Monday, September 21, 2015

Soft Cheese Listeria Outbreak Extends Back 5 Years - The Power of Whole Genome Sequencing

This past week, a California cheese company recalled cheese due to Listeria related illnesses.  CDC released information that there have been 24 cases in 9 different states caused by 5 closely related strains of Listeria.  The cases occurred over a five year period!  
The ability to combine this data into one outbreak is incredible!  Whole Genome Sequencing has become a game changer with regard to solving foodborne illness outbreaks.  The entire DNA sequence from pathogens responsible for past foodborne illness cases can be evaluated and matched with those from more recent cases. 
This technology also raises the ante for facilities with low level pathogen contamination issues.  Just as was seen with the Blue Bell ice cream facilities, it is more than a matter of checking the environment for Listeria, but enacting a proactive strategy that when contamination is found.  This includes an examination to determine if product has been exposed as well as a carrying out a seek-and-destroy mission to determine all potential sources/ contributing factors within the process environment (recognizing the fact that it is often an on-going battle of control rather than complete elimination).
This strategy also includes prevention of contamination - all of those things that come into process environment from outside - whether that is raw materials or even non-food (workers, inspectors, pallets, maintenance tools, carts, forklifts, used equipment, etc).  Who knows, some of this may be coming from a facility fighting its own endemic contamination issue.
Epi Curve, September 17, 2015
People infected with the outbreak strains of Listeria monocytogenes, by month of specimen collection*
CDC Outbreaks
Multistate Outbreak of Listeriosis Linked to Soft Cheeses
Posted September 18, 2015 9:00 AM ET
CDC is collaborating with public health officials in several states and the U.S. Food and Drug Administration (FDA) to investigate a multistate outbreak of Listeria monocytogenes infections (listeriosis). Listeria can cause a serious, life-threatening illness.
  • Five rare DNA fingerprints of Listeria are included in this investigation.
  • Whole genome sequencing showed that the Listeria strains with the five rare DNA fingerprints are closely related genetically.
  • Twenty-four people infected with one of the closely related Listeria strains have been reported from nine states since August 8, 2010.
  • Twenty-one people were hospitalized. Five illnesses were pregnancy-related; one resulted in a fetal loss. One death was reported from Ohio.
  • Additional illnesses are under investigation.
  • The investigation has not conclusively identified the source of this outbreak, but most ill people interviewed reported eating soft cheese before becoming ill. This investigation is ongoing.
  • Eighteen (82%) of the 22 ill people with available information reported eating soft cheeses in the month before becoming ill.
  • Four (57%) of seven ill people who specified a brand of cheese reported brands distributed by Karoun Dairies. No other brand of cheese was reported more than once.
On September 16, 2015, Karoun Dairies, Inc. voluntarily recalled[PDF - 2 pages] and ceased production of certain cheeses that the company distributes due to possible contamination with Listeria.

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