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2.2 Microbiology > Celine - Haemophilus > Flashcards

Celine - Haemophilus Flashcards

(50 cards)

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1
Q

What are the three families of small gram negative rods (coccobacilli)?

A

Pasteurellaceae
Alcaligenaceae
Brucellaceae

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2
Q

What are the two genera of pasteurellaceae

A

Haemophilus
Pasteurella

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3
Q

What is the genera in alcaligenaceae

A

Bordetella

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4
Q

What is the genera in brucellaceae

A

Brucella

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5
Q

How are pasteurellaceae classified
(3)

A

Family is classified into nine genera

Most are regarded as commensals

The two genera of interest are Haemophilus and Pasteurella

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6
Q

Write about Haemophilus

A

10 species found in clinical specimens
Most are non-pathogenic

H. influenzae
H. ducreyi
H. aegyptius
H. parainfluenzae (opportunistic)

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7
Q

What are the two types of H. influenzae

A

Type B
Non-typable

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8
Q

What infections does H. influenzae type b cause
(6)

A

Meningitis type B

Epiglottis type B

Bloodstream infection - type B

Cellulitis
Arthritis
Osteomyelitis

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9
Q

What infections does non-typable H. influenzae cause

A

Otitis - non-typable
Sinusitis - non typable
Pneumoniae - non-typable

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10
Q

What infections does H. aegyptius cause

A

Conjunctivitis

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11
Q

What infections does H. parainfluenzae cause

A

Opportunistic infection
Pneumoniae
Endocarditis

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12
Q

What infections does H. ducreyi cause

A

Chanchroid (genitals and lymph nodes)

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13
Q

Write about H. influenzae infection
(3)

A

Range from those associated with local conditions to those that cause invasive disease

2 groups: Invasive and noninvasive

Type of infection depends on Capsule production

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14
Q

Write about invasive infections

A

H. influenzae is the primary pathogen
Acute pyogenic invasive infection
Meningitis, epiglottitis, bloodstream infection

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15
Q

Write about the noninvasive infections

A

H. influenzae play secondary role
Induce inflammatory response
Pneumonia, otitis media and sinusitis

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16
Q

What are the virulence factors of H. influenzae
(5)

A

Capsule
IgA protease
Pili
Endotoxin
Outer membrane proteins

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17
Q

Write about the capsule virulence factor of H. influenzae
(4)

A

Virulence is directly related to capsule formation

Six capsular types - serotypes a -f

Serotype b most virulent -> causes 95% of blood stream and meningeal Haemophilus infections

Noncapsulated strains known as non-typable strains (NTHI) were primarily associated with noninvasive infection

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18
Q

Write about the virulence of Type b strains
(4)

A

Type b strains have a polyribosyl ribitol phosphate (PRP) capsule renders them:

Resistant to phagocytosis by PMN leukocytes

Non-inducers of alternative complement pathway

Hib can invade the blood or CSF without attracting phagocytes or provoking an inflammatory response.

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19
Q

What are the significant virulence factors of Hib

A

PRP Capsule

Fimbriae

IgA protease

Lipooligosaccharide

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20
Q

What are the significant virulence factors of NTHI

A

Fimbriae
IgA protease
Especially active lipooligosaccharide

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21
Q

What is the function of fimbriae

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A

Successful colonisation of the nasopharynx

22
Q

What is the function of IgA protease

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A

Degrades host secretory IgA

23
Q

What is the function of lipooligosaccharide

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A

Inhibits mucocilliary clearance

Antigenic diversity

Immune evasion

24
Q

Write about H. influenzae
(5)

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A

Human host reservoir for infection

H. influenzae present in the nasopharynx of 75% of healthy children and in a lower percentage of adults

Usually NTHI strains harboured as normal flora

But a minority of healthy individuals (3-7%) intermittently harbour Hib

H. influenzae is spread by droplet transmission through secretions and/or aerosols

25
Write about H. influenzae epidemiology in children
Not developed antibody response to PRP capsule Hib most common cause of H. influenzae
26
Write about H. influenzae epidemiology in adults
Acquired antibody to PRP NTHI most common cause of Haemophilus infection NTHI strains have tended to be less invasive, but induce an inflammatory response that cause disease
27
Write about Hib infection
Hib may penetrate the epithelium, evade IR causing invasive infection: - epiglottis - meningitis in children <3 - bloodstream infection - spread to other areas - cellulitis, arthritis and osteomyelitis Less frequently Hib causes: - pneumonia in 15% of Haemophilus infection - otitis media in 5-10% of Haemophilus infection
28
What is epiglottis
Epiglottis inflamed may close off upper airway
29
Write about NTHI infections
Pneumonia Otitis media
30
Write about H. influenzae caused meningitis (5)
Hib used to be the most common cause of meningitis in children between the ages of 6 months and 2 years Accounted for 50-65% of meningitis cases 5% fatality 15-30% of cases caused hearing impairment or neurological sequelae Incidence of Hib invasive disease has declined by 98% since introduction to Hib vaccine
31
Write about the Hib vaccine (5)
Introduced in Ireland 1992 The Hib vaccine offered to all children as part of the routine immunisation programme Hib began to increase in recent years The Hib booster was introduced in 2006 Hib reducing again NTHI invasive infections increased There was only 1 case of Hib invasive infection in 2022
32
Write about NTHI pathogenesis
IgA protease facilitates colonisation of the upper respiratory tract mucosa Infection arises from spread from site of colonisation In babies and young children common cause of middle ear infection - otitis media, which manifests as an earache with fever (90% cases NTHI) In adults may infect mucosa damaged by viral disease or cigarette smoking may lead to pneumonia, (85% cases NTHI) particularly in COAD But in past 10 years, a steady but constant increase has occurred in invasive NTHI worldwide, with elderly most at risk- change in epidemiology Patients with underlying co-morbidities are most susceptible
33
Write about non-invasive H. influenzae infections (5)
Most often non-capsulated NTHI Otitis media Pneumonia But NTHI increasingly implicated in invasive disease - meningitis in elderly
34
Write about invasive H. influenzae infections (7)
Associated with capsulated H. influenzae capsule type B: Hib Meningitis Epiglottitis BSI Arthritis Osteomyelitis Less commonly pneumonia and otitis media
35
What are the clinical specimens of Haemophilus
Cerebrospinal fluid Blood Sputum Middle ear aspirates Nasopharyngeal swabs -> carriage Eye swabs -> H. aegyptius Genital swab -> h. ducreyi
36
Write about the day 1 investigation of Haemophilus (2)
Haemophilus fastidious - very prone to drying and chilling Specimens should be held at room temperature and processed as soon as possble
37
What is done with Haemophilus on day 1
Direct specimen microscopy - gram stain Direct specimen microscopy - CSF white cell count Direct specimen - antigen detection Isolation of Haemophilus
38
Write about the gram stain of haemophilus
Done directly on CSF, blood, sputum or ear swabs Small Gram-negative pleomorphic coccobacilli - very difficult to see especially in small numbers
39
Write about the WCC in direct specimen microscopy of Haemophilus
CSF - count number of white and red cells White cell differential - polymorphs (bacterial) vs mononuclear (viral/TB) Biochemical - increase in protein and decrease in glucose
40
Write about the day 1 direct specimen antigen detection of Haemophilus (5)
Latex agglutination for Hib antigens Latex beads coated with antisera for serotype b Detect antigens direct in CSF Rapid, sensitive and specific Result available before culture
41
What are the growth characteristics of Haemophilus (6)
In vitro growth requires accessory growth factors including Heat stable X factor (haemin) Heat labile V factor (nicotinamide adenine dinucleotide, NAD) Capnophilic Must be cultured on chocolate agar Incubated for 24-48 hours in 5-10% CO2
42
What does capnophilic mean
Only grows in 5-10% CO2 at 37 degrees for 24-48 hours
43
Why does Haemophilus need chocolate agar to grow (4)
Haemophilus needs X and V factors Blood agar contains X factor (haemin) but also NADase which inactivates V factor (NAD) Therefore chocolate agar must be used Chocolate agar is made by heating blood cells to 80 degrees Celsius which releases V factor and destroys NADase
44
Write about day 2 basic characteristics of Haemophilus (7)
No growth on blood agar Growth on chocolate agar 1mm grey wet colonies Pungent odour Gram-negative coccobacilli Oxidase positive Catalase positive
45
What tests are carried out on day 2 Haemophilus identification
X and V growth factor requirement test - discriminatory test Automation: - Maldi TOF - Vitek-NH-biochemical profile Molecular detection
46
Write about X and V factor test
Test organism is lawned onto DST agar (free of X and V) Apply X, V and XV discs on agar Incubate in 5-10% CO2
47
What species needs factor X and V
H. influenzae H. aegyptius
48
What species needs factor V
H. parainfluenzae
49
What species needs factor X only
H. ducreyi
50
Write about the molecular detection of Haemophilus (3)
CSF sent to Irish Meningitis and Sepsis Reference Laboratory, Temple Street Confirm by PCR - performed in addition to culture diagnostic lab 50% of meningitis cases in Ireland confirmed by PCR alone - culture negative

2.2 Microbiology (60 decks)

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