A recent Korean study underlines the value of daily chlorhexidine bathing, demonstrating a reduction in the trend of MRSA incidence in a high-prevalence ICU setting. The study also underlines the threat of reduced susceptibility to chlorhexidine emerging, which may begin to erode gains that have been made through the introduction of chlorhexidine.
The study was performed in a 16 bed medical ICU in Korea. Following a 14-month control period, daily bathing using chlorhexidine was introduced. During the control period, pre-emptive isolation of all admissions occurred until they were demonstrated to be MRSA-negative, and enhanced environmental measures were already in place. The rate of MRSA carriage on admission to the unit was very high, at around 25% of admissions (much higher than you’d expect to see in the UK). The rate of MRSA BSI was high also, with 13 in the control period also. This is more than most large hospitals in the UK see in an entire year! So, this was a setting of very high MRSA prevalence.
The results suggest that the introduction of chlorhexidine bathing improved the MRSA picture: the rate of acquisition was reduced by 23% from 21 to 16 per 1000 patient days, the number of MRSA BSI reduced from 13 to 5, and the incidence density showed a significant reduction during the intervention phase. Whilst the reduction in MRSA acquisition and BSIs were not statistically significant, the trend was in the right direction. It was difficult to interpret the findings around the possibility of reduced chlorhexidine susceptibility, because only isolates from the intervention phase were available for analysis. However, the presence of genes associated with chlorhexidine susceptibility, and the proportion of isolates less susceptible to chlorhexidine were greater in the incident isolates compared with the prevalent isolates, suggesting that the MRSA transmitting on the unit was less susceptible to chlorhexidine.
Importantly, the rate of compliance with hand hygiene and contact precautions was monitored throughout the study, and found not to vary significantly between the control and intervention periods. Although the study was a pre-post design, without a concurrent control or randomisation, the results are impressive, reinforcing the findings of other studies that chlorhexidine daily bathing can reduce the transmission of key hospital pathogens.
There has been much discussion on the transmission routes of the MERS coronavirus (MERS-CoV). Initial studies suggested that contamination of air and surfaces could be important in the transmission of the MERS-CoV. A recent study in Clinical Infectious Diseases evaluated the extent of air and surface contamination surrounding patients during MERS-CoV outbreaks in 2015 in South Korea.
A high rate of both air and surface contamination was identified. 4/7 air samples from two patient’s rooms a bathroom and a common corridor were contaminated with MERS-CoV, and 15 of 68 surfaces were found to be contaminated with MERS-CoV by viral culture. The finding of viable MERS-CoV in a common corridor is of particular concern, and, although asymptomatic shedding could have been involved, this suggests that MERS-CoV was not contained during the outbreak.
These high rates of contamination of both surfaces and air suggest that either or both could be involved in the transmission of MERS-CoV.
We have known for a while that Acinetobacter baumannii can cause widespread contamination of surfaces and air. But it’s difficult to know how much of a transmission risk this causes. Is contamination of surfaces a cause or effect of transmission? And is contamination of the air an intermediate step between the patient and the surface, or a problem in its own right? A recent US study does not answer these questions, but does offer some useful data on the scale of surface and air contamination emanating from infected and colonised patients.
Extensive air and surface sampling was performed around 25 carbapenem-resistant A. baumannii patients in the ICU. The key finding is that contamination of the air and surfaces was significantly greater around patient who were rectally colonised (38% for air and 16% for surfaces) compared with patients who had colonisation of the respiratory tract (13% for air and 10% for surfaces). This seems a little backwards – you may expect a patient colonised in the respiratory tract to release more resistant bacteria into the air, but on the basis of this study, this does not seem to be the case. This apparent discrepancy may be explained by the presence of closed-circuit ventilation for many patients who had respiratory colonisation.
This study again highlights the risk of environmental contamination surrounding patients with A. baumannii and underlines the need to address contaminated surfaces and probably air too when formulating strategies for preventing the spread of A. baumannii.
A useful review by Weber et al. explores data from studies with a clinical outcome evaluating UV and hydrogen peroxide automated room (ARD) decon devices. There are now quite a few studies showing that admission to a room previously occupied by a patient with a pathogen associated with HCAI (including C. difficile, MRSA, VRE and others) increases the chances of acquiring these pathogens due to surface contamination that is not dealt with by standard cleaning and disinfection approaches. There is also a sound evidence base showing that both UV and hydrogen peroxide ARD systems do a better job of reducing microbial loads on surfaces than standard cleaning and disinfection. However, evidence from studies linking these environmental reductions to clinical outcomes are rarer, but increasing.
The focuses on some key studies evaluating the clinical impact of ARD systems. There are some convincing studies for HPV (including the impressive Passaretti and McCord studies), and for UVC systems, which put out a continuous dose of germicidal UV (including Napolitano and the much-anticipated BETR-D study). Whilst there are quite a few studies which, on the face of it, suggest that PX-UV, which puts out a pulsed dose of broad spectrum UV, also reduces HCAI, many of these studies have important confounding factors, making it difficult to attribute the reduction specifically to the UV device. For example, in the study by Fornwalt, PX-UV was introduced as a part of a quality improvement programme, and in the study by Simmons, PX-UV was part of a multi-faceted bundle.
The review concludes that ‘A growing number of clinical studies have demonstrated that ultraviolet devices and Hydrogen Peroxide systems when used for terminal disinfection can reduce colonization or health care-associated infections in patients admitted to these hospital rooms.’
We have known for a while that mobile devices are an emerging risk for harbouring hospital pathogens. But it was interesting to see a new study evaluating the rate of contamination with Candida sp. on the surface of phones. 175 phone screens from a Polish hospital were sampled, and a whopping 75% were contaminated with Candida sp! Interestingly, there was no correlation between the behaviour of healthcare workers in terms of cleaning their phones and the rate of contamination. But perhaps this is unsurprisingly given only 20% of healthcare workers actually cleaned their phone!
Phones are fast becoming an extension of ourselves, but the policies for the appropriate management of phones and other mobile devices used by healthcare workers seem to be slow to come through. Perhaps it would be useful to classify healthcare workers’ mobile phones as medical devices?