Question

Which of the following is a bactericidal antibiotic?
A.Ofloxacin
B.Tetracycline
C.Chloramphenicol
D.Erythromycin

Answer 1

We must need to know that antibiotics are substances that can be of natural origin, semi-synthetic origin, or synthetic which act either by inhibiting the growth of microorganisms especially bacteria, or destroying their structure. To answer this question, one should understand the meaning of bacteriostatic, bactericidal action of antibiotics, and also antimicrobial substances. Antibiotics don’t act on viruses. If antibiotics are used in excess or inappropriately then they will not work because bacteria will develop resistance to it.

Complete step by step answer:
We need to remember that the antibiotics are antimicrobial substances (which destroy or inhibit the growth of microbes or pathogens). There are two ways were antibiotics show their action.
Bacteriostatic: (static means to stop), the substances which stop the growth of bacteria by altering change in the bacterial structure. E.g. tetracyclines, sulphonamides.
Bactericidal: (cidal means to kill), the substances which act by killing the bacteria as a whole by interfering with their replication, transcription, and translation. E.g. fluoroquinolones.
In the given question, Ofloxacin is a bactericidal antibiotic. It belongs to fluoroquinolones. It acts by blocking the DNA gyrase enzyme which is responsible for DNA replication.
We must know that tetracyclines are produced by Streptomyces bacteria and are bacteriostatic in action which acts by binding to S ribosomal subunit and blocks aminoacyl tRNA.
Chloramphenicol is bacteriostatic in action. It stops bacterial growth by binding to bacterial ribosomes. It is used against gram-negative bacteria and Streptococcus pneumonia.
Erythromycin is a macrolide antibiotic that is bacteriostatic in action. It acts by binding to the S subunit of ribosomes of bacterial rRNA.
The correct answer is option A.

Note:
As we know that antibiotics are the medicines which act against more than one type of bacteria and thus they are known as broad-spectrum antibiotics and narrow-spectrum antibiotics act against the particular type of bacteria. We should note that bacteriostatic is a reversible process and does not decrease the number of bacterial cells and are effective in high doses whereas bactericidal action is irreversible and causes a decrease in bacterial cells and is effective in low doses.