Antimicrobial effects of chlorine dioxide in a hospital setting

Chlorine dioxide is a powerful disinfectant with strong antibacterial properties. We conducted a study at different sites of the Lebanese American University Medical Center-Rizk Hospital to determine the efficacy of the ECOM air mask in decreasing the particle load. Air cultures were obtained from three different locations, namely the patients’ elevator, visitors’ elevator and mobile clinic and the number of colonies grown on each type of agar was determined. We also measured particle counts at the three sites both at baseline and after placement of the ECOM air mask. After 7 days of ECOM air mask use, the numbers of colonies grown on all types of media was decreased by 20–100% versus the baseline values. The counts of particles of different diameters (0.3, 0.5 and 5 µm) were decreased at all three sampled sites. This study highlighted the efficacy of the ECOM air mask. The utility of the gaseous form of ClO2 as an antiseptic in the hospital setting appears promising.


Effect of the ECOM air mask on microorganisms
To perform this experiment, MacConkey agar (MAC) was used to isolate gram-negative bacteria, trypticase soy agar (TSA) and Luria-Bertani agar (LB) were used to culture different types of microorganisms and Sabouraud agar (Sab) was used to grow pathogenic and non-pathogenic fungi.Samples were collected from the patients' elevator, visitors' elevator and mobile clinic, one sample from each location.Prior to placement of the ECOM air mask, the baseline level of microbes was recorded by taking air cultures using SPIN AIR V2 (absorbs 100 L of air in 1 min) on all four types of agar.SPIN AIR V2 is a portable device, that can retrieve accurate volumes of air by forcing them, and after incubation, colony enumeration is done.The ECOM air mask was placed in the middle of each sampling area and samples were taken again after 1 week.The agar plates were incubated at 37 °C for 18 h and the number of colonies that grew on each medium was counted.

Effect of the ECOM air mask on particles
To detect the antibacterial and antifungal activity of 0.017-0.031ppm ClO 2 emitted from the ES-010 ECOM air mask, we measured the particle count at the three aforementioned locations (patient elevator, visitor elevator, mobile clinic).First, baseline samples (T0) were obtained, followed by placement of the ECOM air mask.In both elevators, samples were taken 2, 4, 5, 6, 8, 20 and 25 days after placing the ECOM air mask.For the mobile clinic, samples were taken 10, 20 and 24 h and 4 and 15 days after placing the ECOM air mask.The particles were counted using the TSI AeroTrak® 9303 Handheld Particle Counter, which measures all particles based on a set diameter.The TSI AeroTrak® 9303 Handheld Particle Counter is a lightweight plastic device used for particle measurements.The instrument can report up to three particle sizes simultaneously.

Effect of the ECOM air mask on the microorganism count
As shown in Table 1, After 7 days of ECOM air mask use, the numbers of colonies grown on all types of agar decreased by 20-100% versus the initial values.

Effect of the ECOM air mask on particles in air
The counts of particles of three different diameters (0.3, 0.5 and 5 µm) were recorded at baseline and at several subsequent time points, as in Tables 2, 3, 4.
In the mobile clinic, a major decrease in the particle count was detected within a few hours after mask placement and this decrease was maintained until day 4.However, this decrease was not sustained on day 15, excluding the large particle count, which was decreased by 49%, as in Table 2 and Fig. 1.
In the visitors' elevator, seen in Table 3 and Fig. 2 there were sustained decreases in the small (48%) and medium particle counts (43%), whereas the large particle count remained unchanged.www.nature.com/scientificreports/Similarly, in the patients' elevator, there were sustained decreases in the small (50%) and medium particle counts (45%), whereas the large particle count remained unchanged as shown in Table 4 and Fig. 3.

Discussion
Our experiment demonstrated the efficacy of the ECOM air mask in killing microbial pathogens at three locations and decreasing the particle load in air.
The antimicrobial properties of ClO 2 were confirmed in this study.According to one study, these effects are attributable to its ability to denature proteins 3 .In fact, another study demonstrated that ClO 2 is a size-selective antimicrobial agent.It can kill micro-sized organisms quickly, but it is incapable of causing measurable damage to much larger organisms because of its inability to penetrate deeply into living tissue.This might render ClO 2 relatively safe for human use as an antiseptic 10 .ClO 2 shares an antiseptic mechanism with natural antiseptics such as hypochlorous and hypoiodous acids.Neutrophil granulocytes use these hypohalous acids to kill bacteria after phagocytosis.ClO 2 and hypohalous acids target and attack sulfhydryl groups, which are important for the life processes of all living systems.This explains the inability of bacteria to develop resistance against ClO 2 11 .In addition, one study demonstrated the antibacterial effect of ClO 2 on MDR bacteria 12 .
The antiviral effect of the gaseous form of ClO 2 against RNA and DNA viruses has been reported 13 .Some studies suggested that this virucidal effect is attributable to the denaturing effect of ClO 2 on amino acids such as cysteine, tyrosine and tryptophan in viral protein capsids 14 .However, because ClO 2 exerted a virucidal effect on non-enveloped viruses, it could have other mechanisms of action that require further investigation 13 .The gaseous form of ClO 2 also has antifungal properties and it inactivates mould and bacterial colonies 15 .Its sporicidal effect is attributable to its ability to affect cell membrane integrity and inhibit germination 16 .
Seven days after starting the experiment in this study, decreased colony counts were detected on all agar plates for samples obtained from the patients' elevator and visitors' elevator.Regarding mobile clinic samples, a decreased colony count was detected on LB and TSA agar plates, whereas small counts were sustained on Sab and MAC agar plates, which might be attributable to contamination.
Regarding the particle count measurement, a decrease of up to 50% was documented for most of the air samples collected.The increased particle count in the mobile clinic can be explained by the fact that the exposure of this area to outdoor settings is significant, whereas in indoor areas such as elevators, the particle count was considerably lower.
The utility of the gaseous form of ClO 2 as an antiseptic in the hospital setting appears promising.The presence of ClO 2 in the air reduces the number of pathogens present.The use of the ECOM air mask in the hospital setting can disinfect the air, and consequently ensure better hygiene and infection control.Our study demonstrated its efficacy as disinfectant in real life setting.Further studies are required to investigate the antiviral, antifungal and sporicidal effects of ClO 2 in the hospital setting.In the era of artificial intelligence, technology can complement the use of chlorine dioxide in hospital setting by developing predictive models, ensuring real time monitoring and control, and performing automated data analysis.

Limitation
The first limitation in that our study was conducted only in one center and in specific limited sites.Multicenter studies should be performed in the future in different sites to elaborate and establish guideline for the use of such modalities.
Another limitation is that all the study sites were open areas which might have affected the particle count and culture.However, this reflects the real life setting.

Conclusion
This study highlighted the efficacy of the ECOM air mask in decreasing particle and microbial counts at different hospital sites.The novelty of this study brings an innovative way of use of the gaseous form of ClO 2 , shown to be an effective antiseptic in hospital setting.However, further studies are needed with more data to support these results and optimize its use.

Table 1 .
Number of colonies grown from samples at different locations before and 7 days after placement of the ECOM air mask.

Table 2 .
Number of particles after placement of the ECOM air mask in the mobile clinic.

Table 3 .
Number of particles after placement of the ECOM air mask in the visitors' elevator.

Table 4 .
Number of particles after placement of the ECOM air mask in the patients' elevator.