micro sheet # 8

بسم الله الرحمن الرحيم

_________________________________________________________________________

for microsoft office 2007 :

http://www.mediafire.com/?amp9v3p7pnvl5ff

for microsoft office 2003 :

http://www.mediafire.com/?q80ah6ir4k27ci7

_________________________________________________________________________



A continue of chemical control of micro-organisms
Halogens
They are: iodine, fluorine, chlorine and bromine
They act by a mechanism called halogenation, they are added as a group to enzymes or proteins and they are effective either alone or as organic compounds.
1) Iodine : it’s available in two forms :

a) Tinctures of iodine : it is prepared in alcohol solution, it’s insoluble in water.
- potassium or sodium iodide alkyls that are solubilised in alcohol

it is active in 2-3% against most organisms where it combines with amino acid tyrosine in proteins and denature them but it leaves stains on the skin and somehow it’s irritating , that’s why it’s been largely replaced by Iodophors
b) Iodophors : they are compounds that release complexes of iodine slowly and they takes several minutes to act and they’re used as skin antiseptics in surgeries (surgical scrub) but they not effective against bacterial spores that’s why they’re just antiseptics
Examples of Iodophors are: Betadine, Isodine, Wescodyne, and Prepodyne.
Iodophors slowly release iodine without being an irritant that’s why they are widely used in hospitals.
2) Chlorine
It is less commonly used in medical practices but it’s more found in households as a disinfectant (bleach)
When it’s mixed with water it forms hypochlorous acid
Cl2 + H2O  H+ + Cl- + HOCl

HOCL is a strong antibacterial agent used to disinfect drinking water by using very low concentrations. It’s also used in pools and in sewage.
It’s easily inactivated by organic material, so in swimming pools that are contaminated by organic materials ( like weeds) chlorine is not efficient .

Another issue is viruses (adeno- virus) that is resistant to chlorine
So if adeno- virus contaminates a swimming pool it leads to the infection of the people that are swimming in that pool and will cause conjunctivitis or pharyngeo-conjunctivitis ( the infection of the pharynx and the eye) and this usually occurs due to contamination by stool.

Sodium hypochlorite (NaOCl) is the active ingredient of bleach

10% bleach is sufficient to kill most pathogenic organisms but not spores (spores are not affected by either chlorine or iodine)

Chloramines: Consist of chlorine and ammonia that are less effective as germicides.

The other halogens (fluorine and bromine) have different applications in medicine; bromine is used as a tranquilizer, but not for the control of microorganisms.

3) Surfactant : it’s an abbreviation for ( surface active agents )
They are active in interfaces (like the folds of skin on the hand) and that’s why they can act on bacteria that are present there.
They possess hydrophobic and hydrophilic groups and they Lower the surface tension and increase miscibility of molecules
There are two classes of surfactant:
a) Soaps: which is composed of sodium or potassium salts and fatty acids, none of these are antibacterial or antiviral, and they act by mechanical degerming of the skin because of the miscibility of organisms (they are washed off by soaps). However there are medicated soaps that contain agents that have antibacterial effect).
b) Detergents: They are superior to soaps because they don’t precipitate water minerals (people who wash their hands with soaps alot they notice a white layer on their skin and that’s because of precipitation of salts and lipids on their hands and this is what causes the allergy of soaps)

Detergents are compounds that are made out of anionic, cationic or quaternary ammonium compounds
Anionic: carboxyl or sulfate groups are the active groups
Cationic: ammonium, phosphorium and sulforium
quaternary ammonium compounds : the ammonium compound is formed of four hydrogen’s and one nitrogen , here the four hydrogen’s are replaced by other groups that are covalently linked to nitrogen , the quaternary ammonium compounds act by inhibiting the normal function of the cell membrane of the bacteria
(Remember we said once that the cell membrane has two antibiotics that act on them the polymexin E and A & detergents
4) Alkylating agents: they Substitute alkyl groups for the hydrogen of reactive groups of enzymes, nucleic acids, and proteins (an alkyl group is: CΞCH) and the most widely used alkylating agent is ethylene oxide. it competes with autoclaves and sterilants in hospitals .

Autoclaves: is steam under pressure

Ethylene oxide is suitable for the sterilization of things that are heat sensitive. It’s Colorless, soluble in water & common organic solvents and it destroys spores however it’s an explosive substance that’s why it’s mixed with CO2 or N2 to avoid that effect.
It’s also a toxic substance and that’s why agents that are treated with ethylene oxide should be air exposed for a while so that the toxicity is removed as gas before using those items (items such clothes, bed linings, operative theater cloths ... etc)
It acts slowly and the action of the ethylene oxide is influenced by humidity, time of exposure, and temperature
That’s why four hours are needed to achieve sterilization at 50-56°C and 6-12 hours at room temperature.
But autoclaves need only 15 minutes to achieve sterilization.
Its optimum humidity is 30%.
- Used to sterilize heat sensitive items.
- Gas must be dissipated before the item can be used (24 hours), if it’s used before 24 hours toxicity can result.
- Exposure time is reduced by 50% for each doubling of concentration of ethylene oxide.
Doubling can carry the risk of explosion and toxicity
- Toxicity likewise the doubles with increase of the temperature by 10°C.
It means when the temperature rises to 66° the time reduces by half (note that we can’t use high temperature for this fearing of toxicity)
BetaPropiolactone: (a gas) is Fumigant and is a Carcinogen and it’s also and explosive substance.

5) aldehydes:
They cross link molecules together and they have been used in sterilization and disinfection for a very long time and they are the most effective antimicrobials.
They inactivate proteins by forming covalent cross links molecules together with several functional groups.
The two most common aldehydes that have been used are: formaldehyde and glutaraldehyde
a) Formaldehyde is mostly used in cadavers ( sustains the integrity of dead bodies )
Formaldehyde gas is an excellent disinfectant.
When Formaldehyde is prepared in aqueous solution (water) it’s called formalin, in a 37% aqueous solution and it’s used in morgues
Formaldehyde when it’s a gas it’s used in fumigation (smoked meat and other types of smoked food) it’s used as a way of disinfecting them
Formalin was used extensively to preserve biological specimens and inactivate viruses and bacteria in vaccines.
It’s an Irritant to the mucous membranes, and has a strong odor also it’s toxic


b) Glutaraldehyde: is less irritating and more effective than formaldehyde.
It is one of the few chemical disinfectants that are sterilizing agent.
a 2% solution of glutaraldehyde (Cidex) is Bactericidal, tuberculocidal, and viricidal in 10 minutes but sporicidal in 3 to 10 hours.
Commonly used to disinfect hospital instruments like GI endoscopes
6) Heavy Metals : they are also substances that can be used and have been used for a long time now

Include copper, selenium, mercury, silver, and zinc.
They have an Oligodynamic action because very low concentration is sufficient to kill organisms


A. Silver:
1% silver nitrate used to protect infants against a condition known as (ophthalmia neonatorum) which is an infection caused by Neisseria gonorrhoeae it can infect the female genital tract without causing any symptom (Asymptomatic infection ) and if the child while passing through the birth canal acquires this infection a severe eye infection develops that could lead to blindness by destroying the eye ball and it’s been discovered the 1% silver nitrate can prevent this case and this is why it was commonly used in hospitals
Nowadays eye drops with antibiotics have replaced this treatment
B. Mercury
Organic mercury compounds like Merthiolate and mercurochrome are used to disinfect skin wounds.
Of course mercury is toxic and that’s why it’s avoided but mercurochrome was very common used to clean wounds.

C. Copper
Copper sulfate is used to kill algae in pools and fish tanks.
D. Selenium: it Kills fungi and their spores. And it’s used as an antifungal
And it’s been used in dandruff shampoos. (Cellsun shampoo has selenium and is very effective.) lately the discovered that dandruff cause is fungal infection not like what was thought before that dandruff is a result of greasy hair ( emidasols are antifungal)
Pityriasis versicolor (which is the brownish discoloration of the skin due to the direct sun contact) is also treated by selenium
E. Zinc
Zinc chloride is used in mouthwashes (antiseptic).
Zinc oxide is used as antifungal agent in paints.
7) Oxidizing Agents
They have antimicrobial effect by oxidizing the cellular components of treated microbes (Cellular proteins). They also become elastemers and that’s why they kill these organisims and they Disrupt membranes proteins.
Examples of oxidizing agents are: ozone and hydrogen peroxide
A. Ozone:
Is highly reactive form of oxygen. Generated by exposing oxygen to electricity or UV light.
Can be used along with chlorine to disinfect water. And helps neutralize unpleasant tastes and odors. It’s more effective killing agent than chlorine, but less stable and more expensive.
B. Hydrogen Peroxide
It has wide application and is s used as an antiseptic and stirilant . And it’s not good for open wounds because it is broken down by catalase present in human cells and will be inactivated and will be changed to water and oxygen that’s why we see bubbles due to the release of oxygen
The active Oxidant is the free hydroxyl radical
Effective in disinfection at the concentration of (3-6%) of inanimate objects but it’s used as a Sporicidal at the concentration of (10-25%) at higher temperatures that’s why we can call it a disinfectant agent.
It’s used by food industry and to disinfect plastic implants, contact lenses, and surgical prostheses.
Plasma Gas: can be generated by Vaporization of H2O2 with the generation of microwave or radiofrequency energy it is a sterilant
C. Benzoyl Peroxide
It’s used in acne medications. Acne is caused by bacteria that are called Propionibacterium acnes.

D. Peracetic Acid
One of the most effective sporicidal liquid available. Generates acetic acid and Oxygen, both of which are nontoxic And is a Sterilant , Kills bacteria and fungi in less than 5 minutes.
Used widely in the disinfection of food and medical instruments because it does not leave toxic residues like ethylene oxide
Kills Endospores and viruses within 30 minutes

8) Chlorhexidine : used commonly in dentistry , it’s an Antiseptic at 4% it’s used for surgical scrub and hand washing. And is found in two examples Hibiclens, Hibitane.
9) Parachlorometaxylenol (PCMX) Active against gram positive bacteria only.
10) Triclosan Active against bacteria. It is a common antiseptic in deodorant soap.

WHAT AND WHEN TO USE ITEMS
(critical items, semi critical items and noncritical items)

1) (critical items should be treated with High-Level disinfectants)
Used for items involved with invasive procedure that cannot withstand sterilization procedures (certain types of endoscopes, surgical instruments with plastic or other components that are destroyed by heat)
The disinfection of these and other items is most effective if treatment is preceded by cleaning of the surface by an agent that removes the organic matter because organic matter interferes with the action of the disinfectant

Examples of high level disinfectants include treatment with moist heat, glutaraldehyde, hydrogen peroxide, peracetic acid, chlorine dioxide, and other chlorine compounds. (Most of these are sterilant rather than disinfectants because they even kill the spores)

2) (Semi-critical items are used for intermediate Level disinfectants)
They include Alcohols, iodophors, and phenolics are used to clean surfaces or instruments in which contamination with bacterial spores and other highly resilient organisms is unlikely (semi critical items).
Examples of items treated include flexible fiberoptic endoscopes (used in the upper GI tract), laryngoscopes, vaginal specula, anesthesia breathing circuits, and others.
Here there are normal flora in these sites there’s no spores there and that’s why we use intermediate items





3) (Non- critical items for Low-Level disinfectants)
They contain Quaternary ammonium compounds are used to treat noncritical instrument and devices such as blood pressure cuffs, ECG electrodes, and stethoscopes.

Although these items come into contact with patients, they do not penetrate through mucosal surfaces or skin so the tissues remain sterile.



The body first deals with infection through non specific mechanisms, if they fail specific mechanisms are used like macrophages, if both fail disease will be established and diagnosis will made according to the clinical manifestations and then microbial antiagents will be given such as antibiotics.



The End
“ Think for yourselves and let others enjoy the privilege to do so too. ”
Voltaire


Thank you all and God bless

Done by : Lana Obeidat
28/9/2010

thanx for posting it
bas it's micro lec. sheet not the sheet for the lab! =)


amma bel nesbeh lal a5ta2 el grammatical .. i'm sorry can u fix them

1) Tinctures of iodine :it is active in 2-3% against most organisms where it combines with amino acid tyrosine in proteins and denatureS them

2) Iodophors : they are compounds that release complexes of iodine slowly and they take

3) Soaps: which are composed of sodium or potassium salts and fatty acids

4) Ethylene oxide is suitable for the sterilization of things that are heat sensitive. It’s Colorless, soluble in water & common organic solvent
5) Toxicity likewise it doubles with the increase of temperature by 10°C.

6)Acne is caused by bacteria that is called Propionibacterium acnes.

7) if both fail disease will be established and diagnosis will be made according to the clinical manifestations


<< i ddnt have the time to correct the sheet yesterday and also i have the flu so ma ely da5al! :P :) anyway if u could please correct those mistakes i'd be greatful! :) >>
thanx!

tc[b]

إنت لو عدلتيهم على السوفت كبي إلي عندك ورفعتيها مرة تانية كان أسهل وأحسن .. على كل سيتم التعديل .. بس أنا هلأ نعسان شوي .. سامحينا