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127 Cards in this Set
- Front
- Back
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What is the function of peptidoglycan in the bacterial cell wall?
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Gives rigid support as well as protects against osmotic pressure changes.
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What is the peptidoglycan cell wall made of?
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A sugar backbone with crosslinked peptide side chains.
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What organisms express Teichoic acid? What does it do?
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Teichoic acid is only found on gram positive organisms and induces acute-phase reaction caused by the secretion of IL-1, IL-6, and TNF
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What organisms express endotoxin? Where is it found?
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Endotoxin is found on the outer membrane of gram negative bugs.
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What portion of LPS is the toxin and what portion is antigenic?
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Lipid A is the toxin that stimulates IL-1 and TNF
The polysaccharide portion is antigenic. |
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What ribosome subtypes are found in eukaryotic and prokaryotic organisms?
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Pro: 30S and 50S
Eu: 40S and 60S |
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Where can lytic enzymes like Beta-lactamases be found (cell structure)?
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Periplasm
Between the cell membrane and outer membrane of gram negative bugs. |
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Capsulated bugs are protected against __________.
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Phagocytosis
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What organism has a unique capsule? What is it made of? What do all others have?
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B. anthracis has a D-glutamate cell wall. All other capsule are made of polysaccharide
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What structure mediates the adherence of bacteria to cell surfaces?
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Pili / fimbria
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What structure forms between bacteria during conjugation?
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F-pilus (sex)
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What is the purpose of spore formation? What is the spore coat made of?
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Spores provide resistance to dehydration, heat and chemicals. They are covered by a keratin-like coat and have dipicolinic acid.
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What bacterial species are capable of forming spores?
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Bacillus
Clostridium |
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What structure allows bacteria to adhere to foreign structures such as a catheter?
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Glycocalyx which is a polysaccharide structure
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Which bacteria are known to be branching and filamentous? Are they gram positive or negative?
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Gram positive
Actinomyces Norcardia |
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What is unique about the cell wall and membrane structures of mycoplasma and mycobacteria?
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Mycoplasma: Contains sterols and no cell wall.
Mycobacteria: Contains mycolic acid and a high lipid content. |
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Which bugs do not gram stain? Why?
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These Rascals May Microscopically Lack Color.
Treponema: Too thin Rickettsia: Intracellular Mycobacteria: Acid Fast Mycoplasma: No cell wall, too small Legionella: Intracellular Chlamydia: Intracellular, no muramic acid, very small |
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What technique is used to visualize Treponema?
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Dark field and fluorescent staining
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How is legionella visualized?
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Silver stain
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What stain could be used to diagnose Whipple's disease? What causes it?
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periodic acid-Schiff stain to visualize Tropheryma whippelii
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What stain can be used to visualize glycogen or polysaccharides?
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PASs the sugar
PAS- periodic acid-Schiff |
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What stain is used for Cryptococcus infections?
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India ink
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What is silver stain used for?
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PCP
Fungi Legionella |
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What bug requires chocolate agar with factors V and X?
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H. influenza
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What type of agar is used to grow Neisseria?
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Thayer-Martin or VPN (Vancomycin, Polymixin, Nystatin) to inhibit gram +, other gram - and fungi.
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What are the components of MacConkey's agar? What is it used to grow? What will colonies look like?
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Lactose
Bile salts Crystal violet Neutral red Used to grow gram negative bugs. Lactose fermenters will appear as red colonies. White colonies are non-lactose fermenters. |
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What infection might flare and appear in the upper lobes of the lung following anti-TNF drugs?
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TB
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What bacteria are obligate aerobes?
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Nagging Pests Must Breathe.
Norcardia Pseudomonas Mycobacterium Bacillus |
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What are the obligate anaerobes?
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Can't Breathe Air
Clostridium Bacteroides Actinomyces |
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Which antibiotics are ineffective against anaerobes?
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AminOglycosides - O for oxygen
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What bugs are obligate intracellular? Why?
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Rickettsia and Chlamydia are obligate intracellular bugs because they cannot make ATP.
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What is the purpose of the quellung reaction?
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To identify if organism has a capsule. If present, capsule will swell.
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In the event a pt has no spleen, what organisms must the pt be vaccinated against?
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Capsulated organisms:
(Kapsules Shield SHiN) Klebsiella pneumo Salmonella Strep pneumo HiB N. Meningitidis |
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What do capsulated organisms have in common?
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IgA protease
Cause meningitis Undergo transformation |
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How is the bacterial capsule beneficial to vaccine formation?
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Capsular polysaccharides (which are antigenic) can be conjugated with protein structures to increase T-cell response and immunity.
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What is the pigment of pseudomonas colonies?
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Blue-green
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What are the urease-positive bugs?
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Particular Kinds Have Urease
Proteus Klebsiela H. pylori Ureaplasma |
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What is the mechanism of protein A as expressed by S. aureus?
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Binds Fc of Ig and prevents opsonization and phagocytosis.
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What is the function of M protein as expressed by group A strep?
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Blocks phagocytosis
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What bugs have endotoxin?
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Most gram negatives and Listeria
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What bugs have exotoxin?
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Some gram positives and gram negatives
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Is exotoxin excreted?
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Yes
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Is endotoxin excreted?
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No
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What is endo and exotoxin made of?
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Endotoxin: LPS
Exotoxin: Protein |
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What is the difference in genetic location of endotoxin and exotoxin?
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Exotoxin can be transferred via plasmid or phage
Endotoxin is coded into the bacterial chromosome |
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Which is more potent exotoxin or endotoxin?
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Exotoxin
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Which is more antigenic exotoxin or endotoxin?
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Exotoxin
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Which has clinical use, endotoxin or exotoxin? How?
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Exotoxins form toxoids and can be used to created vaccines.
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Which is stable at 100C for over an hour?
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Endotoxin
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Are tetanus, botulism, and diphtheria caused by endotoxin or exotoxins?
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Exotoxins
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Fever and shock following a gram negative rod sepsis is due to _________.
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Endotoxin release
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What is a superantigen?
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Antigen that binds directly to MCH II and T-cell receptor simultaneously causing a massive activation of T-cells and IFN-gamma and IL-2 secretion.
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What are two common superantigens?
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TSST-1 from S. aureus.
Erythrogenic/pyrogenic toxin from S. pyogenes. |
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What organism and toxin causes "scalded skin syndrome"?
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S. aureus release of exfoliatin toxin
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How does S. aureus cause food poisoning?
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Release of enterotoxin
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What organism causes Scarlet fever?
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S. pyogenes
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What is the mechanism of ADP ribosylating AB toxin?
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B structure binds the cell allowing it to be endocyted. A structure will add ADP-ribosyl to the host cell proteins, fucking protein function.
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What bug can inactivate EF2 elongation factor? Why is it lethal? What is the characteristic lesion?
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C. diphtheriae (also pseudomonas exotoxin A)
Can be lethal due to inhibition of protein synthesis in the heart and neurons. Characteristic diphtheria is a pseudomembranous pharyngitis. |
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What bugs cause rice-water stool? Why (explain mechanism)?
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V. Cholera and Heat-Labile E. coli toxin are able to cause ADP-ribosylate the Gs protein causing adenylyl cyclase activation. This increases pumping of Cl into the gut with a decrease in Na absorption. Na and water move together--causing voluminous rice-water diarrhea.
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What organism releases heat labile and heat stabile toxin? What is the difference in mechanism?
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E. coli
HL: adenylyl cyclase activation HS: guanylate cyclase activation Both give the same result: watery diarrhea. |
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What is the mechanism of pertussis toxin?
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Increase in cAMP via G-alpha-i inhibition.
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How does pertussis cause lymphocytosis?
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by inhibiting chemokine receptors
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What toxin causes gangrene?
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alpha toxin of C. perfringens
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What is the mechanism of C. tetani toxin?
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Blocks release of GABA and glycine causing tetanic paralysis
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What is the mechanism of C. botulinum toxin? What is the difference with tetani toxin?
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Botulinum toxin blocks ACh release causing CNS paralysis.
Botulinum is flaccid paralysis Tetanus is rigid paralysis |
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What organisms typically cause HUS? How?
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Shigella and E. coli O157:H7 release shiga toxin, enhancing cytokine release and causing HUS
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How does shiga toxin effect protein synthesis?
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Cleaves host rRNA, fucking the 60S ribosome (eukaryotic)
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What titer is used in the diagnosis of rheumatic fever? What does it measure?
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ASO titer
Measure the amount of Anti-streptolysin O. |
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What exotoxins are able to induce cAMP formation?
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V. cholera toxin
E. coli HL toxin Pertussis toxin Anthrax edema factor All directly induce cAMP formation, except for pertussis which blocks the inhibition causing an increase of cAMP. |
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Lipid A activates three distinct pathways. What are they?
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1. Activates macrophages
2. Activates complement (alternative pathway) 3. Activates Hageman factor (factor XII) |
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What is the Hageman factor? How is it effected by lipid A?
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Factor XII in coagulation is activated by lipid A causing DIC.
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What is the sequelae of lipid A activation of macrophages?
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IL- 1 causing fever
TNF causing fever and hemorrhagic tissue necrosis NO causing shock and hypotension |
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What is the sequelae of lipid A activation of the complement pathway?
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Production of C3a and C5a.
C3a causes hypotension and edema mediated through histamine release C5a causes neutrophil chemotaxis |
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In what growth phase are spores formed in bacteria? Why?
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Stationary phase: Immediately follows log phase growth, but now that nutrients are depleted spore formation is initiated.
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What are the 5 bacteria that secrete enterotoxin that causes GI lyte imbalances and subsequent diarrhea?
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E. coli, Vibrio cholera, staph aureus, and salmonella/shigella
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What toxins of staph aureus cause hemolysis?
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Alpha and A+B of gamma toxin
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Which toxin of staph aureus destroys leukocytes?
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Leukocidin (B+C of gamma toxin)
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Which staph aureaus toxins are responsible for the sx of food poisoning?
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enterotoxins A-E
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What is the superantigen of staph aureus and what does it cause?
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TSST-1 = toxic shock syndrome
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What could be causing a child infected with staph aureus to look as if they've been burned?
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Scalded skin Syndrome from epidermolytic/exfoliative toxin
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What causes the symptoms of scarlet fever?
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erythrogenic (skin rash/toxic shock-like) and pyrogenic (fever) toxins of strep pyogenes
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What cuases hemolysis during a strep pyogenes infection?
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Streptolysin O (oxygen labile) and S (oxygen stable)
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How do you stain pneumocystis jiroveci?
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Silver stain
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What are the characteristics of MacConkey's agar?
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Has crystal violet and bile salts to inhibit gram + growth and it's only carb is lactose with neutral red stain = lactose fermentors turn pink
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What is the method by which most antibiotic resistance is exchanged between bacteria?
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Plasmid exchange via conjugation using sex/F pili
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What skin infections can be caused by both strep pyogenes and staph aureus?
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Folliculitis, cellulitis, and impetigo (vesicles or ruptured = yellow, weeping "honeycomb" crusted lesion on kid's faces)
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What are the hallmarks of necrotizing fasciitis (as seen in strep pyogenes infection)?
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Spreads rapidly and has pain/tenderness beyond the area of redness
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What are the two autoimmune diseases initiated by a strep pyogenes infection?
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Acute glomerulonephritis and rheumatic fever
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Why are group B strep (agalactiae) infections so common in neonates? How do you prevent them?
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They're part of the normal vaginal flora in 25% of women. Screen all pregos and give Penicillin G during labor
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What are the 3 most common causes of neonatal meningitis?
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Strep B, listeria, and e.coli
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What is the most prominent organism in dental plaque? What's the issue with that?
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Viridans strep mutans. Can = subacute endocarditis after dental work in those with turbulent flow (use prophylaxis)
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What patients are most susceptible to Listeria monocytogenes infections?
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Immunocompromised (steroids, AIDs, etc) or infants/fetuses
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What CD's inhibit C9 compliment binding, protecting RBCs from lysis?
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CD 55 and 59 (=DAF)
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During antigen recombination, where does the DNA break?
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Recombination signal sequences flanking the V, D, and J coding regions
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What initiates V(D)J antigen recombination?
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Recombination Activating Gene complex (RAG 1 and 2 that recognize the RSSs - both are required for B and T cell development)
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Which cytokines activate macrophages and which inhibits macrophages?
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Activated by INFgamma (TH1), inhibited by IL 4 and 10 (TH2).
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What cytokines mediate inflammation? What are they secreted by?
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IL-1, IL-6, and TNFalpha. Secreted by monocytes and macrophages
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What cytokines are released by virally infected cells?
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INFalpha and beta
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What type of hypersensitivity is responsible for Poison ivy and contact dermatitis? What about eczema?
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Poison ivy and contact dermatitis = type IV, Eczema = type I.
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Which autoimmune diseases are primarily mediated by Type III hypersensitivity?
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SLE, RA, polyarteritis nodosa, and post-streph GN.
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What disease are you thinking if a patient has iron deficiency and hemosiderinuria due to chronic intravascular hemolysis and thrombosis?
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Paroxysmal Nocturnal Hemoglobinuria
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How do you diagnose PNH?
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Ham's Test (RBC lysis at decreased pH) or do flow cytometry to look for a decreased of CD59/55 (DAF) on RBCs
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How do you treat PNH?
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Iron, warfarin and bone marrow transplant
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What are you thinking if a mom's 3rd kid is dies in utero due to hydrops fetalis with anemia due to RBC hemolysis and jaundice?
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Erythroblastosis fetalis (maternal IgG against Rh on baby's RBCs)
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How do you prevent future problems in a Rh(-) mom who's carrying an Rh+ fetus?
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Give anti-RhD Ig at 28 weeks, at any traumatic event, and within 3 days of delivery
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What diseases have an increase in ESR?
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Any inflammation/infection/malignancy but specifically polymyalgia rheuamtica, temporal arteritis, and active RA
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What are the functions of the lymph node?
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Nonspecific filtration by macros (in the node's medulla), storage/activation of B's and T's, and antibody production
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Where are the B cells found in the lymph node? What about T cells?
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B cells are in the follicles (secondary is active), and T's are in the paracortex
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Which part of the node becomes enlarged during an extreme cellular immune response?
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The paracortex
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What does a lymphnode look like in a patient with DiGeorge syndrome?
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Underdeveloped paracortex
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What duct drains the majority of the body's lymph? What's the exception?
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Thoracic duct drains all but the right arm and right half of the head which are drained by the right lymphatic duct
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Where does the thoracic duct enter lymph back into circulation?
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At the junction of the left subclavian vein and the internal jugular
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What does the superficial inguinal lymph node drain?
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The anal canal below pectinate, scrotum, and superficial thigh
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Where does lymph from the testes drain?
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superficial and deep plexus to the para-aortic
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What drains into the superior mesenteric lymph node? What about the inferior mesenteric?
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Superior = Duodenum and jejunum. Inferior = sigmoid
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Where does the upper limb and lateral breast lymph drain?
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Axillary node
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What node does the stomach lymph drain to?
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Celiac node
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Where does the lymph from the rectum and anus above the pectinate line drain?
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Internal iliac node
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Where are the B and T cells found in the spleen?
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T's are in the periarterial lymphatic sheaths and B's are in the follicles within the white pulp
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What happens in a patient with splenic dysfunction? Why?
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You get a decrease in IgM due to a lack of APCs (macrophages) leading to a decreased in C3b opsonizaiton = increased susceptibility to encapsulated bacteria
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What bacteria are more likely to infect someone without a spleen?
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Encapsulated - S. pneumoniae, H. influenzae B, Salmonella, N. meningitidis, and Klebsiella (KS SHiN)
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What are you thinking if you see a blood smear with Target cells and nuclear remnants in the RBCs (Howell-Jolly bodies) plus thrombocytosis?
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Postsplenectomy patient
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What's the function of the thymus and where does it arise from?
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T cell differentiation and maturation. Arises from the brachial 3rd pouch (endoderm layer)
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What are the 2 types of T cell selection forces and where do they occur.
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Positive (MHC restriction) and negative (nonreactive to self) selection occur at the corticomedullary junction of the thymus.
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Where are the most immature T cells in the thymus? What are their cell markers?
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In the cortex = Cd4+ AND CD8+
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What cell types are involved in innate immunity?
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PMNs, macrophages, dendritic cells, and NK cells (activated by compliment)
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What cell types are involved in adaptive immunity?
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T's and B's (activated by antibody)
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