E. coli O157:H7
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What is the morphology and gram reaction of this pathogen (2) E. coli, including E. coli O157H7 is a gram-negative bacillus. What do (i) O157 and (ii) H7 attached to the name of this bacterium represent (2). The O157 is the serotype antigen that identifies the E. coli strain, and the H7 represents the antigen type on the bacteriums flagella. This strain of E. coli was harmless until it acquired the gene for a toxin via a genetic mechanism call transduction. Describe how a bacterium can acquire new genes by transduction. (2) With transduction the transfer of DNA between organisms involves mediation of viruses called bacteriophages or phages. A phage infected a susceptible bacterium and during its process of replication and assembly a phage incorporates a segment of bacterial DNA. The bacterium will lyses and releases the mature phages. One of the phages has the incorporated bacterial DNA, that one are called defective virus. This defective virus infected other bacterium but instead of injecting viral nucleic acid it is injecting bacterial DNA. The new infected bacterium will recombine its own DNA with the received bacterial DNA from the phages.
The virus will not replicate or lyses the cell because it is a defective virus. The bacterium survives and can use this new genetic material that was incorporated into its chromosome. In what year did this strain of E. coli first appear (1) E. coli O157H7 was first recognized as a pathogen in 1982. Name the toxin produced by this strain. State whether it is an endotoxin or an exotoxin. (2) The name of the toxin is Shiga-like toxin (SLT), it is also known by verocytotoxin. This toxin is an exotoxin. What is the incubation period of this disease (1) The incubation period is usually 2 to 5 days after infection with a range of 1 to 10 days. State 4 signs/symptoms of infection with this strain of E. coli (not of HUS). (2) Severe abdominal cramps, bloody diarrhea, vomiting and some fever. This pathogen is also found in cattle, swine and deer, but does not cause infections in them. Explain why.(1) This pathogen does not cause infection in cattle, swine and deer because they are the natural habitat (reservoirs) for that pathogen.
This pathogen is usually transmitted by contaminated food/water. State 3 other specific ways in which some one may acquire the pathogen (that is, other than from food or water). (3) Person-to-person contact in families and childcare centers, swimming in recreational water contaminated with E. coli O157H7, contact with farm animal, touching contaminated surface then touching their mouth. State 2 predisposing factors (other than age) to this disease. (2) Rural works, people who consume diets rich in fibers, immunosuppressed and people with stomach surgery are more susceptible to developing the disease. Some people develop HUS after being infected. What does HUS mean and describe its signs and symptoms.(3) HUS means Hemolytic Uremic Syndrome and its signs and symptoms include pallor, fever, bruising or nosebleeds because of the destruction of platelets, fatigue, shortness of breath, swelling of the body, especially hands and feet, jaundice, reduced flow of urine, kidney failure and death.
Antibiotics are usually not administered for this infection. How is the disease managed (1) The disease is managed by replacing fluids and electrolytes to treat or prevent dehydration. Which other type of drug (i.e. other than antibiotics) should definitely not be taken for this infection Explain why. (2) Drugs that are used to control diarrhea, like Imodium and Lomotil, should not be taken because these medicines can slow down the digestion process, allowing more time for the body to absorb the toxins. It can prolong illness, increase symptoms and trigger complications. This is a notifiable disease. What does this mean (1) A disease that by law must be reported to public health authorities at the time it is diagnosed.