Compatibility between wiper materials and chemical disinfectants affects stability and concentration
By Kimberly Dennis MacDougall and Valerie Williamson, Kimberly-Clark Professional
Cleaning environmental surfaces is critical to reducing health-care acquired infections and is the necessary first step in any sterilization or disinfection process, according to the Guidelines for Environmental Infection Control in Health Care Facilities from the U.S. Centers for Disease Control and Prevention (CDC).
Cleaning renders surfaces safe to handle or use by removing organic matter, salts, and visible soils, all of which interfere with microbial inactivation. The physical action of scrubbing with detergents and surfactants and rinsing with water removes a large number of microorganisms from surfaces.
In addition to physical cleaning, disinfecting or sanitizing surfaces is also critical to reducing health-care-acquired infections. However, not all surface sanitation efforts are equal. In fact, according to two recent studies, some common systems-such as using a cotton rag or cellulose-based wiper to apply bleach or quaternary amines to surfaces-deliver less-than-ideal concentrations of disinfectants/sanitizers to surfaces.
An important step in the disinfection/sanitization process is mixing and application of the disinfectant. To be effective, the disinfectant should be mixed and applied to the surface uniformly, according to the directions, and the surface should remain wet for the length of time recommended by the manufacturer.
The selection and use of chemical germicides is another important step. A number of disinfectants are currently used in health-care facilities including alcohols, hypochlorites, chlorohexidine, iodophors, hydrogen peroxide, phenolics, and quaternary amine compounds.
Methods for applying surface disinfectants
There are various methods for applying surface disinfectants in health-care environments. In the studies described here, two common systems were evaluated:
- Open bucket system: This system employs an open bucket in which cotton rags or disposable cellulose-based wipers are submerged into the disinfecting solution and then taken out to wipe down various surfaces.
- closed bucket system with disposable non-woven wiper: These disposable cleaning wipers have a fiber preparation that is compatible with the disinfecting chemicals bleach and quaternary amines. A dry roll of wipers is placed into the bucket and the disinfecting chemical is added to saturate the wipers. The bucket is closed and the saturated wipers are dispensed via a port on the top of the bucket.
To ensure that the chemical concentration of the disinfectant solution is adequate, a simple paper indicator strip is typically used to check the parts per million of disinfectant (bleach or quaternary amines) present in the bucket. However, this practice does not monitor the amount of disinfectant in the liquid deposited from the wiper to the surface. And, in fact, it is the ability to deliver the correct concentration of germicidal ingredients to surfaces-to render microbes non-functional-that is the primary operative assumption underlining the principle of surface disinfection, and the focus of the two studies.
Study #1 and results
Two studies were conducted to examine the effects of commonly used wiping material substrates on the amount of quaternary amines and bleach being released to surfaces for the purpose of disinfection. It is important to emphasize that the systems used for the purpose of these studies are different and that each wiper type is used under conditions representative of its common use. Obviously, the length of time the wipers are exposed to the chemical and the number of wipers placed in the chemical at one time are significant factors. Therefore, the closed bucket system creates a significantly more challenging environment with regard to the exposure of the wipers to the disinfectant compared with the open bucket system because the wipers remain in contact with the chemical solution for a significantly longer period.
In the first study, the different wiping systems were compared over an 8-hour period, comparable to a single work shift in a hospital setting. The study was then extended out to three days to investigate the compatibility of the disposable non-woven wiper in the closed bucket over time, as this system provided 90 wipers per roll and lasted much longer than the open bucket of disinfectant fluid with dipped wipers. A conservative rate of using six wipers in the bucket per hour over the course of an 8-hour shift was investigated. Fluid samples were collected from the wipers and tested at predetermined time points to detect active quaternary amines available from the wiper for surface disinfection.
In conducting the study, a quaternary amine solution was prepared based on chemical manufacturer specifications, and duplicate buckets without wipers were used as controls. Fluid from the controls was collected and analyzed over an 8-hour period. Fluid was also removed from the open bucket and tested prior to the removal/dipping of the wipers to establish the effect of the correct concentration of the disinfectant solution at designated time points.
For the closed bucket system with the disposable non-woven wipers, quat samples were taken from three wipers at 10-minute time points to obtain solution for three titration measurements of disinfectant for each extraction. The fluid was extracted from the wipers and immediately collected in a plastic bag for quat release measurements, which were taken instantaneously.
For the cellulose-based wipers in the open bucket system, wipers were submerged in the quaternary solution for 5 seconds, every 10 minutes. Three wipers were removed at designated time points and the solution extracted for quat release measurements. Steps were taken to ensure that the wiper maintained adequate fluid and was not wrung dry. Measurements were taken instantaneously. There were three titrations completed for each extraction.
The study results showed a significant decline in the concentration of basic quaternary amines released when cotton rags or cellulose-based wipers were used in the open bucket system compared to the disposable non-woven wipers in the closed bucket system. In fact, an immediate drop-off of quat release at the time point of zero was noted for both cotton and cellulose-based wipers even though neither material was in continuous contact with the disinfectants in the open bucket. This observation suggests an instantaneous negative interaction between these materials and the disinfectant chemicals tested.
The study findings showed that the initial quat release from cotton was 53 percent lower than the original chemical disinfectant A solution, as shown in Fig. 1. Over 8 hours, representative of a standard work shift, the quat release from cotton continued to decline rapidly. Prior to the solution being depleted in the bucket, the quat release from the last cotton rag passed through the bucket was 0.83 percent of the original disinfectant concentration. By comparison, the cellulose-based wipers also displayed a sharp reduction in active quat release for chemical disinfectant A. At the conclusion of the 8-hour shift, the average quat release from the cellulose-based wipers was 21.5 percent of the original concentration.
In contrast, the disposable non-woven wipers maintained at least 83.6 percent of the chemical disinfectant A solution concentration for the first 8 hours of the study. In extended three-day testing, the non-woven wipers retained an average of 88.6 percent of the original active concentration.
The results for the chemical disinfectant B are shown in Fig. 2. According to study findings, the initial drop in active quat concentration for cotton wipers was 29.3 percent. This is a significant loss that may be of concern to health-care facilities using this type of disinfectant and wiping substrate to disinfect critical surfaces. Conversely, the study found that the initial disposable non-woven wiper taken from the enclosed bucket of chemical disinfectant B maintained 99.6 percent of the original chemical concentration. In extended three-day testing, the disposable non-woven wipers retained an average of 90 percent of the original chemical concentration.
These results suggest that the disposable non-woven wipers with a fiber preparation intended to yield quat compatibility would better maintain target disinfectant concentration as compared to cotton rags and cellulose-based wipers, even over a relatively prolonged period of time.
Study #2 and results
A second study was conducted to evaluate the effects of the same commonly used wiping substrates on the amount of bleach being released to surfaces for the purpose of disinfection.
The variables tested in the study-including the type of delivery system, the length of time the wipers were exposed to the chemical, and the number of wipers placed in the chemical at one time-mirror practices commonly used in health-care disinfection applications. The bleach solution tested was diluted to the chemical manufacturers’ recommended level for disinfection. Because bleach tends to be less stable over time, the testing period was limited to 72 hours.
The study results showed that cotton rags and cellulose wipers in an open-bucket system rapidly depleted the active chloride ion present in bleach (see Fig. 3). However, the disposable non-woven wiper used in the closed-bucket system kept it stable for a full 72-hour period.
In the study, the chloride ion release from the first cotton rag from the open bucket was 11 percent lower than the original bleach concentration. The chloride ion release from the first cellulose-based wiper was 13 percent lower than the original bleach disinfectant solution and dropped to 28 percent lower after 24 hours of use.
In contrast, the initial chloride ion release for the disposable non-woven wipers was only 3 to 5 percent lower than the original bleach concentration even after 72 hours of use.
The significant decline in the release of bleach disinfectant when cotton rags and cellulose-based wipers were used in an open-bucket system implies that active disinfecting agents are not always applied to the surface in the ideal concentration to support optimum environmental disinfection.
It is interesting to note that the Association for Professionals in Infection Control and Epidemiology (APIC) calls for the use of disposable cloths during environmental (surface) cleaning as a way to prevent and/or control multiple drug-resistant bacteria and notes that, for all environmental surface cleaning, cloths should be thoroughly moistened with disinfectant. APIC further cautions against returning a cloth to the bucket of disinfectant once it has been used to wipe surfaces as this may “promote increased environmental contamination and microbial spread.”
The enclosed system described in these studies helps to avoid contamination of the wipers and the cleaning solution because it eliminates any opportunity to re-dip the wipers into an open bucket. In addition, the use of the closed-bucket system reduces the need for mixing new solution batches because the system is stable for an extended period of time. Factors such as changes in pH and exposure to air and light, which can affect the stability of bleach, are not a problem because the closed-bucket system allows for minimal bleach and wiper exposure to air and light.
In conclusion, infection control practices can be optimized through the selection of wiping material systems that are compatible with the chemicals (quaternary amines and bleach) used in the surface disinfection protocol. Likewise, some materials currently in use are far from optimal in their ability to provide disinfectant actives to surfaces in the intended concentrations. These findings are important considerations in the design of today’s infection control practices.
Kimberly Dennis MacDougall is a research scientist and Valerie Williamson is category manager at Kimberly-Clark Professional (www.kcprofessional.com).