Warning to all Microbiology students!

Persons infected with the outbreak strain of Salmonella Typhimurium, by state

A truly alarming report from the Centers for Disease Control, and widely reported in the popular press: a multistate outbreak due to Salmonella Typhimurium has been found to be attributable to a standard teaching laboratory isolate of the bacterium, resulting in infections in 109 individuals last spring with one death. Molecular analysis by the New Mexico Department of Health found that patient isolates were indistinguishable from commercially available isolates of Salmonella that are commonly used in college microbiology laboratories, suggesting that exposure in teaching labs was responsible for development of disease. Epidemiological analysis by the CDC found that patients were significantly more likely (60%) to have been in a microbiology laboratory a week prior to the onset of symptoms than control patients (2%) who did not get ill. Additionally, the CDC found that several children who became ill were associated with persons who worked or studied in labs that possessed the outbreak strain. Although the outbreak appears to have currently diminished to sporadic levels, the situation has led the CDC to reiterate good laboratory practices that can prevent future outbreaks. The astute BIO230 student will note that these practices are very similar to those outlined in the introductory lab safety lecture:

  • Organisms used in teaching laboratories have diminished virulence, but it should be stressed that the virulence is NOT zero, and some individual can be at increased risk than the general public. These organisms can also easily be unknowingly removed from the laboratory, and although you may not be in a risk group for developing disease, the people you may come into contact with MAY be at risk for disease.
  • Persons working with Salmonella and other microorganisms must receive basic instruction in infection control, in order to prevent potential transmission. Frequent handwashing is essential at stopping transmission, and additionally personal items such as keys, cell phones, music players should NEVER be handled at any time while in the microbiology lab. Food and drink should also never be brought into the same room.
  • Personal protection equipment (PPE) such as a lab coat should be used to cover clothing while in the microbiology lab, and should not leave the lab under any circumstances except to be sterilized by autoclaving.
  • When students work with isolates of Salmonella or other microorganisms, they should be aware of the signs and symptoms of disease. Salmonella infections are marked by diarrhea, fever, and abdominal cramps within 12 to 72 hours post exposure. You should contact your personal care physician if you or someone with whom you have contact show these signs following working with bacteria in the lab.

The Center for Disease Control noted that biosafety lab practices were largely similar between labs where disease was found and labs that didn’t report cases, however they found that “some policies appeared to be more difficult to monitor and enforce, such as not allowing the use of handheld devices (e.g., cell phones or music players) at the laboratory work space.” Our most effective strategy in this case would likely seem to be vigilance and respect, knowing that the organisms are present and using the utmost care to prevent them from leaving the lab.


About ycpmicro

My name is David Singleton, and I am an Associate Professor of Microbiology at York College of Pennsylvania. My main course is BIO230, a course taken by allied-health students at YCP. Views on this site are my own.

Posted on January 20, 2012, in Danger danger danger!, Lab, Microbes in the News and tagged , , , . Bookmark the permalink. Comments Off on Warning to all Microbiology students!.

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