Question

A patient has a blood infection caused by a gram negative bacteria species. Why might it be dangerous to treat this infection with fast acting "cidal" antibiotic?

Answer 1

There are two kinds of antibiotics to treat bacteria.

(1) Bacteriostatic- This type helps to just inhibit the growth of the bacteria but does not completely eliminate it.

(2) Bactericidal- This type of antibiotic completely destroys or kills the bacteria.

Antibiotics should be prescribed to patients based on the type and severity of the infection. A bactericidal antibiotic is used to treat patients having severe infections with serious clinical condition, in the cases it would be fatal to wait for the time of action of a bacteriostatic antibiotic. The bactericidal antibiotic is also used to treat patients with poor immunity as in the cases of primary and secondary immunodeficiencies, where the patients do not have the ability to fight back the infection on their own.

In milder cases of infections, or in the cases of patents with a healthy immune system, the most preferred type of antibiotic is the bacteriostatic antibiotic. Also it is important to know that the human body comprises of a huge aggregate of microorganisms termed the 'human microbiome'. The human microbiome includes bacteria, virus, fungus, archea and protists and reside in a number of tissues and body fluids. The human microbiome is harmless to the human body and in some cases even beneficial. Some of the bacteria in the gut help in digestion and also secrete vitamins (ex. Vitamin B12).

Therefore, if a patient has a blood infection caused by a gram negative bacterial species, treatment with a fast reacting 'cidal' antibiotic might also kill the harmless gram negative bacteria present in the body, particularly the intestine and this might disturb the human microbiome balance.