The antibacterial activity and stability of acetic acid

Summary

Acetic acid has been shown to have good antibacterial activity against micro-organisms such as Pseudomonas aeruginosa. This study examined the activity against a range of bacterial pathogens and also assessed any reduction in antibacterial activity due to evaporation or inactivation by organic material in dressings. Acetic acid was active at dilutions as low as 0.166% and the activity was not reduced by evaporation nor by inactivation by cotton swabs. Burn injuries are a major problem in countries with limited resources. Acetic acid is an ideal candidate for use in patients who are treated in those parts of the world.

Introduction

Acetic acid has been used as an antibacterial agent for thousands of years. There are reports that thieves used vinegar during the great plagues of Europe to avoid contracting infection when stealing valuables from the dead bodies of plague victims, and that apple cider vinegar was used as a wound dressing in the American Civil War and World War I. More recently, acetic acid has been a widely used topical antiseptic agent for the treatment of burn wounds and has been shown previously to have activity against Gram-negative organisms including Pseudomonas aeruginosa.¹

Despite the long history of acetic acid as an effective antiseptic, its popularity as a dressing has waned and this may be due to the availability of novel modern dressings which have impressive theoretical modes of action. It may also be because of concerns about the reliability of acetic acid as a topical disinfectant. The stability of the agent has not, to our knowledge been studied before and the compatibility of acetic acid with dressings has not been determined. A volatile agent such as acetic acid may lose activity through evaporation of active chemical, and, as with many other disinfectants, organic material including cotton gauze dressings may inactivate acetic acid thus reducing its antibacterial effect.

This study was designed to address four main questions: (i) How active is acetic acid against common pathogens at a range of dilutions? (ii) Does this activity reduce as a result of evaporation? (iii) Is the antibacterial activity inhibited by cotton gauze? (iv) What effect does organic matter have on the efficacy of acetic acid?

It is routine practice when assessing the efficacy of disinfectants to choose one Gram-positive and one Gram-negative as representatives of most bacterial species. The test organisms selected were chosen as representatives of Gram-positive and -negative bacteria that are common causes of infection in burn wounds. In addition, the NCTC/ATCC strains of Pseudomonas aeruginosa and Staphylococcus aureus are recognized test strains in EN standards for assessing the efficacy of chemical disinfectants, e.g. EN 13727.² Acinetobacter was chosen as, in recent years, it has presented a problem for burns patients.