Effectiveness of various cleaning and disinfectant products on Clostridium difficile spores of PCR ribotypes 010, 014 and 027

Currently C. difficile is emerging worldwide in healthcare facilities [1]. The incidence of C. difficile infections doubled between 2001 and 2010 in the United States of America [2‐5]. C. difficile is an important health threat associated with morbidity, mortality, and extra costs. The costs caused by C. difficile are estimated between $8911 and $30,049 per case [3, 5]. These costs arise due to direct healthcare costs and due to longer hospital stays. The yearly national excess hospital cost associated with hospital-onset C. difficile is estimated to be €4 billion for Europe, $1 billion in the United States of America and $280 million in Canada [5, 6]. Effective infection control measures are therefore greatly needed.

The hospital environment is known to be a key pathway for patients to acquire C. difficile infections (CDI). Spores of C. difficile can survive in hospitals for years [7]. New views on the transmission of C. difficile conclude that asymptomatic carriers can also introduce the bacteria into the hospital and may consequently play an important part in the transmission to other patients. Still, the chance of transmission from asymptomatic carriers is probably lower than from patients with a CDI [8, 9]. Guidelines to date only advise to take extra measures with CDI diagnosed patients, for example the guideline for disinfection and sterilization in healthcare facilities, 2008, of the Centers of Disease Control and Prevention (CDC).

To disinfect environments contaminated with C. difficile, it is generally advised to use an unbuffered 1:10 dilution of hypochlorite [10]. It is known that hypochlorite does not enhance sporulation and when used for environmental disinfection leads to a significant reduction of C. difficile-associated diarrhea [11]. However, hypochlorite has to be used in excessive concentrations to be effective, thereby increasing its toxic and corrosive properties. Therefore, alternative agents are needed to eradicate spores of C. difficile.

CDI is a serious infection, with an all cause 30-day mortality of 15% or greater, that warrants a variety of infection control measures to prevent and control its occurrence [19]. Effective cleaning and disinfection is an essential prerequisite to prevent the spread of CDI within healthcare settings. Presently, chlorine-based products are the mainstay with regard to environmental disinfection in the Netherlands, but alternative, ready-to-use products are needed to ensure consistent cleaning. We therefore tested the effectiveness of different cleaning/disinfecting wipes and sprays against spores of C. difficile PCR ribotypes 010, 014 and 027. These ribotypes were chosen because of their differences in virulence and transmission potential. C. difficile ribotype 010 does not produce toxins and therefore is unable to cause CDI in humans. In contrast, C. difficile PCR ribotype 027 is known for its “hypervirulence”. It is associated with increased morbidity and mortality [15, 20, 21], as well as its potential to cause large outbreaks. Currently, this type is found in 1.2% of all characterized isolates sent to the National Reference Laboratory in the Netherlands [21]. The third tested strain PCR ribotype 014 produces toxin A and B and is the most prevalent (17%) PCR ribotype in the Netherlands [21].

The overall effectiveness of products measured by log₁₀ CFU reductions ranged from 3.09 (spray A) to 5.29 (wipe B). While to date a European standard for an in vivo test that mimics the real-life situation for sporicidal effectiveness is missing, the EN 13704 ‘suspension test’ requires a 3 log₁₀ CFU reduction after 60 min. All products, in all application forms, would therefore pass this European norm. Given the fact that higher numbers of spores are found in the hospital environment [20] and that patients with a CDI can excrete up to 1 × 10⁷ spores per gram feces [5], a more realistic EN test should be developed that mimics real-life bacterial/spore loads and cleaning times of less than 60 min. We would recommend a significantly higher (e.g. a 5 log₁₀) CFU reduction for effective control of C. difficile transmission, as was also proposed by Fraise et al. [20]. Our tests show that this requirement is feasible, as shown by the fact that wipe B achieved a 5.29 log₁₀ CFU reduction.

When comparing the mean log₁₀ CFU reductions by application type (wipe versus spray), it became obvious that the ready-to-use wipes were outperforming the sprays using a paper towel by 0.81 to 1.60 log₁₀ CFU reductions. The differences in log₁₀ CFU reduction between the wipe and spray with the same active ingredient were consistently observed for all products tested in both application forms (A, B and C). While not as pronounced, the differences in log₁₀ CFU reductions were also apparent in log₁₀ RLU reductions, with the three highest log₁₀ RLU reductions seen for wipes and the lowest for sprays. This difference between wipes and sprays could possibly be explained by the “mechanical” effect involved with cleaning/disinfecting. Studies similar to ours, but using detergent wipes achieved an average log₁₀ CFU reduction of 1.63, which is exactly within the range of difference we observed with wipes and sprays [22, 23]. Clearly, the application form is responsible for a significant part of the effect in addition or combination with the disinfecting active compound. As we compared wipes against sprays plus paper towels, some may argue that the difference in effect is due to the difference in mechanical effect of the different materials used for wiping. Based on a study by Diab-Elschahawi et al., who compared microfibers, cotton cloths, sponge cloths and paper towels for their decontamination abilities, without finding a significant difference [16], we conclude that the difference between wipes and sprays in our study cannot be explained by the difference in wiping material.

Although sprays were used according to the suppliers’ instructions, surface coverage as well as the actual contact time and number of wiping movements might be different to the use of impregnated wipes. Wipes B and C were available as ready-to-use wipes and wipe A needed to be prepared in a reusable container. Ready-to-use wipes eliminate the possibility of human errors that could make the disinfectant less effective or make the wipes unnecessarily toxic.

In addition to the application method and the compound used, our results indicate that the individual C. difficile strain is of importance with regard to the effect of cleaners/disinfectants. While CFU reductions were highest for the non-toxin producing C. difficile ribotype 010 in a low organic contamination environment, they were lower for the clinically more important ribotypes 014 and 027. Interestingly, the differences in effectiveness were less pronounced and, in the case of wipe B, even reversed in a high organic contamination environment. While our results in this regard are not fully conclusive, they certainly indicate the importance of including a variety of clinically relevant ribotypes when evaluating the effect of disinfectants against C. difficile.

In conclusion C. difficile spores of 014 and 027 strain are harder to eliminate compared to those of the non-toxigenic strain 010. Future studies should use these more resilient types of C. difficile to ensure the needed in-vivo effect. Impregnated cleaning/disinfection wipes generally outperform ready-to-use sprays, even if based on the same active ingredient, and should thus be preferred over sprays for the daily cleaning/disinfection in rooms of patients with CDI. While all products pass current EN 13704 standards we believe that - given the in-vivo load of Clostridium spores - higher standards should be set, such as those achieved by the products based on 1.5% of hydrogen peroxide.