Infection Prevention 2015 (the annual conference of the Infection Prevention Society) has just wrapped up in Liverpool so we thought we’d share some of the key updates around environmental science.
Martin Kiernan gave a great lecture on the importance of the contaminated environment in the transmission of multidrug-resistant Gram-negative rods. Historically, the general view has been that Gram-negative bacteria don’t survive well on surfaces, but recent data has suggested that this is often not the case. The non-fermenters (especially A. baumannii) survive well on surfaces, with survival times measured in months. Even the Enterobacteriaceae including highly resistant CPE (especially K. pneumoniae) can also exhibit surface survival times measured in months. Indeed, Professors Peter Hawkey and Ed Septimus also gave lectures highlighting the potential role of surface contamination in the transmission of resistant Gram-negative bacteria. Martin also discussed the relative recent finding that biofilms on dry hospital surfaces probably play an important and previously unrecognised role in facilitating the survival of Gram-negative bacteria; indeed, one study found that biofilm-producing A. baumannii showed longer surface survival times than non-biofilm-producing strains. There is evidence that even thorough, repeated bleach disinfection does not eliminate reservoirs of A. baumannii, so perhaps it’s no surprise that admission to a room previously occupied by a patient with A. baumannii is a risk factor for acquisition! So what can be done to address surface contamination with Gram-negative bacteria?
- Using objective measures (such as fluorescent markers) to improve the cleaning process can help.
- The use of chlorhexidine to reduce shedding of bacteria from patients can reduce environmental contamination, and a recent study suggests that it can reduce the transmission of carbapenem-resistant A. baumannii.
- Automated room decontamination methods may play a role.
- And we need to develop a new generation of disinfectants with biofilms in mind!
All of the abstracts from the conference are published in an open access download from the Journal of Infection Prevention.
- A poster from the Royal Free (Abstract ID: 3781) evaluated the staff acceptability of Clinell’s Universal and Sporicidal wipes to replace the previous protocol of chlorine solution diluted daily in buckets. Of the 100 staff surveyed, more than 90% agreed that the wipes were easier to access, more visible, easier to use, appeared effective, and would reduce the risk of dilution errors. As you would expect, the ease of use associated with wipes compared with a conventional “bucket method” was the most striking outcome of the survey.
- A poster from UCLH (Abstract ID: 3764) found that a fairly shocking 35% of surfaces in the near patient environment were contaminated with C. difficile after terminal disinfection with a sporicidal agent! Ribotyping and whole genome sequencing were used to investigate the relationship between environmental and patient isolates, and identified at least one case of environmental cross-transmission.
- As we all move towards mobile communication devices in our personal and professional lives, the tricky question about how and when to disinfect them is posed. A poster from Qatar (Abstract ID: 3772) evaluated a number of different methods for disinfecting an iPad experimentally contaminated with S. aureus. Brief exposure to UV light was the most effective method, achieving a 3-4 log reduction with a 60 second exposure.
- A study of a UVC room disinfection device from Royal Wolverhampton NHS Trust (Abstract ID: 3776) showed a statistically significant reduction of bacterial contamination compared with conventional manual cleaning, in line with other studies.
- Important research from PHE (Abstract ID: 3824) demonstrates that a number of commercial disinfectants are ineffective against some Gram-negative bacteria at their in-use concentration (see this review for more details here). Furthermore, Gram-negative bacteria tested in biofilms rather than planktonic cultures were even less susceptible to disinfectants. Finally, exposure to sub-lethal doses of some biocides resulted in further reduced susceptibility and antibiotic cross-resistance. This early-phase laboratory research raises some interesting questions and demonstrates the challenges that resistant Gram-negative bacteria pose to disinfection.
Thanks to the IPS for another great conference!
There’s been some fascinating data published in recent years using micro cultures to evaluate the chances of healthcare workers (HCW) acquiring hand contamination with pathogens from surface contact. Surprisingly, the chances of hand contamination are just about equal regardless of whether you touch a patient direct, or their surrounding surfaces for MRSA, VRE and C. difficile. A new study uses modelling to evaluate the interplay between contamination of air, surfaces, and hands in a simulated single room and four bed bay.
The main finding is that the type of care delivered is the most important factor in determining hand contamination, with personal care resulting in most contamination. The number of surface contacts and surface distribution of microbes were also important factors, but less so than the type of care delivered. A reduction in ventilation rate from an already low 6 air changes per hour to an even lower 4 air changes per hour made little difference. As you may expect, the single room was considerably better at containing contamination than the four bed bay.
Although personal care was the most important factor in predicting HCW hand contamination, there’s not a lot that can be done about this. Hospital patients will always need this level of close physical contact. Clearly this does underline the need for rigorous hand hygiene following patient contact. But the other factors identified can be addressed: improvements in surface disinfection would reduce the risk of hand contamination. And this may be doubly important because HCWs are less likely to perform hand hygiene after contact with a surface than after contact with a patient. It may also be feasible to reduce the number of surface contacts during patient care through a process of re-education. If HCW had at the forefront of their mind that surfaces around patients are likely to be heavily contaminated, would they touch these surfaces as much? Probably not. Finally, although the number of air changes in a room could be increased, this study suggests that this would not have a great deal of impact on HCW hand contamination rates.
This is an important study, which highlights the links between air, surface and hand contamination, and suggests that improving surface disinfection would reduce the rate of HCW hand contamination and the risk of onward transmission.
p>Infection Control Today (ICT) recently released a new report on wipes. The concise report neatly outlines the key benefits of wipes over traditional “mop and bucket” methods, namely assurance of correct dosage, no need to repeatedly dip into an in-use solution (which risks contamination of the solution), and perhaps most importantly, convenience. This can lead to better compliance with cleaning protocols, improved staff satisfaction, faster room turnaround, improved impact in terms of microbial reduction, and, in some circumstances, cost savings.
The report highlighted a recent study that performed a useful cost effectiveness study, accounting for the time taken to clean the room with wipes vs. a traditional bucket method. Cleaning the room using wipes took an average of 178 seconds vs. 231 seconds with the traditional method, resulting in a cost saving per employee day of $38.58 (around Â£25). This doesn’t sound much, but multiply this by all of the cleaners in the hospital (let’s say there are 100) and all the days in the year, and you get to almost Â£1m! So, even if the material cost for the wipes is higher than for the traditional bucket method, time savings may make the process cost-saving (in addition to the other benefits).
The ICT report covers some useful technical aspects about how good wipes function, including their loading ratio, and disinfectant absorbance and release. But which wipe to choose? There is no shortage of choice in the marketplace, from detergent wipes with no disinfectant activity at all to sporicidal wipes with efficacy against C. difficile spores. Which wipe you choose will depend on your intended purpose. There are probably three key uses of surface wipes in hospitals: cleaning a surface (with no need for disinfection), disinfecting a surface (without inactivating C. difficile spores) and disinfecting a surface (inactivating C. difficile spores). Now that good quality disinfectant / detergent wipes are available (such as the Green Clinell Universal Wipes), the use of detergent only wipes is declining sharply. Meanwhile, the continued problems caused by C. difficile necessitates the use of a sporocial wipe on occasion (such as the Red Clinell Sporicidal Wipes, or a chlorine wipe).
But how to choose between the wipes from various manufacturers with similar and overlapping claims? One of the key factors is efficacy and published data, and, for example, a recent Cardiff study put a range of detergent wipes through their paces, concluding that some did not do what they said on the tin. Efficacy will not be the only factor in deciding which wipe to purchase, but it’s a start!
A powerful study from Korea demonstrates the value of chlorhexidine gluconate (CHG) daily bathing of ICU patients to reduce the transmission of carbapenem-resistant Acinetobacter baumannii (CRAB). Where enhanced screening, contact precautions and environmental disinfection failed, the introduction of CHG daily bathing made an impressive reduction in the transmission of CRAB.
The study was performed in a 16 bed ICU, with a 14 month control period, and a 12 month intervention period. The authors evaluated how many patients were identified as carrying CRAB within the first 48 hours of their admission to the ICU (‘prevalent’ cases) and those that were first identified as carrying CRAB after 48 hours on the ICU (‘incident’ cases). Universal admission screening was in place throughout the study, meaning that the incident cases are presumed acquisitions. In the control period, 21% of 593 eligible admissions acquired CRAB compared with 10% of 554 admissions in the intervention period (incidence density reduced from 44 to 21 per 1000 at-risk patient days, p<0.001) (see figure below). A time series analysis confirmed a significant reduction in the incidence density of CRAB associated with the introduction of CHG.
Figure legend: Rate of acquisition and environmental contamination in the control and intervention periods
The authors also compared environmental contamination at one timepoint in the control period, with four timepoints in the intervention period. The proportion of sites contaminated with CRAB in the intervention period was significantly lower than in the control period (30% of 127 vs. 10% of 540) (see figure above). It is not clear whether this is due to reduced shedding of CRAB from affected cases, or due to the fact that there were less cases around due to reduced transmission; it seems likely that both contributed to the reduction in CRAB environmental contamination.
Meanwhile there was no significant change in the prevalence of CRAB on the unit, compliance with hand hygiene or contact precautions, providing firm evidence that the reduction was not due to reduced importation of CRAB into the ICU, or improvements in infection control.
Due to the potential risk for CRAB developing reduced susceptibility to CHG, the authors tested the MIC and MBC of prevalent and incident cases identified during the intervention period. (It was a shame they didn’t compare cases from the control period with the intervention period – but the isolates from the control period were not saved.) They found no significant different between the MIC/MBC of prevalent and incident cases, suggesting that the daily use of CHG did not result in reduced susceptibility. It’s worth noting that the median MIC/MBC was 32 mg/L, and the concentration of CHG applied to the skin was in the region of 1000x more concentrated than this, making clinically significant reduced susceptibility a distant possibility.
One of the most striking aspects of the study is the extremely high levels of CRAB on the unit. Combining prevalent and incident cases suggests that a whopping 47% of 593 eligible patients were affected by CRAB at some point during their admission. These very high levels of CRAB probably limit the generalisbility of the findings to units with a lower admission prevalence. Notwithstanding this, there was a clear step-change in the rate of CRAB acquisition associated with the introduction of CHG daily bathing, suggesting that this intervention should be performed to reduce the transmission of CRAB.
A review in a very high impact journal (Annals of Internal Medicine) has addressed cleaning and disinfection strategies to prevent HCAI. Whilst it is great to see this issue addressed in a general, high impact medical journal, there are a number of important limitations to the review.
Firstly, it only includes data on MRSA, C. difficile and VRE. This is a shame, because it means that emerging data on the role of the environment in the transmission of Gram-negative bacteria – most crucially Acinetobacter baumannii – is excluded. It also means that there is no data on viruses such as norovirus, which limits the impact of the review. Secondly, it is very US centric, only including products or process available or under evaluation in the US. Thirdly, the scope of the literature review seemed to exclude some key literature, not least the statement that: ‘No conference abstracts within the past 2 years were identified for inclusion‘, which certainly does not match our experience of recent conferences! Finally, there is poor resolution between the various automated room disinfection systems that are available, lumping together all hydrogen peroxide technology together, and doing the same for UV. This is disappointing, since we now know that there is a vast difference in the impact of UVC vs. pulsed-xenon UV, and between hydrogen peroxide vapour vs. aerosol systems.
The figures in the review are useful, providing a visual summary of the relative weight of evidence behind the various approaches to improving cleaning and disinfection in hospitals. The ‘evidence hierarchy’ adapted from the McDonald & Arduino version is also useful, providing a different perspective on how far up the hierarchy the various approaches have made it. However, it’s important to note that the interpretation of these figures should be tempered by the fact that the review only included data from the US!
The key evidence gap identified is that there are few good quality studies with a clinical outcome (i.e. reduced infection or colonisation), which is a function of how difficult it is to perform these studies. However, a number of these are in progress, so this should improve over the coming years.
It seems clear that there is compelling evidence behind a number of usually complimentary but occasionally conflicting approaches, suggesting that several interventions to address environmental hygiene could be used simultaneously. Specifically, conventional cleaning and disinfection can be improved through implementing better disinfectants and processes for delivery by using wipes that are demonstrably effective against the target pathogens. It is also vital that monitoring processes are undertaken more rigorously and can provide organisations with data that demonstrate safe preparation of areas for patient occupancy. In addition, automated room decontamination systems can provide additional assurance that rooms are clean and safe for the next occupant.