Bacteriostatic antibiotics limit the growth of bacteria by interfering with bacterial protein production, DNA replication, or other aspects of metabolism while not necessarily directly harming the organism. Upon removal of the bacteriostatic agent, the bacteria can regrow as opposed to bactericidal agents that directly kill bacteria.
Chloramphenicol prevents protein chain elongation via inhibition of peptidyltransferase activity of the 50S prokaryotic ribosomal subunit preventing peptide bond formation. Peptidyltransferase enzymes form peptide bonds between adjacent amino acids using tRNAs during the translation process of protein biosynthesis.
Chloramphenicol has excellent blood brain barrier penetration and is active against the three main bacterial causes of meningitis including Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenzae. In developed nations, it is only used when patients have a severe penicillin or cephalosporin allergy. However, in developing nations, it is commonly used to treat meningitis due to low cost.
Chloramphenicol may be used to treat patients with rocky mountain spotted fever (RMSF). Though doxycycline is the drug of choice for treating RMSF, pregnant women may be treated with chloramphenicol as an alternative.
One of the most serious adverse effects associated with chloramphenicol treatment is bone marrow toxicity which can cause anemia. This is a direct toxic effect of the drug and is typically reversible.
Aplastic anemia is a condition characterized by insufficient production of new blood cells to replenish blood cells. Unlike anemia which refers to only low red blood cell counts, aplastic anemia refers to lower counts of all three blood types including red blood cells, white blood cells, and platelets. This side effect is rare and generally fatal.
IV chloramphenicol use is associated with gray baby syndrome, which occurs in newborns because they do not yet have fully functional liver enzymes including UDP glucuronyl transferase to metabolize chloramphenicol. This leads to severe adverse effects including cyanosis, discoloration of the baby to an ashen gray color, hypotension and cardiovascular collapse.
Resistance to chloramphenicol is caused by an enzyme called chloramphenicol acetyltransferase, which inactivates chloamphenicol by covalently linking an acetyl group to a hydroxyl group on the chloamphenicol molecule. The acetylation prevents the drug from binding to the ribosome.
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