Microbiology Flashcards
what is an infection pathologically
inflammation due to a pathogen/infectious agent
describe colonisation
the presence of a microorganism, doesn’t always mean infection
what does colonisation mean for swap tests of infected patients
disease might not be caused by bugs found
what it a paired sera test
two separated blood test to show rise in antibodies
what determines the choice of treatment
when the microorganism has a cell wall (B-lactam?)
how are some infections prevented
vaccination
what are the conducting airways consisted of
trachea and bronchus
what are the upper resp. tract components
oropharynx, nasopharynx
what are the host defences against infection in the nasopharynx
nasal hairs, ciliated epithelia, IgA
what are the host defences against infection in the oropharynx
saliva, sloughing, cough
how does mucous prevent infection
traps pathogens
what is a rhinitis infection inflammation of?
the nose
give 3 examples of upper respiratory colonisers that are gram positive
alpha-haemolytic streptococci (strep. pneumoniae), beta-haemolytic streptococci (strep. pyogenes), staphylococcus aureus
give 2 examples of upper respiratory colonisers that are gram negative
haemophilus influenza, moraxella catarrhalis
what are the hosts defences in the conducting airways
mucociliary escalator, cough, AMPs (antimicrobial peptides), cellular and humoral immunity
describe what causes infection
trauma, intubation of airway, abnormalities of defence (e.g. ciliary escalator), virulent pathogen/ large inoculum
what causes an aspiration pneumonia
impaired cough reflex
what is acute bronchitis
infection and inflammation of the airway
what are the clinical features of acute bronchitis
productive cough, +/- wheeze and fever, normal chest exam and cxr,
what precedes acute bronchitis
a URT infection
are antibiotics made available for acute bronchitis
not usually indicated
what are 90% of acute bronchitis cases a result of
viruses
what are the clinical features of a COPD acute exacerbation
productive cough or acute chest illness, breathlessness, wheezing, increased sputum purulence
what usually causes an acute exacerbation of COPD
often follows viral infection or fall in temp/ increase in humidity
what is COPD
blanket term for several diseases characterised by airflow obstruction- mainly chronic bronchitis and emphysema
what is an exacerbation
acute worsening of symptoms
what is sputum purulence
its colour- green, yellow, brown
what pathogens cause an exacerbation
30% viral, 50% bacteria e.g streptococcus pneumonia, haemophilus influenzae, moraxella catarrhalis and gram negatives
what does the recurrent inflammation of the airways on chronic bronchitis
hyper production of mucous (inc, neutrophils) inhibits the ciliary escalator, blocking the airways and impairing the hosts immune response
what is pertussis
whooping cough
what is whooping cough
acute trachea-bronchitis
describe the symptoms of whooping cough
cold like for 2 weeks, paroxysmal coughing 2 weeks, repeated violent exhalations with severe inspiratory whoop, vomiting, residual cough for month or more
what microorganisms are responsible for pertussis
bordetella pertussis- gram neg cocoobacillus
how is bordetella pertussis diagnosed
bacterial culture, PCR, serology, clinical signs and symptoms
what is a paroxysm
a violent episode of something
how and when is pertussis treated
with antibiotic is <21 days cough
what are the three main routes of transmission
contact, airborne, droplets
describe airborne transmission
small, <5 microns, travel long distances and remain airborne
what precautions do does airborne transmission need
standard infection control and filtering face piece 3
describe droplet transmission
larger particles, >5 microns, fall to floor within 2m, spread via contact
what are the standard infection control precautions
hand washing, PPE, door closed, decontamination before leaving room
when should a respirator be discard when airborne precautions are in actions
after leaving the room
why are infections common in CF
due to the inefficient clearance of mucous and chronic colonisation
what are some pathogens that cause infections in CF patients
Pseodomonas aeruginosa, burkholderia cepacia, staph. aureus, haemophilus influenza, strep pneumoniae
what are (and arent) the host defences of the lower respiratory tract (lungs) and what
no ciliary escalator.
alveolar lining fluid- surfactant, Ig, complement, FFA, AMP
alveolar macrophages and neutrophils- phagocytosis, inflammatory response
what are the clinical presentations of community acquired pneumonia
cough, increased sputum, chest pain, dyspnoea, fever, CXR with infiltrates
what is the pathological mechanism behind community acquired pneumonia
organism reaches lungs, immune activation and infiltration (systemic response), fluid and cellular build up in alveoli leads to impaired gas exchange
what is the most common pathogen that causes community acquired pneumonia
streptococcus pneumoniae
what other pathogens can causes community acquired pneumonia
viruses, haemophilus influenzae, steph. aureus
what are some risk factors for community acquired pneumonia
age, immunocompromised/suppressed,
smoking
how is community acquired pneumonia diagnosed
sputum culture, purulence, viral PCR
what is streptococcus pneumoniae sensitive to
amoxicillin, doxycycline, co-trimoxazole
how is pneumococcal pneumonia treated
5 day course of amoxicillin
what is the difference between invasive and non invasive pneumonia
invasive in blood stream
what can invasive pneumonia cause in the brain
meningitis
what microorganism causes typical community acquired pneumonia
streptococcus pnuemoniae
what microorganisms cause atypical community acquired pneumonia
mycoplasma pneumoniae, legionella pneumonia, chlamydophila pneumonia, chlamydia psitacci, viruses
how is legionella pneumonia diagnose
legionella unrinary antigen (detects serogroup 1 only), culture, paired serology, PCR from sputum
how is legionella pneumonia treated
claythromycin, erythromycin, quinolones- levofloxacin
is legionellla pneumonia typical or atypical
atypical
how does legionella pneumonia survive in the body
invades macrophages and replicates
what are the clinical symptoms of legionella pneumonia
flu like illness which may progress to a severe pneumonia with mental confusion, acute renal failure and GI symptoms
what is the mortality rate of legionella pneumonia
5-30%
how is legionella pneumonia transmitted
inhalation of contaminated water droplets
what are the risk factors for legionella pneumonia
exposure to contaminated aerosolised water, impaired immunity, >55YO, diabetes, malignancy, altered immunity
what is walking pneumonia
mild form of/ atypical
what is not used to treat a walking pneumonia and why
amoxicillin as organism has no cell wall
does does staphylococcus pneumonia follow
influenza
describe how cadiovascular infections of staphylococcus pneumonia
haematogeneous spread of staphylococcus aureus
what types of pneumonia cause relative bradycardia
legionella, mycoplamsa, tularaemia, chlamydia
what organisms cause hospital acquired pneumonia
60% gram negative (e-coli, klebsiella spp, pseudomonas spp), CAP organisms (S. Aureus and anaerobes)
how is HAP treated
IV amoxicillin (if penicillin allergic Co-trimoxazole) + metronidazole + gentamicin (+/- if pen. allergic)
what are the non infective causes of pneumonia
pulmonary inflitrates with eosinophilia; parasites, brucella, endemic mycoses, psittacosis, tuberculosis
what pathogens cause ‘classical flu’
influenza A and B viruses
what pathogens cause flu like illnesses
parainfluenza viruses and many others
what is haemophilus influenza and what does it do
bacterium, not primary cause of flu but can be secondary invader
what is the most common cause of death in influenza epidemics
secondary bacterial infections
what antivirals are used to treat flu
oseltamivir, zanamivir
when should antivirals be given
only when patient is at risk of complications
describe antigenic drift
when minor mutations in the surface proteins of the virus cause epidemics of flu
what virus causes a flu pandemic
influenza A
what other factors cause a flu pandemic
antigenic shift, segmented genome, animal reservoir/mixing vessel
how is influenza detected in the lab
PCR of a swab (direct detection of virus) or antibody detection
what is in a killed flu vaccine
inactivated virus- 2 different influenza A and 1 B + adjuvant
how is a live vaccine administered
intra-nasally
how are mycoplasma, coxiella and chlamydophila
all respond to tetracycline and macrolides
what pathogens cause a typical pneumonia
mycoplasma, coxiella and chlamydophila psittaci
how is an a typical pneumonia confirmed in a lab
serology or virus detection e.g PCR
in which groups of people is community acquired pneumonia caused by mycoplasma pneumoniae most common
children and young adults
how is community acquired mycoplasma pneumonia spread
person to person
what is q fever caused by
coxiella burnetii
what are the conditions caused by coxiella burnetii
pneumonia and pyrexia of unknown origin
who does coxiella burnetii affect
sheep and goats
what does chlamydophila psittaci cause
psittacosis
how does psittacosis usually present
as pneumonia
what is bronchiolitis and what is it also known as
inflammation of the fine bronchioles- respiratory syncytial virus
who does RSV affect
infancy
how does RSV clinical present
fever, coryza, cough, wheeze
how does RSV present in severe cases
grunting, reduced PaO2, intercostal/ sternal indrawing
what are the complications of bronchiolitis
respiratory and cardiac failure- common in premature babies or babies with pre existing resp or cardiac failure
why is bronchiolitis so common
epidemics every winter, no vaccine, nosocomial spread in hospital wards
what effect does metapneumovirus have on most children by the age of five
most antibody positive
