Micro Basic Flashcards
Peptidoglycans
Composition
Function
Sugar backbone with peptide side chains cross linked by transpeptidase
Support. Protects against osmotic pressure
Lipoteichoic acid
Where is it?
What does it do?
Cell wall of Gram+
Induces TNF and IL1
LPS AKA Location What is it? Components
Endotoxin Outer membrane of Gram- Major Surface Ag Lipid A (induces TNF and IL1) O polysaccharide is the antigen
Periplasm
What is it?
What kind of organisms
What does it contain
Space between cytoplasmic membrane outer membrane
Gram-
Hydrolytic enzymes include β lactamase
Capsule
Made from…
Function
Polysaccharides (except in Bacillus anthracis which contains D-glutamate)
Protects against phagocytosis
Pilus/Fimbria
Composition
Function
Glycoprotein
Mediates adherence of bacteria to cell surface. Sex pilus for conjugation
Flagellum
Composition
Function
Protein
Motility
Spore
Composition
Function
Keratin-like coat, Dipicolinic acid, Peptidoglycan
Resistance to heat, chemicals, dehydration
Glycocalyx
Composition
Function
Polysaccharide
Mediates adherence to surfaces (especially foreign surfaces)
Outer layer composition in Gram+ vs Gram- bacteria
+
Inside to outside:
Cytoplasmic membrane, Peptidoglycan (cell wall), Capsule
Pilus, Flagellum, Lipoteichoic acid (lipids + teichoic acids)
-:
Cytoplasmic membrane, Perplasm, Peptidoglycan, Endotoxin (LPS), Capsule
Pilus, Flagellum
Outer layers of Mycoplasma
Membrane contains sterols and have no cell walls
Cell wall of Mycobacteria
Contains mycolic acid with high lipid content
Bugs that do not gram stain?
“These Rascals May Microscopically Lack Color”
Treponema (too thin), Rickettsia (intracellular), Mycobacteria (high lipid content in cell wall), Mycoplasma (no cell wall), Legionella pneumophila (intracellular), Chlamydia (intracellular and lacks muramic acid in cell wall)
Giemsa Stains for what organisms
“Certain Bugs Really Try my Patience”
Chlamydia, Borrelia, Rickettsiae, Trypanosomes, Plasmodium
PAS
Name
What does it stain?
Use
Periodic Acid Schiff Base
“PASs the sugar”
Glycogen, Mucopolysaccharides
Diagnoses Whipple’s Disease (Tropheryma Whipplei)
Ziehl-Neelsen Stain
Name
Organisms
Carbol Fuchsin
Acid Fast organisms (Nocardia, Mycobacterium)
India Ink
Cryptococcus neoformans
Mucicarmine can also be used to stain thick polysaccharide capsule red
Silver Stain
Fungi, Legionella, Helicobacter pylori
Culture Requirements for H. influenzae
Chocolate agar with factor V (NAD) and X (hematin)
Culture Requirements for N gonorrhoeae and N meningitidis
Thayer-Martin (or VPN) media
Vancomycin (inhibits Gram+ organisms), Polymyxin (inhibit Gram- organisms except Neisseria), Nystatin (inhibits fungi)
Culture Requirements for B pertussis
“Bordet for Bordetella)
Bordet-Gengou (potato) agar
Culture Requirements for C diphtheriae
Tellurite plate, Loffler’s media
Culture Requirements for M tuberculosis
Lowenstein Jensen agar
Culture Requirements for M pneumoniae
Eton’s agar
Culture Requirements for lactose fermenting enterics
Pink colonies on MacConkey’s agar (fermentation produces acid, turning colonies pink)
E coli is also grown on eosin-methylene blue (EMB) agar as colonies with green metallic sheen
Culture Requirements for Legionella
Charcoal yeast extract on agar buffered with cysteine and iron
Culture Requirements for Fungi
“Sab’s a Fun Guy”
Sabouraud’s agar
Obligate Aerobes
“Nagging Pests Must Breathe”
Nocardia, Pseudomonas aeruginosa (can use nitrates in anaerobic environment), Mycobacterium tuberculosis, and Bacillus
Obligate Anaerobes Name Weakness Gross Culture? What doe they produce? Where are they normally? What antibiotics don't work on them?
“Anaerobes Can’t Breathe Air”
Clostridium, Bacteroides, Actinomyces
Lack Catalase and/or SOD and are thus susceptible to oxidative damage
Foul smelling because of short chain fatty acids
Difficult to culture
Produce gas (CO2, H2) in tissue
Normal GI flora
Aminoglycosides ineffective because they need O2 to enter cell
Obligate intracellular bugs
“Stay inside when its Really Cold”
Rickettsia, Chlamydia
Can’t make their own ATP
Facultative Intracellular bugs
“Some Nasty Bugs May Live FacultativeLY”
Salmonella, Neisseria, Brucella, Mycobacterium, Listeria, Francissela, Legionella, Yersinia pestis
Encapsulated Bacteria Purpose of capsule Test Examples Who is especially at risk?
Antiphagocytic virulence factor that can serve as an antigen in vaccines
Quellung Positive (Swelling = Swellung)
“SHiNE SKiS”
Streptococcus pneumoniae, Haemophilus influenzae B, Neisseria meningitidies, E coli, Salmonella, Klebsiella pneumoniae, group B Strep
Asplenics. Give S pneumoniae, H influenzae, and N meningitidis vaccines
Catalase+ organisms
Function of catalase
Who is at risk?
Examples
Degrades H2O2 before it can become microbicidal
People with chronic granulomatous disease (NADPH oxidase deficiency) because they degrade the limited H2O2
“PLACESS for your CATs”
Pseudomonas, Listeria, Aspergillus, Candida, E coli, S aureus, Serratia
Problem with polysaccharide capsule antigens?
How is ti solved?
T cells not activated because polysaccharides cannot be presented Conjugate to a protein to promote T cell activation and class switching
Pneumovax
Polysaccharide vaccine w/o conjugated protein against pneumococcus
Prevnar
Conjugated Polysaccharide vaccine against pneumococcus
H influenzae Type B Vaccine
Conjugated vaccine
Meningococcal Vaccine
Conjugated vaccine
Urease+ bugs
“CHuck norris hates PUNKSS”
Cryptococcus, H pylori, Proteus, Ureaplasma, Nocardia, Klebsiella, S epidermidis, S saprophyticus
Pigment producing bacteria
Actinomyces israelii - yellow sulfur granules (israel has yellow sand)
S aureus - yellow pigment
Pseudomonas aeruginosa - blue-green (like arugula)
Serratia marcescens - red pigment (red maraschino cherries)
Protein A
Function
Organisms
Binds Fc of Ig to prevent opsonization and phagocytosis
S aureus
IgA protease
Function
Organisms
Organ susceptible
Cleaves IgA
“SHiN”
S pneumoniae, H influenzae B, Neisseria
Respiratory mucosa
M Protein
Function
Organisms
Prevents phagocytosis
GAS
Exotoxin Source Secreted from cells? Composition Location of gene Tox
Gram+ and Gram- Secreted from cells Polypeptide Plasmid or Bacteriophage Highly toxicity
Exotoxin Antigenicity Vaccines Stability Examples
Induces high titer Abs called antitoxins
Toxoids used as vaccines
Destroyed rapidly at 60 degrees (except for Staphylococcal enterotoxin)
Tetanus, Botulism, Diphtheria
Endotoxin Source Secreted from cells? Composition Location of gene Tox
Outer cell membrane of most Gram- Not secreted Lipopolysacharide (structural part of bacteria released when lysed) Bacterial chromosome Low toxicity
Endotoxin Clinical effects MoA Antigenicity Vaccines Stability Examples
Fever, Shock Induces TNF and IL1 Poorly antigenic No toxoids formed and no vaccine available Staple at 100 degrees C for 1 hour Meningococcemia, Sepsis by Gram- rods
Corynebacterium diphtheriae Kind of toxin produced? Name of toxin? MoA of toxin Manifestation
Exotoxin
Diphtheria toxin
ADP ribosylating A-B toxin: Inactivates Elongation Factor (EF2) thus inhibiting protein synthesis
Pharyngitis with pseudomembranes in throat and severe lymphadenopathy (bull neck)
Pseudomonas aeruginosa Kind of toxin produced? Name of toxin? MoA of toxin Manifestation
Exotoxin
Exotoxin A
ADP ribosylating A-B toxin: Inactivates Elongation Factor (EF2) thus inhibiting protein synthesis
Host cell death
ADP ribosylating A-B toxin
Names
MoA
Diphtheria toxin, Exotoxin A, Heat Labile, Cholera toxin, Pertussis toxin
B (binding) component binds host cell surface receptor enabling endocytosis; A (active) component attaches to ADP-ribosyl to disrupt host cell proteins
Shigella Spp Kind of toxin produced? Name of toxin? MoA of toxin Manifestation
Exotoxin
Shiga Toxin (ST)
Inactivates 60S ribosome by removing adenine from rRNA inhibiting protein synthesis
GI mucosal damage –> dysentery. Enhances release of cytokines –> HUS
Enterohemorrhagic E coli (EHEC) Strain Kind of toxin produced? Name of toxin? MoA of toxin Manifestation
O157:H7 Exotoxin Shiga-Like Toxin (SLT) Inactivates 60S ribosome by removing adenine from rRNA Enhances release of cytokines --> HUS Does not invade host cells
Enterotoxigenic E coli Kind of toxin produced? Name of toxin? MoA of toxin Manifestation
Exotoxin
Heat-Labile Toxin (LT) and Heat-Stable Toxin (HS)
HL (ADP ribosylating A-B toxin): Overactivates AC –> ↑cAMP –> ↑Cl secretion in gut and water efflux
HS: Overactivates GC –> ↑cGMP –> ↓ resorption of NaCl and water in the gut
Watery diarrhea
“Labile in Air –> AC”
“Stable in Ground –> GC”
Bacillus Anthracis Kind of toxin produced? Name of toxin? MoA of toxin Manifestation
Exotoxin
Edema Factor
Mimics AC and increases cAMP
Responsible for characteristic edematous borders of black eschar in cutaneous anthrax
Vibrio cholerae Kind of toxin produced? Name of toxin? MoA of toxin Manifestation
Exotoxin
Cholera toxin
ADP ribosylating A-B toxin: Permanently activates Gs –> Overactivates AC –> ↑cAMP –> ↑Cl secretion in gut and water efflux
Rice water diarrhea
Bordetella pertusis Kind of toxin produced? Name of toxin? MoA of toxin Manifestation
Exotoxin
Pertussis toxin
ADP ribosylating A-B toxin: Permanently inactivates Gi –> Overactivates AC –> ↑cAMP –> impaired phagocytosis to permit survival of microbe
Whooping cough (coughs on expiration and whoops on inspiration
100 day cough in adults
Clostridium tetani Kind of toxin produced? Name of toxin? MoA of toxin Manifestation
Exotoxin
Tetanospasmin
Cleaves SNARE protein required for NT release of GABA and Gly neurons (Renshaw cells in spinal cord)
Muscle rigidity, lock jaw, Risus sardonicus
Clostridium botulinum Kind of toxin produced? Name of toxin? MoA of toxin Manifestation Where do they get it from?
Exotoxin Botulinum toxin Cleaves SNARE protein required for NT release of ACh from neurons Flaccid paralysis, floppy baby Honey
Clostridium perfringens Kind of toxin produced? Name of toxin? MoA of toxin Manifestation
Exotoxin
Alpha toxin (lecithinase)
Phospholipase that degrades tissues and cell membranes
Degradation of phospholipid C –> myonecrosis (gas gangrene) and hemolysis (double zone of hemolysis on blood agar)
Streptococcus Pyogenes Kind of toxin produced? Name of toxin? MoA of toxin Manifestation
Exotoxin
Streptolysin O
Degrades cell membranes
Lyses RBCs (contributes to β hemolysis and host produces ASO used to diagnose RF)
Staphylococcus aureus Kind of toxin produced? Name of toxin? MoA of toxin Manifestation
Exotoxin
Toxic Shock Syndrome Toxin (TSST1)
Brings together MHCII and TCR to cause release of IFNγ and IL2 –> shock
TSS: fever, rash, shock
Streptococcus pyogenes Kind of toxin produced? Name of toxin? MoA of toxin Manifestation
Exotoxin
Exotoxin A
Brings together MHCII and TCR to cause release of IFNγ and IL2 –> shock
TSS: fever, rash, shock
Endotoxin Pathway of Action
LPS –> Macs –> IL1 (fever), TNF (fever hypotension), NO (hypotension)
LPS –> complement –> C3a (hypotension, edema), C5a (neutrophil chemotactic)
LPS –> tissue factor –> coagulation cascade –> DIC
Endotoxin Mnemonic
“ENDOTOXIN”
Edema, NO, DIC/Death, Outer membrane, TNFα, O Ag, eXtremely heat stable, IL1, Neutrophil chemotaxis
Bacterial Growth Curve
Lag: metabolic activity w/o division
Log (exponential): Rapid cell division
Stationary: Nutrient depletion slows growth. Spore formation in some bacteria
Death: Prolonged nutrient depletion and buildup of waste products lead to death
Which antibiotics work on the log phase?
Cephalosporins and Penicillins becuase they act on peptidoglycan synthesis
Bacterial Transformation
Mechanism
Bacteria that can do it?
Take up DNA from surroundings
“SHiN”
S pneumoniae, H influenzae, Neisseria
Conjugation
F+ x F-
Hfr x F-
F+ x F-: dsDNA plasmid with genes for pilus
Hfr x F-: transfer of plasmid and chromosome genes after plasmid incorporation
Transposition
Segments of DNA jump from one location to another. Genes can be transferred from plasmid to chromosomes and vice versa
Flanking DNA can be transferred as well
Transduction
Generalized
Specialized
Packaging event: Bacterial DNA packaged into lytic phage by accident
Excision event: Flanking regions around bacterial DNA is put into a Lysogenic phage
Genes encoded in lysogenic phage
“ABCDE”
shigA-like toxin
Botulinum toxin, Cholera toxin, Diphtheria toxin, Erythrogenic toxin of Strep pyogenes
