseptic performed significantly better than Betadine solution against SA using an ex-vivo tissue model designed to simulate mucocilliary clearance in the nares.