Sunday, March 20, 2016

Elizabethkingia: The Bacteria That Kicks You While You're Down

What's your biggest fear? Sharks? Heights? Cancer?

Compared to exciting threats like sharks, or falling to your death when your bungee cord snaps on your honeymoon bungee jumping excursion, infectious diseases fall pretty low on the list for most Americans. We've eradicated a number of diseases through rapid urbanization/industrialization (did you know that malaria was endemic in North America in the early decades of the union?), large-scale waste management (bye, cholera!), and widespread use of vaccinations (see: smallpox, polio, etc.).

An agar plate of bacteria and mold, from NationWell

There's a number of things to which Americans are not immune, and a large category of them is bacterial infections. I say "category", because the variety of pathogenic bacteria in the U.S. can be broken into a number of subdivisions, such as: sexually transmitted infections (those which are caused by bacteria), antibiotic/antimicrobial resistant bacteria, those spread by environmental exposure (like Borrelia spp. that causes Lyme Disease, which is transmitted by ticks), and nosocomial bacterial infections (also known as hospital-acquired infections), just to name a few.

The most well-known subdivision I mentioned above is antibiotic/antimicrobial resistant bacteria. In fact, over two million people in the U.S. are infected with antibiotic/antimicrobial resistant bacteria each year. You can dig deeper into the world of antibiotic/antimicrobial resistant bacteria on the CDC website, which rates bacterial species based on the severity of the threat they pose

Nosocomial infections, specifically, caused approximately 1.7 million infections and resulted in  99,000 deaths in 2002 (according to an estimate report from the National Nosocomial Infections Surveillance System). A similar surveillance survey by the CDC in 2011 reported over 720,000 nosocomial infections in acute care hospital facilities.

Get more information on the CDC's Hospital-Acquired Infection Data and Surveillance Report here.

I bring this up because in the span of 4 months, a bacterial infection called Elizabethkingia anophelis has killed 18 people in Wisconsin and 1 person in Michigan.

Elizabethkingia is the phylogenetic genus of 4 related species of gram negative bacteria:
  • E. anophelis, which causes respiratory infections in humans, and was originally isolated from the midgut of Anopheles mosquitoes
  • E. endophytica, which is a plant pathogen that mostly infects Zea Mays, or sweet corn
  • E. meningoseptica, which causes severe meningitis and sepsis in newborns and infants (premature newborns are particularly susceptible)
  • E. miricola, which was miraculously (pun!) isolated from condensation water on the Russian Space Station, Mir.
The genus is named after Elizabeth Osborne King, a clinical microbiologist (and a #WomanInSTEM!) who worked for the CDC in the 1940s through the 1960s, and studied meningitis in newborns. E. anophelis is common in environmental reservoirs, such as water and soil, but rarely causes infections in humans. The CDC logs only a handful of reported cases in the US each year.  

Yet, in Wisconsin, approximately 54 people have been infected since November of 2015. The outbreak is mostly affecting people who are 65 years or older, most of which had underlying health conditions. E. anophelis infects the bloodstream and occasionally the respiratory tract, causing nonspecific symptoms, including fever, chills, shortness of breath, and cellulitis. Death is usually a result of sepsis.

The current outbreak has been tracked across 12 counties, but has not specifically been labeled as a hospital-acquired infection. Infections of the current outbreak have been centered in the southeastern quarter of the state, including the Milwaukee area and surrounding suburban counties. One case in Hong Kong illustrated that the infection can be spread from mother to child. E. anophelis is an antibiotic resistant species, which is why the magnitude of the current outbreak is causing such alarm for medical professionals. Transmission from person-to-person is highly unlikely without blood-to-blood contact, meaning there must be another common source within the community. The transmission route for the most recent outbreaks that occurred prior to the current one in Wisconsin, one in Central Africa and the other in Singapore, was not determined.

So, how does this factor into our biggest fears? The infectious disease world is constantly discussing the concept of "emerging diseases", meaning rare infections that are suddenly migrating to naive populations (meaning, the population of that geographical region has never been exposed to the pathogen before) or are infecting new populations. Antibiotic resistant bacteria, like Elizabethkingia anophelis, are sometimes included in the description of emerging diseases because the acquired or developed resistance poses new problems for treatment and infection control.

Say you go to the hospital because your appendix has ruptured. This is a routine surgery that shouldn't take much time or effort. But being in the hospital puts you at risk for infection, especially when you are in the process of recovering from a routine, but intensive, procedure. If the infection is rare, it will take your doctor a longer time to identify the culprit. If the infection is resistant to common treatments, you will have to endure more extensive treatment programs. If you are recovering from a surgical procedure, or have other open and exposed wounds, you're immune system may be otherwise preoccupied. So, a short hospital stay that should have been routine, might end up being more extensive, or putting you at a higher risk for death.

If you would like to follow the outbreak in Wisconsin, the Department of Health Services website is updated every Wednesday regarding developments in the investigation.

1 comment:

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