Lecture 4:- Control Of Microorganism
- 1. Microbiology Lecture 4:- Control Of Microorganism Dr. Raghda Saad Mohammed
- 2. Sterilization : is process of killing or removing all of viable organisms. Disinfection : is process of kill or removing must but not all viable organisms. Antiseptic : it means prevent of infection by inhibiting growth of bacteria. Bactericidal agents : they are those which able to kill bacteria. Bacteriostatic agents : only prevent multiplication of bacteria and they remain alive. Various agents used is sterilization are: • 1-physical method • 2-chemical method Sterilization and disinfection
- 3. 1-Sun light 2- drying 3- heat 4- filtration 5-radiation 1-Sun light : it bactericidal activity. the action is due to ultraviolet ray. 2-Drying : drying in air has effect on many bacteria. 3-heat : the factors influencing sterilization by heat are : a-Nature of heat b-Temperature and time c-Number of organisms d-Whether organism has spore capacity Type of heat 1-Dry heat A-Red heat: it is used to sterilize metallic objects by holding them in a flam till they are red hot ex Wire loop , needles scalpels forceps, etc. B-Flaming: the article is passed over flam without allowing it to become red hot e.g. culture tubes, glass, slides Sterilization and disinfection
- 4. C- Hot air oven: requires temp- of 160 c for one hour - we can sterilize all glass, syringes , petri-dishes , test tubes flask , scissors etc 2- Moist heat: the lethal effect is by denaturation and coagulation of protein A- Temp. below 1000C Pasteurization of milk :temp. employed is either : 63C for 30 mints holder method or: 72 C for 15-20 second flash method Mycobacterium , Salmonella , Brucella are killed B- Temp. at 100C. 1-Tantalization: this is process by which medium is placed at 100c inflowing steam for 30 min. each on 3 successive days. 2- Boiling : most of vegetation from bacteria , fungi and are killed 50-70 C in short time for needles and instruments boiling in water for 10-30 min , is sufficient to Sterilization. 3- Steam under pressure : autoclave is used for bacteriological and surgical work because of spores kills all microorganisms including (HIV & hepatitis virus). Sterilization and disinfection
- 5. Filtration ;- Is the method of sterilization, used filter paper useful for antibiotic solutions , sera , etc. Ex: Asbestos disc filter , membranous filter Radiation Ultraviolet radiations : it is chief bactericidal factor present in sun light , it cause following changes in cell 1. denaturation of protein 2. damage to DNA 3. inhibition of DNA replication 4. formation of H2O2 and organic peroxide in medium B-Chemical methods: 1- Acid and alkaline: growth bacteria inhibition Mycobacterium is more resistant to acid than alkaline 2-Halogens: iodine is used chiefly for skin. combines with water to from hydrochloric acid which is Bactericidal. 3 -Formaldehyde: useful in ster. Bacterial vaccine and in inactivating bacterial toxin without affecting their antigenicity (5-10%) solution in water kills many bacteria. It is Bactericidal, sporicidal and lethal to viruses also. Sterilization and disinfection
- 6. 4- Dry : gentian and malachite green etc. are active against gram positive bacteria. 5- Soap and detergents: they are Bactericidal and bacteriostatic for gram positive bacteria and some acid fast organisms. 6-Aerosol and gaseous disinfectants S02 : chlorine and formalin vapor have been used as gaseous disinfectant . Propylene, glycol is powerful disinfectant Sterilization and disinfection
- 7. Infection Infection The lodgment and multiplication of organism in the tissue of the host. Classification of infection 1. Primary infection : - Initial infection with organism in the host . 2. Reinfection : - Subsequent infection by the same organism in the host. 3. Secondary infection : - In the host whose resistance is lowered by preexisting infection disease , anew organism may set up as infection . 4. Focal infection : - It is a condition due to infection at localized sites like appendix and tonsil . 5. Cross infection : - The patient suffering from a disease and new infection is set up from another host or from external source . 6..Nosocomial infection : - Cross infection occurring in hospital . 7.Subclinical infection : - When a patient clinical affects are not apparent .
- 8. Source of infection 1. Human : - is himself a common source of infection from a patient or1.carrier . 2. Animals : - Infectious diseases transmitted from animals to human are called zoonosis may be bacterial (e.g. plague from rat ), viral ( e.g. rabies from dogs ) , protozoa (e,g leishmaniasis from dogs ), helminthes (e.g. hydatid cyst from dogs ), fungal from cats and dogs . 3. Insects : - The disease caused by insects are called arthropod borne disease .Insects like mosquitoes , flees ,lice that transmit infection are called vector. Transmission may be mechanical (transmission of dysentery or typhoid bacilli by house fly) these are called mechanical vector. They are called biological vector if pathogens multiplies in the body of vector e.g. Anopheles mosquito in malaria. 4. Some vector may act as reservoir host(e.g. ticks in relapsing fever and spotted fever). 5. Soil : - Soil may be serve as some of parasitic infection like round worm and hook worm. Spores of tetanus bacilli remain viable in soil for a long time. 6. Water : - Vibrio cholera , infective hepatitis virus . 7. Food :- Contaminated food may be source of infection.(food poisoning by staphylococcus).
- 9. Methods of transmission of infection 1. Contact : - Syphilis , gonorrhea , trachoma . 2. Inhalation : - Influenza , tuberculosis , small pox , measles and mumps . 3. Infection : - Cholera (water) food poisoning (food) dysentery (handborne) . 4. Inoculation : - Tetanus , (infection) rabies (dog), arbovirus (insects) , serum hepatitis (injection) . 5. Insects : - Act as mechanical vector (dysentery and typhoid by house fly) or biological vector (malaria) of infectious disease . 6. Congenital : - Congenital syphilis , Toxoplasma . 7. Laboratory infection : - Infection may be transmitted during procedure like injection , catheterization.
- 10. Respiratory system infection Lower respiratory tract infection (Consist of three types) • 1. Trachea • 2. Bronchiole • 3. Lung • Upper respiratory tract infection Sputum (Consist of types): • 1. Tonsillitis. • 2. Throat. • 3. Nose.4. • Nose sinuses • 5. Larynx
- 11. • It is mucous that is coughed up from the lower airways .In medicine, sputum samples are usually used for microbiological investigation of respiratory tract Culture media which used : • 1. MacConkey agar. • 2. Blood agar. • Types of bacteria which cause respiratory tract infection: • 1. Staphylococcus. • 2. Streptococcus. • 3. Corynobacteria. • 4. Neisseria. • 5. Pneumonia. • 6. Haemophillus.