Topics 10-29 Flashcards
What are the 3 types of thermal preference
- psychrophilic
- mesophilic
- thermophilic
What are the temperature ranges in psychrophilic Bb
<15°c
Temp. for Mesophilic Bb
15-45°c
Temp. for Thermophilic Bb
> 45°c
How do Bb reproduce
binary fission
How do Bb grow
-incr. in size and Vol.
Name the phases of Bb propagation
- lag phase
- exponential (log) phase
- stationary phase
- regressive phase
How can you count the total count of Bb
- microscopic count (bürker chamber)
- electronic cell count
- spectrophotometry (turbidity)
- flow cytometer
How can you count the total live count of Bb (Cfu/ml)
- broth dilution method
- plate count
- -spread plate
- -pour plate
- membrane filter
What is a CFU
In microbiology, a colony-forming unit is used to estimate viable bacteria or fungal cells in a sample
How can you maintain a Bb culture
- on media
- in the freezer
- -@-18 - -80°c
- lyophilisation
How can we describe the environmental conditions for Bb propagation
- optimal - fast replication
- tolerable - decr. replication
- non tolerable - no repl., Bb die
How can one make the conditions non tolerable for Bb
- drying
- cooling, keeping warm
- salting, addition of sugar
- pickling
How can we control Bb
- physical agents
- chemical agetns
Name physical agents used for controlling Bb
- pasteurisation
- sterilisation
Name chemical agents used for controlling Bb
- disinfection
- antibiotics, antibacterial agents
Bb are more susceptible to cold than heat T/F
F
Bb are resistant to cold T/F
T
Name some thermal sterilisation methods
- dry heat: oven, flaming, incineration
- moist heat: autoclave, steaming, boiling
Pasteuriasation
62-140°c for a certain period of time
the hotter the shorter time is necessary
Mechanical pressure resistance of Bb
- 5-6*10^7 Pa
Even ultrasound can not damage the cytoplasmic membrane T/F
F
Aim of disinfection
- elimination of pathogens
- reduction of saprophytes
Disinfection is a selective method T/F
F
Name the criteria a disinfectant needs to fullfill (8)
- broad spectrum
- lack of toxicity, mutagenicity, carcinogenicity
- non toxic to environment
- good penetration
- odourless
- water soluble
- non corrosive
- low cost
Activity of disinfectant is influenced by
- resistance of Bb
- number of Bb
- Cc of disinfectant
- temp.
- time
- pH
- surface
How is the activity of a disinfectant quantified
- species killed
- species inhibited
- speed of inactivation
- side effects
Name the 2 types of disinfecting agents
- disinfectants
- antiseptics
What can you use disinfectants for
utensils, stables, vehicles..
What can you use antiseptics for
skin, mucous membranes, tissues
Name all the disinfectants (10)
- Halogens
- Aldehyes
- oxidative agents
- alcohols
- detergents
- phenol
- acids, alkalis
- salts
- dyes
- sterilising gases
Name an example of a halogen
Cl2
In what disinfectant can halogens be found
household bleach
How do organic clorine compounds act
- slow long release, stable
- disinfection of hand
- func. with oxidation
Spectrum of organic iodine
bactericidal, fungicidal, sporocidal, virucidal
Characterize aldehydes
- highly reactive
- use reduction, alkylation
- wide spectrum
Name some examples of Aldehyde disinfectants
- Formaldehyde
- -gas form too
- -vaccine prod.
- -toxic
- Glutaraldehyde
Name some oxidative agents
- H2O2
- -for wounds
- -damage of cyoplasmic mem., DNA
- urea hydrogen peroxide
- peracetic acid
- ozone
All oxidative agents have a fairly wide spectrum T/F
T
Characterise alcohols
- activity correlates with chain length
- water is needed
- denaturate proteins
Spectrum of alcohols
-bactericidal, virucidal
Name the 2 parts of Detergents
hydrophilic hydrophobic
Name the 4 groups of Detergents
- anionic
- cationic
- amphoter
- non ionic
Anionic detergents
- soaps, SDS
- no disinfecting ability
Cationic detergents
- react on lipids
- only bactericidal (G+mostly)
Characterize phenol
- good antibacterial activity
- toxic
- increased permeability
- cell wall denat.
- bactericidal, fungicidal
Name some acid disinfectants
lactic acid, acetic acid, formic acid
Mode of action of acids
coagulation of proteins
Spectrum of acids
bactericidal fungicidal
Name some salts used
Hg,Ag, Cu
Spectrum of salts
bactericidal, fungicidal
Name some disinfecting dyes
crystal violet, brilliant green, methylene blue, malachit green
How do dyes work as disinfectants
enzyme inactivation
Spectrum of dyes
bactericidal fungicidal
Name some sterilising gases
ethylene oxide, propylene oxide, ß-propiolactone
what are sterilising gases used for
sterilisation of heat sensitive material
Spectrum of sterilising gases
sterilisation
mode of action of salts
enzyme inactivation
mode of action of phenol
- denat. of proteins
- incr. permeability
- cell wall dead
Mode of action of oxidative agents
- oxidation nanednana
- - protein, DNA, cell wall lipids
What are Antibiotics
microbial metabolites which can kill or inhibit growth of susceptible bacteria
When was penicillin discovered
1929
Who discovered Penicillin
Alexander fleming
What does the use of AB depend on
their selective toxicity
What must Abs exploit to make sure only their targeted Bb gets hurt
biochemical differences in structures and metabolic pathways of Bb and eukaryotic cells
Antibacterial activity has to have…
.. narrow range but a broad spectrum
What effects do Abs have
- bacteriostatic
- bactericidal
What do Bacteriostatic agents do
inhibit growth of Bb
What do Bactericidal agents do
cause irreparable damage and Bb cell death
Name some bacteriostatic agents
- tetracycline
- chloramphenicol
- macrolides
- sulfonamides
- trimetoprim
- nitrofurans
Name some bactericidal agents
- ß-lactam Abs
- polypeptides
- aminoglycosides
- quinolones
- bacitracin
- vancomycin
Name all the ways Abs can hurt Bb (7)
- inhibition of cell wall synthesis
- inhibition of cell membrane function
- inhibition of protein synthesis
- inhibition of DNA dependent RNA polymerase
- inhibition of DNA gyrase
- disruption of DNA structure
- inhibition of DNA synthesis
Name the cell wall inhibitors
- Penicillin
- Cephalosporins
- Vancomycin
How does Penicillin work
blocks peptidoglycane synthesis - inhibits cross linking
Penicillin works only against Bb in the stationary phase T/F
F only against Bb in log phase
How does Penicillin get excreted
via the kidney
Which Bb does Penicillin work against
mainly Gr+ and some Gr-
Which Bb are resistant to Penicillin
Bb with a thin peptiglycan layer and impermeable LPS
and beta lactamase test or lack of penicillin binding protein rec.
How does Cephalosporin act
inhibition of transpeptidase enzymes (resp. of synth. pentapeptide units)
Bb resistant against Cephalosporin have
- structural advantages
- modified binding sites
- beta-lactamase enzymes
Cephalosporin is active aminly against
Gr+ Bb
Damagers of cell membrane
Polymyxins
What do polymyxins have
a defined hydrophobic and hydrophilic part
How do polymyxins work
they bind to cell membrane phospholipids - cause structural disorganization and permeability damage
Whcih Bb do polymyxins attack
only Gr-
Polymyxins can act only on multiplying cells T/F
F multiplying and stationary
Name the 2 groups able of inhibiting protein synthesis
Aminoglycosides
Tetracyclines
Name the Aminoglycosides
- Streptomycin
- Neomycin
- Kanamycin
- Gentamycin
What do the protein synthesis inhibiting agents act on
30s
What is 30S
prokaryotic small ribosomal subunit, subunit of 70S ribosome found in prokaryotes. is implicated in the binding of tRNA on mRNA The small subunit is responsible for binding and reading mRNA during translation
What do the Aminoglycosides cause
Misreading of the mRNA by binding to the 30S ribosome and halting the 30S initiation complex
What is the result of the Aminoglycoside action
-faulty proteins are produced
against which Bb are the Aminoglycosides active
agaisnt Gr- Bb and myco Bb
How can Bb be resistant against Aminoglycosides
- binding site
- anaerobic Bb (O2 requ. for uptake)
- inactivating enzymes
- ph - active in an alkaline environment
what is MIC
minimum inhibitory concentration
Name the Tetracyclines
- Tetracycline
- Oxytetracycline
- Chlortetracycline
- Doxycycline
How do tetracyclines act
inhibition of binding of tRNA
What do tetracyclines bind to
reversibly bind to the 30S ribosome and inhibit binding of aminoacyl-t-RNA to the acceptor site
Name the groups whcih can inhibit Protein synthesis (50S)
- Chloramphenicol
- Macrolids
- Lincosamides
Name the Chloramphenicol group
- Chloramphenicol
- Thiamphenicol
- Florfenicol
What do Chloramphenicols inhibit
peptidyl transferase
Name the Macrolids
- Erythromycin
- Oleandomycin
- Tylosin
- Tilmicosin
- Tiamulin
What do the macrolids inhibit
inhibition of binding tRNA to ribosomes
Which agents can inhibit the superhelx of DNA
Quinolones
Name some Quinolones
-nalidixic acid
-oxolinic acid
-flumequine
…
What do Quinolones inhibit
-inhibit DNA gyrase (prevent coiling)
How can Bb be resistant to Quinolones
- transport
- obligate anaerob.
- mod. gyrase
Which agents can inhibit RNA replication
Rifampins
How do Rifampins act
inhibit DNA dep. RNA polymerase
Which agents inhibit intermediate metabolism
- Sulfonamides
- diaminopirimidines
Sulfonamides and diaminopirimidines act how
interfere with biosynthesis of folic acid
What agents produce metabolites against Bb DNA
- Nitrofurans
- Nitroimidazoles
What are the principles of antibiotic therapy
- used on the basis of correct diagnosis
- most effective antibiotic
- correct dosage
- correct treatment time
- tissue concentration must exceed effective concentration in the site of infection
Resistance to Ab occurs bc.
- enzymatic drug inactivation
- modification of binding sites
- decr. IC accumulation
- alteration in metabolism
Name the types of resistance
- Innate
- Acquired
- Cross resistance
- Multiresistance
What is innate resistance
chromosomally encoded , general physiology of Bb (e.g. cell wall structure)
What is acquired resistance
can arise from a mutation or transfer of genetic material encoding resistance genes
What is cross resistance
a single mechanism confers resistance to multiple antimicrobial agents
How can antimicrobial susceptibility be tested in Bb
- disc diffusion method
- Broth dilution method
- E-test
Describe the disc diffusion test
- prepare a uniform disk of Bb
- put paper discs each with a different antimicrobial agent on the disk
- check for zones of inhibition
Factors affecting the size of the zone of inhibition
- size of inoculum
- test medium
- antimicrobial agent and concentration
- incubation condition
How to evaluate the disc diffusion test
- Susceptible if diameter is >20mm
- moderately susceptible 15-20mm
- resistand <15mm
Broth dilution method is performed how
preparing a two fold dilution of an antibiotic in a series of tubes
each tube is inoculated with Bb and then incubated
measure turbidity
How much cell volume does the DNA take up
10%
How is the genetic material structured in Bb cells
- Chromosome
- extrachromosomal genetic elements: Plasmids, Bacteriophages
Possible forms of DNA
haploid, circular, double stranded
Plasmids have single stranded DNA T/F
F double stranded
Plasmids are relatively uniform in size T/F
F vary size
Plasmids replicate independently from the chromosome T/F
T
Name the number of plasmids in one cell
1-4 - 20-30
Name the most important plasmids
- F:fertility
- R: antibiotic resistance
- bacteriocins
- Ent: enterotoxin prod.
- Hly: haemolysin
- Attachment (fimbria, capsule)
What are Bacteriophages
viruses which infect bacteria
Which kinds of DNA do Bacteriophages have
- dsDNA
- ssDNA
- dsRNA
- ssRNA
Prophage
the DNA is integrated into the bacterial chromosome
After the binary fission daughter cells are genetically identical T/F
T
What is a Mutation
change in the base sequence of DNA
Name the different kinds of mutations
- spontatneous
- induced
- point
- missense
- nonsense
- reversion
What can mutations influence
- cell structure
- metabolism
- resistance
- virulence
Name potential mutations influencing cell structure
- colony morphology
- cell wall synthesis
- capsule formation
- flagella formation
- fimbria prod.
Potential mutations influencing resistance
- antibacterial drugs - mutation on the ribosome
- phage - mutation on binding site
Mutations influencing virulence
- toxin prod.
- capsule form.
- fimbria prod.
What’s Transposition
translocation of DNA elements in the genome
Name the 2 ways of Transposition
- IS (insertion sequence) elements
- Transposons
What are transposons
segments of DNA that can move from one region of DNA to another and integrate
What are insertion sequences
800-1400 bp sequences without code function
Where could a transposons be transfered to
from a chromosome to a plasmid for example
What are Mutations, Recombinations, Transpositions
Genotypic variants
What’s recombination
receiving new genes encoding new characteristics
Name the forms of recombination
- conjugation
- transformation
- transduction
- phage conversion
How is conjugation performed
DNA transfer between two Bb in contact with each other using sex fimbria
What are the two parties in Conjugation called
donor and recipient cells
What is the conjugation mediated by
the plasmid called F-Factor - fertility factor
What is actually being transferred in Conjugation
the F-plasmid which copies itself OR parts of the chromosome
How does the copied plasmid insert itself in the new genome
inserts itself on a specific site in the chromosome
How does Transformation work
DNA is transferred as naked DNA - breaks - taken up - a piece of the received DNA is integrated - unused DNA is degraded
What does competent mean in regard to Tranformation
competent cells let large DNA molecules pass their cell wall
What is Transduction
DNA transaction by a bacteriophage
2 forms of Transduction
- generalized
- specialized
How does generalized transduction work
Phage infects cell A - A DNA is incorporated in phage - Cell A lyses - phage infects cell B - DNA A becomes integrated in B
Hoe does specialized transduction work
some phages can integrate into the host cell genome - gets excised - phage incorporates original cell genes and replicates - cell is lysed phages are released - infect new cell and incorporate into genome
What are phenotypic variants
results of environmental effects
What could phenotypic variants influence
- morphology
- resistance
- enzyme prod.
Phenotypic variations always only influence one cell T/F
F whole population can be affected
How to examine the bacterial genome
- GC ratio/content
- DNA fingerprinting
What does DNA-DNA hybridization do
compares similarity between DNA sequences
How to amplify DNA
PCR
Genomes of bacteria are elastic
Genomes of bacteria are elastic meaning they often receive new genetic info. recombination can be beneficial neutral or harmful
What is the difference between Sterilisation and Disinfection
- Sterilisation= all bacteria, viruses, fungi, spores, parasites, prions are dead
- disinfection= killing all pathogenic bacteria, and significant reduction of microbial flora
Where to find saprophytes in a host
in a natural bacterium flora
in a symbiosis or mutualism
e.g: colon flora
In what relationship are path. Bb with their host
Parasitism - fac. pathogens
predatory prey interaction - obgl. path.
What’s the definition of pathogenicity
the ability of a microbe to damage a host
Pathogenicity is qualitative concept T/F
T
Virulence is a qulitative concept T/F
F quantitative concept
What is Virulence in relation to pathogenicity
the degree of pathogenicity
amount of all factors of pathogenicity
connected to a bacterium strain
How to measure virulence
in animal trials
only in target animal species !
What parameters are used in animal trials
MLD (minimum lethal dose) /MID(minimum infective dose)
-death of all trial animals
LD50/ID50
-death of 50% of trial animals
Virulence is not a constant feature T/F
T
What can be an incr. in virulence
- passage in the host species (selection of more virulent Bb)
- recombination
- -induced
- -spontaneous
What can be a decr. in virulence
- mutation
- spontaneus
- passage
- -maintanance in lab
What are virulence factors
- features involved in pathogenicity
- morphological, metabolic, structural .. characteristics
- different properties
How can virulence factors be grouped
- non toxic
- toxic
Where could be cell wall associated virulence factors be found
- capsule
- adhesins
- antiphagocytic materials
Name capsule associated virulence factors
- D-glutamic acid polypeptide
- hyaluronic acid
- polysaccharides
- inhibits phagocytosis, protects Bb
- better replication
Name adhesins associated virulence factors
- fimbria
- surface proteins
Name antiphagocytic materials virulence factors
- prevent the fusion of phagosoma and lysosoma
- lipid complexes
- mycolic acid, waxes
Name all the extracellular enzymes (10)
- coagulase
- fibrinolysin
- hyaluronidase
- collagenase
- lipase
- lecitinase
- deoxyribonuclease
- urease
- leucocidins
- hemolysins
Who can prod. exotoxins
Gr+ & Gr-
Who can produce endotoxins
Gr-
How are exotoxins released
excreted
How are endotoxins released
cell lysis
Endotoxins are more toxic than Exotoxins T/F
F
