Microbial Growth And Control Flashcards
Explain the statement “Bacteria Grow”
- # of cells are increasing ( ^ reproductive process)
- Before a bacteria cell can divide into 2 daughter, the parent cell must make a copy of its genetic chromosome (DNA replication)
Why is the log scale used for the y-axis of bacterial growth curves?
-its easier to predict growth linearly compared to exponentially, due to the unchanging slow as time increases on the x-asis
State and explain the 4 phases of bacterial growth
1) Lag phase: # of cells are constant/no division
- microbe is adapting to culture conditions (synthesis of needed enzymes
2) Exponential phase (log phase): rapid growth (binary fission)
- Increase in nutrients and decrease in waste=growth
- sporulation occurs at the end of this phase
3) stationary phase: # of cells are constant, growth rate=death rate
- decrease in nutrients, increase in waste
4) Decline/death phase: # of cells decrease, rate of death> rate of growth
- substantial increase in wastes, substantial decrease in nutrients
Some growth curves have only 3 phases. Which phase is not always present in a bacterial growth curve? Why?
- Lag phase
- Some bacteria don’t need to adapt to their environment. But may need to develop enzymes to metabolize the nutrients
What is the equation for the exponential growth of bacteria. Explain what each term means
N(t) = N(0) x 2 ^t/d)
N(t)= total number of cells at time t
N(0)= the number of cells to start with at time 0
t= time that has passes
D=doubling time
Define Sanitizer
- an agent that reduces the number of microbes to a safe level
Define disinfectant
- an agent applied to inanimate objects to reduce the microbial load
Define antiseptic
-an agent applied to human tissues to reduce microbial load
define antimicrobial agent
-an agent that could be antiseptic, disinfectant, or antibiotics
Define sterilant
- an agent that destroys all microbes including bacterial endospores
Define Batericidal
-an agent that destroys all vegetative bacterial cells
Define bacteriostatic
-an agent that prevents vegetative bacterial cells from reproducing
Define Virucidal
-an agent that inactivates virus particles so they cannot infect
Define fungistatic
-an agent that stops fungi from reproducing
Define Sporicidal
- aka sterilant
- it kills all bacterial endospores and other microbes
Define degerming agent
- physically removing microbes
Define cleaner
- an agent that removes dirt and decrease microbes
What is a phenolic? Explain how they work
- disinfecting agent
- denatures proteins and disrupt plasma membranes of microbes
- effective in the presence of organic material and remain active on surfaces long after application
-general types of chem disinfectants: Phenolics, halogens, alcohols, hydrogen peroxide
Explain how hexachlorophene works
- antiseptic agent that works by disrupting plasma membranes of microbes
- can also be used as a disinfectant
Explain how chlorhexidine works
- an antiseptic agent that disrupts the plasma membranes of microbes
- also can be used as a disinfectant
Name some examples of halogen based control agents and explain how they work
- Iodine, betadine
- disrupts protein synthesis and membranes
- oxidizes proteins
- Chlorine
- powerful oxidizer (DNA, proteins, membranes)
How do alcohol-based antiseptics and disinfectants work? Explain the relationship between water and alcohol-based antiseptic effectiveness.
- Alcohol based antiseptics needs to be between 60-95% alcohol to kill organisms. Too little or too much concentration will not be able to kill the microorganism
- needs water to be effective
What is a quat? How do they work?
- super soap/detergent that is considered a disinfectants and antiseptic
- denatures proteins and disrupts plasma membranes
What is the oligodynamic effect? Which chemicals does the term oligodynamic effect apply?
- describes how specific agents such as heavy metals, help denature proteins at very low concentrations
- silver ions
What are 2 examples of antiseptics based upon the oligodynamic effect
- silver nitrate: used as drops to prevent neonatal gonorrheal infection
- silver sulfadiazine: antiseptic cream on burns to prevent infection
Name 3 organic acids used as preservatives. How do they work?
- Sorbic acid, Benzoic acid, and calcium propionate
- controls molds and bacteria in food
How does ethylene oxide work? What is it used for?
- chemically reactive gas that modifies the proteins, lipids, and DA in the chamber by alkylating proteins, DNA, RNA.
- used on heat-sensitive medical instruments like plastic probes
- long exposure time needed
Most resistant to least resistant microbes
1) Endospores
2) Myobacteria
3) Cyst of Protozoa
4) vegetative Protozoa
5) Gram - bacteria
6) Fungi, including fungal spores
7) Viruses without envelopes
8) Gram + bacteria
9) Virusus with lipid evelopes
What are some factors that affect bacterial growth?
- Physical conditions
- temp, pH, osmotic pressure
- chemical conditions
- CHNOPS (macronutrients)
- inorganic elements: Na, Cl, K
- gases
