M103 T4 L8 Flashcards
What are features of the Legionella pneumophila bacteria?
thin aerobic flagellated non-spore-forming Gram-negative
What is unusual about the coating on Mycobacterium tuberculosis bacteria? What causes it?
is unusual and waxy
primarily due to the presence of mycolic acid
What are the symptoms of parainfluenza virus?
fever
runny nose
cough
What are the two main parts of the respiratory tract?
the upper respiratory tract
the lower respiratory tract
Why have we divided the respiratory tract into two main parts?
conditions in each part present differently to each other
different consequences in terms of morbidity and mortality
investigated and treated differently
What are the four functions of alveolar macrophages?
to secrete anti-microbial peptides
to engulf and kill pathogens
to recruit other immune cells
to process and present antigens to T cells
What secretes IgA?
plasma cells
Which atby is most commonly produced?
IgA
How does IgA help to enable immune function in the mucous membranes?
IgA secretions form an additional epithelial protective barrier
How does the additional epithelial protective barrier formed by IgA help to protect the cell?
prevents microbial adherence to the epithelial surface
inhibits certain viral infections by interfering with their assembling processes.
binds to pathogens causing phagocytosis
provides atby dependent, cell mediated cytotoxicity
What material is the mucosa made up of?
consists of one or more layers of epithelial cells
overlying a layer of loose connective tissue
What are the five things that the alveolar spaces fill up with when the lungs experience inflammation?
exudate pus cells debris dead bacteria dead viruses
Why does inflammation in the lungs cause a loss of function?
the alveolar spaces fill up with different cells / matter
stops the alveolar spaces from being filled with air anymore
How does inflammation in the lungs cause pain?
there is no real pain sensation in the lungs themselves
the pain comes the outside of the lungs - pleuritic pain
What is pleuritic pain caused by?
inflammation causes swelling and sensitivity
the outside of the lung is inflamed with the infection below it
rub together
the friction causes pleuritic pain
During swelling, what is the effect of the alveolar walls becoming thicker than normal?
it impedes that gas transfer
What are the three causes of swelling on a microscopic level?
vasodilation
increased vascular permeability
inflammatory cell infiltration
Why does part of the lungs sometimes become lighter in colour during swelling? Why is this a problem?
because that part of the lung is full of pus
if the lighter section were to be squeezed, it would be really hard and solid
this means that this part of the lungs no longer has its usual squidgy air sponge anymore
What is a Pulmonary abscess caused by?
when a bit of dead / necrotic lung has died away and there is a pus filled abscess within that
How long is the incubation period for rhinoviruses?
incubation: 2 - 3
How long can symptoms last for rhinoviruses?
usually 3 - 10 days
it can be up to two weeks in 25 % of patients
What happens if bradykinin is administered internasally?
causes a sore throat
causes nasal congestion
How is sneezing mediated?
histamines are released
the trigeminal nerves are stimulated sensorily
When does nasal discharge change colour?
when there are increasing numbers of neutrophils due to myeloperoxidase
What are the changing colours of nasal discharge due to myeloperoxidase?
white
yellow
green
What nerve mediates coughing?
the vagus nerve
What condition needs to be met for a cough to start?
any inflammation has to extend as far as the larynx to trigger coughing
What substance is responsible for systemic symptoms such as fever?
Cytokines
What is the difference between how fast symptoms appear for the cold compared to for the flu?
cold - appears gradually
flu - within a few hours
What is the difference between what areas of the body the cold affects compared to for the flu?
cold - affects mainly your nose and throat
flu - affects more than just your nose and throat
What is the difference between how the cold makes people feel compared to for the flu?
cold - feel unwell but okay to carry on as normal
flu - feel exhausted and too unwell to carry on as normal
What is the difference between how the cold and the flu in terms of fevers?
cold - usually no fever
flu - high fevers, may have lower respiratory tract features as well
What two viruses is influenza caused by?
Influenza A virus
Influenza B virus
How long is the incubation period for uncomplicated influenza?
1-4 days
What are the symptoms of uncomplicated influenza?
abrupt onset of cough and fever headache, sore throat, nasal discharge myalgia malaise acute debilitation otherwise examination often unremarkable
What is the temperature range for a fever caused by uncomplicated influenza?
38 - 41 oC
What are the risk factors for influenza?
Immunosuppression chronic medical conditions pregnancy / 2 weeks postpartum Age <2y or >65y (young or old) BMI >40
What are the complications for influenza?
1o viral or 2o bacterial pneumonia
CNS disease
Death
What is the estimated mortality rateamong people infected withinfluenzain the US?
about 0.13percent
What is the function of the influenza virus haemagglutinin surface protein?
binds sialic acids on cell surface glycoproteins
binds glycolipids in the respiratory tract
AAR allows the influenza virus to enter the cell
What is the function of neuraminidase on the surface of the influenza virus?
allows the virus to escape by cleaving sialic acid bonds
so that the escaping virions won’t all clump together
What features do the genome on influenza virus have?
a segmented genome consisting of 8 parts
can be reassorted if two different viruses infect the same cell (the genetic material will mix)
What is the difference between antigenic shift and antigenic drift?
shift - whole segment switch
drift - many small point mutations
How does antigenic drift work?
when RNA viruses are a little bit careless about how they replicate
causes little point by point mutations each time they replicate
over time, it just slowly changes what sitting on the outside of the virus
neutralising atbys used to block binding fo the virus to cells
however, mutations can alter the haemagglutinin epitopes enough so that neutralising atby no longer binds
What are the options for treatment and prevention of influenza?
hand hygiene
droplet precautions (spreads by droplets)
active immunisation
What does active immunisation treatment for influenza work against?
haemagglutinin components
neuraminidase components
What are the symptoms of pneumonia?
Fever (cytokines)
breathlessness (alveoli full of matter)
cough (trying to cough up alveolar content)
sputum production (mucociliary escalator tries to get rid of alveolar content in the trachea)
Hypoxia - increased respiratory rate
Pleuritic chest pain
Sepsis
Radiologically, what does a diagnosis of pneumonia require?
infiltrates on a plain CXR with supporting clinical features
Why can the heart borders or diaphragm become obscured on CXRs?
due to loss of solid-gas interface
the alveoli and bronchioles are completely filled with inflammatory debrision, so they look solid
what usually is solid next to gas is now solid next to solid
What are the three types of classification for pneunomia?
Typical versus atypical *lecturer said not helpful
Lobar versus bronchopneumonia *
Community versus hospital-acquired
Why is the pneunomia classification Community / hospital-acquired the most useful classification?
the pathogens involved differ in their % contribution
so it alters their management
What are the Community-acquired pneumonia pathogens?
Streptococcus pneumoniae Haemophilus influenzae Mycoplasma pneumoniae Legionella pneumophila Staphylococcus aureus
What proportion of pneumonias are caused by respiratory viruses?
about a third
Why are all pneumonias treated with antibiotics even though a third are viral?
it’s really hard to tell whether it’s whether bacteria or viruses are causing the pneumonia most of the time
What is the most common organism overall?
Streptococcus pneumoniae
What are the risk factors of Streptococcus pneumoniae?
alcoholism respiratory disease smoking hyposplenism chronic heart disease HIV – 50- to 100-fold increase in invasive pneumococcal disease in HIV+
What type of bacteria is Streptococcus pneumoniae?
Gram positive cocci
How is Streptococcus pneumoniae prevented and how is it treated?
prevented - vaccine
treated - penicillin
Where is Streptococcus pneumoniae acquired?
in the nasopharynx
What proportion of people with Streptococcus pneumoniae are asymptomatic carriers?
40-50%
What is the most common cause of atypical pneumonia?
Mycoplasma pneumoniae
How does atypical pneumonia usually present?
young patient
with a vague constitutional upset
lasts for several weeks
extrapulmonary symptoms very common
Why is atypical pneumonia penicillin resistant?
it lacks a cell wall
penicillins need a cell wall to work on
Why can’t atypical pneumonia be diagnosed in the usual way in a lab?
it lacks a cell wall
so it cannot grow on normal lab plates
How is atypical pneumonia diagnosed?
by PCR of throat swab (VTS)
involves looking for the genome rather than trying to grow it
How is atypical pneumonia treated?
macrolides or tetracyclines
In which two ways can Legionella pneumophila occur?
as sporadic infection
in outbreaks associated with a contaminated water source (consider travel and nosocomial acquisition)
What is a potential effect of Legionella pneumophila?
Can cause severe, life threatening infection
How common is Legionella pneumophila?
350 cases/year in E&W
How is Legionella pneumophila diagnosed?
doesn’t grow on routine culture – need special conditions, and longer
Urinary legionella antigens - urine is tested for L.p antigens using a lateral flow assay
How is Legionella pneumophila treated?
macrolides or quinolones
What are the risk factors of Legionella pneumophila?
smoking
chronic lung disease
What condition has to be met for it to be Healthcare-associated pneumonia?
has to have onset at least more than 48 hours since admission
How do patients catch Healthcare-associated pneumonia?
Hospitalised patients become colonised
with hospital bacteria the longer they stay
they may either be intrinsically more resistant to antibiotics, or have acquired resistance mechanisms.
these organisms then develop into pneumonia
How is Healthcare-associated pneumonia treated?
a broader spectrum antibiotics are used instead
What are the social risk factors for pneumonia?
Current EtOH misuse
Current or hx of drug misuse
Homelessness
Imprisonment
What are the risk factors for pneumonia?
More pulmonary disease
Higher MDR rates
Poorer treater completion rates
Poorer outcomes even in drug sensitive TB
How often does Aerobic bacillus divide?
every 16-20 hours
very slowly
Why doesn’t Aerobic bacillus stain strongly with Gram stain?
it has a cell wall, but it lacks the PPLPD outer membrane
Why is Aerobic bacillus referred to as acid fast bacillus (AFB)?
it retains the gram stain after treatment with acid
any other bacteria that (stain) will wash away
(weakly positive)
Which two special stains are used for Aerobic bacillus?
Ziehl-Neelsen
auramine-rhodamine
What are the six steps by which TB infection occurs?
Inhalation Inflammatory cells bacterial dissemination dendritic cell presentation immune system cells granulomas
What happens during the inhalation stage of TB infection?
Infection initiated by the inhalation of aerosol droplets that contain bacteria
Where are inflammatory cells recruited to during a TB infection?
to the lung
Where does bacterial dissemination occur?
disseminates to the draining lymph node
What happens after the bacterial dissemination stage?
the dendritic cell presentation of bacterial antigens
What happens after the bacterial antigen stage?
leads to T cell priming and triggers an expansion of antigen-specific T cells, which are recruited to the lung.
Which cells are recruited in a TB infection?
T cells
B cells
activated macrophages
other leukocytes
What leads to the establishment of granulomas?
immune cells being recruited to the lungs
What do granulomas contain?
Mycobacterium tuberculosis
Where are the droplets containing TB bacteria deposited after entering the body?
in terminal airspaces in the lungs
What is the role of the alveolar macrophages?
they ingest bacilli in the terminal airspaces of the lungs
they recruit more macrophages
How are the TB bacteria able to survive once ingested by the macrophages?
they are able to replicate within the endosome of the macrophages
so they survive inside them rather than being killed off
After ingestion by macrophage, where are the TB bacteria transported to?
the regional lymph nodes
What could happen to the TB bacteria in the regional lymph nodes?
they might be killed off entirely
they might be walled off in granulomas
How does granuloma formation occur?
the TB bacteria in the regional lymph nodes trigger T cell priming and an expansion of antigen specific T cells which are recruited to the lungs
the activated macrophages establish granulomas, which then wall off any remaining bacilli
Is granuloma formation an effective immune strategy for protecting from TB?
yes - this contains the infection in about 90% of individuals
What happens to TB bacteria inside granulomas?
might become calcified and completely killed off in the granulomas - infection eradicated
might start multiplying and become primary TB
might control it - have live but dormant mycobacteria within an active granuloma
What are the consequences for a patient with dormant mycobacteria within a granuloma?
patient is asymptomatic
at a later stage, it might reactivate and disseminate
this occurs in about 10% of individuals
What are the features of latent TB?
Dormant bacilli
Contained by host defences
Non-infectious
Asymptomatic
What are the features of active TB?
Actively replicating bacilli
May be infectious (site-dependent)
Symptomatic (site-dependent)
How can active TB be diagnosed?
by isolating acid fast bacilli
by growing Mycobacterium tuberculosis
by demonstrating its presence by conducting a PCR and finding the presence of the MTB genome in the sample
How can latent TB be diagnosed?
by demonstrating the hosts’ immune response
What are the aims for managing TB?
cure active disease
reduce spread
prevent reactivation
How is TB managed?
prompt and adequate treatment;
appropriate source isolation by contact tracing
What types of infections are commonly caused by gram negative bacteria?
pneumonia, bloodstream infections
wound or surgical site infections
meningitis in healthcare settings
Are Gram-negative bacteria easily treatable?
no bc they are resistant to multiple drugs and are increasingly resistant to most available antibiotics
What does a Gram stain test involve?
Gram stain test, these organisms yield a positive result. a chemical dye which stains Gram +ve bacteria cell walls purple and Gram -ve bact pink, as their cell walls don’t hold the dye
