Respiratory Tract Infections Flashcards
What are the top 6 killers - infections responsible for the greatest number of deaths in the world?
- Acute respiratory tract infections
- HIV/AIDS
- Diarrheal diseases
- TB (chronic infection)
- malaria
- measles
What are common bacteria in the normal microbiota of the respiratory tract?
- Bacteroides spp.
- Candida albicans (causes thrush)
- Oral Streptococci
- Haemophilus influenzae (causes menigitis)
What are occasional organisms found in the normal microbiota of the respiratory tract of people?
- Streptococcus pyogenes
- Streptococcus pneumoniae
- Neisseria meningitidis
What organisms are found in latent state in tissues?
- Herpes simplex virus type I (HSV)
- Epstein-Barr virus (EBV) - glandular fever
- Cytomegalovirus (CMV)
- Mycobacterium tuberculosis
What are the host defence mechanisms of the respiratory tract?
- saliva
- mucus
- cilia (goblet cells)
- nasal secretions
- antimicrobiral peptides - defensins, lysozyme
What group of people experience the most cases of whopping cough?
90% of cases are children <5
What is the method of transmission of whopping cough?
air-born droplets
What is the incubation period of whopping cough?
1-3 weeks
What are the clinical features of whopping cough?
- Catarrhal stage (week 1)
- highly contagious
- malaose (feeling unwell)
- Mucoid rhinorrhoea (nasal cavity filled with mucus)
- Conjunctivitis
- Paroxysmal stage (1-4 weeks)
- coughing eith classive inspiratory ‘whoop’
- Lumen of respiratory tract is compromised by mucus secretion and mucosal oedema
How is whopping cough diagnosed?
- Clinically characterised by ‘whoop’
- Bacterial isolation from nasopharyngeal swabs
- NAAT (nucleic acid amplification technique)
What is the treatment of whopping cough?
- Catarrhal stage = erythromycin
- paroxysmal stage = antibiotics have no effect
- isolation
- supportive care (hospitalisation for infants)
What is the prevention treatment of whopping cough?
vaccination
What is the causative pathogen of whopping cough? And what type of bacteria is this?
Bordetella pertussis
gram negtaive aerobic coccobacillus
What does Bordetella pertussis target and what are its toxic factors?
- attached to and replicates in the ciliated respiratory epithelium - filamentous haemagglutinin (FHA)
- Toxic factors:
- Pertussis toxin (Ptx) - similar to diptheria
- Adenylate cyclase toxin - affects neutrophil function (Increases cAMP)
- Tracheal cytotoxin
- Endotoxin
What is acute bronchitis?
inflammation of the tracheobronchial tree
What is acute bronchitis usually caused by?
- rhinovirus
- coronavirus
- adenovirus
- mycoplasma pneumoniae
What secondary infections can cause acute bronchitis?
- streptococcis pnemoniae
- haemophilus influenzae
**Causes more problems (bacterial and viral together)
What is chronic bronchitis characterised by?
cough and excessive mucus sewcretion in tracheobronchial tree
Not attributable to a specific disease
What are the anatomical disturbances to the respiratory system that cause acute bronchitis?
- Immune deficit: SCID
- Ciliary deficit: Kartegener Syndrome, smoking
- Excessively thick mucus: cystic fibrosis
What are the main features of bronchiolitis?
- restricted to children <2 years old
- bronchioles have such a fine bore
- Infection may lead to epithelial cell necrosis
- Mainly caused by Respiratory Syncytial Virus (RSV)
What is pneumonia?
inflammation of the substance of the lungs
How is pneumonia confirmed?
on a chest radiograph
How does pneumonia get into the lung?
acess to lower respiratory tract by inhalatiom of aerosolised microbes or by aspiration of normal flora of the upper respiratory tract
What is an important determinant of the type of pneumonia?
AGE
Describe pneumonia in children?
- Mainly viral
- Neonates may develop pneumonia caused by streptococcus B, E.coli, Chlamydia trachomatis (aquired from mother during birth)
Describe pneumonia in adults
- mainly bacterial
- aetiology varies with age, underlying disease, occupation and geohraphical risk factors
Aetiological causes of viral pneumonia
- Influenza virus
- Measles
- Coronavirus
- Parainfluenza virus
- Respiratory syncytial virus (RSV)
- Cytomegalovirus (CMV)
- Adenovirus
Aetiological causes of bacterial pneumonia
- Streptococcus pneumoniae
- Mycobacterium tuberculosis
- Haemophilus influenzae
- Pseudomonas aeruginosa
- Staphylococcus aureus
What is atypical pneumonia and what is it caused by?
- Failure to respond to treatment with penicillin
- Mycoplasma pneumoniae
- Legionella pneumophilia
- Chlamydia psittaci
- Chlamydia pneumoniae
- Coxiella burnetii
What are the anatomical classifications of pneumonia?
- Lobar pneumonia - distinct region of lung e.g. lobe
- Bronchopneumonia
- Diffuse, patchy consolidation
- Assocaited with bronchi and bronchioles
- Intersitital pneumonia
- invasion of lung interstitum
- Usually characteristic of viral infection
- Necrotising pneumonia
- lung abscesses and destruction of parenchyma
What are the initial clinical features of Streptococcus pneumoniae?
- abrupt onset
- rigors
- fever
- malaise
- tachycardia
- dry cough
What are the initital clinical features of Streptococcus pneumoniae followed by?
- productive cough and rusty sputum
- spiky temperature
- lobular consolidation
What are the clinical features of Mycoplasma pneumoniae
- fever
- dry cough
- dyspnoea
- lymphadenopathy
What are the clinical features of Haemophilus influenzae
- mainly occurs in children
- consolidation or patchy bronchopneumonia
- persistent purulent sputum and malaise
What is legionella pneumophila caused by?
legionnaire’s disease
What is legionella pneumophila?
severe systemic infection with pneumonia
What are the clinical features of legionella pneumophila?
- tachypnoea
- purulent sputum
- chest x-ray shows consolidation
What is legionella pneumophila?
gram negative bacillus
How is legionella pneumophila transmitted?
aerosol, but not person-person
How does legionella pneumophila usually occur?
in outbreaks
What is the laboratory diagnosis of Legionnaire’s Disease
- gram staining of sputum
- recognition with serotype-specific floursecent antibody
- Culture of Legionella on cystine yeast extract agar
- Detection of antigen in urine
- 4-fold rise in antibody
What are the clinical features of measles?
- fever
- runny nose
- Kolpik’s spots
- characteristic rash
What can measles result in?
neurological complications
What can measles cause?
Can cause “giant cell” (Hecht’s) pneumonia in the immunocompromised – usually fatal
What type of virus is measles?
paramyxovirus
How is the measles virus spread?
aerosol
Where does the measles virus replicate?
lower respiratory tract
What is the incubation period of measles?
10-14 days
How do you diagnose the measles virus?
- serology for measles
- virus isolation
- viral detection
What is the treatment of measles virus?
ribavirin treatment (anti-viral)
antibiotics for secondary bacterial infections
methods of the prevention of the measles virus
immunisation with highly effective, live, attenuated MMR vaccine
What is an endemic
present in a community at all times; at a relatively low to medium frequency but at a steady state
What is an epidemic?
sudden severe outbreak within a region or group
what is a pandemic?
occurs when an epidemic becomes widespread and affects a whole region, a continent or the entire world
What type of virus is influenza?
orthomyxovirus
What are the three tpes of influenza?
- Type A = epidemics and pandemics, animal resovoir
- Type B = epidemics, no animak hosts
- Type C = minor respiratory illness
Dsecribe the influenza virus?
- type-specific antigens on cell surface (spikes)
- Haemagglutinin (H)
- Neuraminidase (N)
- Single-standed RNA
- Segmented genome
- Resassortment gives ruse ti novel combinations of H and N genes
What mild changes does influenza undergo during spread through the host species?
Antigenic drift
- small point mutations in the H and N antigens occurs constantly
- Allows the virus to multiply in individuals with immunity to preceding strains
- new subtype can reinfect community
- occurs with all influenza types
What major changes does influenza undergo during spread through the host species?
Antigenic shift
- sudden major change based on recombination between two different strains when they infect the same cell
- produces a virus with novel surface glycoproteins
- new strain can spread through previously immune populations - new pandemic
What makes a pandemic?
- antigenic shift
- most people have no immunity
- attach rate is high - it spreads rapidly
- mortaltity can be high
What type of virus is swine flu? And who did it mostly affect?
H1N1 virus
People inder the age of 40. Attack rate was high but mortality was low
How is influenza diagnosed?
- Nasopharyngeal aspirate
- Direct immunofluorescent
- culture
- NAAT detection
What is the treatment used for influenza?
- Amantadine
- Zanamavir
- Oseltamivir (Tamiflu)
What is the management for influenza?
- rest, warmth, hydration, analgesia
- Anti-viral treatment within 48hrs has some effect on the duration of fever
- Antibiotics not given unless secondary bacterial infection is suspected
What is the prevention for influenza?
killed vaccine (~70% efficacy)
What is SARS?
Severe Acute Respiratory Syndrome
What are the symptoms of SARS?
- High fever
- cough
- Shortness of breath
- CXRs consistent with pneumonia
What is the incubation period of SARS?
2-7 days (max 10 days)
How is SARS transmitted?
via droplets, faeces, infected animals (many modes)
How is SARS identified?
- virus isolation in cell culture
- electron microscopy
- molecular techniques
What type of virus is SARS?
- coronavirus
- enveloped RNA virus
- Characterisitic “halo”
- receotir for spike protein is ACE2
What is the treatment for SARS?
No specific treatment avaliable
- Ribavirin
- Corticosteroids
- Interferons
- Anti-retroviral therapies (protease inhibitors)
Common fungal infections of RT
- Aspergillus fumigatus
- Pneumocystis jiroveci (previously P. carinii)
- AIDS defining condition
Common parasitic infections of RT
- Ascaris
- Strongyloides
- Schistosoma
- Echinococcus granulosus
