Micro 1 USMLE Flashcards
alcoholic vomits gastric contents and develops foul smelling sputum. What organisms are most likely
anaerobes
middle age male presents w/ acute onset monoarticular joint pain and bilateral bell’s plalsy. What is the likely dz and how did he get it
lyme dz; bite from Ixodes tick
Pt w/ mycoplasma pneumoniae exhibits cryoagglutins during recovery phase. What types of immunoglobulins are reacting
IgM
UA of pt shows WBC casts. What is the dx?
pyelonephritis
young child presents w/ tetany and candidiasis. Hypocalcemia and immunosuppression are found. What cell is deficient?
T cell (DiGeorge)
pt presente w/ “rose gardener’s” scenerio (thorn prick w/ ulcers olong lymphatic drainage. What is the infectious bug.
sporothrix schencki
25 y/o medical student has a burning feeling in his gut after meals. bx of gastric mucosa shows gram negative rods. what is the likely organism?
H pylori
32 yo male has “cauliflower” skin lesions. Tissue bx shows broad based budding yeast. What organism is most likely?
blastomyces
breast feeding woman suddenly develops redness and swelling of her right breast. On examination it is found to be afluctuant mass. What is the dx?
mastitis caused by S. aureus
Young child has recurrent lung infections and granulomatous lesions. What is the defect in neutrophils?
NADPH oxidase (chronic granulomatous dz)
20 y/o college student presents w/ lymphadenopathy, fever, and hepatosplenomegaly. His serum agglutinates sheep RBCs. What cell is infected?
B cell (EBV; infectious mononucleosis)
One hour after eating custard at a picnic, a whole family began to vomit. After 10 hours, they were better. What is the organism?
S. aureus (produces preformed enterotoxin)
infant becomes flaccid after eating honey. What organism is implicated, and what is the mechanism of action.
Clostridium botulinum; inhibited release of ACh.
Man presents with squamous cell carcinoma of the penis. He has exposure to what virus?
HPV
Pt develops endocarditis three weeks after receiving a prosthetic heart valve. What organism is suspected?
S. aureus or S. epidermidis
55 y/o man who is a smoker and heavy drinker presents with a new cough and flulike symptoms. Gram stain shows no organisms; silver stain of sputum shows gram-negative rods. What is the dx?
legionella pneumonia
after taking clidamycin, pt develops toxic megacolon and diarrhea. What is the mechanism of diarrhea
C. difficile overgrowth
this bacterial structure is composed of a sugar backbone with cross linked peptide side chains. It functions to give the bacterium rigid support, and to protect against osmotic pressure
peptidoglycan
This bacterial structure is composed of teichoic acid which induces TNF and IL-1. It functions as a major surface antigen.
cell wall/membrane in gram postitives
this bacterial structure is composed of lipid A which induces TNF & IL-1. Polysaccharide is the antigen. It functions as a major surface Ag and a site of endotoxin.
outer membrane of gram negative
what is the endotoxin of Gram negative bacteria
lipopolysaccaride
this bacterial structure is composed a plasma bilayer. It fxs as a site of oxidative and transport enzymes.
Plasma membrane
This bacterial structure is composed RNA and protein in 50S and 30S subunits. It functions as the site of protein synthesis.
ribosome
this bacterial structure is composed of many hydrolytic enzymes, including B-lactamases. It is the space between the cytoplasmic membrane and outer membrane in gram negative bacteria.
Periplasm
this bacterial structure is composed polysaccaride and protects against phagocytosis.
capsule.
the capsule of bacillus anthracis is unique in that it contains _________ instead of polysaccharide.
D-glutamate
This bacterial structure is composed of glycoprotein. It functions to mediate adherence of bacteria to cell surface.
pilus/fimbrae
sex pilus forms attachment between 2 bacteria during _______
conjugation
this bacterial structure is composed of protein and fxs in motility
flagellum
this bacterial structure is composed of a keratin-like coat and dipicolinic acid. It provides resistance to dehydration, heat, and chemicals.
spore
this bacterial structure is composed DNA. It contains a variety of genes for antibiotic resistance, enzymes, and toxins.
plasmid
This bacterial structure is composed of polysaccharide. It mediates adherence to surfaces, especially foreign surfaces (e.g., indwelling catheters).
Glycocalyx
in the bacterial growth curve this is the part where there is metabolic activity without division
lag
in the bacterial growth curve this is the part where there is rapid cell division
log
in the bacterial growth curve this is the part where nutrient depletion slows growth
stationary
in the bacterial growth curve this is the part where there is prolonged nutrient depletion and buildup of waste products.
death
what is the source of exotoxins
some G+ & G- bacteria
what is the source of endotoxins
cell wall of most G- bacteria and listeria
are exotoxins secreted from the cell
yes
are endotoxins secreted from the cell
no
exotoxins are made of _______
polypeptides
endotoxins are made of _____
lipopolysaccharides
genes for exotoxins are located where?
plasmid or bacteriophage
genes for endootoxins are located where?
bacterial chromosomes
how toxic are exotoxins
high (fatal dose is on the order of 1 ug)
What is the toxicity of endotoxins?
low (fatal dose is on the order of hundreds of micrograms)
what are the clinical effects of endotoxins?
fever & shock
what is cytokines are involved in the mode of action of endotoxins
TNF & IL1
high-titer antibodies called antitoxins can be used against these toxins
exotoxins
this toxin poorly antigenic
endotoxins
these are used as vaccines for exotoxins
toxoids
is there a vaccine available for endotoxins
no
what is more heat stable, endotoxins or exotoxins
endotoxins
what is the only exotoxin that is heat stable
staphylococcal enterotoxin
tetanus, botulism, & diphtheria typically cause problems due to ________ (exotoxin or endotoxins)
exotoxins
meningococcemia, causes sepsis by G- rods. Toxicity is due to ________ (exotoxin or endotoxins)
endotoxins
these binds directly to MHC II and T-cell receptor, activating large numbers of T cells to stimulate release of IL-1 & IL-2
superantigens
TSST-1 from this bug causes toxic shock syndrome (fever, rash, shock).
S. Aureus
Enterotoxins from this bug cause food poisoning.
S. Aureus
Scarlet fever-strain SPE SPE toxin from this bug causes toxic shock-like syndrome.
S. pyogenes
this exotoxin interferes with host cell fx. It has a B component and an A component.
ADP ribosylating A-B toxins.
tell me about the B component of ADP ribosylating A-B toxins
B (binding) component binds to receptor on surface of host cell, enaboling endocytosis)
tell me about the A component of ADP ribosylating A-B toxins
A (active) component attaches an ADP-ribosyl to a host cell protien (ADP ribosylation), altering protein fx.
What bugs have ADP ribosylating A-B toxins (4)
Corynebacteria diptheria
Vibrio cholerae
E. Coli
Bordetella Pertussis
What bugs have superantigins (2)
S. aureus
S. pyogenes
this bug has an ADP ribosylating A-B toxin that inactivatess elongation factor (EF-2) causing a pharyngitis and a “pseudomembrane” in the throat
Corynebacterium diptheriae
This bugs ADP ribosylating A-B toxin acts on the G protein to stimulate adenylyl cyclase, increasing pumping of Cl- & H2O in the gut causing voluminous rice-water diarrhea.
Vibrio cholerae
This bug has a heat-labile ADP ribosylating A-B toxin, that stimulates adenylyl cyclase (cholera-like mechanism), causing watery diarrhea. Heat stabile toxin stimulates guanylate cyclase.
E. Coli