Drug resistant bacteria versus advanced medical technology: No contest

The duodenoscope implicated now in several deadly outbreaks of carbapenem-resistant Enterobacteriaceae (CRE) is an otherwise terrific device for management of biliary or pancreatic duct disorders. Unfortunately, the same features that allow the scope to guide fine instruments into miniscule spaces also provide sanctuary for bacterial pathogens, protecting them from all standard approaches to disinfection. To quote yesterday’s FDA safety communication: 

“…reports associate multidrug-resistant bacterial infections in patients who have undergone ERCP with reprocessed duodenoscopes, even when manufacturer reprocessing instructions are followed correctly. Meticulously cleaning duodenoscopes prior to high-level disinfection should reduce the risk of transmitting infection, but may not entirely eliminate it.”

Translation: you pays your money and you takes your chances. 

There aren’t any great options for further reducing the (albeit small) risk for infection transmission from these devices. Some hospitals that have experienced outbreaks have switched to ethylene oxide gas, which is time-consuming and may still fail if organic debris remains in the tiny spaces that are so difficult to clean mechanically. Microbiological surveillance (culturing scopes after disinfection) is time-consuming, costly, and has unknown sensitivity for detection of transmission risk. 

This problem is just one example of the limitations that antimicrobial resistance and infection control practice place on advanced healthcare delivery. Each year we see advances in our ability to provide life-saving care—but each of these advances can be easily circumvented by a simple lapse in infection control practice, or an untreatable bacterial pathogen. 

As for this particular device, there must be a safer approach that doesn’t sacrifice utility. In a world where you can buy a robot hat-backpack that feeds you tomatoes while you jog, there must be a way to design a duodenoscope that can be effectively cleaned.

Rosie reincarnated

As a child I never liked cartoons much, with one exception--The Jetsons. The Jetsons were a family that lived in Orbit City in 2062. The parents were George and Jane, and the kids were Judy and Elroy. But there was also the family dog, Astro, and their cleaning lady, Rosie the Robot.

I couldn't help but think of Rosie as I read an article on the use of disinfecting robots at Johns Hopkins Hospital in today's Baltimore Sun. These robots seem to be all the rage. If you want to dig a little deeper, Clinical Infectious Diseases has the full account of the study done by Trish Perl's group. In the study, rooms that had previous occupants with MDROs were subjected to standard cleaning in 3 hospital units. In 3 other units, rooms were disinfected by hydrogen peroxide vapor producing robots. Subsequent room occupants were assessed for MDROs to determine whether transmission to the new occupant had occurred. The investigators demonstrated a significant reduction for VRE in subsequent occupants, but no significant decrease for MRSA, C. difficile, or MDR-gram negative rods. Of note, the study was partially funded via in-kind services by the robot maker. An excellent editorial by Cliff McDonald and Matt Arduino accompanies the paper.

The bottom line is that the authors demonstrated an absolute 6% reduction in VRE acquisition with use of robotic disinfection. Does that result warrant jumping on the robot band wagon? I don't think so for several reasons. First, with the exception of a few special patient populations (e.g., oncology and transplant patients), VRE has little pathogenic potential. Second, only a fraction of newly colonized VRE patients will develop infection. Third, a big problem with the study is that molecular typing was not performed. A few years ago, one of my IPs noted that 4 consecutive patients housed in the same room in our medical ICU all developed VRE bloodstream infections. I was certain that we had a problem with suboptimal cleaning between patients. Fortunately, we had all the isolates, and when molecular testing was performed we surprisingly found that the isolates were all genetically very distinct. It seems that VRE is an organism that while transmissible is also one for which antibiotic pressure is always creating new strains in individual patients. Lastly, even if this technology were perfect and rendered a room absolutely sterile, within seconds of the robot leaving and the humans returning, the room will once again be contaminated. It reminds me of the hysterical response by grade schools several years ago of shutting down a school and bleaching it after a child was found to have MRSA.

So to any hospital thinking about hiring Rosie, ponder long and hard, and consider taking all that money and using it to drive hand hygiene compliance to a new level. Remember, in health care, the hands remain the final common pathway.

Happy New Year!

Beware of dishes!

As of this week, germophobes have one more thing to worry about. A new paper in PLoS One (full text here) describes the results of a series of experiments in which dishes and forks were contaminated with a mouse norovirus and then subjected to the usual cleaning protocols used in restaurants (both machine and hand washing of the items). The results were disturbing. The various cleaning methods all left residual norovirus on the dinnerware. This is especially important since the infecting dose of norovirus may be as low as 10 viral particles.

So what to do with this information? Here are your options (from most to least risk averse):
(1)  Never eat in a restaurant again
(2)  Carry your own dinnerware with you wherever you go
(3)  Eat only at McDonald's where all dinnerware is disposable (though you could still be at a small risk from the reusable plastic tray your food items are placed on)
(4)  Eat at all your favorite places and stockpile compazine and immodium
(5)  Just cast your fate to the wind

The ghosts of the "prior room occupant"

"Well, you know, Doc, when something happens, [it] can leave a trace of itself behind. Say like, if someone burns toast. Well, maybe things that happen leave other kinds of traces behind. Not things that anyone can notice, but things that people who "shine" can see….I think a lot of things happened right here in this particular hotel over the years. And not all of 'em was good."

-From the movie The Shining, 1980 

I’m reviewing papers for a talk I’m preparing on “control of multiple drug resistant gram negative rods (MDR-GNRs)”. So I’m looking again at a set of studies that always scare me (even more than a Stephen King novel)—those that demonstrate that a variety of bad bugs (C. difficile, MRSA, VRE, and MDR-GNRs) can be “left behind” after a patient is discharged, poised to colonize or infect the next occupant of that hospital room. It is a scandalous indictment of current hospital disinfection practices that patients must be haunted by the pathogens of the previous occupant of their hospital bed! 

There are still some practical (and financial) hurdles that must be overcome before new disinfection technologies (UV light, H2O2 vapor, antimicrobial surfaces, etc.) become standard of care. In the long run, though, I think that’s where the future lies—excellence in cleaning will remain important (organic debris will always require removal), but for microbial eradication in the environment, these technologies are going to replace our existing, more rudimentary approaches.

Infectious Risks of Transvaginal Ultrasound

Transvaginal ultrasounds carry infection risks, although published estimates of rates are lacking. With the Commonwealth of Virginia poised to mandate ultrasounds prior to an abortion, and other states certainly to follow, it is important to review the CDC guidelines for the cleaning and disinfection of vaginal probes. There are also other issues at stake, like the doctor-patient relationship. Mandatory reporting of all infections secondary to this procedure should be considered.

UPDATE: Image removed.

From the CDC-HICPAC "Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008"

Vaginal probes are used in sonographic scanning. A vaginal probe and all endocavitary probes without a probe cover are semicritical devices because they have direct contact with mucous membranes (e.g., vagina, rectum, pharynx). While use of the probe cover could be considered as changing the category, this guideline proposes use of a new condom/probe cover for the probe for each patient, and because condoms/probe covers can fail (195, 197-199), the probe also should be high-level disinfected. The relevance of this recommendation is reinforced with the findings that sterile transvaginal ultrasound probe covers have a very high rate of perforations even before use (0%, 25%, and 65% perforations from three suppliers). (199)

One study found, after oocyte retrieval use, a very high rate of perforations in used endovaginal probe covers from two suppliers (75% and 81%) (199), other studies demonstrated a lower rate of perforations after use of condoms (2.0% and 0.9%) (197 200). Condoms have been found superior to commercially available probe covers for covering the ultrasound probe (1.7% for condoms versus 8.3% leakage for probe covers) (201). These studies underscore the need for routine probe disinfection between examinations. Although most ultrasound manufacturers recommend use of 2% glutaraldehyde for high-level disinfection of contaminated transvaginal transducers, the this agent has been questioned (202) because it might shorten the life of the transducer and might have toxic effects on the gametes and embryos (203).

An alternative procedure for disinfecting the vaginal transducer involves the mechanical removal of the gel from the transducer, cleaning the transducer in soap and water, wiping the transducer with 70% alcohol or soaking it for 2 minutes in 500 ppm chlorine, and rinsing with tap water and air drying (204). The effectiveness of this and other methods (200) has not been validated in either rigorous laboratory experiments or in clinical use. High-level disinfection with a product (e.g., hydrogen peroxide) that is not toxic to staff, patients, probes, and retrieved cells should be used until the effectiveness of alternative procedures against microbes of importance at the cavitary site is demonstrated by well-designed experimental scientific studies. Other probes such as rectal, cryosurgical, and transesophageal probes or devices also should be high-level disinfected between patients.

As with other high-level disinfection procedures, proper cleaning of probes is necessary to ensure the success of the subsequent disinfection (205). One study demonstrated that vegetative bacteria inoculated on vaginal ultrasound probes decreased when the probes were cleaned with a towel (206). No information is available about either the level of contamination of such probes by potential viral pathogens such as HBV and HPV or their removal by cleaning (such as with a towel). Because these pathogens might be present in vaginal and rectal secretions and contaminate probes during use, high-level disinfection of the probes after such use is recommended.

References:

195. Fritz S, Hust MH, Ochs C, Gratwohl I, Staiger M, Braun B. Use of a latex cover sheath for transesophageal echocardiography (TEE) instead of regular disinfection of the echoscope? Clin. Cardiol. 1993;16:737-40.

196. Lawrentschuk N, Chamberlain M. Sterile disposable sheath sytsem for flexible cytoscopes. Urology 2005;66:1310-3.
197. Milki AA, Fisch JD. Vaginal ultrasound probe cover leakage: implications for patient care. Fertil. Steril. 1998;69:409-11.
198. Storment JM, Monga M, Blanco JD. Ineffectiveness of latex condoms in preventing contamination of the transvaginal ultrasound transducer head. South. Med. J. 1997;90:206-8.
199. Hignett M, Claman P. High rates of perforation are found in endovaginal ultrasound probe covers before and after oocyte retrieval for in vitro fertilization-embryo transfer. J. Assist. Reprod. Genet. 1995;12:606-9.
200. Amis S, Ruddy M, Kibbler CC, Economides DL, MacLean AB. Assessment of condoms as probe covers for transvaginal sonography. J. Clin. Ultrasound 2000;28:295-8.
201. Rooks VJ, Yancey MK, Elg SA, Brueske L. Comparison of probe sheaths for endovaginal sonography. Obstet. Gynecol. 1996;87:27-9.
202. Odwin CS, Fleischer AC, Kepple DM, Chiang DT. Probe covers and disinfectants for transvaginal transducers. J. Diagnostic Med. Sonography 1990;6:130-5.
203. Benson WG. Exposure to glutaraldehyde. J. Soc. Occup. Med. 1984;34:63-4.
204. Garland SM, de Crespigny L. Prevention of infection in obstetrical and gynaecological ultrasound practice. Aust. N. Z. J. Obstet Gynaecol. 1996;36:392-5.
205. Fowler C, McCracken D. US probes: risk of cross infection and ways to reduce it--comparison of cleaning methods. Radiology 1999;213:299-300.
206. Muradali D, Gold WL, Phillips A, Wilson S. Can ultrasound probes and coupling gel be a source of nosocomial infection in patients undergoing sonography? An in vivo and in vitro study. AJR. Am. J. Roentgenol. 1995;164:1521-4.

In case you mist it.....

Two articles and an editorial in the June issue of ICHE discuss the use of hydrogen peroxide (vapor or mist) in hospital room disinfection. The hydrogen peroxide systems are appealing—the by-products, water and oxygen, are harmless, while H2O2 itself is sporicidal (i.e. kills C. difficile) and effective in eradicating other nosocomial pathogens from environmental surfaces.

The main drawback, besides the added cost, is feasibility. There are two systems (vapor and “dry mist”), and the vapor apparently requires that the room be sealed (doors, windows, ventilation ducts, etc.) during application. The Rhode Island group reports that H2O2 vapor decontamination required a mean of 2 hours and 20 minutes—not an appealing prospect for hospitals that run at or near capacity and for which short room turnaround times are critical.