Chemical Methods of Control: Health Care Conditions in the 1800s

1. MICROBIOLOGY – ALCAMO LECTURE: Chemical Methods of Control

2. Health Care Conditions in the1800’s • Hospitals rarely had running water • Garbage and human waste were dumped in a pit right outside • Surgeons wiped their hands and instruments on their jackets and pants • Bed sheets were rarely changed and infection was rampant • 1/3 of women giving birth died of puerperal fever – blood disease caused by Streptococcus

3. Health Care Conditions in the1800’s • A Hungarian doctor – Ignaz Semmelweis – noticed: • More puerperal fever in maternity wards tended by doctors fresh from dissecting cadavers • Less puerperal fever in maternity wards tended by midwives • He thought disease was spread by infected hands and made hospital workers wash their hands • This reduced the death rate among maternity patients significantly

4. Health Care Conditions in the1800’s • Other doctors rejected Semmelweis’s conclusions because it put the blame on them • After he died, Pasteur came out with the germ theory of disease • Doctors began to finally realize that infectious MO’s could be transmitted by clothing, utensils and instruments • They began using chemical antiseptics and disinfectants and the death toll declined

5. Health Care Conditions in the1800’s • In the 1860’s Joseph Lister established the principles of aseptic surgery • He used carbolic acid to kill MO’s in operating rooms • Reduced the death rate post-surgery from 45% to 9%

6. Lister Video • http://www.mefeedia.com/news/29703360

7. Chemical Agents of Control – Terms To Know • Most chemical agents can only reduce the # of MO. Sterility is unusual. • Two Categories: • Antiseptics: Use on living tissues - mild or very diluted chemicals • Disinfectants: Use on objects – strong or concentrated chemicals

8. Chemical Agents of Control - Terms To Know • Bactericidal Agent – kills MO’s • Bacteriostatic Agent – temporarily prevents further multiplication of MO’s without killing them • Sepsis (putrid) – contamination of an object by MO’s: • Septicemia – MO infection of the blood • Antiseptic – against infection • Aseptic – free of contaminating MO’s

9. Chemical Agents of ControlTerms To Know • Sanitize – to reduce the MO population to a safe level determined by public health standards • Degerm – to remove MO’s from the surface • - cidal agents – kill Mo’s: • Fungicide • Virucide • Sporicide

10. What Makes a Good Disinfectant • It must kill MO’s • Be nontoxic to humans and animals • Be soluble in water • Get its job done in a short time • Should penetrate surfaces well • Should not corrode instruments • Should be inexpensive and easy to obtain

11. Important Chemical Agents - Halogens • Halogens are highly reactive elements whose atom have 7 electrons in their outer shell • Chlorine and Iodine – Very Reactive • Cause Cell Death by Oxidation – • Oxygen is released and then combines with and inactivates proteins (enzymes)

12. Important Chemical Agents - Halogens • Chlorine • Disinfectant that can be used alone as gas or in a solution with water • Used in municipal water supplies to keep bacterial populations low • 6 – 10 Drops/Gal Clear Water/1 hour = Drink • Available as calcium hypochlorite – used for wounds in WWI and WWII

13. Important Chemical Agents - Halogens • Available as sodium hypochlorite – bleach to disinfect water (swimming pools) and sanitize factory equipment • Laundry bleach most available and excellent means of MO control • Do not combine bleach with other chemicals - small but lethal amounts of Cl gas may be released!!!!

14. Important Chemical Agents - Halogens • Chlorine is effective against • Gram-positive and Gram-negative bacteria • Many viruses • Fungi • Protozoa • Not effective against spores

16. Important Chemical Agents - Halogens Iodine • Usually an antiseptic • 2% in water or alcohol (Tincture) good for wounds • If solvent evaporates tissue damage • For water disinfection use 18 – 20 Drops/Gal Clear Water/1 hour = Drink • Iodifors – iodine mixed with detergent • Betadyne – for local wounds

18. Important Chemical Agents - Phenol • Has been a key disinfectant since Joseph Lister used it • Remains the standard against which other disinfectants are evaluated • It acts by coagulating proteins in the cell membranes of MO’s • But, it is expensive, has a strong odor, and is caustic to the skin

19. Important Chemical Agents - Alcohol • Either antiseptic or disinfectant • 70% Ethyl alcohol preferred • Causes denaturation and desiccation • But requires long exposure, limited effect

20. Important Chemical Agents - Heavy Metals • Metal elements with a large molecular weight: • Silver, Mercury, Copper, Lead, Zinc • Can be used as either an antiseptic or a medicine • Cause denaturation of proteins (enzymes) • Can be very toxic to host

21. Important Chemical Agents - Heavy Metals • Mercury: • Mercuric chloride was used by the Greeks and Romans for treating skin diseases • Mercury is very toxic to the host, so it is now combined with carrier molecules to make it less toxic • Mercurochrome • Merthiolate • Metaphen

22. Important Chemical Agents - Heavy Metals • Copper: • Potent inhibitor of algae • Copper sulfate is an algaecide used in swimming pools and municipal water supplies

23. Important Chemical Agents - Heavy Metals • Silver: • Silver Nitrate – useful antiseptic and disinfectant • If it is a strong dilution – used for chemical cautery • If it is a weak dilution – used in a newborn’s eyes to prevent bacterial infection by Neisseria gonorrhoeae • Zinc: Calamine Lotion (antiseptic, anti-itch) • Bismuth: Pepto Bismol (anti-diarrheal)

24. Important Chemical Agents Hydrogen Peroxide • Antiseptic and disinfectant – used as a rinse in wounds and scrapes • Area foams as catalase in tissues breaks down H2O2 to oxygen and water • This results in a highly reactive form of oxygen – toxic to MO’s

25. Important Chemical Agents - Soap • Soap is made of fatty acids combined with sodium hydroxide – high pH bad for certain MO’s • Soap is also a wetting agent that solubilizes particles clinging to a surface • Soap also removes skin oils and MO’s slide off skin

26. Soaps Video • http://www.google.com/url?sa=t&source=video&cd=9&sqi=2&ved=0CH8QtwIwCA&url=http%3A%2F%2Fvideo.google.com%2Fvideoplay%3Fdocid%3D-3210455528645505714&rct=j&q=chemical%20disinfection&ei=gXSjTc-QPMi-0QGAlaDQBA&usg=AFQjCNH14lMibDqfMas5Nz5ZNV34-Y9njg&cad=rja

27. Important Chemical Agents - Ethylene Oxide • A small compound with excellent penetration capacity and sporicidal ability due to oxidation • Very Dangerous – toxic and explosive • Used in production of sterile supplies and by NASA to sterilize space capsules

28. Ethylene Oxide Video • http://www.youtube.com/watch?v=-ICBQg9tcT8