75 - URT Infections Flashcards
Parts of resp tract with normal microbiota
Paranasal sinuses
Examples of potentially pathogenic bacteria present in ~50% of normal resp tracts
Viridans strep (greening), neisseria spp, corynebacterium spp, G- anaerobes, H influenzae (often without identifiable capsule), C albicans, strep pneumoniae
Examples of potentially-harmful bacteria present in resp tract of healthy people 1-10% of time
Strep pyogenes, meningococci
Uncommon potentially-harmful bacteria in resp system of healthy people
Enterobacteria, pseudomonas, C. diphtheriae
Residents of healthy resp system in latent state
In lung: P. jirovecii, M. tuberculosis
In lymph nodes, sensory nerves: CMV, HSV, EBV
Effect of diphtheria vaccination on rare diphtheria cases
Some rare, non-toxigenic infections of diphtheria, presenting as things like infective endocarditis.
Vaccine is a diphtheria toxoid, so evolutionary advantage to being diphtheriatoxin negative.
PCP
Pneumocystis pneumonia (pneumocystic jirovecii)
Why might P. jirovecii be an AIDS-defining illness?
Normally controlled with adaptive immunity, perhaps some in body after a mild infection.
When cell-mediated immunity is impaired, becomes a serious infection
Places in the mouth that bacteria can be found 1 2 3 4
1) Nasal washings
2) Saliva
3) Tooth surfaces
4) Gingival scrapings
Are there more anaerobic or aerobic bacteria in the mouth?
More anaerobic
URT syndromes 1 2 3 4 5 6
Common cold Pharyngitis/tonsilitis Sinusitis Otitis media Epiglottitis Croup (laryngotracheobronchitis, LTB)
What can rhinoviruses cause?
Rhinitis, sometimes pharyngitis
What can parainfluenzaviruses cause?
Rhinitis, pharyngitis, laryngitis, tracheitis.
Rarely bronchitis, bronchiolitis, pneumonia
What can H. influenzae cause?
Rhinitis, laryngitis, tracheitis, bronchitis, bronchiolitis, pneumonia
Frequent aetiological agents of the common cold
Rhinovirus Parainfluenzavirus RSV Enterovirus Coronavirus Human metapneumovirus
Immunity to rhinovirus
About 100 different serotypes.
Imperfect immunity
What can influenzavirus cause?
Rhinitis Pharyngitis Laryngitis Tracheitis Bronchitis Bronchiolitis Pneumonia
What can pertissis cause?
Laryngitis, tracheitis, bronchitis, bronchiolitis, pneumonia
Effect of cold on resp tract infections
No effect on catching rhinovirus, but if you’re already infected can increase likelihood of pneumonia (cold air might inhibit mucociliary elevator)
What can RSV cause?
Rhinitis, bronchitis, bronchiolitis, pneumonia
Aetiological agents of pharyngitis/tonsilitis (with nasal involvement)
Adenovirus, enterovirus, parainfluenzavirus, influenzavirus
When are tonsilectomies performed now?
Only when there is a chronic infection of the tonsils
What does nasal involvement with an URT imply?
Often viral infection if there is nasal involvement
Aetiological agents of pharyngitis/tonsilitis (without nasal involvement)
Adenovirus, enterovirus, reovirus, influenza.
S. pyogenes, Strep groups C and G
Proportion of URT caused by bacteria versus viruses
~10-20% are bacterial.
This is higher in children (~1/3 are bacterial in children)
Clinical criteria to distinguish between viral and bacterial URT
Age (children more likely to get bacterial infections)
Rash (if rash is present, bacterial)
Very hard to tell the difference normally.
Effect of treating patient with amoxycillin who has EBV
Rash, so can be labelled as allergic to penicillin.
From mild toxicity.
Only occurs with active EBV (no rash with latent)
Aetiological agents of sinusitis
Primary: Viral (part of common cold syndrome)
Secondary: H. influenzae, S. pneumoniae
Secondary bacterial invasion of sinuses
After a viral infection, mucociliary elevator can be impaired.
Normal commensal bacteria can invade sinuses (H. influenzae, S. pneumoniae
Common childhood URT infection
Otitis media (shorter, straighter otitis media)
Frequent aetiological agents of otitis media
Pneumococci, H. influenzae, Moraxella catarrhalis.
Common cause of otitis media
Secondary bacterial infection with commensal flora
Frequent aetiological agent of epiglottitis
H. influenzae type B (not so much anymore, as there is a good HiB vaccine)
Important URTs to be able to distinguish between
Croup and epiglottitis.
Croup is harmless, epiglottitis is potentially lethal
Which aspect of a URT viral infection impairs mucociliary elevator?
Virus lyses infected epithelial cells, which are ciliated.
Visual symptom of otitis media
Bulging, inflamed tympanic membrane
URTIs which are good to diagnose with lab
Pharyngitis/tonsillitis if possible
Epiglottitis whenever possible (epiglottitis is rare)
URTIs what don’t need a lab diagnosis
Common cold. Sinusitis (seldom necessary) Otitis media (seldom necessary) Croup (seldom necessary)
How to diagnose epiglottitis
Without touching epiglottis.
Epiglottis is very inflamed in epiglottitis, and touching it makes it worse, increases risk of suffocation.
Diagnose radiologically and with a blood culture (it is a systemic infection)
What does presence of follicles in tonsillitis tell you?
Nothing.
Appearance of mononucleosis in someone’s mouth
White membrane over pharynx
What’s the cause of herpangina
Coxsackievirus.
NOT herpesvirus.
Cause of hand, foot and mouth disease
Enterovirus (Coxsackievirus A16)
Most important enterovirus
Poliovirus
URTI treatment
Mostly supportive
Why shouldn’t you give aspirin with a cold?
Aspirin is slightly immunosuppressive, increases risk of transmission
When is pharyngitis/tonsillitis treated?
When bacterial. Treat to prevent complications
Examples of possible complications with group A Strep pharyngitis/tonsillitis
Invasive complications with group A strep
Quinsy (peritonsillar abscess)
Autoimmune complications (rheumatic endocarditis)
Susceptibility of group A strep
100% susceptibility to penicillin G (no sign of developing resistance)
When is sinusitis treated?
If very severe
When is otitis media treated?
In under two years old, of if infection is prolonged and severe.
When is epiglottitis treated?
Always
