Antibiotics are used to treat a wide variety of bacterial infections and have sa

Question

Antibiotics are used to treat a wide variety of bacterial infections and have saved millions of lives since they were first introduced in the 1940s and 1950s.

According to their mechanism of action, antibiotics can be divided into three main groups, those inhibiting cell wall synthesis, those inhibiting protein synthesis and those that inhibit nucleic acid synthesis.  For example, penicillin and its related compounds prevent susceptible bacteria from creating a cell wall.  They do this by binding to and inactivating an enzyme (transpeptidase).

  Horizontal gene transfer is made possible by the existence of mobile genetic elements, such as plasmids (extrachromosomal genetic material), transposons (“jumping genes”) and bacteria-infecting viruses (bacteriophages).  These elements are transferred between organisms through different mechanisms, which in prokaryotes include transformation, conjugation, and transduction.

1. Describe the manner in which the DNA can be transferred from one cell to another.

2.Choose a disease or an organism that has a well-documented mechanism of resistance (such as methicillin resistant Staphylococcus aureus - MRSA or tuberculosis) and identify the gene or genes that confer resistance and the method of DNA transfer thought to contribute to its spread. 

3.Discuss the danger that antibiotic resistance poses in today’s society, consider how man has contributed to this and suggest any strategies that you think may be able to halt it or prevent its expansion

Explanation / Answer

Hi,

1. There are 3 ways a gene can be transferred from one cell to another ( excluding the obvious way of vertical transfer, from mother to daughter cell) .

.A Transformation: naked DNA is uptaken naturally by the cells. These DNA fragments are from dead cells which are freely moving around in nature.

B. Transduction: Virus mediated. The phages when they attack the bacterial cells, carry certain genes of its host with it, which are then transferred to the next host.

C. Conjugation: The so called sexual method, in which a donor bacteria transfers some of its genes to the recipient via a conjugation tube called pilus.

2. An example of important gene imparting resistance to an antibiotic is: AmpC -lactamases. They belong to the class of cephalosporinases encoded on the chromosomes of many of the Enterobacteriaceae and a few other organisms. They mediate resistance to cephalothin, cefazolin, cefoxitin, most penicillins, and -lactamase inhibitor--lactam combinations. They code for enzyme amp-c, which hydrolyses the cephalosporins thus neutralizing the antibiotic. This gene is transferred via plasmids from one cell to another. The most common way of transfer of a plasmid is conjugation.

3. The impact of antibiotic resistence can be understood only when we know the revolution the antibiotics have brought about. During the world war, more people would die due to wound infections than any other reason. The discovery of antibiotic paved a way to save these people, both during was and also in the time of peace. The resistance against the antibiotic means literally the antibiotic fails to act and a patient dies due to infections. This is a serious threat to mankind as the resistance gene evolution is much faster than the development of newer and more effective antibiotics. The bacteria can acquire resistance to natural ways or also by induced ways. The rise in resistance part is also due to misuse of antibiotics was the man. The unconditional and unrestricted use of antibiotics, improper dosage and improper prescription has led to the development of resistant bacterial strains.

The solution to this problem lies in developing the new class of antibiotic which does not rely on traditional antibiotic targets. Reduced and limited prescriptions, avoiding antibiotics as much possible. The war against resistance is easier said than fought.

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