USMLE - Micro Basic

Sugar backbone with peptide side chains cross linked by transpeptidase
Support. Protects against osmotic pressure

Cell wall of Gram+
Induces TNF and IL1

Endotoxin

Outer membrane of Gram-

Major Surface Ag

Lipid A (induces TNF and IL1)

O polysaccharide is the antigen

Space between cytoplasmic membrane outer membrane
Gram-
Hydrolytic enzymes include β lactamase

Polysaccharides (except in Bacillus anthracis which contains D-glutamate)
Protects against phagocytosis

Glycoprotein
Mediates adherence of bacteria to cell surface. Sex pilus for conjugation

Protein
Motility

Keratin-like coat, Dipicolinic acid, Peptidoglycan
Resistance to heat, chemicals, dehydration

Polysaccharide
Mediates adherence to surfaces (especially foreign surfaces)

+
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

Membrane contains sterols and have no cell walls

Contains mycolic acid with high lipid content

“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)

“Certain Bugs Really Try my Patience”
Chlamydia, Borrelia, Rickettsiae, Trypanosomes, Plasmodium

Periodic Acid Schiff Base
“PASs the sugar”
Glycogen, Mucopolysaccharides
Diagnoses Whipple’s Disease (Tropheryma Whipplei)

Carbol Fuchsin
Acid Fast organisms (Nocardia, Mycobacterium)

Cryptococcus neoformans
Mucicarmine can also be used to stain thick polysaccharide capsule red

Fungi, Legionella, Helicobacter pylori

Chocolate agar with factor V (NAD) and X (hematin)

Thayer-Martin (or VPN) media
Vancomycin (inhibits Gram+ organisms), Polymyxin (inhibit Gram- organisms except Neisseria), Nystatin (inhibits fungi)

“Bordet for Bordetella)
Bordet-Gengou (potato) agar

Tellurite plate, Loffler’s media

Lowenstein Jensen agar

Eton’s agar

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

Charcoal yeast extract on agar buffered with cysteine and iron

"Sab's a Fun Guy"

| Sabouraud's agar

"Nagging Pests Must Breathe"

| Nocardia, Pseudomonas aeruginosa (can use nitrates in anaerobic environment), Mycobacterium tuberculosis, and Bacillus

"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

"Stay inside when its Really Cold"
Rickettsia, Chlamydia
Can't make their own ATP

"Some Nasty Bugs May Live FacultativeLY"

| Salmonella, Neisseria, Brucella, Mycobacterium, Listeria, Francissela, Legionella, Yersinia pestis

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

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

T cells not activated because polysaccharides cannot be presented

Conjugate to a protein to promote T cell activation and class switching

Polysaccharide vaccine w/o conjugated protein against pneumococcus

Conjugated Polysaccharide vaccine against pneumococcus

Conjugated vaccine

Conjugated vaccine

"CHuck norris hates PUNKSS"

| Cryptococcus, H pylori, Proteus, Ureaplasma, Nocardia, Klebsiella, S epidermidis, S saprophyticus

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)

Binds Fc of Ig to prevent opsonization and phagocytosis

| S aureus

Cleaves IgA
"SHiN"
S pneumoniae, H influenzae B, Neisseria
Respiratory mucosa

Prevents phagocytosis

| GAS

Gram+ and Gram-

Secreted from cells

Polypeptide

Plasmid or Bacteriophage

Highly toxicity

Induces high titer Abs called antitoxins
Toxoids used as vaccines
Destroyed rapidly at 60 degrees (except for Staphylococcal enterotoxin)
Tetanus, Botulism, Diphtheria

Outer cell membrane of most Gram-

Not secreted

Lipopolysacharide (structural part of bacteria released when lysed)

Bacterial chromosome

Low toxicity

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

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)

Exotoxin
Exotoxin A
ADP ribosylating A-B toxin: Inactivates Elongation Factor (EF2) thus inhibiting protein synthesis
Host cell death

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

Exotoxin
Shiga Toxin (ST)
Inactivates 60S ribosome by removing adenine from rRNA inhibiting protein synthesis
GI mucosal damage --> dysentery. Enhances release of cytokines --> HUS

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

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"

Exotoxin
Edema Factor
Mimics AC and increases cAMP
Responsible for characteristic edematous borders of black eschar in cutaneous anthrax

Exotoxin
Cholera toxin
ADP ribosylating A-B toxin: Permanently activates Gs --> Overactivates AC --> ↑cAMP --> ↑Cl secretion in gut and water efflux
Rice water diarrhea

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

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

Exotoxin

Botulinum toxin

Cleaves SNARE protein required for NT release of ACh from neurons

Flaccid paralysis, floppy baby

Honey

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)

Exotoxin
Streptolysin O
Degrades cell membranes
Lyses RBCs (contributes to β hemolysis and host produces ASO used to diagnose RF)

Exotoxin
Toxic Shock Syndrome Toxin (TSST1)
Brings together MHCII and TCR to cause release of IFNγ and IL2 --> shock
TSS: fever, rash, shock

Exotoxin
Exotoxin A
Brings together MHCII and TCR to cause release of IFNγ and IL2 --> shock
TSS: fever, rash, shock

LPS --> Macs --> IL1 (fever), TNF (fever hypotension), NO (hypotension)
LPS --> complement --> C3a (hypotension, edema), C5a (neutrophil chemotactic)
LPS --> tissue factor --> coagulation cascade --> DIC

"ENDOTOXIN"

| Edema, NO, DIC/Death, Outer membrane, TNFα, O Ag, eXtremely heat stable, IL1, Neutrophil chemotaxis

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

Cephalosporins and Penicillins becuase they act on peptidoglycan synthesis

Take up DNA from surroundings
"SHiN"
S pneumoniae, H influenzae, Neisseria

F+ x F-: dsDNA plasmid with genes for pilus

| Hfr x F-: transfer of plasmid and chromosome genes after plasmid incorporation

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

Packaging event: Bacterial DNA packaged into lytic phage by accident
Excision event: Flanking regions around bacterial DNA is put into a Lysogenic phage

"ABCDE"
shigA-like toxin
Botulinum toxin, Cholera toxin, Diphtheria toxin, Erythrogenic toxin of Strep pyogenes