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

Bactericidal vs Bacteriostatic

The main difference between bactericidal and bacteriostatic is that bactericidal antibiotics act by inhibiting the synthesis of the cell wall in microorganisms while bacteriostatic antibiotics inhibit the protein synthesis, thereby disturbing DNA replication and metabolism of microorganisms. One of the major differences between bactericidal and bacteriostatic is that bactericidal antibiotics kill the bacteria while the bacteriostatic antibiotics inhibit the growth and reproduction of bacteria, thereby inactivating them.

Bactericidal vs Bacteriostatic

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 dies 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 a reversible process because as soon the drug stops its activity, the bacteria easily resumes its normal function and growth. Bacteriostatic antibiotics have fewer side effects and are often prescribed by physicians.

Comparison Table Between Bactericidal and Bacteriostatic

Parameters of ComparisonBactericidalBacteriostatic
MeaningRefers to the killing of bacteriaRefers to inhibiting the growth and reproduction of bacteria.
ProcessIrreversible process.Reversible process.
Mode of actionIt inhibits the synthesis of the bacterial cell wall.Inhibits protein synthesis and DNA replication of bacteria.
Antibiotics usageEndocarditis, meningitis, neutropenia, osteomyelitisWound infection, urinary tract infection
Examplesß-lactum antibiotics, ofloxacin, penicillin, aminoglycosides, vancomycin, and cephalosporins.Chloramphenicol, tetracyclines, sulfonamides, erythromycin,  trimethoprim, spectinomycin, lincosamide,  macrolides, etc.

What is Bactericidal?

Bactericidal is the specification of drug category which prevents the body from bacteria by killing it. The mode of action of bactericidal antibiotics is: They inhibit the synthesis of the cell wall of bacteria.

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

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

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

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

One of the ß-lactum antibiotics known as penicillin attaches to penicillin-binding proteins, which in turn inhibits the cross-linking of the cell wall of bacteria.

The concentration of the antibiotic 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 in order to produce an aseptic environment.

This is especially done in operation theaters 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 and DNA replication along with 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 normalizes their activity.

This kind of antibiotic gets activated in accordance with the host’s immune system to prevent bacterial growth and reproduction. Bacteriostatic, when given in high doses, kill the bacteria and starts acting as a bactericidal.

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

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

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

Main Differences Between Bactericidal and Bacteriostatic

  1. Bactericidal are antibiotics that kill the bacteria, while bacteriostatic are antibiotics that prevent bacterial growth.
  2. Bactericidal antibiotics inhibit bacterial cell wall formation, while bacteriostatic antibiotics inhibit the protein synthesis and DNA replication of bacteria.
  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 the treatment of meningitis, or endocarditis while bacteriostatic antibiotics are used in the treatment of 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.
Difference Between Bactericidal and Bacteriostatic


Both bactericidal and bacteriostatic are used to prevent bacterial growth. The main difference is their mode of action as bactericidal acts by killing bacteria and bacteriostatic acts by inactivating the bacteria.

Bactericidal antibiotics work on eliminating the bacterial population, while bacteriostatic antibiotics aim to keep the bacterial population in check by inhibiting bacterial replication.

Both bactericidal antibiotics and bacteriostatic antibiotics are used depending on the action required, and the concentration required. There is no evidence that which of them is more powerful.

They are prescribed according to the relevance of the disease and the action required for a specific disease.


  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

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