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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
Neisseria gonorrhoeae - Laboratory Diagnosis
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
Treatment of Gonorrhea
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
Haemophilus influenzae Morphology and Staining
Gram-negative coccobacilli
 Short - 0.5 - 1.5 um Nonmotile, non-sporeforming grow on chocolate agar
28
Haemophilus influenzae Classification (3 types)
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
Haemophilus influenzae: Antigenic Structure (virulence factors)
•Polysaccharide capsule-- 6 types: a - f - Type b - polyribitol phosphate - Antibody protective (antiphagocytic) * Pili * Endotoxin
30
how is Haemophilus influenzae transmitted
respiratory droplets
31
how does Haemophilus influenzae cause disease
Adhere - Pili, OMPs Transcytose like Neisseria Encapsulated strains invade bloodstream Endotoxin - local and systemic inflammation
32
Haemophilus influenzae type b: Clinical Manifestations
Meningitis - children
33
Clinical Manifestations: Nontypable Haemophilus influenzae
Clinical Manifestations: Nontypable Haemophilus influenzae
34
Haemophilus influenzae
 requires what growth factors
``` X factor (Hematin) V factor (NAD) Both supplied by lysed but not whole blood
 ```
35
treatment of sever disease caused by Haemophilus influenzae
Broad spectrum cephalosporins (2nd and 3rd)
36
treatment of less sever disease (sinusitis, otitis) caused by Haemophilus influenzae
Amoxicillin/clavulanate Trimethoprim-sulfamethoxazole Fluoroquinolones 25 - 50% produce beta-lactamase Ampicillin resistant
37
Prevention: Haemophilus influenzae
``` Vaccine: PRP-protein conjugate vaccines (type b) (T-cell dependent antigens) Universal vaccination of children Age 2 months ``` Chemoprophylaxis household contacts Rifampin
38
Bordetella pertussis: Morphology/Staining
Gram-negative coccobacilli
 0.5-1.0 um no capsule adhesions
39
Bordetella pertussis toxins
Pertussis toxin (PT) - (definitely virulent) Adenylate cyclase toxin Tracheal cytotoxin - peptidoglycan fragment Dermonecrotic toxin Endotoxin - LPS
40
Bordetella pertussis: Adhesins
•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
Pertussis Toxin - PT
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
Adenylate Cyclase Toxin
found in Bordetella pertussis Increase cAMP levels in cells
 Affects leukocyte functions - Chemotaxis - Superoxide production
43
Tracheal cytotoxin
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
Dermonecrotic toxin
Causes ischemic necrosis found in bordetella pertussis
45
how is Bordetella purtussis spread
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
Bordetella pertussis: Pathogenesis
* 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
phases of Bordetella pertusssis infection
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
Bordetella pertussis: Laboratory Diagnosis
``` 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
Bordetella pertussis: Treatment
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
Bordetella pertussis: Prevention
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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