Question

Background:For the vaccine she must incorporate the gene for the S. pneumoniae antigen into a bacterium that will survive in the yogurt and will express the gene producing the antigen molecule. One organism found in yogurt is Streptococcus thermophilus. Dr. Bimmel begins her plan to transform S. thermophilus with a plasmid vector encoding the antigen gene.

First Dr. Bimmel must choose a plasmid cloning vector. Dr. Bimmel understands that a gene encoding resistance to antibiotics is commonly used to select for recombinant organisms (she does not want to include such a gene in her final construct for fear that it would be transferred to normal flora in the gut of the immunized children). As such, her final recombinant S. thermophilus strain will need some further genetic manipulations. However, for a phase one study, where the vaccine will be tested in the laboratory in animals, it is ok.

Question: Is Dr. Bimmel right to be concerned about the presence of antibiotic resistance genes, even in the absence of selection? What are the risks (if any( of leaving the antibiotic resistance genes in the vector for the final product? What are the advantages (if any) of leaving the antibiotic resistance genes in the plasmids?

Answer 1

Please find the answers below:

Is Dr. Bimmel right to be concerned about the presence of antibiotic resistance genes, even in the absence of selection?

Answer: Yes. Dr. Bimmel is right to be concerned about the presence of antibiotic resistance genes even in the absence of selection since some of the bacteria might simply fail to remove the antibiotic-resistance gene from their inserts and thus these bacterial colonies, if entered the human host, will impart antibiotic resistance to them. Hence, a serious medical situation might arise.

What are the risks (if any( of leaving the antibiotic resistance genes in the vector for the final product?

Answer: As the most potential risk of leaving antibiotic resistnace gene in the final product, the individuals which will be immunized with this vaccine will tend to develop an inherent resistance against the use of this antibiotic, making them resistant in nature. This demands immediate medical attention because a number of pathological microflora might infect such as human host.

What are the advantages (if any) of leaving the antibiotic resistance genes in the plasmids?

Answer: The only possible advantage of presence of the antibiotic resistance gene in the plasmid is the screening ability of the experimenter between immunized and non-immunized individuals. Secondarily, if the host was initially susceptible to antibiotic due to hypersensitivity, the presence of an antibiotic resistance gene would provide him immunity against such an anaphylatic shock.