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what are the main differences between the upper and lower respiratory tract? (sterility, morbidity, mortality, cause)
- URTI: non sterile, high morbidity, low mortality, viral
- LRTI: sterile, high morbidity, high mortality, bacterial
what are the 2 main viral causes of rhinitis? and what type of viruses are they?
- rhinovirus: small RNA virus
- coronavirus: RNA virus
what is the pathogenesis of rhinitis?
infection/inflammation of nasal mucosa
what are the symptoms of rhinitis?
itchy eyes, blocked nose, sore throat, cough,
what is the main presentation of pharyngitis?
what is the most common cause of pharyngitis? give e.g.
virus: influenza, parainfluenza, EBV, HSV, Coxsackie A
what is the most important bacterial cause of pharyngitis?
group A streptococcus=strep progenies
what are the other bacterial causes of pharyngitis?
- haemophilus influenzae
- Group C and G Streptococci
- rarely Corynebacterium diphtheriae
how would you differentiate a bacterial sore throat from a viral?
- spiking temperature
- higher severity: barely swallow
- necrosis (white patches)
if you suspect bacterial pharyngitis what investigation needs to be done and why is it good and what is the immediate treatment and what needs to be avoided?
- bacterial THROAT SWAB as S.pyogenes grows overnight as beta-haemolytic clones on blood agar
- Rx: start penicillin for 10 days
- avoid: amoxicillin as if it is EBV - you can get a rash due to cross reaction between abx and virus
why do you treat GAS so aggressively?
- to prevent the immunological sequelae:
- acute glomerulonephritis
- rheumatic fever
- these happen due to immune mimicry: Ab against GAS cross react and bind to glomerular BM or cardiac membrane
why do some people with bacterial pharyngitis go red? what happens around eye?
- GAS makes an erythrogenic toxin which makes you go red = scarlet fever
- circumoral pallor: around eyes still white!
what is the test for glandular fever?
monospot or EBV antibody detection
what does acute otitis media and sinusitis usually follow?
why is AOM more in children under 5?
short eustachian tube
name 3 of the most common causes of AOM and acute sinusitis?
- Strep pneumo
- Haem influenzaue
- Moraxella catarrhalis
- i.e. from URT normal flora track via ET
what are the Rx options for AOM?
- watch and wait
- antimicrobials: amoxicillin
what are 3 Rx options of acute sinusitis:
- anti microbials
- surgical drainage
how does acute epiglottitis present?
stridor, drooling, sore throat, high fever
why is acute epiglottitis an emergency?
swelling may threaten airway
what USED to be the most common cause of acute epiglottitis and why is it no longer?
Haemophilus influenza b (now Hib vaccine)
what is now the most common cause of acute epiglottitis?
group A strep = strep progenies
what is the Ix and Rx of acute epiglottitis?
- Ix: do NOT examine mouth as may precipitate acute resp obstruction
- treat: high dose iv cefotaxime
what is whooping cough?
- bacterial illness: bordetella pertussis
what are the 3 clinical stages of pertussis?
- paroxysmal whooping stage
how do you diagnose pertussis?
pernasal swab onto spcecial charcoal media or PCR
what is the treatment of pertussis and for how long?
- erythromycin for 3 weeks
- penicillin resistant
what do we do to prevent pertussis?
acellular vaccination at 2, 3, 5 months and pre-school booster at 3-5years
what is croup? and how does it present?
- fever, barking inspiratory noises, cough, hoarseness
what is the most common causes of croup?
viral: infleunza and parainfluenza
what are the symptoms of influenza?
- sudden onset, fever, malaise, headache, myalgia, non productive cough, sore throat
- last 4-7days
what type of virus is influenza? (2 marks)
- RNA virus with segmented genome
what does the envelope of influenza contain?
- haemagglutinin (HA)
- neuraminidase (NA) proteins
what are the different types of influenza?
- A: epidemics and pandemics
- B: milder disease, pandemics
- C: not pathogenic in man
what is the difference between epidemic and pandemic?
- epidemic: out of control in one nation
- pandemic: out of control in more than 3 countries in the world
what time of the year does influenza outbreak?
what is the incubation period of influenza?
how does influenza spread as epidemics and pandemics?
- antigenic change in HA and NA
- shift: major change
- drift: minor change
what are the complications of influenza?
- primary influenza pneumonia (rare, often fatal - pregnant women)
- secondary bacterial pneumonia - causes death. infected with Staph aureus, pneumo, h.influ
how do you make a lab diagnosis of influenza?
- nasopharyngeal secretions or nose/throat swabs and do:
- viral culture, PCR, antigen detection by immunofluorescence
why is serology useless in most diagnosis?
retrospective so limited value. when get results, illness over!
how is influenza prevented? 3 ways from simple to complex
- 1. hand washing, disinfecting surfaces and use of masks to stop you touching your mouth
- 2. oseltamivir (NA inhib): use for post exposure prophylaxis
- 3. inactivated (killed) vaccine with current strains of influenza A and B
who is influenza vaccine given to?
- over 65 yo
- healthcare workers
- chronic illness: renal failure, heart probs, respiratory disease, liver disease, immunosuppressed
what is the treatment of influenza? and how does it work?
- oseltamivir or zanamivir both neuraminidase inhibitors give as soon as symptoms start
- they limit viral shedding
what type of virus is parainfluenza?
- 4 serotypes, 4 lower pathogenicity
what is the Rx of parainf?
Rx not usually indicated
which are the normal flora of the URT that cause LRTI?
- strep pneumoniae
- haemophilus influenzae
- moraxells catarrhalis
- staph aureus
why do normal flora of the URT cause LRTI?
reduced host defences
how are some bact/viruses transmitted?
how is coxiella burnetti spread?
transmitted via contact with animals/animal products
how is legionella pneumophila spread?
aerosolised contaminated water supplies
name 9 host defences:
- nasopharyngeal infiltration
- mucosal adherence
- lysozyme, protease, lactoferrin present in respiratory secretions
- mucociliary escalator
- cough and gag reflex
- immunoglobulins: IgA in nasal mucosa
- T and B lymphocytes
- alveolar macrophages
name 5 groups of patients that have reduced host defence and explain why door each one:
- ventilated patients: bypassed nasopharyngeal filtration, bypassed gag and cough reflex, reduced mucociliary clearance
- smokers: mucosal adherence is not as effective, mucociliary function impaired
- cystic fibrosis
what are Strep pneumo and h.infl's virulence factors?
- produce IgA protease: disable mucosal IgA
- polysaccharide capsules: resistant to phagocytosis
what is Bordatella pertussis' virulence factor?
makes endotoxins - widespread local damage
what is the main pathogen for bronchiolotis?
RSV: respiratory syncytial virus
who is most affected by bronchiolotis?
infants esp. in first 6 months of life
what type of virus is RSV and how many serotypes?
how is RSV spread?
droplet spread or contact with fomites
why do you have to end diagnose RSV?
how is RSV diagnosed?
- throat swab, nasopharyngeal aspirate into viral CULTURE
- viral antigen detected using IMMUNOFLUORESCENCE
how is RSV bronchiolitis managed?
- admit if severe LRTI
- supportive Rx: oxygen thearpy
- Ribavarin by AEROSOL inhalation or severe
- source isolation
- hand washing: prevent nosocomial transmission
what is used to prevent RSV in high risk infants?
- monoclonal RSV Ab vaccine: palivizumab
- in prewinter season to high risk babies. but £
what is the definition of pneumonia
inflammation of lung parenchyma caused by infection usually
what is the definition of community acquired pneumonia
presenting in community or within 48 hours of attending hospital
what are the 4 typical causes of bacterial CAP?
- strep pneumonia
- haemophilus influenzae
- moraxella catarrhalis
- staph aureus
- all give lobar pneumonia (typical)
what are 4 causes of atypical bacterial CAP?
- Mycoplasma pneumoniae
- Legionella pneumophila
- Coxiella burnetti: Q fever - rare - contact with animal product - vets
what is the leading cause of CAP in under 2yo?
name 3 viral causes of CAP and who does it affect?
- human metapneumovirus
- elderly and immunocompromised most at risk
what are the symptoms and signs of TYPICAL pneumonia?
- productive cough
- purulent sputum
- pleuritic chest pain
- shallow rapid breathing
- reduced chest movements
- dull to percussion
- bronchial breathing with COARSE crepitations
what type of bacteria is strep pneumo?
gram positive diplococcus
how does strep pneumo grow on blood agar?
what is strep pneumo the LEADING CAUSE OF?
- acute sinusitis
- acute exacerbations of COPD
how is strep pneumo diagnosed?
- CULTURE: blood or sputum
- antigen detection on URINE dipstick
what is the empirical treatment of typical CAP? give mild, mod sev
- mild-mod: amoxicillin
- severe: benzyl-penicillin plus clarithromycin OR cefurozime and clarithomycin
what is the presentation of ATYPICAL pneumonia?
- non productive cough
what are the CXR signs of atypical pneumonia?
what are the CXR signs of typical pneumonia?
who does legionella pneumophila commonly affect?
middle aged males
what time of year does legionella come about?
- summer months - related to travel - hotels with dodgy AC or water supply
- need exposure to CONTAMINATED WATER - showers, AC, sprays
how is legionella diagnosed?
- antigen in urine
- culture of respiratory secretions
what is the treatment of legionella pneumophila?
- macrolide: clarythromycin
- and rifampicin if severe (orange urine)
do patients with legionella pneumonia need to be source isolated?
no because it doesn't transmit from person to person
what type of year does mycoplasma pneumonia present?
sporadic or epidemic - 4 yearly cycles
who does mycoplasma pneumoniae affect?
children and young adults
how is mycoplasma pneumonia diagnosed?
- PCR on resp secretions
what is the treatment of mycoplasma pneumonia?
what is the definition of hospital acquired pneumonia?
acute pneumonia commencing 48 hours or more after admission to hospital
what are the risk factors for HAP?
- time in hospital
- time on ventilation
- NG tube - leading to oropharyngeal (gastric) aspiration
- PPI - inc gastric pH - as suddenly pseudomonas can survive there
- chronic pulmonary disease
- severity of underlying disease
what organisms cause HAP?
- staph aureus
- pseudomonas aeringosa
- respiratory viruses in immunocompromised
what are the poor prognostic indicators of pneumonia?
- Urea > 7mmol/l
- Resp rate > 30
- Blood pressure: SBP<90mmHg; DBP<60mmHg
- Age > 65yrs
- NB this score is not good for young people as they are fit, good for older adults
what is the empirical treatment for HAP?
broad spec beta lactam: piperacillin-tazobactam (tazocin) this covers coliforms, pseudomonas, staph aureus but not MRSA
what is needed in severe HAP?
empirical + gentamicin
what is needed to treat MRSA?
what is used in penicillin allergy?
what is the fast way of detecting Mycobacterium (for TB)?
auramine stain (rather than ZN stain)
where is the most common primary infection of TB?
name 3 rare sites of primary TB infection
what is primary pulmonary TB?
first contact with bacillus
what is a ghon complex a combination of?
- initial lesion: small focus of granuloma in parenchyma/subpleural - PERIPHERY of lung
- involvement of draining hilar LN: this is the larger response
what do ghon complexes look like macroscopically?
yellow necrotic areas in parenchyma and nodes
what is secondary pulmonary TB usually due to? 2 things
- 1. reactivation of primary TB
- only in 5% of primary TB cases
- 2. re-infection - e.g. health care worker
- 3. post BCG
where in the lung does primary pulm TB localise to compared to secondary, why?
- primary: periphery
- secondary: apices due to higher PO2 which mycobacterium love
what is the pathological sign of secondary pulm TB?
assmann focus - area of necrosis in apices of lung. more extensive parenchymal involvement of upper lobe
what are the 4 sequelae of progressive pulmonary TB?
- cavitatory fibrocaseous TB
- single organ TB
- miliary TB
what causes cavitating TB?
- usually secondary TB
- drainage of necrotic tissue into bronchus/bronchiole and formation of cavity
what are the conseuences of cavitating TB?
- spread of inflame within lUNGS
- spread into upper airways - then infected sputum swallowed…
- spread to gut
what is open TB?
once the TB has spread into the airways
what causes TB bronchopneumonia?
dissemination through airways
where can Tb spread to via the blood?
- bone - spine - Pott's disease - vertebral collapse and acute angulation of spine
- joints - arthritis
- GU tract
what is miliary TB? and what is it assoc. with?
- WIDESPREAD via blood
- assoc. with reduced immunity
where does miliary TB usually spread to?
- bone marrow
- i.e. organs with rich blood supply
is miliary TB usually seen with primary or secondary TB?
what are epitheloid cells?
macrophages that have lost their phagocytic function and so are ineffective in consuming bacteria
what are longhan's giant cells?
lots of macrophages (epitheloid cells) joint together to make a multinucleate cell. nuclei arranged in a horseshoe shape
name the 4 antiTB drugs and their SE
- rifampicin: orange urine
- isoniazid: hepatitis and peripheral neuropathy (due to depletion of vitB6 so have to give B6 supplements)
- pyrazinamide: hepatotoxicity
- ethambutol: visual disturbance (optic neuritis)