microbial growth Flashcards Preview

MicroB Lecture > microbial growth > Flashcards

Flashcards in microbial growth Deck (27)
Loading flashcards...
1


Asepsis vs sepsis

asepsis: absence of significant contamination

 

sepsis: microbial contamination

2

Sterilization

 

Commerical sterilization

 

Disinfection

 

Antisepsis

Removal of all microbial life

 

Kills C. Botulinum endospores

 

removal of pathogen

 

removal of pathogens from living tissue

3

Degerming

 

Sanitization

 

Biocide/Germicide

 

Bacteriostasis

Removal of microbes from a limited area

 

Lowering the number of micrbial counts on utensils

 

Kills microbes

 

Inhibits microbes (does not kill)

4


Microbial control Agent

Alters membrane permeability

 

damages proteins

 

damages nucleic acids

 

5


Heat

 

TDP vs TDT


Kills by denaturing enzymes

 

TDP (Thermal death point): lowest temperature in which all cell culture will be killed within 10 min

 

TDT (Thermal death time):  The time it takes the cell culture to die at a specific temperature

6


Autoclave

121C at 15 psi

 

moist/heat denatures proteins

7


Pasteurization


Reduces spoilage organisms and pathogens

 

Treatment:  63C for 30 minutes

High Temp for short time:  72C for 15 sec

ultra High temp:  140C for 1 sec

 

Except: thermoduric organisms. wil survive

8

Dry Heat Sterilization


Kills by oxidation

 

  • dry heat
  • flaming
  • incineration
  • hot air sterilization

Hot air:  170C for 2 hr

Autoclave: 121C for 15 min.

9


Filtration

 

Hepa vs membrane filtration


HEPA: Removes microbes > 0.3um

 

Membrane Filtration:  Removes Microbes > 0.22um

 

 

10


Microbial Control

 

Low temp

High Pressure

Desiccation

Osmotic Pressure

Chemicals

Low temperature:  Inhibits microbial growth

  • Refrigeration
  • Deep Freezing
  • Lyophilization

 

High Pressure:  Denatures proteins

Desiccation:  Prevents Metabolism

Osmotic pressure:  causes Plasmolysis (Shrinkage from loss of water)

Chemicals:  controls growth by reducing population to safe levels on living and inanimate objects.

11


Radiation


Ionizing radiation - damages DNA & ionizes water to release OH

  • X-rays
  • gamma rays
  • electron beams

Nonionizing radiation - Damages DNA

  • UV
  • 260nm

Microwaves - kills by heat except antimicrobial

12


Disinfectants


Phenol & Phenolics (Carbolic acid) - Disrupt plasma membranes

Bisphenols (Hexacholorphene & Triclosan) - Disrupt plasma membranes

Biguanides (Chlorhexidine) - Disrupt plasma membranes

  • High specificity to bacterial cell membrane
  • has broad spectrum activity (Both gram - and gram + bacteria)

Halogens (Iodine & Chlorine)

Alcohol (Ethanol & Isopropanol) - Dentaures protein, dissolves lipids. Requires water

 

 

13


Heavy Metals


Ag (Silver), Hg (Mercury) & Cu (Copper)

 

Silver Nitrate:  Prevents gonorrheal ophthalmia neonatorum

 

Silver Sulfadiazine:  Toopical cream used on burns

 

Copper sulfate:  an algicide

 

Oligodynamic action:  Denature proteins

 

14


Surfactant


Soap:  Degerms

 

Acid-anionic detergents:  sanitizing

 

Quarternary Ammonium Compounds:  bactericidal, denatures proteins & distrupts plasma membrane

15


Food Preservative

Organic Acids (Sorbic acid, benzoic acid, calcium propionate)

  • Inhibits metabolism
  • controls mod and bacteria in food & cosmetics

 

Nitrite

  • Prevents endospore germination

 

Antibiotics (Nisin & Natamycin)

  • Prevents spoilage of cheese

16

Aldehydes


Inactivates protein by cross linking w/ functional groups

 

Use:  Medical Equipment

Glutaraldehyde

formaldehyde

Orthophthalaldehyde

17

Gas Sterilants


Denatures proteins

Use: Heat-sensitive material

Ethylene oxide

18


Peroxygens


Oxidizing agents

 

Use:  Contaminated surfaces

 

19


Microbial characteristics


most resistant to least

 

Prions

endospores

mycobacteria

vegetative protozoa

Gram -

Fungi

viruses w/o envelope

gram +

viruses w/ lipid envelopes

20

Chemotherapy


Paul Ehrlich, Chemist: methylene blue for staining bacteria. Dyed rabbit ear vein

 

Koch:  Alkaline methylene blue w/ heat to stain waxy envelope

 

Alexander Fleming:  Discovered mold, penicillium notatum

21


Anitmicrobial Drugs

Chemotheraphy - The use of drug to treat disease

 

Antimicrobial drugs: Interferes with microbial growth in host

 

Antibiotic:  inhibits microbes using substance produced by a microbe

 

Selective toxicity:  Kills microbes w/o damaging host

22


Antimicrobial spectrum


Broad spectrum

Narrow spectrum

Superinfection

23


Penicillin


Natural

Penicillin G (injection)

Penicillin V (Oral)

 

Semisynthetic

Oxacillin (Narrow - Gram +)

Ampicillin (Extended - many Gram -)

 

 

24


Cell wall synthesis


1st Generation:  Narrow spectrum

 

2nd generation:  Extended spectrum

 

3rd Generation: includes psudeomonads

 

4th generation:  Broadest spectrum

25


Polypeptide antibiotics


Bacitracin (topical)

against Gram +

 

Vancomycin

Glycopeptide

Last Line against anitibiotic resistant S. aureus

26

Antibiotic Resistance

  • Enzymatic destruction of drug
  • Prevention of penetration of drug
  • Alteration of drug's target site
  • Rapid ejection of the drug

27

Causes of antibiotic resistance

  • Using outdated or weakened antibiotics
  • Using antibiotics for the common cold and other inappropriate conditions
  • Using antibiotics in animal feed
  • Failing complete the prescribed regimen
  • Using someone else's leftover prescription