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2.2 Microbiology > Celine - Neisseria > Flashcards

Celine - Neisseria Flashcards

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1
Q

What type of bacteria are Neisseria and Moraxella

A

Gram Negative Cocci

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2
Q

Write about the genus Neisseria
(2)

A

11 species known to colonise humans

Most are normal flora of nasopharynx

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3
Q

What are the 2 only species of Neisseria of clinical significance

A

N. gonorrhoeae
N. meningitidis

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4
Q

What are the 4 species of Neisseria which exist as normal flora commensals

A

N. lactamica
N. sicca
N. flavescens
N. elongata

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5
Q

What kind of infections does Neisseria gonorrhoeae cause?
(4)

A

Infections have high prevalence and low mortality
Unlike other Neisseria species these are not part of normal flora
Transmission by sexual contact - its a STI
Can cause acute pyogenic infection of the epithelium of various mucosal surfaces

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6
Q

What are the three types of Neisseria gonorrhoeae infections

A

Asymptomatic
Symptomatic uncomplicated
Symptomatic complicated infections

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7
Q

What is an asymptomatic N. gonorrhoeae infection?

A

Reservoir for transmission

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8
Q

What is a symptomatic uncomplicated N. gonorrhoeae infection?

A

Restricted to mucosal sites

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9
Q

What is symptomatic complicated N. gonorrhoeae infections?

A

Invasive and disseminated infection - rare

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10
Q

Why are STIs so important

A

Most common group of identifiable infectious diseases in many countries especially among the ages of 15-50

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11
Q

What are the four most common STI

A

Trichomoniasis
Chlamydia
Gonorrhoea
Syphilis

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12
Q

Comment on the stats of STIs

A

The incidence of STIs has continued to rise

Genital Warts HPV has decreased

Chlamydia has been on the increase

Gonorrhoea on the rise but startig to plateaux

Herpes simplex virus was on the rise but starting to plateua

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13
Q

Comment on the stats for Gonorrhoea

A

Second most common STI in Ireland
Increased by 2.3% in 2021
90% of notifications are male
5:1 male:female ratio
78% are gbMSM -> often in nonurethral sites
Target health promotion and screening in MSM

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14
Q

What were the 2021 stats for covid?

A

N. gonorrhoeae increased by 2.3%

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15
Q

Comment on the importance of N. Gonorrhoeae lab investigation

A

STI in gbMSM

Often found in nonurethral sites

Gonorrhoea undiagnosed if only looking at urethral screening

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16
Q

Comment on N. Gonorrhoea infections in males
(5)

A

Primary site of infections include urethra, pharyngeal and rectal

55-100% are asymptomatic

45% are symptomatic

Causes acute urethritis with yellow purulent discharge and dysuria (pain on micturition), 1-14 days after infection-easy to diagnose

Anorectal and oropharyngeal in gbMSM

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17
Q

What are the complications of N. gonorrhoea infections in males?

A

Prostatitis and epididymitis occur if untreated

Gonococcaemia and joint disease - very rare

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18
Q

Comment on N. Gonorrhoea in females
(4)

A

Primary site of infection is the cervix but also anorectal

90% are asymptomatic and remain undiagnosed reservoir for infection

Symptomatic infection not common

Cervix primary site -> vaginal discharge, burning and frequency and menstrual abnormalities, fever and pain

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19
Q

What are the complications of N. gonorrhoea?
(3)

A

20% of cases extend to uterus leading to pelvic inflammatory disease (PID) - infertility or ectopic pregnancies

Gonococcaemia and joint disease may occur - rare

Transmit to infants - ophthalmia neonatorum - infected conjunctiva

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20
Q

What are the virulence factors of N. gonorrhoeae?
(7)

A

Pili
Opa protein
Iron binding proteins
IgA protease
Por protein
Lipooligosaccharide
No capsule

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21
Q

How do the pili act as virulence factors in N. gonorrhoeae?

A

They adhere to nonciliated mucosal epithelium
Antigenic variation - immune evasion

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22
Q

What does the Opa protein do?

A

Assist in epithelium binding
Assist in antigenic variation and allow for immune evasion

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23
Q

What does iron binding protein do?

A

Facilitates multiplication and colonisation

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24
Q

What does IgA protease do?

A

This cleaves IgA1

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25
Q

What does Por protein do?

A

Invasin

Forms pores

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26
Q

What does Lipooligosaccharide do?

A

LOS is an endotoxin which causes tissue damage

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27
Q

What virulence factor does N. gonorrhoeae not have?

A

No capsule

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28
Q

Write about N. meningitidis
(6)

A

Infections have low prevalence and high mortality

Normal flora in 10-15% of people - colonise the posterior nasopharynx carriers

Carriers can transmit disease to non-immune hosts

Transmission by respiratory droplets - aerosols

Close and prolonged contact - nurseries, schools, kissing, sneezing

Infection may be random or outbreaks

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29
Q

What kind of people does N. meningitidis infect?
(2)

A

Hosts that are lacking antibodies (to capsule)

Deficient in complement components (C5-C8)

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30
Q

What kind of infections does N. Meningitidis cause
(6)

A

BSI
Meningitis
Meningococcemia
Invasive meningococcal disease (IMD) 2 presentations
Acute meningitis
Meningococcemia

31
Q

Comment on the BSI caused by N. meningitidis

A

Following aspiration bacteria attach to epithelial cells of the nasopharyngeal mucosa, cross mucosal barrier, enter the bloodstream

Invasive infection

32
Q

How does N. Meningitidis cause meningitis?
(3)

A

Bacteria enters the CNS causing meningitis

May cause invasive meningococcal disease

High mortality

33
Q

What happens when N. meningitis enters the BS other than a BSI
(3)

A

5-20% enter BS without meningitis-meningococcaemia

Associated with invasive fulminant infection

More damaging and dangerous condition

34
Q

What is IMD

A

Invasive meningococcal disease

35
Q

What is the characteristic sign of meningococcemia

A

Haemorrhagic lesions

36
Q

What is Meningitis?
(4)

A

Causes fever, headache, stiff neck and petechial rash (75% septic cases)

Even when disease diagnosed early and treatment started

5-15% of patients die within 24-48 hours of onset

Brain damage, hearing loss or learning disability in 10-15% of survivors

37
Q

What is meningococcemia?
(4)

A

Causes fever, purpuric lesion, multi-system involvement

Disseminated Intravascular Coagulation

Haemorrhaging and destruction of adrenals - Waterhouse-Friderichsen syndrome

50% of untreated patients die

38
Q

What is a tell tale sign of meningitis

A

Meningococcal rash

39
Q

What is a tell tale sign of meningococcemia?

A

Purpuric skin lesions

40
Q

Comment on the incidence of N. meningitidis
(5)

A

Most common form of bacterial meningitis in Ireland

Incidence highest in babies and young adolescents

50% of cases in first year of life

All invasive meningococcal disease caused by N. meningitidis serogroups A, B, C, Y, W

Serogroup B most common

41
Q

What vaccines are there for meningitis and when were they introduced?
(2)

A

In 2000 the MenC vaccine was introduced

In 2016 the MenB conjugate vaccine was introduced

42
Q

Comment on the stats behind invasive meningococcal disease in Ireland
(5)

A

Marked downward trend in IMD with the intro of MenC

Small increase in 2012

2015 MenC booster introduced

MenB introduced in 2016

Increase of other groups such as W and Y now

43
Q

What are the six virulence factors of N. meningitidis

A

Fimbriae
Capsule
Iron acquisition
Porin
sIgA protease
Lipooligosaccharide

44
Q

What do fimbriae do?

A

Attach to nonciliated epithelial cells
Antigenic switching - allows for immune evasion

45
Q

What does the capsule do for N. meningitidis

A

Prominent antiphagocytic polysaccharide
Immune evasion

46
Q

What is iron acquisition for

A

Multiplication

47
Q

What are porins for

A

Tissue invasion

48
Q

What is sIgA protease for

A

Weaken mucosal immunity

49
Q

What is LOS

A

Lipooligosaccharide
Endotoxin
Major toxin
Tissue damage

50
Q

What clinical specimens are common in N. gonorrhoeae

A

Genital - urethral exudates, cervical swab
Extra-genital e.g. rectal swabs, pharyngeal swabs
Joint fluid - occasionally

51
Q

What clinical specimens is N. meningitidis common in

A

Invasive infection - CSF, blood culture, skin scrapings

Carriage - nasopharyngeal swab

52
Q

Comment on the transport of Neisseria to the lab
(4)

A

Neisseria is fastidious

It is sensitive to drying and temperature variation

Need to use transport media for survival

Transport to lab without delay

53
Q

What is done with N. gonorrhoeae on day 1
(5)

A

Direct specimen microscopy

Isolation

54
Q

Write about the direct specimen - microscopy of N. gonorrhoea

A

Gram stain smear of urethral discharge

Gram-negative kidney-bean intracellular diplococci in pus cells

90% sensitivity and specificity for symptomatic male

30% sensitivity for women and asymptomatic male

55
Q

How does N. gonorrhoeae appear in direct specimen microscopy

A

Gram-negative kidney-bean intracellular diplococci

56
Q

What is done with N. meningitidis on day 1
(5)

A

Direct specimen microscopy

White cell count

Biochemical markers

Direct specimen - antigen detection

Isolation

57
Q

Write about the direct specimen microscopy of N. meningitidis

A

Gram stain on CSF or skin scrapings

Gram negative kidney bean intracellular diplococci in polymorphonuclear leukocytes

58
Q

How does N. meningitidis appear on direct microscopy gram stain

A

Gram negative kidney bean intracellular diplococci in polymorphonuclear leukocytes

59
Q

Write about using a white cell count to identify N. meningitidis

A

Count the number of white and red cells in CSF

White cell differential count -> polymorphs (bacterial) vs mononuclear (viral/TB)

60
Q

Write about using biochemical markers in day 1 ID of N. meningitidis

A

Increase in protein
Decrease in glucose

61
Q

Write about the direct specimen antigen detection on day 1 for N. meningitidis
(6)

A

Rapid identification of serious invasive infection

Direct latex agglutination for N. meningitidis

Latex beads coated with antisera for gpB, C, Y and W

Detect group antigen direct in CSF

Rapid, sensitive and specific

Result available before on Day 1 before culture

62
Q

In direct latex agglutination for N. Meningitidis what are the beads coated with

A

Antisera for gpB, C, Y and W

63
Q

Write about growth characteristics
(2)

A

Pathogenic species fastidious, require blood or serum as well as growth factors (iron, haemin) to grow

They are capnophilic they only grow in 5-10% CO2, 37 degrees, 24-48 hour

64
Q

What is Neisseria put up on on day 1?

A

Blood agar and chocolate agar, chocolate broth

65
Q

What is Neisseria gonorrhoeae put up on on day 1?
(4)

A

Its more fastidious so it requires enriched agar but also contaminated mucosal sites - enriched selective media (add antibiotic cocktail for selectivity)

Thayer-Martin medium
New York City medium

You should warm plates before inoculating

66
Q

What is GC (New York City)?

A

GC is enriched by lysed blood and yeast extract and antibiotics

For isolation of N. gonorrhoeae

67
Q

How should you incubate your Neisseria agar

A

Incubate all at 5-10% CO2, 37 degrees Celsius, 24-48 hours

68
Q

What are the basic characteristics of Neisseria?
(3)

A

Gram-negative kidney bean diplococci

Oxidase positive

Catalase positive

69
Q

How do you remember the basic characteristics

A

GONOCC

Gram negative diplococci, kidney bean shaped
Obligate aerobes
Nonmotile
Oxidase positive
Catalase positive
Capnophilic - prefer increased level of CO2 (5-10%)

70
Q

What testing is done on day 2 for Neisseria

A

Biochemical ID tests (TAXO sugars)

Automation

71
Q

Write about the biochemical ID/ TAXO sugars test for Neisseria

A

Carbohydrate utilisation tests - discriminatory test
Neisseria use carbohydrates oxidatively - not fermentation tests
Test ability to oxidise glucose, maltose, lactose and sucrose
Media e.g. Choc or GC agar minus antibiotics
Lawn inoculum and apply Taxo sugar discs
Incubate overnight in 5-10% CO2
Add phenol red indicator - yellow = positive oxidation reaction

72
Q

Write about the automated confirmatory tests for Neisseria
(2)

A

Maldi-TOF-mass spectroscopy - ID bacteria based on protein profile

Vitek-NH-biochemical profile

73
Q

Write about Neisseria meningitis confirmation using molecular detection
(3)

A

N. meningitis - CSF sent to Irish Meningitis and Sepsis Reference Lab in Temple Street Hospital

Confirm by PCR - performed in addition to culture diagnostic lab

50% of meningitis cause in Ireland confirmed by PCR along-culture negative due to immediate antibiotic treatment

74
Q

Write about Neisseria gonorrhoeae confirmation using molecular detection
(3)

A

Commercial PCR tests for combined detection of N. gonorrhoeae and Chlamydia

Detect detection in clinical specimen performed on Day 1 - gold standard test method - no conventional culture

MDR N. gonorrhoeae emerging - representative culture and antimicrobial susceptibility testing required

2.2 Microbiology (60 decks)

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