Chapter 4 Flashcards
- Orderly increase in the sum of all the
components of an organism - Cell multiplication, increase in the number of
single bacteria making up population , “culture”
growth
the number of viable cells per unit volume of
culture
cell concentration
dry weight of cells per
unit volume of culture
biomass concentration
- Can be measured by cell concentration (the
number of viable cells per unit volume of
culture) - Biomass concentration (dry weight of cells per unit volume of culture)
Viable cell count
- Measured by photoelectric means
- Related to viable count using a standard curve
-A barely turbid suspension of Escherichia coli
contains about 107 cells per milliliter, and a
fairly turbid suspension contains about 108 cells per milliliter
turbidity
The Growth Rate Constant
Can be measured in grams of biomass producedper hour
Product of time (t)
Growth rate constant (k)
Biomass concentration (B)
Exponential growth
Increase in cell number, not cell size!
microbial growth
what are the physical requirements for growth: Temperature
minimum growth temperature, optimum growth temperature, maximum growth temperature
Five groups based on optimum growth
temperature
- Psychrophiles
- Psychrotrophs
- Mesophiles
- Thermophiles
- Hyperthermophiles
– period of little or no cell division and it
can last for 1 hour or several days
Lag
cells begin to divide and enter a period
of growth or logarithmic increase; cells are
most active metabolically
log
metabolic activities of
individual surviving cells slow; microbial death
balance the no. of new cells; period of
equilibrium
stationary
no. of death exceeds the no. of new
cells formed
death
- Death mean irreversible loss
If it fails to give rise to a colony
Depends on the medium
First hour after treatment are also critical in the determination of “killing.”
measurement of death
physical methods for bacterial control of microbial growth
sterilization
Disinfection
Pasteurization
aseptic technique
Some Common biocides used for Antisepsis, Disinfection, Preservation and other purposes
alcohols, aldehydes, Biguanides, Bisphenols, Halogen-releasing agent, heavy metal derivatives, organic acids, peroxygens, phenols and cresol, quaternary ammonium compounds, vapor phase
Strategies to Control Bacteria at the Environmental Level
Antibiotics as the gold standard of treatment
Prevent exposure to infectious agents
destroys or eliminate all forms of microbial life from an object or environment
sterilization
eliminates many or all pathogenic microorganisms, except bacterial spores from an object or an environment
disinfection
application of heat, for the purpose of killing or retarding the development of pathogenic bacteria
pasteurization
pathogenic organisms are reduced to safe levels on in animate object, reducing cross infection
sanitization
removal of organic or inorganic material from objects and surfaces, manually or mechanically using water with detergent or enzymatic product
cleaning
chemical or physical agent usually broad spectrum that inactivates microorganisms
biocide
- term to a property by which biocide is able to kill bacteria
- Killed organism can no longer reproduce even after being removed from contact with the agent
- causes lysis (dissolution) of the cells
bacteriocidal
- the property by which a
biocide is able to inhibit bacterial multiplication
Upon removal of the agent multiplication
resumes
fungistatic and sporostatic
bacteriostatic
presence of pathogenic microbes in
living tissues
septic
free of, using method to free of
microorganism
aseptic
– agents that destroy or inhibit the
growth of microorganism in or on living tissues
antiseptic
substance added to food
products or to an organic solution to prevent
chemical change or bacterial action
preservative
- substance that interferes with a
particular metabolism
Bactericidal or bacteriostatic
antibiotics
General Mechanism of Biocide Action
Disruption of the Cell membrane or wall
Protein Denaturation
Disruption of Free Sulfhydryl Groups
Damage to DNA
Chemical Antagonism
Physical Methods
simplest means of sterilizing materials
bactericidal and sporicidal if performed
appropriately
heat
bactericidal but not sporicidal
radiation
used of biochemical agents
chemical agents
liquid desiccants, bactericidal but
not sporicidal
alcohols
disinfection and sterilization of
instruments, endoscopes and surgical tools. Bactericidal and sporicidal
aldehydes
used in hand washing and oral
products, disinfectant and preservative, bactericidal but not sporicidal
biguanides
used in antiseptic soaps and hand
rinses, bactericidal and sporostatic (not
sporicidal)
bisphenols
Releasing agents – destroys cellular
activity of proteins, sporicidal if high
concentration
halogen
used of combination of two antibacterial agents, not sporicidal
heavy metal derivatives
preservative in pharmaceutical and food industries, neither sporicidal
organic acids
– requires high concentration to be bactericidal and sporicidal
peroxygens
have antiseptic, disinfectant or preservative properties, not sporicidal
phenols
used in variety of clinical purposes, not sporicidal
quaternary ammonium compounds
sterilized heat sensitive medical devices, sporicidal
vapor-phase sterillants
