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The Nervous System & Respiratory Diseases > Respiratory Infections (L26-31) > Flashcards

Respiratory Infections (L26-31) Flashcards

1
Q

Describe Staphylococcus aureus.

A
  • Gram positive cocci in irregular clusters

- Catalase positive

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2
Q

Describe Neisseria meningitidis.

A
  • Gram-negative capsulated diplococcus
  • Only known host is humans and asymptomatic nasopharyngeal carriage occurs
  • Capsule protects against phagocytosis so systemic spread occurs
  • Continuous production of outer membrane fragments releases great quantities of endotoxin leading to shock
  • Overwhelming septicaemia with haemorrhagic rash may occur
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3
Q

Describe Streptococcus pyogenes.

A
  • Gram positive cocci in chains

- Catalase negative

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4
Q

Describe Corynebacterium diptheriae.

A
  • Gram-positive rods forming ‘Chinese letters’ as a result of incomplete division.
  • Also contains metachromatic granules of polyphosphate.
  • Causes diphtheria which is now rare as immunisation is successful, and humans are the only hosts.
  • Virulence is caused by the diptheria exotoxin.
  • Produces a pseudomembrane on the tonsils and pharynx which can spreads upwards or downwards leading to respiratory obstruction and death.
  • The toxin enters the bloodstream causing fever and heart failure.
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5
Q

Describe Haemophilus Influenzae.

A
  • Haemophilus influenzae appears as Gram-negative small coccobacilli (sometimes longer filaments)
  • It was, until recently, the principal cause of meningitis in children between the ages of about 3 months and four years of age
  • It is also the cause of what can be a life-threatening disease, epiglottitis
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6
Q

Describe Coccidiodes immitis.

A
  • Gram negative rods
  • Humans are the only reservoir and source of infection
  • Produces an infection of the epithelium of the large airways, characterised by spasmodic bouts of coughing, often accompanied by vomiting and subconjunctival haemorrhage
  • Produces an endotoxin leading to fever, and a number of exotoxins. It is a disease preventable by vaccination
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7
Q

Describe Streptococcus pneumoniae.

A
  • Gram positive diplococci

- Catalase negative

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8
Q

Describe Mycobacterium tuberculosis.

A
  • Rods not classified by the Gram stain
  • Cells have special cell walls with an outer lipid layer containing waxy components.
  • Infection is by aerosols.
  • No toxins are produced and virulence relies on the cell wall.
  • Damage is initially localised in the lungs but may then spread to other sites in the body.
  • Preventable by immunisation.
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9
Q

Name some upper respiratory infections.

A
  • Common cold
  • Sinusitis
  • Otitis (middle ear)
  • Pharyngitis
  • Epiglottitis
  • Laryngotracheitis- laryngitis and croup
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10
Q

Describe the pathogenesis of upper respiratory infections.

A
  • Organisms gain entry to the respiratory tract by inhalation of droplets, mainly from coughing and sneezing
  • Organisms then invade mucosa
  • Epithelial destruction may ensue, with redness, oedema (swelling), haemorrhage and sometimes an exudate
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11
Q

What are the initial symptoms of a cold?

A
  • Runny, stuffy nose
  • Sneezing
  • Usually no fever
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12
Q

What are the symptoms of epiglottitis?

A
  • Difficulty in breathing
  • Muffled speech
  • Drooling
  • Stridor (noisy breathing or wheezing)
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13
Q

What are the symptoms of laryngotracheitis?

A
  • Rapid breathing

- A bluish colouration of the skin through lack of oxygen

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14
Q

True or false? Common colds usually recognised clinically.

A

True.

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15
Q

How are pharyngitis and laryngotracheitis diagnosed?

A

Bacterial cultures of throat swabs.

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16
Q

How is epiglottitis diagnosed?

A

Blood cultures.

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17
Q

How do you treat viral infections?

And what with?

A

Symptomatically.

  • Decongestants
  • Antipyretics
  • Fluids
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18
Q

How do you treat bacterial pharyngitis and epiglottitis?

A

With antibiotics.

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19
Q

What causes the common cold?

A

A range of viruses. Mainly rhinoviruses.

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20
Q

How long does the common cold last?

A

48-72 hours.

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21
Q

What diseases may occur as a secondary bacterial infection to the common cold.

A
  • Otitis media

- Sinusitis

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22
Q

What is sinusitis?

A

An inflammation of one or more of the sinuses, the hollow cavities within the cheek bones found around the eyes and behind the nose.

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23
Q

What is the primary function of the sinuses?

A

To warm, moisten and filter the air in the nasal cavity.

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24
Q

Acute sinusitis most often follows a _____ _____.

A

Common cold.

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25
Q

Which bacteria most commonly cause acute sinusitis?

A
  • Streptococcus pneumonia
  • Haemophilus influenzae
  • Moraxella catarrhalis
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26
Q

_____ sinusitis is also commonly a mixed infection of aerobic and anaerobic organisms.

A

Chronic.

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27
Q

Describe Moraxella catarrhalis.

A
  • M. catarrhalis is a member of the family Neisseriaceae
  • Gram negative diplococcus
  • Rough, circular, convex colonies on agar
  • Grows well on nutrient agar at 28oC
  • Strictly aerobic
  • Oxidase and catalase +ve
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28
Q

Describe the pathogenesis of sinusitis.

A
  • The sinuses in their normal state are empty since mucous is constantly swept out by cilia.
  • The mucous is swept into the nasal cavity where it then drains out of the nose (runny nose) or into the back of the throat (post nasal drip).
  • When cilia do not properly function because of infection, mucous is not properly cleared.
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29
Q

Which bacteria most commonly cause otitis media?

A
  • Streptococcus pneumonia
  • Haemophilus influenzae
  • Streptococcus pyogenes (group A)
  • Moraxella catarrhalis
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30
Q

What are the symptoms of otitis media?

A
  • Acute ear ache (usually confined to one side)
  • High fever
  • Nausea
  • Vomiting
  • Diarrhoea
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31
Q

How would you go about diagnosing otitis media?

What would you see?

A
  • By looking into the ear canal with an otoscope

- Bulging, reddened tympanic membrane (ear drum)

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32
Q

How do you treat otitis media?

A
  • Analgesics

- Antibiotics

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33
Q

What are Pharyngitis & Tonsillitis?

A

Infections in the throat which cause inflammation of the lymphoid tissue.

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34
Q

What causes Pharyngitis & Tonsillitis?

A

Bacterial, viral or fungal infections.

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35
Q

How do you treat bacterial Pharyngitis & Tonsillitis?

A

Penicillin G.

36
Q

What is acute laryngitis?

A

An infection of the larynx (voice box).

37
Q

What causes laryngitis?

A

Viral and bacterial infections.

38
Q

List the common symptoms of laryngitis.

A
  • Hoarseness or loss of voice
  • Raw throat
  • Dry cough
  • Tickling sensation in the throat
  • Persistent need to clear the throat
39
Q

What does Haemophilus influenzae infect and cause?

A

The upper respiratory tract and causes acute respiratory infections (pneumonia, bronchitis), acute conjunctivitis, otitis media and bacterial meningitis).

40
Q

True or false? A vaccine (Hib vaccine) to stimulate antibodies against the capsule is now available, and has almost eliminated the disease.

A

True.

41
Q

True or false? All species of Haemophilus are catalase and oxidase positive.

A

True.

42
Q

Name the 3 layers of the meninges from superficial to deep.

A
  • The dura mater
  • The arachnoid mater
  • The pia mater
43
Q

Describe the dura mater.

A

The dura mater is the toughest layer next to the inner surface of the skull. They can contain blood filled cavities called dural sinuses which contain venous blood.

44
Q

Describe the arachnoid mater.

A

The arachnoid mater is a fibrocellular layer. Tight junctions between cells form a fluid-tight compartment.

45
Q

Describe the pia mater.

A

The pia mater is a thin layer that closely covers the surface of the brain and spinal cord.

46
Q

What is meningitis?

A

An infection which causes inflammation of the membranes covering the brain and spinal cord.

47
Q

What causes meningitis?

What are the effects of each?

A
  • Viral infections (most common). Usually resolve without treatment
  • Bacterial infections. Cause extremely serious illnesses, and may result in death or neurological damage even if treated. The brain may also become inflamed
48
Q

What is a lumbar puncture a diagnostic test for?

A

Meningitis.

49
Q

What is epiglottitis?

A

An acute infection of the epiglottis.

50
Q

What happens to the epiglottis during epiglottitis?

A

The epiglottis rapidly swells, blocking the passage of air into the lungs. This is potentially fatal and is a medical emergency.

51
Q

What causes epiglottitis?

A

Haemophilus influenzae type B.

52
Q

Which ages are susceptible to epiglottitis?

A

Epiglottitis tends to occur in children aged between 1-6 years, although it may occur at any age.

53
Q

How is epiglottitis treated?

A
  • If the child has a sore throat and difficulty breathing, immediate medical help must be sought
  • It may be necessary to insert a tube into the windpipe under general anaesthetic to keep the airways open
  • Antibiotics should be given intravenously and humidified oxygen is given to help the patient breathe
54
Q

_____ produce clumps of cells, have an oxidative metabolism and are therefore catalase positive.
They are Gram-positive cocci that grow in the presence of air.

A

Staphylococcus.

55
Q

_____ produce chains of cells, are fermentative (produce lactic acid) and are therefore catalase negative. They are Gram-positive cocci that grow in the presence of air.

A

Streptococcus.

56
Q

Staphylococcus are divided into two major groups using the coagulase test.
Name the two groups and the species within each.

A

Coagulase +ve:
- S. aureus

Coagulase -ve:

  • S. epidermidis
  • S. saprophyticus
57
Q

What does coagulase do?

A

Coagulase converts fibrinogen to insoluble fibrin which causes the staphylococci to clump together.

58
Q

Describe the Exfoliative toxins released by Staphylococcus aureus and the effects they cause?

At risk age-groups?

A
  • Two exfoliative toxins are produced, toxin A is chromosomal, toxin B is plasmid borne
  • Produces exfoliative dermatitis known as scalded skin syndrome
  • Epidermis peels off revealing red area underneath
  • Mainly seen in young children and is usually self resolving
59
Q

What are the clinical manifestations of Toxic shock syndrome toxin-1?

A
  • Low blood pressure
  • Fever
  • Diarrhoea
  • Extensive skin rash
  • Shedding of skin
60
Q

How are Staphylococcal diseases treated?

A

With antibiotic therapy.

61
Q

How is scarlet fever spread?

A

By inhalation of infective respiratory droplets.

62
Q

What is Necrotizing fasciitis?

A

A deep-seated infection of subcutaneous tissue that causes destruction of the sheath covering skeletal muscle.

63
Q

What are the clinical manifestations of Necrotizing fasciitis?

Mortality rate?

A
  • Severe pain
  • Severe systemic toxicity
  • Cutaneous gangrene
  • Haemorrhagic fluid leaking from a wound
  • Untreated progresses to multiple organ dysfunction
  • Overall mortality 30%
64
Q

Describe the bacterium Neisseria meningitidis.

A
  • Gram-negative, aerobic encapsulated diplococcus

- Oxidase & catalase positive & non-motile

65
Q

What is Diphtheria?

What causes it?

How is it spread?

A
  • A disease of the upper respiratory tract, although cutaneous diphtheria may also occur
  • It is caused by infection with the bacterium Corynebacterium diphtheriae
  • These bacteria are usually spread in droplets of moisture coughed into the air or by skin to skin contact
66
Q

List the symptoms of Diphtheria.

A
  • Sore throat
  • Fever
  • Nausea
  • Vomiting
  • Headache
  • Fast heart rate
67
Q

Describe the Genus: Corynebacterium.

A
  • Irregularly shaped Gram-positive rods
  • Aerobic , non-motile &
    non-sporing
  • Diverse group of bacteria
  • Includes animal and plant pathogens, as well as saprophytes
68
Q

Which bacterium?

  • Grows best on blood or serum-containing medium at 35-37C
  • Most strains require nicotinic and pantothenic acids for growth
  • Colonies appear grey or black on blood agar containing tellurite
  • 3 biotypes, gravis, intermedius & mitis
A

Corynebacterium diphtheriae.

69
Q

List the common symptoms of diphtheria.

A
  • Low-grade fever (less than 38.5ºC)
  • Inflammation of the throat (most commonly the pharynx but may also affect the larynx or nose
  • Formation of a thick pseudomembrane
  • Swollen lymph nodes and glands (so-called bull-neck appearance)
  • Rapid, faint pulse
  • Pale, shocked appearance
70
Q

List the possible complications associated with diphtheria sufferers?

A
  • Respiratory obstruction
  • Acute systemic toxicity (organ failure)
  • Myocarditis (inflammation of the heart). Death is most commonly due to heart failure and cardiac arrhythmias
  • Peripheral neuritis (neural condition)
  • Nephritis (inflammation of the kidney)
71
Q

The structural gene for ___1___ toxin, tox, is carried by a family of closely related corynebacteriophages of which the ___2___-phage is the most extensively studied.
The regulation of ___1___ tox expression is mediated by an iron-activated repressor, DtxR, which is encoded on the C. diphtheriae genome.

A
  1. Diphtheria

2. Beta

72
Q

Diphtheria toxin is composed of a single polypeptide chain of _____ amino acids.
It is composed of three structural/functional domains:

Describe each.

A

535.

  1. An N-terminal ADP-ribosyltransferase (catalytic)
  2. A region which facilitates the delivery of the catalytic domain across the cell membrane (transmembrane domain)
  3. The eukaryotic cell receptor binding domain
73
Q

Describe the mode of action of the Diphtheria toxin.

3

A
  • The toxin binds to its cell surface receptor and is internalized by receptor-mediated endocytosis
  • Upon acidification of the endosome the transmembrane domain inserts into the membrane
  • The catalytic domain is cleaved off & delivered to the cytosol
74
Q

What does the Diphtheria exotoxin cause?

How?

A

It causes the death of epithelial cells and neutrophils by inhibiting protein synthesis.

75
Q

Describe the Elek Test for the Diphtheria toxin.

A
  • Cultures are streaked horizontally, then overlayed by an antitoxin-impregnated strip
  • Toxin and antitoxin diffuse into the culture during incubation and precipitin lines develop where toxin and antitoxin are present
  • Positive reactions are indicated by the formation of precipitin lines
76
Q

What is used to treat Diphtheria?

A
  • Diphtherial antitoxin

- Antibiotics

77
Q

Name the clinical test.

  • This is a diagnostic test designed to evaluate susceptibility to diphtheria
  • A small amount of diphtheria toxin is injected into the skin; the injection will produce an area of redness and swelling in individuals with low levels of antibody (i.e., little immunity ) against the toxin
  • If the individual is immune to diphtheria, the antibody in the system will neutralize the toxin and no skin reaction will occur
A

Schick Test for Immunity.

78
Q

What is Cutaneous diphtheria?

A

An infection at a wound or skin lesion leading to slow-healing ulceration.

79
Q

Mycobacteria contain a waxy lipid, _____ acid, in their cell wall. The lipid makes the cells more durable and is commonly associated with pathogenicity.

A
  1. Mycolic
80
Q

What is trehalose dimycolate?

A

The cord factor.

81
Q

List the symptoms of TB.

A
  • Bad cough
  • Pain in the chest
  • Coughing up blood or sputum
  • Weakness or fatigue
  • Weight loss
  • No appetite
  • Chills
  • Fever
  • Sweating at night
82
Q

Describe the usual treatment of TB.

Describe the 3 phases of this treatment and what each drug does.

A

Usual treatment of TB is a combination of isoniazid, rifampicin, pyrazinamide and ethambutol for 2 months followed by isoniazid and rifampicin alone for a further 4 months, ideally given daily or three times per week.

  • In the first 2 weeks, the large numbers of actively growing bacteria are killed, principally by isoniazid, helped by rifampicin and ethambutol. The patient ceases to be infective
  • In the following few weeks the less active bacteria within macrophage and caseous material are killed by pyrazinamide and rifampicin
  • During the remaining treatment any remaining or dormant bacteria are slowly killed by rifampicin and isoniazid
83
Q

Name the disease.

  • Is a highly contagious disease that is an exclusively human pathogen
  • One of the most frequent and serious bacterial respiratory diseases of children in communities not protected by vaccination.
  • Before the introduction of a vaccine hundreds of thousands of cases occurred each year, with a significant mortality rate
  • Caused by Bordetella pertussis
    - produces adhesins and several toxins as major virulence factors
  • Transmission is by droplet inhalation
A

Whooping Cough.

84
Q

Name and describe the 3 layers of the mucociliary transport system.

A
  • Ciliated Epithelial Cells - each cell has many hair-like structures on its surface called cilia
  • Aqueous Layer - a thin layer of low-viscosity fluid. The depth of this layer is critical for effective cilial movement
  • Gel Layer - mucus floats on top of the aqueous layer. It traps pathogens and is moved from the airways by the cilia
85
Q

What is Filamentous Hemagglutinin (FHA)?

A

FHA is a large 220kDa protein that forms filamentous structures on the cell surface. It binds to galactose residues on a sulphated glycolipid called sulfatide which is very common on the surface of ciliated cells.

86
Q

Read:

Haemophilus influenzae.

A
  • Most strains of Haemophilus influenzae are non-capsulated but some strains possess a polysaccharide capsule (types a–f)
  • H. influenzae type b (Hib) is a major human pathogen that causes invasive & non-invasive infections, including meningitis and epiglottitis
  • Non-capsulate strains cause approximately 10% of invasive infections and 90% of non-invasive respiratory infections, including otitis media and acute exacerbations of chronic obstructive airway disease
  • Some 20% of H. influenzae strains are ampicillin resistant (B-lactamase mediated); ceftriaxone (broad-spectrum cephalosporin) is now the treatment of choice for invasive disease
  • Conjugate Hib vaccine is routinely offered

The Nervous System & Respiratory Diseases (15 decks)

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