Objective

The objective was to determine whether the Defend 400 air cleaner could reduce airborne bacterial counts as compared to the control (no Defend device) in an urgent care outpatient facility running under normal conditions (occupied by doctors, nurses, staff and patients).

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Methodology

Enumeration and identification of airborne bacterial species from air samples. The samples were collected using an impaction air sampler, MAS-100 Eco Microbiological Air Sampler (MBV AG, Switzerland). Bacterial counts and bacterial species identification were performed by EMSL Analytical Inc (NJ, USA).

Air samples were taken during two phases: control and test.

• The control phase, without the Defend 400 air cleaner, consisted of air samples taken at each environment for five consecutive days. The control phase established a baseline for the air samples colony counts.
• The test phase, with the use of a Defend 400 air cleaner in each environment, was carried out in a similar fashion on the same five consecutive days of the week. During the test phase, the Defend 400 was set to speed 3, 108 Cubic Meters per Minute (CMM) [184 m3/hour]. Note that the device was always ON during the test phase.

Both, control, and test phase conditions reported a comparable overall number of visitors (303 v 306) to the clinic, with the same average and a median number of visitors per hour (5).

Summary of Results

Compared to the control, the Defend 400: 

• Significantly (P<0.05) reduced airborne bacteria in the combined four rooms by 52%.
• In each room, the reduction ranged from 11-72%.
• Overall, there was a 60% reduction in opportunistic pathogens (2980 to 1180 CFU).
• The most numerous species reduced consisted of Micrococcus luteus and Micrococcus lylae, which have been associated with a variety of illnesses including meningitis, septic arthritis, endocarditis, chronic cutaneous infections and catheter infections.
• Overall, there was a 43% reduction in pathogenic bacteria (70 to 40 CFU).

Conclusion and Discussion

During the 5 consecutive days, the Defend 400 significantly reduced the total bacterial count by 52%, which included a 60% reduction in opportunistic pathogens and a 43% reduction in pathogenic bacteria.

Because of the reduction in bacteria, the Defend 400 complements existing infection prevention practices such as built-in heating/air conditioning systems, social distancing, hand and surface disinfection, and the use of masks.

Reduction in airborne pathogens may, in turn, decrease transmission of airborne transmitted infectious diseases at healthcare institutions, although further studies are required to demonstrate this.