On May 30, 2012 Brianna Dannen, Public Health Nurse at the Clark County Health District (CCHD), received a call from Bob Williamson at Clark College.  Mr. Williamson called to report that a child of a Clark College student enrolled in a microbiology class, BIOL&260, taught by Travis Kibota was ill with Salmonella.  The student, Cameron Ross, had recently conducted tests on an “unknown organism” as part of a class assignment to identify the organism.  The organism Ms. Ross had been assigned to identify was pathogenic Salmonella Typhimurium.  Mr. Williamson and Mr. Kibota thought there might be a connection between Ms. Ross’s work in the laboratory and the Salmonella infection diagnosed in her son, Braden Linkenheimer.

Their concern was not without precedent.  In October 2010 PulseNet detected a multistate outbreak of Salmonella Typhimurium infections with PFGE Pattern JPXX01.0014. The source of the outbreak remained unsolved until December 2010 when the New Mexico Department of Health identified three patients with strain JPXX01.0014.  One patient was a student and the two other patients were children of students in microbiology courses held at two community college campuses. This finding prompted an epidemiologic study of patients infected with Salmonella Typhimurium Strain JPXX01.0014.  In total 109 patients residing in 38 states were identified as being infected with Strain JPXX01.0014.  Ill persons were significantly more likely than non-ill persons to report exposure to a microbiology laboratory in the week before illness onset.  NM DOH investigators connected the strain of Salmonella Typhimurium isolated in patients with a commercially available Salmonella Typhimurium strain used in laboratory settings.[1]

It would not be long before CCHD learned that Braden Linkenheimer, Cameron’s son, was also infected with Salmonella Typhimurium. The Oregon Health Division (OHD) Public Health Laboratory (PHL) conducted PFGE on the isolate cultured from Braden’s stool specimen (OHD PHL ID#12053002562). Results showed that Braden was infected with PulseNet Pattern JPXX01.0014, the same strain identified in the previous outbreak associated with exposure to microbiology laboratories. Instructor Travis Kibota confirmed that the strain used by his students in his microbiology laboratory was Salmonella Typhimurium ATCC strain 14028.  Thus, the connection between Braden Linkenheimer’s salmonellosis and his mother’s exposure to Salmonella in the microbiology laboratory was definite.

Public health investigators explored ways Braden Linkenheimer was exposed to the laboratory strain of Salmonella Typhimurium.  Based on the usual incubation period for a Salmonella infection (6-72 hours), two routes of transmission seemed possible.  Cameron Ross first had contact with her “unknown organism” in the laboratory on Monday, May 14. She continued her laboratory experiment on May 16, May 21 and May 30.  Ms. Ross reported having several episodes of diarrhea starting May 18.  Braden became ill on May 24.  Based on her report of diarrheal symptoms on May 18, it is possible that Ms. Ross was infected on May 14 or May 16 during her laboratory work and that Braden became ill secondarily through person-to-person spread with his mother while she was ill.  However, a stool specimen collected from Ms. Ross on June 1 was negative for Salmonella.

Investigators also posited that Braden became ill as a result of contact with classroom materials that Ms. Ross used in the laboratory and subsequently brought home with her, i.e., fomite transmission.  Investigators reviewed Ms. Ross’ laboratory practices.  She stated that she followed protocols provided to students at the start of the term.  Students were allowed to bring personal items such as pens, pencils and laptops into the lab with them.  The instructions provided to students by Mr. Kibota did not clearly state that personal items should not be in allowed in the lab.  In fact, Mr. Kibota told health department investigators that “we do not have official policies regarding fomites such as pencils, pens, cell phones, etc.”  Students were advised to wear “old clothes” and lab coats were described as “optional.”  Students were tested on their knowledge of lab procedures and safety rules.  Cameron Ross received 100% on her test.

Ultimately, investigators were not able to determine if Braden acquired his infection via person-to-person transmission from his mother or through contact with a contaminated item she brought home with her.  What was clear is that Braden was infected with the strain of Salmonella Typhimurium used in his mother’s microbiology class just before he became ill.

CCHD staff referred Mr. Kibota to guidelines recommended by the CDC following the 2010-2011 outbreak of laboratory acquired Salmonella Typhimurium.[2]  Mr. Kibota was advised to add a component about signs and symptoms of bacterial infection to safety instructions provided to students and to require use of lab coats by students.  Dr. Alan Melnick, CCHD Health Officer, went so far as to question why “students (or faculty) in a community college lab should be working with human pathogens….”

Among the CDC recommendations for laboratory directors, managers, and faculty involved with clinical and teaching microbiology laboratories, were the obvious:

  • Non-pathogenic (attenuated) bacteria strains should be used when possible, especially in teaching laboratories.  This will help reduce the risk of student and/or their family members becoming ill (emphasis added).
  • Place dedicated writing utensils, paper, and other supplies at each laboratory station.  These items should not be allowed to leave the laboratory.

These recommendations were made over a year before Braden’s Salmonella infection.[3]

Dr. Sandra McLellan, Associate Professor and Senior Scientist, Great Lakes WATER Institute at the University of Wisconsin-Milwaukee, reviewed laboratory protocols provided to students in Travis Kibota’s microbiology class.  Dr. McLellan noted several factors that contributed to the Salmonella infection experienced by Braden Linkenheimer.

  • Lack of sufficient instructions in the safety procedures for the lab for working with pathogens.
  • Information about signs and symptoms of infection by the pathogens being studied and utilized at the laboratory would have resulted in students taking proper precautions against both infection and secondary transmission of disease.
  • As recommended by the Centers for Disease Control and Prevention, the lab should have been using a non-virulent strain of Salmonella in the classroom setting.
  • Personal items should not have been allowed in the laboratory.

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[1]           See Final Update: Human Salmonella Typhimurium Infections Associated with Exposure to Clinical and Teaching Laboratories, CDC, January 17, 2012, http://www.cdc.gov/Salmonella/typhimurium-laboratory/011712/index.html.

[2]           Id.

[3]           Investigation Announcement: Multistate Outbreak of Human Salmonella Typhimurium Infections Associated with Exposure to Clinical and Teaching Microbiology Laboratories. CDC April 28, 2011. Online: http://www.cdc.gov/salmonella/typhimurium-laboratory/042711/index.html#advice-directors.