Respiratory Infections (L26-31) Flashcards
1
Q
Describe Staphylococcus aureus.
A
- Gram positive cocci in irregular clusters
- Catalase positive
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
3
Q
Describe Streptococcus pyogenes.
A
- Gram positive cocci in chains
- Catalase negative
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.
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
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
7
Q
Describe Streptococcus pneumoniae.
A
- Gram positive diplococci
- Catalase negative
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.
9
Q
Name some upper respiratory infections.
A
- Common cold
- Sinusitis
- Otitis (middle ear)
- Pharyngitis
- Epiglottitis
- Laryngotracheitis- laryngitis and croup
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
11
Q
What are the initial symptoms of a cold?
A
- Runny, stuffy nose
- Sneezing
- Usually no fever
12
Q
What are the symptoms of epiglottitis?
A
- Difficulty in breathing
- Muffled speech
- Drooling
- Stridor (noisy breathing or wheezing)
13
Q
What are the symptoms of laryngotracheitis?
A
- Rapid breathing
- A bluish colouration of the skin through lack of oxygen
14
Q
True or false? Common colds usually recognised clinically.
A
True.
15
Q
How are pharyngitis and laryngotracheitis diagnosed?
A
Bacterial cultures of throat swabs.
16
Q
How is epiglottitis diagnosed?
A
Blood cultures.
17
Q
How do you treat viral infections?
And what with?
A
Symptomatically.
- Decongestants
- Antipyretics
- Fluids
18
Q
How do you treat bacterial pharyngitis and epiglottitis?
A
With antibiotics.
19
Q
What causes the common cold?
A
A range of viruses. Mainly rhinoviruses.
20
Q
How long does the common cold last?
A
48-72 hours.
21
Q
What diseases may occur as a secondary bacterial infection to the common cold.
A
- Otitis media
- Sinusitis
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.
23
Q
What is the primary function of the sinuses?
A
To warm, moisten and filter the air in the nasal cavity.
24
Q
Acute sinusitis most often follows a _____ _____.
A
Common cold.
25
Which bacteria most commonly cause acute sinusitis?
- Streptococcus pneumonia
- Haemophilus influenzae
- Moraxella catarrhalis
26
_____ sinusitis is also commonly a mixed infection of aerobic and anaerobic organisms.
Chronic.
27
Describe Moraxella catarrhalis.
- 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
28
Describe the pathogenesis of sinusitis.
- 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.
29
Which bacteria most commonly cause otitis media?
- Streptococcus pneumonia
- Haemophilus influenzae
- Streptococcus pyogenes (group A)
- Moraxella catarrhalis
30
What are the symptoms of otitis media?
- Acute ear ache (usually confined to one side)
- High fever
- Nausea
- Vomiting
- Diarrhoea
31
How would you go about diagnosing otitis media?
What would you see?
- By looking into the ear canal with an otoscope
| - Bulging, reddened tympanic membrane (ear drum)
32
How do you treat otitis media?
- Analgesics
| - Antibiotics
33
What are Pharyngitis & Tonsillitis?
Infections in the throat which cause inflammation of the lymphoid tissue.
34
What causes Pharyngitis & Tonsillitis?
Bacterial, viral or fungal infections.
35
How do you treat bacterial Pharyngitis & Tonsillitis?
Penicillin G.
36
What is acute laryngitis?
An infection of the larynx (voice box).
37
What causes laryngitis?
Viral and bacterial infections.
38
List the common symptoms of laryngitis.
- Hoarseness or loss of voice
- Raw throat
- Dry cough
- Tickling sensation in the throat
- Persistent need to clear the throat
39
What does Haemophilus influenzae infect and cause?
The upper respiratory tract and causes acute respiratory infections (pneumonia, bronchitis), acute conjunctivitis, otitis media and bacterial meningitis).
40
True or false? A vaccine (Hib vaccine) to stimulate antibodies against the capsule is now available, and has almost eliminated the disease.
True.
41
True or false? All species of Haemophilus are catalase and oxidase positive.
True.
42
Name the 3 layers of the meninges from superficial to deep.
- The dura mater
- The arachnoid mater
- The pia mater
43
Describe the dura mater.
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
Describe the arachnoid mater.
The arachnoid mater is a fibrocellular layer. Tight junctions between cells form a fluid-tight compartment.
45
Describe the pia mater.
The pia mater is a thin layer that closely covers the surface of the brain and spinal cord.
46
What is meningitis?
An infection which causes inflammation of the membranes covering the brain and spinal cord.
47
What causes meningitis?
| What are the effects of each?
- 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
What is a lumbar puncture a diagnostic test for?
Meningitis.
49
What is epiglottitis?
An acute infection of the epiglottis.
50
What happens to the epiglottis during epiglottitis?
The epiglottis rapidly swells, blocking the passage of air into the lungs. This is potentially fatal and is a medical emergency.
51
What causes epiglottitis?
Haemophilus influenzae type B.
52
Which ages are susceptible to epiglottitis?
Epiglottitis tends to occur in children aged between 1-6 years, although it may occur at any age.
53
How is epiglottitis treated?
- 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
_____ 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.
Staphylococcus.
55
_____ 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.
Streptococcus.
56
Staphylococcus are divided into two major groups using the coagulase test.
Name the two groups and the species within each.
Coagulase +ve:
- S. aureus
Coagulase -ve:
- S. epidermidis
- S. saprophyticus
57
What does coagulase do?
Coagulase converts fibrinogen to insoluble fibrin which causes the staphylococci to clump together.
58
Describe the Exfoliative toxins released by Staphylococcus aureus and the effects they cause?
At risk age-groups?
- 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
What are the clinical manifestations of Toxic shock syndrome toxin-1?
- Low blood pressure
- Fever
- Diarrhoea
- Extensive skin rash
- Shedding of skin
60
How are Staphylococcal diseases treated?
With antibiotic therapy.
61
How is scarlet fever spread?
By inhalation of infective respiratory droplets.
62
What is Necrotizing fasciitis?
A deep-seated infection of subcutaneous tissue that causes destruction of the sheath covering skeletal muscle.
63
What are the clinical manifestations of Necrotizing fasciitis?
Mortality rate?
- Severe pain
- Severe systemic toxicity
- Cutaneous gangrene
- Haemorrhagic fluid leaking from a wound
- Untreated progresses to multiple organ dysfunction
- Overall mortality 30%
64
Describe the bacterium Neisseria meningitidis.
- Gram-negative, aerobic encapsulated diplococcus
| - Oxidase & catalase positive & non-motile
65
What is Diphtheria?
What causes it?
How is it spread?
- 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
List the symptoms of Diphtheria.
- Sore throat
- Fever
- Nausea
- Vomiting
- Headache
- Fast heart rate
67
Describe the Genus: Corynebacterium.
- Irregularly shaped Gram-positive rods
- Aerobic , non-motile &
non-sporing
- Diverse group of bacteria
- Includes animal and plant pathogens, as well as saprophytes
68
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
Corynebacterium diphtheriae.
69
List the common symptoms of diphtheria.
- 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
List the possible complications associated with diphtheria sufferers?
- 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
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.
1. Diphtheria
| 2. Beta
72
Diphtheria toxin is composed of a single polypeptide chain of _____ amino acids.
It is composed of three structural/functional domains:
Describe each.
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
Describe the mode of action of the Diphtheria toxin.
| 3
- 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
What does the Diphtheria exotoxin cause?
| How?
It causes the death of epithelial cells and neutrophils by inhibiting protein synthesis.
75
Describe the Elek Test for the Diphtheria toxin.
- 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
What is used to treat Diphtheria?
- Diphtherial antitoxin
| - Antibiotics
77
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
Schick Test for Immunity.
78
What is Cutaneous diphtheria?
An infection at a wound or skin lesion leading to slow-healing ulceration.
79
Mycobacteria contain a waxy lipid, _____ acid, in their cell wall. The lipid makes the cells more durable and is commonly associated with pathogenicity.
1. Mycolic
80
What is trehalose dimycolate?
The cord factor.
81
List the symptoms of TB.
- Bad cough
- Pain in the chest
- Coughing up blood or sputum
- Weakness or fatigue
- Weight loss
- No appetite
- Chills
- Fever
- Sweating at night
82
Describe the usual treatment of TB.
Describe the 3 phases of this treatment and what each drug does.
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
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
Whooping Cough.
84
Name and describe the 3 layers of the mucociliary transport system.
- 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
What is Filamentous Hemagglutinin (FHA)?
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
Read:
| Haemophilus influenzae.
- 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
