Mucor, Negative-Pressure Rooms, and the Immunosuppressed

Today the Centers for Disease Control released the long-awaited report on the Mucor mold infections that occurred in the ICU at my home institution. The findings did not contain any major findings that were not well known prior to the report. However, the report is important, nonetheless, as it highlights the ubiquity of mold in the environment and illustrates how immunosuppressed patients are exquisitely--and almost exclusively--at risk.

To recap, there were 3 probable and 1 suspect infection that occurred with mold of the Mucor variety in transplant patients. Of the 4 cases, three were fatal and three occurred in the same ICU room. This type of mold is important given its high mortality rate which is a largely a result of the type of patients it infects (i.e. the immunosuppressed). 

The most important part of the CDC report is the case-control study they conducted. Case control studies are very important at delineating risks and eliminating noise in the quest for a definitive answer to the phenomenon under study.

In this case-control study, the room that 3 of the 4 patients stayed in was found to be the only significant factor that distinguished cases from the controls studied. This result puts to rest any other factor that may have been at play such as contaminated linens, for example.

What was special about this room, according to the CDC report,  was that it was a negative-pressure room which, by design, draws air in (these are the room we use for contagious tuberculosis patients to prevent infectious air from leaking out of the room). Could the negative-pressure have drawn fungal spores in? The room was also located near the exit of the ICU providing a route for spores from visitors's clothes, shoes, and elsewhere outside the to gain some proximity to the negative-pressure room.

It is important to remember that these mold infections, unfortunate and tragic, likely do not represent a major statistical aberration over what would be expected at a major transplant center that cares for some of the sickest patients in the world. FYI, my mother just had surgery at the hospital and I didn't bat an eye over her risk for infection with Mucor.

The report's recommendations to not use negative-pressure rooms for immunosuppressed patients (unless needed), to change some of the geography, and maintain vigilance for future occurrences are valid. 

Infectious Disease: The Coolest Specialty in the World

As I always preach, infectious diseases can be an exhilarating field full of all kinds of challenges that may be lurking in each patient on whom you're consulted. Mixed amongst the mundane cases of infected pressure ulcers, cellulitis, and urinary tract infections is where you find the zebras--if you look hard enough or, in Pasteur's immortal words, have a prepared mind.

The latest zebra spotting occurred this week. The patient was an injection drug user who presented with an alteration in consciousness and ultimately was diagnosed with an encephalitis of unknown cause. Encephalitis has a variety of causes, many of which are infectious. Herpes and West Nile Virus are two common causes in the US, but many other viral causes go unidentified because of lack of easy diagnostics. Not all encephalitis, however, is infectious in origin and there are autoimmune forms as well. Treatment is different for infectious vs. autoimmune encephalitis with immunosuppression being the mainstay of management of autoimmune forms.

This patient's diagnostic workup was completely unrevealing--no virus was found and suspicion turned to an autoimmune form of encephalitis. Brain biopsy results were forthcoming when the patient's clinical course took a terminal course and the patient unfortunately died. 

Now here come's the twist.

Since this was a young patient there was a major impetus for organ donation. However, it is a very dangerous proposition to transplant organs from a person who has died of an unknown encephalitis as both rabies and West Nile have been transmitted that way. His organs were deemed not suitable for donation.

Another twist then occurred when the brain biopsy results returned.

Mucormycosis.

Many people outside of infectious disease may never have heard of Mucormycosis but it is an aggressive fungal infection that leaves most of its victims dead. It is often seen in the immunosuppressed or diabetics and occasionally has been seen in injection drug users (I saw a fatal case previously with horrible skin lesions) and was interestingly seen in Joplin tornado victims.

To transplant organs from someone who died of an invasive fungal infection, which Mucormycosis is par excellence, would be a death sentence for organ recipients. What likely occurred in this case is that heroin contaminated with fungal spores from the environment were injected and the process begun. 

So hoofbeats can belong to zebras sometimes.