And what about antimicrobial scrubs?

Ascot: a neckband with wide pointed wings, traditionally made of pale grey patterned silk

The role that environmental transmission plays in the spread of important pathogens is increasingly recognized. One of the major mechanisms by which pathogens are thought to spread is via contaminated healthcare worker clothing. A major reason that gowns are included in contact precaution is that they are felt to interrupt the transmission from patient/environment to HCW attire. An old (2010) study that Dan Morgan completed found that gowns became contaminated 11% of the time when caring for patients with MDR-Acinetobacter and 5% of the time when caring for patients with MDR-Pseudomonas. A repeat (2012) study found that gowns became contaminated during 4% of HCW visits caring of MRSA+ patients, 5% for VRE, 2% for MDR-Pseudomonas and 13% for MDR-Aceintobacter.

With so much contamination and a desire to rid the world of unnecessary gown use, investigators have been exploring the benefits of antimicrobial textiles, such as scrubs. If these novel scrubs could reduce contamination, maybe we could drop the dreaded gown and go with universal gloves for contact precautions?

Which brings us to a ASCOT study by Deverick Anderson and colleagues funded by the CDC Prevention Epicenters Program. ASCOT: Antimicrobial Scrub Contamination and Transmission. The investigators examined the benefits of two different antimicrobial scrubs (Scrub 1: silver-alloy and Scrub 2: organosilane-based quaternary ammonium and a hydrophobic fluoroacrylate copolymer emulsion) vs standard poly-cotton surgical scrubs in a 3-arm RCT during 3-consecutive 12-hour ICU nursing shifts. The primary outcome was change in total contamination on the nurses scrubs as sum of CFUs. Of note, all MDRO colonized patients in the study were placed on contact precautions and HCW placed gowns over their scrubs and wore gloves while caring for those patients.

The study collected many cultures: 2919 from the environment and 2185 from the HCW clothing. 41 nurses were randomized but one was excluded for a total of 40 nurses caring for 102 patients during 167 encounters. Their primary finding was the scrub type had no effect on HCW clothing contamination (p=0.70) There is a lot to unpack in this study and it warrants a careful read - a lot of data! but I've included Table 3 below with the contamination before/after each shift. Overall, the median CFU increase was 61.5 (interquartile range [IQR], −3.0 to 191.0) in the control arm, 73.0 (IQR, −107.0 to 194.0) in the Scrub 1 arm, and 54.5 (IQR, −60.0 to 215.0) in the Scrub 2 arm.

There were acquisition events during 39 (33%) of the shifts with 20 (17%) environmental acquisitions and 19 (16%) acquisitions on HCW attire. Looking at the 19 HCW attire acquisition events, 12 (63%) were confirmed: 7 from the patient, 3 from environmental contamination, and 2 from the patient/environment.

Overall, the authors reported that there were no benefits from either antimicrobial scrub. However, there was significant transmission from patient or environment to HCW attire.  Back to the drawing board on antimicrobial scrubs?  Maybe. I would like to see the study repeated in a hospital where contact precautions are not used to see if benefits might exist in settings where gowns are not worn when caring for MDRO+ patients. With this much acquisition of nurses' clothing, it's going to be hard to ditch gowns, unfortunately.

Oh, and I love the ASCOT name. Brilliant.

The cartoon editorial, microbiology edition: An idea whose time has come!

I was excited to read the editorial in this month’s Journal of Clinical Microbiology (JCM), by Alex McAdam (JCM Editor in Chief), entitled “Prevalence and Predictive Values”. You can read it here too, because I’ve pasted it below:

Brilliant—a simple concept (diagnostics 101!) explained in a simple format. And as an associate editor of JCM, I can attest that this concept is frequently missed by submitting authors, not to mention practicing clinicians and hospital epidemiologists. 

This issue is also foundational to diagnostic stewardship, as it emphasizes the importance of limiting diagnostic testing to patients who have a reasonable pre-test likelihood of disease (pre-test likelihood being the individual-patient equivalent of population prevalence). 

It also explains why we’ll never “get to zero” for healthcare-associated infections (HAIs), even if all HAIs were preventable. Take the example of hospital-onset C. difficile infection (HO-CDI). The more successful your prevention program is at reducing whatever the “true” incidence of HO-CDI is, the lower will be the population prevalence—and the lower the positive predictive value (PPV) for the very sensitive CDI tests we now use. Positive tests will still occur, no doubt, and will be counted toward the HO-CDI rate—but they’ll be increasingly likely to be clinical false positives. 

Now I need to go start working on a good cartoon editorial about whether CAUTI exists….

Summer Quick Hits (with the Award for the Most Eyebrow-Raising Article Title of the Year)

Trying to recover from summer vacation (Alaska = thumbs up, especially during a summer heat wave) and gear up for a new school (and blogging) year, so here are a few quick hits from recent articles:

Two articles highlight several HAIs that aren't often included in surveillance and prevention efforts:

• Len Mermel has a nice systematic review in CID examining the burden of bloodstream infection related to short-term peripheral venous catheters (a.k.a. peripheral IVs - not midline or PICCs).  Used in a substantial number of hospitalized patients (esp. as we're better about central line necessity), these devices have a much lower risk of BSI when compared to central venous catheters (2-64 fold higher risk for CVCs); however, given the vast number of devices used (Len estimates ~200 million adult patients in the U.S. annually), the number of BSI events are likely high. A number of interesting details are in the paper, so worth checking out. 
• A nice commentary out of the UK in Lancet Respiratory Medicine advocates for an increased focus on healthcare-associated pneumonia, particularly that which occurs outside of the ICU (and is not ventilator-associated). 

Both of these papers highlight HAIs that are not in the "Big 5" (CLABSI, CAUTI, SSI, MDROs/C. diff, and VAE) but cause patient harm.  Broadening an IP surveillance and prevention program to include these events does have some challenges, however.  The worry about objective surveillance definitions that came to a head with VAP certainly applies to HAP, and the volume of patients at risk for a PIV-related BSI invites the need for an automated system for surveillance.  Nonetheless, with reductions in the Big 5 (well, except VAE as I'm still not sure how to tackle that one), it's perhaps time we look to expand our scope.

Finally, a paper that wins the award for the most eyebrow-raising title of the year: "Hematophagous Ectoparasites of Cliff Swallows Invade a Hospital and Feed on Humans."  Try reading that without saying "What?? Gross."  The authors outline their nosocomial "outbreak" of two ectoparasites related to a massive swallow roost on the outside of a community hospital.  One inpatient noted a rash illness, and testing of ticks and bugs identified the presence of human blood in 17% of the captured critters.  Hospital invasion!  Feeding on humans! Talk about a riveting agenda for your next infection prevention committee meeting!

Diagnostic Stewardship

The following is a guest post from Dr. Dan Morgan, GFOTB (Good Friend Of The Blog):

This week Preeti Malani, Dan Diekema and I wrote a viewpoint in JAMA discussing diagnostic stewardship, or “modifying the process of ordering, performing, and reporting diagnostic tests to improve the treatment of infections and other conditions.” In other words, guiding laboratory ordering to prevent contradictory results and reporting results in a fashion that makes treatment more appropriate. There really are two Criteria for Diagnostic Stewardship modifying laboratory testing:

1) Does it modify the process of ordering, performing and reporting tests? 

2) Does it improve the appropriateness of patient management? 

When I discussed diagnostic stewardship with my non-medical wife, she asked “you mean they don’t do that? Why would they do tests that contradict other results or provide second or third line antibiotic choices?” 

This is why I think diagnostic stewardship has so much potential. It is about making laboratory ordering more rational, which is hard to debate. Although medicine has existed with the idea that doctors knew best how to order and interpret results, we are now seeing they often don’t, as predicted by psychologists Danny Kahneman and Amos Tversky in the 1970s; “Intuitive judgments are liable to similar fallacies in more intricate and less transparent problems.” 

Doctors ordering and interpreting test results are like other people, often irrational. Diagnostic stewardship makes testing more logical to improve patient care. Ultimately this process shouldn’t be limited to urine cultures, blood cultures and C. difficile testing but applied to new molecular detection panels and non-ID tests, like cascading tests for anemia or limiting PSA testing in young and elderly men. And there has been interest in this idea from areas outside of ID. 

The fact that diagnostic stewardship reduces false-positive tests that contribute to publicly reported HAIs means there is likely a lot of incentive to support these processes. But we shouldn’t forget there are important patient benefits too, including avoiding unnecessary antibiotics, avoiding the distraction of misdiagnosis, and improving the ability of HAI rates to truly measure care.