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MHD #3 > Neisseria, Haemophilus and Bordetella > Flashcards

Neisseria, Haemophilus and Bordetella Flashcards

1
Q

Structural Characteristics of Neisseria: Morphology and Staining

A

Gram negative “kidney bean” diplococci


Endotoxin lipopolysaccharide complexed with protein in outer membrane


Capsules and pili

intracellular

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2
Q

Neisseria in culture

A

Growth enhanced in CO2

Fastidious species require enriched media
Chocolate agar

OXIDASE POSITIVE

Classification based on measuring acid production with sugar oxidation reactions

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3
Q

classification of N. gonorrhoeae vs. N meningitidis

A

N. gonorrhoeae: maltose - , will not grow on blood agar, Pili and OMPs

N. meningitidis: maltose +, will grow on blood agar, Capsule and LPS

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4
Q

importance of complement

A

Bactericidal activity against Neisseria requires intact complement

6,000-fold increase risk for meningococcal and disseminated gonococcal disease in persons with deficiency of one or more of the terminal components
• C5, C6, C7, C8

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5
Q

N. meningitidis serogroups

A

A, B, C, Y, W-135

B- is not immunogenic

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6
Q

Neisseria meningitidis - Determinants of Pathogenicity

A
  • Pili – attachment
, Multiply at site disperse 
and invade
  • Polysaccharide capsule
    • Bloodstream invasion and survival (avoids phagocytosis until opsonized)
    • ?CNS penetration

• LPS – cell damage and systemic inflammation (causes septic shock like state)

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7
Q

Epidemiology of Meningococcal Disease

A

Developed world – sporadic cases or outbreaks in closed populations
Usually Group B
Rare community outbreak of Group A

Developing world – outbreaks of Group A or W135 predominate
Transmitted by respiratory droplets

1,000-fold ↑ attack rates in household contacts

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8
Q

Clinical Manifestations of Neisseria meningitidis Infection

A
  1. Respiratory colonization followed by overt disease or transient carrier state (immunizing event)
  2. Meningococcemia
  3. Meningitis
  4. others: pneumonia, arthritis, pericarditis, urethritis
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9
Q

meningococcemia symptoms

A

Shock
Hemorrhage
Purpura
Adrenal hemorrhage

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10
Q

meningitis symptoms

A

headache, mental status changes, neurological signs

Skin: petecheae→purpura

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11
Q

Laboratory Diagnosis: Neisseria meningitidis

A

Gram smear – CSF

Cultures (CSF, Blood, Skin)

Oxidase positive, oxidize glucose and maltose
Nonselective media (blood or chocolate agar)
Growth enhanced in CO2

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12
Q

which is more fastidious N. meningitis or N. gonhorreae ?

A

N. gonhorrea (will only grow on chocolate agar)

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13
Q

Treatment: Neisseria meningitidis

A

Penicillin – resistance is uncommon
- Ceftriaxone (normally crosses BBB better)
- Can use penicillin G if sensitive

Other cephalosporins

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14
Q

Prevention: Neisseria meningitidis

A
  1. Chemoprophylaxis – Household contacts
    - Rifampin
    - Ciprofloxacin
    - Ceftriaxone (1 dose)
  2. Vaccine – polysaccharide containing Groups A, C, Y, W-135 conjugated to diphtheria toxoid
    - Adolescents age 11-12
    - At risk adults
  3. New Serogroup B vaccines (MenB-FHbp, MenB-4C)
    - Recombinant protein vaccines
    - Recommended for very high risk only
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15
Q

Persons at Increased Risk for Meningococcal Disease
Vaccine Recommended

A

All children at age 11 (adolescent visit)

College freshman living in dormitories

Microbiologists routinely exposed

Populations in which an outbreak occurs

Military recruits

Persons with increased susceptibility

  • Asplenia
  • Terminal complement deficiency

Travelers to hyperendemic regions

  • Sub-Saharan Africa
  • Saudi Arabia
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16
Q

Structural features of Neisseria gonorrhoeae

A
  • Pili – stacked units of repeating protein 
(MW 19 kD)
  • PorB
  • Opa
  • Rmp proteins – stimulate blocking antibodies

all present in the outer membrane

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17
Q

significance of PorB in N. gonorrhoeae

A

Outer membrane protein I – Porin
Pores (channels)
Facilitate epithelial cell invasion

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18
Q

significance of Opa in N. gonorrhoeae

A

adherence proteins confer opaque appearance to colony

Opaque – localized disease (Opa expressed)
Transparent – disseminated disease

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19
Q

Antigenic Variation in Pili

A

DNA recombination involving transfer of variable sequences from unexpressed (silent) loci, pilS, to expression locus, pilE


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20
Q

Antigenic Variation in Opa

A

Up to 11 different Opa genes in genome
Switch on an off Opa genes by varying length of 5 nucleotide (CTCTT)n repeats in the leader sequence encoding the Opa gene

Alteration in number or repeats turns on or off expression

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21
Q

2 ways N. gonorrhoeae uses antigenic variation

A

altering its pili and Opa genes

22
Q

Epidemiology of Gonorrhea (how its spread)

A

Transmission across mucosal surfaces by direct contact
High rate among adolescents and young adults
Reservoir – asymptomatic (50% women, 
5+% men)

Risk
Men 20% per contact with infected woman
Women 50% per contact with infected man

23
Q

what N. gonrrohoeae uses to survive in the host/ avoid immune response

A

Antigenic and phase variation
Resist phagocytosis (Opa and pili)
Bind host transferrin, lactoferrin→iron
IgA 1 protease
Evade serum antibody and complement mediated killing
- LOS sialylation
- Rmp stimulates “blocking antibodies” (Protect other surface antigens (Por protein, LOS) )

24
Q

Gonorrhea – Clinical Disease

A

primary localized diseases - urethritis and cervicitis (can also cause proctitis, pharyngitis, conjunctivitis)

secondary (local invasion or disseminate ) – epididymitis/prostatis, endometritis/salpingitis (PIS), Arthritis, Dermatitis

25
Q

Neisseria gonorrhoeae - Laboratory Diagnosis

A

Gram stain - urethra, cervix, joint (less sensitive if from the cervix)
requires chocolate agar
oxidase positive
oxidizes glucose (NOT maltose)

PCR can now use urine samples -makes getting a sample easier

26
Q

Treatment of Gonorrhea

A
  1. Ceftriaxone ** (No Oral Treatment)
+ azithromycin (for C. trachomatis) – All single dose
  2. OR + Doxycycline (for C. trachomatis)– 7 days
  3. Penicillin resistance – two types
    • Decreased affinity for penicillin of penicillin-binding proteins – low level
    • Plasmid-mediated TEM-type β-lactamase (PPNG) – high level

no oral antibiotics are affective

27
Q

Haemophilus influenzae Morphology and Staining

A

Gram-negative coccobacilli

Short - 0.5 - 1.5 um
Nonmotile, non-sporeforming
grow on chocolate agar

28
Q

Haemophilus influenzae Classification (3 types)

A
  1. Serotypes: a-f by polysaccharide capsule
  2. Biotypes: using three biochemical reactions
    - For epidemiological studies only
  3. Biogroups
    - H. influenzae biogroup aegyptius causes Brazilian purpuric fever
29
Q

Haemophilus influenzae: Antigenic Structure (virulence factors)

A

•Polysaccharide capsule– 6 types: a - f

  • Type b - polyribitol phosphate
  • Antibody protective (antiphagocytic)
  • Pili
  • Endotoxin
30
Q

how is Haemophilus influenzae transmitted

A

respiratory droplets

31
Q

how does Haemophilus influenzae cause disease

A

Adhere - Pili, OMPs
Transcytose like Neisseria
Encapsulated strains invade bloodstream
Endotoxin - local and systemic inflammation

32
Q

Haemophilus influenzae type b: Clinical Manifestations

A

Meningitis - children

33
Q

Clinical Manifestations: Nontypable Haemophilus influenzae

A

Clinical Manifestations: Nontypable Haemophilus influenzae

34
Q

Haemophilus influenzae
 requires what growth factors

A 
X factor  (Hematin)
V factor  (NAD)
Both supplied by lysed but not whole blood

35
Q

treatment of sever disease caused by Haemophilus influenzae

A

Broad spectrum cephalosporins (2nd and 3rd)

36
Q

treatment of less sever disease (sinusitis, otitis) caused by Haemophilus influenzae

A

Amoxicillin/clavulanate
Trimethoprim-sulfamethoxazole
Fluoroquinolones

25 - 50% produce beta-lactamase
Ampicillin resistant

37
Q

Prevention: Haemophilus influenzae

A 
Vaccine:
PRP-protein conjugate vaccines (type b)
(T-cell dependent antigens)
Universal vaccination of children
Age 2 months

Chemoprophylaxis household contacts
Rifampin

38
Q

Bordetella pertussis: Morphology/Staining

A

Gram-negative coccobacilli

0.5-1.0 um

no capsule
adhesions

39
Q

Bordetella pertussis toxins

A

Pertussis toxin (PT) - (definitely virulent)
Adenylate cyclase toxin
Tracheal cytotoxin - peptidoglycan fragment
Dermonecrotic toxin
Endotoxin - LPS

40
Q

Bordetella pertussis: Adhesins

A

•Pertactin – Surface protein

•Filamentous hemagglutinin (Fha)
- Both bind to integrins on membranes of ciliated respiratory cells
- Both bind to CR3 – glycoprotein on macrophages that promotes phagocytosis without respiratory burst
Promotes intracellular survival

• Pertussis toxin

  • S2 (binding) subunit binds to glycolipid on ciliated cells
  • S3 binds to receptors on phagocytic cells → expression of CR3 on surface

•Pili

41
Q

Pertussis Toxin - PT

A

AB subunit: A-S1 enzymatic, B-S2-S5 binding

A - ADP-ribosylation of regulatory G protein
Prevents inactivation of adenylate cyclase
Biologic effects: increased respiratory secretions and mucus production; lymphocytosis

B – Subunits – previously discussed adhesions

the only toxin we know is definitely virulent

42
Q

Adenylate Cyclase Toxin

A

found in Bordetella pertussis

Increase cAMP levels in cells


Affects leukocyte functions

  • Chemotaxis
  • Superoxide production
43
Q

Tracheal cytotoxin

A

peptidoglycan fragment
Causes extrusion of ciliated tracheal epithelial cells
Stimulates IL-1 release (fever)

found in Bordetella pertussis, damages the cilia of the trachea

44
Q

Dermonecrotic toxin

A

Causes ischemic necrosis

found in bordetella pertussis

45
Q

how is Bordetella purtussis spread

A

Highly infectious airborne droplets

Unrecognized in adults - Reservoir

Decreased immunization - Increased incidence

used to mainly cause infections in young children but has recently shifted towards adolescences

46
Q

Bordetella pertussis: Pathogenesis

A
  • Attach to ciliated cells by adhesins
  • Tracheal cytotoxin and others destroy ciliated cells
  • PT - Systemic manifestations, mucus production, cough, lymphocytosis
  • B. pertussis does not invade respiratory tract cells
47
Q

phases of Bordetella pertusssis infection

A

Incubation: 7-10days no symptoms

catarrhal: 1-2 wks, rhinorrhea, malaise, fever, sneezing
paroxysmal: 2-4 wks, cough, vomiting, leukocytosis

Convalescent: 3-4 wks diminished cough, secondary complications ( pneumonia, seizures, encephalopathy)

48
Q

Bordetella pertussis: Laboratory Diagnosis

A 
Lymphocytosis
Sample - nasopharyngeal aspirate
Charcoal blood agar
  - Strict aerobe, non-motile
  - Difficult  and slow to grow
  - Early - higher yield
Antigen detection - direct immunofluorescence
*PCR – performed in LUMC lab and state laboratories (mostly use PCR now)
49
Q

Bordetella pertussis: Treatment

A

Azithromycin (other macrolides) - may be effective in early disease

Alternate – Trimethoprim/sulfamethoxazole

  • Effective in catarrhal stage only
  • Eliminates nasopharyngeal organisms and prevents spread

Supportive care

50
Q

Bordetella pertussis: Prevention

A

DTaP Vaccines

  • Purified, detoxified PT, Fha, Pn and Fim types 2 and 3
  • Recommended for all children

Replace killed whole cell vaccines

Tdap recommended for all adults
- Takes place of one routine (every 10 years) Td

MHD #3 (11 decks)

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