RTIs 1 Flashcards
Which type of infection is responsible for the greatest amount of deaths in the world ?
Acute respiratory infections
Identify examples of RTIs.
- Common cold
- Otitis and Sinusitis
- Oral Cavity infections
What are our sources of infection (RTIs especially) ?
- Other humans (i.e. social/family contact)
- Environment (e.g. air conditioning systems)
- Animals (e.g. psitaccosis)
How does morphology of the Eustachian tube affect likelihood of infection ?
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).
What factors are likely to lead to mucus accumulation in the upper respiratory tract ?
Swollen mucosa
Vascular enlargement
Arrested cilia
Clogged ostia
What are symptoms of mucus accumulation in the upper respiratory tract ?
Nasal congestion
Chest congestion
Sinus Pressure
Cough
What are the risks of otitis media ?
Possibly rupture, releasing pus and damaging hearing.
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 ?
Inflammation due to allergy
Identify the main components of the respiratory innate defense.
- Nasal mucus
- Ciliated cells
- Mucociliary clearance elevator
- Alveolar macrophages
- Polymorphonuclear leucocytes
- Complement
Explain how mucociliary clearance elevator works.
- 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.
Identify two organisms in the common normal microbiota of the RT (i.e. >50% normal people).
Bacteroides spp.
Candida albicans
Identify two organisms in the occasional normal microbiota of the RT (i.e. <10% normal people).
Streptococcus pyogenes
Streptococcus pneumoniae
Identify two organisms who have latent state in tissues in the RT.
Epstein-Barr virus (EBV)
Cytomegalovirus (CMV)
Identify the main RT host defenses.
- Saliva
- Mucus
- Cilia (muco-ciliary escalator/elevator)
- Nasal secretions
- Antimicrobial peptides
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
-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.
Identify causative agents for acute pharyngitis and tonsilitis.
Viruses: • Herpes simplex virus type I (HSV-1) • Epstein-Barr virus (EBV) • Cytomegalovirus (CMV) • Rhinovirus • Coronavirus • Adenovirus
Bacteria:
• Streptococcus pyogenes
• Haemophilus influenzae
• Corynebacterium diphtheriae
Cytomegalovirus (CMV) Infection
- Transmission
- Symptoms
- Diagnosis
- Treatment
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
Identify a virus which can reactivate and cause disease when cell- mediated immunity is compromised.
Cytomegalovirus (CMV)
What organism is associated with Glandular fever ?
Epstein-Barr Virus (EBV)
EBV
- Transmission
- Where does it replicate ?
- Transmission: Transmitted by saliva and aerosol
- Where does it replicate ? Replicates specifically in B lymphocytes (CD21 receptor)
Glandular Fever
- Clinical Features
- Diagnosis
- Treatment
- Complications
-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
TONSILLITIS
- Causative organisms
- Transmission
- Treatment
- Clinical Features
- 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)
Strep Pyogenes
- Class of pathogen
- Infection of Upper respiratory tract it causes
- Treatment
- Complications
-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
DIPHTERIA
- Causative organism
- Clinical Features
- Diagnosis
- Treatment
- Prevention
-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
