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MD3001 > RTIs 1 > Flashcards

RTIs 1 Flashcards

1
Q

Which type of infection is responsible for the greatest amount of deaths in the world ?

A

Acute respiratory infections

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2
Q

Identify examples of RTIs.

A
  • Common cold
  • Otitis and Sinusitis
  • Oral Cavity infections
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3
Q

What are our sources of infection (RTIs especially) ?

A
  • Other humans (i.e. social/family contact)
  • Environment (e.g. air conditioning systems)
  • Animals (e.g. psitaccosis)
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4
Q

How does morphology of the Eustachian tube affect likelihood of infection ?

A

Shorter flatter Eustachian tube means infection more common under 7 years.
Indeed, the short flat eustachian tube means infection can ascend through the tube to the middle ear, resulting in otits media.
Eustachian tube is also connected to the mastoid sinuses which means infections can spread into said sinuses and block drainage and result in secondary infection (i.e. resulting in sinusitis).

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5
Q

What factors are likely to lead to mucus accumulation in the upper respiratory tract ?

A

Swollen mucosa
Vascular enlargement
Arrested cilia
Clogged ostia

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6
Q

What are symptoms of mucus accumulation in the upper respiratory tract ?

A

Nasal congestion
Chest congestion
Sinus Pressure
Cough

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7
Q

What are the risks of otitis media ?

A

Possibly rupture, releasing pus and damaging hearing.

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8
Q

What other factors beyond infection in the eustachian tube spreading to the mastoid sinuses, can lead to blockage of drainage in mastoid sinuses and thereby secondary infection and sinusitis ?

A

Inflammation due to allergy

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9
Q

Identify the main components of the respiratory innate defense.

A
  • Nasal mucus
  • Ciliated cells
  • Mucociliary clearance elevator
  • Alveolar macrophages
  • Polymorphonuclear leucocytes
  • Complement
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10
Q

Explain how mucociliary clearance elevator works.

A
  • Particles are trapped in mucus covering the respiratory tract
  • Ciliary action drags the mucus upwards
  • Material is expectorated
  • Disruption of system results in chronic infections e.g., cystic fibrosis, bronchiectasis.
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11
Q

Identify two organisms in the common normal microbiota of the RT (i.e. >50% normal people).

A

Bacteroides spp.

Candida albicans

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12
Q

Identify two organisms in the occasional normal microbiota of the RT (i.e. <10% normal people).

A

Streptococcus pyogenes

Streptococcus pneumoniae

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13
Q

Identify two organisms who have latent state in tissues in the RT.

A

Epstein-Barr virus (EBV)

Cytomegalovirus (CMV)

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14
Q

Identify the main RT host defenses.

A
  • Saliva
  • Mucus
  • Cilia (muco-ciliary escalator/elevator)
  • Nasal secretions
  • Antimicrobial peptides
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15
Q

COMMON COLD

  • Other name
  • Transmission
  • Causative agents. Do these agents have the same pathology and epidemiology ?
  • What are the main clinical features of the common cold ?
  • How severe is the common cold ?
  • Is there any vaccine against the common cold ?
  • Describe the pathogenesis of the common cold
A

-Other name: Acute coryza
-Transmission:
Aerosol
Virus-contaminated hands

-Causative agents. Do these agents have the same pathology and epidemiology ?
-40% Rhinoviruses (>100 serotypes)
-30% Coronaviruses (>3 serotypes)
-Coxsackie virus A
-Echovirus
-Parainfluenza virus
Differences in pathology and epidemiology

-What are the main clinical features of the common cold ?
• tiredness
• slight pyrexia
• malaise
• sore nose & pharynx
• profuse, watery nasal discharge becoming mucopurulent
• sneezing in early stages
• secondary bacterial infection occurs in minority

  • How severe is the common cold ? Generally mild and self-limiting
  • Is there any vaccine against the common cold ? No
  • Describe the pathogenesis of the common cold: Colonisation of the respiratory epithelium, replication in this epithelium, exposing basement layer making it more susceptible to infection.
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16
Q

Identify causative agents for acute pharyngitis and tonsilitis.

A 
Viruses:
• Herpes simplex virus type I (HSV-1) 
• Epstein-Barr virus (EBV)
• Cytomegalovirus (CMV)
• Rhinovirus
• Coronavirus
• Adenovirus

Bacteria:
• Streptococcus pyogenes
• Haemophilus influenzae
• Corynebacterium diphtheriae

17
Q

Cytomegalovirus (CMV) Infection

  • Transmission
  • Symptoms
  • Diagnosis
  • Treatment
A

Cytomegalovirus (CMV) Infection
-Transmission: Transmission in body secretions and organ transplants

-Symptoms: Usually asymptomatic or mild in healthy adults

-Diagnosis:
• Diagnose 2° infection: IgM in blood
• Diagnose CMV pneumonitis: CMV antigen (Ag) in Bronchoalveolar lavage (BAL)

-Treatment: Treatment with ganciclovir

18
Q

Identify a virus which can reactivate and cause disease when cell- mediated immunity is compromised.

A

Cytomegalovirus (CMV)

19
Q

What organism is associated with Glandular fever ?

A

Epstein-Barr Virus (EBV)

20
Q

EBV

  • Transmission
  • Where does it replicate ?
A
  • Transmission: Transmitted by saliva and aerosol

- Where does it replicate ? Replicates specifically in B lymphocytes (CD21 receptor)

21
Q

Glandular Fever

  • Clinical Features
  • Diagnosis
  • Treatment
  • Complications
A 
-Clinical Features: 
• Fever
• Headache 
• Malaise
• Sore throat 
• Anorexia
• Palatal petechiae
• Cervical lymphadenopathy 
• Splenomegaly
• Mild hepatitis
• Swollen tonsils and uvula
• White exudate

-Diagnosis:
Detection of heterophile antibodies (IgM) specific for EBV:
• Monospot test
• If negative – consider HIV conversion

-Treatment:
• Not to be treated with antibiotics (ampicillin and amoxycillin)!
• Cannot really treat it (no antiviral for it)
• Contact sports or heavy lifting should be avoided durind the first month of illness and until any splenomegaly has resolved

-Complications:
• Burkitt’s lymphoma
• Nasopharyngeal carcinoma
• Guillain-Barré syndrome

22
Q

TONSILLITIS

  • Causative organisms
  • Transmission
  • Treatment
  • Clinical Features
A
  • Causative organisms: Streptococcus pyogenes
  • Transmission: Transmission by airborne droplets and contact

-Treatment: Can be treated with penicillin (most of the time, not necessary)
Increasing resistance to erythromycin and tetracycline!

-Clinical Features: 
– Fever
– Pain in throat
– Enlargement of tonsils
– Tonsillar lymphadenopathy
– Sometimes asymptomatic! (15-20% of infected become asymptomatic carriers)
23
Q

Strep Pyogenes

  • Class of pathogen
  • Infection of Upper respiratory tract it causes
  • Treatment
  • Complications
A

-Class of pathogen:
• Group A Streptococcus
• Gram positive cocci in chains

  • Infection of Upper respiratory tract it causes: Tonsillitis
  • Treatment: Penicillin
-Complications: 
• Scarlet Fever (caused by erythrogenic toxin from S. pyogenes)
• Peritonsillar abscess (=“quinsy”)
• Otitis media / sinusitis
• Rheumatic heart disease
• Glomerulonephritis
24
Q

DIPHTERIA

  • Causative organism
  • Clinical Features
  • Diagnosis
  • Treatment
  • Prevention
A

-Causative organism: Corynebacterium diphtheriae, but only the toxin-producing strains cause disease.

-Clinical Features: 
• Sore throat
• Fever
• Formation of pseudomembrane
• Lymphadenopathy
• Oedema of anterior cervical tissue (bull-neck)

-Diagnosis:
Made on clinical grounds as therapy is usually urgently required

-Treatment:
• Prompt anti-toxin therapy administered intramuscularly
• Concurrent antibiotics (penicillin or erythromycin)
• Strict isolation
• Also contact tracing + vaccination and treatment of contacts

-Prevention:
• Childhood immunisation with toxoid vaccine
• Booster doses given if travelling to endemic areas if >10 years have elapsed since primary vaccination

25
Q

Corynebacterium diphtheriae

  • Kind of pathogen
  • Composition of toxins produced by Corynebacterium diphtheriae
  • Transmission
  • Part of body colonised
A

-Kind of pathogen: Human pathogen

-Composition of toxins produced by Corynebacterium diphtheriae:
• Subunit A (Active): responsible for clinical toxicity
• Subunit B (Binding): transports toxin to receptors on myocardial and peripheral nerve cells

  • Transmission: Airborne droplets
  • Part of body colonised: Colonises pharynx, larynx and nose (rarely skin and genital tract)
26
Q

Parotitis

  • Clinical features
  • Causative organism. What family does this organism belong to ?
  • Transmission
  • Diagnosis
  • Treatment
  • Prevention
  • Complications
A 
-Clinical features: 
• Fever
• Malaise
• Headache
• Anorexia
• Trismus
• Severe pain and swelling of parotid gland(s)

-Causative organism:
Mumps virus
Paramyxovirus family

-Transmission: Transmission by droplet spread and fomites

-Diagnosis:
• Diagnosis is based on clinical features
BUT IgM serology can be performed in doubtful cases from saliva, CSF or urine

-Treatment:
• Mouth care
• Nutritional
• Analgesia

-Prevention:
• Active immunisation
• Measles-Mumps-Rubella (MMR) vaccine

-Complications:
• CNS involvement
• Epididymo-orchitis (~30% infected after puberty)

27
Q

Acute epiglottis

  • Causative organism. What family does this organism belong to ?
  • Clinical features
  • Prevention
  • Diagnosis
  • Treatment
A

-Causative organism. What family does this organism belong to ?
Haemophilus influenzae
Pasteurellaceae family, Gram negative bacillus

-Clinical features: 
• High fever
• Massive oedema of the epiglottis
• Severe airflow obstruction resulting in breathing difficulties 
• Bacteraemia

-Prevention:
Hib vaccine against Haemophilus influenzae type B

-Diagnosis:
• DO NOT examine throat or take throat swabs as this will precipitate complete obstruction of airway.
• Blood cultures to isolate H. influenzae

-Treatment
• LIFE-THREATENING EMERGENCY
• Requires urgent endotracheal intubation
• Intravenous antibiotics (ceftriaxone or chloramphenicol)
Some clinical strains have β- lactamase and may be resistant to ampicillin so no use ampicilin

28
Q

Laryngitis and tracheitis

  • Causative organisms
  • Clinical features
A 
-Causative organisms: 
• Parainfluenza virus
• Respiratory Syncytial virus 
• Influenza virus
• Adenovirus

-Clinical features:
• In adults: hoarseness; retrosternal pain
• In children: dry cough; inspiratory stridor (croup)

29
Q

Wooping cough

  • Causative organism. What family of organisms does this organism belong to ? What are the toxic factors associated with this organism ?
  • Transmission
  • Clinical features
  • Diagnosis
  • Treatment
  • Prevention
A

-Causative organism. What family of organisms does this organism belong to ?
Bordetella pertussis
Gram negative aerobic coccobacillus, human pathogen
Toxic factors associated with Bordetella pertussis:
• Pertussis toxin (Ptx)
• Adenylate cyclase toxin
• Tracheal cytotoxin
• Endotoxin

-Transmission: Transmission by air-borne droplets

-Clinical features:
1) Catarrhal stage (1 week):
• Highly contagious
• Malaise
• Mucoid rhinorrhoea
• Conjunctivitis
2) Paroxysmal stage (1-4 weeks):
• Paroxysms of coughing with a classic inspiratory “whoop”
• Lumen of respiratory tract is compromised by mucus secretion and mucosal oedema

-Diagnosis: 
• Clinically by characteristic “whoop” 
OR
• Bacterial isolation from nasopharyngeal swabs
OR
• NAAT

-Treatment:
• In catarrhal stage can be treated with erythromycin
• In paroxysmal stage, antibiotics have no effect
• Isolation + Supportive care (hospitalisation for infants)

-Prevention:
Vaccination

30
Q

What is the mechanism of action of Bordetella pertussis ?

A

Attaches to (thanks to surface components e.g. filamentous haemagglutinin FHA) and replicates in the ciliated respiratory epithelium, without invading deeper structures.

31
Q

Acute bronchitis

  • Define
  • Causative organisms
A
  • Define: Inflammation of the tracheobronchial tree

- Causative organisms: rhinovirus, coronovirus, adenovirus, or Mycoplasma pneumoniae

32
Q

What are the main clinical features of chronic bronchitis ? What is it due to ?

A

-Characterised by cough and excessive mucus secretion in tracheobronchial tree

-Not attributable to specific diseases such as TB, bronchiectasis, asthma but rather due to anatomical disturbance of the respiratory system
(e.g. a) Immune deficit- SCID b) Ciliary deficit- Kartegener syndrome and smoking c)
Excessively thick mucus- CF)

33
Q

Bronchiolitis

  • Define
  • Causative organism
  • Complications
  • Age groups
A
  • Definition: Infection of bronchioles resulting in fine bore.
  • Causative organism: Mainly due to Respiratory Syncytial Virus.
  • Complications: epithelial cell necrosis
  • Age groups: Restricted to children < 2 years old

MD3001 (75 decks)

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