48. Lower Respiratory Tract Infections Flashcards Preview

Year 1 - Term 2: Carriage of Oxygen > 48. Lower Respiratory Tract Infections > Flashcards

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What are the 2 main LRT infections?

What does LRT include?

Pneumonia - community acquired/hospital acquired


Also tracheitis, pleurisy, bronchiolitis, bronchitis


LRT: Trachea, primary bronchi, lungs

One of most important causes of death in kids <5 worldwide


Describe the 2 types of pneumonia.

1. Community-acquired: frequent in young, old and comorbidites (e.g. COPD, HIV, asthma), maybe 20 to viral respiratory tract infection, 40-60% = can't ID cause. Caused by typical/atypical pathogens.

2. Hospital-acquired: predisposing factors: abnormal conscious state, intubation, surgery, ventilation and immunosuppression. Frequenty caused by G- organisms, often MDR. 3rd commonist hospital infection but highest mortality (20-50%). E.g. Pseudomonas aeruginosa, Enterobacter


List some typical and atypical causes of community acquired pneumonia.

What does typical community-acquired pneumonia present with?

What about atypical pneumonia?

Typical: Streptococcus pneumoniae (diff strains and many diff antigens, can go to heart, brain, abdomen etc.), Haemophilus influenzae, Moraxell catarrhalis, S. aures post influenza, Group A strep (upper RTI)

Atypical: Mycoplasma pneumoniae, Chlamydia pneumoniae, C. psittiace, Legionella pneumophilia, M. tuberculosis, Coxiella burnetii

Sudden onset chillsfever, pleuritic chest pain + productive cough. WCC increased. Thick purulent sputum (can be rust coloured). CXR = parenchymal involement. S. pneumonia commonest cause. 

Doesn't respond to BETA-LACTAM therapy. Gradual onset, non-productive cough, fever, headache, CXR abnormal.


What can you see in this CXR?

Consolidation of L upper lobe, classical for S. pneumonae - pneumonia


What can you see in these images of the lung and sputum gram stain?

L: lobar consolidation on L

R: lots of G+ cocci and pus


How would you ID Streptococcus pneumoniae?

What is M. pneumoniae?

How is it diagnosed?

Catalase negative, alpha hemolytic colonies, bile soluble (all other streptococci are resistant), susceptible to Optochin

Droplet transmission, epidemic every 3-4yrs, fever, headavhe, myalgia, earache, dry cough, arthritis sometimes. Skin rashses, haemolytic anaemia, neurological complications poss.

Clinical and CXR = patchy bilateral bronchopneumonia, hard to culture, Abs produced against pts own RBC. Use IgM test, serology (look for Abs against M. pneumoniae) and PCR


What is Legionnaires Disease?

How is it diagnosed?

Caused by Legionella pneumophila, v small G- bacteria, slow grower, need specialist media and dyes, motile, lives in amoeba in warm water -> adapted to hot water heaters, storage tanks, shower heads etc. Control systems needed.

History (exposure to cooling towers etc.), Clinical (multi-system disease, confusion, myalgia, renal failure etc.), Lab (CXR - patchy interstitial involvement/consolidation, Hyponatraemia, urea increase, liver function test abnormal), Isolation of L. pnuemophila via cultures/visulation in sputum or tissue/in urine via EIA (serogroup 1)


What is Chlamydia pneumoniae?

What is Q fever?

What is Penumocystis jirovicii?

Causes atypical pneumonia, intracellular pathogen, zoonosis acquired from birds, unculturable on lab media

Caused by Coxiella burnetii, transmitted via infected animals e.g. milk, can cause atypical pneumonia, diagnosis usually by serology

Imp. cause of pneumonia in v. immunocompromsed (so not 10 atypical), fever, dyspnoea, non-productive cough. Diagnosis = histological (silver staining). Treatment = co-trimoxazole or steroids


What are some complications of pneumonia?

How would you diagnose hospital-acquired pneumonia?

What would you use to determin the severity of pneumonia?

Pleural effusion (3-5%, clear fluid +/- pus), empyema thoracis (1%, pus in pleural space), lung abcess (destruction of lung parenchyma, single (aspiration) or multiple (metastatic))

History, clinical exam, CXR, Bloods (Hb, WBC, platelets, UsEs, ESR), urine (can find pneumococcal antigen in urine), blood cultures, sputum (microscopy, culture, sensitivity), serodiagnosis/antigen detection

CURB 65 score - clinical severity prediction, 0 = low risk of death, 1-2 = hospitalisation considered, 3 or more = high risk, urgent admission


What can you see on these CXRs?

L: pleural effusion and patchy consolidation on L, fluid would have to be aspirated/drained

R: 2 huge abceses full of fluid (prob pus) on R, would need chest drain/surgical


What is the treatment for community-acquired pneumonia?

What are the preferred treatments for 0-1 CURB score?


Beta-lactams sometimes given as monotherapy e.g. amoxicillin, benzylpenicillin, cefuroxime but inactive against Mycoplasma pneumoniae (no cell wall) and poor against intracellular orgs like Legionella and Chlamydia spp.

0-1: Amoxicilin (alt = doxycycline)

2: Amoxicillin + clarithromycin (alt = doxycycline)

NB: if legionella suspected add levofloxacin


What is a prevention measure for penumonia?

What is TB?

How does a person contract pulmonary TB?

Penumococcal vaccine: includes 23 antigens, recommended for certain individuals.

Chronic mainly respiratory bacterial disease but can affect almost any other organ, caused by Mycobacterium tuberculosis (also M.bovis/africanum,microti), exposure does not always = infection, can be fought or latent. 

Inhaling infected droplet nuclei from a cough/sneeze by infected person (from their granuloma in lung tissue)


List some symptoms of TB.

Describe mycobacteria.

What 2 stains could you use for mycobacteria?

Poor appetite, productive cough +/- blood/mucus, chills, night sweats, weight loss. Chest pain and if extra pulmonary: meninges, lymph nodes, GI tract, bone and joints and genitourinairy tract can all show symptoms.

Aerobic, non-motile, rods, distinctive cell wall (waxy mycolic acid outer layer = protective and v diff to other bacteria: resistance to drying/antibiotics/disigectants/acids and alkalis/impermeable to standard stains/survives in macrophages

Ziehl-Neelsen (wax holds stain fast so acid won't decolarise it -> then counterstain, looks red) or Auramine-phenol (fluorescent)


What can you see on this CXR? What would you diagnose the patient with?

Ghon focus: on bottom R (10 lesion stuck to pleura, caused by TB (mycobacterium bacilli), small area of granulomatous infection only detectable on CXR if it calcifies/grows substantially. 

Gohn complex: when the GF involves infection of adjacent lymphatics and hilar lymph nodes.


What methods are there for detecting Mycobacterium tuburculosis?

Microscopy (quick and done on any sample but low sensitivity and specificity)

Culture but takes a long time, needs wide range of growth conditions, some unable to culture. Media: solid or liquid, if need time = contamination.

Automated systems: lq culture media, continuously monior and flag up real time new +ves, decreased workload, can be used for susceptibility testing, measures O2 consumption/CO2 production but single incubation temperature

ID via nucleic acid probes against reference lab, result in 24h (but need culture for it). Strips coated with 165 DNA sequences and probes complementary, hybridisation, marker => bands on strip.


What is susceptibility testing?

What is the Mantoux test? What can be done instead now?

Test 1st lines for all new cases: isoniazid, rifampicin, pyrazinamide, ethambutol. Can do via molecular assays: ID spp from cultures. Use 10 samples e.g. sputum, CSF. Genotype resisitance testing for rifa and ison (can do in machine - cartridge but expensive)

Skin test, see if previous TB infection. Inject extract of mycobacterium antigens and measure reaction 48-72hrs later. If v marked, may have TB. Now can do it via blood: take lymphocytes and stimulate with same antigens from Mantoux test -> produce interferons if respond (IGRA).


How is TB diagnosed?

What is the antimicrobial therapy for TB?

How is MDR TB be treated - what 2nd line drugs?

What is XDR TB?

Clinical (history, exam, radiology), microscopy and culture from affected site (e.g. pulmonary = sputum on 3 consecutive days), histology (caseating granuloma = contain necrosis), immunological tests (mantoux/heaf and IGRA)

6m minimum: 2m rifampicin + isoniazid + pyrazinamide + ethambutol, 4m rif and iso. Longer if complicated TB e.g. MDR, meningitis. DOT to ensure compliance

MDR = resistant to iso and rif so use aminoglycoside (e.g. amikacin, kanamycin), fluoroquinolone, ampicillin, ethambutol, pyrazinamide

MDR + resistance to quinolones/injectables


What can be used to prevent TB?

BCG vaccine - not part of routine childhood vaccination unless live in high prevalence area. Attenuated strain of M. bovis. Initial 10-15yrs then wanes.

Control contamination

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