1. CONTROL OF BACTERIAL GROWTH 1. Physical method 2. Chemical method 3. Antimicrobial therapy

2. Physical method 1. Heat in controlling microorganism based on: thermal death point temperature, under given conditions, will certainly destroy all the cells shortest time kills all bacteria except spore form within certain temp.& defined condition thermal death time

3. 1.1 Dry heat material of nature that heat can penetrate readily to all part all bacteria will be destroyhot air oven cannot be used with liquid or organic material temp of 170-180 0 C, one hour, glassware 1.2 Moist heat kill all vegetative bacteria, except spore forms temp.90-100 0 C,10-30 min (boil) 70 0 C 10 min (steam) surgery instruments, dairy equipments

4. 1.3 Steam under pressure complete and rapid destruction of bacterial spores and all microbes temperature is higher than boiling point autoclave : consists of a chamber into which steam may be introduced and maintain under pressure when required temperature is reached, the steam pressure is adjusted to maintain the temperature for require length of time 15 lb/ in, at 121 0 C, 15 min

5. 2. Freezing (cold): delay metabolic activity of microbes freezing and thawing decrease bacterial population bacteria kept frozen in ice, remain alive for a period of time (-40 0 c, -70 0 c)

6. 3. Desiccation (drying) : controlling the growth of all bacterial life by removing of water various species of microbes differ in their ability to survive drying * organism produces endospore more resistant * young actively growing culture of an organism is more readily killed by drying than one which passed through different growth phases vaccine, bacterins, sera

7. 4. Radiation : causes genetic damage ultraviolet light (wave length 240-280 nm) breaks in single and double strands interfering DNA replication * irradiation of air in the hospital * aid in decontamination of lab facilities * can cause skin & eye damage

8. Ionizing radiation greater energy than UV light * causes direct damage * produce toxic free radicals and H 2 O 2 from water within the microbial cells X- ray, beta, alpha & gamma ray (Cobalt-60) * industrial processes, food preserve, medical * sterilize surgical supplies, gloves etc * carry dead but stainable bacteria may produce false-positive Gram stain smear

11. 5. Filtration (live & dead) microbes removed from a liquid by passing the liquid through a filter with pore size that organism cannot enter nature purifies water though the ground used in sterilization of media which may be altered by heat sterilization pore size 0.45 um for common bacteria 0.22 um for virus etc. 0.3 um for HEPA filter

12. Chemical method * cause death of pathogenic vegetative bacterial * protoplasmic poisons 1.Protein denature 1. Alcohol toxic to cell at high concentration ethyl alc. (70-90%) isopropyl (90-95%) are commonly used acts as protein denaturants treatment of infection at superficial lesions

13. 2. Phenol (antiseptic&disinfectant) denature proteinlysol, hexachlorophene strong antibacterial agent usually high concentration (1-2% aqueous sol n ) treating contaminated material 3. Heavy metal ions Mercury, Copper and Silver salt used at very low concentration Mercury combining with protein & may precipitate cell protein eg. Mercurochrome, Merthiolate,1%silver nitrate

14. Halogens (fluorine, chlorine, bromine, iodine, astatine Oxidizing agent inactivating cell by oxidizing essential components of microbial cell iodine - 2% iodine in 50% alc (tincture) skin disinfectant iodophor- used in preparation of skin before surgery 4. Oxidizing agent

15. chlorine - highly oxidizing agent < 1 ppm- kill most vegetative bacteria - inactivate most virus - for drinking water - activity loss quickly in presence of organic matter 5% Sodium hypochlorite - decontaminating of glassware H2O2H2O2

16. 5. Alkylating agent highly lethal to essential all microbes react with protein in the cell and inactivate them sporicidal formaldehyde (37% aqueous sol n formalin) Glutaraldehyde 2% buffer sol n apparatus that cannot be heat treated

17. 6. ethylene oxide gas -replacing labile H atom on hydroxyl carboxyl or sulfhydryl grs esp. guanine and adenine in DNA - sterilizers resemble autoclave 10% ethylene oxide in CO 2 at 50-60 0 C 4-6 hrs. Microbicidal, sporicidal (autoclave) Penetrate packing material, plastic bag

18. Detergents (surface-active compound) compound with hydrophobic and hydrophilic groups attach to solubilize compound or alter their properties (wetting & emulsifier agent) Anionic detergent : soap- highly effective cleanser little antibacterial effect - their charge similar to that of most microbes 2. Injury of cell membrane

19. Cationic detergents : quaternary ammonium compound : benzalkonium chloride 0.1% - highly bactericidal in the absence of contaminating organic matter - react with lipid of cell membrane of bacteria - alter membrane surface properties and its permeability led to loss of essential cell component and death

20. Bacteriostatic having the property of inhibiting bacterial multiplication : multiplication resumes upon removal of the agent Bactericidal * having the property of killing bacteria * action differs from bacteriostatic only in being irreversible * organism can no longer reproduce Sulfonamide, Tetracycline Penicillin, Streptomycin Antimicrobials therapy

21. Mode of Action Prevent cross-linking of peptidoglycan in the cell wall inhibiting cell wall synthesis, creating weak point Gram positive bacteria are more sensitive 1. Inhibition of cell wall synthesis penicillin, cephalosporins

22. cell membrane enclosing the cyloplasm control passage of materials in or out of the cells cellular contents (proteins, nucleotide, ions) can leak from cell cell damage death 2. Damage to cell membrane function if its function is damaged : polymyxin, amphotericin B (topical tr.)

23. act by binding to DNA inhibit its replication or transcription 3. Inhibition of nucleic acid function sulfonamide, nalidixic acid, fluoroquinolone

24. affecting on ribosome 4. Inhibition of protein synthesis antibiotics bind to receptors of subunits of bacterial ribosome and affected a number of different steps in protein synthesis tetracycline aminoglycosides (gentamicin etc.)