Spectrum of Respiratory Pathogens Flashcards
Define the terms pathogen, virulence and infection and describe the types of infection
Pathogen: An organism capable of causing harm. An agent of disease.
Virulence: The strength of the ability of an organism to cause harm. Defined by the number of organisms required to cause disease, capability to overcome host barriers and status of host immune defences.
Infection: Colonisation of an organism where it is not normally found/should be found
Opportunistic infection: May infect those who are immunocompromised.
Describe how microbes gain access to the body and how they cause damage.
Access is gained through overcoming host barriers and defences. This may be through breaks in the skin, through ingestion, invasive procedures, sexual transmission, bites, inhalation.
How they cause damage: Release of endo/exo toxins, release enzymes for the breakdown of host tissues, induce immune responses (inc. inflammation), modify host
Describe how microbes fool the bodies defence mechanisms and how they are transmitted
- Rapidly entering cells
- Latency
- Altering antigens
- Hiding within cells
- Evading macrophages
- Tough outer capsule
- ‘Cloaking’ in host protein
Describe the pathogenic traits of bacteria
- Host mimicry
- Exotoxins (secreted) and endotoxins (released upon lysis)
- Antigenic variation
- Absence of tissue damage (no inflammation)
Bacteria overview
Morphology: Bacilli (Rod), cocci (round), spirochetes (spiral)
Cell wall: Provides shape and protection
Describe the defence mechanisms employed by the respiratory tract
- Mucus: Allows trapping of bacteria, dirt etc. Preventing it from reaching the lungs.
- Cilia: Mucociliary elevator allows movement of mucus upwards for excretion
- Cough: Encourages removal of mucus
- IgM and IgG: Present in the alveolar lining fluid
- IgA: Secreted in the URT
- Phagocytosis: Removes pathogens (dust cells)
Name the main types of URTIs and describe their symptoms
Otitis: Pain, temperature, irritability, discharge, headache, toothache
Sinusitis: Facial pain, nasal obstruction and discharge
Tonsillitis: Lymphedema, temperature, difficulty breathing, enlarged tonsils
Rhinitis (cold, coryza): Rhinorrhoea, sneezing, pharyngitis (sore throat) (Minimal systemic symptoms)
Pharyngitis: Sore throat, erythema of the pharynx, tonsil enlargement
Acute epiglottitis: Pyrexia, sore throat, laryngitis, painful dysphasia, airway obstruction can develop
Acute laryngitis: Hoarseness of loss of voice
Name the main types of LRTI and describe their symptoms
Bronchitis: Productive cough, wheezing, shortness of breath, chest discomfort.
Pneumonia: Productive/dry cough, chest pain, fever, severe difficulty breathing (build up of fluid - blood, mucus)
Bronchiolitis: Cough, wheeze, shortness of breath (1-2 days)
Name some examples of the common non-viral pathogens associated with upper and lower RTIs and describe some of their specific hallmarks and symptoms
- Streptococcus pyogenes
Group A: Gram +ive, non-motile or spore forming
One of the most common human pathogens
Can inhibit phagocytosis and disrupt the immune system.
Attach to and evade the mucosa of the respiratory tract
5-15 % carry the bacteria asymptomatically
Name some examples of the common non-viral pathogens associated with upper and lower RTIs and describe some of their specific hallmarks and symptoms
- Scarlet fever
Caused by: Group A Streptococci
Symptoms: Pyrexia, lymphadenopathy, aches, nausea
Most common in children, 5 - 15 years
Rough red rash seen 12-72 hours after the fever starts, spreads to the entire body
Name some examples of the common non-viral pathogens associated with upper and lower RTIs and describe some of their specific hallmarks and symptoms
- Diptheria
Caused by: Cornyebacterium diphtheria (gram +ive, aerobic, bacilli)
Symptoms: Severe pharyngitis, trachea covered, respiratory distress. Death from multisystem toxaemia and myocarditis
