(02) Bacterial Growth and Development Flashcards
How does the growth rate of bacteria complicate identification of pathogens?
- what methods are used to circumvent this problem?
- Fast growing bacteria mask slower growing pathogens like fungus
- Different media is used to inhibit the growth of bacteria to isolate a single type
What 4 factors does the growth rate of an organism depend on?
- Nutrient Availability
- pH
- Salinity
- Temperature
Differentiate phototrophs and auxotrophs.
Phototrophs
- can make all of their own essential metabolites
Auxotrophs
- must acquire essential metabolites from the environment
What is the effect of acidic pH on most bacteria?
- notable exception?
- disease?
- Toxic to most bacteria
Helicobacter pylori
- Stomach Ulcers by secreting urease to convert urea into ammonia and bicarbonate
What is the effect of salt on bacterial growth?
- High Salt environments typically prevent bacterial growth
What is the optimal growth temperature of most human pathogens?
- name for these?
- 30ºC - 37ºC
- Mesophiles
Iron is important to growth and virulence. How do pathogens ensure they have sufficient iron?
- Secrete Siderophores that bind Fe
2. Siderophore-Fe is ACTIVELY transported back into the bacteria
Average time needed for pathogenic replication?
- Mycobacterium Tuberculosis?
- E. Coli?
- 30-60 minutes for most bacteria to replicate
- Mycobacterium Tuberculosis = 20 hours
- E. Coli = 20 minutes
What are the 4 phases of bacterial growth?
- explain each of these phases
- Lag Phase
- must adapt to new nutrient environment - Exponential Phase
- Constant optimal doubling times are established
- Maximal DNA and Protein Synthesis - Stationary Phase
- Nutrients depleted during exp. phase = waste accumulates
- cell death = cell growth - Decline
- more waste, less nutrients
- Cell death > Cell Growth
What does it mean to measure the turbidity of a liquid culture?
- Measure bacterial concentration using a spectrophotometer
When during which phase is sporulation initiated?
- cell type that does this?
- Stationary Phase
- Gram (+) bacteria initiates sporulation during this time
When is the best time to administer antibiotics?
- Exponential Phase
Planktonic Bacteria vs. Biofilm
- en vitro vs. en vivo prevalence
Planktonic Bacteria
- common in laboratory
- Free-living Bacteria (en vitro)
Biofilm
- encased bacteria
- 80% of infections (en vivo)
Biofilm
- what forms encasement?
- clinical importance?
- Carbohydrate matrix encasement
Clinical Importance:
- Source of recurrent infections and treatment failures
- IMPAIRS ANTIBIOTIC ACCESS
- ANTI-PHAGOCYTIC
Common places to find biofilms?
- Heart Valve Implants
- Implanted Prostheses
- Dental Plaque
- In-dwelling catheters
Relationship of Cystic Fibrosis to biofilms?
- Pseudomonas Aeruginosa forms ALGINATE biofilm
ATPs produced by oxidative respiration.
- what general cell types can do this?
- final electron acceptor
- 34 ATPs produced
- Cell Types = aerobes and facultative anaerobes
- O2 = final electron acceptor
Compare growth rates of anaerobic respiration to aerobic respiration.
- electron acceptors
anaerobic
- slow, inefficient
- electrons transferred directly to organic acceptors
Aerobic
- fast, efficient
- electrons transferred to oxygen (inorganic)
What toxic products are produced as a result of aerobic respiration?
- what counteracts their effects?
- Superoxide anions and Hydrogen Peroxide
Superoxide:
Superoxide dismutase turns it into H2O2
H2O2:
Detoxified by 1) Catalase or 2) Peroxidase
What detoxification enzyme may be lacking from facultative anaerobes?
Catalase
T or F: pathogenic anaerobes can survive brief exposure to oxygen
True
Folic acid, compare how humans get it vs. bacteria.
Humans:
- must get it from enviroment
Bacteria:
- Synthesize their own (major target)
Why would it be difficult to isolate Rickettsia or Chlamydia?
- They are OBLIGATE INTRACELLULAR PATHOGENS
- they depend on a host to grow and would need a lab growing animal cells in culture to grow it (NOT PRACTICAL, not pt. of diagnosis)
In the context of commensal organisms that are part of the normal human flora, differentiate resident and transient organisms.
Resident - present all the time
Transient - contracted by the environment but removed after a finite time
Describe how normal flora of the skin, gut, and vagina prevent growth of pathogenic organisms.
Skin:
- Produces Fatty acids to prevent growth of new bacteria
Gut:
- Extremely dense giving little room for growth while producing lots of waste and toxins.
Vagina:
- Flora produces acid to deter growth of new bacteria
What tissues of the body are typically sterile?
- Internal Tissues and blood
What is blood in bacteria referred to as?
Bacteremia
Pathogenesis
Mechanism of Disease Development
Virulence
a term expressing degrees of Pathogenicity
Colonization
the presence and multiplication of microorganisms without tissue invasion or damage
Infection
colonization that generally leads to disease
Epidemic
disease that rapidly affects many people in a fixed period of time
Virulence factor
Any number of products produced and often secreted by pathogens that allow the pathogen to invade and cause disease in a host and evade host defenses.
Name 5 examples of virulence factors
- Adhesion Factors
- Capsules
- Endotoxins
- Exotoxins
- Siderophores
