USMLE (Subject) / Microbiology - Flashcards (Lesson)

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  • Which bacteria have IgA proteases? 1. Streptococcus pneumoniae 2. Neisseria gonorrheae 3. Neisseria meningitidis 4. Haemophilus influenzae
  • What does the capsule of Bacillus anthracis consist of? D-glutamate
  • What bacteria do not gram stain well? 1. Treponema 2. Rickettsia 3. Mycobacteria (high-lipid-content wall) 4. Mycoplasma (no cell wall) 5. Legionella pneumophila (primarily intracellular) 6. Chlamydia (intracellular, lacks muramic acid in cell wall)
  • Bacteria with superantigens 1. Staphylococcus aureus 2. Streptococcus pyogenes
  • Bacteria with AB toxins 1. Corynebacterium diphtheriae 2. Vibrio cholerae 3. E. coli 4. Bordetella pertussis
  • Exotoxins released by Staphylococcus aureus Superantigens 1. Toxic shock syndrom toxin (TSST-1) causes toxic shock syndrome (fever, rash, hypotonia) 2. Enterotoxins cause food poisoning (heat-resistant!) 
  • Endotoxins: what do they activate? 1. Macrophages:IL-1 --> FeverTNF --> Fever and hemorrhagic tissue necrosisNitrate-oxide --> Hypotension 2. Alternative complement pathways (C3a, C5a) 3. XI - Hageman factor (coagulation cascade --> disseminated intravascular coagulopathy)
  • What method is used to differentiate Neisseria? Sugar fermentation Meningococci ferment Maltose and Glucose Gonoccoci only ferment Glucose
  • Special culture requirements for: Haemophilus influenzae Chocolate agar with factors X (Hematin) and Y (NAD)
  • Special culture requirements for: Neisseria gonorrhoea Thayer-Martin media
  • Special culture requirements for: Bordatella pertussis Bordet-Gengou (potato) agar
  • Special culture requirements for: Mycobacterium tuberculosis Lowenstein-Jensen agar
  • Special culture requirements for: Lactose-fermenting enteric bacteria Pink colonies on MacConkey agar
  • Special culture requirements for: Fungi Sabourand's agar
  • What microbes can be stained with: periodic acid schiff (PAS) Glycogens and mucopolysaccharids Used to diagnose Morbus Whipple
  • What microbes can be stained with: India ink Cryptococcus neoformans
  • 4 lysogenic genes BCDE 1. Botulinum 2. Cholera 3. Diphtherie 4. Erythrogenic toxin of Streptococcus pyogenes
  • 5 obligate aerobes 1. Bacillus 2. Pseudomonas aeruginosa 3. Mycobacterium tuberculosis 4. Neisseria 5. Legionella
  • 3 obligate anaerobes 1. Clostridium 2. Bacteroides 3. Actinomyces Lack catalase and/or superoxidase dismutase
  • What antibiotics are particularly ineffective against anaerobes? Aminoglycosides, because they require O2 to enter the bacterial cell
  • 3 obligate intracellular bacteria 1. Legionella 2. Chlamydia 3. Rickettsia Can't make their own ATP
  • Encapsulated bacteria 1. Streptococcus pyogenes 2. Haemophilus influenzae (especially B serotype) 3. Neisseria meningitidis 4. Klebsiella pneumoniae
  • What is Protein A? Virulence factor of Staphylococcus aureus. Binds to Fc-IgG, inhibiting complement fixation and phagocytosis
  • What disease states does staphylococcus aureus cause? Inflammatory:1. Skin infections2. Organ abcesses (endocarditis, osteomyelitis)3. Pneumonia Toxin-mediated1. Toxic shock syndrom (TTST-1)2. Scalded skin syndrom (SSSS) from exfoliative toxin3. Rapid-onset food poisoning (preformed enterotoxin)
  • What disease states does streptococcus pyogenes cause? Pyogenic1. Pharyngitis2. Cellulitis3. Impetigo Toxigenic1. Toxic-like shock syndrome2. Scarlet fever Immunogenic1. Rheumatic fever2. Acute glomerulonephritis
  • What is streptococcus pneumoniae the most common cause of? 1. Meningitis 2. Otitis media (in children) 3. Pneumonia 4. Sinusitis MOPS
  • What disease states does staphylococcus epidermidis cause? Infection of prosthetic devices and catheters Contaminates blood cultures
  • What are the mechanisms of a Bacillus anthracis infection? 1. Non-inhalation contact2: Formation of a malignant pustule (painless ulcur)3. Progression to bacteremia4. Death 1. Inhalation of spores2. Development of flulike symptoms that rapidly progress to fever, pulmonary hemorrhage and shock
  • What is Woolsorter's disease? Inhalation of Bacillus anthracis spores from contaminated wool
  • Which bacteria can live in neutrophils? Neisseria
  • Vaccine availability for Neisseria Gonokokken: No Meningokokken: Yes
  • What disease states does Gonococcus cause? 1. Gonorrhea2. Septic arthritis3. Neonatal conjunctivitis4. PID (pelvic inflammatory disease)
  • What disease state does Meningococcus cause? 1. Meningococcemia2. Meningitis3. Waterhouse-Friedrichson syndrome
  • What disease state does Haemophilus influenzae cause? 1. Epiglottidis2. Meningitis3. Otitis media4. Pneumonia Does not cause a flu (that's a virus!)
  • Treatment for Haemophilus influenzae meningitis Ceftriaxone (Cephalosporine) Vaccine: Type B polysaccharide given between 2 and 18 monts of age Close contacts: Rifampin
  • Orange sputum? Which bacteria? 1. Pneumococcus 2. Klebsiella ('red currant jelly' sputum)
  • Salmonella vs. Shigella Animal reservoir: Salmonella: YESShigella: No Virulence: Salmonella >100'000Shigella >10
  • What bacteria causes contamination of: reheated rice? Bacillus cereus
  • What bacteria causes contamination of: meat? 1. Staphylococcus aureus (starts quickly, ends early) 2. E. coli O157:H7 (undercooked meat) 3. Campylobacter 4. Clostridium perfringens (reheated meat dishes) 5. Clostridium botulinum (sausage) 6. Vibrio parahaemolyticus, vulnificus (in seafoods)
  • What bacteria causes contamination of: poultry? 1. Salmonella (and eggs)
  • Difference between mechanisms of cholera and pertussis toxins Cholera: permanently activates Gs (turns "on" "on") Pertussis: permanently disables Gi (turns "off" "off")
  • Treatment for Legionella Has a beta-lactamase (penicillin-resistant) 1. Erythromycin2. Rifampin
  • What disease state does Mycobacterium avium-intracellulare cause? Bacteria are multiple drug resistant and cause disseminated disease in AIDS
  • Symptoms of tuberculosis 1. Fever2. Weight loss3. Hemoptysis (coughing up of blood)4. Night sweats
  • True or false: No gram-positive bacteria have endotoxin. False. Listeria monocytogenes has it.
  • Disease states caused by Chlamydia trachomatis 1. Reactive arthritis (Reiters syndrome)2. Conjunctivitis3. Non-gonoccocal urethritis, cervicitis, pelvic inflammatory disease
  • Disease states caused by Chlamydia pneumoniae 1. Infection of the respiratory tracts2. Atypical pneumoniae 
  • Disease states caused by Chlamydia psittaci 1. Atypical pneumoniae 
  • What is unusual about the Chlamydia wall? It lacks muramic acid.
  • Treatment of Chlamydia Erythromycin or tetracycline

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