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Haemophilus Flashcards

1
Q

Name the general characteristics of Haemophilus spp.

A
  • Fam = Pasturellaceae
  • Sm, non motile, pleomorphic GNB
  • Faculative anaerobes, 5-7% CO2 enriched atmosphere
  • Require X factor or V factor to grow
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2
Q

Epidemiology and mode of transmission for Haem spp.

A
  • NF of upper resp. tract

- Endogenous strains (opportunistic)

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3
Q

Pathogenesis and virulence of Haem. spp.

A
  • Otitis media, sinusitis, conjunctivitis
  • Not encapsulated
  • low virulence factors (uncertain)
  • Opportunistic (endogenous)
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4
Q

Haemophilus influenzae; epidemiology + mode of transmission.

A 
- NF of URT
2 categories:
- Typable (systemic + life threatening)
- Non-typable (localized)
- Type b are most serious infections (has vaccine)
  • Person to person (resp. droplets)
  • Endogenous strains (into sterile sites)
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5
Q

Haemophilus influenza - Typable

A

Based on capsular characteristics:

  • Cap. = sugar alcohol phosphate complex
  • 6 groups: a,b,c,d,e, f
  • HIB (H.influenzae type b); most common encountered serious infections in humans
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6
Q

Haemophilus influenza - non-typable (NTHi)

A
  • No capsule = normal inhabitants of URT
  • Encapsulated = meningitis, epiglottitis, cellulitis w/ bacteremia, septic arthritis, pneumonia
  • Non-encapsulated = localized infection, otitis media, sinusitis, conjunctivitis
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7
Q

What are the virulence factors of H.influenzae?

A

Capsulated

  • protected from phagocytosis (usually HIB)
  • Additional cell envelope factors help with attachement to host

Non-encapsulated
- Pili and other cell surface factors mediate attachment

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8
Q

H. parainfluenzae; epidemiology and mode of transmission

A
  • NF of URT

- Endogenous strains (opportunistic)

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9
Q

H. parainfluenzae; pathogenesis and spectrum of disease.

A
  • Low pathogenicity, occasionally causes endocarditis
  • Similar infections as H. influenzae
  • Most common of Heam spp.
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10
Q

H. parainfluenzae; virulence factors

A
  • Similar to Haem. spp.

- No capsules

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11
Q

H. ducreyi; epidemiology and mode of transmission

A
  • NOT NF, only in humans during infection

- Person to person; sexual contact

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12
Q

H. ducreyi; pathogenesis and spectrum of disease

A

Chancroid

  • symptoms=genital lesions, to ulcers and inguinal lymphadenopathy
  • Confused w/ syphilis
  • More common in tropics, or socially disadvantaged pops.
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13
Q

H. ducreyi; virulence factors

A 
Uncertain but could be:
- Capsular factors
- Pili
- Toxins
(involved in attachement to host)
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14
Q

Name some other Haemophilus infections:

A

Formerly called: Haemophilus aphrophilus

  • “H” of HACEK group
  • SBE (subacute bacterial endocarditis)
  • NOW: Aggregatibacter aphrophilus
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15
Q

How is Haemophilus isolated?

A
  • Nasal washes and/or nasopharyngeal swabs

- Susceptible to drying and temp extremes (culture to correct media asap

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16
Q

How is collecting for H. ducreyi different?

A
  • Clean ulcer, swab w/ phosphate buffered saline

- Culture to special selective media w/in 10 mins

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17
Q

What to be cautious about during Gram stain

A
  • Centrifuge to concentrate
  • Coccobacilli of sm bacili stain pale, can be difficult to pick out from pink background
  • Be careful not to over decolorize
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18
Q

Gram of H. influenzae:

A

Pleomorphic coccobacilli or sm. rods

19
Q

Gram of H. parainfluenzae

A

Sm .pleomorphic rods/long filaments

20
Q

Gram of H. haemolyticus

A

Sm coccobacilli/ short rods w/ occasional cells appearing tangled

21
Q

Gram of H. parahaemolyticus

A

Short/medium length bacilli

22
Q

Gram of H. ducreyi

A

Slender/ coccobacilli (school of fish)

23
Q

Gram of A. aphrophilus

A

Very short bacilli, occasionally filamentous

24
Q

What stain is used in fluorescent microscopy?

A

Acridine orange stain (small #’s)

25
Direct detection: Particle agglutination assays
- Detects Type b capsular polysaccharide - CSF and urine (Gram is reliable) - False pos if recent Hib vaccination
26
When are molecular techniques used and why?
- Rapid screening for CSF, serum, urine, plasma, WB - Sensitive methods for H.ducreyi - Pulsed-field gel electrophoresis is gold standard for typing
27
Plates used to culture Haem spp.
5% BA w/ SS, CHOC, MAC
28
Which broths will H. influenzae and H. parainfluenzae grow in?
Thioglycolate and BHI broth
29
What conditions will Haemophilus spp. grow in?
- best growth in 5-10% CO2 | - 35-37 C, will gorw in 24 hrs, usually held for 72
30
How do you culture H. ducreyi?
Requires growth factors - MH based CHOC w/ 1% Isovitalex and 3ug/L vancomycin - HI based agar w/ 10% fetal bovine serum and 3ug/L vanco (inhibits GP) - Inc at 33 C, with high humidity - 2-7 days incubation
31
Haem spp.; post incubation appearance:
BA: NG (H.i needs X and V; H.p needs V) MAC: NG CHOC: sm-med, smooth grey, buff/slight yellow. H.influenzae CHOC: Mucoid and larger if capsule, no capsule; sm, smooth and translucent @ 24hr
32
Common ID for Haem. spp.?
- Gram - +/- hemolysis on horse/rabbit blood - Growth on CHOC in CO2 and NG (or satellites) on BA - X/V growth requirements - Porphyrin test - Rapid sugar fermentation - Serotyping (rule out/confirm type b
33
How to do satellitism test:
- Sheep BA - Streak sample - Use Staph for "Y" streak (lysis RBC's in agar, releasing X and V) - Incubate 5-10% CO2 - Look for very tiny colonies growing close to source of NAD
34
How do you determine X and V growth requirements?
- MH, nutrient agar, heart infusion agar or TSA - Streak organism (0.5 McFarland standard) - Apply X, V and XV disks/strips - Incubate at 35 C overnight in ambient air
35
Results for X and V requirements; H. influenzae
Growth only around XV
36
Results for X and V requirements; H. parainfluenzae
Growth around V and XV
37
Results for X and V requirements; H. ducreyi
Growth around X and XV
38
Explain porphyrin test:
- Determines org's ability to synth X factor - Tests for enzyme; porphobilinogen synthase - Subsrate: ALA (δ-aminolevulinic acid) - Products: porphyrins and protoporphyrins
39
Positive and negatives for porphyrin test?
``` Pos = H. parainfluenzae Neg = H. influenzae ```
40
AMS for H. influenzae
- Resistant to ampicillin - Life threatening infections: Usually suscept. to 3rd gen cephalosporins - Localized infections: Usually several cephs, beta-lactam/lactamase inhibitor combos, macrolides, SXT, some fluoroquinolones
41
AMS for H. ducreyi
- Resistance to SXT, tetracyclines, beta-lactamse (ampicllin + amoxacillin) - Treat w/ erythromycin, sometimes ceftriaxone + ciprofloxacin
42
AMS for Haem spp.
- Beta-lactamase resistance to ampicillin | - Treat w/ same as H.i
43
AMS conditions/requirements:
- Haemophilus test medium (HTM) - Capnophilic (5-7% CO2 - 16-18 hrs

Micro II (6 decks)

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