General Bacteriology Flashcards
What are microbes and what are the major classifications
Microbe: micro-organism (either single cell or colony of cells)
* Bacteria, archaea, eukaryote
What can you see with a light vs electron microscope
- Electron microscopy for: protein/virus
- Light microscopy: bacteria/RBC/cells
Compare eukaryote, bacteria, and archaea
- chromosome topology
- extrachromosomal DNA
- peptidoglycan in cell wall
- cell membrane lipids
- ribosome
- transcription and translation
eukaryote
- linear
- none
- none
- polyunsaturated
- 80S
- no
Bacteria/prokaryotes
- circular
- plasmid
- yes
- saturated or monosaturated
- 70S
- yes
Archaea/prokaryote
- circular
- plasmid
- none
- saturated
- 70S
- no
What are the features of fungi
Fungi: eukaryotic
* In many varieties of environment – can grow at low temp (20-30C)
* High pressure and low pH tolerant
* Saprophytic (eat dead)
What are the relevant structural features of fungi
Structure: unique to fungi, can be used as antifungal drug targets
* Cell wall: chitin
* Cell membrane: ergosterol
How is taxonomy used for bacteria? What are 4 other ways to classify bacteria?
Taxonomy: genus (collection of species with related properties) + species (collection of strain with common properties but are different)
* Can have subspecies based on phenotypic or genotypic differences
* Genotype: genetic makeup
* Serovar/serotype: based on antigenic properties
* Pathovars/pathotypes: based on pathogenic properties/virulence factors
* Phage factors: ability to be lysed by bacteriophage
What are 3 types of fungi morphology? How is morphology influenced by temperature?
Mold: mycelial growth at body and enviro temp
Yeast: bacterial-like growth at body and enviro temp
Dimorphic: mycelial growth at enviro temp + yeast growth at body temp
What are the 2 parts of mold
- Mycelium = mat of branching hyphae (vegetative form)
- Hyphae = long/branching/filamentous
o Septate (small spaces between cells) or non-septate (cells continuous)
What is the morphology of yeast
Yeast: bacterial-like growth at body and enviro temp
* Single celled
* Oval or bottle shaped/footprint) or large/encapsulated
* Budding
What are fungal spores
Fungal Spores: disseminate and germinate
* Many types of spores
What are the 3 main morphologic types of bacteria? What do they look like? How to see them?
Coccus: sphere in chains or clump
* Use gram stain
Bacillus: rods
* Use gram stain
Spirochaete : helical
* Use dark field microscopy without a stain
What are 6 morphologies of cocci bacteria + an example of each
- Coccus (1)
- diplococcus (2): Neisseria spp.
- streptococci (chain): SS. pyogenes
- tetrad (4 in a cube): Micrococcus spp.
- sarcina (8 in a cube): Sarcina spp.
- staphylococci (grape bunching): S. aureus
What are 5 morphologies of bacilli bacteria + an example of each
- Bacillus: E. coli
- Diplobacilli: Coxiella burnetii
- streptobacilli (chain): Strreptobacillus moniliformis
- palisades (fence-like): Corynebacterium diphtheriae
- coccobacilli (plump, look like something between cocci and bacillus): P. multocida
5 major differences of prokaryotes and eukaryotes
Prok
- no nuclear membrane with circular chromosome +/- plasmid
- smaller ribosomes (70S)
- peptidoglycan
- lipid membrane is saturated - monosaturated
- coupled translation and transcription
3 major morphotypes of bacteria
cocci
baccilus
spirochetes
2 major morphotypes of fungi
mold
yeast
How do gram - differ from gram +
Gram -
thinner peptidoglycan
outer membrane with LPS
M ain surface components of bacteria? What are the main functions
Bacterial cell envelope (protect against desiccation/antimicrobials/phagocytosis)
- capsule
- cell wall
- cell membrane
Flagella (movement)
Fimbriae (adhesion/conjugation)
What are the 3 main ways bacteria acquire DNA
horizontal gene transfer
- ttraansformation
-transduction - conjugation
What are 3 morphologies of spirochete bacteria + an example of each
- Vibrio: comma shape, Vibrio spp.
- Spirilium: thick rigid spiral, Spirillum minus
- Spirochete: thin/slender, Leptospira spp.
What are 3 other shapes of bacteria (not cocci/bacillus/spirochete) and what do they look like
- Filamentous: long chain/filament
- Star shape: flat/6-pronged
- Box-shape: rectangular
Why does bacterial morphology/shape matter?
- Change primary selective pressure: nutrient gathering/cell division/predation
- Change secondary selective pressure: attachment to surfaces/motility
What are 5 steps of staining bacteria
Staining
1. Heat or chemical fixation
2. Crystal violet stain
3. Iodine stain: less soluble = adhere to cell wall
4. Alcohol: decolourization, wash away staining from gram (-)
5. Safranin: counterstain, stain gram (-)
Explain the colours of a gram stain and why do the respective bacteria stain this way?
Gram (+) = purple
* Thick peptidoglycan layer (90% wall)
Gram (-) = pink
* Thin peptidoglycan layer (10% wall) + high lipid
What are the 6 main functions of the bacterial envelope
- Protection: prevent phagocytosis and drying
- Nutrient transport
o Permeability barrier - Adhesions: attachment/pathogenesis
- Enzymes: peptidoglycan hydrolase impact growth/development and survival
- Virulence
- Chemoreceptors
What are the 3 functions of fimbrae/flagella
- Motility
- Adhesion
- Conjugation (via pilus)
What is a bacterial capsule and what is its functions (4)
Capsule: extracellular polymeric material
* Capsule/glycocalyx or slime layer
o Can visually see the slimy/mucoid appearance of colonies
* Help form biofilm formation/adherence/virulence
* Increase environmental resistance (drying/antimicrobials)
How do you stain a bacteria to highlight its capsule
- McFadden stain used to stain capsule pink
2 bacterias that produce capsules
- Ex. anthrax, Klebsiella
What is the functions of the bacterial cell wall
- Structure/shape/protection against osmotic shock/rupture
- Virulence factor
- Can be immunologically distinct between strains
What type of antibiotic targets the bacterial cell wall? How?
- Target for antimicrobials: beta-lactams
o Ex. penicllin: Target transpeptidase and prevents peptidoglycan synthesis = cell wall lysis
What are the layers from inside > out of a gram negative bacterias outer membrane
- Cytoplasm
- Phospholipid inner membrane
- Peptidoglycan
- Lipopolysaccharide (toxic to mammalian cells)
What is LPS and why is it bad? What are the consequences?
LPS: endotoxin, heat stable
* Released when bacteria is ruptured
* O antigen produces immune response – used for serotyping
* Lipid A component: responsible for many toxic effects
o Can cause uncontrolled activation of immune system and production of cytokine storm = endotoxic shock
What are the clinical signs of endotoxemia
Endotoxemia
* Fever/hypoglycemia/thrombosis/DIC/death
* Congested MM/scleral injection (enlarged vessels)
What are exotoxins and where do they come from? How do they do damage?
Exotoxins:
* Produced by live gram (+) bacteria (mainly)
* Heat labile
* Specific damage due to receptor mediator interaction
What are 2 examples of bacteria that produce exotoxins
- Ex. C. tetani = tetanospasmin
o C. botulinum = botulinum toxin - Lipoteichoic acid = similar effect to LPS
What is the structure and functions of the bacterial cell membrane
- Similar to cell membrane in eukaryotes
- Lipid bilayer with proteins
- Selectively permeable
- Site of respiratioin/ssecrretion/photosynthesis
- Sensing proteins/enxymes/transport proteins
Compare Flagella and Fimbriae
- protein components
- function
- structure
- bacterial type
Flagella:
* Protein = flagellin
* In motile bacteria
* Long/filmentous
* Gram (-)
Fimbriae/Pili
* Protein = pilin
* Vary in number aand type
* Thin/straight/thread-like
* Adhesion/conjugation
* Gram (-)
What is unique about transcription and translation in a bacteria
Couple Transcription and Translation: fast
How does translation vary between bacterial cells and eukaryotes? Why is it important
- Use small ribosome (70S = 30S + 50S) – can be aa target for antimicrobials (because eukaryote is 80S – 40S + 60S)
Describe the 3 types of horizontal gene transfer that bacteria use to swap genetic material
- Horizontal gene transfer: transfer of genes between bacteria
o Transduction: uptake of DNA from lysed bacteria
Natural process that can be replicated in lab
o Conjugation: transfer of plasmids (both gram + and -)
Pilus formation occurs in gram (-)
Require F+ and F- (F = plasmid)
Important in gram (-) in antimicrobial resistance development - Ex. E. coli
o Transformation: transfer of genes between bacteria and lysogenic phages (bacteriophage)
What are 3 main categories of mechanisms of genetic variation in bacteria
horizontal gene transfer
* Mutation
* Transposition (transposons moving within bacteria)
What 2 genera of bacteria form spores
- Genera: Bacillus and Clostridium
What is the structure of a bacterial spore
- 7 layers
1. Exosporium
2. Coat
3. Outer membrane
4. Cortex
5. Germ cell wall
6. Inner membrane
7. Core
How to destroy bacterial spores
very environmentally resistant
- Inhibition: UV/ultra-high temp/chemicals
What are 6 main growth requirements of bacteria
- Energy source: sun/organic carbon/inorganic carbon
- Carbon source: organic carbon/CO2
- Major elements: C/O/H/N/S/P/K/Mg/Fe/Ca/Mn
- Trace elements: Mn/Co/Cu/Zn/Mo
- Growth factors: amino acids/vitamin
- Environment: temp/pH/osmotic pressure/O2
How does temperature affect bacteria
- Membrane gelling: enzymatic reactions slowed or not at all
o Membrane is gel - Temp at which enzymatic reactions occur = growth rate
- Temp at maximum enzyme function – high end, right before denaturing
How are bacteria classified based on temperature range? Why is it important
- Mesophile bacteria cause infection in mammals (grow at body temp)
- Some important bacteria psychrophiles (grow at low temp)
o Listeria - Psychrophiles > mesophile > thermophile > hyperthermophile
How are bacteria classified based on pH range
- Varied pH in body (ex. stomach = barrier to prevent infection)
- Acidophile/neutrophile/alkaliphile
How do bacteria deal with variation in osmotic pressure
Osmotic Pressure: bacteria tolerant to variation than eukaryotic cells due to cell wall
* Pathogenic bacteria commonly grow best at physiologic saline concentrations
* Superoxidase dismutase used to break down
How do bacteria metabolize oxygen
Oxygen Metabolism : depends on presence of enzymes used to break down O2
* Superoxidase dismutase used to break down
Oxygen Metabolism : depends on presence of enzymes used to break down O2
* Enzymes that cause oxygen metabolites
* Mechanisms to break down radicals (H2O2/O2-)
- Enzymes that cause oxygen metabolites
- Mechanisms to break down radicals (H2O2/O2-
What are 5 categories of bacteria based on their ability to process oxygen
- Obligate aerobes: need O2, aerobic resp
- Facultative anaerobes: grow with or without O2
- Microaerophilic: need low O2 (lower than atmospheric)
- Aerotolerant anaerobes: mainly do anaerobic resp but can survive with O2 exposure
- Obligate anaerobes: anaerobic resp only
List 3 methods of sterilization
- Heat/radiation/filtrationChemicals (ethylene oxide/ozone/formaldehyde/H2O2/plasma)
What are 2 methods of heat sterilization
- Steam autoclaving
- Boiling is not sterilization
- Pasteurization – heating food to kill potential human pathogens
List 8 methods of food storage/prep
- Refrigeration (4C): kill most but not some (listeria/yersinia)
- Freeze (-20C): kill most but some can live (thaw in fridge to prevent growth)
- Boil
- Pasteurize
- Irradiate (gamma/UV)
- Vacuum pack
- Osmotic pressure
- Acidify
Compare sterilization/disinfection/antisepsis
Sterilization: destroy all viable microorganisms
Disinfection: reduce pathogenic organisms on fomites
Antisepsis: inactivate or destroy microbes with a chemical
What is one consideration you should have when disinfecting
- Inhibited by organic matter (must remove before)
List 5 types of disinfectants
- Ethanol (70%)
- Isopropyl Alcohol (70%)
- Bleach (5.25%): sodium hypochlorite
- Virkon: ozone/sodium dodecylbenzenesulfonate/sulfamic acid/inorganic buffer
- PREempt (4.25%): H2O2
What is 70% ethanol used for? What are limitations?
o Denature protein/dissolve lipid = kill bacteria and virus
o Not effective for spores
o No residue/but dehydrates living tissue
What is 70% isopropyl alcohol used for? What are limitations?
o Denature protein/dissolve lipid = kill bacteria and virus
o Not effective for spores
o No residue/less dehydration of living tissue
How should bleach be prepped for disinfection? Contact time?
o 1:10 dilution in water (can damage surfaces)
o Contact time = 10m
What is the function of virkon? Contact time?
o Bactericidal/fungicidal/virucide
o Cleaning and disinfectant (good detergent) + noncorrosive
o Contact time = 10m
What is the function of PREempt? Contact time?
o Bactericidal/fungicidal/virucide
o Cleaner + disinfectant with minimal reside
o Contact time = 5m
List 2 types of antiseptics. What is their mechanism of action?
- Povidone-iodine: free ioiodine dissociated and interacts with bacteria protein/nucleotide/fatty acid = death
- Chlorhexidine gluconate: mess with bacterial cell wall = death
List the 6 steps of bacterial replication
Binary Fission
1. Increase cell mass and number of ribosomes
2. Chromosome duplication
3. Synthesis of new cell wall and cytoplasmic membrane
4. Split of chromosomes
5. Septum form
6. Cell division = identical daughter cells
What is the bacterial growth curve? How does it change?
Bacterial Growth Curve – occurs in a closed system (nutrients available and waste accumulates)
1. Lag phase
2. Log/exponential growth phase (susceptible to adverse conditions – abx)
3. Stationary phase - # new cells = # dead cells
4. Death
Duration of each phase is dependent on organism/growth condition (media type/temp)
List 2 mechanisms of direct bacterial growth assessment
Direct
* Microscopic counts
o Direct smear
o Counting chamber
o Total cell count
* Culture count
o Serial dilution (10X) then plate onto solid culture medium
Count colony forming units
o = Viable colony count (only counting the ones that grew)
List 1 mechanisms of indirect bacterial growth assessment
- Measuring cell mass
o Weight
o Biochemical activity
o = Turbidity/optical density (spectrophotometer)
What is generation time?
Generation Time: time it takes for a population to double
* Depends on growth medium
List 3 types of sources of bacteria? List some examples of each.
Other animals
* Infected animals
* Carrier animals (preclinical/subclinical/convalescent – shedding after recovery)
* Via body fluids/direct contact
Environment
* Soil (ex. pseudomonas/listeria/clostridia)
* Spores (ex. Bacillus anthracis)
* Via feed/water/fomites
Commensal
* Benign/opportunistic pathogens
List the steps of bacterial infection
- Enter portal of entry
- Encounter specific targets: not random
- Colonize targets/cross host barriers
- Spread locally and colonize new populations of target cells
- Enter blood/lymph
- Spread
- Cause dysfunction or disease
List the types of portals of entry into the body. What barriers/defences does the body use? How do bacteria get in
(oral/skin/urogenital/GI/eye/ear/placenta/umbilicus/mammary)
a. Physical/chemical barriers (pH/mucus)
b. Transport and immune systems (mucociliary apparatus/innate and adaptive)
c. Ingest/inhale/penetration/direct
List 5 methods of diagnosing a bacterial infection
- Visualize organism
- Isolate organism
- Detect genetic material of organism
- Detect a rise of antibody titre of organism
- Detect specific cell immune response
Signs are usually non-specific (fever/neutrophilic leukocytosis)
List the steps of specimen collection
Case History
Appropriate sample
method/materials (sterile)
Clear labelling
Individually package specimens
Send to lab asap
Ship/store in proper conditions
What are the important features to include in the case history when submitting a bacterial sample to lab
- Site of collection
- Clinical signs
- Treatments given
- Other animals affected
What are 4 things to note when taking a sample
Appropriate sample
* Site of infection (wall vs center of abcess)
- Ensure there is sufficient quantity (fluid volume/tissue size)
o Urine need minimum of 1ml - Before administration of abx (or must stop abx, wait for wash out period – then sample)
- Proper collection method/materials (sterile)
3 guidelines to follow when shipping/storing samples
- Refrigerate (except anaerobic swabs/blood culture bottles)
- Sip with ice
- Arrive to lab within 24hrs (max 72hrs)
List 6 methods of bacterial identification
- Direct exam
- Culture
- Biochemical analysis (varied time associated) – not used as much anymore
- MALD MS: matrix assisted laser desorption/ionization TOF MS
- PCR:
- Serology: antibody titre
