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Lecture 25

MBIO 1010 Lecture 25: Lecture 25

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MBIO 1010
Christopher Rathgeber

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Microbiology 1010 – Lecture Notes 27.13 β-Lactam Antibiotics Cell wall synthesis inhibitors, e.g. penicillins  and cephalosporins Comprise of over 50% of antibiotics used around the world  Penicillins o Discovered by Alexander Fleming Target cell wall (peptidoglycan synthess) Transpeptidation Effective against Gram- positive bacteria Some synthetic forms active against Gram- negative bacteria Figure 27.25 Penicillins. Bacterialstatic – keeps it constant = rely on a functioning immune system Bacterialccidal – it destroys the bacterium to it’s entirety Urinary track infections – usually gram neg. 27.13 β-Lactam Antibiotics: Penicillins and Cephalosporins Cephalosporins o Fungus, Cephalosporium sp. o Structurally different from penicillins Figure 27.26 Ceftriaxone. Fig 27.25 Penicilllin 133 Microbiology 1010 – Lecture Notes 27.13 β-Lactam Antibiotics: Penicillins and Cephalosporins (Continued…) Cephalosporins o Similar mode of action to penicillins o Broader spectrum than penicillins o Resistant to β-lactamases o Commonly used to treat gonorrhea Broad spectrum (some gram. Neg coverage). Where the bacteria shows resistance to the B- Lactam …. Cephalosporin's are resistant to the resistance of the bacteria\\ Chlamydia is intercellular (live within our cells) 27.14 Antibiotics From Bacteria Aminoglycosides Amino sugars bonded by glycosidic linkage E.g. streptomyci, kanamycin, neomycin, gentamicin o  Target 30S subunit of the ribosome  o Useful against Gram-negative bacteria  Not as commonly used ‘last resort antibiotics’ Figure 27.27 Aminoglycoside antibiotics: streptomycin and kanamycin. Sugars that are linked by glucosidic bonds O-link sugars and the common is streptomycin. Target the 30S subunit Interaction with the mRNA = 30s role 134 Microbiology 1010 – Lecture Notes 27.14 Antibiotics From Bacteria (Continued…) Macrolides o Lactone rings bonded to sugars o E.g. erythromycin (Streptomyces erythreus) o Broad spectrum  Target 50S subunit of the ribosom Partial inhibition of protein synthesis  preferential translation of some proteins Figure 27.28 Erythromycin, a macrolide antibiotic. Clinically used very often. Allows bacterium to leave some proteins unharmed – but others are informed. Because of this – he has fewer proteins and can’t sustain. 27.14 Antibiotics From Bacteria (Continued…) Tetracyclines o Produced by several species of Streptomyces o Broad-spectrum o Natural and semisynthetic o Inhibit 30S subunit of ribosome Most widely used antibiotic along with penicillins Veterinary and as growth promoters resistance Figure 27.29 Tetracycline. Streptomyces = produced by these species Broad spectrum = both gram pos. and gram neg. Natural and semi- synthetic where other organisms are producing this and sometimes we put them I the lab to make something that is better and more better fits our needs by modifying them. Problems with the drug – inhibit infections inside of farm animals. So therefore, because this antibiotic is going into our food = over use and there is a big amount of resistance. Lose effectiveness. 135 Microbiology 1010 – Lecture Notes 27.14 Antibiotics From Bacteria (Continued…) Novel Antibiotics Daptomycin  Produced by Streptomyces Cyclic lipopeptide Active against Gram-
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