Antibiotic
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 […]
Mechanism of resistance in Enterococcus
Enterococci are intrinsically resistant to many classes of antibiotics – like cephalosporins, Aminoglycoside (low-level resistance), macrolides, clindamycin, quinupristin-dalfopristin (E faecalis), Fusidic acid, Sulfonamide [EUCAST], which limits our options when we try to treat Enterococcal infections. Most clinical infections are caused by Enterococcus faecalis, followed by Enterococcus faecium.Other Enterococci occasionally isolated from the clinical specimen are […]