antibiotic actionW13s

16 madigan et al 12th ed fig 2017 11th ed antib8

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Unformatted text preview: g of growth factors -interferes with metabolism -anti-metabolites -when bacterium is try to metabolism folic acid, it will insert the sulfa drug -folic acid is important in making purines (Fig 27.16 Madigan et al, 12th ed: Fig 20.17, 11th ed) antib8 precursors of purines: inosinic acid = precursor of purine nucleotides sulfa drugs: broad spectrum growth factor analogs (Fig 5.27, Madigan et al. 12th , Fig. 5.28, 11th ed) antib8a (ii) isoniazid: •  very narrow spectrum growth factor analog - of the vitamin nicotinamide •  works against Mycobacterium tuberculosis •  inhibits mycolic acid synthesis (component of mycobacterial cell wall) → control and treatment of tuberculosis (Fig 34.11, Madigan et al., 12th ed; Fig 26.9, 11th ed) antib9 (iii) quinolones, fluoroquinolones: •  all possess 4-quinolone ring •  affect bacterial DNA gyrase (topoisomerase II) activity, topoisomerase IV activity •  DNA supercoiling impaired → disrupts replication, repair, transcription, bacterial chromosome separation during cell division •  nalidixic acid = prototype •  effective against gram positive and gram negative bacteria •  human urinary tract infections, STIs (Chlamydia, N. gonorrhoeae), respiratory tract infections •  beef, poultry industries – prevention of respiratory tract diseases ciprofloxacin: a fluoroquinolone •  drug of choice against penicillinresistant Bacillus anthracis (Fig 27.18, Madigan et al., 12th ed; Fig 20.19, 11th ed) antib10 examples of antibiotics: β-lactams: penicillins, cephalosporins •  secondary metabolites of fungi (Penicillium chrysogenum; Cephalosporium sp.) •  all possess β-lactam ring (appears essential for activity) •  inhibit bacterial cell wall synthesis (transpeptidation) penicillin: •  penicillins differ at “R” group •  substitution to produce semisynthetic penicillins (Fig 27.19 Madigan et al 12th ed ; Fig. 20.20) 11th ed) •  natural penicillin (penicillin G) affects gram positives •  ampicillin (semisynthetic) also affects some gram negatives; resistant to βlactamase penicillin r...
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