L31 Flashcards
Name the steps of prokaryotic cell division.
- Initiated @cytoplasmic membrane
- Daughter chromosomes anchored to membrane
- Septum grows & divides daughter cells
What causes bacteria remain linked to form chains/clusters?
Incomplete cleavage of septum
What are obligate aerobes?
Require O2 b/c acts as terminal e- acceptor
What are obligate anaerobies?
Energy via fermentation
NO O2
What are facultative anaerobes?
Grow w/ or w/o O2 - can do both respiration or fermentation
Generally prefer O2
What are microaerophiles?
Can handle low levels O2
What are the 2 reasons anaerobes can’t handle O2?
- Don’t have superoxide dismutase
- No catalase or peroxidase
No ways to degrade superoxide or hydrogen peroxide –> stick around and kill anaerobic bacteria
What are the 3 classification of bacteria by temperature?
Thermophilic = like hot Mesophilic = like body temp Psychrophilic = cold
What are the 4 phases of a bacterial growth curve?
Lag phase Exponential (log) phase Stationary phase - Reproduction = death Decline (due toxic byproducts of reproduction)
What occurs during the lag phase?
Bacteria:
- Store nutrients
- Synthesize enzymes
- Prepare for binary fission
What is the generation time? Give the equation.
Time required for cell # to double
g = t/n
(n = # generations aka # times cell population doubles during the time interval)
How do you test generation time?
Pour plate
- Serial dilutions
- Plate & count CFUs
Define asepsis.
State of being free of micro-organisms
Define sterilization.
Elim ALL viable organisms & spores
Define disinfection.
Kill MOST micro-organisms
Define sanitization.
Reduce pathogen level
Germicide
Kills bacteria & some spore
Disinfectant
Kills bacteria, fungi, viruses
Ineffective vs spores
Antiseptic
Bacteriostatic
What is the hierarchy of resistance of microbes to disinfection?
Least resistant = enveloped viruses (lipo-philic) Bacteria Non-envelop/hydrophilic viruses Mycobacteria Spores
Autoclaving
Pressure + heat + steam
What are other disinfection options?
Hot air sterilization Filtration disinfection Radiation (UV vs ionizing) Ethylene oxide = sterilization Alcohol (ethyl & isopropyl) Halogens (chlorine)
What are the options for disinfecting the skin?
Alcohol scrub > soap
EXCEPT C.diff - soap to clean off spores!
Describe the 4 main characteristics of a biofilm.
- Attached to hydrated surface
- Embedded in polysacc slime
- Behave as community
- Antibiotic resistant & can’t be cleared by host immunity
Name some biofilm associated diseases.
CF Endocarditis Osteomyelitis Chronic UTI Prostatitis Otitis media Dental infections Indwelling medical device infections
Why are microbes in a biofilm resistant to antibiotics?
Slow growing
Reduce antibiotic penetration
What is an issue with attributing an infection to a biofilm?
MIC/MBC inaccurately predict bacterial populations IN SITU
- CFU counts
