L11. Upper Respiratory Tract Infections

Question 1

What is the imaginary cut off between the upper and lower respiratory tracts?

Answer 1

The epiglottis

Question 2

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

Answer 2

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

Question 3

Is any part of the URT sterile?

Answer 3

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

Question 4

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

Answer 4

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.

Question 5

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

Answer 5

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)
C.albicans

Question 6

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

Answer 6

S.pyogenes

Meningicocci

Question 7

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

Answer 7

Enterobacteria
Pseudomonas
C.diptheriae (non-toxigenic)

Question 8

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

Answer 8

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

Question 9

Why is it difficult to diagnosis respiratory diseases?

Answer 9

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.

Question 10

What pathogens are commonly the cause for the common cold?

Answer 10

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

Question 11

What is the pathogenesis of the common cold?

Answer 11

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)
Recovery

Question 12

What is a major consequence of the common cold?

Answer 12

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

Question 13

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

Answer 13

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

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

Question 14

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

Answer 14

10-20% are caused by bacteria

In children 1/3rd are bacterial

Question 15

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

Answer 15

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

Question 16

What is the pathogenesis of sinusitis?

Answer 16

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.

Question 17

What are the major pathogenic causes of otitis media?

Answer 17

Pneumococci
H.influenzae
M.cararrhalis

Question 18

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

Answer 18

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)

Question 19

What are the major pathogenic causes of Epiglottitis

Answer 19

H.influenzae type B

Question 20

Why is it important to distinguish epilgottitis from croup?

Answer 20

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

Question 21

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

Answer 21

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.

Question 22

What are the major pathogenic causes of Croup?

Answer 22

Parainfluenza virus
Influenza A
RSV

Question 23

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

Answer 23

Never required for the common cold

Seldom necessary for all things except pharyngitis (if possible) and epiglottis which is required.

Question 24

Describe the treatments for URT infections (if there are)

Answer 24

Treatments are mostly symptomatic relief Eg. paracetamol.

Antibiotics are administered if the infections are recurrent or severe (or is epiglottitis).

Question 25

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

Answer 25

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

Question 26

What are major viral respiratory tract infections

Answer 26

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