抗生素与细胞膜（英文PPT）Antibiotics and cell envelopePPT.pptVIP

* Polymyxin B binds lipid A phospholipids disrupts outer membrane, Gram negative bacteria toxic to human cells Daptomycin * Causes depolarization of bacterial cell membrane * Isoniazid and Ethionamide - chemically related - blocks mycolic acid synthesis Ethambutol blocks arabinogalactan synthesis Cycloserine Anti-tuberculosis drugs * * * * * * * * * * * * * * * * * * * * * * * * * Dr. Alvin Fox Antibiotics: cell envelope,Lecture 36 * Key Words Sterilization/disinfection/antisepsis Beta lactam Antibiotic Penicillins Selective toxicity Cephalosporins/cephamycins Bactericidal Monobactam Bacteriostatic Clavulinic acid Minimal inhibitory concentration (MIC) Penicillinase/beta lactamase Susceptibility testing Polymyxin B Penicillin binding proteins Daptomycin Autolysins Isoniazid Cycloserine Ethioniamide Bacitracin Ethambutol Vancomycin Resistance * STERILIZATION All killed non-selective * Sterilization autoclaving 121oC (heat/pressure) Heat resistant materials ethylene oxide non heat resistant Usually equipment being replaced e.g. H2O2/free radicals ultra-violet light surfaces (e.g. operating rooms) not totally effective gamma radiation mainly food industry * Membrane filters pores bacteria * Antiseptics Topical (e.g. skin) e.g. iodine or 70% alcohol “reduce” bacterial load * ANTIBIOTICS Selectively toxic for bacteria bactericidal (killing) bacteriostatic (growth inhibition) minimize harm to patient * Antibiotics destroy structures present in bacteria not present in host * Antibiotics work together with the immune system * Minimal inhibitory concentration lowest level stopping growth e. g. zone of inhibition around a disk impregnated with antibiotic * Antibiotics that inhibit cell wall biosynthesis are bactericidal Without cell wall, osmotic pressure causes bacteri