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M&I > Bacteria > Flashcards

Bacteria Flashcards

1
Q

Pseudomonas aeruginosa

A

Microbiology

  • Gram-
  • Smells like grapes
  • Motile - single flagellum
  • Quorum sensing
  • Biofilm

Epidemiology

  • Tropism for moist environment
    • Pools, contact cases, respiratory equipment
    • Axilla, perineum, ear
  • Opportunistic infection
    • Ventilator pneumonia
    • Death following bone-marrow transplant
    • Burn units

Pathogenesis

  • Attachment and Colonization
    • Weak adhesion to epithelia due to pili
  • Local Invasion
    • Toxins: elastase, alkaline phosphatase, phospholipase C, cytotoxin
    • Effects: tissue destruction, Ig destruction, microvascular injury
  • Systemic Dissemination
    • LPS
    • Exotoxin A
    • Exoenzyme S

Clinical Manifestations

  • Ecthyma gangrenosum - ulcer surrounded by erythema
  • Bacteremia
  • Pneumonia
  • Ear and eye infections
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1
Q

Borrelia burgdorferi

A

Microbiology

  • Atypical
  • OSP
    • Outer surface proteins
    • Encoded by plasmids

Epidemiology

  • Ticks

Pathogenesis

  • Lipoproteins bind to CD4 and TLRs

Clinical Manifestations

  • Erythema migrans - expanding, targetoid rash at site of tick bite
  • Flu-like symptoms - headache, fever
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2
Q

Enterotoxigenic Escherchia coli (ETEC)

A

Microbiology

  • Gram-

Epidemiology

  • Most common cause of traveler’s diarrhea
  • Spread via contaminated water

Pathogenesis

  • Toxins
    • LT - almost identical to cholera toxin
    • ST - stimulates cGMP, producing similar effects as cAMP
  • No damage to mucosal surface

Clinical Presentation

  • Diarrhea
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2
Q

Acinetobacter baumanni

A

Microbiology

  • Gram-
  • Expresses efflux pumps to extrude antibiotics
  • Beta-lactamases

Epidemiology

  • Prevalent during natural disasters
  • Becoming common in hospitals

Pathogenesis

  • Adheres to bronchial epithelial cells

Clinical Manifestations

  • Pneumonia
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4
Q

Vibrio cholerae

A

Microbiology

  • Single polar flagellum - rapid, linear motion
  • Can switch between dormant and active states (for years)
  • O antigen - LPS
  • H antigen - flagellar antigen

Epidemiology

  • Reservoir is water
  • Diarrheal fluid perpetuates spread of disease by further contaminating water supplies

Pathogenesis

  • Toxin: 6 subunits - 5B + 1A
    • B binds to ganglioside GM1
    • A activates adenylate cyclase
  • Increased cAMP
    • Blocks absorption of sodium and chloride
    • Promotes secretion of chloride and water

Clinical Manifestation

  • Severe diarrhea
  • No cramps or strain

Treatment

  • Doxycycline
  • Tetracycline
  • Trimethoprim-sulfamethoxazole
  • Ciprofloxacin
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5
Q

Salmonella enteritidis

A

Microbiology

  • Gram-

Epidemiology

  • Transmitted via poultry products

Pathogenesis

  • Ingested bacteria is internalized by M cells within the intestines

Clinical Manifestations

  • Diarrhea
  • Nausea
  • Vomiting
  • Excretion of bacteria in stools for weeks

Treatment

  • Antibiotic treatment paradoxically may increase duration of carriage
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6
Q

Yersinia pestis

A
  • Microbiology
    • Gram-
    • Bipolar staining (stains on either side but not in middle)
    • Antiphagocytic capsule containing the I antigen
  • Epidemiology
    • Normal distribution
  • Virulence Factors
    • LPS endotoxin
    • Coagulase
    • Fibrinolysin
    • LPS endotoxin
    • V and W antigens
  • Pathogenesis
    • Flea bites an infected rat
    • Flea bites a human
    • Bacteria travels to regional lymph nodes
    • Phagocytosed bacteria begins to express I antigen on capsule to prevent further phagocytosis
    • Hemorrhagic necrosis of lymph nodes
  • Clinical Manifestations
    • Fever
    • Chills
    • Bubo - extremely tender lymph node with extensive swelling and possible necrosis
    • Pneumonic plague - dreaded complication of bubonic plague which can be spread human-to-human
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7
Q

Klebsiella pneumoniae

A

Microbiology

  • Gram-
  • K1 and K2 antigens - prevent phagocytosis
  • Mucous colonies

Epidemiology

  • Immunocompromised individuals
  • Hospitalized patients

Clinical Manifestations

  • Liver abscess
  • Meningitis
  • Pneumonia
  • Bacteremia
  • UTI
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8
Q

Pasteurella multocida

A

Microbiology

  • Gram-
  • Antiphagocytic polysaccharide capsule that aids in intracellular survival

Epidemiology

  • Animal bites (normal flora in animals)
  • Animal licking of wounds

Pathogenesis

  • Bacterial fimbriae cause adherence to mucosal membrane of animals
  • Bacteria transferred during an animal bite
  • Humoral immunity is protective

Clinical Manifestations

  • Cellulitis
  • Purulent discharge
  • Regional lymphadenopathy
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9
Q

Haemophilus influenzae, type B

A

Microbiology

  • Gram-
  • Requirements
    • X Factor (hemin)
    • V Factor (NAD or NADP)
  • Polyribosyl ribitol phosphate (PRP) capsule - resistance to phagocytosis by PMNs

Epidemiology

  • Spread via airborne droplets
  • Encapsulated serotypes can penetrate nasopharyngeal epithelium and enter capillaries
  • Non-encapsulated serotypes cause local disease

Pathogenesis

Clinical Manifestations

  • Otitis media
  • Pneumonia
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10
Q

Salmonella typhi

A

Microbiology

  • Gram-

Epidemiology

  • No animal reservoir
  • Acquired through water contaminated with human excreta

Pathogenesis

  • Ingested bacteria is internalized by M cells within the intestines
  • Bacteria travels through lymphatics

Clinical Manifestations

  • Prolonged infection (weeks)
  • Rose spots
  • Intestinal perforations
  • Abdominal hemorrhaging

Treatment

  • Six weeks of trimethoprim-sulfamethoxazole and amoxicillin
  • Must have biliary and kidney stones resolved
  • Pulse-temperature deficit
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10
Q

Enterohemorrhagic Escherichia coli (EHEC)

A

Microbiology

  • Gram-
  • Shiga-like toxin
    • A subunit binds to 60S ribosomes in large bowel and kills the mucosal cell

Epidemiology

  • Food
    • Bovine origin
    • Vegetables contaminated during irrigation
  • Water
    • Drinking water
    • Swimming
  • Direct Human Contact

Pathogenesis

  • Fimbrial adhesin - attaches to large intestine mucosa
  • Shiga-like toxin causes endothelial cell damage
  • Bacteria enters bloodstream
    • Endothelial cell damage
    • Hemolytic uremia syndrome

Clinical Presentation

  • Watery diarrhea that becomes bloody
  • Hemolytic uremia syndrome
    • Hemolysis
    • Kidney failure (possible lifetime dialysis)
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11
Q

Treponeme pallidum

A

Microbiology

  • Atypical
  • Undulating movement

Epidemiology

  • Cause of syphilis
  • Southeastern gay males

Pathogenesis

  • Transmitted through physical contact
  • Penetrates membranes and spreads throughout body
  • Incubating Syphilis
    • 3 weeks
  • Primary Syphilis
    • Single chancre
  • Secondary Syphilis
    • 2-8 weeks after chancre
    • Rash, alopecia, lymphadenopathy
  • Latent Syphilis
    • No clinical manifestations
  • Late (Tertiary) Syphilis
    • Neurosyphilis
    • Cardiovascular syphilis
      • Result of endarteritis
      • Aneurism
    • Gummatous Syphilis
      • Granulomas
      • Liver, bones, skin

Clinical Manifestations

  • chancre
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13
Q

Bordetella pertussis

A

Microbiology

  • Gram-

Epidemiology

  • Humans and higher primates are the only reservoirs

Pathogenesis

  • Bacteria is inhaled and adheres to ciliated epithelium in nasopharynx
  • Advancement to alveoli causes pertussis
  • Adhesion factors
    • Filamentous hemagglutinin - binds galactose residues on ciliated cells
    • Pertussis toxin - serves as adhesin to bind bacteria to host cells
    • Pertactin
  • Toxicity
    • Pertussis toxin inhibits Gi
    • Secretion of adenylate cyclase
    • Tracheal cytotoxin stops ciliated cells from beating

Clinical Manifestations

  • Stages
    • Catarrhal
      • ~10 days
      • Cough
    • Paroxysmal
      • Whooping cough
    • Convalescent
  • Duration
    • Extremely long (100 days)
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14
Q

Campylobacter jejuni

A
  • Microbiology
    • Gram-
    • Curved
    • Motile
  • Epidemiology
    • Sporadic: poultry
    • Outbreak: unpasteurized milk
  • Pathophysiology
    • Multiplies in bile-rich upper intestines
      • Damage to jejunum, ileum, and colon
    • Invades mucosal epithelium
    • Humoral and cell-mediated immunity important in prevention
  • Presentation
      • Diarrhea
        • Most common cause of childhood bacteria
        • Presents another peak in adulthood (~age 30)
    • Mimics Crohn’s disease
    • Abdominal pain (similar to appendicitis)
    • Fever
    • Not much nausea and vomiting
  • Guillan-Barre Syndrome (GBS)
    • Potential post-infection complication
    • Cross-reactivity between LPS and peripheral nerve myelin, resulting in paralysis
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15
Q

Helicobacter pylori

A

Microbiology

  • Gram-
  • Spiral-shaped
  • Urease positive

Epidemiology

  • 50% of world’s population infected
  • Lives beneath mucous layer but does not invade tissue

Pathogenesis

  • VacA - cytotoxin
  • CagA - necessary for VacA expression

Presentation

  • Gastritis
  • Peptic ulcers
  • Asymptomatic colonization for decades
16
Q

Francisella tularensis

A

Microbiology

  • Gram-
  • Possesses B-lactamase
  • Requires cysteine

Epidemiology

  • Mid-western young males
  • Transmission
    • Tick or insect bite
    • Aerosols during skinning of animals (particularly rabbits)
    • No human-to-human transmission

Pathogenesis

  • Intracellular parasite of hepatocytes, macrophages, and endothelial cells
  • Prevents fusion of phagosome and lysosome
  • Humoral immunity insufficient; cellular immunity

Clinical Presentations

  • 30 days
  • Presents similar to TB (granulomas)
  • Papular lesion at site of bite; followed by focal necrosis of the lesion (papule-ulcer)
  • Pulse-temperature deficit (fever with decreased pulse)
17
Q

Legionella pneumophila

A

Microbiology

  • Gram-
  • Distinct, branched-chain fatty acids in cell wall
  • Unencapsulated

Epidemiology

  • Lives in water
  • Unaffected by chlorine
  • Individuals with impaired ciliary clearance (smoking, immunosuppression)

Pathogenesis

  • Bacteria enter humans via inhalation
  • Alveolar macrophages phagocytose the bacteria
  • Mip protein prevents fusion of phagosome with lysosome
  • Bacteria multiply until phagosome ruptures
  • Primary defense is cellular immunity; IFNγ causes monocytes to no longer support intracellular multiplication of Legionella by downregulating transferrin

Clinical Manifestations

    • Pneumonia
  • High fever
  • Diarrhea
  • Pontiac Fever
      • Caused by inhalation of only toxin
    • Results in fever only (no pneumonia)
19
Q

Bartonella

A

Microbiology

  • Stain black with Warthin-Starry

Epidemiology

  • Cat-scratch disease
  • Trench fever
  • Body louse

Clinical Manifestations

  • Regional lymphadenopathy
20
Q

Shigella

A

Microbiology

  • Gram-

Epidemiology

  • Cause of bacillary dysentery
  • Spread via fecal-oral contact and flies

Pathogenesis

  • Does not invade beyond colonic mucosa
  • Secretes toxins that damage and destroy colon lining

Clinical Presentation

  • Frequent passing of stools (5-7 times a day)
  • Blood and mucus in stools
  • Abdominal pain
  • Fever >48 hours
  • Bacteria excreted for 1-4 weeks
21
Q

Yersinia enterocolitica

A
  • Microbiology
    • Gram-
    • Resistant to serum complement
  • How You Get It
    • Winter-time
    • Undercooked pork
    • Fecal-oral transmission
    • Contaminated blood
  • Pathogenesis
    • Organisms are ingested
    • Invasion of intestinal epithelium (Peyer’s patches)
      • Invasin
      • Attachment invasion locus
      • YadA
  • Clinical Manifestations
    • 1-3 weeks
    • Fever
    • Diarrhea
    • Abdominal pain (mirroring that of appendicitis)

M&I (32 decks)

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