L11. Upper Respiratory Tract Infections Flashcards Preview

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Flashcards in L11. Upper Respiratory Tract Infections Deck (26)
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What is the imaginary cut off between the upper and lower respiratory tracts?

The epiglottis


Both the URT and the LRT contain an abundance of normal microbiota. True of False? Explain

The URT does have an abundance of normal microbiota while the LRT is relatively sterile. This is because the defenses of the URT are good at keeping particulate and infectious away from the LRT


Is any part of the URT sterile?

There are two components of the URT that are relatively sterile compared to the rest of it: middle ear and the paranasal sinuses.


What kind of microbiota (anaerobic or aerobic) make up the URT? Why is this?

Generally, the anareobic bacteria outnumber the aerobic bacteria 10:1 in the URT. This is because anaerobic bacteria are able to form niche environments in areas like in the gums, the saliva, tooth surfaces and between the teeth.


What are some common (>50%) pathogens of the URT in healthy people?

viridans streptococci
H. influenzae (non-typable)
Nisseria spp.
Gram negative anaerobes make up the majority
Corynebacterium spp.
S.pnuemoniae (variable between different ages and populations)


What are some occasional (1-10%) pathogens of the URT in healthy people?



What are some Uncommon (<1%) pathogens of the URT in healthy people?

C.diptheriae (non-toxigenic)


What bacteria are able to reside in latent states in the respiratory tract?

P.jurovecii (carini): pneumocystis pneumoniae (an AIDs defining illness)
CMV, HSV, EBV (in lymph nodes and sensory ganglia)


Why is it difficult to diagnosis respiratory diseases?

Because there are several syndromes which can have multiple different causes (bacterial or viral) each with different pathogens. Pathogens themselves, are able to cause different respiratory syndromes.


What pathogens are commonly the cause for the common cold?

parainfluenza virus
coronavirus (more common in adults than children)
human metapnuemovirus (HMPV)


What is the pathogenesis of the common cold?

Virus attaches, absorbes and multiples eventually killing the epithelial cells (host defenses are activated at this stage)
Virus spreads out to the fluid and to infect other cells (person is highly infectious at this stage)
Inflammation increases and phagocytes come into engulf debris (this leads to low-grade overgrowth of bacterial commensals)


What is a major consequence of the common cold?

Can predispose to a secondary infection which can potentially lead to pneumonia


What are the major pathogens involved in Pharyngitis and Tonsilitis? (Sore throat syndrome)

Adenovirus, Enterovirus, Parainfluenza (with nasal involvement) and Influenza

Without nasal involvement: adenovirus, influenza, enterovirus, reovirus, S.pyogenes, Strep groups C and G


What is the trend for pathogens causing Sore Throat Syndrome? In terms of bacterial vs. viral and how this is different in young children?

10-20% are caused by bacteria
In children 1/3rd are bacterial


What are the major pathogenic causes of Sinusitis? (Primary and Secondary)

Primary: Viral
Secondary: H. influenzae, S.pnuemoniae


What is the pathogenesis of sinusitis?

Viruses are able to spread across the epithelia and through tubes connecting to the paranasal sinuses. In the mucosa, the epithelial cells are damaged leading to high bacterial susceptibility.


What are the major pathogenic causes of otitis media?



What is the pathogenesis of otitis media? Why is it more common in children?

Secondary to nasal, URT infection via spread through the eustacian tube.It is more common in children because they have horizontal tubes anatomically (less easily drained)


What are the major pathogenic causes of Epiglottitis

H.influenzae type B


Why is it important to distinguish epilgottitis from croup?

Because epilgottitis can be potentially fatal and requires urgent diagnosis and treatment


Can throat swabs be made to diagnose epiglottitis? Why or why not?

No. You must avoid at all costs touching the epiglottis because this will aggravate the situation and make it worse causing suffocation and death of the patient. Instead diagnosis is done by Xray analysis or blood culture if a systemic infection is suspected.


What are the major pathogenic causes of Croup?

Parainfluenza virus
Influenza A


For what respiratory syndromes is it necessary to do laboratory diagnoses? Why or why not?

Never required for the common cold
Seldom necessary for all things except pharyngitis (if possible) and epiglottis which is required.


Describe the treatments for URT infections (if there are)

Treatments are mostly symptomatic relief Eg. paracetamol.
Antibiotics are administered if the infections are recurrent or severe (or is epiglottitis).


Why is it not useful to give antibiotics to viral infections? Despite them being prophylactic for secondary infections?

Because they are viruses.
There is no evidence that suggests treatment with antibacterials prevents secondary bacterial infections due to virus predisposition.


What are major viral respiratory tract infections

Common cold, sore throat, sinusitis, laryngitis, croup, acute bronchitis, influenza