PPE for preventing highly infectious diseases

Schermafbeelding 2016-04-27 om 15.32.54

The use of PPE and the protection of HCWs against highly infectious diseases was (and is) a topic of major importance, around the globe. The recent Cochrane review by Verbeek et al. was probably hoping to offer this “vital” information.

Unfortunately, they found no studies on the effects of goggles, face shields, long-sleeved gloves or taping on the risk of contamination. All they found was very low quality evidence, with high risk of bias and uncertain estimates of effect, that:

  • More breathable types of PPE offer more comfort without increasing the risk of contamination
  • Double gloving and CDC doffing guidance appear to decrease the risk of contamination, and
  • Active more than passive training in PPE use may reduce PPE and doffing errors.

Their conclusions are obvious: we need high-quality studies of the materials, their use and protective effects, safe ways of doffing, and the most adequate training to achieve safe use of PPE for HCWs in the presence of highly infectious diseases or those (even less infectious) that may cause severe harm to HCWs.

But what to do until than? My personal opinion is that we should only use PPE, we are used to and know how to use. First-time users, even if supplied with the best available products, will inevitably fail to remove the PPE without error. Consequently, institutions should have a stable selection of PPE, and in the case of preventing highly infectious diseases, a selected group of HCWs with continuous active training, as it is too late to start when the next epidemic is hitting our healthcare centers.

Schermafbeelding 2016-04-27 om 14.47.06

MERS-CoV: a survival guide for you and your patients

This time last week, we were on red alert that a MERS-CoV pandemic was gathering pace. The news over the last few days has been more encouraging, with no new cases reported in Saudi Arabia, the epicenter of the MERS-CoV cases. However, there are still plenty of patients with MERS-CoV who need to be cared for around the world. Like SARS-CoV, but unlike the “usual suspects” that cause HCAI such as MRSA and C. difficile, MERS-CoV has the capacity to affect both healthcare workers and patients. Thus, I hope that this ‘survival guide’ will prove useful to those on the front line.

I presented a webinar on ‘MERS-CoV: coming to a hospital near you? Infection prevention and control challenges’. You can download the slides here. I came across a fantastic blog whilst preparing the webinar: ‘Virology Down Under’ by Dr Ian Mackay. I’ve used some of his excellent images in the slides, with his kind permission.

There are two transmission routes to consider for MERS-CoV: droplet / aerosol and contact / fomite. CDC recommends both airborne and contact isolation procedures to reflect these transmission routes. This involves placement of the patient in a negative pressure airborne infection isolation room, and the use of gloves, gowns, eye protection and N95 (FFP3) mask, and, of course, hand hygiene. PHE recommends a similar approach.

First and foremost, as a respiratory virus, inhalation of infected droplets is likely to be the most important transmission route. However, whilst not an ‘airborne’ virus (such as measles), aerosols can be generated by MERS-CoV patients that comprise small droplet nuclei that travel for long distances. A recent study of influenza suggests that the generation of aerosols is surprisingly common, to the extent that ‘living and breathing is an aerosol generating procedure’. Indeed, a recent study showed that a MERS-CoV aerosol diminished by only 7% over 10 minutes (compared with 95% for influenza). The use of an N95 (FFP3) mask will prevent direct inhalation of droplets / aerosols, and gloves, gowns and eye protection will prevent contact with mucous membranes and contamination of clothing or hands for subsequent nasal inoculation. But, if MERS-CoV aerosol is generated in the patient’s room (which seems likely), how long will it last and will the subsequent admission to the next room be at risk?

Let’s assume a patient sheds a MERS-CoV infectious aerosol of 6-log. I’m not aware of any infectious dose data for MERS-CoV yet, but for SARS-CoV it can be as low as <20 plaque forming units. Given the decay rate of 7% over 10 minutes, infectious aerosol above the infectious dose could be present after the discharge of the patient for a little under 26 hours! Even if the virus was shed at a lower titre, infectious aerosol times would still be considerable (Table). Could this be a job for automated room disinfection systems, which address both surface and airborne contamination? One such system, hydrogen peroxide vapour, has recently been shown to inactivate the SARS-CoV surrogate, TGEV.

Shed titre Time to reach 20 virus particles
1000000 26 hours
100000 20 hours
10000 15 hours
1000 9 hours
100 4 hours

Table: Relationship between shed titre of MERS-CoV and time to reach 20 virus particles.

Whilst respiratory viruses are not that great at surviving on surfaces compared with C. difficile spores and some vegetative bacteria, they can survive long enough to bring contact / fomite transmission into play. A number of reviews have concluded that contact / fomite transmission is an important route for influenza and other respiratory viruses such as rhinovirus. The SARS-CoV and surrogates exhibit unusual survival properties compared with other respiratory viruses, with survival times often measured in days, weeks or even months. Recent data suggests that MERS-CoV shares this property, surviving for >2 days when dried onto hard surfaces compared with only a few hours for influenza tested in the same study. Fortunately, these enveloped viruses are inactivated rapidly by usual hospital disinfectants, so I can understand the CDC’s recommendation for standard environmental disinfection.

So, how to protect yourself and your patients? The answer is simple for direct patient care: wear your gown, gloves, goggles and N95 (FFP3) mask, and wash your hands! It’s simple in theory, compliance with these measures in practice is not as good as you may expect. Prof Seto published a study in the Lancet in 2003 about compliance with personal protective equipment (PPE) and hand hygiene during the SARS epidemic. Remarkably, even when caring for patients known to be infected with SARS, <30% of healthcare workers self-reported that they wore a mask, glove, gown and washed their hands as they should have done. And this was self-reported, so you’d expect there to be a bias towards compliance! Most importantly, none of the healthcare workers who complied with all four measures became infected.

Seto Lancet SARS PPE

Figure: Healthcare worker compliance with mask, glove, gown use, and hand washing during the SARS epidemic, stratified by those who became infected with SARS.

To summarise: how to protect you and your patients from MERS-CoV:

  • Place patient in negative pressure airborne infection isolation room, where available.
  • Wear the correct PPE when in the room (gloves, gown, N95 / FFP3 mask, goggles), and wash your hands.
  • Pay attention to the potential for contaminated surfaces and air, particularly following the discharge of the patient.
  • Oh, and if you go on holiday to Saudi Arabia, don’t kiss any camels!

This study has been BUGGing me for a while

bug glove

A fabulous study recently published in JAMA evaluates the ‘Benefits of Universal Glove and Gown’ (BUGG) in US ICUs. This is a model study design: one of the first cluster randomized controlled trials of a non-therapeutic infection control intervention. Twenty ICUs were paired and randomized to either universal glove and gowning, or to continue the current practice of placing patients known to be infected or colonized with MRSA and VRE on contact precautions. The hypothesis is that undetected colonization with MRSA and VRE is common, and the only real way to address this is to assume everybody is colonized!

Summary of findings:

  • Universal glove and gowning was not associated with a reduction in a composite measure of MRSA / VRE acquisition (the primary outcome).
  • VRE acquisition was not reduced by universal glove and gown use, whereas MRSA was.
  • CLABSI, CAUTI and VAP; ICU mortality; and adverse events did differ significantly between the two groups.
  • Hand hygiene compliance on room entry was not significantly different between the two arms, whereas hand hygiene compliance on room exit was significantly higher in the intervention arm.
  • Healthcare workers visited patients 20% less frequently in the intervention arm (4.2 vs. 5.2 visits per hour).

BUGGFigure: The change in acquisition rate, comparing the baseline period with the study period for the intervention and control units.

Here’s what’s BUGGing me about this study:

  • The acquisition rate in both intervention and control study arms reduced (Figure). The acquisition rate reduction in the control arms may be due to improved compliance with admission screening, resulting in more accurate ascertainment of who required contact precautions.
  • The significant reduction was achieved for MRSA but not for VRE. The authors suggest that VRE colonization may have been suppressed on admission and not detected, and flourished during antimicrobial therapy giving the impressive of acquisition. I wonder whether differences in the routes of transmission may also have contributed; for example, VRE seems to be substantially “more environmental” than MRSA. Another potential confounder is that, by chance, the prevalence of MRSA or VRE on admission to the intervention ICUs was more than double that in the control ICUs (22% vs. 9%). In actual fact, the raw rate of MRSA acquisition in the intervention ICUs was marginally higher than in the control ICUs during the intervention period (6.00 vs. 5.94 per 1000 patient days), even though the change in rate was significantly greater on the intervention ICU. Although adjustment was made for this difference in the analysis, it may have skewed the findings somewhat.
  • The authors achieved remarkably high compliance with admission screening (around 95%), discharge screening (around 85%) and glove and gowning (around 85%). Each site had the luxury of a study coordinator and a physician champion to lead implementation, plus weekly feedback on screening compliance and visits from study investigators. Most ICUs would not be afforded these luxuries so I suspect that real-world compliance outside of the somewhat artificial study environment would be considerably lower. Indeed, an ID Week poster suggests that compliance with gowning in one US ICU was a ‘dismal’ 20%!
  • Adverse events were not significantly higher in the universal glove and gowning arm, which may seem surprising prima facie. However, the reason why adverse events are more common for patients on contact precautions is that they are marginalized by being on contact precautions. If all patients are effectively on contact precautions, the time of healthcare workers would be spread evenly.
  • Universal gloving is likely to result in universally bad hand hygiene compliance within the room during patient care; when healthcare workers feel protected, they are less likely to comply with hand hygiene and gloves are a good way to make healthcare workers feel protected. The increase in hand hygiene compliance on room exit is probably also a symptom of inherent human factors, since healthcare workers feel more ‘dirty’ when exiting the room of a patient with a higher perceived risk of MDRO ‘contamination’ (the so-called “urgh” factor).
  • Healthcare workers had less time for patient care in the intervention arm because they were busy donning and doffing gloves and gowns. Interestingly, the authors suggest that fewer visits may be a good thing for patients, and may have contributed to their reduced chances of acquiring MRSA. This seems unlikely though, given the fact that VRE acquisition was not reduced. On balance, less contact with healthcare workers is likely to be bad for patients.
  • The increased cost of universal glove and gowning was not evaluated and, whilst incrementally small, would be a substantial sum.

In summary, this study sets the standard in terms of rigorous assessment of an infection prevention and control intervention. Universal application of gloves and gowns is unlikely to do as much harm as universal administration of mupirocin, but it will not make a profound reduction in the transmission of MDROs. Therefore, I shouldn’t think many ICUs will be rushing to implement universal gloves and gowns on the strength of these findings.

Article citation: Harris AD, Pineles L, Belton B et al. Universal glove and gown use and acquisition of antibiotic-resistant bacteria in the ICU: a randomized trial. JAMA 2013;310:1571-1580.