My Micro Part 1, USMLE Flashcards
Bacterial structure: Rigid support
Peptidoglycan
Bacterial structure: Major surface antigens (2)
1) Cell wall
2) Outer membrane (G-)
Bacterial structure: Protects against osmotic pressure
Peptidoglycan
Bacterial structure: Site of oxidative and transport enzymes
Plasma membrane
Bacterial structure: Site of endotoxin
Outer membrane (G-)
Bacterial structure: Space between the cytoplasmic membrane and outer membrane in G-
Periplasm
Bacterial structure: Site of lipopolysaccharide
Outer membrane (G-); aka endotoxin
Bacterial structure: Mediate adherence of bacteria to cell surface
Pilus/fimbria
Bacterial structure: Motility
Flagellum
Bacterial structure: Resistant to dehydration, heat, and chemicals
Spore
Bacterial structure: Forms attachment between 2 bacteria during conjugation
Sex pilus
Bacterial structure: Contains genes for antibiotic resistance, enzymes, and toxins
Plasmid
Bacterial structure: Adherence to surfaces, especially foreign surfaces (e.g. indwelling catheters)
Glycocalyx
Bacterial structure: Sugar backbone with peptide side chains cross- linked by transpeptidase
Peptidoglycan
Bacterial structure: Lipoteichoic acid
Cell wall
Bacterial structure: Lipid A
Outer membrane (G-)
Bacterial structure: O polysaccharide
Outer membrane (G-)
Bacterial structure: Phospholipid bilayer
Plasma membrane
Bacterial structure: Contains hydrolytic enzymes, including beta lactamases
Periplasm
Bacterial structure: Component of pilus/fimbria
Glycoprotein
Bacterial structure: Component of flagellum
Protein
Bacterial structure: Components of spore
1) Dipicolinic acid
2) Peptidoglycan
Bacterial structure: Keratin-like coat
Spore
Bacterial structure: DNA
Plasmid
Bacterial structure: Component of capsule
Organized discrete polysaccharide layer EXCEPT B. anthracis
Subunits of bacterial ribosome
30S and 50S
Substances induced by exposure to major surface antigens
TNF and IL-1
Component of cell wall that induces TNF and IL-1
Lipoteichoic acid
Component of outer membrane (G-) that induces TNF and IL-1
Lipid A
Antigen of outer membrane (G-)
O polysaccharide
Component of capsule of B. anthracis
D-glutamate (a polypeptide, not polysaccharide)
Bacterial structure: Composed of loose network of polysacharides
Glycocalyx
Bacterial structure: Unique to G+
Lipoteichoic acid
Bacterial structure: Unique to G-
1) Outer membrane
2) Porin on outer membrane
3) Periplasmic space
G+ rods
1) Bacillus
2) Clostridium
3) Corynebacterium
4) Gardnerella (Gram variable)
5) Lactobacillus
6) Listeria
7) Mycobacterium
8) Propionibacterium
G- zoonotic rods
- ELLAs
1) Batonella
2) Brucella
3) Francisella
4) Pasteurella
Branching filamentous G+ bacteria
1) Actinomyces
2) Nocardia
Weakly acid fast bacteria
Nocardia
Bacteria: Giemsa
Certain Bugs Really Try my Patience
1) Chlamydia (pleomorphic)
2) Borrelia (spirochete)
3) Rickettsia (pleomorphic)
4) Trypanosomes
5) Plasmodium
Bacteria without cell wall
1) Mycoplasma
2) Ureaplasma
Component of membrane of mycoplasma and ureaplasma
Sterols
Component of mycobacterial cell wall responsible for acid fast staining
Mycolic acids
Component of acid fast staining that stains my colic acid
Carbolfuchsin
Means of identification/staining of T. pallidum
1) Dark-field microscopy
2) Fluorescent antibody staining
Bacteria: Lacks classic peptidoglycan because of low muramic acid, rendering beta lactam antibiotics less effective
Chlamydia
Bacteria: PAS
Tropheryma whipplei (Whipple disease)
Bacteria: Ziehl-Neelsen
1) Mycobacteria
2) Nocardia
3) Cryptosporidium oocysts (protozoa)
Bacteria: India ink
Cryptococcus neoformans
Bacteria: Silver stain
1) Fungi (P. jiroveci)
2) Legionella
3) H. pylori
Substance stained by PAS
[PASs the sugar]
Glycogen and mucopolysaccharides
Alternative to Ziehl-Neelsen staining
Auramine-rhodamine stain (inexpensive but less specific)
Alternative to india ink
Mucicarmine
Mucicarmine stains the polysaccharide capsule of C. neoformans what color?
Red
Culture medium/media: H. influenzae
Chocolate agar
Culture medium/media: N. gonorrhea/N. meningitidis
Thayer-Martin
Culture medium/media: B. pertussis
1) Bordet-Gengou
2) Regan-Lowe
Culture medium/media: C. diphtheriae
1) Tellurite agar
2) Loffler medium
Culture medium/media: M. tuberculosis
Lowenstein-Jensen
Culture medium/media: M. pneumoniae
Eaton agar
Culture medium/media: E. coli
EMB
Culture medium/media: Legionella
Charcoal yeast extract agar buffered with cysteine and iron
Culture medium/media: Fungi
Sabouraud agar
Media content: CAP (esp. for H. influenzae)
1) Factor V (NAD)
2) Factor X (hematin)
Media content: Thayer-Martin, inhibits G+
Vancomycin
Media content: Thayer-Martin, inhibits G- except Neisseria
Colistin
Media content: Thayer-Martin, inhibits fungi
Nystatin
Media content: Thayer-Martin
[Very Typically Cultures Neisseria]
1) Vancomycin
2) Trimethoprim
3) Colistin
4) Nystatin
Media content: Bordet-Gengou
Potato
Media content: Regan-Lowe
1) Charcoal
2) Blood
3) Antibiotic
Media content: Eaton agar (esp. for M. pneumoniae)
Cholesterol
Use an O2-dependent system to generate ATP
Aerobes
Aerobes
[Nagging Pests MustBreathe]
1) Nocardia
2) Pseudomonas
3) MycoBacterium tuberculosis
Triggers for reactivation of M. tuberculosis
1) Immunocompromise
2) TNF-alpha inhibitor use
Generally foul smelling (short-chain fatty acids), are difficult to culture, and produce gas in tissue (CO2 and H2); normal flora in GIT
Anaerobes
Anaerobes
[Frankly Can’t Breathe Air]
1) Fusobacterium
2) Clostridium
3) Bacteroides
4) Actinomyces
Anaerobes lack these enzymes, making them susceptible to oxidative damage
1) Catalase
2) Superoxide dismutase
Antibiotics that are ineffective against anaerobes because they require O2 to enter bacterial cell
AminO2glycosides
Rely on host ATP for survival
Obligate intracellular bacteria
Obligate intracellular bacteria
[Really CHilly and COld]
1) Rickettsia
2) Chlamydia
3) Coxiella
Facultative intracellular bacteria
[Some Nasty Bugs May Live FacultativeLY]
1) Salmonella
2) Neisseria
3) Brucella
4) Mycobacteria
5) Legionella
6) Francisella
7) Listeria
8) Yersinia pestis
Significance of spleen in ridding of encapsulated bacteria
Opsonized bacteria are cleared by spleen
Vaccines given for asplenics
1) S. pneumoniae
2) H. influenzae
3) N. meningitidis
T/F A polysaccharide antigen (capsule) alone can be presented to T cells, promoting T cell activation and subsequent class switching
F, conjugated to a carrier protein, enhancing immunogenicity
Pneumococcal polysaccharide vaccine with no conjugated protein
Pneumovax
Urease-positive organisms
[CHuck norris hates PUNKSS]
1) Cryptococcus
2) H. pylori
3) Proteus
4) Ureaplasma
5) Nocardia
6) Klebsiella
7) S. epidermidis
8) S. saprophyticus
Disease associated with recurrent infections with catalase (+) organisms
CGD
Enzyme deficient in CGD
NADPH oxidase
Pigment-producing bacteria: Yellow granules
Actinomyces israelii
Bacterial components that promote evasion of host immune response
Virulence factors
Virulence factor: Binds Fc region of IgG, preventing opsonization and phagocytosis
Protein A
Virulence factor: Secreted by SHiN to colonize respiratory mucosa
IgA protease
Virulence factor: Shares similar epitopes to human cellular proteins (molecular mimicry); possibly underlies the autoimmune response seen in acute rheumatic fever
M protein
Virulence factor: Needle-like protein appendage facilitating direct delivery of toxins from certain gram-negative bacteria to eukaryotic host cell
Injectisome aka type III secretion system
Bacteria: Protein A
S. aureus
Bacteria: M protein
GABHS
Exotoxin vs endotoxin: Gram-positive and gram- negative bacteria
Exotoxin
Exotoxin vs endotoxin: Secreted from cell
Exotoxin
Exotoxin vs endotoxin: Polypeptide
Exotoxin
Exotoxin vs endotoxin: LPS
Endotoxin
Exotoxin vs endotoxin: Encoded in plasmid or bacteriophage
Exotoxin
Exotoxin vs endotoxin: Encoded in bacterial chromosome
Endotoxin
Exotoxin vs endotoxin: High toxicity, low fatal dose
Exotoxin
Exotoxin vs endotoxin: Low toxicity, high fatal dose
Endotoxin
Exotoxin vs endotoxin: Fever, shock, DIC
Endotoxin
Exotoxin vs endotoxin: Induces antibodies called antitoxins (antigenic)
Exotoxin
Exotoxin vs endotoxin: Poorly antigenic
Endotoxin
Exotoxin vs endotoxin: Toxoids used as vaccines
Exotoxin
Exotoxin vs endotoxin: No toxoids or vaccines available
Endotoxin
Exotoxin vs endotoxin: Stable at 100C for 1 hour
Endotoxin
Exotoxin vs endotoxin: Destroyed rapidly at 60C
Exotoxin
Exotoxin vs endotoxin: Meningococcemia
Endotoxin
Heat stable enterotoxin
Staphylococcal enterotoxin
Toxin and bacteria: Inactivate elongation factor (EF-2)
1) Diphtheria toxin, C. diphtheriae
2) Exotoxin A, P. aeruginosa
Toxin and bacteria: Inactivate 60S ribosome
1) Shiga toxin, Shigella spp
2) Shiga-like toxin, EHEC O157: H7
Toxin and bacteria: Overactivates adenylate cyclase (increases cAMP) > increases Cl− secretion in gut and H2O efflux
Heat-labile toxin (LT), ETEC
[Labile in the Air (Adenylate cyclase), Stable in the Ground (Guanylate cyclase)]
Toxin and bacteria: Overactivates guanylate cyclase (increases cGMP) > decreases resorption of NaCl and H2O in gut
Heat-stable toxin (ST), ETEC
[Labile in the Air (Adenylate cyclase), Stable in the Ground (Guanylate cyclase)]
Toxin and bacteria: Mimics the adenylate cyclase enzyme (increases cAMP)
Edema toxin, B. anthracis
Toxin and bacteria: Overactivates adenylate cyclase (increases cAMP) by permanently activating Gs > increases Cl− secretion in gut and H2O efflux
Cholera toxin, V. cholerae
Toxin and bacteria: Overactivates adenylate cyclase (increases cAMP) by disabling Gi, impairing phagocytosis to permit survival of microbe
Pertussis toxin, B. pertussis
Toxin and bacteria: Proteases that cleave SNARE
1) Tetanospasmin, C. tetani
2) Botulinum toxin, C. botulinum
Toxin: GI mucosal damage > dysentery
Shiga toxin
Toxin: HUS
1) Shiga toxin
2) Shiga-like toxin
Toxin: Edematous borders of black eschar
Edema toxin of cutaneous anthrax
Toxin: 100-day cough in adults
Pertussis toxin
Toxin: Target Renshaw cells
Tetanospasmin
Toxin: Target NMJ cells
Botulinum toxin
Toxin: Prevents release of inhibitory (GABA and glycine)
Tetanospasmin
Toxin: Prevents release of stimulatory (ACh) signals
Botulinum toxin
Toxin: Spastic paralysis
Tetanospasmin
Toxin: Flaccid paralysis
Botulinum toxin
Toxin, bacteria: Phospholipase (lecithinase) that degrades tissue and cell membranes
Alpha toxin, C. perfringens
Toxin, bacteria: Protein that degrades cell membrane
Streptolysin O, S. pyogenes
ADP ribosylating A-B toxins
1) Diphtheria toxin
2) Exotoxin A
3) Shiga toxin
4) Shiga-like toxin
5) Heat-labile toxin
6) Edema toxin
7) Cholera toxin
8) Pertussis toxin
9) Tetanospasmin
10) Botulinum toxin
T/F EHEC invades host cells
F
Toxin, bacteria: Binds to MHC II and TCR outside of antigen binding site to cause overwhelming release of IL-1, IL-2, IFN-γ, and TNF-α > shock
1) TSST-1, S. aureus
2) Exotoxin A, S. pyogenes
Manifestations of alpha toxin
1) Myonecrosis > gas gangrene
2) Double zone of hemolysis on BAP
Toxin, bacteria: Scalded skin syndrome
Exfoliative toxin, S. aureus
Toxin: Food poisoning caused by S. aureus
Enterotoxin
Host antibodies against this toxin is used to detect rheumatic fever
Streptolysin O (ASO)
T/F ASO is responsible for post streptococcal GN
F
Ability to take up naked DNA (i.e., from cell lysis) from environment (also known as “competence”)
Transformation
Plasmid that contains genes required for sex pilus and conjugation
F+ plasmid
Sex pilus on F+ bacterium contacts F− bacterium. A single strand of plasmid DNA is transferred across the conjugal bridge (also known as the “mating bridge”)
F+ x F- Conjugation
T/F Chromosomal DNA is transferred in F+ x F-conjugation
F
Transfer of plasmid and chromosomal genes
Hfr x F- conjugation
Segment of DNA (e.g., transposon) that can “jump” (excision and reintegration) from one location to another, can transfer genes from plasmid to chromosome and vice versa.
Transposition
A “packaging” event
Generalized transduction
An “excision” event
Specialized transduction
Lytic phage infects bacterium, leading to cleavage of bacterial DNA. Parts of bacterial chromosomal DNA may become packaged in viral capsid. Phage infects another bacterium, transferring these genes.
Generalized transduction
Lysogenic phage infects bacterium; viral DNA incorporates into bacterial chromosome. When phage DNA is excised, flanking bacterial genes may be excised with it. DNA is packaged into phage viral capsid and can infect another bacterium.
Specialized transduction
Genes for these 5 bacterial toxins are encoded in a lysogenic phage
[ABCDE]
1) Shiga-like toxin
2) Botulinum toxin
3) Cholera toxin
4) Diphtheria toxin
5) Erythrogenic toxin of S. pyogenes
Differentiates staph from strep
Catalase
Staph (+)
Strep (-)
Differentiates S. aureus from S. epidermis and saprophyticus
Coagulase
S. aureus (+)
Differentiates S. epidermis from saprophyticus
Novobiocin sensitivity
Epidermidis, sensitive
Saprophyticus, resistant
Alpha hemolytic strep
S. pneumoniae
Viridans strep
Beta hemolytic bacteria
1) S. pyogenes
2) S. agalactiae
3) S. aureus
4) L. monocytogenes
Gamma hemolytic strep
Group D enterococcus (faecalis and faecium)
Group D nonenterococcus (bovis)
Differentiates S. pneumoniae from viridans strep
1) Optochin sensitivity (pneumoniae is sensitive)
2) Bile solubility (pneumoniae is bile soluble)
3) Capsule (pneumoniae has capsule)
Differentiates S. pyogenes from agalactiae
Bacitracin sensitivity (pyogenes is sensitive)
Differentiates Group D enterococcus from nonenterococcus
Growth in 6.5% NaCl (enterococcus grows)
Lancefield Group A strep
S. pyogenes
Lancefield Group B strep
S. agalactiae
Lancefield Group D strep
Enterococci and nonenterococci
Common characteristic growth of Group D streptococci
Growth in bile
Bacteria: Meningitis in newborns
1) Group B strep
2) L. monocytogenes
MRSA is resistant to
1) Methicillin
2) Nafcillin
Mechanism of resistance of MRSA
Altered PBP
Toxin and bacteria: Associated with prolonged use of vaginal tampons or nasal packing
TSST-1, S. aureus
A toxic shock– like syndrome associated with painful skin infection
S. pyogenes TSS
T/F Staphylococcal enterotoxin is preformed
T
Incubation period of S. aureus food poisoning
2-6 hours
Toxin responsible for abscess formation of S. aureus
Coagulase
Bacteria: Adherent biofilms in prosthetic devices
S. epidermidis
Bacteria: Most common cause of uncomplicated UTI in young women
E. coli
Bacteria: Second most common cause uncomplicated UTI in young women
S. saprophyticus
Bacteria: Normal skin flora that contaminates blood cultures
S. epidermidis
T/F S. aureus commonly colonizes the nares
T
S. aureus superantigen
TSST-1
Lancet-shaped, gram-positive, encapsulated diplococci
S. pneumoniae
S. pneumoniae is the most common cause of
MOPS
1) Meningitis
2) Otitis media in children
3) Pneumonia
4) Sinusitis
Bacteria: Rusty sputum
S. pneumoniae
Bacteria: Ventilator-associated pneumonia
P. aeruginosa
Bacteria: Sepsis in sickle cell disease and splenectomy
S. pneumoniae
T/F S. pneumoniae is non-virulent without capsule
T
Bacteria: Normal flora of oropharynx that cause dental caries
Viridans, S. mutans
[Viridans live in the MOUTH because they are not afraid op-to-chin (of-the-chin)]
Bacteria: Normal flora of oropharynx that cause subacute bacterial endocarditis at damaged heart valves
Viridans, S. sanguinis
Bacteria: Erysipelas
S. pyogenes
Bacteria: Scarlet fever
S. pyogenes
Bacteria: Colonizes vagina and may cause pneumonia, meningitis and sepsis in babies
S. agalactiae
Bacteria: Club-shaped
C. diphtheriae
Bacteria: TSS-like syndrome
S. pyogenes
Bacteria: Necrotizing fasciitis
S. pyogenes
Bacteria: Produces CAMP factor, which enlarges the area of hemolysis formed by S. aureus
S. agalactiae
Bacteria: PYR (+)
S. pyogenes
Criteria for rheumatic fever
Jones criteria
Major criteria for rheumatic fever
JONES
1) Joints
2) Carditis
3) Nodules
4) Erythema marginatum
5) Sydenham chorea
More commonly precedes post streptococcal GN: Impetigo vs pharyngitis
Impetigo
Bacteria: Sandpaper-like texture of skin
S. pyogenes (scarlet fever)
Bacteria: Strawberry tongue
S. pyogenes (scarlet fever)
Bacteria: Hippurate (+)
S. agalactiae