3. Antibiotics

Amoxicillin Mechanism of Action

Amoxicillin is in the class of beta-lactam antibiotics. Beta lactams act by binding to penicillin-binding proteins that inhibit a process called transpeptidation, leading to activation of autolytic enzymes in the bacterial cell wall. This process leads to lysis of the cell wall, and thus, the destruction of the bacterial cell. This type of activity is referred to as bactericidal killing.

Azithromycin Mechanism of Action

Azithromycin prevents bacteria from growing by interfering with their protein synthesis. It binds to the 50S subunit of the bacterial ribosome, thus inhibiting the translation of mRNA.

Cefuroxime Mechanism of Action

It’s a Cephalosporin group antibiotic, exerts bactericidal activity by interfering with bacterial cell wall synthesis and inhibiting cross-linking of the peptidoglycan. The cephalosporins are also thought to play a role in the activation of bacterial cell autolysins which may contribute to bacterial cell lysis.

Cephalexin (Cefalexin) Mechanism of Action

It’s a Cephalosporin group antibiotic, exerts bactericidal activity by interfering with bacterial cell wall synthesis and inhibiting cross-linking of the peptidoglycan. The cephalosporins are also thought to play a role in the activation of bacterial cell autolysins which may contribute to bacterial cell lysis.

Ciprofloxacin Mechanism of Action

Ciprofloxacin is a bactericidal antibiotic of the fluoroquinolone drug class. It acts on bacterial topoisomerase II (DNA gyrase) and topoisomerase IV. Ciprofloxacin’s targeting of the alpha subunits of DNA gyrase prevents it from supercoiling the bacterial DNA which prevents DNA replication.

Clarithromycin Mechanism of Action

Clarithromycin, a macrolide antibiotic, inhibits bacterial protein synthesis by binding to the bacterial 50S ribosomal subunit. Binding inhibits peptidyl transferase activity and interferes with amino acid translocation during the translation and protein assembly process, and prevents bacterial protein synthesis.

Clindamycin Mechanism of Action

It is a bacterial protein synthesis inhibitor by inhibiting ribosomal translocation in a similar way to macrolides. It does so by binding to the 23S RNA of the 50S subunit of the ribosome. Clindamycin is bacteriostatic.

Co-amoxiclav Mechanism of Action

Co-amoxiclav is a combination of Amoxicillin and Clavulanic acid. Clavulanic acid blocks the chemical defense, known as beta-lactamase, that some bacteria produce against penicillin group antibiotics such as amoxicillin. Co-amoxiclav is active against bacterial infections that have become resistant to amoxicillin.

Co-trimoxazole Mechanism of Action

Co-trimoxazole, generally bactericidal, a combination of trimethoprim and sulfamethoxazole. It acts by sequential blockade of folic acid enzymes in the synthesis pathway. The sulfamethoxazole component inhibits the formation of dihydrofolic acid from para-aminobenzoic (PABA), whereas trimethoprim inhibits dihydrofolate reductase. Both drugs block folic acid synthesis, preventing bacterial cell synthesis of essential nucleic acids.

Doxycycline Mechanism of Action

Doxycycline is a tetracycline group, a broad-spectrum antibiotic. It inhibits the synthesis of bacterial proteins by binding to the 30S ribosomal subunit, which is only found in bacteria. This prevents the binding of transfer RNA to messenger RNA, so new proteins cannot be made. This stops bacterial growth giving the immune system time to kill and remove the bacteria.

Flucloxacillin Mechanism of Action

Like other β lactam antibiotics, flucloxacillin acts by inhibiting the synthesis of bacterial cell walls. It inhibits cross-linkage between the linear peptidoglycan polymer chains that make up a major component of the cell wall of Gram-positive bacteria. 

Gentamycin Mechanism of Action

Gentamicin is and Aminoglycoside, “irreversibly” bind to a specific 30S subunit of the ribosome. This leads to interference with the initiation complex, misreading of mRNA so incorrect amino acids are inserted into the polypeptide leading to nonfunctional or toxic peptides and ultimately inhibits bacterial protein synthesis.

Levofloxacin Mechanism of Action

Levofloxacin is a bactericidal antibiotic of the fluoroquinolone drug class. It acts on bacterial topoisomerase II (DNA gyrase) and topoisomerase IV. Levofloxacin’s targeting of the alpha subunits of DNA gyrase prevents it from supercoiling the bacterial DNA which prevents DNA replication.

Meropenem Mechanism of Action

Meropenem is a broad-spectrum carbapenem antibiotic. It inhibits bacterial cell wall synthesis like other β lactam antibiotics, thus it acts by binding to penicillin-binding proteins that inhibit a process called transpeptidation, leading to activation of autolytic enzymes in the bacterial cell wall. This process leads to lysis of the cell wall, and thus, the destruction of the bacterial cell. Meropenem is bactericidal except against Listeria monocytogenes, where it is bacteriostatic.

Metronidazole Mechanism of Action

Metronidazole is of the nitroimidazole class. It inhibits nucleic acid synthesis by disrupting the DNA of microbial cells. They also lead to the production of toxic metabolites, which may damage the DNA of replicating organisms, usually anaerobic bacteria and protozoans

Vancomycin Mechanism of Action

The bactericidal action of vancomycin results from inhibition of cell wall biosynthesis. Vancomycin forms hydrogen bonds & prevents incorporation of N acetylmuramic acid (NAM) and N acetylglucosamine (NAG) peptide subunits from being incorporated into the peptidoglycan matrix, which forms the major structural component of Gram positive cell walls. Additionally, vancomycin alters bacterial cell membrane permeability and RNA synthesis. Vancomycin is not active in vitro against gram-negative bacilli, mycobacteria, or fungi.