What is a Bacteriostatic?

Mary McMahon
Mary McMahon

A bacteriostatic is a compound which has the effect of preventing bacterial growth. These agents do not kill bacteria like bactericidal compounds; instead, they limit further replication of bacteria at the site where they are introduced. Several antibiotic drugs are bacteriostatic agents, with tetracyclines being a notable example. While drugs which actively kill bacteria are preferred for many types of treatments, there are settings in which these drugs may be better for the treatment of bacterial infections.

Several antibiotic drugs are bacteriostatic agents.
Several antibiotic drugs are bacteriostatic agents.

These drugs can work in a number of different ways; one common technique is to interfere with DNA replication in the target bacteria or to inhibit protein production. When this happens, the organisms are unable to multiply and eventually they die off, allowing the immune system to process them and remove them from the body. This is one reason why fully finishing a course of antibiotics if critical. If someone on a bacteriostatic drug stops taking it, the inhibited bacteria can start to replicate again, causing the infection to recur.

People with compromised immune systems should take precautions to avoid exposure to germs, despite the availability of bacteriostatic medications.
People with compromised immune systems should take precautions to avoid exposure to germs, despite the availability of bacteriostatic medications.

Courses of these drugs tend to be longer than those of some bactericidal compounds, because it is important to fully inhibit bacterial growth until all of the organisms are dead. In high doses, some of these drugs may also be capable of killing bacteria in addition to suppressing growth. A doctor may prescribe such drugs for a variety of reasons, depending on the nature of a patient's infection and other factors.

Drug companies also manufacture bacteriostatic water for injection. This product is treated so that bacteria cannot grow in it while it is stored, transported, and prepared for delivery. These ampules can be mixed with other solutions for injection and used in clinical and hospital settings in patient treatment. Although the solution itself is bacteriostatic, it is still possible for contamination to occur if the shot is not performed properly or the environment is not kept clean.

As with other antibiotics, there is a risk that using bacteriostatic compounds too freely could allow bacteria to develop resistance to them. For this reason, these drugs are only prescribed when they are clearly necessary, and patients are reminded to finish courses of drugs so that they do not contribute to the development of antibiotic-resistant bacteria. Such bacteria can be especially problematic for people with compromised immune systems who lack even rudimentary natural defenses against bacteria and other microorganisms, and who can experience severe infections as a result.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


This is a good introduction to these kinds of drugs. I had always thought antibiotic drugs completely killed off bacteria, not just limited their growth.

One story I will share is that I lived in Asia for several years. They would prescribe antibiotic drugs for sicknesses, just as doctors in the United States do. The only odd difference I noticed is that doctors over there would sometimes prescribe antibiotics for only a few days when the same medications here would be prescribed for anywhere from ten days to two weeks.

I never understood that because I was told that the body would develop resistance to the medication if you took your medication that way.

Anyway, I’m not a doctor - it was just a pattern I noticed.

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