Flashcards in FA - Micro - Basic Bacteriology Deck (139):
What is the function of the peptidoglycan?
Gives rigid support - Protects against osmotic pressure.
What is the chemical composition of peptidoglycan?
Sugar backbone with peptide side chains cross-linked by transpeptidase.
What is the function of cell wall/cell membrane?
Major surface antigen.
What is the chemical composition of the cell wall/cell membrane?
Peptidoglycan for support. Lipoteichoic acid includes TNF and IL-1.
What is the function of the outer membrane (gram neg.)?
Site of endotoxin - LPS - Major surface antigen.
What is the chemical composition of the outer membrane (gram neg.)?
1. Outer leaflet = Contains LPS/LOS.
2. Embedded proteins = Porins + Outer membrane proteins (OMPs).
3. Inner leaflet = Phospholipids.
What is the function of the plasma membrane?
Site of oxidative and transport enzymes.
What is the chemical composition of the ribosome?
What is the function of the periplasm?
Accumulates components exiting Gram(-), including HYDROLYTIC ENZYMES (eg beta-lactamases).
What is the chemical composition of periplasm?
Space between cytoplasmic membrane and outer membrane in Gram(-) = Peptidoglycan in the middle.
What is the function of the capsule?
Protects against phagocytosis.
What is the chemical composition of the capsule?
Polysaccharide - EXCEPT Bacillus anthracis --> D-glutamate.
What is the function of the pilus/fimbria?
Mediate adherence of bacteria to cell surface - sex pilus forms attachment between 2 bacteria during conjugation.
What is the chemical composition of pilus/fimbria?
What is the function of the flagellum?
What is the chemical composition of the flagellum?
What is the chemical composition of a spore?
Keratin-like coat - Dipicolinic acid - Peptidoglycan.
What is the function of the glycocalyx?
Mediates adherence to surfaces, especially foreign surfaces (e.g., indwelling catheters).
What is the chemical composition of the glycocalyx?
LOOSE NETWORK of POLYSACCHARIDE.
Mention the gram(+) cocci.
Staph + Strep
Mention the gram(-) coccus.
Neisseria + Moraxella.
Mention the gram(+) rods.
4. Gardnerella (gram variable).
7. Mycobacteria (acid fast).
Mention the gram(-) enterics.
Mention the gram(-) respiratory bacteria.
1. Haemophilus (pleiomorphic)
2. Legionella (silver)
Mention the gram(-) zoonotic bacteria.
Mention the 2 branching filamentous bacteria.
2. Nocardia (weakly acid fast)
Mention the 2 pleiomorphic bacteria.
1. Rickettsiae (Giemsa)
2. Chlamydiae (Giemsa)
Mention the 3 spirochetes.
2. Borrelia (Giemsa)
Does Mycoplasma + UREAPLASMA gram stain?
No - No cell wall - Contain sterols, which do not Gram stain.
Bacteria with unusual cell membranes/walls.
Mycoplasma --> Contain sterols and have no cell wall.
Mycobacteria --> Contain mycolic acid. High lipid content.
Mention some bacteria that do NOT gram stain well.
4. Legionella pneumophila
What is the mnemonic for the bacteria that do NOT gram stain very well?
These Microbes May Lack Real Color.
What is the problem with treponema?
Too thin to be visualized.
What do we do to visualize treponemes?
Dark-field microscopy and fluorescent antibody staining.
What is the problem with Mycobacteria?
High lipid content in cell wall detected by carbofuchsin in acid-fast stain.
How do we stain Legionella?
What does Giemsa stain?
What is the mnemonic for the bugs that Giemsa stain?
Certain Bugs Really Try my Patience.
When do we use PAS (periodic acid-Schiff)?
Stains glycogen - mucopolysaccharides - used to diagnose Whipple disease --> Trophyrema Whipplei.
When do we use Ziehl-Nielsen (carbol fuchsin)?
1. Acid-fast organisms - Nocardia, Mycobacterium (stains mycolic acid in cell wall).
2. Protozoa - CRYPTOSPORIDIUM OOCYSTS.
When do we use India ink?
C.neoformans - mucicarmine can also be used to stain thick polysaccharide capsule RED.
When do we use silver stain?
1. Fungi (PCP + COCCIDIOIDES)
What is the medium used for isolation of H.influenza?
Chocolate agar with V(NAD+) + X (hematin).
What is the medium used for Neisseria isolation?
Thayer-Martin (or VPN):
V --> Vancomycin --> Kills Gram(+).
P --> Polymyxin (TMP + Colistin) --> Kills Gram(-) except Neisseria.
N --> Nystatin --> Kills Fungi.
What is the medium used for B.pertussis?
1. Bordet-Gengou (potato) agar (Bordet for Bordetella).
2. Regan-Lowe medium --> Charcoal + Blood + Antibiotic.
What is the medium used for C.diphtheriae isolation?
1. Tellurite agar.
2. Loeffler medium.
What is the medium used for M.tuberculosis isolation?
What is the medium for M.pneumoniae?
Eaton agar - Requires cholesterol.
What are the media used for Lactose-fermenting enterics' isolation?
MacConkey agar --> Pink colonies - Fermentation produces acid, turning colony pink.
What is the medium used for Legionella?
Charcoal yeast extract agar buffered with cysteine + iron.
What is the medium for fungi?
Sabouraud agar - "Sab's is a Fun guy!"
Mention some obligate aerobes.
Use and O2-dependent system to generate ATP.
Mention the main obligate anaerobes.
What are the main features of obligate anaerobes?
1. Lack catalase and SOD
2. Susceptible to oxidative damage.
3. Generally foul-smelling (short-chain fatty acids).
4. Difficult to culture.
5. Produce GAS in tissue (CO2, H2)
Are aminoglycosides effective against obligate anaerobes?
NO - Aminoglycosides require O2 to enter into bacterial cell.
Mention the obligate intracellular bugs.
Chlamydia + Rickettsia + COXIELLA - Can't make own ATP.
Mention the facultative intracellular bugs.
Mention the main encapsulated bacteria.
2. H.influenza type B
7. Group B strep
Mention some main catalase (+) bacteria.
What is the mnemonic for the cat(+) bacteria?
You need PLACESS for your cats.
Mention the urease(+) bugs.
What is the mnemonic for urease(+) bugs?
CHuck Norris hates PUNKSS.
Mention some pigment-producing bacteria.
3. P.aeruginosa (Aerugula = Green)
4. Serratia marcescens.
What pigment does A.israellii produce?
YELLOW sulfur granules - composed of filaments of bacteria.
What pigment does S.aureus produce?
What pigment does P.aeruginosa produce?
What pigment does Serratia marcescens produce?
What is the role of bacterial virulence factors?
Promote evasion of host immune response.
What is the protein A?
Binds Fc region of IgG - Prevents opsonization + Phagocytosis - Expressed by S.aureus.
What is the IgA protease?
Enzyme that cleaves IgA.
Which bugs secrete IgA protease?
2. H.influenza type B
in order to colonize the respiratory mucosa.
What is the M protein?
Helps prevent phagocytosis.
Which bug expresses protein M?
Group A strep.
What is the location of the genes of exotoxin and endotoxin?
Exotoxin --> Plasmid or phage.
Endotoxin --> Bacterial chromosome.
Exotoxin or endotoxin is more toxic?
Exotoxin --> High (fatal doses on the order of 1μg).
Endotoxin --> Low (fatal doses on the order of hundreds or micrograms).
Compare the clinical effects of exotoxin and endotoxin.
Exotoxin --> Various effects.
Endotoxin --> Fever, shock (hypotension), DIC
What is the mode of action of exotoxin?
What is the mode of action of endotoxin?
TNF, IL-1, and IL-6.
Compare the antigenicity of exotoxin and endotoxin.
Exotoxin --> Induces high-titer antibodies called antitoxins.
Endotoxins --> Poorly antigenic.
Compare the vaccines for exotoxins and endotoxins.
Exotoxin --> Toxoids used as vaccines.
Endotoxin --> No toxoid formed and no vaccine available.
Compare the heat stability of endotoxin/exotoxin.
Exotoxin --> Destroyed rapidly at 60C - except staph enterotoxin.
Endotoxin --> Stable at 100C for 1hr.
Mention typical diseases associated with exotoxins.
Mention typical diseases associated with endotoxin.
2. Sepsis by gram(-) rods.
What is the toxin of C.diphtheriae?
What is the toxin of P.aeruginosa?
What is the mechanism of BOTH diphtheria toxin and exotoxin A?
What are the manifestations of C.diphtheriae?
Pharyngitis with pseudomembranes in throat and severe lymphadenopathy (bull neck).
What are the manifestations of P.aeruginosa?
Host cell death via exotoxin A.
What is the toxin of Shigella spp.?
Shiga toxin (ST).
What is the toxin of EHEC (incl. O157:H7 strain)?
Shiga-like toxin (SLT)
What is the mechanism of Shiga toxin (ST) and Shiga-like toxin (SLT)?
Inactivate 60S ribosome by removing adenine from rRNA.
What are the manifestations of Shigella?
1. GI mucosa damage --> Dysentery.
2. ST also enhances cytokine release --> HUS.
What are the manifestations of EHEC?
1. SLT enhances cytokine release --> HUS
2. Unlike shigella, EHEC does not invade host cells.
What are the 2 toxins of ETEC?
1. Heat-labile toxin (HL)
2. Heat stable toxin (ST)
What is the mechanism of LT ETEC toxin?
Overactivates cAMP --> UP Cl secretion in gut and H2O efflux.
What is the mechanism of ST toxin of ETEC?
Overactivates cGMP --> DOWN resorption of NaCl and H2O in gut.
What are the manifestations of ETEC?
Watery diarrhea --> Labile in the Air (Adenylate cyclase)
--> Stable on the Ground (Guanylate cyclase).
What is the toxin of B.anthracis?
What is the mechanism of B.anthracis?
Mimics the adenylate cyclase enzyme (UP cAMP).
What are the manifestations of B.anthracis?
Likely responsible for characteristic EDEMATOUS BORDERS of black eschar in cutaneous anthrax.
What is the toxin produced by V.cholerae?
What is the mechanism of cholera toxin?
Overactivates cAMP by permanently activating Gs --> Incr. Cl secretion in gut and H2O efflux.
What are the manifestations of cholera toxin?
Voluminous "rice-water" diarrhea.
What is the toxin of Bordetella pertussis?
What is the mechanism of Pertussis toxin?
Overactivates adenylate cyclase --> UP cAMP --> By DISABLING Gi.
===> Impairing PHAGOCYTOSIS to permit survival of microbe.
What does B.pertussis cause?
1. Child coughs on expiration and "whoops" on inspiration.
2. Toxin may actually be a cause of cough.
3. Can cause 100-day cough in adults.
What is the toxin of C.tetani?
What is the toxin of C.botulinum?
What is the mechanism of BOTH tetanospasmin and botulinum toxins?
BOTH are PROTEASES --> Cleave SNARE (soluble NSF attachment protein receptor), a set of proteins required for neurotransmitter release via vesicular fusion.
What are the manifestations of C.tetani?
2. Risus sardonicus
4. Toxin prevents release of inhibitory (GABA and glycine) neurotransmitters from Renshaw cells in spinal cord.
What are the manifestations of C.botulinum?
1. Flaccid paralysis
2. Floppy baby
3. Toxin prevents release of stimulatory ACh at neuromuscular junction --> Flaccid paralysis.
What is the toxin of C.perfringens?
What is the mechanism of alpha toxin?
Phospholipase (LECITHINASE) that degrades tissue and cell membranes.
What are the manifestations of C.perfringens?
Degradation of phospholipids:
1. MYONECROSIS ("gas gangrene").
2. HEMOLYSIS ("double zone" of hemolysis on blood agar).
What is the toxin of S.pyogenes?
What is the mechanism of Streptolysin O?
Protein that degrades cell membrane.
What are the manifestations of S.pyogenes?
1. Lyses RBCs.
2. Contributes to β-hemolysis.
3. Host antibodies against toxin (ASO) used to diagnose rheumatic fever (do not confuse with immune complexes of poststreptococcal GN).
What toxins act like superantigens causing shock?
1. TSST-1 (S.aureus)
2. Exotoxin A (S.pyogenes)
What is the mechanism of superantigen-toxins?
Bring MHC II and TCR in proximity to outside of antigen binding site to cause overwhelming release of IL-1 + IL-2 + IFN-gamma + TNF-alpha --> SHOCK.
What are the manifestations of toxic shock syndrome?
4. Other toxins cause scalded skin syndrome (exfoliative toxin) and food poisoning (enterotoxin).
Mention 4 bacteria that inhibit protein synthesis.
4. EHEC (incl. O157:H7)
Mention 3 bacteria that increase fluid secretion.
Mention a bacterium that inhibits phagocytic ability.
Mention 2 bacteria that inhibit release of neurotransmitters.
Mention 2 bacteria that lyse cell membranes.
2. S.pyogenes (streptolysin O)
Mention 2 bacteria that release superantigens causing shock.
1. S.aureus (TSST-1)
2. S.pyogenes (exotoxin A)
What does endotoxin activate?
1. Macrophages (TLR4)
3. Tissue factor
What happens when the macrophages are activated via endotoxin?
IL-1 --> Fever.
TNF --> Fever and hypotension.
NO --> Hypotension.
What happens when the complement is activated via endotoxin?
1. C3a --> Hypotension, edema.
2. C5a --> Neutrophil chemotaxis.
What happens when tissue factor is activated via endotoxin?
Coagulation cascade --> DIC.
What is the mnemonic for endotoxin?
eXtremely heat stable
What is termed transformation in bacterial genetics?
Ability to take up naked DNA (i.e., from cell lysis) from environment (also known as "competence"). Any DNA can be used.
Transformation is a feature of which bacteria?
2. H.influenza type B
What happens in F+ x F- conjugation?
1. F+ plasmid contains genes required for sex pilus and conjugation.
2. Bacteria without this plasmid are termed F-.
3. Sex pilus on F+ bacterium contacts F- bacterium.
4. A SINGLE STRAND of plasmid DNA is transferred across the conjugal bridge ("mating bridge").
5. NO TRANSFER OF CHROMOSOMAL GENES.
What happens in Hfr x F- conjugation?
1. F+ plasmid can become incorporated into bacterial chromosomal DNA, termed high-frequency recombination (Hfr) cell.
2. Replication of incorporated plasmid DNA may include some flanking chromosomal DNA.
3. Transfer of plasmid and chromosomal genes.
What is termed "transposition"?
1. Segment of DNA (transposon) that can "jump" (excision and reintegration) from one location to another.
2. Can transfer genes from plasmid --> chromosome and vice versa.
What happens in generalized transduction?
1. A "packaging" event.
2. Lytic phase infects bacterium --> cleavage of bacterial DNA.
3. Parts of bacterial chromosomal DNA may become packaged in PHAGE caspid.
4. Phage infects another bacterium --> transfers these genes.
What happens in specialized transduction?
1. An "excision" event.
2. Lysogenic phage infects bacterium.
3. Viral DNA incorporates into bacterial chromosome.
4. When phage DNA is excised --> flanking bacterial genes may be excised with it.
5. DNA is packaged into phage viral capsid and can infect another bacterium.