What’s in the disinfectant pipeline?

uni-sporWe talk often about the ‘antibiotic pipeline’, but as the pipeline slows to a trickle, the ‘disinfectant pipeline’ is made even more important. Prof Jean-Yves Maillard from Cardiff University recently gave a talk at the HIS Spring Meeting scanning the horizon for new disinfectants. Prof Maillard began with highlighting the emerging challenge that biofilms present to effective disinfection of dry hospital surfaces. Whilst traditionally associated with wet environments, biofilms have recently been discovered on dry hospital surfaces. The entire disinfection process, from product develop through to delivery at the point of use, has been configured without the knowledge that biofilms are present. This means that disinfectants have not been formulated with anti-biofilm activity in mind, standard laboratory tests and based on killing bacteria in a planktonic growth phase, and that the mode of usage of disinfectants has not been developed in a way that addresses the presence of biofilms. Gama and Cardiff University are collaborating to develop some disinfectant formulations with anti-biofilm activity in mind. Prof Maillard also discussed some other approaches to developing disinfectants, for example, exploring synergies between ‘green’ disinfectants, chiefly hydrogen peroxide and peracetic acid combinations. Finally, Prof Maillard gave a word of warning against disinfectants with a residual activity claim. The level of residual activity is likely to be low level, and whilst this may be useful in the short term, it will promote sub-lethal exposure and the development of reduced susceptibility.

 

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Transmission of C. difficile: Asymptomatic carriers are also a risk

A new paper from Canada that has examined the effect of screening and isolation for asymptomatic carriers of toxigenic C. difficile has just been released onto the JAMA Internal Medicine website. In this study, 4.8% of patients screened were found to be carrying the tbD gene and these patients were part of an intervention group that included isolation, but not in the traditional sense as shared bays were permissible however the curtains remained drawn. The effect of this intervention was not immediate however there was a significant decrease in trend over time of 7% per 4-week period and the authors have suggested that based on previous data they would have expected to see 101 cases over the intervention period, whereas they actually saw 38 cases, a 63% decrease. Asymptomatic carriage has for some time been suggested as a significant risk factor for transmission, as other studies which show high skin contamination from these patients have demonstrated, including studies that have demonstrated a risk from healthcare environments contaminated by asymptomatic patients. Keeping disinfectants with proven sporicidal activity in reserve for only ‘cases’ of C. difficile may mean that opportunities for reducing the bioburden from asymptomatic patients are missed

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Which strategy is most cost-effective in preventing the transmission of C. difficile?

As resources become more and more constrained in healthcare facilities around the world, we need to think in terms of both effectiveness, and cost-effectiveness. A new modelling study published in PLoS ONE evaluates the cost-effectiveness of several strategies to prevent the transmission of C. difficile. Probably the key finding of the study is that hand hygiene compliance, environmental decontamination, and empiric isolation and treatment were the most effective interventions.

The model was a simulation of C. difficile transmission, including estimates for the following parameters: interactions between patients and health care workers; room contamination via C. difficile shedding; C. difficile hand carriage and removal via hand hygiene; patient acquisition of C.
difficile via contact with contaminated rooms or health care workers; and patient antimicrobial
use. Six interventions were then tested either individually or as a bundle at three levels of efficacy (base-case (BASE) to reflect typical hospital practice, (2) intervention (INT) to represent implementation of hospital-wide efforts to reduce C. diffiicle transmission, and (3) optimal (OPT)to represent the highest expected results from strong adherence to the interventions), and at three levels of transmission and importation (low, medium, and high).

Bundled interventions were most cost-effective, and hand hygiene compliance, environmental decontamination, and empiric isolation and treatment were most effective as individual interventions.

This study supports most approaches to C. difficile management, which recommend a bundle of interventions including focus on hand and environmental hygiene, and patient isolation.

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Standardising the testing of disinfectant wipes

wipe
There has been quite a bit of discussion lately about the suitability of laboratory testing methods for wipes. This is a crucial issue, and may explain to a large degree the differences in wipe performed when tested in parallel. For example, a study of wipes with sporicidal claims found that few actually demonstrated meaningful sporicidal activity!

A recent study in the Journal of Hospital Infection aims to standardise the testing of disinfectant wipes using an ASTM method. The protocol depends on using a “Wiperator”, which standardises the pressure and motion used to apply the wipe to the inoculated test surfaces. The new test protocol was put through its paces by three laboratories testing the efficacy of five disinfectant wipes against two common pathogens (S. aureus and A. baumannii). Reassuringly, all of the wipes tested achieved a >4-log reduction on the test bacteria within 10s of wiping, and 3/5 wipes tested achieved a >7-log reduction on the test bacteria. However, only one of the wipes tested (based on 0.5% accelerated H2O2) prevented the transfer of bacteria to another surface.

This methodology solves a number of common problems with other methods used to test the efficacy of disinfectant wipes, especially standardising the pressure and wiping motion; the inclusion of a measure of the risk of onward transfer of bacteria to other surfaces is another important inclusion in the protocol. It seems likely that this disinfectant wipe testing standard will quickly become the gold standard method.

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Chlorhexidine daily bathing reduces infections: multicentre study in the US

CHG_bathing_alternative_pack1 An ambitious study involving ICUs in 33 community hospitals in the US over a period over five years evaluated the impact of chlorhexidine (CHG) daily bathing. ICUs in 17 hospitals implemented CHG daily bathing, whereas 16 ICUs did not, and served as controls. The study evaluated any potential changes in a host of infection-related outcomes, including CLABSI, any BSI, VAP, CAUTI, and VRE and MRSA HCAIs.

The ICUs were not randomised to the intervention, but it’s a pretty good sample size so you’d expect any variability to be smoothed out naturally. However, it is worth nothing that 88% of the hospitals that implemented CHG bathing also had an active MRSA screening programme, whereas only 50% of the hospitals that did not implement CHG bathing had an MRSA screening programme. Thus, implementing CHG could be a marker of a more complete infection prevention and control programme, which could confound these findings. Perhaps related to this is the finding that MRSA, VRE, CAUTI, CLABSI, all primary BSI and VAP were all more common in the ICUs that implemented CHG, suggesting that the baseline characteristics of the units that chosen to implement CHG were different to those that did not.

Nonetheless, the results from the time series analysis (which evaluated whether there were changes in the rate of these HCAI-related outcomes) are impressive: CLABSIs were reduced by 59%, primary BSIs by 36%, and VRE CLABSIs by 33% on the units that were using CHG daily bathing. There were no changes in the rate of MRSA-related HCAI metrics.

This study performed in a large number of community hospitals (rather than large academic teaching hospitals) provides real-world data that CHG bathing reduces the rate of important HCAIs. However, it also illustrates that CHG bathing is not a silver bullet and needs for form part of a multifaceted strategy to prevent HCAI on ICUs.

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