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Dan, a usually healthy 16-year-old, celebrated the end of school at the home of one of his schoolmates. They bought some ground beef and had a barbecue. When the hamburgers were done, they added mayonnaise and some vegetables to the buns. |
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They had a great time. Three days later, Dan began to get severe abdominal pains and after a few hours, severe diarrhea. By that time, Dan found out that most of his friends who had been at the barbecue were also suffering from the same symptoms.
Dan's mother made him go to the doctor, who told him that he had contracted a food-borne disease which could probably be attributed, among other possibilities, by the bacteria: E. coli or Salmonella
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E. coli (strain O157) |
Salmonella |
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Which illness is caused by this organism? |
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How is the infection spread? |
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What are the main pathogenic types of the bacteria? |
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Which type is the likely cause of Dan's food-borne illness? |
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What are the symptoms of the infections? |
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Main toxins |
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When does symptom onset occur? |
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How can the infection be diagnosed? |
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How can the infection be treated? |
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Can the bacteria be treated by antibiotics? |
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What are possible complications of the illness? |
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Back to Dan…
Two days after visiting the doctor, Dan's diarrhea had not improved. Dan also found that he had blood in his feces. His mother did not need to push him to go to the doctor, his anxieties did the job for her.
After learning about the symptoms caused by Salmonella and E. coli, can you guess what the doctor's diagnosis will be? |
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After a week, Dan felt a lot better, and after 12 days, he was completely healthy, even though he had not taken any medication.
Most of the food-borne infections in the western world follow the same course as Dan's illness did. However, a few might end in serious complications or even death. |
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More about the spread of E. coli infections in the western world:
At this site you will find a lot of news about E. coli
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1.Read the news report and write about five ways (five food agents) in which one can contract an E. coli (strain O157) infection. |
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The majorproblem in treating E. coli is the liberation of toxins from the bacterium following antibiotic treatment, which can worsen the clinical symptoms.
The second reason is: antibiotic resistance.
Antibiotic resistance in bacteria has become a serious problem in today's society. Through evolution, tougher bacteria that cannot be killed by antibiotics are surviving and reproducing: one of the reasons for this is overuse of antibiotics.
Resistance to antibiotics in E. coli is determined by plasmids. Two conjugative resistance factors have been identified: a 52-MDa plasmid coding for resistance to ampicillin, streptomycin and sulfonamide in some of the strains and a 77-MDa plasmid coding for resistance to ampicillin, streptomycin, kanamycin, tetracycline and sulfonamide in other strains.
We can recognize resistant E. coli strains by spreading them on plates containing antibiotic: only the bacteria containing the drug resistance plasmid will be able to grow.
Look at these agar plates and indicate which of these strains is resistant to ampicillin: |
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Escherichia coli O157:H7
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 E. coli Antibiotic Resistotypes |
| The Development of Antibiotic Resistance in E. coli |
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About vaccines to E. coli |
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TheE. coli genome also serves as a genetic tool. More about this issue |