3- microbiology of respiratory tract Flashcards
what are the 3 important components for disease? (another triangle thing)
susceptible host, virulent pathogen, favorable environment = if lack any of these then disease
what are the 6 components of chain of infection? (geography thing)
- susceptible host (elderly, infants, immunocompromised)
- portal of entry (mouth, eyes, cuts)
- mode of transmission (contact, droplets (sneeze, speak, cough))
- portal of exit (mouth, cuts, feces, bodily fluids)
- reservoir (people, animals, water, food, soil)
- agent (bacteria, virus, parasites, funghi)
what is a colonisation?
presence of microbe in human body without inflammatory response
*means doesn’t need antibiotic
what is a bacteraemia?
presence of viable bacteria in blood
what is infection?
inflammation due to viable bacteria in blood
what is sepsis?
dysregulated host response due to infection
what is importance if it says colonies in question?
it’s a trick - make sure to not prescribe antibiotics when colony as colony is just presence of microbe but not actually causing inflammatory response
*unless in immune compromised/CF
what are some common bacteria causing community acquired pneumonia? (from highest incidence to lowest incidence)
- streptococcus pneumoniae = typical
- haemophilus influenzae
- mycoplasma pneumoniae = atypical
- chlamydia pneumoniae = atypical
- legionella species = atypical
what are common hospital acquired pneumonia and Ventilator-Associated Pneumonia?
- staphylococcus aureus
- pseudomonas aeruginosa
- e.coli
*a bunch more in notes but just picked these - ones with more gram negatives
what is common fungal infection in lungs?
aspergillus
what are some common viral infections in adults?
- influenza viruses
- rhinoviruses
- coronavirus
what is involved in diagnosing infections? (sam as like everything else)
- history
- examination
- investigations (radiology, biochemistry, immunology etc)
- tests (blood, stool, urine, wound, tissue cultures)
- serology
what is problem with serology test? why is it not that useful for someone who is acutely ill?
takes a long time for body to form antibodies
what is
a) sinusitis?
b) rhinitis?
c) pharyngitis?
d) epiglottitis?
e) laryngitis?
inflammation of:
a) paranasal sinuses
b) nose
c) pharynx, tonsils, uvula
d) epiglottis, superior larynx
e) larynx
what is the important aspects of inflammation that are good to think about for different locations e.g. pleuritic chest pain, coughing, short of breath, maybe sputum?
calor (heat), rubor (redness), tumor (swelling) , dolor (pain) , functio laesa (loss of function)
how long does blood culture and PCR take? what is the significance of this?
blood test about 2 days and PCR about 6-24 hours but often lab doesn’t run every day so logistics mean maybe only done once or so a week
= means that you can’t just wait until diagnosis before doing something, need to treat as go along and with little bits and pieces your told
what are the key things to do for microbiology?
- identify what particular infection for particular patient
- determine colonisation vs infection for interpreting test results
- identify organism with name & characteristics and with correct tests
- choose treatment - with antibiotic guide & formulation, adverse effects
- prevent infection = vaccines, drugs
what are people have unusual host response?
- old people
- immunosuppressed
- some drugs, genetic
what are characteristics of unusual microbe that make difficult infection?
- virulence expression
- latency – intracellular
- predilection (preference) for certain sites
what are the different classes of beta lactams?
- Penicillin
- Flucloxacillin
- Amoxicillin
- Cephalosporins
- Piperacillin/tazobactam
- carbapenems
does flucloxacillin work for methicillin resistant?
no
why is it bad for people with penicillin allergies?
because it means they might have to use drugs such as quinolones which is bad with lots of bad side effects
= that’s why it’s important to test if actually allergic cause you don’t want to give someone bad drug unless you really need to
what are important things to think about when picking what antibiotic to give?
- dose, route, frequency, cost
- age, body composition
- with food/without food
- if they can access treatment
how many days of antibiotics is suitable?
5 days
what is risk factor clue for question of community acquired penumonia?
smoker
what are clinical symptoms of community acquired pneumonia?
- cough
- increased sputum
- dyspnoea
- chest pain
- fever
what is seen on chest xray in community acquired pneumonia?
chest xray with infiltrates
what is temperature and results found from examination of community acquired pneumonia?
temperature 38.0, left base crackles
what is pathology of community acquired pneumonia?
organism reaches lung → immune activation & infiltration (systemic response) →fluid & cellular build up in alveoli leads impaired gas exchange
what is aspiration pneumonia?
occurs when food or liquid is breathed into the airways or lungs, instead of being swallowed so lots of oral pathogens in wrong way = anaerobes
what are some bugs common in pneumonia in immunosuppressed?
- Pneumocystis jiroveci, Aspergillus sp. , endemic mycoses
- Mycobacterium tuberculosis , non-tuberculous mycobacteria
what tests should be done to help diagnosis of community acquired pneumonia?
- sputum culture
- purulence
- viral PCR
what are risk factors for community acquired pneumonia?
- increasing age
- immunocompromised/suppressed patients
- smoking
who is more likely to have asymptomatic strep?
- child
- also military personal
what are strep pneumoniae virulence factors? what is the main one?
capsule = key virulence factor, basis of where vaccination comes from (capsule also anti-phagocytic)
other virulence factors = surface adhesins, pneumolysin, sIgA protease
what are the different ways streptococcus pneumoniae presents?
- pneumonia is most common presentation
- can also present as otitis media, bacteraemia, meningitis
should you start antibiotics in absence of evidence of bacterial infection?
no
how should you start treatment of strep pneumoniae?
first treatment = empiric therapy
- you take history of relevant allergies
what antibiotic is prescribed for mild to moderate community acquired pneumonia?
amoxicillin - if penicillin allergy doxycycline (tetracycline)
what antibiotic is prescribed for severe community acquired pneumonia?
co-amoxiclav + doxycycline - if penicillin allergy IV levofloxacin (quinolone)
*if in ICU - add clarithromycin
what antibiotic is prescribed for severe hospital acquired pneumonia?
amoxicillin + metronidazole + gentamicin (aminoglycoside)
- if penicillin allergy, co-trimoxazole, metronidazole, gentamicin
what antibiotic is prescribed for non-severe hospital acquired pneumonia?
amoxicillin + metronidazole
- if penicillin allergy = co-trimoxazole + metronidazole
what are the 4C antibiotics?
- ciprofloxacin (fluoroquinolone)
- clindamycin
- cephalosporin
- co-amoxiclav
what is invasive pneumococcal disease?
a group of illnesses caused by pneumococcus bacteria e.g. meningitis & bacteraemia
when should you add vancomycin?
if recent travel to country with high rates of penicillin resistant pneumococci
how can pneumonia infection cause empyema?
accumulation of infected liquid can breach the lung and get within body cavity especially pleural space causing empyema
what is recent holiday to foreign country in history a hint for?
legionella pneumonia - can test with legionella urinary antigen (detects serogroup 1 only)
what tests should be done for legionella pneumonia?
- PCR from sputum
- legionella urinary antigen
- culture
what is treatment of legionella pneumonia?
clarythromycin or erythromoycin
and if needed (but very last resort) quinolones e.g. levofloxacin
is legionella gram negative or gram positive?
gram negative
where is legionella?
in moderately warm water - why back from travel is a clue
how is legionella transmitted?
Transmitted by inhalation of contaminated water droplets
what are symptoms of legionella?
severe flu and can include fever, chills, loss of appetite, headache, lethargy
what are typical symptoms of mycoplasma pneumonia?
typically young student, aches & pains, feels rubbish, headache, noticed a rash (all sorts of rashes), non productive cough, often self limiting
what are the main diagnostic tests in legionella?
- culture
- urinary antigen test
- nucleic acid-based detection
from different places - respiratory tract specimens, blood, urine
what is treatment of mycoplasma pneumonia?
= has no cell wall →amoxicillin NOT treatment of choice
- clarithromycin and if not ciprofloxacin
when does staphylococcus aureus pneumonia occur?
post influenza - spreads haematogenous (lymphatic spread)
what is the drug of choice for staphylococcus aureus pneumonia?
co-trimoxazole then doxycycline
what is whooping cough (pertussis)?
- Acute tracheo-bronchitis
- cold-like symptoms and paroxysmal coughing for two weeks
- repeated violent exhalations with severe inspiratory whoop, vomiting common
- residual cough for month or more, infectious in first fortnight and then not infectious
what is bacteria causing whooping cough?
bordetella pertussis = gram negative coccolbacillus
what antibiotic should be given for someone presenting with acute bronchitis - infection & inflammation of bronchi, productive cough, wheeze and normal chest examination & x-ray?
NO ANTIBIOTICS = trick - when normal chest examination + chest x-ray shouldn’t give antibiotics
does every COPD examination need antibiotics?
no
can resistance spread?
when encountered resistance - bacteria chat to each other and swap resistance elements so more likely to get resistance to lots of things (many mechanisms)
what are some viruses which cause pneumonias?
influenza, RSV (respiratory syncytial virus), adenovirus (in transplant patients), corona virus, measles
what are examples of evasion?
- hide in neurons and non-neuronal cells
- bukholderia pseudomallei can emerge many years later
- leishmania can interfere with IL-12 transmission
= not too important to know details, just idea
who are more vulnerable to aspergillus?
people who’ve had transplant or chemo more vulnerable or HIV infection
what is aspergillus?
fungus that can cause pneumonia
what cells are involved in bacterial infection?
dependant on antibodies so needs phagocytes + neutrophils to clear things and B cells to make the antibodies
what cells are involved in virus infections?
managed by T lymphocytes mainly - also antibodies + B lymphocytes important for detection but clearance is purely T lymphocyte
what cells are involved in fungal infections?
needs phagocytosis to clear so eosinophil and T lymphocytes (mainly) so predisposed if not phagocyte function or T lymphocytes (chemo + HIV more susceptible)
