Difference Between Bactericidal and Bacteriostatic

Antibiotics are a class of medicine used to counteract microorganisms. Antibacterial activity refers to the act of prevention from bacteria. Antibiotics are divided into two types based on their mode of action: Bactericidal and Bacteriostatic.

Both have the same function: to destroy bacteria and counteract bacterial activity. Both of them differ in the mode of action and the conditions in which they are prescribed.

Bactericidal vs Bacteriostatic

Bactericidal antibiotics act by inhibiting the cell wall synthesis in microorganisms, while bacteriostatic antibiotics inhibit protein synthesis, thereby disturbing the DNA replication and metabolism of microorganisms. Bactericidal antibiotics kill the bacteria, while bacteriostatic antibiotics inhibit the growth and reproduction of bacteria, thereby inactivating them.

Bactericidal means the process involving the killing of bacteria. This process is irreversible as the bacteria, once killed, cannot be retrieved. The bactericidal antibiotics act primarily by inhibiting cell wall synthesis.

This leads to leaching out of the cell contents of bacteria, and the bacteria die off.

Bacteriostatic means the process of inhibition of the growth of bacteria. It does not kill the bacteria as in the case of bactericidal.

This is reversible because the bacteria quickly resume their normal function and growth after the drug stops its activity. Bacteriostatic antibiotics have fewer side effects and are often prescribed by physicians.

Comparison Table

Parameters of Comparison	Bactericidal	Bacteriostatic
Meaning	Refers to the killing of bacteria	Refers to inhibiting the growth and reproduction of bacteria.
Process	Irreversible process.	Reversible process.
Mode of action	It inhibits the synthesis of the bacterial cell wall.	Inhibits protein synthesis and DNA replication of bacteria.
Antibiotics usage	Endocarditis, meningitis, neutropenia, osteomyelitis	Wound infection, urinary tract infection
Examples	ß-lactam antibiotics, ofloxacin, penicillin, aminoglycosides, vancomycin, and cephalosporins.	Chloramphenicol, tetracyclines, sulfonamides, erythromycin,  trimethoprim, spectinomycin, lincosamide,  macrolides, etc.

What is Bactericidal?

Bactericidal is the specification of a drug category that prevents the body from bacteria by killing them. The mode of action of bactericidal antibiotics is: They inhibit the synthesis of the bacteria’s cell wall.

The improper formation of the cell wall or the damaged cell wall leads to the leaching out of bacterial contents.

This ultimately leads to the death of the bacteria, and thus the amount of bacteria decreases eventually in the body. This is an irreversible process as the bacteria is killed and cannot be reversed.

This kind of antibiotic does not work per the host’s immune system. Some bactericidal antibiotics are also said to inhibit protein synthesis and bacterial lipids and enzymes.

Some of the drugs opt for more than one mode of action. When used in rapidly dividing bacteria, bactericidal antibiotics show the most activity.

One of the ß-lactam antibiotics, penicillin, attaches to penicillin-binding proteins, inhibiting the cross-linking of bacteria’s cell walls.

The antibiotic concentration required to kill 99.99% of the bacteria is known as minimum bactericidal concentration(MBC).

Bactericidal can be referred to as any substance that kills bacteria. Examples include disinfectants, antibiotics, and antiseptics.

These activities are used in hospitals and other healthcare facilities to completely kill the bacteria on the surface of the things to produce an aseptic environment.

This is mainly done in operation theatres and intensive care units. Common chemicals used in case of disinfecting are alcohol.

What is Bacteriostatic?

Bacteriostatic is the specific category of antibiotics that inactivates the bacteria by limiting its growth and multiplication of cells, i.e., reproduction. The mode of action of bacteriostatic antibiotics:

They inhibit the protein synthesis, DNA replication, and other metabolic activities of bacteria. This is a reversible process.

When the drug is removed from the body or its pharmacological action wears off, the bacteria resume their growth and normalize their activity.

This antibiotic gets activated by the host’s immune system to prevent bacterial growth and reproduction. When given high doses, Bacteriostatic kills the bacteria and starts acting as a bactericidal.

The minimum concentration of a drug that inhibits a considerable amount of bacterial growth to show the suppressing activity of bacteria is known as minimum inhibitory concentration (MIC).

Bacteriostatic treatments freeze bacterial activity and stop them from multiplying and showing their action. This process is used in the pasteurization of milk.

The bacteriostatic activity aims to stall the cellular activities of bacteria rather than kill them. They are usually of a broad mechanism of action.

Main Differences Between Bactericidal and Bacteriostatic

1. Bactericidal are antibiotics that kill bacteria, while bacteriostatic antibiotics prevent bacterial growth.
2. Bactericidal antibiotics inhibit bacterial cell wall formation, while bacteriostatic antibiotics inhibit bacteria’s protein synthesis and DNA replication.
3. The mode of action of bactericidal is irreversible, while that of bacteriostatic is reversible.
4. Bactericidal antibiotics work on bacteria by killing them, while bacteriostatic antibiotics tend to inhibit bacterial growth by preventing the synthesis of protein.
5. Bactericidal antibiotics are used in treating meningitis or endocarditis, while bacteriostatic antibiotics are used to treat wound infections or urinary tract infections.
6. Bactericidal drugs can show side effects such as toxic shock syndrome in humans, whereas bacteriostatic antibiotics rarely show side effects.

References

1. https://aac.asm.org/content/58/8/4573.short
2. https://academic.oup.com/cid/article/38/6/864/320723?login=true
3. https://academic.oup.com/jac/article/70/2/382/2911103?login=true