Respiratory Tract Infection Flashcards
Upper respiratory tract is commonly colonised by which gram-positive bacteria?
GRAM POSITIVE STREPTOCOCCI: alpha and beta hemolytic streptococci, Strep penumonia and Strep pyogenes (respectively.)
GRAM POSITIVE STAPHYLOCOCCI: Staphylococcus aureus
What is the microorganism associated with epiglottitis?
Haemophilus influenza type B (Hib)
How is epiglottitis treated?
Ceftriaxone - a cephalosporin. SEFF-TRIA-ZONE
Tests for epiglottitis?
Blood culture, do not throat swab as patient has a compromised airway due to inflamed epiglottis.
For haemophilus influenzae gram stain would show pink (gram negative.)
Haemophilus influenza type B will also grown on chocolate agar/lysed blood agar.
What is the most commonly encountered organism in exacerbations of COPD?
Moraxella Catarrhalis, gram negative diplococcus
What tests would you do in an acute exacerbation of COPD?
Resp exam: cyanosed, wheeze, crackles
Sputum culture to find out the causative microorganism (infleunce antibiotics)
Sputum purulence - severity?
CXR to rule out pneumonia
Treatment for acute exacerbation of COPD?
Antibiotics -> doxycycline or amoxicillin
Bronchodilator inhalers
Short course of steroids in some cases
Evidence of respiratory failure- oxygen
Cystic fibrosis microbiology
Inefficient clearance and build up of mucus = EVERYTHING
Acute Bronchitis Microbiology
Usually viral origin and usually preceded by an upper respiratory tract infection
What is pertussis?
Whooping cough
acute tracheobronchitis
“cold like” symptoms for two weeks.
Paroxysmal cough is main feature
What is the microbiology of pertussis?
Bordatella pertussis, gram negative coccobacillus
How do you diagnose Pertussis?
Take a nasal swab
Attempt grow bacteria on culture. Bortadella Pertussis (pertussis causative organism) would grow on charcoal blood agar!
Can also perform PCR on nasal swab specimen
Can also perform serology on nasal swab specimen
There are not many organisms that would cause paroxysmal cough!
Treatment for pertussis?
Treat with antibiotics if less than 21 days cough
Macrolides - clarithromycin or erythromycin if pregnant patient.
Most common causative organism of community aquired pneumonia?
Streptococcus pneumoniae (70%)
Diagnosis of community acquired pneumonia?
Purulent sputum
Sputum culture: culture on blood agar depends on organism. E.g. alpha hemolysis for streptococcus pneumoniae
Perform PCR on sputum, should be negative for viruses
Perform Gram stain to deermine type of bacteria, will see lots of pus cells
Check if its legionella pneumonia by looking for the legionella antigen in URINE
CXR Consolidation, alveolar infiltrate and pleural effusion
Pathogenesis of legionella pneumonia?
Invades alveolar macrophages and replicates
What is legionella pneumonia?
Atypical pneumonia. Gram negative bacteria, obligate intracellular organisms that resides in water amoeba.
Treatment for legionella pneumonia?
Macrolides - clarithromycin/erythromycin if preg
Quinolones such as levoflaxacin
Treatment for hospital acquired pneumonia? 0-2 CURB 65 score?
Amoxicillin IV/PO, doxycycline if penicillin allergic
Treatment for hospital acquired pneumonia? 3-5 CURB 65 score?
Co Amoxiclav IV and Doxycycline PO
Treatment for pneumocystis pneumonia?
Co-trimoxazole (trimethoprim and sulfamexazole- folic acid synthesis inhibtors)
Acute Bronchitis clinical presentation
Productive cough, normal chest X ray and examination, fever and wheeze may be seen.
How would you diagnose aspergiullus?
Fungal infection
Take a history - immunocompromised/supressed patients due to undergoing chemotherapy, or having AIDs. Infection can also occur in immunocompetent patients with underlying disease such as severe pneumonia, COPD or TB. These patients may have developed an aspergilloma.
Bronchoalveolar Lavage - use specimens to check for fungal culture and perform PCR to check for Aspergillus. Broncholaveloar lavage is when sterile fluid squirted into bronchi then collected for examination
What is an aspergilloma?
It is a fungus ball that develops in the chest cavity, usually in patients with underlying resp disease such as bronchitis, sacroidosis TB or COPD
What are the treatment options for aspergillosis?
Antifungal medication - Amphotericin B and Voriconazole
Surgery
How would you diagnose TB?
Take a history! Associated with travel/birth in areas with high prevalence.
Microscopy of sputum/tissue
PCR
Mycoplasma TB is acid fast - check using zheil Neelsen stain
Grow culture on mycoplasma specific media - Lowenstein Jensen
How does a ziehl Neelsen stain work?
Mycobacteria have a thick waxy coat. Thus it retains stain even after exposure to alcohol and acid. Other bacteria would not be able to retain the stain.
This is why mycoplasma is considered acid fast.
What are the advantages and disadvantages of a Ziehl Neelson stain?
Advantages are that it is fairly cheap, but does not indicate species of myobacteria OR drug sensitivity.
What are the advantages and disadvantages of a PCR?
This is expensive but will give you FAST results. Limited information on species and drug sensitivity.
What are the advantages and disadvantages of a mycobacterial culture?
Slow! Culture is incubated for several months. However this gives information on drug sensitivity and is a highly specific and sensitive test.
For mycobacterial species, which medium promotes faster growth?
Liquid media > Lowenstein Jensen
What is the treatment for TB?
Pyrazinide Rifampicin Isoniazid Ethambutol Streptomycin PRIEST!
The upper respiratory tract is colonised by which GRAM NEGATIVE bacteria?
H influenzae, moraxella catharasis
