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Microbiology Part 1 > Lec10 Atypical Pneumonia > Flashcards

Lec10 Atypical Pneumonia Flashcards

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1
Q

What are signs of typical pneumonia?

A
  • abrupt onsent
  • productive cough
  • copious sputum
  • evidence of consolidation on exam
  • high WBC count
  • distinct infilitrate on chest xray
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2
Q

What are signs of atypical pneumonia?

A
  • insidious onset
  • extrapulmonary symptoms [headahces, muscle aches]
  • usually no consolidation on exam
  • fever rarely > 101
  • normal WBC
  • less distinct infiltrate on chest xray
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3
Q

What are 3 most frequent causes of atypical pneumonia?

A
  • mycoplasma pneumoniae
  • chlamydophila pneumoniae
  • legionella species
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4
Q

What are some other common etiologies of atypical pneumonia [besides the 3 main bacteria]?

A
  • coxiella burnetii [q fever]

- respiratory viruses

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5
Q

What is epidemiology of mycoplasma pneumoniae?

A
  • in mini outbreaks in households
  • incubation 2-3 wks
  • gives young children URI, others primary penumonia
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6
Q

How is mycoplasma pneumoniae transmitted?

A
  • by respiratory droplet
  • need close contact
  • much longer incubation than viral infections
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7
Q

What is structure of mycoplasma pneumoniae? shape? gram stain? etc?

A
  • lacks cell wall
  • contains RNA and DNA
  • short rod-shaped
  • not visible on gram stain
  • can grow on cell free medium
  • long doubling time so takes many days to grow in culture
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8
Q

What are extrapulmonary manifestations of mycoplasma pneumoniae?

A
  • hepatitis
  • hemolysis
  • rash [erythema multiforme]
  • rarely: myocarditis, encephalitis
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9
Q

What are the virulence factors of mycoplasma pneumoniae? who is particularly at risk?

A
  • virulence factors located intracellularly
  • patient age relates to likelhood of progression —> adolescent, young adult, elderly more at risk
  • high disease rate [and more severe infection] in sickle-cell disease
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10
Q

What is the host immune response to mycoplasma pneumoniae?

A
  • polyclonal T cell and B cell activation

- variety of antibodies produced including antibodies [cold agglutins]

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11
Q

What are cold agglutinins?

A
  • autoantibodies produced in immune response

- IgM antibodies directed at the I antigen on RBC surface

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12
Q

What are the clinical manifestations of mycoplasma pneumoniae?

A

respiratory: upper to lower
skin: erythema multiforme
cardiac: arrythmia, CHF
neuro: meningitis
other: renal, liver, musculoskeletal

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13
Q

How do you diagnose mycoplasma pneumoniae infection?

A
  • usually on clinical basis
  • can use complement-fixing antibodies to confirm diagnosis retrospectively
  • culture techniques and cold-agglutinin test not useful [not specific/sensitive/too cumbersome]
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14
Q

How do you treat mycoplasma pneumoniae?

A
  • no cell wall so can’t use penicillins/cephalosporins
  • use macrolides [erythromycins] or tetracyclines
  • most cases undetected or untreated
  • no vaccine
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15
Q

What is epi of chlamydophila pneumoniae

A
  • associated with epidemics

- older the host –> more likely to cause lower rather than upper respiratory infection

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16
Q

How is chlamydophila pneumoniae transmitted?

A

by respiratory droplets

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17
Q

What is structure/shape of chlamydophila pneumoniae?

A
  • intracellular bacteria
  • have cell walls
  • not seen on gram stain
18
Q

What is the elementary body vs reticulate body of chlamydophila pneumoniae?

A

elementary body = metabolically inacive infectious form, can survive outside the cell

one inside the cell it becomes the reticulate body = starts replicating

19
Q

What are the virulence factors for c. pneumoniae?

A
  • no specific virulence factors identified

- located intracellularly

20
Q

What is the pathogenesis of c. pneumoniae?

A
  • enters via respiratory tract

- can persist in respiratory epithelial cells for prolonged period before and after acute infection

21
Q

What are the clinical signs of chlamydophila pneumoniae?

A
  • commonly asymptomatic
  • patchy pneumonia without fever
  • occassionaly upper respiratory symptoms [rhinitis, sore throat]
  • persistent cough
  • otisis, and rarely pericarditis or pleuritis
  • may be implicated in atherosclerosis
22
Q

How is c. pneumoniae diagnosed?

A
  • usually presumed from clinial signs
  • can use IgM antibody to detect recent infection in serum
  • can use IgG antibody to detect remote or recent infection
23
Q

How is c. pneumoniae treated?

A
  • teatracyclines, macrolides [clarithromycin, azithromycin], newer fluroquinolones
24
Q

How is legionella pneumophila transmitted?

A
  • lived in aqueous habitats
  • transmit to humans though inhalation following aerosolization
  • no person-person transmission
  • incubation = 2-10 days
25
Q

What is structure of l. pneumophila? gram?

A
  • small bacilli
  • gram negative [but weakly]
  • aerobe
  • fastidious growth –> need special media to isolate
  • 16 serotypes but group 1 causes most human infections
26
Q

What are the virulence factors of l. pneumophila?

A
  • variety of toxins and protease
  • on surface:
  • – pili promote adherence to target cell
  • – flagellae promote entry into cell
  • – macrophage infectivity promoter protein
27
Q

What is the pathogenesis of L. pneumophila infection?

A
  • organism reaches lung and phagocytoses by alveolar macrophages
  • grows in cell and eventually kill and infect other macrophages
  • neutrophils infiltrate alveoli and fluid leaks from capillaries into interstitium of lung
  • sever inflammatory cytokine response to dying macrophages
28
Q

What type of host immune response?

A

both cellular and humoral

29
Q

What are the clinical signs of L. pneumophila?

A
  • prodromal illness [fever, malaise]
  • mild to life threatening pneumonia
  • hepatitis, rhabdomyolosis, renal failure, abscesses, altered mental status etc
  • may start with altered mental status and diarrhea
30
Q

How is L. pneumophila diagnoses?

A
  • culture respiratory secretions on selective media [buffered charcoal yeast extract, use silver stain]
  • detect antigen of serogroup 1 in urine
  • direct fluorescent antibody staining of respiratory secretions
  • insensitive to serum antibody test
31
Q

How is L. pneumophila treated?

A
  • macrolides [azithromycin], tetracyclines, fluoroquinolones [levofloxacin]
  • high mortality in immunocompromised and elderly
32
Q

What are the two macrolide antibiotics?

A
  • clarithromycin

- azithromycin

33
Q

What is mech of action of macrolides [clarithromycin, azithromycin]? bacteriostatic or bactericidal?

A
  • bind 50s ribosomal subunit
  • inhibit RNA-dependent protein synthesis
  • bacteriostatic
34
Q

What are the PK properties of clarithromycin? [oral or intravenous, half life, elimination]

A
  • given orally
  • metabolized by liver
  • 30% excreted unchanged in urine
  • 3-4 hr elimination half life
35
Q

What are the PK properties of azithromycin? [oral or intravenous, half life, elimination]

A
  • given orally or intravenously
  • if orally needs to be on empty stomach [food interferes with absorption]
  • wide distribution in tissues, 2-4 day elimination half life
  • eliminated unmetabolized through bile
36
Q

What toxicities associated with macrolides?

A

frequent: diarrhea, nausea, abdominal pain

less frequent: dizziness, temporary hearing loss, ventricular arrhythmia

37
Q

What are the 3 fluroquinolone antibiotics?

A
  • moxifloxacin
  • levofloxacin
  • ciprofloxacin
38
Q

Mech of action of fluoroquinolones?

A
  • inhibit DNA synthesis by:
  • inhibiting DNA gyrase
  • inhibiting topoisomerase IV
39
Q

What are the PK properites of fluoroquinolones? [oral or intravenous, half life]

A
  • all 3 given orally or intravenously
  • absorbed well from GI
  • reach high conc in all tissues with long half lives
40
Q

How is levofloxacin eliminated? ciprofloxacin? moxifloxacin?

A

levo and cipro by kidneys

moxi primarily via liver in the bile

41
Q

What toxicities associated with fluoroquinolones?

A

most frequent: anorexia, nausea, vomiting, abdominal pain, diarrhea
less frequent: headache, dizziness, cartilage erosions, tendonitis/tendon rupture, mania, seizures, hallucination
- avoided in peds because of potential effect on growing cartilage

42
Q

If you have GI problems, confusion and 2-3 days later get pneumonia what should you think?

A

legionella!

Microbiology Part 1 (24 decks)

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