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Microm 442 > Lecture 13 Haemophilus, Bordetella, Mycoplasma, Legionella > Flashcards

Lecture 13 Haemophilus, Bordetella, Mycoplasma, Legionella Flashcards

1
Q

What is Haemophilus influenzae?

A

Gram-negative coccobacillus, oxidase positive, facultative anaerobe, and non-motile. Frequently encapsulated (types a-f).

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2
Q

What are some susceptible hosts of H influenzae?

A

-High rate of healthy pediatric and adult carriers
-primarily pediatric pathogen,
initial protection by maternal antibody,
-peak incidence of infection 6 mo-18 mo of age

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3
Q

What are some virulence factors of H influenzae?

A
  • pili and fimbriae for attachment
  • capsule is antiphagocytic (Type b)
  • IgA proteases
  • can cross epithelial barrier, giving it capcity for vascular invasion.
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4
Q

How is H influenzae transmitted?

A

-transmission from person to person by respiratory droplets and direct contact with resp. secretions

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5
Q

How is H influenzae treated in pediatrics?

A

-vaccine: protein-linked PRP (invoke T cells!), very effective (given @ 2 months old)

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6
Q

What are some risk factors of H influenzae infection?

A
  • complement deficiency, hypogammaglobulinemia, sickle cell anemia, functional asplenia, malignancy, HIV
  • In adults, chronic pulmonary disease, smoking, HIV alcoholism, pregnancy, malignancy
  • Socioeconomic factors: crowding, poor immunization, daycare attendance
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7
Q

What is non-typeable H influenzae?

A
  • non-capsulated strains that are common constituents of nasopharyngeal microbiota
  • cause localized disease: upper and lower respiratory tract infection, otitis media more
  • severe disease in immunocompromised
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8
Q

How does H influenzae cause Otitis Media/sinusitis?

A

-likely displacement of normal microbiota by pathogen, strains involved are frequently non-typeable

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9
Q

What is Epiglottitis (H influenzae)?

A
  • fever, sore throat, barking cough
  • Rapid progression (24 h)
  • dx by lateral neck X-ray or blood cx
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10
Q

How can H Influenzae cause Meningitis?

A
  • previous respiratory infection or various vague symptoms prior to onset
  • likely route = respiratory tract, gets into blood, gets into CNS
  • significant mortality even with antibiotic therapy, 1/3 survivors have neurological problems
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11
Q

What diseases can also occur with URI by H influenzae?

A

Cellulitis/arthritis

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12
Q

How is H Influenzae diagnosed?

A

culture and identify organism:

  • Requires X factor (hemin)
  • V factor (NAD) for growth
  • CO2 –enriched atmosphere
  • can grow on chocolate agar
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13
Q

What is Haemophilus ducreyii?

A
  • coccobacillus, often irregularly shaped with central indentation
  • Common sexually STD in developing countries
  • Enhances HIV transmission.
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14
Q

What are effect of Haemophilus ducreyii?

A

Chancroid - soft chancre, painful

  • satellite lesions
  • painful, unilateral lymphadenopathy common
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15
Q

How is H ducreyii diagnosed?

A
  • gram stain from
  • culture possible on chocolate + vancomycin (33°C, 5% CO2)
  • Must rule out syphilis by dark field and serology
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16
Q

What is Bordetella perussis?

A
  • Gram-negative coccobacillus

- specifically colonizes and destroys ciliated respiratory epithelium of large airways

17
Q

What are some virulence factors of Bordetella perussis?

A
  • Filamentous hemagluttinin (FHA) and pili for attachment
  • Tracheal Cytotoxin (TCT)
  • Pertussis toxin (PT)
  • Adenylate cyclase toxin (ACT)
  • FHA, PT, ACT expression controlled by two-component regulatory system
  • spread via aerosolized droplets
18
Q

What is TCT?

A

toxic PG-fragment destroys ciliated cells via NO and IL-1 pathway

19
Q

What is PT?

A

AB subunit toxin, ADP-ribosylates G protein leading to increased host cell cAMP -> alters lymphocyte homing and function -> lymphocytosis (high lymphocyte counts)

20
Q

What is ACT?

A

catalyzes ATP->cAMP also hemolysin

21
Q

What is whopping cough or pertussis?

A
  • Disease of Bordetella pertussis
  • severe disease for children (95%)
  • asymptomatic carriage by adolescents and adults
  • frequent cause of persistent (>2 wks) cough among adults
22
Q

What are ways to treat Whooping cough?

A
  • immunization: “P” part of DTaP (aP=acellular pertussis); administered at 2, 4, 6, 15-18 months; 4-6 yrs old)
23
Q

What are some complication to whooping cough?

A
  • pneumonia,
  • death secondary to dehydration, -malnourishment,
  • brain damage secondary to anoxia
24
Q

What is the dx of Bordetella pertussis?

A
  • clinical symptoms,
  • lymphocytosis
  • culture is optimal in 5% CO2, on selective media
  • PCR: nasal swab
25
Q

What is mycoplasma pneumoniae?

A
  • smallest free-living bacterium
  • pleomorphic filaments
  • no cell wall, cell membrane contains sterols -strict aerobe
26
Q

What diseases can M. pneumoniae cause?

A

Tracheobronchitis and pneumonia

27
Q

What group is susceptible to Tracheobronchitis and pneumonia?

A
  • predominantly children/adolescents
  • military recruits
  • college students
28
Q

What is the mechanism of infection for M. pneuomoniae in causing tracheobronchitis and pneumonia?

A
  • adhesin protein P1, necessary for attachment to ciliated respiratory epithelium
  • attaches to host glycolipid or glycoprotein on respiratory epithelial cells
  • destruction of ciliated respiratory epithelium, mucociliary escalator
29
Q

How large is M. pneumonaie genome?

A
  • Just know small compared to H. influenza and E. Coli

- small genome: 689 encoded proteins

30
Q

What is the attack rate of M. pneumonaie in the respiratory tract?

A
  • 90% cases upper respiratory tract: low fever, headache, malaise, non-productive cough
  • 10% cases lower respiratory tract:
    • tracheobronchitis
    • atypical pneumonia
    • secondary infection/superinfection
31
Q

How do you dx M. pneumonaie?

A
  • culture (slow and insensitive)
  • PCR (rapid and sensitive)
  • Serology: lack of specificity
32
Q

What is Legionella pneumophila?

A
  • pleomorphic GNR stains poorly with Gram stain
  • Environmental bacterium
  • facultative
  • intracellular pathogen (amoeba)
  • interaction with macrophage essential
  • virulence gene expression -> macrophage death
  • transmitted via contaminated aerosols
  • no documented human to human spread
33
Q

What is legionnaires disease?

A
  • headache, myalgia, rising fever, cough without much sputum, severe necrotizing pneumonia, high mortality
34
Q

What is Legionnaires disease incidences dependent on?

A

depends on water contamination; exposure to contaminated water; susceptibility of host

35
Q

What are some risk factors to Legionnaires disease?

A

smoking and chronic lung disease; increasing age, hematopoietic transplantation, other forms of immunosuppression [glucocorticoid administration] but not patients with neutropenia, acute leukemia or HIV.

36
Q

What is pontiac fever?

A
  • (Legionnella) acute febrile illness without pneumonia

- attack rate 90% (healthy and immunocompromised)

37
Q

How is legionella pneumonia diagnosed?

A
  • direct fluorescent antibody staining (DFA)
  • Gram stain (often fails
  • culture: often negative
38
Q

How is legionella treated?

A

erythromycin .

Microm 442 (16 decks)

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