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ID Week 5 > ICL 2.22: Haemophilus & Bordetella > Flashcards

ICL 2.22: Haemophilus & Bordetella Flashcards

1
Q

what’s the microbiology of haemophilus?

A

gram (-) pleomorphic

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2
Q

what’s the microbiology of bordetella?

A

gram (-) pleomorphic = coccobacilli

non-motile

obligate aerobes

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3
Q

what are the 4 bordetella species?

A
  1. B. bronchiseptica
  2. B. parapertussis
  3. B. pertussis***
  4. B. holmesii
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4
Q

what are the general characteristics of B. pertussis?

A

human pathogen only!!

whooping cough!!!

expresses PT toxin

non-motile

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5
Q

which bacteria causes whooping cough?

A

B. pertussis

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6
Q

what medium do you use for B. pertussis cultures?

A

Bordet-Gengou

they require media supplemented with charcoal, starch, blood or albumin to absorb toxic substances in common lab media

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7
Q

what are the antigenic components of B. pertussis?

A
  1. pertussis toxin (PT)***
  2. filamentous hemagglutinin (FHA)
  3. agglutinogens
  4. adenylate cyclase (CyaA)
  5. pertactin (PERT)
  6. tracheal cytotoxin (TCT)

all of these could be included in a vaccine!

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8
Q

what are the toxins associated with B. pertussis?

A
  1. pertussis toxin (PT)
  2. adenylate cyclase (CyaA)
  3. tracheal cytotoxin (TCT)

B. pertussis is a toxin mediated disease!!! so the vaccine would be against the toxins, not the bacteria itself (PT is the primary component of vaccine)

this also means that antibiotics don’t work to get rid of the symptoms, they just make sure the bacteria doesn’t continue to replicate and make more toxins

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9
Q

what is the function of adenylate cyclase?

A

CyaA is a toxin of B. pertussis

it’s anti-inflammatory and anti-phagocytic

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10
Q

what is the function of tracheal cytotoxin?

A

TCT is a toxin of B. pertussis

it damages cilia and induces IL-1

without cilia there’s no mucosal clearing

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11
Q

what is the pathogenesis of B. pertussis?

A

it’s primarily a toxin mediated disease (PT)

  1. bacteria attach to cilia of respiratory epithelial cells
  2. inflammation occurs which interferes with clearance of pulmonary secretions
  3. B.pertussis antigens allow evasion of host defences
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12
Q

what can help diagnose B. pertussis infection?

A

lymphocytosis

PT causes high lymphocytosis!

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13
Q

what are the 3 stages of a B. pertussis infection?

A
  1. catarrhal stage
  2. paroxysmal stage
  3. convalescent stage
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14
Q

what is the catarrhal stage of a B. pertussis infection?

A

1-2 weeks post infection

symptoms = rhinorrhea, sneezing, +/- fever

it’s basically just a cold so you aren’t too worried

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15
Q

what is the paroxysmal stage of a B. pertussis infection?

A

1-6 post infection

cough gets more severe and becomes intermittent

cough begins first as a dry, intermittent, irritative hack and evolves into the inexorable paroxysmal = worsening

post - tussis exhaustion is universal, post-tussis emesis is common

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16
Q

what is the convalescent stage of a B. pertussis infection?

A

weeks to months after infection

cough less frequent

symptom wanes gradually, however with subsequent respiratory illnesses over several months, paroxysmal coughing can recur

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17
Q

what are the general clinical characteristics of a B. pertussis infection?

A

insidious onset, similar to minor upper respiratory infection with nonspecific cough = slow onset

*fever usually minimal or absent throughout course

more severe disease in infants

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18
Q

is B. pertussis more severe in kids or adults? why?

A

kids, especially babies

it’s because they have smaller bronchioles that make it harder to oxygenate their bodies when the bacteria is causing inflammation in the bronchioles

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19
Q

what are some of the B. pertussis complications that can be seen in children?

A
  1. Bacterial Pneumonia
  2. Seizures
  3. Encephalopathy
  4. Epistaxis = nose bleeds
  5. Pneumothorax
  6. Subdural hematoma
  7. Hernia
  8. Rectal prolapse

literally all of these are all signs of increased pressure from all the coughing

the increased pressure from the cough can cause bleeding into the eyes or brain

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20
Q

when is B. pertussis most likely to be fatal?

A

first 6 months of life

the disease is milder than in infants and children

infact, the whoop is uncommon in adults BUT they are often the source of infection for children

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21
Q

what are the symptoms of B. pertussis in adults?

A

whoop is uncommon

usually there’s difficulty sleeping, urinary incontinence, pneumonia and rib fracture

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22
Q

what tests can you use to diagnose B. pertussis?

A
  1. PCR (swab)
  2. culture (swab)
  3. DFA (swab)
  4. serology (blood)

the problem with serology is that you can’t use it till late in the paroxysmal stage because you’re looking for antibodies and at that point it’s too late

cultures are slow but they’re the gold standard for diagnosis

however clinically, PCR is what gets used because results are in 1 hour

so PCR or NAAT of nasopharyngeal secretions is most sensitive and specific while culture is specific but not sensitive

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23
Q

how do you treat B. pertussis?

A

macrolide = erythromycin, clarithromycin, azithromycin

however, antibiotics kill the bacteria but do not neutralize the toxin –> they don’t prevent the course of the disease or prevent the cough so you just have to ride it out but you still need antibiotics to prevent bacterial multiplication

so you need supportive care

also give erythromycin for prophylaxis like if the parents of a baby are sick or any other exposure scenario

24
Q

what’s the reservoir of B. pertussis?

A

human

it’s carried in the nasopharynx

25
Q

how is B. pertussis transmitted?

A

respiratory droplets

cough, runny nose, etc.

26
Q

what is the time during which B. pertussis may be transferred directly or indirectly from an infected person to another person? aka its communicability

A

maximal in catarrhal stage

because the symptoms are non-specific and you’re just walking around thinking you have a normal URT infection

the secondary attack rate up to 80% in households –> this is why prophylaxis is important

27
Q

what are the 2 B. pertussis vaccines?

A
  1. DTaP = pediatric
  2. Tdap = adult

main component of vaccines is PT

28
Q

why do we give adults Tdap vaccines even though B. pertussis isn’t lethal in them?

A

to protect the babies!!

29
Q

what’s the immunization schedule for B. pertussis?

A

give 3 doses of DTaP before 6 months of age and a booster at 12 to 18 months and at 4-6 years

then you give 1 dose of Tdap at 11-12 years

you also give 1 dose at 27 to 36 weeks of gestation for every pregnancy

30
Q

is there antibiotic resistance with B. pertussis?

A

nope

31
Q

what are the genuses in the pasteurellaceae family?

A
  1. Haemophilus
  2. Pasteurella
  3. Actinobacillus
  4. Aggregatibacter
32
Q

what’s the microbiology of pasteurellaceae family?

A

gram (-) pleomorphic = coccobacillus

facultative anaerobe

non-motile

oxidase positive

large buttery colonies with musty odor

33
Q

in what media do pasteurellaceae grow?

A

blood or chocolate agar

they need enriched media

34
Q

what diseases is actinobacillus actinomycetemcomitans associated with?

A
  1. periodontitis
  2. endocarditis
  3. bite wound infection

this bacteria is in the pasteurellaceae family

grows slowly in blood culture

35
Q

what diseases is Aggregatibacter aphrophilus associated with?

A

endocarditis

this bacteria is in the pasteurellaceae family

grows slowly in blood culture

36
Q

which bacteria should you immediately think of when you hear dog/car scratch?

A

pasteurella multocida & canis

37
Q

how do you treat pasteurella multocida infections?

A

DOC = penicillin

if allergic, treat with doxycyline

38
Q

what are the possible complications associated with pasteurella multocida infections?

A
  1. cellulitis
  2. abscess
  3. meningitis*
  4. chronic respiratory disease

it can also cause systemic infection in the immunocompromised

so you have to treat pasteurella multocida early since it could cause meningitis

39
Q

which haemophilus species are important human pathogens?

A

all rare!

  1. H. parainfluenzae

bacteremia, endocarditis

  1. H. aegyptius

purulent conjunctivitis (pink eye)

  1. H. ducreyi

chancroid

  1. H. influenzae
40
Q

which disease does H. influenzae cause?

A

meningitis!!

41
Q

what are some of the symptoms of H. influenzae infection?

A

fever, fussy, crabby, vomiting, “not acting right”,

PE = incessant crying, altered sensorium, irritable, not consolable, seizures, neck stiffness, neurological deficit

42
Q

what would the spinal fluid micropscopy of a H. influenzae infection show?

A

little dots inside WBCs that shouldn’t be there

slide 42

43
Q

in what media does H. influenzae grow in?

A

well they’re pasturella so they need chocolate agar!

specifically they need hemin and NAD

44
Q

what are the two types of H. influenzae?

A
  1. non-encapsulated H. flu

2. encapsulated H. flu

45
Q

what are the characteristics of non-encapsulated H. flu?

A

colonizes upper respiratory tract

can spread locally to cause sinusitis, otitis media and to lower resp. tract in patients with COPD to cause pneumonia

46
Q

what are the characteristics of encapsulated H. flu?

A

more virulent form of H. influenzae! specifically, type B is the most pathogenic

95% of invasive disease is caused by type B

transient colonizers of the throat

there are polysaccharide capsules of types A to F

capsule contains Polyribitol phosphate (PRP)

47
Q

what are the virulence factors associated with H. infleunzae?

A
  1. polysaccharide capsule = anti-phagocytic (especially type b)
  2. LPS lipid A
  3. IgA1 protease
48
Q

which groups are at risk for H. influenzae infection?

A
  1. unimmunized < 4yrs of age
  2. sickle cell disease
  3. asplenia
  4. immunocompromised
  5. American Indian/Alaska Native populations
49
Q

what’s the pathogenesis of haemophilus infleunzae type B?

A
  1. organism colonizes nasopharynx
  2. in some persons organism invades bloodstream and causes infection at distant site
  3. antecedent upper respiratory tract infection may be a contributing factor
50
Q

what are the clinical features of H. influenza type B infections?

A
  1. meningitis (50%)
  2. epiglottitis
  3. pneumonia
  4. arthritis

all of these symptoms were prevaccine!!

51
Q

which age group is most susceptible to H. influenza type B infections?

A

kids!!!

incidence decreases with age

52
Q

how do you diagnose H. influenzae?

A
  1. CSF PCR
  2. microscopy gram stain of CSF, joint fluid, tissue fluid
  3. culture in chocolate agar
  4. type b capsule agglutination test in CSF replaced by PCR done at the CDC

specimen collection – depends on site of infection: sputum, blood, CSF(cerebrospinal fluid), joint fluid, etc

53
Q

how do you treat H. influenzae ?

A

DOC = 3rd gen. cephalosporins are first line for serious infections like meningitis, epiglottitis, etc = cefotaxime or ceftriaxone

could also use FQs

macrolides are NOT used in serious infection

54
Q

is there an H influenza vaccine?

A

yes

it’s the first conjugate vaccine

synthetic oligosaccharides linked to tetanus toxoid or another immunogenic protein (conjugation) is basis of current vaccine (Hib vaccine). It can be used as early as six weeks of age

55
Q

what’s the H. influenzae immunization schedule?

A

HIB vaccine:

3 doses before 6 months of age and booster at 12 to 18 months

first dose 6 – 8 weeks of age

56
Q

is there antibiotic resistance with H. influenzae?

A

yes

30% resistant to ampicillin

ID Week 5 (13 decks)

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