Microbiology 8 Respiratory Tract Infections 1 Flashcards
1
Q
Why is the respiratory tract so vulnerable?
A
- it is a mucous membrane that is constantly exposed to the outside environment
2
Q
What are some defences of the respiratory tract?
A
- Nasal hairs
- mucous secretions
- cilia
- cough reflex
- alveolar macrophages
3
Q
What are two examples of pathogens that interfere with ciliary actions?
A
- Bordetella pertussis (whooping cough)
- Mycoplasma pneumoniae
4
Q
How do lower respiratory tract infections differ from upper ones?
A
- they are more severe
- more important
- cause consolidation of the lung
- clinical example: pneumonia
5
Q
What is otitis media?
A
- an infection of the middle ear
6
Q
What causes outbreaks of bronchiolitis?
A
- respiratory syncytial virus
7
Q
What are examples of URTI?
A
- sinusitis
- otitis media
- pharyngitis
- epiglottitis
- laryngitis*
8
Q
How do infections overlap?
A
- URTIs usually become LRTIs
9
Q
Which viruses cause 75% of common cold cases?
A
- rhinovirus
- coronavirus
- adenovirus
10
Q
What are infections linked with the common cold?
A
- pharyngitis
- rhinitis
- sinusitis
- laryngitis
11
Q
Expand on the common cold:
A
- it is a mucosal irritation that causes sneezing and coughing
- these symptoms cause the spread of the virus
- this is very important because they are mechanisms of shedding and transmission
- common colds are a very big trigger to chronic respiratory conditions and other LRTIs
12
Q
What is a viral trigger?
A
- something that causes disruption to the respiratory tract, and then you get colonization and further disease (possibly by bacteria that was already there)
13
Q
How does the common cold progress and spread?
A
- inflammatory virus-rich secretions
- causes sneezing reflex and hand contamination
- leads to binding to host cell
- spread from cell to cell, damage to epithelial cells and inflammatory mediators released
14
Q
Why does the human rhinovirus work best in the URT?
A
- the rhinovirus duplicates best at 34 degrees, which is just below body temperature
- this means that the virus enzymes work best at that temperature
- it is a cold adapted virus
15
Q
Describe Otitis media
A
- it is a middle ear infection
- most common in children
- causes glue ear: difficulty hearing and learning problems
- the tympanic membranes gets inflamed
- it’s a clinical diagnosis because you can’t get a puss sample from the middle ear
16
Q
What viruses causes otitis media and how do you treat it?
A
- streptococcus pneumoniae and haemophilus influenza (as a secondary cause)
- treated with amoxicillin first line
17
Q
Describe sinusitis
A
- all ages
- local tenderness from local accumulation of puss in a sinus
- fever
- no formal microbiological diagnosis - just clinical
18
Q
Which viruses causes sinusitis? How do you treat it?
A
- streptococcus pneumoniae and haemophilus influenza
- you leave it, unless it persists, then you treat it with amoxicillin
19
Q
Describe acute epiglottitis
A
- occurs in young children
- considered a medical emergency
- respiratory obstruction
- if hospitalized, intubation and antibiotics
20
Q
How do you prevent epiglottitis? How do you treat it?
A
- there is a vaccine for haemophilus influenzae capsular type B (gram negative bacillus)
- you treat it with cefotaxime or chloramphicol
21
Q
how can you check for acute epiglottitis?
A
- blood cultures are often positive due to the systemic infection
22
Q
Expand on Mumps
A
- virus that causes parotitis
- it has a respiratory spread
- no specific treatment
- has a vaccine but over the years has become less effective (MMR vaccine)
23
Q
How do you test for mumps?
A
- RT-PCR for mumps RNA in salvia - i.e. buccal swab
- RT-PCR for mums RNA in CSF or urine
- Not done in NI, but you can also check for mumps-specific IGM ab in serum or saliva
24
Q
What are some important resp viruses?
A
- influenza virus
- RSV
- parainfluenza viruses (croup or laryngitis)
- rhinovirus (URTI common cold)
25
Expand on pharyngitis
- Epstein Barr Virus (glandular fever)
- 70% of sore throats are caused by viruses, the rest bacteria
- sore throat and fever
- Streptococcus pyogenes: strep through
- Diphtheria: toxin induced damaged to heart and brain
26
Expand on laryngitis and tracheitis
- common with lots of causes
- croup: laryngotracheobronchitis
cause inspiratory stridor due to laryngeal narrowing
- young children
- caused by parainfluenza viruses 1&2
27
How do you test for Parainfluenza virsues 1&2 and how do you treat them?
- PCR but mostly clinical diagnosis
- paracetamol and loads of fluid
- if severe, corticosteroids
- if hospitalised, adrenaline
28
Infection mononucleosis:
- Epstein Barr Virus
- transmitted through saliva, very cell associated
- teenagers and young adults tend to get it
- babies get asymptomatic infection
- also called glandular fever
- causes a membrane with puss over tonsils
29
How do you treat infectious mononucleosis?
no specific treatment, but steroids can be used if severe
30
What are symptoms of infectious mononucleosis?
- lethargy, sore throat, fever, hepatitis, lymphadenopathy, splenomegaly
- immunologically mediated
31
How do you test for infectious mononucleosis?
- monospot serology test or EBV IgM
| - causes atypical lymphocytes on blood smear
32
What is an example of a complication of infectious mononucleosis?
- encephalitis
33
What happens on a cellular level when infected by the EBV-Herpes family?
- you get cytotoxic t cells which target B cells
- a dysregulation of cytokines which cause flare ups
- white blood cells change causing an elevation of liver enzymes
34
How does streptococcus pyrogenes present?
- pharyngitis and peritonsillar abscess
| - scarlet fever: rheumatic fever, rheumatic heart disease, and acute glomerulonephritis
35
How do you test for streptococcus pyrogenes?
- throat culture
| - anti-streptolysin O titre (ASOT) serology test
36
How do you treat streptococcus pyrogenes?
- penicillin or erythromycin
37
Diphtheria
- caused by corynebacterium diphtheria(gram positive bacillus)
- pharyngeal diphtheria presents with a membrane over the pharynx
- this is important because it releases toxins that can cause fatal hear failure and polyneuritis
- toxins are phage coded
38
How do you treat for diphtheria?
- there is an effective vaccine
| - antitoxin *antibody) + penicillin or eryhtromycin
