30 Sep

Listeria

Recently there has been a massive recall of cantaloupes due to contamination by bacteria that belong to the genus Listeria.  It is believed that these cantaloupes have all come from a farm in Colorado.  The genus Listeria is named after Dr. Joseph Lister,  the grandfather of what is known today as sterile surgery.  Bacteria in this genus is gram negative and the major human pathogen is Listeria monocytogenes.  This pathogen causes listeriosis, which is contracted by eating contaminated food.  Pregnant women, children, the elderly and anyone with a weakened immune system is more succeptible to the disease.  Listeria monocytogenes encodes genes that are temperature regulated.  The temperature within the host cell activates the translation of the virultent genes.  Other members of the genus Listeria use a very effective method to reporoduce within the host.  They use the protein actin within the host cell’s cytoplasm to create a comet-like structure.  This comet-like structure propels the bacterium to the cell membrane of the host and creates protrusions called filopods.   This protrusion makes contact with adjacent host cells and is phagocytosed.  Once the rocket is phagocytosed by a new cell the process repeats.  Listeriosis can be prevented by sanitizing surfaces that make contact with food.  These surfaces can be sanitized with alcohol.