There has been some recent discussion on whether we should implement screening for asymptomatic carriage of C. difficile. Whilst there is some evidence that cross-transmission of C. difficile from symptomatic cases is rare (in English hospitals, at least), a recent study shows that asymptomatic carriers are an important source of in-hospital transmission of C. difficile.
The study was performed over 4 months in a Danish ICU. All admissions were screened for asymptomatic carriage of C. difficile. The key outcome was that exposure to a C. difficile asymptomatic carrier resulted in an increased risk of C. difficile infection: C difficile infection was detected in 2.6% of patients not exposed to carriers and in 4.6% of patients exposed to asymptomatic carriers (odds ratio 1.8, 95% confidence interval 1.2-2.8). Put another way, patients exposed to asymptomatic carriers were approximately twice as likely to develop C. difficile infection!
One unique aspect of the study was that hospital staff were blinded to the C. difficile carriage status of the patients on the unit. This means that no attempts were made to reduce the risk of C. difficile transmission from known carriers. So, the study provides some tantalising evidence that improving the management of known C. difficile carriers (perhaps through isolation and enhanced disinfection) could reduce the incidence of C. difficile infection.
Patients with C. difficile diarrhoea will shed a lot more spores and need to remain the key focus of prevention and control initiatives. However, this study suggests that asymptomatic carriers should be a separate focus of prevention and control interventions.
We recently posted a blog on a review and meta-analysis on the increased risk of acquiring key hospital pathogens from the prior room occupant. A similar review and meta-analysis has just been published focussing on the ICU environment. The new study highlights the 5-fold increase in risk of acquiring Acinetobacter when the previous room occupant had this pathogen!
The main result is the same from both meta-analyses: the risk of acquiring MRSA, VRE, C. difficile, Acinetobacter, Pseudomonas, and Klebsiella or E. coli is approximately doubled when patients were admitted into rooms where the previous occupant had these pathogens. The presentation of the data grouped by organism in the most recent review draws attention to a greater increase in risk from one pathogen in particular: Acinetobacter. There was a
5-fold increase in risk for this pathogen, which was itself double the increase in risk for all pathogens combined, suggesting that Acinetobacter is somehow "more environmental" than the others*. Whilst differences in study design and setting may go some way to explain this, this is plausible:
we know that Acinetobacter is shed in high quantities and has
exceptional survival properties.
In the previous post, we reiterated the need to redouble our efforts to tackle contamination of the hospital environment based on these findings, especially at the time of patient discharge, in order to mitigate or even eliminate this increased risk through:
- Improving the cleaning / disinfection process
- Developing new modalities to make cleaning / disinfection easier
- Producing novel disinfectants
- Improved design
- Reduced patient shedding
- Considering antimicrobial surfaces
- Implementing automated room decontamination (ARD)
We now know that being admitted to a room where the previous room occupant had a pathogen is a risk factor for the incoming occupant in acquiring these pathogens, and that improving the quality of terminal cleaning and disinfection mitigates or removes completely this increased risk. So, let's get out there and ensure that all rooms are clean, safe, and ready to deliver the highest quality of care to our patients.
*Only one of the studies included C. difficile, which was performed in an outbreak setting - we would expect future studies to show a higher increased risk for acquiring C. difficile from the prior room occupant!
A multicentre US study has shown that hospital floors can be a source of pathogens that can cause HCAI. Floors were heavily contaminated, high-touch items were in frequent contact with floors, and hands became contaminated with hospital pathogens as a result of contact with these items. Anybody who dismissed hospital floors as a potential transmission risk are missing a trick!
Historically, floors have been considered a minor risk in terms of transmitting hospital pathogens, and the focus has been on the disinfection of high-touch surfaces. In order to assess the potential for cross-transmission, a group of five hospitals collaborated to study the frequency of contamination of hospital floors and whether high-risk objects could be a contaminated as a result of contact. Around half of the 318 floors sampled in 159 patient rooms were contaminated with C. difficile (regardless of if the patient had C. difficile infection or not, and whether or not the patient had been discharged and terminal disinfection performed), and between 10 and 30% of floors were contaminated with MRSA and VRE. Amazingly, a point prevalence survey found that 41% of the rooms had one or more high-touch surface in contact with the floor. These objects transferred C. difficile to 3%, VRE to 6%, and MRSA to 18% of researcher hands following contact.
What we need now is a good quality intervention study to show that enhanced disinfection of floors (perhaps using our Sporicidal Granules) reduces the transmission of hospital pathogens. Any takers?
A randomised controlled study with a clinical outcome compared the impact of chlorhexidine, octenidine, and povidone iodine used for cutaneous antisepsis for preventing line infections associated with intravascular catheters. Chlorhexidine knocked spots off the competition, with patients randomised to chlorhexidine significantly less likely to develop line-relates sepsis or bacterial contamination when compared with octenidine or povidone iodine.
57 patients were randomised to either 4% chlorhexidine gluconate, octenidine hydrochlorodine, or 10% povidone iodine for cutaneous antisepsis prior to insert and during the use of intravascular cathethers. 1 in 10 patients randomised to octenidine and povidone iodine developed cathether-related sepsis, compared with none in the chlorhexidine group (p<0.001) (see Table below). Also, catheter-related colonisation occurred in 26% of patients in the povidone iodine group, 21% in the octenidine group, and none of the patients in the chlorhexidine group. Importantly, there were no significant differences between baseline characteristics of the patients randomised to the three different antiseptics.
Table: Clinical outcomes associated with 57 patients randomised to three difference cutaneous antiseptics.
This study supports the use of chlorhexidine as the antiseptic of choice for preventing catheter-line associated infections.
A new study in BMC Infectious Diseases models the impact of various cleaning strategies on the transmission of MRSA. Regular wiping of high touch surfaces was more effective than daily cleaning of the whole room in preventing the transmission of MRSA.
The study team created a simple mathematical model to explore the transmission of MRSA. And herein lies the main limitation: “all models are wrong, but some are useful“! The real challenge with modelling studies is whether we really know enough to accurately ‘parameterise’ the model. Also, even when there is data for a given variable (e.g. the amount of MRSA that is shed by a patient into the environment), this will vary greatly (e.g. where the patient is infected or colonised, strain of MRSA, how mobile the patient is, and environmental factors such as airflow, and others). Models like this have to come up with mathematical ways to model all of these uncertainties. So, you can see why some people think that mathematical models are not really that useful. However, they allow us to explore transmission pathways in a way that would be extremely challenging to do, and sometimes not possible to do, using experimental studies.
The study evaluated the transmission of MRSA from one patient to another who were in adjacent hospital rooms. The key variables were the type of cleaning (either irregular cleaning of the whole room), or wiping of touch points (variable frequency of cleaning high and low touch points). The main finding was that regular cleaning of touch points in the room was much more effective than once daily cleaning of the entire room. The effectiveness of wiping touch points in preventing transmission increased with the frequency of wiping, perhaps unsurprisingly!
Further work is required to confirm this observation (this is a modelling study after all), but this idea could change the way that we approach hospital cleaning and disinfection. Could we start talking in terms of the “Five Moments for Environmental Hygiene” to mirror the “Five Moments for Hand Hygiene”? Should healthcare workers disinfect each surface that they touch? Or perhaps the same wipe should be used to disinfect both hands and surfaces following each of the Five Moments for Hygiene?! Just thoughts at this stage, but this study certainly does make you think!