Controlling microbial growth in the environment Flashcards

Question

Give an example of sterilization

Answer 1

Preparation of microbial culture media & canned food

Answer 2

Typically by steam under pressure, incineration, or ethylene oxide gas

Answer 3

– High—kill all pathogens, including endospores. Health care professionals use this to sterilize invasive instruments (catheters, implants, parts of heart lung machine) – Intermediate—kill fungal spores, protozoan cysts, viruses, pathogenic bacteria. Not endospores. Used to disinfect instruments that come in contact w/mucous membranes but non invasive (respiratory instrument, endoscopes) – Low—kill vegetative bacteria, fungi, protozoa, some viruses; used to disinfect items only contact skin (furniture, electrodes)

Answer 4

– High—kill all pathogens, including endospores – Intermediate—kill fungal spores, protozoan cysts, viruses, pathogenic bacteria – Low—kill vegetative bacteria, fungi, protozoa, some viruses

Answer 5

A phospholipid envelope is typically more fragile than a protein capsid

Answer 6

``` Most resistant 1) Prions 2) Bacterial endospores 3) Mycobacteria 4) Cysts of protozoa 5) Active-stage protozoa (trophozoites) 6) Most Gram-negative bacteria 7) Fungi 8) Nonenveloped viruses 9) Most Gram-positive bacteria 10) Enveloped viruses Most susceptible ```

Answer 7

– Denature proteins – Interfere with integrity of cytoplasmic membrane and cell wall – Disrupt structure and function of nucleic acids

Answer 8

– Used to disinfect, sanitize, and sterilize – Denatures proteins and destroys cytoplasmic membranes – More effective than dry heat – Methods of microbial control using moist heat: * Boiling * Autoclaving * Pasteurization * Ultrahigh-temperature sterilization

Answer 9

– Kills vegetative cells of bacteria and fungi, protozoan trophozoites, most viruses – Boiling time is critical: Different elevations require different boiling times – Endospores, protozoan cysts, and some viruses can survive boiling

Answer 10

– Pressure applied to boiling water prevents steamfrom escaping – Boiling temperature increases as pressure increases – Autoclave conditions – 121oC, 15 psi, 15 min

Answer 11

– Used for milk, ice cream, yogurt, and fruit juices – Not sterilization: Heat-tolerant microbes survive – Pasteurization of milk – Batch method – Flash pasteurization – Ultra high-temperature pasteurization

Answer 12

– Used for materials that cannot be sterilized with moist heat – Denatures proteins and oxidizes metabolic and structural chemicals – Requires higher temperatures for longer time than moist heat – Incineration is ultimate means of sterilization

Answer 13

– Decrease microbial metabolism, growth, and reproduction – Chemical reactions occur more slowly at low temperatures – Liquid water not available – Psychrophilic microbes can multiply in refrigerated foods – Refrigeration halts growth of most pathogens – Slow freezing more effective than quick freezing – Organisms vary in susceptibility to freezing

Answer 14

– High concentrations of salt or sugar in foods to inhibit growth – Cells in hypertonic solution of salt or sugar lose water – Fungi have greater ability than bacteria to survive hypertonic environments

Answer 15

– Drying inhibits growth because of removal of water – Lyophilization used for long-term preservation of microbial cultures – Prevents formation of damaging ice crystals

Answer 16

– High concentrations of salt or sugar in foods to inhibit growth – Cells in hypertonic solution of salt or sugar lose water – Fungi have greater ability than bacteria to survive hypertonic environments

Answer 17

– Wavelengths shorter than 1 nm – Ejects electrons from atoms to create ions – Ions disrupt hydrogen bonding, oxidize double covalent bonds, and create hydroxide ions – Hydroxide ions denature other molecules (DNA) – Electron beams – effective at killing but do not penetrate well – Gamma rays – penetrate well but require hours to kill microbes

Answer 18

– Wavelengths greater than 1 nm – Excites electrons, causing them to make new covalent bonds – Affects 3-D structure of proteins and nucleic acids – UV light causes pyrimidine dimers in DNA – UV light does not penetrate well – Suitable for disinfecting air, transparent fluids, and surfaces of objects

Answer 19

– Intermediate- to low-level disinfectants – Denature proteins and disrupt cell membranes – Effective in presence of organic matter – Remain active for prolonged time – Commonly used in health care settings, labs, and homes – Have disagreeable odor and possible side effects

Answer 20

– Intermediate-level disinfectants – Denature proteins and disrupt cytoplasmic membranes – More effective than soap in removing bacteria from hands – Swabbing of skin with 70% ethanol prior to injection

Answer 21

– Intermediate-level antimicrobial chemicals – Believed to damage enzymes via oxidation or by denaturation – Widely used in numerous applications – Iodine tablets, iodophores, chlorine treatment, bleach, chloramines, and bromine disinfection

Answer 22

– Peroxides, ozone, and peracetic acid – Kill by oxidation of microbial enzymes – High-level disinfectants and antiseptics – Hydrogen peroxide can disinfect and sterilize surfaces – Not useful for treating open wounds because of catalase activity – Ozone treatment of drinking water – Peracetic acid is effective sporocide used to sterilize equipment

Answer 23

– “Surface active” chemicals – Reduce surface tension of solvents – Soaps and detergents – Soaps have hydrophilic and hydrophobic ends – Good degerming agents but not antimicrobial – Detergents are positively charged organic surfactants – Quats – Low-level disinfectants – Ideal for many medical and industrial applications

Answer 24

– Heavy-metal ions denature proteins – Low-level bacteriostatic and fungistatic agents – 1% silver nitrate to prevent blindness caused by N. gonorrhoeae – Thimerosal used to preserve vaccines – Copper controls algal growth

Answer 25

– Compounds containing terminal –CHO groups – Cross-link functional groups to denature proteins and inactivate nucleic acids – Glutaraldehyde disinfects and sterilizes – Formalin used in embalming and disinfection of rooms and instruments

Answer 26

``` – Microbicidal and sporicidal gases used in closed chambers to sterilize items – Denature proteins and DNA by cross-linking functional groups – Used in hospitals and dental offices – Disadvantages * Can be hazardous to people * Often highly explosive * Extremely poisonous * Potentially carcinogenic ```

Answer 27

– Site to be treated – Harsh chemicals and extreme heat cannot be used on humans, animals, and fragile objects – Microbial control based on site of medical procedure – Temperature –pH – Residual organic matter

Answer 28

– Inexpensive – Fast-acting – Stable during storage – Capable of controlling microbial growth while being harmless to humans, animals, and objects Such ideal products & procedures do not exist- every agent has limitations & disadvantages

Answer 29

– Damage to proteins and nucleic acids – Protein function depends on 3-D shape – Extreme heat or certain chemicals denature proteins – Chemicals, radiation, and heat can alter/destroy nucleic acids – Produce fatal mutants – Halt protein synthesis through action on RNA

Answer 30

– Alteration of cell walls and membranes – Cell wall maintains integrity of cell – When damaged, cells burst because of osmotic effects – Cytoplasmic membrane controls passage of chemicals into and out of cell – When damaged, cellular contents leak out – Nonenveloped viruses more tolerant of harsh conditions

Answer 31

1) The nature of the sites to be treated 2) The degree of susceptibility of the microbes involved 3) The environmental conditions that pertain

Answer 32

medical instruments that penetrate outer defenses of the body (needles, scalpels) carry great potential for infection, so they must be sterilized. Disinfection may be used for items that mucous membrane surface contact surface or skin. In the latter case, sterilization is required for immunocompromised

Answer 33

Non-enveloped viruses (poliovirus) because envelops are more easily disrupted than the protein coats of non enveloped

Answer 34

Environmental extremes of temp. & acidity & withstand many chemical disinfectants. They can survive more than 20 yrs in 70% alcohol

Answer 35

Survive drying and protects from most water-based chemicals. Must use strong disinfectants or heat to treat whatever comes into contact with TB patients including utensils, equipment and patients room

Answer 36

Entry of most disinfectants, protects against drying, and shields against radiation & heat