Monobactams are a group of antibiotics that are often used as a backup medication or in combination with other antibiotics. The best-known representative is the antibiotic aztreonam.
What is monobactam?
Monobactams are a group of antibiotics that are often used as a backup medication or in combination with other antibiotics. Monobactams are among the semisynthetic antibiotics. Gram-negative bacteria produce a substance for this purpose, which is subsequently modified synthetically. Like other ß-lactam antibiotics, monobactam contains a monocyclic ß-lactam ring. ß-lactam is a cyclic organic chemical compound that contains an amide bond in the ring. However, monobactams do not contain another fused ring. This is a typical characteristic of ß-lactam antibiotics. Monobactams are stable to ß-lactamase. ß-lactamases are enzymes produced by various bacteria. They play a crucial role in the development of antibiotic resistance by bacteria. However, antibiotics from the monobactam group can be cleaved by extended spectrum ß-lactamases (ESBL). Thus, ESBL-producing bacteria such as E.coli and Klebsia are resistant to monobactams.
Pharmacologic action
Monobactams have a bactericidal effect. They inhibit the synthesis of the cell wall of bacteria. The cell wall is vital to bacteria. They have a very high osmotic particle concentration within their cell plasma. If the cell wall is no longer present or is damaged, water flows into the cell interior of the bacteria. They swell so that after some time the plasmalemma, a cell membrane that encloses the cytoplasm, ruptures. The bacteria burst and thus perish. The spectrum of action of monobactams is quite broad. They are mainly effective in the Gram-negative range. Gram-negative bacteria can be stained red in the Gram stain. In contrast to Gram-positive bacteria, they possess not only a thin peptidoglycan layer of murein but also another outer cell membrane. Gram-negative pathogens include, for example, staphylococci, streptococci, mycobacteria, nocardia, listeria and clostridia. Monobactams have no effect on Gram-positive pathogens such as Legionella, Campylobacter, Helicobacter pylori, Enterobacteria, Borrelia and Chlamydia. Anaerobes also cannot be treated with antibiotics from this group. Because monobactams cannot be absorbed from the gastrointestinal tract, they must be administered parenterally. This means that they are usually injected into the vein. Intramuscular or inhalation administration is also possible. The bioavailability of monobactams is almost 100 percent. Metabolism takes place in the liver. Subsequently, the kidneys excrete the resulting metabolites.
Medical application and use
Monobactams function mainly as reserve antibiotics. These particular antibiotics may only be used for infections with resistant pathogens. They are also used directly for severe infections when infestation by resistant pathogens is expected. It should be noted that reserve antibiotics are by no means more effective than standard antibiotics. In fact, they often have a poorer effect and are associated with more side effects. However, they are still effective against resistant pathogens. Monobactams are used in particular for the treatment of complicated urinary tract infections or intra-abdominal infections. For this purpose, the drugs are combined with the antibiotics metronidazole or clindamycin. The effect of the monobactams must also be confirmed by an antibiogram. The main indication for the use of aztreonam, the main representative of the monobactams, is chronic lung infection with the pathogen Pseudomonas aeruginosa in patients with cystic fibrosis. Cystic fibrosis is a hereditary disease characterized by the production of a viscous secretion by the exocrine glands of the body. Antibiotics from the monobactam group are also used in patients allergic to penicillin or cephalosporin.
Risks and side effects
Monobactams should not be used in children younger than 18 years. Their use is also contraindicated in patients with renal dysfunction or in patients allergic to beta-lactam antibiotics. Adverse drug reactions include cough and wheezing breath sounds. Pain in the throat or larynx may also occur.Other side effects include nasal congestion and secretion of thin to mucous nasal secretions. Some patients also suffer from fever and chest discomfort during treatment with monobactams. Bronchial spasm may also be among the possible side effects. Furthermore, a skin rash may develop during treatment.
