Ocular Microbiology and Immunology Group
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2017 OMIG Abstract 14

In Vitro Evaluation of a Hypochlorous Acid Hygiene Solution
on Established Biofilms
Eric G. Romanowski, Nicholas A. Stella, Kathleen A. Yates, Kimberly M. Brothers, Regis P. Kowalski,
and Robert M. Q. Shanks
The Charles T. Campbell Ophthalmic Microbiology Laboratory, UPMC Eye Center, Ophthalmology
and Visual Science Research Center, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania

Purpose: The goal of the current study was to determine whether a commercial formulation of hypochlorous acid (HOCl) hygiene solution (0.01%), Avenova™, can destroy existing biofilms formed by ocular clinical bacterial isolates, including blepharitis isolates of Staphylococcus aureus and coagulase-negative staphylococci (CNS), and a keratitis isolate of Pseudomonas aeruginosa.

Methods: Biofilms grown in bacterial growth media on disposable contact lens cases were challenged with 0.01% HOCl.  At various time points, surviving bacteria were quantified by serial dilution and colony counts. The S. aureus biofilms were also similarly treated with 1% azithromycin (not the AzaSite formulation). S. aureus biofilms formed on glass were challenged with the 0.01% HOCl, and imaged using vital staining and confocal laser scanning microscopy. Crystal violet staining of the biofilms on the contact lens cases was also used to determine residual biofilm after HOCl treatment.  

Results: Bactericidal decreases (≥3 log10; 99.9%) were observed for all tested bacterial species after a 30-minute exposure to 0.01% HOCl. S. aureus biofilms had a bactericidal level of killing by 10 minutes (p<0.01), S. capitis by 5 minutes (p<0.001), S. epidermidis by 30 minutes (p<0.001), and P. aeruginosa by 10 minutes (p<0.01). In contrast, 1% Azithromycin produced only a 0.5 Log10 decrease in S. aureus colony counts after a 30-minute exposure even though the isolate is considered susceptible to azithromycin. Confocal microscopy and crystal violet staining analysis of bacterial biofilms treated with HOCl both demonstrated that biofilm bacteria were readily killed, but biofilm structure was largely maintained.

Conclusions: HOCl 0.01% produced bactericidal decreases of bacteria (S. aureus, CNS, P. aeruginosa) contained in biofilms by 30 minutes, but did not disrupt biofilm structures. The time to bactericidal decrease of the tested staphylococcal blepharitis isolates varied by species, with S. capitis taking the shortest time while S. epidermidis took the longest. Azithromycin had little effect on the number of S. aureus contained in the biofilms. Further studies are indicated to determine the clinical significance of these findings.

Disclosure: S (NovaBay Pharmaceuticals, Inc.)

2017 Agenda and Abstracts | < Previous Next >