LEcture 9 Flashcards
What would be an example of exponential growth in microbes?
- microbe population that doubles at a constant rate
What are the phases of the growth curve?
- lag phase
- exponential (log) phase
- stationary phase
- death phase
What occurs in the lag phase?
- cell synthesize new components
- this allows them to adapt to new medium
Can the lag phase vary?
- yes, it can be short or absent
What occurs in the exponential phase of growth curve?
- the rate of growth is constant
- population is uniform in terms of chemical and physical properties
What happens in the stationary phase of prokaryote growth?
- growth ceases, maintaining constant # of viable cells
- can occur due to inactivation of reproduction or from same rate of cell death
What are direct methods to measure microbial growth?
- plate counts
- filtration
- MPN
- Direct microscopic count
What are indirect methods of microbial growth?
- turbidity
- metabolic activity
- dry weight
What are physical requirements for cell growth?
- temperature
- pH
- osmotic pressure
What are chemical requirements for chemical growth?
- carbon
- nitrogen, sulfur, phosphorous
- trace elements
- oxygen
- organic growth factor
Is the use of a spectrophotometer indirect or direct method of counting?
- indirect method
How have thermophiles made adaptations to survive at extreme temperatures?
- grow at higher temperatures and require
- more H bonds
- more prolines
- chaperones
- histone like DNA stabilizing proteins
Which type of microbes are able to grow around our body temperature?
- mesophiles
What microbes grow at temperatures below our body temperatures?
- psychrophiles
- psychotrophs
What is an acidophile?
- microbe that grows at pH between 0-5.5
What pH is optimal for neutrophils?
-5.5 to 7
What pH is optimal for alkaliphiles?
- 8.5 to 11.5
What is aerotolerance?
- ability of a microorganism to grow in presence or absence of oxygen
Can antibiotics penetrate the biofilm?
No, difficult to remove the biofilm as well
How do prokaryotes reproduce?
- binary fission
- budding
- conidiospores or actinomycetes
- filament fragmentation
What do strict anaerobe microbes lack that prevents them from growing in aerobic conditions?
- SOD
- catalase
What are barophilic organisms?
- organisms that grow better in high pressures due to changes in membrane fatty acids
How is a biofilm produced?
- microbes reversibly attach to a surface and release polysaccharrides, proteins and DNA to form extracellular polymeric substance
- the biofilm matures as more polymers are released
Disinfection?
- destruction or removal of vegetative pathogens but NOT bacterial endospores. Used on inanimate object
Sterilization?
- complete removal of all viable microorganisms, Used on inanimate object
Antisepsis?
- chemical applied to body surface to inhibit vegetative pathogens
Chemotherapy?
- chemicals used internally to kill or inhibit growth of microorganisms within host tissue
Sanitization?
- reduce microbial population to levels deemed safe
What are chemotherapeutic agents kill and what ones inhibit growth?
kill: cidal agent
growth inhibition: static agent
What conditions will contribute to the effectiveness of antimicrobial agents?
- population size
- population composition can change sensitivity to chemical
- [chemical]
- length of exposure to chemical
- temperature (high=death. cold not so dead)
- local environment: effects are specific to the microbe
What will moist heat destroy?
- virus, fungi, bacteria
will not destroy endospore - is -cidal
What is a sterilization technique effective against all microorganisms?
autoclave. Kills spores even!!! OMG My excitement!!!
What is pasteurization?
- process to kill pathogens and reduces spoilage rate by removing number of organisms present
- NOT sterilization
What is dry heat sterilization?
- less effective than wet heat sterilization
- oxidizes cells constituents and denatures proteins
UV radiation causes thymine dimers and has been used for what cleaning process?
- water treatment
What is ionizing radiation effective and not effective against?
- treats bacterial enospores
- not effective against all viruses
Phenolics are chemical control agents that act how?
- common disinfectant
- denature proteins and disrupt cell membrane
- skin irritant, bad smell
Describe aspects of alcohol disinfectants.
- most widely used (ethanol and isopropanol)
- not sporicidal. bactericidal, fungicidal
- denature proteins, possibly dissolve lipid membranes
What are halogen antimicrobial agents?
- fluorine
- chlorine
- bromine
- iodine
- astatine
Features of iodine.
- skin antiseptic
- oxidizes cells and iodinates proteins
- skin damage, staining, allergen
- spore killer at [high]
Features of chlorine.
- oxidize cell constituents
- water supply disinfectant
- destroy vegetative bacteria and fungi
- Cl gas is sporicidal
What heavy metals can be used as a chemical control agent?
- Hg
- Ag
- Ar
- Zn
- Cu
- work well but are toxic
- combine to inactivate/precipitate proteins
What are quaternary Ammonium compounds?
- detergents with antimicrobial activity and effective disinfectants
What type of detergents make good disinfectants?
- cationic as they kill most bacteria and they are safe and easy to use.
- inactivated by hard water and soap though
Why are aldehydes good chemical control agents?
- highly reactive molecules that are sporicidal
- combine to inactivate nucleic acids
What are sterilizing gases, ethylene oxide, betapropiolactone, hydrogen peroxide, effective against?
- microbbicidal and sporicidal
- inactivate DNA and proteins
What are chemotherapeutic agents?
- antibiotics
- destroy pathogenic microbes or at least inhibit their growth
Penicillin?
- block enzyme catalyzing transpeptidation
- prevents cell wall synthesis, causing cell lysis
- only acts on growing bacteria
- binds periplasmic proteins
- activate bacterial autolysins and murein hydrolases
- stimulate bacterial holins to form holes or lesions in PM
What are narrow spectrum penicillins?
- V and G which are naturally occurring
What are broad spectrum penicillins?
- semisynthetic but also have higher rate of resistance
What are cephalosporins?
- block enzymes catalyzing transpeptidation
- prevent cell wall synthesis, causing cell lysis on growing bacteria
- broken into 4 generations to cover different spectrums
What are two glycopeptide antibiotics?
- vancomycin and teicoplanin
Vancomycin.
- glycopeptide antibiotic
- treat antibiotic resistant staphylococcal/ enterococcal infection
Teicoplanin.
- glycopeptide antibiotic
- treats antibiotic resistant staphylococcal/enterococcal infections
What antibiotics inhibit protein synthesis?
- chloramphenicol
- streptomycin
- tetracyclines
- aminoglycosides
How does tetracycline work as an antibiotic?
- prevent tRNA from binding at the A site
- bacteriostatic (slow bacterial growth)
How does chloramphenicol work as an antibiotic?
- binds 50S region and inhibits peptidyl transferase reaction
- inhibits polypeptide elongation
- dangerously toxic
How does streptomycin work as an antibiotic?
- alters 30S shape, causing mRNA strand to read incorrectly
- altering the polypeptide sequence
How do aminoglycosides work as an antibiotic?
- bind to 30S and inhibit translation process and causing misreading.
- has levels of resistance and can be toxic
What is a macrolide drug?
- erythromycin broad spectrum bacteriostatic
- inhibits peptide chain elongation
- used in place of penicillin allergy
What do metabolic antagonists, that act as antimetabolites, do?
- antagonize or block functioning of metabolic pathways by competitively inhibiting metabolites by enzymes
What are sulfonamides?
- broad spectrum antibiotic that inhibit folic acid synthesis
- PABA (paminobenzoic acid) analog that has different funciton
How does sulfamethoxazole work?
- analog of PABA, but blocks transition from PABA to dihydrofolic acid by competitive inhibition
How does trimethoprim work?
- blocks the transition from dihydrofolic acid to tetrahydrofolic acid
- causes photosensitivity and ABD pain
What is the overall function and effect of sulfonamides?
- blocking synthesis prevents the activation of DNA/RNA precursors and prevents DNA/RNA formation
What are quinolones?
- broad spectrum synthetic that inhibits bacterial DNA gyrase and topoisomerase II
- bactericidal for wide range of infections
What are two examples of quinolones?
- nalidixic acid
- norfloxacin
Describe features of antifungal drugs.
- low therapeutic index with high toxicity.
- treats superficial mycoses better than systemic
Why is it important to treat systemic mycoses?
- difficult to control and can be fatal
What are three common drugs used to treat systemic mycoses?
- amphotericin B
- 5-flucytosine
- fluconazole
How does amphotericin B work on systemic mycoses?
- binds to sterols in the membrane
How does 5-flucytosine work on systemic mycoses?
- disrupts RNA function
When is fluconazole used and why?
- low side effects
- used prophylactically
What is amantidine?
- anti viral Rx
- blocks penetration and uncoating of influenza virus
Adenine arabinoside (vidarabine)
- anti viral
- inhibit herpes virus; DNA and RNA synthesis proteins
Tamiflu?
- anti viral influenza
- nueraminidase inhibitor
Acyclovir?
- anti viral
- inhibits herpes virus DNA pol
Valacyclovir?
- anti viral
- prodrug form of acyclovir
Ganciclovir?
- anti herpes virus drugs
Foscarnet?
- inhibits herpes virus DNA pol
HPMPC (cidofovir)
- broad spectrum anti DNA virus drug
- inhibits viral DNA pol of:
- papovavirus, adenovirus, herpes virus, iridovirus, poxvirus
Azidothymidine
- nucleoside reverse transcriptase inhibitor
Ritonavir
- viral protease inhibitor
Fusion inhibitors?
- prevent HIV entry into cells
In what ways can a drug be resisted by a microbe?
- prevent entrance, promote loss of drug
- inactivate drug
- modify target enzyme/organelle
- increase production of targeted meatabolite
What is an immunity gene?
- genes that protect antibiotic producing microbes from their own product
What is carried on R plasmid and how can it be transferred?
- multiple resistance genes
- transferred by conjugation, transformation, transduction
