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Microbiology Unit II > 4 Bacterial PNA 1 & 2 > Flashcards

4 Bacterial PNA 1 & 2 Flashcards

1
Q

Pneumonia is defined as …

A

Inflammation of the lung and parenchyma, including the alveoli, respiratory bronchioles, etc

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2
Q

PNA with involvement of the entire lobe

A

Lobar pneumonia

Bronchopneumonia is just the bronchi?

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3
Q

PNA is usually due to an infectious agent, such as…

A

BACTERIA
Fungi
Viruses
Parasites

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4
Q

6th leading cause of death in the US

A

PNA - most common infectious cause of death

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5
Q

How does mortality rate from PNA different in outpatient vs inpatient settings?

A

1% in outpatient

Up to 25% in infections requiring hospital admission

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6
Q

The two major categories of PNA

A

Hospital acquired (nosocomial) - develops within 72 hours of admission

Community acquired (CAP)

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7
Q

Community acquired PNA is further subdivided into what two categories?

A

Typical (usually Strep pneumo, H flu, K pneumo, or Staph aureus)

Atypical (usually Zoonotic, nonzoonotic, or with extrapulmonary involvement)

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8
Q

3 zoonotic pathogens that cause atypical PNA

A 
Chlamydia psittaci (psittacosis)
Francisella tularensis (tularemia)
Coli Ella burnetii (Q fever)
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9
Q

3 non-zoonotic pathogens that cause atypical PNA

A

Chlamydia pneumoniae
Mycoplasma pneumoniae
Legionella pneumoniae

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10
Q

Atypical PNA is usually unresponsive to …

A

ß-lactams

Also, difficult to diagnose

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11
Q

Typical or Atypical PNA: Sudden onset

A

Typical

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12
Q

Typical or Atypical PNA: Gradual onset

A

Atypical

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13
Q

Typical or Atypical PNA: Sick appearing, high fever (>103)

A

Typical

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14
Q

Typical or Atypical PNA: Well appearing, lower fever (<103)

A

Atypical

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15
Q

Typical or Atypical PNA: Chills/shaking

A

Typical

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16
Q

Typical or Atypical PNA: Productive cough

A

Typical

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17
Q

Typical or Atypical PNA: Non-productive cough

A

Atypical

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18
Q

Typical or Atypical PNA: Pleurisy

A

Typical

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19
Q

Typical or Atypical PNA: Consolidation (well-defined infiltrates)

A

Typical

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20
Q

Typical or Atypical PNA: Patchy, ill-defined infiltrates

A

Atypical

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21
Q

Typical or Atypical PNA: Chest pain, SOB

A

Typical

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22
Q

Typical or Atypical PNA: Body aches, diarrhea, abdominal pain

A

Atypical

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23
Q

Gram-positive, lancet-shaped diplococcus

A

Streptococcus pneumoniae

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24
Q

Alpha-hemolytic colonies

A

Streptococcus pneumoniae

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25
Q

Green colonies on blood agar

A

Streptococcus pneumoniae

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26
Q

Optochin sensitivity

A

Streptococcus pneumoniae

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27
Q

Encapsulated strains are virulent

A

Streptococcus pneumoniae

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28
Q

_________ increase the risk of pneumococcal pneumonia

A

Viral infections (more common in colder, wetter months)

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29
Q

The major reservoir of Streptococcus pneumoniae infections

A

Asymptomatic carriers (because it’s an irregular normal flora component)

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30
Q

Major virulence factor for Streptococcus pneumoniae

A

Capsule

Basis for serotyping (90 serotypes) and the basis for anti-pneumococcal vaccines

Inhibits phagocytosis by interfering with complement activity and preventing C3b opsonization

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31
Q

Other protective virulence factors for Streptococcus pneumoniae besides the capsule

A

IgA Protease - degrades host secretory IgA

Hydrogen peroxide —> apoptosis in host cells and elimination of competing bacteria

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32
Q

Other binding virulence factors for Streptococcus pneumoniae

A

Pili - contributes to the colonization of the upper respitatory tract and activates production of large quantities of TNF

Surface Proteins - Choline binding proteins (Adhesins that interact with the carbs on the surface of pulmonary epithelial cells)

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33
Q

What is the Peptidoglycan-teichoic acid complex?

A

A Streptococcus pneumoniae virulence factor that illicit a significant immune response and acts as a potent immunomodulator

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34
Q

What is Pneumolysin?

A

Another Streptococcus pneumoniae virulence factor

Interacts with target cell membrane to form transmembrane pores —> cell lysis and activation of complement

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35
Q

What is Autolysin

A

Another Streptococcus pneumoniae virulence factor that causes lysis of pneumococcus and results in the release of pneumolysin

Released in response to antibiotic therapy and stationary phase

Is an attempt by the organism to dampen host immune response

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36
Q

What is the pathogenesis of a Streptococcus pneumoniae infection?

A

Pneumococcus enters respiratory tract through aspiration

Multiplies in tissue (stimulates immune response to cellular components)

Multiplication results in disease from heightened immune response

PNA develops, possibility for hematogenous spread via lymphatic drainage in lungs

Fibrinous edema fluid in alveoli —> red cells and leukocytes —> tissue consolidation

Resolution occurs with the absorption of fluid and phagocytosis of remaining cells

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37
Q

Clinical manifestations of Streptococcus pneumoniae infection

A

Sudden onset of fever

Chills

Chest pain

Productive cough with purulent RUST COLORED sputum

Bacteremia

CXR shows consolidation in lungs

Confirmed by presence of gram-positive diplococci on sputum

38
Q

Special tests to confirm Streptococcus pneumoniae and rule out others

A

Optochin sensitivity

Bile solubility (bile will lyse Streptococcus pneumoniae but no effecton other alpha-hemolytic strep)

Quelling reaction to observe capsules

Agglutination tests for capsular polysaccharides

Genetic probe test

39
Q

DOC for Streptococcus pneumoniae infection

A

Penicillin G used in empiric therapy - but resistance is becoming common

40
Q

What is the difference between the two pneumococcal vaccines?

A

23-valent capsular polysaccharide represents 85-90% of the infections in US - recommended for persons >65 or other predisposing factors

13-valent capsular polysaccharide covers >80% of infections in children 6 years and younger, conjugated to a carrier protein

41
Q

Non-motile, gram-negative bacillus coated by a thick slimy capsule

A

Klebsiella pneumoniae

Can cause both typical CAP and NP

42
Q

Klebsiella pneumoniae is more common in what populations?

A

Alcoholics and DM

Often seen in the homeless population

43
Q

Primary virulence factor for Klebsiella pneumoniae

A

Polysaccharide capsule (antiphagocytic, prevents MAC-mediated lysis)

Also ADHESINS (either fimbrial or non-fimbrial)

44
Q

Aggressive necrotizing CAP with predilection for the upper lobes, causing severe illness with rapid onset high fever

A

Klebsiella pneumoniae

Patients will often have productive cough with a thick, blood tinged sputum (Currant jelly sputum)

Often fatal, even with abx treatment

45
Q

Diagnosing Klebsiella pneumoniae

A

Gram stain/cuture showing mucous capsule

Presence of currant jelly sputum

Cavitation on CXR

46
Q

Treatment of Klebsiella pneumoniae

A

Empiric therapy used due to rapid progression of disease

Susceptibility testing required as it is ß-lactamase producing

Combo treatments with:
• Aminoglycosides
• 3rd gen cephalosporins
• Fluoroquinolones

47
Q

Non-motile, gram-negative coccobacillus that can be either encapsulated or non-encapsulated

A

Haemophilus influenzae

Has ability to lose its capsule (non-typeable H. influenzae) but is still capable of causing disease

48
Q

Contains lipooligosaccharide in cell wall

A

Haemophilus influenzae

Functions as a virulence factor similar to LPS

49
Q

Colonies of this bacterium require factors from RBCs for growth but do not have hemolytic properties

A

Haemophilus influenzae

50
Q

Most strains of Haemophilus influenzae are classified as …

A

Opportunistic pathogens

Nontypeable Haemophilus influenzae is part of the normal flora in ~80% of the population

51
Q

Type B of this bacterium can cause pneumonia in infants and young children

A

Haemophilus influenzae

Causes 2-4% of Haemophilus influenzae-related pneumonia’s

52
Q

Haemophilus influenzae virulence factors

A

Polyribosylribitol phosphate (PRP) capsule*** (renders it resistant to phagocytosis by PMNs

Neuraminidase

IgA protease

Fimbriae (required for successful colonization in the nasopharynx

LOS

53
Q

Satellite growths on blood agar

A

Haemophilus influenzae

Only possible in co-infections

Colonies of Haemophilus influenzae will appear as convex smooth, pale, grey or transparent colonies

54
Q

Test to detect Haemophilus influenzae other than culture

A

ID-Latex Particle Agglutination test (LAT)

Easier to achieve definitive results than other culture methods

Relies on antigen, not viable bacteria

Can be used during or following abx treatment***

55
Q

Treatment of Haemophilus influenzae

A

Treated typically with ß-lactams (ie augmentin)

If resistance or highly invasive infections, consider 3rd gen cephalosporins (will also cross BBB)

Preventable through the use of one of three different Hib conjugate vaccines

56
Q

Smallest free-living bacteria

A

Mycoplasma pneumoniae

Cause of atypical CAP

57
Q

Due to its lack of cell walls, Mycoplasma pneumoniae is …

A

Pleomorphic in shape

Has a “fried egg” appearance in culture on many different media

58
Q

Bacteria with plasma membranes containing sterols

A

Mycoplasma pneumoniae

Aerobic and looks like our cholesterol so easily evades immune system

59
Q

SSx of Mycoplasma pneumoniae infection

A

Non-productive cough that lasts 1-2 months, fever (but not usually in children under 5), crackles, headache and chest pain

Relapses common - infection does not produce long lasting immunity

60
Q

Pathogenesis of Mycoplasma pneumoniae infection

A

Organism adheres to epithelium and releases hydrogen peroxide, resulting in damage to epithelium

Prevents clearance of airway and results in colonization of airways

Evades immune system by fusing to host cell membrane (via sterols), disguising itself

Can also cause otitis, rhinitis, pharyngitis, and tracheobronchitis

61
Q

Mycoplasma pneumoniae generally targets people in what age range?

A

5-20 years

Very common transmission between family members, outbreaks common in crowded conditions

Humans are the only reservoir

62
Q

Transmission of Mycoplasma pneumoniae is via…

A

Respiratory droplets (person-to-person)

63
Q

How is Mycoplasma pneumoniae diagnosed?

A

Chest X-ray: patchy infiltrates (not lobar consolidation)

Culture from sputum

COLD AGGLUTININ ASSAY - detects IgM antibodies that bind to the I antigen on the surface of RBCs at 4˚C (not specific though)

64
Q

DOC for Mycoplasma pneumoniae

A

Azithromycin/Tetracycline

65
Q

Tiny, non-motile, coccoid shaped bacteria that exist as obligate intracellular parasites and cause atypical pneumonia

A

Chlamydophila pneumoniae

They’re gram-negative, in case you were wondering

66
Q

Chlamydophila pneumoniae exists in what two forms?

A

Elementary bodies (EB) - the infectious form

Reticulate bodies (RB) - the intracellular form

67
Q

How does the Chlamydophila pneumoniae life cycle work?

A

Chlamydophila elementary body enters lung cell

Elementary body becomes reticulate body

Replication occurs

Reticulate body becomes elementary body and is released to reinfect other cells

68
Q

Clinical SSx of Chlamydophila pneumoniae infection are a result of what?

A

Direct tissue destruction during intercellular bacterial replication, in addition to inflammatory response

Possesses at least 2 exotoxins as well

Primary response is by neutrophils (immunity not long lasting)

Patients may be asymptomatic or present with mild symptoms (persistent non-productive cough and malaise, with UNILATERAL lower lobe involvement)

69
Q

Chlamydophila pneumoniae occurs mostly in …

A

Adults 60+ years

Transmitted person-to-person via respiratory droplets (humans are the only reservoir)

70
Q

The cell culture for this bacterium is difficult and time consuming

A

Chlamydophila pneumoniae

Dx relies on clinical manifestations and history, along with cell culture and microscopy (looking for inclusions), serology, and PCR

71
Q

DOC for Chlamydophila pneumoniae

A

Tetracycline/erythromycin

72
Q

How did Legionella pneumophila get its name?

A

Outbreak at an American Legion Convention in Philadelphia in 1976

There are 48 species and 70+ serogroups in genus Legionella

90%+ of all human infections result from one species (Legionella pneumophila), most are serogroup 1

73
Q

What does Legionella pneumophila look like?

A

Thin, gram-negative pleomorphic bacillus

Also has:
• Fimbriae
• Single, polar flagellum
• ß-lactamase producer

74
Q

Humans are infected with Legionella pneumophila by…

A

Inhalation of aerosolized contaminated water

75
Q

What is the pathogenesis of Legionella pneumophila?

A

Bacterial cells are opsonized with C3b, facilitating their phagocytosis, but survive intracellularly by inhibiting phagolysosome fusion

Bacterial replication occurs inside phagosome

Host cell is killed when phagosome lyses, releasing toxic enzymes

Bacteria are released upon cell lysis

76
Q

A self-limited illness resulting from Legionella pneumophila infection with Sx lasting 2-5 days and resolving spontaneously w/o treatment

A

Pontiac Fever

SSx:
Fever
Chills
Malaise
Myalgia
HA
No Sx of PNA
77
Q

A severe, acute atypical PNA with a high mortality rate (up to 75% w/o treatment), acquired by inhalation of aerolized bacteria

A

Legionnaires’ Disease (Legionella pneumophila)

2-10 day incubation period —> abrupt onset of Sx:
Fever
Chills
Dry/nonproductive cough
HA
GI and Neuro Sx** differentiates it from other PNAs

Death is due to shock or respiratory failure

78
Q

Pathogenesis of Legionnaires’ Disease

A

Entry of bacilli into macrophages —> multiplication inside macrophage —> death of macrophages —> release of chemotactic factors —> influx of monocytes and PMNs —> increased serum proteins, deposition of fibrin in alveoli, and release of enzymes and cytokines

End result? Acute FIBROPURULENT NECROTIZING PNA

79
Q

Where is Legionella pneumophila widespread?

A

Moist environments

Rivers, streams, potable water, sewage, shower heads, cooling towers, other public water supplies

In nature, the bacteria survive and replicate within protozoan

80
Q

Risk factors for Legionella pneumophila infection

A

Presence of a LARGE inoculum (not very virulent) AND

Any compromise in pulmonary and/or immune function:
• Smoking
• Chronic heart disease
• Chronic lung disease
• Immunosuppression
• Elderly
•Alcoholics

Immunity appears to be long-lasting

81
Q

What medium is used for Legionella pneumophila cultures?

A

Buffered Charcoal Yeast Extract (BCYE) - it is the only clinical isolate that will grow on it

82
Q

How else is Legionella pneumophila diagnosed if not with a culture?

A

Rapid test for antigen in the urine (EIA test)

High sensitivity, but only detects infections with serotypes 1

83
Q

Treatment for Legionella pneumophila

A

DOC: Levofloxacin or other fluoroquinolones
If <8 years, give em a z-pack

Severe disease requires careful management and supportive therapy

No treatment necessary for Pontiac fever

84
Q

Describe Pseudomonas aeruginosa

A

Gram-negative, aerobic, motile bacillus with a single flagellum

Clinical isolates possess pili as well

Blue-green in color due to Pyoverdin and Pyocyanin

85
Q

Primary bacterium used in bioremediation

A

Pseudomonas aeruginosa

For treatment of sewage, oil spills etc to break down bacteria

86
Q

What is Pyocyanin

A

“Blue pus” pigment in Pseudomonas aeruginosa

Catalyze ROS production —> tissue damage

VIRULENCE FACTOR

87
Q

What is Pyoverdin

A

Green fluorescent pigment found in Pseudomonas aeruginosa

Not a virulence factor but gives it a very distinctive appearance

88
Q

What are the virulence factors for Pseudomonas aeruginosa?

A

Pyocyanin (ROS production)

Exotoxin A (A-B toxin —> inhibition of protein synthesis —> ciliastasis and immunosuppression)

Elastases (LasA and LasB) - work synergistically to destroy elastin in the lungs (lose ability to expand/contract —> no gas exchange)

Alginate (mucous polysaccharide/slime layer) - inhibits mucociliary escalator

Pili (attachment to host)

LPS (endotoxin) —> fever, shock, DIC, tissue necrosis

89
Q

Where does Pseudomonas aeruginosa come from

A

Widespread in the environment - inhabits plants, water, and moist soil

Frequent or transient carriage on skin and in feces

An opportunistic pathogen in the hospital

Transmission occurs via fomites, plants, fruits, hands

90
Q

Because Pseudomonas aeruginosa is not very virulent, infection requires what?

A

A significant break in normal defenses - generally in a immunocompromised host

Can cause a variety of infections:
UTI
PNA (esp after vent)
Eye, ear, and skin (from contaminated hot tub, contact lens)
Burn patients
CF (common cause of death)
91
Q

What media support the growth of Pseudomonas aeruginosa

A

BAP and MacConkey

Will produce a water-soluble blue-green pigment

Fruity smell

Patient may fluoresce or it may tinge sputum/pus

92
Q

Treatment of Pseudomonas aeruginosa

A

DO SUSCEPTIBILITY TESTING - MDR strains common

Synergistic drug combo required for successful treatment

Current DOC: Cefepime + Levofloxacin

Avoid broad-spectrum abx (b/c they suppress normal flora)

Microbiology Unit II (7 decks)

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