Microbio 12: Resp Tract Infections Flashcards by D J

Streptococcus pneumoniae is:(type of bacteria?)

Gram-positive cocci in chains

Alpha-haemolytic and optochin-sensitive

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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

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List the main organisms that cause CAP.

SMH
Streptococcus pneumoniae - aka pneumococcus
Moraxella catarrhalis
Haemophilus influenzae - cavitating leisons

Staphylococcus aureus
Klebsiella pneumoniae

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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

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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

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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

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Outline the presentation of bronchitis.

Cough
Fever
Increased sputum production
Increased SOB

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Which organisms cause bronchitis?

Viruses

Streptococcus pneumoniae
Moraxella catarrhalis
Haemophilus influenzae

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List some bacterial causes of cavitating lung lesions.

Staphylococcus aureus

Klebsiella pneumoniae

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What type of bacterium is H. influenzae?

Gram-negative cocco-bacilli (rod)

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How is Legionella spread?

Inhalation of infected water droplets

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What medium is Legionella grown on?

Buffered charcoal yeast extract

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What is a common feature of bacteria that cause atypical pneumonia?

They have NO cell wall

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List four atypical organisms.

Mycoplasma
Legionella
Chlamydia
Coxiella

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Which type of antibiotics do not work on atypical bacteria?

Penicillins

NOTE: this is because they act on cell walls

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Which type of antibiotics do work on atypical bacteria?

Antibiotics that interfere with protein synthesis (macrolides, tetracyclines)

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List some clinical features of Legionella pneumophila infection.

Confusion 
Abdominal pain 
Diarrhoea 
Lymphopaenia
Hyponatraemia

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Urinary antigens are associated with which causes of pneumonia?

Streptococcus pneumoniae

Legionella pneumophila

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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

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What is an empyema?

Collection of pus within the pleural cavity

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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)

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What is the classical CXR feature of TB?

Upper lobe cavitation

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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?

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