Community Based Medicine - Common microorganisms in upper respiratory tract infections Flashcards
Common cold, pharyngitis (tonsilitis/quinsy), acute sinusitis, acute epiglottitis
The respiratory tract is the most common site of
infection by pathogens because its:
- In direct contact with the physical/outer environment
- Exposed to airborne microbes
The most pathogenic bacteria have developed
mechanisms to protect themselves:
- A capsule that inhibits phagocytosis
- Intracellular invasion of cells lining the
- respiratory tract or alveolar macrophages to
- escape the immune system
All surfaces of the respiratory tract are colonised by the
host microbiota:
- Inhabitants of the respiratory tract and rarely, if ever,
- cause disease
- Most come from the oropharynx
Two main functions:
- Compete with pathogenic organisms for potential
attachment sites
- Produce substances that are bactericidal and
prevent infection by pathogen
The common cold?
- Common microbe: Rhinoviruses are the main culprit (>80 strains exist). 1 - 4 day incubation
- Characteristic symptoms: A self-limiting nasal discharge becoming mucopurulent over a few days
- Complications: otitis media (6% of children), pneumonia, febrile convulsion
- Treatment: Avoid treatment. If nasal obstructions in infants 0.9% saline nose drops
Pharyngitis/Tonsilitis/Quinsy
- Pharyngitis: Inflammation of the pharynx
- Tonsillitis: Inflammation of the tonsils
- Quinsy: A peritonsillar abscess as a complication of tonsillitis
Common causative organisms:
Pharyngitis/tonsillitis Pharyngitis/tonsillitis
Mostly respiratory viruses:
Group A β-haemolytic streptococcus
Group C & G β-haemolytic streptococcus
Quinsy
Often polymicrobial
Group A
β-haemolytic Streptococcus
Staphylococcus aureus
Anaerobes
Haemophilus Infleunzae
Respiratory syncytial virus
Bronchiolitis
Parainfluenza Virus?
Croup
Rhinovirus?
Common Cold
Influenza virus?
The most common cause of community-acquired pneumonia
Haemophilus influenzae?
Community-acquired pneumonia
Most common cause of bronchiectasis exacerbations
Acute epiglottitis
Staphylococcusaureus
Pneumonia, particularly following influenza
Mycoplasma pneumoniae
- Atypical pneumonia
- Flu-like symptoms classically precede a dry cough.
- Complications include haemolytic anaemia and erythema multiforme
Legionella pneumophilia
- Atypical pneumonia
- Classically spread by air-conditioning systems, causes dry cough.
- Lymphopenia, deranged liver function tests and hyponatraemia may be seen
Pneumocystis jiroveci
- Common cause of pneumonia in HIV patients.
- Typically patients have few chest signs and develop exertional dyspnoea
Mycobacterium tuberculosis
- Causes tuberculosis.
- A wide range of presentations from asymptomatic to disseminated disease are possible.
- Cough, night sweats and weight loss may be seen
Treatment
Pharyngitis/Tonsilitis
- Group A,C&G Streptococcus - Ist Line Penicillin V 500mgs QDS
- OR if not taking orally, Benzylpenicillin 1.2g ODS IV
- If penicillin allergy - Clarithromycin 500mg BD PO (or IV if not taking orally)
- 10 days for group A Streptococcus
- 5 days for groups C&G streptococcus
Treatment
Quinsey
- 1st line - Benzylpenicllin 1.2g QDS IV Plus Metronidazole 500mg TDS IV
- if allergic to penicillin- Clarithromycin 500mg BD IV Plus Metronidazol 500mg TDS IV
- Oral switch of Benzylpenicillin is penicillin V 500mg QDS
- 5-7 days course
Acute Sinusitis:
inflammation of the paranasal sinuses with concurrent inflammation of the nasal cavity
Commons causative organism
- Mostly respiratory viruses
- Streptococcus pneumoniae
- Haemophilus influenzae
- Moraxella catarrhalis
Microbiological investigations
- Nasal swabs are NOT recommended
- Sinus aspirate ONLY for recurrent or
- persistent infection
- Blood cultures (if systemically unwell
Treatment:
- Topical treatment with 1% ephedrine drops and nasal douching may allow drainage of sinuses with mild disease without the need for antibiotics.
- In chronic cases, topic steroid sprays are the mainstay of management with antibiotics reserved for acute flare up
Acute sinusitis
- Moderate/severe disease - 1st - Amoxicillin 500mg-1g TDS po (5-7days)
- Penicillin allergy - Clarithromycin 500mg BD po/Doxycycline 200mg stat then
Acute Epiglottitis and supraglottitis
- Inflammation of the epiglottis and supraglottic structures
- Potential for life-threatening airway obstruction
- History a disease of children beofe the introduction of Hib vaccine but now
- prevalent in adults.
- ENT review is essential
Common causative organisms
- Haemophilus influenzae (type B)
- Streptococcus pneumoniae
- Staphylococcus aureus
- Group A β-haemolytic streptococcus
Microbiological investigations
- Blood culture
- Epiglottal swab ONLY in intubated patients
Treatment: airway management is vital
