Ozone gas is an effective and practical antibacterial agent

Background

Hospitals and other communal settings face an ongoing challenge from surface-borne bacteria, including drug-resistant organisms such as methicillin-resistant Staphylococcus aureus (MRSA) and spore-forming pathogens like Clostridium difficile. Standard cleaning with chemical disinfectants and wipes can miss hard-to-reach surfaces, porous materials such as fabric and cardboard, and areas with heavy contamination. Researchers Manju Sharma and James B. Hudson set out to test whether gaseous ozone, delivered by a portable generator, could offer a practical, whole-room alternative for reducing bacterial contamination in these environments.

Study design

The study tested a portable ozone generator fitted with a catalytic converter against 15 medically significant bacterial species, spanning gram-positive organisms, gram-negative organisms and acid-fast bacteria. Testing took place in two settings: a small sealed polycarbonate chamber (around 4.47 cubic feet) and a larger office room (about 34 cubic metres). Bacterial samples were dried onto a range of everyday surfaces, including plastic, fabric, cotton, filter paper and cardboard, to reflect the kinds of materials found in real institutional settings. The standard exposure protocol was 25 parts per million (ppm) of ozone for 20 minutes, followed by a short burst of humidity above 90% relative humidity. Bacterial survival was measured as colony-forming units (CFU) before and after treatment.

Findings

Under the 25 ppm, 20-minute protocol with the added humidity burst, ozone gas inactivated more than 3 log10 (over 99.9%) of colony-forming units for most of the bacteria tested. Organisms shown to be susceptible included Acinetobacter baumannii, Clostridium difficile and MRSA. This level of inactivation held up consistently across the different surface materials tested and regardless of whether the bacterial samples were wet or dry when treated. The authors noted that precise inactivation endpoints could not always be pinned down exactly, due to some natural loss of bacteria during the drying and assay process itself, separate from the ozone treatment.

What the authors concluded

Sharma and Hudson concluded that an ozone generator of this kind can provide a valuable decontamination tool for reducing bacterial contamination in institutional and communal settings, including hospitals and other healthcare facilities. They positioned gaseous ozone as a practical option for treating whole rooms and awkward surfaces that are difficult to disinfect thoroughly by hand.

Limitations of this study

This was a controlled laboratory and simulated-room study, not a trial in an occupied clinical setting. Real hospital environments involve organic soil load (such as body fluids, dust and debris), variable humidity and airflow, and furnishings that may behave differently to the test surfaces used here. The study measured bacterial inactivation only; it did not test viruses, fungi or moulds, and did not compare ozone gas directly against standard chemical disinfectants in a head-to-head trial. Ozone gas at the concentrations used is only safe in unoccupied spaces and requires proper ventilation and safety protocols before people re-enter treated areas - this is an environmental disinfection method, not a therapy applied to the body.