The Ionizing and Electromagnetic Spectrum of Energies Fig. 5.7
Physical Control - radiation• Radiation damages DNA• UV radiation (ultraviolet light) – UV lamps for disinfection – Causes T-T dimers – Cell death – What happens in humans?
Mutations block DNA processes• TT dimer distorts DNA• No replication• No transcription• High dose = death
Physical Control - radiation• Ionizing radiation (solar rays, radioactive) – 10K times more energy than UV – ionization of water (OH- & H3O+ ) – DNA breaks apart – Sterilize plastics, food, destroy viruses (Ebola) – What happens to humans exposed to IR? • Acute exposure - • Chronic exposure - • How do we know this???
Physical Control - desiccation• All living things need water• Dry out grains, meat, fish to preserve
Disinfectants/Antiseptics• Ancient Egypt - chemicals for embalming• 1800’s - Iodine used in medicine• Joseph Lister - 1860’s – Read Pasteur – soaked instruments in phenol – Knighted in 1912
Antimicrobial Chemotherapy• Antibiotic control
Pre-antibiotic era• Medicine was a gruesome business• Civil war - more than 2/3 of all deaths due to disease, not wounds• Paul Erlich - early 1900s – Arsenic compounds as syphilis treatment – Fell out of favor b/c toxic
Sulfanilamide - sulfa drugs• 1932 - “prontosil” developed by Gerhard Domagk• Effective in treating Gram-positive bacterial infections• Gave push to development of newer & better antibiotics Bacteria need This PABA to make looks like folic acid PABA
Development of penicillin• Alexander Fleming• 1929 - Penicillium mold prevented S. aureus growth• Extract killed Gram-positive bacteria• 1939 - Florey & Chain• Mass produced in USA
Penicillin & derivatives• One of the most widely used antibiotics• Best against Gram-pos; some Gram-neg (gonorrhea)• ~ 10% of population allergic• Works on rapidly dividing cells – No effect on endospores!
Penicillin Resistance• Many bacterial species have developed resistance• MRSA - methicillin resistant Staph. aureus
Streptomyces - natural antibiotic R&DSoil bacterium - lots of genes for making antibiotic compounds• Aminoglycoside (streptomycin, gentamycin) – Good if allergic to penicillin – Inhibits protein synthesis – Erythromycin: Zithromax, Biaxin – Vancomycin - last resort for MDR Gram-pos
Broad Spectrum antibiotics• Selective Toxicity• Chloramphenicol first one isolated – Effective against Gram-pos &neg, chlamydiae, some fungi – Nasty side effects - hemolytic (last resort)• Tetracycline – Very few side effects (short term) - overprescribed – Yeast infections common – Discoloration of teeth/stunted bones in children
Antibiotic Resistance• Emerging danger• Natural selection of resistant strains thru overuse – Overprescibing meds – Used in livestock feed
• Take entire course of prescription• Do not take higher dose of samemed if no improvement• Do not take antibiotics for viralinfection
Antifungal meds• Fungal infections big problem for immune suppressed individuals• Antifungals - not many choices – Nystatin, miconazole - interfere w/sterols (cell membrane) – Amphotericin B - used for serious internal organ infection – Griseofulvin - ringworm treatment
Antiviral meds - not antibiotics• Antivirals target different stages of viral replication – amantadine - prevents attachment – acyclovir - interferes w/viral DNA replication