91. Microbiology p176-186
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- Bacterial Strucutre & Cell Walls
- p.176
- Where is beta-lactamase in bacteria? What does it do?
- Beta-lactamases are found in the periplasm of gram negative bacteria. The enzyme hydrolyzes beta-lactam antibiotics, conferring resistance.
- Which gram-positive organism lacks a polysaccharide capsule?
- Bacillus anthracis - has D-glutamate instead of polysaccharide
- What are spores made of and what do they do?
- Keratin-like coat, dipicolinic acid. Provide resistanceto dehydration, heat and chemicals
- What helps organisms adhere to indwelling catheters?
- The glycocalyx (composed of polysaccharide)
- What is the major surface antigen of gram-positive cell walls and what does it do?
- Teichoic acid - unique to gram-positive bacteria. Induces TNF and IL-1
- What is specific to gram-negative bacterial cell walls?
- Endotoxin/LPS (lipopolysaccharide)
- Bacterial Growth Curve
- p. 177
- Describe the four phases of bacterial growth.
- 1) Lag phase of metabolic activity without division. 2) Log phase of rapid cell division. 3) Stationary phase in which nutrient depletion slows growth. 4) Death due to prolonged nutrient depletion and buildup of waste products.
- Main Exotoxin and Endotoxin Features
- p. 177
- What are exotoxins and endotoxin chemically?
- Exotoxins are polypeptides, while endotoxins are lipopolysaccharides.
- Where do bacteria keep their exotoxin or endotoxin genes?
- Exotoxin genes on plasmids or bacteriophages; endotoxin genes on bacterial chromosomes.
- Which is more fatal – exotoxin or endotoxin?
- Exotoxin is highly fatal (~1 microgram), while you need 100Â’s of micrograms for endotoxin to prove lethal.
- Which has greater heat stability – endotoxin or exotoxin?
- Endotoxin – stable at 100°C for 1 hour, while endotoxin is rapidly destroyed at 60°C (EXCEPT Staph enterotoxin)
- True or False: We can vaccinate against exotoxins and endotoxins.
- False: We do have toxoids vaccines against exotoxins for diseases like tetanus, botulism and diphtheria, but there are no vaccines against endotoxins.
- Bugs with Exotoxins
- p. 178
- Which bugs have Exotoxin that acts by ADP ribosylation?
- Corynebacterium diphtheriae (which then inactivates EF-2). Also Escherichia coli, Vibrio cholerae, and Bordetalla pertussis (all these then stimulate adenylate cyclase).
- Which bug has exotoxin that blocks the release of acetylcholine? What symptoms does that cause?
- Clostridium botulinum. Anticholinergic symptoms, CNS paralysis, floppy baby, and a wrinkle-free forehead if injected!!
- Which bug has exotoxin that blocks glycine release? What does that cause?
- Clostridium tetani. Causes “lockjaw”.
- How does Staph aureus cause toxic shock syndrome?
- The toxin is a superantigen that binds to MHC II protein and T-cell receptor à induces IL-1 and IL-2 à TSS
- Endotoxin (especially lipid A)
- p. 178
- How could bacterial infection cause disseminated intravascular coagulation?
- Endotoxin can activate Hageman factor --> initiates coagulation cascade --> DIC
- How could bacterial infection cause hypotension?
- Endotoxin activates macrophages to release nitric oxide (--> vasodilationà hypotension); can also activate alternate complement pathway C3a, --> hypotension (N.B. also edema).
- How does bacterial infection cause fever?
- Endotoxin activates macrophages to release IL-1 and TNF --> fever.
- Gram Stain Limitations
- p. 178
- --- are too thin to be visualized. Use darkfield microscopy and fluorescent antibody staining instead.
- Treponema
- --- lack a cell wall
- Mycoplasma
- --- stain with silver
- Legionella pneumophila
- Fermentation patterns of Neisseria
- p. 179
- What are the two Neisseria species?
- N. meningitidis, N. gonorrhoeae
- How are the Neisseria species differentiated?
- MeninGococci ferment Maltose & Glucose; Gonococci ferment only Glucose
- Pigment-producing Bacteria
- p. 179
- --- produces a yellow pigment
- Staphylococcus aureus (Latin aureus = gold)
- --- produces a blue-green pigment
- Pseudomonas aeruginosa
- --- produces a red pigment
- Serratia marcescens (think red marachino cherry)
- IgA Proteases
- p. 179
- IgA proteases allow organisms toÂ…
- Â… colonize mucosal surfaces
- Name 4 organisms with IgA proteases
- Strep pneumoniae, N. meningitidis, N. gonorhoeae, H. influenzae
- Gram-positive Lab Algorithm
- p. 180
- What are the lab steps for ID'ing Staphylococcus aureus?
- 1st gram stain --> get purple/blue cocci (= positive); 2nd catalase test --> positive (staphylococcus clusters); 3rd coagulase test --> positive (differentiates S. aureus from the coagulase-negative S. epidermidis and S. saprophyticus)
- What are the 4 types of gram-postive rods?
- Corynebacterium, Listeria, Bacillus, Clostridium
- When do you test for bacitracin sensitivity or resistance?
- For beta-hemolytic strep. Bacitracin-sensitive --> Group A beta-hemolytic Strep pyogenes. Bacitracin-resistant --> Group B (Bad!) beta-hemolytic Strep agalactiae
- Name 4 laboratory features of Streptococcus pneumoniae
- alpha hemolytic (green – partial hemolysis), positive Quellung reaction, optochin-sensitive, and bile-soluble
- Once you see gram-negative rods under the microscope, what is your next diagnostic test?
- test lactose fermentation
- What are the 3 fast lactose fermenters:
- Klebsiella, E. coli, and Enterobacter
- How do you distinguish among lactose non-fermenters?
- Perform an oxidase test
- Which are oxidase-positive?
- Pseudomonas
- Which are oxidase-negative?
- Shigella, Salmonella, or Proteus
- What are the gram-negative cocci?
- Neisseria
- What are the gram-negative coccoid rods?
- H. influenzae, Pasteurella, Brucella, Bordetella pertussis
- Special Culture Requirements
- p. 180
- Use chocolate agar and factors V & X for ---
- Hemophilus influenzae
- Factor V has --- and Factor X has ---
- NAD, hematin
- Thayer-Martin (VCN) media to culture ---
- Neisseria gonorrhoeae
- Bordet-Gengou (potato) agar to culture ---
- Bordetella pertussis
- Tellurite plate, Loffler's medium, blood agar for ---
- Corynebacterium diphtheriae
- Lowenstein-Jensen agar for growing ---
- Mycobacterium tuberculosis
- Pink colonies on MacConkey's agar are ---
- Lactose-fermenting enterics (Klebsiella, Eschericihia, or Enterobacter
- Charcoal yeast extract agar buffered with increased iron and cysteine to grow ---
- Legionella pneumophila
- Sabouraud's agar to culture ---
- Fungi
- Stains
- p. 181
- Stain used to diagnose Whipple's disease
- PAS (Periodic Acid Schiff)
- PAS stains ---
- glycogen, mucopolysaccharides
- Ziehl-Neelsen stains ---
- Acid-fast bacteria
- India ink stains ---
- Cryptococcus neoformans
- Congo red stains -- and exhibits ---
- Amyloid, apple-green birefringence in polarized light
- Giemsa's stains what 4 organisms?
- Borrelia, Plasmodium, trypanosomes, Chlamydia
- Conjugation, Transduction, Transformation
- p. 181
- Which process can involve eukaryotic DNA?
- Transformation
- DNA transferred from 1 bacterium to another is
- Conjugation
- DNA transferred by a virus from 1 cell to another
- Transduction
- Generalized transduction can transfer --
- Any gene
- Specialized transduction transfers ---
- only certain genes (that's why it's special!)
- Obligate Aerobes
- p. 181
- "Nagging Pests Must Breathe" helps you remember what?
- obligate aerobes: Nocardia, Pseudomonas aeruginosa, Mycobacterium tuberculosis, Bacillus
- Aerobic bacteria commonly found in burn wounds, nosocomial pneumonia, and pneumonias in cystic fibrosis patients?
- Pseudomonas aeruginosa (an obligate aerobe)
- What bug likes the lungsÂ’ apices and why?
- Mycobacterium tuberculosis – because the apices have the highest partial pressure of oxygen
- Obligate Anaerobes
- p. 181
- If you hear crepitus, indicating gas in tissue, what type of infection do you suspect?
- Anaerobic bacterial infection, such as Clostridium, Bacteroides, or Actinomyces (CBA)
- Which bugs are anaerobic and why?
- Clostridium, Bacteroides, and Actinomyces. Air causes them oxidative damage, because they lack catalase and/or superoxide dismutase.
- Why are aminoglycoside antibiotics ineffective against anerobic bacteria?
- "AminO2glycosides" require O2 to enter into bacterial cells; anaerobic bacteria aren't where the oxygen is
- Intracellular Bugs
- p. 181
- Name the 2 obligate intracellular organisms
- Rickettsia, Chlamydia - "They stay inside (cells) when it's Really Cold"
- Why do they need the host's cell?
- They can't make ATP
- Name 7 facultative intracellular organisms
- Mycobacterium, Brucella, Francisella, Listeria, Yersinia, Legionella, Salmonella
- Encapsulated Bacteria
- p.182
- List 4 examples of encapsulated bacteria
- Streptococcus Pneumoniae, Haemophilus influenzae, Neisseria meningitidis, Klebsiella pneumoniae
- What is the main virulence factor of encapsulated bacteria and why?
- Polysacharide capsule is antiphagocytic
- What is a necessary component of humoral immune response to encaps. Bacteria?
- IgG2
- What vaccines are available for encapsulated bacteria?
- Pneumovax, H. influenzae, meningococcal
- What serves as vaccine antigen?
- Capsule
- What laboratory test can be used to detect the presence of encapsulated bacteria?
- Quellung reaction - capsule swells when specific anticapsular antisera are added - "Quellung = capsular swellung"
- What complications/clinical signs is pneumococcus associated with?
- "Rusty sputum", sepsis in sickle cell anemia, and splenectomy
- Spores: Bacterial
- p. 182
- What kind of bacteria form spores and when?
- Certain gram-positive rods when nutrients are limited
- Name 3 spore-formers
- Bacillus anthracis, C. perfringens, C. tetani = gram positive soil bugs
- T or F: Spores are highly resistant to destruction by heat and chemicals
- TRUE
- Spores have ___ acid in their core
- dipicolinic
- T or F: Spores are metabolically active
- False. Spores have no metabolic activity
- What disinfecting procedure kills spores?
- Autoclaving (ex/ surgical equipment)
- Alpha-hemolytic Bacteria
- p. 182
- What organisms are alpha-hemolytic?
- Pneumococci, viridans strep
- Pneumococci are catalase ___ and optochin ___
- Pneumococci are catalase sensitive and optochin sensitive
- Viridans strep are catalase ___ and optochin ___
- Viridans strep are catalase sensitive and optochin resistant
- Beta-hemolytic Bacteria
- p. 182
- What organisms are beta-hemolytic?
- Staph aureus, strep pyogenes, strep agalactiae, lysteria monocytogenes
- Staph aureus is catalase ___ and coagulase ___
- Positive, positive
- Strep pyogenes is catalase ___ and bacitracin __
- negative, sensitive
- Strep agalactiae is catalase __ and bacitracin__
- negative, resistant
- Where is Lysteria monocytogenes found, and what is its characteristic pathology and laboratory appearance?
- Unpausterized milk, miningitis in newborns, tumbling motility
- Catalase/Coagulase
- p. 182
- What are catalase and coagulase tests used for?
- Catalase is used to distinguish staph (+) from strep (-), coagulase is used to distinguish S. aureus (+) from S. epidermis (-) and S. saprophyticus(-)
- How is catalase a virulence factor?
- It degrades H2O2, an antimicrobial product of PMNs that is a substrate for myeloperoxidase
- Staph aureus
- p. 182
- What is the function of protein A?
- Virulence factor - binds to Fc-IgG and inhibits complement fixation and phagocytosis
- TSST is a ___ (type of virulence factor) that binds to ___ (2 types of receptor) and causes ___ of ___ (type of cells) leading to ___ (disease)
- TSST is a superantigen that binds to MHC II and T-cell receptor and causes polyclonal activation of T-cells leading to toxic shock syndrome
- 3 toxins of S. aureus and a syndrome caused by each
- TSST- 1 - toxic shock syndrome, exfoliative toxin - scalded skin syndrome, enterotoxins - rapid-onset food poisoning
- T/F - S. aureus causes acute bacterial endocarditis
- TRUE
- T/F - S. aureus causes skin disease and organ abscesses, but not pneumonia
- False - causes all 3
- T/F - S. aureus food poisoning is due to bacterial infiltration of the intestinal wall
- False - it is due to ingestion of preformed enterotoxin
- Strep Pyogenes
- p. 182
- T/F: strep pyogenes is catalase negative and bacitracin sensitive
- TRUE
- 3 pyogenic manifestations of strep pyogenes
- pharyngitis, cellulitis, impetigo
- Which is not a toxigenic manifestation of strep pyogenes: scarlet fever, rheumatic fever, TSS, acute glomerulonephritis
- Rheumatic fever and acute glomerulonephritis are immune-mediated
- List 5 signs and symptoms characteristic of rheumatic fever
- PECCS: polyarthritis, erythema marginatum, chorea, carditis, subcutaneous nodules
- Enterococci
- p. 183
- T/F: Enterococci are penicillin G sensitive and show variable hemolysis
- F - they are resistant, but do have variable hemolysis
- Lancefield group D includes ___ and ___, which can be differentiated through ___ (lab test)
- Enterococci and non-enterococcal Group D strep. Enterococci can grow on 6.5% NaCl, and non-enterococci cannot.
- Lancefield grouping is based on ___ on the bacterial cell wall
- C carbohydrate
- Viridans Strep
- p. 183
- Viridans Strep are ___ hemolytic
- alpha
- Strep mutans causes ___
- dental caries
- S. sanguis causes ___
- bacterial endocarditis
- How do you differentiate viridans strep from S. pneumoniae in the laboratory?
- Both are alpha-hemolytic, but viridans strep is resistant to optochin (live in the mouth, not afraid of-the-chin)
- Clostridia
- p. 183
- T/F: Clostridia are gram-positive, spore-forming, microaerophilic bacteria
- False - they are obligate anaerobes
- Name 4 types of Clostridia and disease caused by each
- Tetanus - tetanic paralysis, Botulinum - flaccid paralysis, Perfringens - gangrene, Difficile - diarrhea
- How does Clostridia cause tetanic paralysis?
- Exotoxin blocks glycine (inhibitory neurotransmitter) release from Renshaw cells in spinal chord leading to tetanic paralysis
- How does C. botulinum cause flaccid paralysis?
- Preformed, heat - labile toxin inhibits ACh release
- T/F: C. perfringens produces alpha-toxin, a globulin that causes myonecrosis, gas gangrene, or hemolysis
- False - alpha-toxin is a lecithinase
- What causes pseudomembranous colitis? How is it treated?
- Cytotoxin, an alpha toxin produced by C. diff, usu after antibiotic use (clindamycin ar ampicillin). Treat with metronidazole.
- Diphtheria
- p. 183
- Exotoxin is encoded by ___ and ihibits ___ by ADP-ribosylation of ___
- beta-prophaage, protein synthesis, EF-2
- T/F: Symptoms of diphtheria include pseudomembranous pharyngitis, lymphadenopathy, and hematuria
- Does not cause hematuria
- Lab tests for Diphtheria
- Gram-positive, club-shaped rods with metachromatic granules; grow on tellurite agar
- ABCDEFG of diphtheria
- ADP ribosylation, Beta-prophage, Corynebacterium, Diphtheriae, EF-2, Granules
- Anthrax
- p. 184
- Anthrax is caused by ___ (bacteria)
- Bacillus anthracis
- T/F: Bacillus anthracis is spore-forning and gram negative rod
- FALSE - it is a gram-positive rod
- What is the progression of anthrax?
- Contact leads to malignant pustule (painless ulcer) which can progress to bacteremia and death
- What is woolsorter's disease?
- Life-threatening pneumonia caused by inhalation of spores
- Characteristic lesion of anthrax
- Black skin lesions - vesicular papules covered by black eschar
- Actinomycis Vs. Nocardia
- p. 184
- Actinomycis, Nocardia are gram___ rods that form long-branching filaments resembling fungi
- positive
- What air requirement do actinomysis and nocardia have?
- Actinomyces is an anaerobe and nocardia is an aerobe
- A vs. N (pick one): pulmonary infection in immunocompromized
- nocardia
- A vs. N (pick one): oral/facial abscess with sulfur granules that may drain through sinus tracts in skin
- actinomyces
- A vs. N (pick one): Normal oral flora
- actinomyces
- A vs. N (pick one): Weakly acid fast
- nocardia
- What treatment do you use for actinomycis? For nocardia?
- SNAP - sulpha for nocardia; actinomyces use penicillin
- Penicillin and gram-neg bacteria
- p. 184
- Gram negative bugs are ___ to benzyl penicillin G and ____ to penicillin derivatives such as ampicillin
- resistant, may be susceptible
- T/F: Vancomycin can enter gram-negative bacteria
- False - gram-negative outer membrane layer inhibits entry of penicillin G and vancomycin
- Bugs causing food poisoning
- p. 184
- Reheated rice
- Bacillus cereus
- Contaminated seafood
- Vibrio parahemolyticus and vulnificus
- Meats, mayonaise, custard
- S. aureus
- Reheater meat dishes
- C. perfringens
- Improperly canned food
- C. botulinum
- Undercooked meat
- E. coli 0157:H7
- Poultry, meat, eggs
- Salmonella
- Diarrhea, bugs causing watery, bugs causing bloody
- p. 184
- Ferments lactose and causes non-bloody diarrhea
- enterotoxigenic E. coli
- Comma-shaped organism
- Vibrio cholerae
- Does not ferment lactose, motile, bloody diarrhea
- Salmonella
- Does not ferment lactose, nonmotile, very low ID50, bloody diarrhea
- Shigella
- Comma or S-shaped, growth at 42 degrees, bloody diarrhea
- Campylobaxter jejuni
- Transmitted by seafood
- Vibrio parahemolyticus
- Transmitted through pet feces (puppies), bloody diarrhea
- Yersenia enterocolitica
- Rice-water stools
- Vibrio cholerae
- 4 non-bacterial causes of non-bloody diarrhea
- Virus - rotavirus, norwalk virus; protozoan - Cryptosporidium and Giardia
- Ferments lactose and causes bloody diarrhea
- E. coli 0157:H7
- Protozoan cause of bloody diarrhea
- Entamoeba histolytica
- Enterobacteriaceae
- p. 185
- Lab tests for enterobacteriaceae
- Ferment glucose, oxidase negative
- T/F: Enterobacteriaceae includes E.coli, Salmonella, Klebsiella, Enterobacter, Serratia, Proteus, and Pseudomonas
- False - does not include Pseudomona
- Describe O, K, and H antigens
- O - somatic, polysacharide of endotoxin; K - capsular, related to virulence; H - flagellar, found in motile species
- Haemophilus Influenzae
- p. 185
- Name 4 diseases caused by H. influenzae
- epiglottitis, meningitis, otitis media, pneumonia
- T/F - H. influenzae is a large gram-negative rod
- False - it is a small (coccobacillary) gram-negative rod
- H. influenzae is transmitted by ____ and invasive disease is caused by capsular type ___. It produces ___ protease.
- aerosol, B, IgA
- Culture on ___ agar requires ___ and ___
- Chocolate agar, Factor V (NAD), X (hematin)
- T/F: H. influenzae causes the flu.
- False - influenza virus causes flue
- Use ___ to treat H. influenzae meningitis and ___ for prophylaxis of close contacts.
- Ceftriaxone, rifampin
- T/F: H. influenzae vaccine contains type D capsular polysacharide conjugated to enterotoxin
- False: vaccine contains type B capsular polysacharide conjugated to diphtheria toxoid or other protein
- When is the H. influenzae vaccine given?
- Btw 2 and 18 months of age
- Legionella Pneumophilia
- p. 185
- Legionella Pneumophilia is a gram___ rod
- negative
- Legionella pneumophila will grow on ___ yeast extract with ___ and ___, and should be treated with ___
- Charcoal, iron, cysteine, erythromycin
- T/F: Legionella pneumophilia is transmitted through environmental water source habitat.
- TRUE
- T/F: Legionella is transmitted person to person.
-
False - no person to person transmission
(ubiquitous in man and natural water environments) - Pseudomonas Aerugenosa
- p. 185
- T/F: Pseudomonas Aerugenosa is anaerobic gram-negative rod found in water sources
- False - it is AERobic (AERuginosa)
- Name 5 infections commonly caused by Pseudomonas
- Pneumonia (esp. in CF), sepsis, external otitis, UTI, hot tub folliculitis
- T/F: Pseudomonas Aerugenosa ferments lactose and is oxidase-negative
- False - P. Aurugenosa does not ferment lactose and is oxidase negative
- Blue-green pigment produced by P. Aerugenosa
- pyocyanin
- What 2 toxins does P. Aerugenosa produce?
- Endotoxin (causes fever and shock), exotoxin A (inactivated EF-2)
- What is the treatment for P. aeruginosa
- Aminoglycoside plus extended-spectrum penicillin (piperacillin, ticarcillin)
- What kind of injury makes a person especially susceptible to P. aeruginosa infection?
- Burns
- Helicobacter Pylori
- p. 185
- What conditions does H. pylori cause and is a risk factor for?
- Causes gastriti and 90% of duodenal ulcers, risk of peptic ulcer, gastric carcinoma
- T/F: H. pylori is a gram-negative rod that creates an alkaline environment
- TRUE
- What is a test for H. pylori?
- Urease breath test
- What is the treatment for H. pylori?
- Triple therapy - bismuth, metronidazole, and tetracycline or amoxicyclin OR more expensive metronidazole, omeprazole, and clarithromycin
- What 2 bacteria are urease positive?
- H. pylori and Proteus
- Lactose - fermenting enteric bacteria
- p. 185
- What culture technique differentiates lactose fermenting from non-fermenting bacteria?
- Lactose fermenters grow pink colonies on MacConkey's agar (Lactose is KEE)
- Klebsiella
- Ferments lactose
- Salmonella
- Does not ferment
- E.coli
- Ferments lactose
- Enterobacter
- Ferments lactose
- Citrobacter
- Ferments lactose
- Salmonella Vs. Shigella
- p. 186
- Non-lactose fermenter
- both
- Motile
- SalMOnella
- Invades futher, disseminates hematogenously
- Samonella
- More virulent
- Shigella (10e1 innocumlum compared to 10e5 innoculum for Salmonella)
- Symptoms prolonged with antibiotic treatment
- Samonella
- Has an animal resevoir
- Samonella
- Invade intestinal mucosa causing bloody diarrhea
- both
- What immune cell type predominantly responds to Salmonella?
- Monocytes
- How is Shigella transmitted?
- 4 f's: food, fingers, feces, and flies
- Cholera and Pertussi toxins
- p. 186
- How does Vibrio Cholerae toxin work?
- Permanently activates Gs causing rice-water diarrhea
- How does Pertussis toxin work?
- Permanently disables Gi, causing whooping cough, also promotes lymphocytosis by inhibiting chemokine receptors
- What do Pertussis toxin and Choleratoxin have in common?
- Act via ADP ribosylation that permanently activates adenyl cyclase, resulting in increased cAMP
- Zoonotic Bacteria
- p. 186
- Name 5 common zoonotic bacteria
- "Bugs from your pet": Borrelia burgdorferi, Brucella, Francisella tularensis, Yersinia pestis, Pasteirella multocida
- Borrelia burgdorferi
- Lyme disease; tick bite; Ixodes ticks that live on deer and mice
- Brucella
- Brucellosis/undulant fever; dairy products, contact with animals -- "Undulate and Unpasteurized products give you Undulant fever"
- Francisella tularensis
- Tularemia; tick bite; rabbits, deer
- Yersenia pestis
- Plague, flea bite; rodents, esp. prarie dogs
- Pasteurella multocida
- Cellulitis; animal bite; cats, dogs
- Gardnerella vaginalis
- p. 186
- What symptoms are associated with G. vaginalis infection?
- Vaginosis - greenish vaginal discharge, fishy smell, not painful
- What is Mobiluncus?
- An anaerobe commonly involved in G. vaginalis infections
- G. vaginallis should be treated with ___
- Metronidazole
- What are the laboratory characteristics of G. vaginalis?
- Pleiomorphic, gram-variable rod; clue cells - vaginal epithelial cells covered with bacteria are visible under a microscope