48. Lower Respiratory Tract Infections Flashcards
What are the 2 main LRT infections?
What does LRT include?
Pneumonia - community acquired/hospital acquired
TB
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 chills, fever, 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?
CURB 2?
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.
