MICROBIOLOGY – ALCAMO

LECTURE:

Chemical Methods of Control

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

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

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

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%

Lister Video

• http://www.mefeedia.com/news/29703360

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

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

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

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

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 inactivatesproteins (enzymes)

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

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!!!!

Important Chemical Agents - Halogens

• Chlorine is effective against– Gram-positive and

Gram-negative bacteria–Many viruses– Fungi– Protozoa

• Not effective against

spores

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

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

Important Chemical Agents - Alcohol

• Either antiseptic or disinfectant

• 70% Ethyl alcohol preferred

• Causes denaturation and desiccation

• But requires long exposure, limited effect

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

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

Important Chemical Agents - Heavy Metals

• Copper:– Potent inhibitor of algae– Copper sulfate is an algaecide used in

swimming pools and municipal water supplies

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)

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

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

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

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

Ethylene Oxide Video

• http://www.youtube.com/watch?v=-ICBQg9tcT8