Long term Impact of a disinfectant with residual activity on suppression of bacteria on fomites in hospital waiting rooms

Charles P. Gerba and Laura Y. Sifuentes The University of Arizona, Tucson, AZ.

DISCUSSION

We have previously shown that treatment of surfaces with SurfaceWise® in an intensive care unit suppressed total bacterial numbers by greater than 99% for 15 weeks. We have extended this work now to include waiting rooms in hospitals. Total bacteria numbers remained below 99% of original levels for 4 weeks after treatment and below 87% even after 15 weeks. The surface treatment appears to offer a long term suppression of bacterial numbers on surfaces in heavily used facilities reducing the risk of exposure to antibiotic resistant bacteria.

Reference Tamimi, A. H. et al. 2014. Long term efficacy of a self-disinfecting coating in an intensive care unit. Am. J. Infection Control. (42:11):1178-1181.

Disclosure Statement: This study was supported by funding to the University of Arizona by Allied BioScience, Inc., Dallas, TX.

ABSTRACT

Background/Objective: Control of bacteria responsible for infections in health care environment requires repeated application of disinfectants to be effective. The goal of this study was to assess the ability of a disinfectant with residual activity and its application method on the long term suppression of bacteria in hospital waiting rooms.

The levels of bacteria on common fomites in the waiting rooms for patients to be admitted to a hospital and the emergency room waiting area were sampled over a two week period of time in a 300 bed hospital to obtain the background levels of total bacteria, coliforms, Methicillin Resistant Staphylococcus aureus (MRSA), Carbapenem Resistant Enterobacteriaceae (CRE), Vancomycin Resistant Enterococci (VRE) and Clostridium difficile bacteria. Sampling sites in the ER lobby were the microphone used at the check in counter, chair armrests, check in counter, door handles, end tables, countertops and an area of wall. Sampling sites in the main lobby were telephone, check in counters, chair armrests and tabletops. All movable items were inconspicuously tagged and coded over the course of the study to ensure they had not been removed from the waiting rooms. These areas were then treated with a onetime application of SurfaceWiseTM (Allied BioScience, Inc., Dallas, TX) which is a onetime application of a persistent antimicrobial. The same areas were then sampled for the study bacteria after 7, 14, 30, 60 and 105 days. There were no changes in the routine disinfection/cleaning activities in these areas before and after the treatment.

Results: Total bacterial numbers were found to decrease from an average of 100 colony forming units (CFU)cm2 on all sites before the treatment to 0.1 or less cm2

(99.8 % reduction) for the next 30 days and then increased to an average of 4 CFU/cm2 after 105 days. Statistical analysis of the data indicated the reductions observed where significant (p<0.05). Antibiotic resistant bacteria were detected on almost half of the sites sampled (7/15) before treatment. After treatment, antibiotic resistant bacteria were isolated only once over the next 105 days (1/64).

Conclusions: The product treatment was found to be highly effective in reducing the numbers of bacteria on hospital fomites for several months in hospital waiting rooms used for patient admittance.

METHODS

Microbial methods Areas of 100 sq. cm were sampled using a sponge stick containing Letheen broth (3 M, St. Paul, MN) to neutralize any residual disinfectant. After sampling, the samples were immediately placed on ice packs and sent overnight to the University of Arizona. Upon receipt the broth was extracted from the sponge stick by manual agitation, and then 4 mL of extracted broth was assayed using selective media for isolation of the various bacteria. Samples were cultured for total heterotrophic bacteria, Clostridium difficile, methicillin-resistant Staphylococcus aureus (MRSA), vancomycin resistant enterococcus (VRE), and carbapenem resistant Enterobacteriaceae (CRE).

Data analyses Average log base 10 reductions due to intervention were calculated based on geometric means. A 95% confidence interval (CI) was constructed for the log base 10 reductions with upper and lower limits using student t-statistic. Percent reduction of HPC concentrations on fomites were also calculated based on the geometric means. Due to the fact that the data and the log transformed data did not meet the conditions of normality, homogeneity and the presence of few outliers in the datasets, bootstrapping techniques were used to conduct Analysis of Variance (ANOVA) for each stage between the baseline concentrations for the sampled fomites and the intervention concentrations for the same fomites to determine statistical significance.

RESULTS

Before Treatment

The average (arithmetic mean) number of heterotrophic bacteria detected per 100 cm2 at all locations and % reductions in bacterial numbers after treatment are shown in Table 1 and Figure 1. Bacterial numbers were always 99% less on surfaces after the treatment for four weeks, 96% after eight weeks and still almost 89% after 15 weeks. Figure 1 shows the distribution of the numbers of bacteria on each sampled surface. As can be seen the numbers of bacteria on all sampled surfaces are below the level before treatment of surfaces with SurfaceWise®. Only on one occasion was an antibiotic resistant bacteria isolated in the waiting rooms for 15 weeks after treatment (Table 2).

Figure 1. Distribution of bacteria numbers (HPC) on surfaces in waiting rooms