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63 Cards in this Set
- Front
- Back
Mechanism of Staphylococcal Toxic Shock Syndrome Toxin 1 (TSST-1)?
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Binds beta chain of TCR nonspecifically --> 20% of all T cells activated --> cytokine storm, systemic inflammation, shock
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What percentage of staph aureus strains produce TSST-1?
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<10%
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Function of Staphylococcal coagulase?
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forms complex w/prothrombin: STAPHYLOTHROMBIN that converts/polymerizes fibrinogen into fibrin clots.
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Which Staphylococcal enzymes function in the degradation of skin?
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lipases
glycerol ester hydrolases |
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Function of Staphylococcal alpha-toxin?
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forms trans-membrane pores that allow egress of vital molecules
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Function of Staphylococcal Panton-Valentine Leukocidin (PVL)?
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effective at lysing PMNs in vitro.
may indicate especially invasive S. aureus strain. |
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Function of Staphylococcal gamma-toxin?
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lyses PMNs in vitro
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What is a furuncle and where does it develop?
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-well defined abscess containing pus enclosed by a fibrin capsule
-forms in the skin, often in a hair follicle or sebaceous/sweat gland -result of tissue destruction by alpha toxin |
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What disease results from spread of furuncles?
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multiple furuncles may coalesce into a carbuncle
disseminated deep tissue infections result in cellulitis |
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Which abx are used for tx of Staph saprophyticus UTI's?
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fluoroquinolones
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What % of UTI's are caused by Staph Saprophyticus?
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10-20%
2nd most common cause of UTI's in young women |
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Dx methods for S. aureus infections?
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Cx overnight growth of catalase positive, coagulase positive GPC in clusters on BA
Blood cultures usually negative for deep abscesses other than endocarditis, osteomyelitis, and arthritis (muscle/bone stuff). |
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Pathogenesis of Staphylococcal food poisoning?
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only toxins (not cells) necessary for sickness.
enterotoxins A through E heat-stable (not necessarily destroyed by cooking!) + serotonin release in GI tract --> vomiting |
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Pathogenesis of STSS?
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caused by TSST-1 or enterotoxins B or C, superantigens
High fever, vomiting, diarrhea, sore throat, muscle pain -> in 48 hrs can progress to shock due to massive T cell activation, cytokine storm |
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Pathogenesis of bullous impetigo?
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superifcial skin infection by S. aureus, usually young children
production of exfoliatin results in fluid-filled, red, itchy blisters filled w/bacteria. blisters break and scab over w/yellow crust. |
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pathogenesis of scalded skin syndrome?
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redness, skin peeling off in sheets due to production of exfoliatin at site of infection (may not be clinically apparent) and beyond
most common in <5 y/o face, armpit, groin affected first; may spread over entire body |
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Which adhesion factors does Staph aureus employ?
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Fibronectin Binding Proteins: FnbpA, FnbpB
Collagen Binding Proteins |
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What is the functions of Staph aureus Protein A?
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Binds Fc portion of antibodies to inhibit their ability to trigger phagocytosis.
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How does Staph aureus evade the immune system?
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-capsule (inhibit phagocytosis)
-exopolysaccharide --> biofilm formation, resists phagocytosis -protein A production |
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What abx are Staphylococci resistant to, and why are they resistant?
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resistant to classical PENICILLINS
PENICILLINASE or BETA-LACTAMASE enzyme allows degradation of beta-lactam abx. |
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What is the mechanism of Staphylococcus' methicillin resistance?
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Pbp2a (Penicillin Binding Protein 2a) has low beta-lactam affinity --> retains transpeptidase activity and can still make cell wall in presence of methicillin
beta-lactams normally bind PBP and block its transpeptidase activity. PBP2a is mutant. |
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Function of Staphylococcal exfoliatin?
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ser protease
disrupts desmosomes (cell junctions) |
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Function of Staphylococcal hyaluronidase?
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hydrolyzes connective tissue
(hyaluronic acid is a component of connective tissue.) |
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Function of Staphylococcal enterotoxin?
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+ serotonin release in GI tract --> vomiting
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Toxins produced by Bordetella pertussis?
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TCT (tracheal cytotoxin)
PT (pertussis toxin) ACT (adenylate cyclase toxin) |
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List all the AB subunit toxins we've discussed.
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Pertussis Toxin
Diphtheria Toxin Botulinum Toxin Cholera Toxin Anthrax Toxin Tetanus Toxin |
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Which of the Rickettsiae and Chalmydiaciae can be cultured on a plate in lab?
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Bartonella spp.
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Which two bacteria cause meningitis following hematogenous spread after a respiratory infection?
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N. meningitidis
H. influenzae |
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What mutations cause Pseudomonas aeruginosa to exhibit increased biofilm formation?
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MUCOID: mucA mutation --> increased Alginate production
WRINKLY: WspF mutation --> increased cdGMP production --> increased pel, psl gene expression |
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What is unique about the structure of Mycoplasma pneumoniae?
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no peptidoglycan cell wall!
cell wall is sterols stolen from host. |
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Function of Mycoplasma pneumoniae's terminal organelle?
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Adhesion to host cell (ciliated resp. epithelium)
P1 protein = adhesin, trafficks to terminal organelle and binds host glycopeptides Also contains actin for coordinating cytoskeletal activities. |
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What causes Q fever?
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Coxiella burnetii
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What causes Rocky Mountain Spotted Fever?
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Rickettsia rickettsii
transmitted by ixodes ticks |
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How do GC and MC evade host immunity?
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-IgA protease
-pili phase variation -vary Opa, Por types -Sialic acid attachment to LOS may block AB binding |
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How does Treponema pallidum evade host immunity?
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Vary surface Ag with TprK gene
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How do Borrelia recurrentis and hermesii evade host immunity?
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~30 vlp/vsp alleles moved from linear plasmid to another plasmid for expression.
serovar switching in population concurrent with fever spikes. |
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What are the two vectors and species that cause relapsing fever?
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TICK (saliva/feces) Borrelia hermesii.
LOUSE (hemolymph--only if crushed!): B. recurrentis |
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How does Corynebacterium diphtheriae regulate diphtheria toxin production?
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DtxR gene: repressor turned OFF in low Fe2+ environments (ex. human) --> Dtx expressed.
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Which toxins are phage-encoded?
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Diphtheria toxin
Botulinum toxin Pseudomonas cytotoxins S. aureus: enterotoxin, exfoliatin |
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Which diseases are transmitted by ticks?
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Lyme Disease (B. burgdorferi)
Rocky Mountain Spotted Fever (R. rickettsii) Relapsing Fever (B. hermesii) Human Monocytic Ehrlichiosis (E. chaffeensis) Human Granulocytic Ehrlichiosis (Anaplasma phagocytophilum) |
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Which diseases are transmitted by lice?
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Relapsing Fever (Borrelia recurrentis)
Trench Fever (Bartonella quintana) Typhus group fevers (Rickettsiae) |
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What is the main killer of whooping cough pts?
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dehydration, malnutrition, anoxic brain damage
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How does Bordetella pertussis regulate TCT, ACT, PT production?
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2-component regulatory system: Bvg genes
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Attack rate of Bordetella pertussis/whooping cough in unimmunized population?
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>95%
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How does Pertussis Toxin work?
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ADP-ribosylates a Gprotein --> ++host cAMP --> alter lymphocyte homing and function.
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Which bug has Elementary Bodies and Reticulate Bodies?
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Chlamydia trachomatis
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What serovars of C. trachomatis cause Trachoma?
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A B Ba C
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What serovars of C. trachomatis cause STD?
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D-K, L1, L2, L3
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What serovars of C. trachomatis cause LGV?
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L1, L2, L3
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Describe stages of LGV.
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Genital lesion
Suppurative inguinal lymphadenopathy, fever, headache, chills Fibrotic changes (formation of xs connective tissue), multiple draining fistulas |
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Describe stages of Lyme Disease.
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ECM-target lesion at tick bite. (must be attached for >24hr)
Neurologic/cardiac abnormalities, headache, neck and muscle pain, conjunctivitis (weeks after ECM) Arthritis (months-years after ECM) |
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Describe stages of Syphilis.
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genital chancre, painless indurated lesion; localized lymphadenopathy
1-3mos later: general lymphadenopathy, rash (foci are where treponemes are proliferating) 2-50yr later: latency OR benign gummatous lesions OR cardiovascular/neurological complications |
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Which diseases are zoonoses?
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Leptospirosis
Psittacine Fever/Parrot Fever Rickettsiae and Chlamydiaciae diseases (Rocky Mtn, Cat scratch, Trench, Q Fevers; HGE, HME) |
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What determines whether C. trachomatis causes Trachoma vs. STD/LGV?
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-serotype
-route of infection: eyes/fomites (trachoma) vs. sexual contact (LGV/STD) |
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Function of metronidazole?
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disrupt DNA helix --> no replication
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Function of linezolid?
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bind 50S ribosomal subunit --> no translation initiation
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Function of tetracyclines?
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bind 30S ribosomal subunit --> charged tRNA cannot enter
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Function of quinolones, fluoroquinolones?
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attacks gm- DNA gyrase, gm+ topoisomerase IV --> no DNA replication/repair
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Function of vancomycin?
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binds NAG/NAM peptide tails --> PBP cannot form crossbridges.
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Function of Macrolides?
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binds 50S ribosomal subunit --> no protein synthesis
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Function of aminoglycoside abx?
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binds 30S ribosomal subunit --> misread or truncate proteins
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Which abx disrupt cell wall synthesis?
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penicillins
cephalosporins imipinem vancomycin (glycopeptides) |
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Function of rifampin?
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binds beta subunit of RNA pol --> no transcription.
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