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184 Cards in this Set
- Front
- Back
What are Staphylococci?
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spherical gram-positive parasitic bacteria that tend to form irregular colonies that resemble grape-like clusters. Tests positive for catalase.
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Name the top 3 human pathogens in which a capsule is considered to be an important virulence determinant.
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1) Streptococcus pneumoniae
2) Neisseria meningitidis 3) Haemophilus influenzae |
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There are two bacterial components that help evade complement. What are they?
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1) Capsules prevent complement activation and help prevent phagocytosis
2) O-antigen (just for gram-negative bacteria) protects against complement and helps make the bacteria serum resistant |
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Which two medically important bacteria do not have cell walls?
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Mycoplasmas and chlamydia
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These 3 main groups of components make up the cell wall or peptidoglycan layer.
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1) N-acetylglucosamine and N-acetylmuramic acid
2) peptides for cross-linking 3) penicillin-binding proteins |
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There are three main mechanisms of penicillin resistance. Can you describe them?
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1) production and use of beta-lactamase, an enzyme that cleaves penicillin
2) alteration of the PBP so penicillin cannot bind 3) prevention of access, which can be in one of a couple ways a) penicillin gets pumped out b) the bacteria has a dense membrane that keep antibiotics from getting to the PBPs |
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Which bacteria cannot be viewed by gram staining?
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1) Mycobacteria: contain long-chain fatty (mycolic) acids and are called acid-fast. Use Ziehl-Neelsen or Kinyoun staining.
2) Many spirochetes: dark-field microscopy. 3) Mycoplasma, chlamydia have no cell wall. 4) Rickettsias, Legionella. |
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Toll-like receptors are activated in two instances in the context of bacteria. What are these instances?
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1) Flagella activate Toll-like receptor 5 (TLR-5), inducing an inflammatory response
2) LPS binds to LBP which interacts with CD14, and the LBP-CD14 complex activates a membrane protein TLR-4, resulting in the production of cytokines (IL-1 and TNF, which act synergistically to induce fever). |
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Oxygen itself is only mildly toxic, but it gives rise to two very reactive and toxic substances. What are they?
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1) hydrogen peroxide (H2O2) -- degraded to water and oxygen by an enzyme named catalase
2) superoxide anion (O2-) -- degraded by an enzyme called superoxide dismutase |
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Two bacteria can grow only inside eukaryotic cells. What are they?
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1) Rickettsia
2) Chlamydia Two important groups of obligate intracellular bacteria. These bacteria must be grown on monolayers of tissue culture cells rather than agar plates. |
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What are the three Gram-positive aerobe bacilli?
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1) Listeria
2) Bacillus 3) Corynebacteria (Think LBC, Snoop Dogg, "throw/blow it in the air") |
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This staph aureus toxin is responsible for lysing red blood cells in humans. What is the toxin, and what is its mechanism of action?
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Alpha-toxin/alpha-hemolysin/hemolysin lyses red blood cells by inserting pores into the lipid bilayer. The osmolar gradient causes ions to flow out and water to flow in, lysing the cell.
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1) What is the difference between an endotoxin and an exotoxin?
2) What type of toxin is Toxic shock syndrome toxin 1 (TSST-1)? |
Endotoxins are part of the structure of the bacteria (e.g., LPS), whereas exotoxins are secreted by the bacteria. TSST-1 is an exotoxin and also a superantigen that causes massage production of cytokines that induce shock and organ failure.
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How does coagulase work? (in the context of bacteria)
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Coagulase binds to prothrombin to form a complex that initiates the polymerization of fibrin to form a clot. The fibrin clot can help keep neutrophils away from the bacteria.
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What are common peripheral manifestations of infective endocarditis?
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1) Splinter hemorrhage
2) Conjunctival petechiae 3) Osler's nodes 4) Janeway's lesions |
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This bacteria causes a blanching rash and causes the skin to peel after it has run its course.
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staph aureus
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1) What syndrome is caused by 2) *what bacteria* is characterized by desquamation and occurs
usually in infants and children under the age of 5. Also, 3) what is the toxin that causes the syndrome? |
1) Scalded Skin Syndrome is caused by 2) Staph aureus due to 3) exfoliatin toxin
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Staph aureus is the leading cause of two things that Dr. Hauser mentioned in his lecture. What are they?
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Staph aureus is a leading cause of...
1) skin and soft tissue infections 2) hospital-acquired pneumonia (It's also a frequent cause of wound infections.) |
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This bacteria causes the common childhood sickness "strep throat," complete with: sore throat, fever, headache, swollen erythematous tonsils, sometimes with purulent exudates, cervical lymphadenopathy.
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Streptococcus pyogenes causes Streptococcal pharyngitis, which is impossible to clinically differentiate from viral pharyngitis.
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What's the difference between the toxic shock syndrome caused by staph aureus vs the one caused by streptococcus pyogenes
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A rash is rarely present in the S. pyogenes version, and it's not associated with tampon use.
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This bacteria causes necrotizing fasciitis.
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S. pyogenes
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What bacteria cause this?
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Bacillus anthracis
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What bacteria does this?
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Listeria monocytogenes
(also Rickettsia ricketsii and Shigella) |
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Listeria monocytogenes need this protein to propel themselves around the cell for invasion and such.
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ActA helps Listeria monocytogenes form and push against actin tails.
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What bacteria are present in this picture?
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Corynebacterium diphtheriae
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The lesions of this gram positive bacteria are notably resistant to neutrophils.
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Nocardia spp.
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What is the name of this physical manifestation of disease, and what is the bacterium that causes it?
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This is impetigo, a soft tissue infection of the epidermis that occurs usually in small children. It's associated with poor hygiene and begins as small vesicles on exposed areas of skin and proceeds to an enlarged pustular vesicle that ruptures to form a yellow crust. It's caused by Streptococcus pyogenes.
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What illness is related to strawberry tongue, and what is the bacterium that causes it?
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Strawberry tongue is one of the constellation of symptoms that's a part of Scarlet fever. It's caused by S. pyogenes. Other symptoms include an erythematous "sand-paper" rash that can accompany strep throat. It usually involves the face but spares areas around the mouth ("circumoral pallor").
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Gram negative bacteria have O antigens, K antigens, and H antigens. What do each of these antigens correspond to?
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O - Lipopolysaccharide (LPS)
K - capsular polysaccharides H - Flagella |
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Of the 5 types of Escherichia coli that cause diarrhea, 3 are solely noted for just being found in developing countries. Which three are those?
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eIec
ePec eAec (think In Poor nAtions) |
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Which bacteria is known to cause the plague ("The Black Death")?
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Yersinia pestis
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The swollen lymph node here is pathognomonic for which disease?
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Bubonic plague, caused by Yersinia pestis.
Bubonic plague: 2-6 day incubation period bubo develops near the site of flea bite fevers, chills, myalgias, arthralgias, and headache bubo becomes progressively enlarged, painful, and erythematous sepsis and death |
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Generally, what size are bacteria?
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Generally, 1-2 micrometers
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What is the composition of the peptidoglycan cell wall?
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Peptidoglycan (also called murein) is composed of two alternating sugars: N-acetylglucosamine(NAG)/N-acetylmuramic acid (NAM). NAG and NAM are crosslinked to form a large 3D sheet. PBPs ensure the proper cross-linking of these chains and are targeted by antibiotics like penicillin.
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Which bacteria cannot be visualized by gram stain?
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Mycobacteria (can visualize with acid-fast, Ziehl-Neelsen, or Kinyoun), and the spirochete Treponema pallidum has gram negative walls that are too thin (can visualize with dark-field microscopy). Also, Rickettsia and Legionella do not pick up gram stain.
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What are teichoic/lipoteichoic acids?
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Teichoic acids are long polymers of either glycerol phosphate or ribitol phosphate that also contain sugars and amino acids and are attached to the cell walls of gram-positive bacteria. Lipoteichoic acids are attached to the cell membrane.
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What is the region between the two membranes of gram-negative bacteria called?
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Periplasm
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What is the toxic portion of LPS (endotoxin)?
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Lipid A
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How does the O antigen help bacteria evade/get caught up with the immune system?
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O antigen protects against complement-mediated lysis, but not against specific antibodies.
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What is the only bacterium that contains sterol?
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Mycoplasma
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Which bacteria do not have cell walls?
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Mycoplasma and chlamydia do not have cell walls.
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How does vancomycin work differently from penicillin? How did bacteria work around this?
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Penicillin binds PBPs whereas vancomycin prevents crossbridges from forming by binding to the amino acids. Vancomycin-resistant bacteria worked around this by altering their last amino acid so that vancomycin couldn’t bind.
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How does lysozyme work, and where is it present?
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Lysozyme cleaves the sugar polymer backbone of peptidoglycan, and it’s present in saliva, sweat, tears, and mucous secretions.
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What non-toxin function does LPS have for Gram-negative bacteria?
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LPS forms a tight barrier that prevents many molecules, including certain antibiotics, from reaching the underlying cell wall.
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How does LPS initiate its toxic effect?
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LPS binds to LBP and the complex interacts with CD14 receptors which then interact with TLR-4 to produce cytokines like IL-1 and TNF-alpha, which are inflammatory.
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What are some important functions of bacterial capsules?
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They prevent dessication and also help prevent phagocytosis by preventing complement activation on the cell surface.
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Which 3 human pathogens are important causes of human disease and use their capsules to help mediate their virulence?
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Streptococcus pneumonia, Neisseria meningitides, and Haemophilus influenza
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What are the 3 major components of a flagella, and where does the energy come from to power the flagellar movement?
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Flagellin, hook (connects flagella to basal body in bacterial envelope), basal body (motor). Energy comes from a proton motive force, i.e. a flow of protons into the cell.
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What disease do capsules cause?
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Meningitis and bactermia and individuals without a functional spleen.
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What are three antigens used for serotyping bacteria and their corresponding bacterial structures?
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K-capsule, O-LPS O-side chain, H-flagella
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Flagella are recognized by the host via what receptor?
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TLR-5
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How big are bacterial genomes, and what is their structure?
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Bacterial genomes are between 1-8 million base pairs. Generally, bacteria have single, double-stranded circular DNA.
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Why do people constantly get reinfected with gonorrhea?
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Neisseria gonorrhoeae constantly change the antigenic make up of their pili.
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How does bacterial chromosomal replication differ from that of humans?
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Bacteria chromosomes can replicate rapidly and they can start a new round before the previous had been completed. Also, they have circular chromosomes, so they need gyrase to separate the strands.
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What are bacterial spores, and what are the medically important bacteria that can form spores (there are 2 the medically important ones)?
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Bacterial spores are highly resistant (to environmental stress e.g. heat, nutrient deprivation, etc.), metabolically inactive dormant forms of bacteria. Clostridium and Bacillus can form spores (these 2 are the medically important ones).
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Bacteria need iron for their growth. How do they get it, given iron is tightly bound to transferrin?
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They use siderophores to extract iron from transferrin and other iron-carrying molecules in the body.
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What enzyme degrades hydrogen peroxide?
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Catalase degrades hydrogen peroxide into water and oxygen.
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Which type of agar is specifically for enteric Gram-negative bacilli?
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MacConkey agar
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Two notable pathogens do not secrete siderophore. What are they, and how do they get iron?
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Neisseria meningitidis and N. gonnorrhoeae get their iron by receptors on their surfaces that bind lactoferrin and transferrin to remove iron and internalize it.
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What can one use in a micro lab to identify bacteria that don’t culture or grow in agar?
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You can use 16S rRNA PCR amplification sometimes to identify the bacterium
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Which bacteria have cytochrome c?
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Pseudomonas aeruginosa and Neisseria spp. have cytochrome c.
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What’s the difference between a lytic infection and a lysogenic infection by a bacteriophage?
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The phage lyse the host bacterium in lytic infection, whereas in a lysogenic infection, the bacterium grows and divides and passes the phage onto its progeny
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What is a pathogenicity island?
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A pathogenicity island is an integrative and conjugative element (ICE—encode information that allows them to excise from the chromosome, transfer to a different bacterium by conjugation, and integrate into the chromosome of the new bacterium) that carries a virulence factor.
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What causes hemolytic uremic syndrome (HUS)?
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In E. coli, HUS is caused by the shiga-like toxin, which is carried by a phage that infects E. coli.
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What is an integron?
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Integrons are genetic entities that capture exogenous gene cassettes and ensure their expression and are composed of 3 core components: a promoter, a primary recombination site located downstream of the promoter, and a gene encoding an integrase.
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What are the 7 toxins of Staphylococcus aureus?
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1) TSST-1: superantigen, causes fever, shock, organ failure 2) Staphylococcal enterotoxins A-E, G-I: vomiting 3) exfoliatin: scalded skin syndrome 4) alpha-toxin (alpha-hemolysin): pore-forming toxin and RBC lysis (beta hemolysis) 5) Panton-Valentine leukocidin (PVL) : pore forming toxin associated with CA-MRSA 6) Coagulase: binds prothrombin to polymerize fibrin to form a clot (fibrin capsule around abscesses) 7) protein A: binds Fc portion of IgG molecules and prevents antibody-mediated clearance
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What is the mechanism of the conferred methicillin resistance of S. aureus?
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MRSA strains contain a variant penicillin-binding protein called PBP2’ (encoded by the mecA gene) that does not bind beta-lactam antibiotics and are thus resistant to all beta-lactam antibiotics.
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How does the pattern of growth differ between Staphylococci, Streptococci, and Enterococci?
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Staphylococci grow in grape-like clusters, whereas Streptococci grow in pairs and chains, and Enterococci
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What are the hemolytic patterns for the different Streptococci?
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Alpha-hemolysis: S. pneumonia and viridans streptococci
Beta-hemolysis: S. pyogenes, S. agalactiae and others Gamma-hemoylsis: S. bovis |
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What are the determinants of pathogenicity for S. pyogenes?
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1) Streptolysin (SLO, SLS): pore-forming toxin 2) M-protein: fibrillar proteins that help evade phagocytosis 3) SPEs: A,C are superantigens, B is a protease 4) Streptokinase: lyses fibrin clots 5) C5a peptidase: cleaves complement component C5a and prevents it from recruiting phagocytes
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What is the difference between Toxic shock syndrome produced by S. pyogenes versus S. aureus?
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S. pyogenes does not have a rash and is not associated with tampon use.
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What are skin infections caused by S. pyogenes?
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Impetigo, Cellulitis, Necrotizing fasciitis
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What would you use to treat S. pyogenes?
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Penicillin works pretty well
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Where do S. agalactiae normally colonize?
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The vagina, often passed perinatally. It can cause neonatal sepsis and neonatal meningitis.
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What is a major problem with the relatively non-virulent Enterococci?
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Vancomycin resistance. It changes D-Ala-D-ala to D-ala-D-lactate.
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What disease can S. bovis cause?
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Colonic carcinoma is associated with S. bovis.
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What environment are enterococci able to thrive in that set them apart from the other Gram+ cocci?
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Enterococci can thrive in high concentrations of bile salts and NaCl.
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Where is the split caused by exfoliatin in scalded skin syndrome?
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Between stratum spinosum and stratum granulosum
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Which bacterium produces a blanching rash in its Toxic Shock Syndrome, S. pyogenes or S. aureus?
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S. aureus produces a blanching rash in its Toxic Shock Syndrome.
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What is the leading cause of hospital acquired pneumonia?
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S. aureus is the leading cause of hospital-acquired pneumonia.
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What molecule is responsible for the beta hemolysis seen in S. pyogenes on blood agar?
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Streptolysin O (SLO) is responsible for the beta-hemolysis seen on blood agar.
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What is “sand paper rash” used in reference to?
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“Sand paper rash” is used in reference to/is produced in Scarlet fever, caused by S. pyogenes. It may accompany streptococcal pharyngitis, usually involves the face but spares the area around the mouth and is accentuated in skin creases. Also, “strawberry tongue” happens.
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How are people exposed to bacillus anthracis?
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Humans are exposed to bacillus anthracis through handling of contaminated meat or hides.
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What are the two toxins that bacillus anthracis has?
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Edema factor (EF): has adenylate cyclase activity leading to increased intracellular cAMP levels, leading to edema and inhibition of neutrophil phagocytosis
Lethal factor (LF): a zinc metalloprotease that cleaves host cell kinases and causes lysis or inactivation of macrophages, dendritic cells, and suppressor T cells There is also protective antigen (PA): a septamer pore that binds to cells and facilitates the entry of EF and LF |
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What are the 3 forms of clinical disease manifested by anthrax?
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Cutaneous anthrax (spores introduced into the skin through cuts or abrasions, small red papules appear and form ulcers with blackened necrotic eschar), inhalation anthrax: (spores inhaled—fever, shortness of breath and hypotension ensue, and death follows soon after), and GI anthrax (rare in humans)
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What’s a good treatment for anthrax?
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Penicillin works pretty well.
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Is there a human vaccine for anthrax?
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A nonliving vaccine with protective antigen as its active component is used for humans.
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How is Listeria transmitted?
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Listeria is transmitted via foodborne sources (e.g., unpasteurized milk, cheeses, coleslaw, raw meat)
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What factors are important for the attachment and invasion of Listeria into mammalian cells?
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Listeria use a protein called internalin for attachment and invasion and adhesins for adherence. Listeria initially reside inside the vacuoule but escape using listeriolysin O, a pore-forming toxin similar to streptolysin O of S. pyogenes and pneumolysin of S. pneumoniae. They then use ActA to form protusions into neighboring epithelial cells and push against actin tails to evade.
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Which bacteria are aerobic, gram-positive bacilli with a “club-shape?”
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Corynebacteria, e.g. C. diphtheriae.
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What is an ADP-ribosylating toxin?
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An ADP-ribosylating toxin transfers ADP-ribose from NAD to host cell proteins, thus altering the activity of these proteins.
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Which bacteria tend to lie in clusters at acute angels with “Chinese letter” appearance?
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Corynebacterium diphtheriae
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In the clinical disease of which bacterium does the patient contract a thick, grey adherent pseudomembrane?
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Corynebacterium diphtheriae
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Which bacteria can cause cardiac arrhythmias and damage to nerves if absorbed into the circulation?
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C. diphtheriae
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What is a toxoid?
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A toxoid is a chemically treated toxin that is no longer toxic but remains immunogenicity.
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Which bacteria form terminal spores and thus have a “tennis racket” or “drumstick” shape?
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C. Tetani
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What food products is botulism associated with?
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Botulism is most often associated with home-canned food products
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How does the botulinum toxin work?
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Botulinum toxin blocks the release of acetylcholine and transmission of nerve impulses.
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What are the 3 types of botulism?
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1. food-borne botulism: symmetric descending paralysis, cranial nerve involvement such as diplopia, dysarthria, dysphagia, and occasional respiratory failure. Nausea, vomiting, and abdominal pain are common
2. wound botulism: same symptoms as food-borne botulism without GI findings 3. infant botulism |
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How do people recover from botulism?
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Recovery requires the regrowth of nerve endings, which can take months to years.
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What bacteria causes gas-gangrene in wounds and food-poisoning assicated with ingestion of contaminated meat, poultry, or legumes?
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Clostridium perfringens
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Are Nocardia aerobic or anaerobic?
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Nocardia are aerobic
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What are identifying characteristics of Actinomycetes bacteria?
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Actinomycetes form long branching filments that resemble the hyphae of fungi.
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What are clinical manifestations of Nocardia infections?
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Subacute pneumonia, nodules, cavitation, empyema (pus in the pleural space), dissemination with the CNS being the most common site.
Transcutaneous inoculation can also occur with the really messed up feet (actinomycetoma) due to walking barefoot |
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What are clinical manifestations of actinomyces israelii infection?
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Poor dentition or trauma leads to oral-cervicofacial disease
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How would one diagnose actinomyces israelii?
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Identification of the organism in Gram-stained sulfur granules and subsequent growth of the organism from cultures is diagnostic. It’s important to have sulfur granules to know the organism is causing the disease and not just part of the normal flora. Actinomyces are not partially acid fast.
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What is alpha hemolysin?
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Alpha hemolysin is a pore-forming toxin that disrupts plasma membranes. E. coli have it.
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What is the difference between diarrhea produced by heat labile (LT) versus heat stable (ST) toxin in ETEC?
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Both lead to the watery stools of traveler’s diarrhea, however LT-induced diarrhea results from stimulation of adenylate cyclase in gut epithelial cells whereas ST-induced diarrhea results from stimulation of guanylate cyclase in the epithelial cells.
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What are the determinants of pathogenicity for E. coli?
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1. alpha-hemolysin: a pore-forming toxin
2. aerobactin: iron siderophore (bind iron and take it away from transferrin) 3. polysaccharide capsule: reduces phagocytosis 4. K1 capsule associated with meningitis & bacteremia 5. Pili; type I pili: binding in the bladder 6. P pili: binding in the upper urinary tract and causing pyelonephritis |
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What is aerobactin?
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Aerobactin is an iron siderophore used by E. coli
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What are characteristics of hemolytic uremic syndrome, and what toxin is thought to cause it?
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HUS is thought to be caused by shiga-like toxin. Patients typically present with bloody diarrhea, crampy abdominal pain, but NO FEVER. HUS has decreased number of platelets, renal failure, and CNS dysfunction.
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Which bacterium is responsible for 15% of food-borne illness in the U.S.?
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Salmonella enterica
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A prolonged fever, persistent bacteremia, constipation or diarrhea, abdominal pain, occasional rash (rose spots) consisting of a few, pale pink macules is consistent with which disease?
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Typhoid fever, caused by Salmonella
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How is Salmonella enterica diagnosed?
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Diagnosis is by routine stool culture, and typhoid fever is diagnosed by growing the organism from the blood or feces
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Where does Yersinia pestis first travel to once it enters the blood stream?
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Once in the bloodstream, Y. pestis travel to the nearest lymph node
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What areas in the U.S. are endemic for bubonic plague?
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Southwestern U.S. is endemic for the bubonic plague (e.g., New Mexico, Arizona, Colorado, California. It occurs usually in hikers or hunters who acquire the illness from wild animals. 90% of cases are in the aforementioned states.
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Fevers, chills, myalgias, arthralgias, headache, and the appearance of a swollen lymph node are indicative of what disease?
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Bubonic plague by Y. pestis.
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Which bacteria look like closed safety pins?
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Y. pestis
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What protein results in cleavage of fibrin, which prevents clot formation and is thought to allow Yersinia bacteria to disseminate throughout the body?
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Plasminogen (Pla.)
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What bacteria exhibit “swarming motility” due to hundreds of flagella per cell?
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Proteus spp. (P. mirabilis and P. vulgaris)
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What is quorum sensing?
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Quorum sensing is a mechanism by which bacteria release autoinducer signals that are detected by their neighbors that let them get a “head count” of bacteria
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Which bacteria produces a “grape like odor” when it grows on laboratory media?
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P. aeruginosa
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Which gram-negative rod uses coiling phagocytosis?
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Legionella
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What are the adhesions for pseudomonas?
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P. aeruginosa uses pili at the end of the bacteria to function as adhesions
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What do LasA and LasB do for pseudomonas aeruginosa?
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They are elastases that degrade elastin.
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What bacteria occupy cooling towers and water distribution systems?
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Legionella
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Which bacteria produces a severe form of diarrhea that could lead to death via rapid dehydration?
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Vibrio cholera
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How does H. pylori survive the acidic environment o the stomach?
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It has a urease that splits ammonia from urea and creates an alkaline microenvironment for H. pylori
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What is VacA, and what does it do for H. pylori?
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VacA is a cytotoxin that causes vacuolation of cultured epithelial cells. People with ulcers are likely to have detectable VacA activity.
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How can you detect/diagnose H. pylori?
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You can perform a urease test, since it’s difficult to culture H. pylori.
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What are the 4 toxins of B. Pertussis and their action?
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1. Pertussis toxin is an A-B toxin; it ADP-ribyslates a host cell G protein which increases cAMP levels.
2. Adenylate cyclase toxin produces cAMP in the presence of host cell calmodulin, which inhibits leukocyte function 3. Dermonecrotic toxin destroys tissue 4. Tracheal cytotoxin: A peptidoglycan fragment that stops or kills ciliated cells and is pro inflammatory |
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What are the 3 stages of whooping cough and their descriptions?
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1. incubation (2 weeks)
2. Catarrhal stage: mild coughing and sneezing (patient very infectious) 3. Paroxysmal stage: explosive coughs. Resolution slow. |
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What disease causes fever, chills, malaise, and drenching sweats and takes 2 to 4 weeks to grow in the laboratory?
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Brucella
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What small, gram-negative coccobacillus is typically contracted from skinning rabbits on a hunting trip?
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Francisella
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Which serogroups of N. meningitides are common in the U.S.?
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B, C, and Y serogroups are common in the U.S.
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What clinical disease presents with severe headache, confusion, lethargy, and vomiting?
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Meningitis (could be caused by N. meningitidis)
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What clinical disease manifests as a sudden onset of fever, chills, nausea, vomiting, rash, myalgia and arthralgias where the rash may be maculopapular, petechial, or ecchymotic? In the fulminant case, patients present with rapid progressive illness with shock, disseminated intravascular coagulation, and multiple organ failure.
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Meningococcemia, caused by N. meningitidis.
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What’s the method of transmission for Rickettsiaceae?
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Transmission is often by insect vectors
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What is OmpA’s function for Rickettsia rickettsii?
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OmpA is an adhesion that allows Rickettsia rickettsi to attach to endothelial cells
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What bacteria produces an illness harbored by sheep and other animals with a Q fever and pulmonary infiltrates but NO rash?
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Coxiella burnetii
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This organism is transmitted by the Lone Star Tick and can be seen inside leukocytes as “mulberry” like clusters called morulae. It causes fever, headaches, myalgias, thrombocytopenia, and leukopenia, and it infects monocytes and macrophages. What is it?
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Ehrlichia chaffeensis
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What organism is similar to Ehrlichia, except it infects neutrophils instead of monocytes and macrophages?
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Anaplasma phagocytophilum
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What bacteria causes cat scratch disease (an enlargement of one or more lymph nodes following a cat scratch or bite)? What is its close relative that is also seen in immunocrompomised individuals and causes bacillary angiomatosis?
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Bartonella henselae causes cat-scratch disease, and both B. quintana and B. henselae cause bacillary angiomatosis.
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What regions are known for Borrelia burgdorferi infections?
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Northeast (Massachussetts to Maryland), Central (Wisconsin and Minnesota), and Pacific Coast (California and Oregon)
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What gram negative bacterium causes lyme disease?
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Borrelia burgdoferi causes lyme disease and has an annular erythematous rash that expands outward and has a central clearing (erythema migrans) that occurs at the site of the bite and is due to the cutaneous spread of the organism outward from the site of inoculation.
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What organism causes syphilis?
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Treponema pallidum
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What bacteria is transmitted by humans drinking water contaminated with animal urine?
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Leptospira interrogans
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Do M. tuberculosis take up gram stain?
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Although they’re gram positive, mycobacteria tuberculosis stain acid fast but do not take up gram stain.
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Define exposure, infection, and disease in the context of tuberculosis?
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Exposure is just being in a place where the bacteria are aerosolized and apparent.
Infection is when the bacteria spreads to local lymph nodes and disseminates to remote sites, but there are usually no apparent symptoms due to an appropriate immune response. Disease is when the bacteria get activated, and the pt has clinical signs and symptoms of TB and feels sick (fever, night sweats, weight-loss). |
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Which two organisms, when they infect humans, prevent fusion of the phagosome with the lysosome and acidification?
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Legionella and M. tuberculosis
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What is miliary tuberculosis?
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Miliary TB is when the bacteria multiplies throughout the body (dissemination of the bacterium is not controlled by host immune system).
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What are the chances of reactivation of TB?
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10%: 5% w/in 2 years; 5% later in life
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What is a granuoloma? How about a caseating granuloma?
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A granuloma is a mass of macrophages, lymphocytes, neutrophils, monocytes, and phagocytosed TB. It becomes caseating when a necrotic core manifests due to the death of macrophages (with concomitant release of toxin) that tried to kill TB and failed.
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What are characteristic symptoms of TB?
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Fever, night sweats, weight loss, upper lobe pulmonary lesions
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What mediates TB’s resistance to antibodies?
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The bacterium grows slowly, which helps confer resistance to antibiotics.
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Besides the lungs, what’s the most common site of spread for TB?
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Lymph nodes, followed by pleura, genitourinary tract, bones & joints, meninges, peritoneum
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What is Pott’s disease?
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Potts disease is when TB manifests in the spine of a pt.
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What causes drug resistance to TB?
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Non-compliance; there are also high numbers of M. tuberculosis in the active disease. Also, its slow division rate also enhances its resistance to antibiotics.
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How do you define multiple-drug resistant TB and extensively drug resistant TB?
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MDR – resistance to rifampin and isoniazid. XDR – additional resistance to quinolones and at least one 2nd line injectable agent (amikacin, capreomycin, kanamycin).
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What vaccine is used to prevent TB?
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The Bacillus-Calmet-Guerin (BCG) vaccine is used to prevent TB, it is derived from an attenuated strain of M. bovis, but it’s used outside of the U.S.
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What are diagnostic tests used to detect TB, and how do they work?
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The PPD (Purified Protein Derivative) of tuberculin, a mix of heat-stable proteins liberated into liquid culture media, is injected intradermally, and one looks for induration (hardening of tissue) after 48-72 hours.
The other diagnostic test is the Interferon-gamma release assay (IGRA) where lymphocytes from a patient’s blood are incubated with M. TB antigens, and one tests if interferon gamma is produced via ELISA. A major advantage of IGRAs over PPD is that they do not cross-react with other Mycobacteria spp. Or BCG vaccination. |
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Does Mycobacterium leprae have any toxins?
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No toxins, it can directly kill Schwann cells, causing nerve demyelination.
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What’s the difference between tuberculous leprosy and lepromatous leprosy?
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In tuberculous leprosy, there’s a strong immune response in contrast to the small immune response with lepromatous leprosy (which is more like miliary tuberculosis).
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The peripheral nerves became enlarged and palpable in what disease?
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Leprosy
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Why may it be difficult to develop a vaccine or other treatments for leprosy?
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M. leprae cannot be cultured on standard media (it’s an obligate intracellular bacterium), although it can be cultured on the footpads of armadillos and mice. It is also very slow in terms of growth and divides every 11-13 days.
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The vaccine for Lyme Disease is based upon which bacterial
protein? A. VacA B. ActA C. OspA D. OmpA E. dot |
C. OspA is a protein of Borrelia burgdorferi against which the Lyme vaccine is made. VacA is a Helicobacter pylori protein, ActA is a Listeria monocytogenes protein, and dot is a genetic locus in Legionella pneumophila.
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Which of the following medias/agars is routinely used to grow Legionella pneumophila?
A. Buffered charcoal-yeast extract agar B. Sheep red blood cell agar C. MacConkey’s agar D. Bordet-Gengou media E. Tellurite selective media |
A. Buffered charcoal yeast extract agar is commonly used to grow Legionella pneumophila. This agar is supplemented with cysteine and antibiotics, which aid in the growth and selection of Legionella.
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Which of the following organisms does NOT use a type III secretion system to cause disease?
A. Yersinia pestis B. Pseudomonas aeruginosa C. Staphylococcus aureus D. Salmonella enterica E. Shigella flexneri |
C. Staphylococcus aureus is a Gram-positive organism. Gram-positive bacteria do not harbor type III secretion systems.
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Which bacterium produces characteristic skin lesions called ecthyma gangrenosum?
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P. aeruginosa
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What bacterium could cause a sore that looks like this?
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Francisella tularensis
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Which bacteria use type III secretion systems?
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1) Shigella
2) EPEC, EHEC 3) P. aeruginosa 4) Salmonella 5) Bordetella 6) Yersinia 7) Chlamydias |
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Which bacteria use type IV secretion systems?
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1) Legionella pneumonia
2) H. pylori |
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Which bacteria live in water or are associated with water?
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1) Legionella (inhabits natural bodies of water as well as cooling towers and water distribution systems, where they parasitize amoebae)
2) Vibrios (V. vulnificus – causes wound infections following cuts exposed to seawater) 3) Leptospira (transmitted to humans following exposure to water contaminated with animal urine) |
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Which bacteria use host actin to propel themselves through the cytoplasm and spread to adjacent cells?
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Shigella, Listeria, R. rickettsii
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Which gram positive or negative organisms are stained poorly by the Gram stain?
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Legionella, Rickettsia rickettsii, Mycoplasma (lack cell walls), (Borrelia burgdoferi?), Treponema pallidum. Mycobacteria better stained with acid fast stains
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What are the super antigens?
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TSST-1
Staphylococal enterotoxins A-E, G-I Streptococcal pyrogenic exotoxins (SPE) A,C |
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Which bacteria stain acid fast?
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Mycobacterium tuberculosis stain acid fast
Nocardia spp. stain acid fast (weakly) |
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Which bacteria have alpha-hemolysins?
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1) Staph aureus
2) E. coli |
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Which bacteria have A-B toxins?
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1) Bacillus anthracis (anthrax toxin is an A-B toxin)
2) Bordetella pertussis (Pertusis toxin is an A-B toxin) 3) Listeria monocytogenes (?) 4) Corynebacterium diptheriae (diphtheria toxin is an A-B toxin) 5) Clostridium tetani (tetanus toxin is an A-B toxin) 6) Clostridium botulinum (Botulinum toxin is an A-B toxin) |
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What is an ADP-ribosylating toxin, and which bacteria have it?
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1) Bordetella pertussis (pertussis toxin)
2) Vibrio cholera (cholera toxin) 3) Pseudomonas aeruginosa (exotoxin A) 4) E. coli (heat labile toxin) 5) Corynebacterium diphtheria |
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Which bacteria have pore-forming toxins?
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1) S. aureus’ Alpha toxin is a pore-forming toxin
2) E. coli have Alpha toxin, a pore-forming toxin 3) Listeria monocytogenes (Listerolysin-O is a pore-forming toxin) |
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What are some facultative intracellular pathogens?
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1) Salmonella
2) Shigella 3) Listeria monocytogenes 4) Legionella 5) Mycobacteria |
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Which bacterial infections could be contracted by ingesting unpasteurized milk?
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1) Listeria monocytogenes
2) EHEC, ETEC 3) Brucella 4) M. bovis |
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Which bacteria are transmitted by ticks?
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1. Yersinia pestis (actually fleas)
2. Rickettsia rickettsii 3. Ehrlichia chaffeensis 4. Anaplasma phagocytophilum 5. Borrelia burdoferi |
