The physical environment and norovirus containment

noro
As norovirus season gets into full swing, spare a thought for those hospital that still have open plan ‘Nightingale’ style wards. These worked for Florence in a Victorian era, but narrow bed spacing and a lack of single rooms makes the containment of infectious diseases very challenging in these wards.
 
A study just published in the Journal of Infectious Diseases puts some numbers to this risk, finding that the frequency of norovirus outbreaks varied hugely across 6 hospitals in the London area. With 2 or fewer outbreaks reported in 5/6 and a whopping 16 separate outbreaks in one of the hospitals. This hospital had the lowest proportion of single rooms (a miserly 7%) and the tightest bed spacing (2.3m between bed centres), and the authors attribute these structural challenges to the frequent outbreaks in these hospitals.
 
Managing norovirus in these challenging ward environments may require some additional measures. Whilst effective hand and environmental hygiene are the key to controlling the spread of noro, this needs to be complemented with effective isolation of patients. Perhaps more segregated cohorting of patients would be a way to tackle segregation of patients with diarrhoea and vomiting in Nightingale wards? But the real solution to address this issue is to increase the number of single rooms in new hospitals!

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Shocking news about chlorhexidine

There is some evidence that passing electricity through a biocide enhances its biocidal activity – a so-called ‘bioelectric effect’. At the molecular level, biocidal activity depends on some sort of chemical interaction at a molecular level. Things tend to happen more quickly in chemical reactions when you add more energy – to a point. And it is likely to be the same with electricity added to a biocidal chemical reaction.
 
And so it is perhaps no surprise that a team of researchers from Belgium found that Porphyromonas gingivalis (an important organism in dentistry) biofilms were inactivated further by chlorhexidine when a 10mA current was run through them. The effect was not identified when a 1.5mA current was used, and the effect was actually fairly modest even with the 10mA current (87% vs 99% reduction, around a 1-log difference).
 
Assuming there is a measurable ‘bioelectric effect’ associated with chlorhexidine, how could this benefit be realised in practice? It’s perhaps possible to introduce a low electric current into specific points of the mouth during dental treatment, but the skin is a lot more tricky. Believe it or not, applying an electric current to the skin is used as a way to improve drug delivery, so perhaps the idea isn’t a far-fetched as it may seem!
 
Chlorhexidine is an excellent biocide, but its effectiveness is reduced by biofilms (as is the case for all biocides) and Gram-negative bacteria are relatively less susceptible to chlorhexidine than Gram-positive bacteria in laboratory studies. Electrifying the skin therefore, terrifying as it may sound, could be a way to help to address these challenges! electric

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Evidence of source control for XDR Acinetobacter outbreak management grows

There is a steadily growing body of evidence that chlorhexidine washcloths can be effective in controlling multi-resistant Gram-negatives. Hot on the heels of a paper that demonstrated the effectiveness of the in controlling spread of Acinetobacter in a critical care unit1 comes a further paper relating to a hospital-wide outbreak of multi-resistant Acinetobacter. A new paper2 from Gray and colleagues from Montreal, Canada just published ‘in press’ in the Journal of Hospital Infection reported on the measures that they implemented to bring about control of the largest XDR Acinetobacter baumannii outbreak in the country to date. The outbreak, involving a single clonal strain, took place in multiple units of a large hospital, although transmission occurred on just two wards in the main. Interestingly, although carriage was detected at multiple sites on patients, only 57% were found to be rectal carriers.

Specific control measures included the creation of a cohort area on a ward with a strong culture of infection control and a patient population at lower risk of progressing from colonisation to infection. All affected wards underwent rigorous decontamination and additional training was provided to healthcare workers. XDR-Acinetobacter cases were provided with dedicated equipment and were bathed daily with 2% chlorhexidine gluconate-impregnated wipes as a source-control measure. Other general measures also included audits of compliance with hand hygiene and environmental decontamination, with feedback being given to staff.

Screening was in interesting aspect of this study. The fact that nearly half of patients were not rectal carriers contrasts markedly with CRE, for which rectal screening is considered sufficient to reliably detect carriage. This study highlights the need to sample a large number of body sites in order to exclude colonization with confidence.

In their discussion, the author express surprise that chlorhexidine bathing has been omitted as a control strategy in recent reviews, despite a number of papers that suggest that it is effective. Other work, including a study in a long-term facility has reported on the use of this strategy to control an Acinetobacter outbreak3. A 53% reduction in the incidence of Acinetobacter infection was reported in a long-term acute care facility following the introduction of chlorhexidine baths every other day for cases, and weekly for non-cases. The more intensive daily protocol used in this Canadian study may partially account for the greater success in controlling this outbreak.

1) Chung, Y. K., J. S. Kim, S. S. Lee, J. A. Lee, H. S. Kim, K. S. Shin, E. Y. Park, B. S. Kang, H. J. Lee and H. J. Kang (2015). "Effect of daily chlorhexidine bathing on acquisition of carbapenem-resistant Acinetobacter baumannii (CRAB) in the medical intensive care unit with CRAB endemicity." Am J Infect Control 43(11): 1171-1177.

2) http://www.journalofhospitalinfection.com/article/S0195-6701%2816%2900005-0/abstract

3) http://www.atsjournals.org/doi/abs/10.1164/ajrccm-conference.2009.179.1_MeetingAbstracts.A1427

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