Microbiology Ch 7

Sepsis = to be contaminated (usually with bacteria or fungi)

Asepsis = absence of contamination

• Sterilize - to completely remove all microbial life (including prions?)
• - - best methods are heat under pressure (autoclave) and sterilizing gas (ethylene oxide)

• Commercial Sterilization - material is heated enough to kill Clostridium botulinum endospores
• - - heat

• Disinfection - distruction of vegitative pathogens (vegitative pathogens (actively growing) - not endospores)
• - - physical or chemical methods

A producer of disease - can be bacteral, viral, fungal, chemical

To physically remove microbes in a limited area - swabbing for injection - uses chemical (alcohol) and physical (rubbling) at the same time - removes microbes (does not kill them)

• Treatment to lower microbial counts on eating utensels to safe public levels
• - - high-temp dishwasher or chemical disinfectant

Antisepsis = to remove pathogens from living tissue

Treatments for death of microbes end in -cide (meaning kill) - biocide, germicide

Treatment to limit the growth of a microbe end in -stat or -stasis -bacteriostasis (limit growth by inhibing protien systhesis)

• Bacteria die at a constant rate of 90%/ min
• 90% die first min
• 90% of remaining 10% die second minute (so on)

1. # of microbes present - ↑microbes = ↓effectiveness

2. Environment - presence of organic matter (nutrients), biofilms, temperature, pH (agents work better if warm and acidic)

3. Time of exposure - ↑ time exposure = works better

4. Type of microbes - Gram (+) bacteria vs. endospore state

1. Damage to cell membrane - affects selective permeability or lipid/ protein damage causes cytoplasm to leak out

2. Damage to intracellular proteins - break bonds and denature proteins - wont work

3. Damage to nucleic acids - no cell growth - lethal

• Moist heat kills by denaturing proteins - called coagulation = breaks H-bonds
• Boiling 10 mins kills most viruses everything except prions and spores

• Dry Heat Sterilization - Dry heat kills by oxidation (breaking chemical bonds)
• 1. Flaming - complete oxidaiton = nothing lives
• 2. Incineration - almost complete oxidation = nothing lives
• 3. Hot-air sterilization - charring - incomplete oxidation
• - 2+ hours - some microbes can live if not in the oven long enough

Moist Heat is more effective - takes lower temperature and shorter time - because the heat is water is more easily transfered to a cool body than the heat in air (hand in 100 degree water vs 100 oven)

TDP = Thermal death point - the lowest temperature at which all microbes are killed in 10 mins

TDT = Thermal death time - the lowest amount of time taken to kill all microbes at a given temperature

DRT = Decimal Reduction Time - time taken to kill 90% of the bacterial population at a given temperature

• Autoclave = preferred method of sterilization - kills by coagulation (denaturation) - breaks H-bonds
• -produces steam under increased pressure - increases temperature of steam = increases effectivness
• 15 psi (121 degrees) x 15 mins = kills everything but prions

• 1. Heat
• - - moist - boil, autoclave
• - - dry - flame, incinerate, hot air (char)
• - - pasteurize - kills pathogens

2. Filtration - removes microbes (0.3 um filter - bacterial = 1 um)

• 3. Cold - lowers metabolism (only inhibits growth)
• - - refrigeration - bacteriostatic (slows spoilage rate)
• - - Deep freeze - H20 expansion = cell disruption still has 30% survival rate
• - - lyophilize - freeze dry under vacuum

4. High atmospheric pressure - denatures proteins/ changes molecular structure of carbs - kills vegitative bacterial (not endospores)

5. Desiccation = remove H20 - microbes become dormant - no effect on endospores

6. Osmotic pressure - plasmolysis (crenation) - high salt, sugar concentraiton (honey & syrup rarely get contaminated)

• 7. Radiation - damages DNA - kills microbe
• - - Ionizing - X-rays, gamma rays, electron beams - ionize molecules (ionize H20 = OH hydroxyl free radical = DNA damage

- - Nonionizing - uv (sunlight) - longer wavelenght -causes thymine dimers = DNA damage

- - Microwaves - kills by heat and boiling - not reliable becuase solid food have an unequal distribution of moisture

pasteurization lowers # of food spoilage microbes and pathgens - times vary by food (fats protect pathogens & need more time)

Equivelent Treatments: - produce the same level of microbial reduction

Classic - mild heating

• HTST - High temp, short time - 72 for 15 secs
• milk, ice cream, yogurt

• UHT - ultra high temp - 140 for < 1sec
• nonrefrigerated milk

• Prions
• Ensospores
• Mycobacteria
• Cysts of protazoa
• Vegitative protazoa
• Gram (-) bacteria
• Fungi & fungal spores
• Viruses w/o envelopes
• Gram (+) bacteria
• Viruses w/ lipid envelopes

• 1. aldehydes
• 2. ethylene oxide

• 1. concentration/ dilution - of disinfectant
• 2. organic matter - present? nutrients, feces, pus
• 3.pH - of disinfectant
• 4. contact - of disinfectant with microbe
• 5. time - gradual process - can take hours

fat soluble → disrupts cell membrane (injures it = cell leaks)

• 1. phenol = LYSOL - - excellent surface disinfactant - persist for long periods after application, stable, remain active in presence of organic compounds
• -can kill mycobacteria
• also throat spray/ losenges - has anesthetic effect as well as antibacterial

• 2. bisphenols - Phisohex (surgical hand scrub)
• - best on Gram (+)
• - no longer used on infants - absorb into skin & cause neuro damage

disrupts cell membrane

• Chlorhexadine - combinded with soap - surgical hand scrub or skin prep for those allergic to iodine
• - mouth wash - kills dental plaque
• - ineffective on endospores, mycobacteria, and most viruses.

• one of most effective - kills almost all microbes including viruses and some endospores
• - alters cell membrane or can enter cell (neutral charge) and hinder protein synthesis

• Iodine (I₂) - oldest and still one of most effective antiseptics
• - Betadine - used for skin disinfection and wound treatment
• - Iodine is also used in alcohol tinctures - tincture of iodine

• Chlorine (Cl₂) - oxidizing agent
• Clorox - NaOCl - sodium hypochlorites - 2 drops/ liter to clean questionable drinking water

• ethanol, isopropanol (rubbing alcohol) 70%
• - lipid membrane disruption
• - protein denaturation (H₂O needed - 70% alcohol most effective)

• - kill bacterial and fungi but not endospores and nonenveloped viruses
• - swabbing = mechanical degerming
• - ineffective on wounds - coagulates proteins - microbes can live beneath this layer
• - increases effectiveness of both with combined with other microbials (tincture)

• Mercury (Hg), Copper (Cu), Zinc (Zn), Silver (Ag), brass (allow of copper or zinc)
• - denature proteins - combine with S on an a.a.

• Oligodynamic = very small amount needed to kill
• 1% silver nitrate - infant eyedrops to kill chlamydia & gonorrhea

• emilsify (break up) oils
• de-germing - mechanical only
• amphipathic molecules - allows fats to be washed away
• soap & detergent are interchanable terms

safe to eat & can kill microbes

1. Organic acids - sorbic acid & benzoic acid - lowers pH - inhibits metabolism - inhibit molds that like acidic environment

• 2. Nitrates - prevents botulism endospore germination
• - sodium nitrate - salt created hypertonic environment
• - turns meat red
• - cancer concern

• 3. Antibiotics
• - restricted by FDA
• - can be used as food preservative - Nisin kills endospores

• Very effective killer/ preservative - can inactivate viruses
• - inactivate proteins by forming covalent crosslinks on a.a.

1. 2% Cidex - Glutaraldehyde - sterilizing agent - used to soak surgical instruments for hours

2. 37% Formalin - Formaldehyde - used for tissue specimin preservation in OR

- both can be used as enbalming agents

• Gas - will kill everything but prions but long exposure time is needed (10 hours)
• - flammable so mixed with CO₂ or N₂ (nonflammable) and applied in a closed chamber
• - Disrupts DNA (breaks covalent bonds) and denatures proteins

- sterilizes without heat or liquid - can be used on instruments that cannot withstand heat or steam exposure (NASA uses on space shuttles)

- mustard gas (WW1) & antifreeze (ethylene glycol) are derivatives of it

oxidizing agents - kills by oxidizing cell parts that shouldnt be oxidized - O₂ toxic in high concentrations

• 1. Ozone (O₃)
• 2. Hydrogen Peroxide (H₂O₂) - ineffective on wounds - breaks down quickly into H₂O and O₂
• 3. Benzoyl peroxide - releases O₂ - anaerobes cant grow

• LPS - lipopolysaccharide on outer cell membrane
• - porins that control what comes into the cell

thick cell wall that contains mycolic acid

Extra thick capsule - most are resistant to chemical disinfectants

most disinfectants are only effective against viruses with lipid envelope - can dissolve envelope and kill virus

Prions are self-replicating proteins - have no genetic material

• not effected by autoclave
• autoclave + NaOH (sodium hydroxide) treatment kinda kills them

• Spongiform encephalopathies - Mad Cow Disease
• CJD - Creutzfeldt- Jakob Disease - very rare - spread by prion-infected surgical instruments