E. coli O157:H7

Topics: Bacteria, Virus, Escherichia coli Pages: 2 (711 words) Published: October 28, 2014
E. coli O157H7 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 O HYPERLINK http//www.emedicinehealth.com/script/main/art.asparticlekey5469 serotype antigen that identifies the E. coli strain, and the H7 represents the antigen type on the HYPERLINK http//www.emedicinehealth.com/script/main/art.asparticlekey2416 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...
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