Microbio 12: Resp Tract Infections Flashcards
Streptococcus pneumoniae is:(type of bacteria?)
Gram-positive cocci in chains
Alpha-haemolytic and optochin-sensitive
Why is no microbiological identification of the pathogen made in most cases of CAP?
Difficult to obtain a good sputum sample and early treatment is usually initiated with empirical antibiotics
List the main organisms that cause CAP.
SMH
Streptococcus pneumoniae - aka pneumococcus
Moraxella catarrhalis
Haemophilus influenzae - cavitating leisons
Staphylococcus aureus
Klebsiella pneumoniae
List the most prevalent pathogens causing CAP in the following age groups: 0-1months 1-6months 6m-5y 16-30y
0-1 months
Escherichia coli
Group B Streptococcus
Listeria monocytogenes
1-6 months
Chlamydia trachomatis
Staphylococcus aureus
RSV
6m-5y
Mycoplasma pneumoniae
Influenza
16-30y
Mycoplasma pneumoniae
Streptococcus pneumoniae
List the causes of CAP that fall into the following two categories:
Typical
Atypical
Typical:
Streptococcus pneumoniae
Haemophilus influenzae
Atypical: Legionella Mycoplasma Coxiella burnetii Chlamydia psittaci
What is the CURB-65 score? How is it interpreted?
Confusion Urea > 7 mmol/L Respiratory rate > 30/min BP < 90 systolic, < 60 diastolic Age> 65
Score of 2 = consider hospital admission
Score of more than 2 = severe pneumonia that may need ITU admission
Outline the presentation of bronchitis.
Cough
Fever
Increased sputum production
Increased SOB
Which organisms cause bronchitis?
Viruses
Streptococcus pneumoniae
Moraxella catarrhalis
Haemophilus influenzae
List some bacterial causes of cavitating lung lesions.
Staphylococcus aureus
Klebsiella pneumoniae
TB
What type of bacterium is H. influenzae?
Gram-negative cocco-bacilli (rod)
How is Legionella spread?
Inhalation of infected water droplets
What medium is Legionella grown on?
Buffered charcoal yeast extract
What is a common feature of bacteria that cause atypical pneumonia?
They have NO cell wall
List four atypical organisms.
Mycoplasma
Legionella
Chlamydia
Coxiella
Which type of antibiotics do not work on atypical bacteria?
Penicillins
NOTE: this is because they act on cell walls
Which type of antibiotics do work on atypical bacteria?
Antibiotics that interfere with protein synthesis (macrolides, tetracyclines)
List some clinical features of Legionella pneumophila infection.
Confusion Abdominal pain Diarrhoea Lymphopaenia Hyponatraemia
Urinary antigens are associated with which causes of pneumonia?
Streptococcus pneumoniae
Legionella pneumophila
Which investigation is used for Coxiella and Chlamydia psittaci?
Serology
NOTE: serology looks at the development of antibodies after an infection (requires paired samples). It is useful for investigating bacteria that are difficult to culture
What is an empyema?
Collection of pus within the pleural cavity
List some reasons for failure to respond to treatment.
Empyema/abscess
Proximal obstruction (e.g. tumour)
Resistant organisms
Not absorbing antibiotics
Immunosuppression
Alternative diagnosis (e.g. lung cancer)
What is the classical CXR feature of TB?
Upper lobe cavitation
Which types of staining are used when investigating TB?
Auramine staining
Ziehl-Neelsen stain - GOATED
NOTE: they are red rods
Define hospital-acquired pneumonia.
A pneumonia that is onset > 48 hours after hospital admission
List some organisms that cause HAP.
Enterobacteriaciae (MOST COMMON – e.g. E. coli, K. pneumoniae)
Staphylococcus aureus
Pseudomonas
Haemophilus influenzae
Acinetobacter baumanii
Fungi (e.g. Candida)
What is Pneumocystic jirovecii pneumonia?
Fungus that is ubiquitous in the environment but can cause pneumonia in immunocompromised patients
Describe the typical presentation of Pneumocystic jirovecii pneumonia.
Dry cough Weight loss SOB Malaise Walk test – desaturation on exertion
How is PCP investigated?
Bronchoalveolar lavage
What is the treatment for PCP?
Co-trimoxazole (septrin)
What are the main features of allergic bronchopulmonary aspergillosis?
Chronic wheeze
Eosinophilia
Bronchiectasis
What is an aspergilloma? symptom?
Fungal ball often forming within a pre-existing cavity
May often cause haemoptysis
How is invasive aspergillosis treated?
Amphotericin B
Which organisms cause pneumonia in the following subgroups of patients: HIV Neutropaenic Bone marrow transplant Splenectomy
HIV:
PCP, TB, Atypical mycobacteria
Neutropaenic:
Fungal (eg. Aspergillus)
Bone marrow transplant:
CMV
Splenectomy: Encapsulated organisms (NHS)
In which organisms is serology useful for reaching a diagnosis?
Organisms that are difficult to culture
Examples: Legionella, Chlamydia, coxiella
Which organism is investigated using immunofluorescence? how else is this detected?
PCP
NOTE: PCP can also be detected using silver stain
What is the treatment for mild-to-moderate CAP?
Amoxicillin
OR erythromycin/clarithromycin (if penicillin allergic)
What is the treatment for moderate-to-severe CAP?
Co-amoxiclav AND clarithromycin
What is treatment options for HAP?
Caused by MRSA or Pseudomonas?
Ceftazidime
If MRSA - Vancomycin
If Pseudomonas - Tazocin + Gentamicin
A 22 year old presents with shortness of breath and a cough with associated green
sputum. Her X-ray is shows lobar pneumonia.
What is the most likely causative organism?
A) Klebsiella pneumoniae B) Haemophilus influenzae B C) Moraxella catarrhalis D) Streptococcus pneumoniae E) Staphylococcus aureus
D) Streptococcus pneumoniae - standard + no unique symptoms, is the most common
A 45 year old man alcoholic presents with shortness of breath and cough. His
sputum is blood-streaked and his X-ray is shows a cavitating leison.
What is the most likely causative organism?
A) Klebsiella pneumoniae B) Haemophilus influenzae C) Moraxella catarrhalis D) Mycoplasma pneumoniae E) Staphylococcus aureus
A) Klebsiella pneumoniae - alcoholic + blood streaked sputum is suggestive of klebsiella pneumoniae
HiB and Staph aureus can also cause cavitating leisons but history suggests the answer above
What is the most likely causative organism of a hospital acquired pneumonia?
Pseudomonas aeruginosa
RFs for HAP?
Admitted for 48+ hours
Intubated + ventilated
A 35 year old man presents to his GP with shortness of breath and a dry cough. He
has been feeling feverish and complains of myalgia. He takes potent steroids for
his eczema and lives at home alone apart from his pet dog and parrot.
What is the most likely cause of his pneumonia? A) Bacteroides B) Coxiella burnetti C) Chlamydia psittaci D) Mycoplasma pneumoniae E) Staphylococcus aureus
C) Chlamydia psittaci - This is an atypical pneumonia and this pt is at risk from steroid use + parrots are a buzzword for this organism
What pneumonia is associated w/ transverse myelitis?
Atypical pneumonia caused by mycoplasma pneumonia
What pneumonia is associated w/ air conditioning / hotel stay / stil water? What biochem findings may you find?
Leigonella pneumonia
Hyponatraemia + Deranged LFTs
Which pneumonia is associated w/ farm animals?
Coxiella burnetti
Atypical pneumonia symptoms?
- Dry cough
- Headache
- Abdo pain
- Diarrhoea
Atypical pneumonia investigations? what is specific to mycoplasma?
- Sputum MCS
- Urine antigen
- Serology
- Blood film (mycoplasma – may mention cold agglutins in SBAs)
What organisms would you see causing pneumonia in a pt w/ unsafe swallow? Mx of this?
Aspirational pneumonia caused by anaerobes from gut flora
It’s caused by anaerobes so treat w/ Metronidazole
Mx of atypical pneumonia?
Clarithromycin
A 30 year old woman is being treated with chemotherapy for acute lymphoblastic leukemia (ALL). She has recently been complaining of shortness of breath and had an episode of blood-streaked sputum. A chest X-ray is performed and a ‘Halo sign’ can be seen
What is the organism causing this?
What is the most appropriate treatment?
A) Co-amoxiclav B) Dexamethasone C) Fluconazole D) Oseltamivir E) Amphotericin B
Currently immune suppressed by chemo
‘Halo sign’ refers to nodule w/ ground-glass shadowing - caused by aspergillosis
Organism = Aspergillus
This means you need an anti-fungal to treat it (Leaves options C and E)
E) Amphotericin B - anti-fungal of choice in aspergillus
A 24 year old HIV-positive woman presents with difficulty breathing. She feels especially short of breath after walking, and her exercise tolerance is greatly reduced.
What is the most likely causative organism? What is the CXR finding in these pts? Mx?
A) Influenza A B) Aspergillus fumigatum C) Influenza B D) Pneumocystis jirovecii pneumonia E) SARS-CoV-2
D) Pneumocystis jirovecii pneumonia - Strong associated w/ HIV + Shows SOBOE
Ground-glass shadowing - bat’s wing
Co-trimoxazole
Erythema nodosum + FLAWS + Haemoptysis is associated w/ which resp infection?
TB
Best and most accurate test for TB? what is the growth medium used?
Test - Zeihl-Neelsen Stain
Culture - grown on Lowenstein-Jensen growth medium
Mx of TB? - Mneumonic
RIPE: R - Rifampicin 6/12 I - Isoniazid 6/12 P - Pyrazinamide 2/12 E - Ethambutol 2/12
Mx of influenza?
Oseltamivir
