escherichia coli 0157 h7

Escherichia Coli 0157:H7

Angelique and Ethan

                E. Coli 0157:H7

• large and diverse group of bacteria • most strains are harmless but others cause disease by

making a toxin called Shiga toxino "Shiga toxin-producing" E. coli - STEC

• when you hear news reports about E.coli infections they're usually about 0157:H7

                    Epidemiology

• first recognized by the Centers for Disease Control as a pathogen in 1982

• during an outbreak of Hemolytic-uremic Syndrome in Oregon and Michigan

• associated with eating hamburgers at the restaurants of one national chain

• reported to cause large outbreaks as well as isolated sporadic infections in small numbers

                     Shiga Toxin

• released into the intestinal tract• inhibits protein synthesis in target cells

o  cuts off several neucleobases from RNA compromising the ribosomes

• structure has two unitso B subunit binds to specific glyco-lipids on the host cello A subunit is internalised and divided

A1 binds to ribosomes• toxin requires specific receptors on the cell surface

o  cattle, swine, and deer do not have these receptors harbor the bacteria and excrete it in their feces 

• damages red blood cells as they pass through the intestinal tract

                STEC E. Coli

• STEC strains can survive for long periods of time on little sustenanceo several weeks on a countertopo up to a year in materials such as compost

• takes a very small amount of bacteria to infect a human o as few as 10 cells can be infected and still cause the

symptoms • toxin classified as a potential                                      

biochemical terrorist agent                                                      by the CDC 

                 How's It Spread ?

• ingesting tiny amounts of human or animal feceso consumption of contaminated foodo unpasteurized (raw) milko water that has not been disinfected

• contact with cattle• contact with the feces of infected people

              Signs and Symptoms    

• bloody diarrhea• severe abdominal pain and tenderness without fever• colitis - swelling of the large intestines• an acute infection 

o recovery in 5-10 days without any specific treatment• more serious in children under 5 yrs old and the elderly

o Hemolytic-uremic Syndrome (HUS)o Thrombotic Thrombocytopenic Purpura (TTP)

    Hemolytic-uremic Syndrome                    • caused in young children • most worrisome complication - potentially fatal• "hemolytic" refers to the breakup of red blood cells

o leads to anemiao destruction of platelets

leads to thrombocytopenia - low blood levels of platelets

promotes abdominal bleeding•  "uremic" refers to kidney failure• problems with the brain - seizures• coma may occur

Thrombotic Thrombocytopenic Purpura

• caused in the elderly • clotting of blood within small blood vessels• fragmentation of red blood cells

o leads to anemia• shortage of platelets

o causes easy bruising• neurologic abnormalities• impaired kidney functions• fever

                        Diagnosis

•  2 methods of testing stool specimenso growing bacteria in culture disheso testing for Shiga Toxin produced by the bacteria

• Blood Tests o performed periodically to look for the development of

HUS CBC - complete blood count  Blood levels of electrolytes BUN - blood urea nitrogen Creatinine - measure the function of the kidney

                     Prognosis

• generally good• most patients recover within 10 days just by treating the

symptoms• becomes more serious if HUS develops

o high survival rate but possibly fatalo most patients are under 5 yrs old so their body might not

be not strong enough to fight

                     Treatment

• antibiotics not proven usefulo studies have shown they may increase chances of

developing HUS• replacement of fluids and electrolytes to prevent dehydration• HUS and TTP require otherwise specific care

o may need dialysis

                        Activity    

Break up into groups of three and create one skit. Each skit should demonstrate one way in which the spread of E. coli can be prevented. You have 3 minutes to discuss and 2 minutes to perform.

Example: McDonalds employee does not wash his hands and patron gets sick. Re-do shows employee washing his hands after using the restroom.

                     Prevention

• WASH YOUR HANDS• COOK meats thoroughly• AVOID raw milk, unpasteurized dairy products and juices• AVOID swallowing water while swimming

                        History

• from 1982 to 2002 - 350 outbreaks in the USo 52 % foodborneo 21% unknowno 6% recreational watero 3% animal contacto 3 % drinking water

• 40 deaths• despite regulations outbreaks remain common• food transmission still the highest percentage• person-to-person transmission happening most commonly in

daycare centers • total recall when source identified

o approximately 25 million pounds of beef recalled

                       History II

• outbreaks provided information about the inadequacy of processing methodso U.S. Department of Agriculture created regulations for

processed meats• U.S. Food and Drug Administration revised Model Food

Code for restaurants• prevention methods targeting food preparers