Antibiotic
Beta-lactamase inhibitors
Clavams (Classical β-lactam-structured inhibitors) Inhibitor Structure type Mechanism Effective vs β-lactamase class Unique features Clavulanic acid β-lactam (oxazolidine ring) Irreversible suicide substrate Class A (TEM, SHV); weak vs C/D Only natural inhibitor (from Streptomyces clavuligerus); first marketed (1981) Sulbactam β-lactam (penicillanic acid sulfone) Irreversible acyl-enzyme Class A > C (limited) Has intrinsic antibacterial activity vs […]
Antibiotic – intrinsic resistance
Enterobacterales & Aeromonas Enterobacterales and Aeromonas are intrinsically resistant to benzylpenicillin, glycopeptides, lipoglycopeptides, fusidic acid, macrolides (Except Azithromycin, effective for typhoid/paratyphoid fever and erythromycin for travellers’ diarrhoea), lincosamides, streptogramins, rifampicin, and oxazolidinones. Bacteria Beta-lactams Non-beta-lactams Klebsiella pneumonia complex,Klebsiella oxytocaRoultella sp.Citrobacter koseri,Citrobacter amalonaticus Amoxicillin, Ticarcillin Klebsiella aerogenes,Enterobacter cloacae complexCitrobacter freundiiHafnia alvei Amoxicillin, Coamoxiclav,1st generation cephalosporinsCefoxitin Serratia […]
Daptomycin
Class: Cyclic lipopeptideSource: Streptomyces roseosporusDiscovered: 1980s; approved for use in 2003 (FDA)Molecular weight: 1620 DA. Mechanism of action: The Daptomycin (DAP) combines with Calcium ions to form a positively charged complex that attaches to the bacterial cell membrane (preferably at the nascent septa). This attachment depends upon the presence of phospholipid phosphatidylglycerol (PG). After attachment, DAP forms […]
Plazomicin
Nature of the antibiotic Class: Next-generation aminoglycoside (neoglycoside), semisynthetic (sisomicin based). It is not inactivated by most aminoglycoside-modifying enzymes (AME).Molecular weight: 592.68. It is synergistic with many antibiotics, including piperacillin-tazobactam. Mechanism of resistance Enterobacteriaceae: modification of the ribosomal binding site due to expression of 16S rRNA methyltransferases. Adverse effect Spectrum Gram-positive Staphylococcus (MSSA, MRSA, and coag neg […]
Tigecycline
Nature: Glycylcycline, a member of the tetracycline family. Semisynthetic derivative of minocycline.MW: 585.6 Mechanism of action: 1. Bind to 30S ribosomal subunit and inhibit protein synthesis – It inhibits the attachment of aminoacyl tRNA to the A site and prevents chain elongation, i.e. block the translation process.2. Inhibit mitochondrial protein synthesis by binding to 70 […]
Fosfomycin
Nature: Small (Mol weight – 138) phosphoenolpyruvate analogue manufactured synthetically but originally obtained from Streptomyces fradiae and some Pseudomonas sp.A broad-spectrum, a bactericidal antibiotic. Mechanism of action: Inhibit bacterial cell wall formation at a very early stage by inactivating enol pyruvate transferase (MurA).MurA catalyzes the transfer of enolpyruvate from phosphoenolphyruvate to uridine diphospho-N-acetylglucosamine (UNAG), the first step […]
Ceftolozane-tazobactam
Class: 5th generation cephalosporin.Available as ceftolozane-tazobactam, a beta lactam-beta lactamase inhibitor (BLBLI) combination. Mechanism of Action: Similar to other beta-lactam antibiotics. It binds to the penicillin-binding protein (PBP) to inhibit the biosynthesis of the cell wall.It binds with the PBP3 of E coli and PBP3, PBP1a, and PBP1b of Pseudomonas aeruginosa. Mechanism of resistance: It is […]
Lefamulin
Nature of the antibiotic Semi-synthetic, pleuromutilin class.Molecular weight – 567.79 gm/mole Pleuromutilins Pleuromutilins (produced by Pleurotus sp.), discovered in the 1950s, have a tricyclic mutilin core.Tiamulin – the first member of this group, was approved for veterinary use in 1979.Retapamulin – topical pleuromutilin was approved for human use in 2007. Mechanism of action It inhibits protein […]
Metronidazole
Class: Nitroimidazole.Mol weight: 171First used in 1960. Mechanism of action: Metronidazole enters the susceptible (bacterial/parasite) cells by passive diffusion. It gets activated to a nitroso compound which causes oxidative damage to the DNA. It also inhibits DNA repair. The conversion of metronidazole to nitroso compound creates a concentration gradient, and more metronidazole enters the cells. The aerobic bacteria lack the necessary […]