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4.1 Medical Microbiology > Acute URTIs - Nasopharyngitis and Pharyngitis > Flashcards

Acute URTIs - Nasopharyngitis and Pharyngitis Flashcards

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1
Q

What is an upper respiratory infection

A

An infection located in the upper respiratory tract:
- mouth, nose, throat, larynx and trachea

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2
Q

What are the seven types of upper respiratory infections

A

nasopharyngitis
Sinusitis
Pharyngitis/tonsilitis
Laryngitis
Laryngatracheitis
Epiglottitis
Otitis Media

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3
Q

What are the four functions of the URT?

A

Breathing
Immunity
Digestion
Speech

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4
Q

Talk about the breathing functino of the URT

A

The URT is a natural air “filter” -> mucuos lining, nasal hairs, cilia etc

The URT moistens, warms and cleanses the air we breath in

URT delivers air to the lungs

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5
Q

Talk about the immune function of the URT

A

The pharynx houses lymphatic tissues that guard against infection by releasing T and B lymphocytes

alveolar macrophages found deeper down in lungs as well

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6
Q

What is the dgestion function of the URT?

A

Epiglottis and larynx work in tandem to prevent food or liquid entering the lungs

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7
Q

What is the speech function of the URT

A

The movement of air across the larynx cerates vibrations

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8
Q

List some of the protective mechanisms of the URT

A

Nasal hairs
Mucus lining
Convoluted passages
Cilia in trachea
Reflexes such as cough, sneeze, swallow
sIgA (IgA in secretions) and T lymphocytes
Antibacterial substances such as lysozyme and interferons
Alveolar macrophages
Normal microflora to compete for nutrients and space
Bacteriocidins

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9
Q

List some of the protective mechanisms of the URT

A

Nasal hairs
Mucus lining
Convoluted passages
Cilia in trachea
Reflexes such as cough, sneeze, swallow
sIgA (IgA in secretions) and T lymphocytes
Antibacterial substances such as lysozyme and interferons
Alveolar macrophages
Normal microflora to compete for nutrients and space
Bacteriocidins

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10
Q

List some of the naturally occuring flora of the nasal cavity
Compare this to in a RTI

A

Staphylococcus
Moraxella
Corynebacteria
Propionibacteria

In RTI: Viral pathogens present

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11
Q

What are some of the naturally occuring flora of the nasopharynx

A

Staphylococcus
Moraxella
Haemophilus
Streptococcus spp
Corynebacterium
Dolosigranulum
Rhinovirus

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12
Q

What is the makeup of the organisms found in the nasopharynx during a RTI

A

Much less diversity during infection
Haemophilus
Streptococcus
Neisseria
Oral-type anaerobes
Respiratory viruses such as RSV or influenzavirus

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13
Q

What are some natural flora of the oropharynx

A

Streptococcus
Neissera
Haemophilus sp
Prevotella

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14
Q

What are some natural flora of the oropharynx

A

Streptococcus
Neissera
Haemophilus sp
Prevotella

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15
Q

Who would you be most likely to finf S. pneumo as a commensal in?

A

Some young kids have S. pneumo in their nasal passage

These arent pathogenic and will only cause infection under the right conditions

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16
Q

Write a note on the epidemiology of URI

A

Account for half of all symptomatic diseases

The most common acute illness evaluated in the outpatient setting (GPs)

Children have been 6-8 episodes per year but can be 12+ etc etc

Adults have between 3-6 episodes per year

Used to be most common in September and March but since covid theyve become a year round infection

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17
Q

Whos most likely to get URIs?

A

Young children or those around them e.g. parents, child-carers or grandparents

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18
Q

Whos most likely to get URIs?

A

Young children or those around them e.g. parents, child-carers or grandparents

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19
Q

What are the three methods of transmission of URIs

A

Droplet transmission

Airborne Transmission

Contact transmission

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20
Q

How are URI transmissed through droplets?

A

Droplets are >5 microns in size

Coughing, sneezing, talking

Contact with mucous membranes

Travel 1-2 meters

Land on surfaces -> another person then touches the surface and picks up the organism

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21
Q

How are URIs transmissed through the air?

A

Aerosol generating procedures
Small in size
Remain airborne for longer then droplets
- aerosols inhaled into lungs of another person

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22
Q

How are URI spread through contact

A

Direct contact -> poor hand hygiene after touching an infected person

Indirect -> touching an object contaminated with droplets etc

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23
Q

What are the main risk factors of URI?

A

Close contact with children
Medical conditions
Smoking
Immunocompromised
Anatomical anomalies
Use of public transport

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24
Q

What medical conditions put you at higher risk of URI?

A

asthma
Allergic rhinitis (hayfever)

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25
Q

What medical conditions put you at higher risk of URI?

A

asthma
Allergic rhinitis (hayfever)

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26
Q

What immune conditions increase risk of URI?

A

Cystic fibrosis
COPD
HIV
Corticosteroids
Transplantation
Post-splenectomy

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27
Q

Give some examples of anatomical anomalies which increase risk of URI

A

Facial dysmorphic changes

Nasal polyposis

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28
Q

What are the two main acute URTIs?

A

Nasopharyngitis
Pharyngitis

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29
Q

What headings should you give when writing about a specific URTI?

A

The infection
Aetiology
Epidemiology
Sequela
Laboratory Detection
Treatment

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30
Q

Talk about nasopharyngitis, what is it and what are the symptoms

A

Known as the ‘common cold’ or a ‘head-cold’

Inflammation of the ciliated epithelial cells in nasal mucosa

A short, mild, self-limiting infection characterised by nasal discharge, cough and a sore throat

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31
Q

Write a note on the aetiology of nasopharyngitis
(3)

A

> 85% caused by respiratory viruses

Between 10 and 15% are less commonly caused by bacteria

<1% of cases caused by rare viruses

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32
Q

What respiratory viruses cause >85% of nasopharyngitis?
(8)

A

1 of 200 virus strains from 7 main families:
Rhinovirus (30-50%)
Parainfluenza
Respiratory syncytial virus
Coronaviruses
Enterovirus
Influenza virus
Adenovirus

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33
Q

What bacteria cause 10-15% of nasopharyngitis?

A

Chlamydia pneumoniae
Mycoplasma pneumoniae
Streptococcus pyogenes

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34
Q

What rare viruses cause <1% of nasopharyngitis?

A

Mumps virus
Rubella virus
Rubeola virus
Cytomegalovirus

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35
Q

What rare viruses cause <1% of nasopharyngitis?

A

Mumps virus
Rubella virus
Rubeola virus
Cytomegalovirus

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36
Q

Why is nasopharyngitis caused by viruses such as mumps and rubella now rare to see

A

Nearly everyone should be vaccinated against these (MMR vaccine)

We did have a drop of in people getting vaccinated but this has gone back up again

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37
Q

What are the five most common sequelae from nasopharyngitis?

A

Lower respiratory tract infection - most common
Bronchial hyperreactivity/asthma flare
Otitis media (5-19%) - more common in kids
Acute sinusitis
Pneumonia
Eye infections in kids

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38
Q

How does nasopharyngitis become eye infections in young kids but is rarely seen in adults?

A

Thinkof how a young kid wipes their nose
Snot straight into the eye

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39
Q

How does nasopharyngitis become eye infections in young kids but is rarely seen in adults?

A

Thinkof how a young kid wipes their nose
Snot straight into the eye

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40
Q

Talk about the diagnosis of nasopharyngitis

A

Nearly always a clinical diagnosis or a symptomatic diagnosis by the patient themselves

Rarely ever get a sample for investigation

Can run biofire film array respiratory panel to detect viruses -> but realistically this is only really done to investigate something else and the virus comes up then accidentally

There is also Rare rtPCR and ELIZA testing available but this isnt really done anywhere

41
Q

Talk about the diagnosis of nasopharyngitis

A

Nearly always a clinical diagnosis or a symptomatic diagnosis by the patient themselves

Rarely ever get a sample for investigation

Can run biofire film array respiratory panel to detect viruses -> but realistically this is only really done to investigate something else and the virus comes up then accidentally

There is also Rare rtPCR and ELIZA testing available but this isnt really done anywhere

42
Q

How is nasopharyngitis treated?

A

Symptomatic therapy

Rest, fluid, paracetemol only really treatment

43
Q

What is pharyngitis?

A

Infection of the pharynx or tonsils

Associated with pharyngeal pain and the appearance of erythema and swelling of affected tissues (tonsils)

Sore throat - swollen lump on each side of throat

44
Q

Comment on the aetiology of pharyngitis

A

70% of cases are viral
30% are bacteral
Very rare cases are fungal

45
Q

Comment on the epidemiology of pharyngitis

A

One of the most common conditions encountered by GP

16% of adults ad 41% of children report a sore throat over a 1 year time frame

Incidence peaks between late winter and early spring

46
Q

What viruses cause pharyngitis

A

Rhinovirus
Adenoviruses (pharyngoconunctival fever)
Coxsackie A and other enteroviruses (small vesicles - herpangia)
EBV in 70-90% of glandular fever patients
Herpes simplex 1 and 2 -> can be severe with palatal vesicles or ulcers

47
Q

What is the telltale sign of adenovirus caused pharyngitis

A

Pharyngoconjunctival fever

48
Q

What is the telltale sign of adenovirus caused pharyngitis

A

Pharyngoconjunctival fever

49
Q

What is the telltale sign of Coxsackie or enterovirus caused pharyngitis

A

Small vesicles - herpangia

50
Q

What is the telltale sign of Herpes caused pharyngitis?

A

Palatal vesicles or ulcers

51
Q

What is the telltale sign of Herpes caused pharyngitis?

A

Palatal vesicles or ulcers

52
Q

What is the treatment for viral pharyngitis?

A

Usually only symptomatic treament -> fluids, rest etc

53
Q

What is the main cause of bacterial pharyngitis?

A

Group A streptococcus -> S. pyogenes

54
Q

Talk about S. pyogenes pharyngitis, what symptoms does it cause

A

Main bacterial cause of tonsilitis

Tonsillar exudate (white tonsils)

Pyrexia, anorexia and dysphagia

Painful cervical lymphadenopathy

No cough -> just sore throat no other URI symptoms

55
Q

Talk about S. pyogenes pharyngitis, what symptoms does it cause

A

Main bacterial cause of tonsilitis

Tonsillar exudate (white tonsils)

Pyrexia, anorexia and dysphagia

Painful cervical lymphadenopathy

No cough -> just sore throat no other URI symptoms

56
Q

What are the risk facors for S. pyogenes pharyngitis?

A

Young age -> strep throat most common in children

Time of yeaar -> circulates in winter and early spring

Strep bacteria flourish where groups of people are in close contact

57
Q

Comment on the aetiology of S. pyogenes pharyngitis

A

Causes of 700 million cases Worldwide per year - a significant amount of cases

Isolated in up to 5-15% of adult and 15-30% of children

58
Q

List the sequela of S. pyogenes pharyngitis

A

Quinsy
Otitis media nad sinusitis
Pneumonia
Bacteraemia
Meningitis
Necrotising fasciitis

Scarlet fever
Rheumatic fever
Endocarditis
Glomerulonephritis

59
Q

What is Quinsy?

A

A peritonsillar abscess

A sequelae of acute bacterial tonsilitis caused by S. pyogenes

60
Q

What is necrotising fasciitis?

A

Death of fibrous tissue beneath the skin and around muscle

61
Q

Why do doctors tend to overprescribe antibiotics for pharyngitis without taking a throat swab?

A

GPs check for white on tonsils
If white presence they give antibiotics even though this could still be a viral infection
Fear of S. pyogenes which can cause severe sequelae if missed

62
Q

What causes S. pyogenes scarlet fever?

A

The effects of pyrogenic(erythrogenic) toxin

63
Q

What is Rheumatic fever

A

An autoimmune reaction due to S. pyogenes

A sequela damaging the heart (arthtitis)

Molecular mimicry whereby antibodies produced against S.pyogenes M-protein damage the human proteins (myosin) of the heart

The build up of antibodies is what causes arthritis symptoms

The autoimmune on cardiac cells causes inflammation known as endocarditis

64
Q

What molecules are involved in molecular mimicry of S. pyogenes caused endocarditis?

A

S. pyogenes M-protein and cardiac cell myosin

65
Q

Talk about S. pyogenes caused glomerulonephritis

A

PSGN or poststreptococcal glomerulonephritis results from a bacterial infection that causes rapid deterioration of kidney function due to an inflammatory response following infection

Basically the infection causes glomeruli to become inflammed

66
Q

Talk about S. pyogenes caused glomerulonephritis

A

PSGN or poststreptococcal glomerulonephritis results from a bacterial infection that causes rapid deterioration of kidney function due to an inflammatory response following infection

Basically the infection causes glomeruli to become inflammed

Antigen -> antibody produced -> Ag-Ab complex -> large complex -> glomeruli damaged

67
Q

How does S pyogenes toxic shock come about?

A

S. pyogenes superantigen toxin is responsible

This is recognised by T lymphocytes which release cytokines responsible for TSS symptoms

68
Q

What three infections can occur from the metastatic spread of an S.pyogenes bacteraemia?

A

It can cross the blood-brain barrier and cause meningitis
It can cause arthritis
It can cause osteomyelitis

69
Q

What three infections can occur from the metastatic spread of an S.pyogenes bacteraemia?

A

It can cross the blood-brain barrier and cause meningitis
It can cause arthritis
It can cause osteomyelitis

70
Q

Talk about group C/G streptococcal pharyngitis

A

S. dysgalactie is the most common

Causes about 3-5% of pharyngitis

Similar in clinical features to GAS but sequelae not as severe

genetically very similar to GAS -> prior to MALDI they were hard to distinguish from each other

71
Q

Talk about group C/G streptococcal pharyngitis

A

S. dysgalactie is the most common

Causes about 3-5% of pharyngitis

Similar in clinical features to GAS but sequelae not as severe

genetically very similar to GAS -> prior to MALDI they were hard to distinguish from each other

72
Q

If you had a persistant sore throat what bacterial cause of pharyngitis would you be concerned with?

A

Fusobacterium necrophorum

73
Q

Talk about the aetiology of F. necrophorum pharyngitis

A

Most likely cause of PSTS - persistant sore throat syndrome i.e. bacterial pharyngitis that re-occurs after treatment

Obligate anaerobe GNB

Quiet difficult to diagnose

Main complication is Lemierre’s Syndrome

74
Q

What is the main complication of F. necrophorum pharyngitis?

A

Lemierre’s Syndrome

75
Q

What is Lemierre’s Syndrome?

A

Where Fusobacterium spreads to a major blood vessel and causes blood clots in the bloodstream

76
Q

Talk about Corynebacterium pharyngitis

A

C. diptheria most common
Acute onset
Characteristic pseudomembraneous tonsils and back of throat
Not really a problem in ireland due to immunisation with toxoid vaccine but still sen due to foreign travel and immigration

77
Q

Talk about C. diptheria complications

A

Bacteria release diptheria toxins A/B which can cause damage to myocardium, nerve endings and adrenal glands

Grey adherent leathery pseudomembrane can block airways or can lodge in trachea/bronchi

Death due to myocarditis and neurological complications

Tracheostomy needed

78
Q

Comment on epidemiology of C. diptheria pharyngitis

A

Very few cases since introduction of toxoid vaccine e.g. 0 cases in Ireland in 2019

16,000 cases worldwide in 2018 -> in unvaccinated and immunocompromised

79
Q

Comment on epidemiology of C. diptheria pharyngitis

A

Very few cases since introduction of toxoid vaccine e.g. 0 cases in Ireland in 2019

16,000 cases worldwide in 2018 -> in unvaccinated and immunocompromised

80
Q

What are the symptoms of C.diptheria pharyngitis

A

Sore throat
Bull Neck
Grey pseudomembrane

81
Q

What are the 4 main sequelae of C. diptheria pharyngitis?

A

Damage to the heart muscle (myocarditis)
Damage to the renal tubules (acute tubular necrosis)
Nerve damage (nerve demyelination/polyneuropathy)
Loss of the ability to move (paralysis)

82
Q

Write a note on lab detection of bacterial pharyngitis

A

Throat swab = gold standard
97% specific and 95% sensitive on blood agar
Containment level 2 lab

83
Q

How should throat swabs be put up for pharyngitis investigation?

A

Blood agar incubated overnight anaerobically
For query fuso a blood agar + metronidazol will be put up with extended incubation (48hrs)

84
Q

How should throat swabs be put up for pharyngitis investigation?

A
85
Q

What make you query a Corynebacterium pharyngitis?

A

Foreign travel

86
Q

What three media would be suitable for confirmation of Corynebacterium?

A

Tinsdale
Tellurite
Hoyles

87
Q

How would you confirm ID of a Group A Strep
(6)

A

Gram + cocci in long chains
Beta haemolytic on blood agar
Bacitracin sensitive
Lancefield group A
Penicillin Sensitive
PYR Test

88
Q

Why do we incubate throat swabs anaerobically?

A

The streptolysins of strep demonstrate B haemolysis better when incubated anaerobically even though strep will still grow in CO2

89
Q

Why do we incubate throat swabs anaerobically?

A

The streptolysins of strep demonstrate B haemolysis better when incubated anaerobically even though strep will still grow in CO2

90
Q

What is the PYR Test?

A

Pyrrolidanyl Aminopeptidase Test

91
Q

How would you confirm ID of Fusobacterium necrophorum?

A

Gram negative pleomorphic bacilli - all different sizes
Strict anaerobes -> hence Mtz disc
Non-motile
Non-spore forming
Beta haemolytic on BA
Selective agars including vancomycin and nalidixin
Characteristic odour (rancid butter or boiled cabbage) and flecked appearance

92
Q

How would you confirm ID of a Corynebacterium Diptheria?

A

GPB
Clubman shape
Chinese lettering
Aerobic or facultative anaerobe
Tellurite
Hoyles
Tinsdale
ELEK Plate for toxin investigation

93
Q

How does Corynebacterium grow on Tinsdale

A

Black colonies surrounded by brown halos -> due to production of cysteinase which release H2S which interacts with salt in media

94
Q

How will C. diptheria grow on Hoyle’s?

A

C. diptheria mitis = black colonies with grey periphery

C. diptheria gravis = large, grey colonies

C. diptheria intermedius = small, dull, grey-black colonies

95
Q

How will C. diptheria grow on Hoyle’s?

A

C. diptheria mitis = black colonies with grey periphery

C. diptheria gravis = large, grey colonies

C. diptheria intermedius = small, dull, grey-black colonies

96
Q

What is the ELEK plate for C. diptheria?

A

An immunodiffusion method
involves applying filter paper soaked in anti-toxin to the plate

97
Q

How is group A Strep treated?

A

Penicillin - usually works

Erythromycin

1st gen cephaloporins

Macolides

98
Q

How is Fuso necrophorum treated?

A

B-lactam antibiotics
Metronidazole
Clindamycin
3rd Generation Cephalosporins

99
Q

How is C. diptheria treated?

A

Erythromycin
Antitoxin - given to revent further spread of toxin

4.1 Medical Microbiology (30 decks)

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