Antibiotics: Microbiology 4 - Antibiotics Chemical compounds used to treat infections caused by bacteria Not toxic enough to kill the patient Can be used to supplement the body's natural defence Classification of antibiotics - Natural antibiotics (true antibiotics) o Produced naturally by fungi or bacteria e.g. penicillin - Semi-synthetic antibodies o Chemically modified natural antibiotics e.g. ampicillin - Totally synthetic antibodies o Manufactured e.g. trimethoprim Clustering the antibiotics into four major mechanisms of action: - Cell wall antibiotics o Destroying or damaging or preventing the synthesis of the cell wall o E.g. B-lactams - Nucleic acid inhibiters o Inhibit DNA or RNA synthesis - Protein antibiotics o Inhibit protein synthesis - Metabolism antibiotics o Impact metabolism o E.g. Foelic acid inhibitors Cell Wall Inhibitors - B-lactam Antibiotics - - e.g. penicillin nucleus is made up of the b-lactam Go over this - combined with a thiazolidine ring using last - Penicillin G (natural one) o Could change it to a more acid stable Penicillin V Still a natural product - Amoxicillin Dorothy Hodgkin's was able to o Semi-synthetic (Chemically modified see the structure of these molecules O Longer half-life - Worked out the structure o Lower toxicity at higher concentratio - Methicillin o Semi-synthetic - Usage: f d o URTI (e.g. tonsillitis) o LRTI (e.g. pneumonia) o STI (e.g. gonorrhoea, syphilis) o Skin and tissue infections - Most predominantly class of antibiotics in the world o 52% o Then 25% for fluroquilaromes - B-lactam antibiotics:
- 10000 metric tons of antibiotics are administered every year o Cephahalosporins (30%) - second generations o Penicillins (7%) History of Antibiotics DIFFERENT CLASSES OF ANTIBIOTICS - AN OVERVIEW Key: COMMONLY ACT AS BACTERIOSTATIC AGENTS, RESTRICTING GROWTH & REPRODUCTION COMMONLY ACT AS BACTERICIDAL AGENTS, CAUSING BACTERIAL CELL DEATH D-LACTAMS AMINOGLYCOSIDES FAMILY OF OVER 20 ANTIBIOTICS MOST WIDELY USED ANTIBIOTICS IN THE NHS R OH Al contain o toto-loctoi ring EXAMPLES Penichins (shown) such as amontdllin and ficiconcillin: Cephalosporins such as cetalexin NODE OF ACTION inhibit banersa cos wall biosynthesis. EXAMPLES Streptomyon (shown), neamycin canarytin, paramomydin. MODE OF ACTION Inhibit the synthesis of proteins by bacteria, leading to cell death, DISCOVERY 1930 CHLORAMPHENICOL COMMONLY URD IN LOW INCOME COUNTRIES 0.3 Distinct inididdio compound MODE OF ACTION Inhibit synthesis of proteins, preventing growth. No longer a fiat line chag in any developed nation due to increased wsistance and worries about safety. 1940 1950 GLYCOPEPTIDES COMMON DRUGS OF LAST RESORT peptide formed af aminoacids EXAMPLES Vencerinyrin (shown] teiroplanin. MODE OF ACTION Inbiber bacteria cell wall bicsynthesk. ANSAMYCINS CAN ALSO DEMONSTRATE ANTIVIRAL ACTIVITY on alphetic dyn EXAMPLES Geklznanych ??h?cen), rifamycin, MODE OF ACTION Inhibit the synthesis of RNA by bacteria, leading to cel death. 1960 1970 STREPTOGRAMINS TWO GROUPS OF ANTIBIOTICS THAT ACT SYNERGISTICALLY Combination of ows structural differing EXAMPLES Pristinamyon 34(shown). Pristinomycin IA. MODE OF ACTION Inhibit the synthesis of proteins by bacteria; leading to col death. 1980 SULFONAMIDES TETRACYCLINES FIRST COMMERCIAL ANTIBIOTICS WERE SULFONAMIDES BECOMING LESS POPULAR DUE TO DEVELOPMENT OF RESISTANCE H,N- MACROLIDES SECOND MOST PRESCRIBED