QuestionSBA
QuestionChoice
Splenectomy causes an increased risk of infection from encapsulated organisms with a 10-20 times greater risk of acquiring sepsis. P. jirovecii is a yeast-like fungus, and it does not have a capsule
33036
d
Pneumocystis jirovecii
QuestionChoice
Splenectomy causes an increased risk of infection from encapsulated organisms with a 10-20 times greater risk of acquiring sepsis. M. catarrhalis is not an encapsulated bacterium
33035
c
Moraxella catarrhalis
QuestionChoice
Splenectomy causes an increased risk of infection from encapsulated organisms with a 10-20 times greater risk of acquiring sepsis. Mycoplasma pneumoniae is not an encapsulated bacterium
33037
e
Mycoplasma pneumoniae
QuestionChoice
Splenectomy causes an increased risk of infection from encapsulated organisms with a 10-20 times greater risk of acquiring sepsis. The most common encapsulated bacteria are Haemophilus influenzae, Streptococcus pneumoniae, and Neisseria meningitidis. For this reason, patients are offered the pneumococcal vaccine, Hib vaccine, and the meningococcal vaccine post-operatively. Patients should also be offered annual flu vaccination and lifelong antibiotic prophylaxis
33033
a
Haemophilus influenzae
QuestionChoice
Splenectomy causes an increased risk of infection from encapsulated organisms with a 10-20 times greater risk of acquiring sepsis. C. psittaci is not an encapsulated bacterium
33034
b
Chlamydia psittaci
Concept
Chapter
# Summary 
 
Pneumonia is a radiological diagnosis, often due to a lower respiratory tract infection causing inflammation of the alveoli and terminal bronchioles, leading to consolidation of bronchopulmonary segment or lobe. Key signs and symptoms include rapid onset of high fever and productive cough for typical bacterial causes. Key investigations include blood tests, sputum culture, urinary antigen tests, and chest x-ray. Management strategies involve use of antibiotics, assessment of severity using CURB-65 score and inpatient treatment for severe cases.
 
 
# Definition
 
- Lower Respiratory Tract Infection/ Pneumonia is caused by infection and subsequent inflammation of the alveoli and terminal bronchioles.
- This leads to an entire bronchopulmonary segment or lobe becoming consolidated, which means that tissue is filled with inflammatory cells and oedema.
 
 
# Community Acquired Pneumonia (CAP)
 
 
## Bacterial Causes
 
 
- Typicals - so called because of the classical rapid onset of symptoms, including high fever and productive cough;
- Streptococcus pneumoniae (gram +ve cocci found in pairs, also known as 'Pneumococcus')
- Staphylococcus aureus
- Haemophilus influenzae (gram -ve rod, potent beta-lactamase producer)
- Moraxella catarrhalis (gram -coccus, potent beta-lactamase producer)
- Atypicals: so called because of the more gradual onset of symptoms, which may be non-specific initially (fever, myalgia, dry cough). The organisms are also intracellular;
- Mycoplasma pneumoniae
- Chlamydia pneumoniae
- Legionella pneumophila
- Coxiella burnettii
- Chlamydia psittaci
 
 
## Viral Causes 
 
- Most commonly Influenza A, which can predispose to superadded Staph aureus (or strep pneumoniae) pneumonia.
- Others: CMV, HSV, VZV
 
## Fungal Causes
 
Can be seen after silver staining and microscopy:
 
- Candida - dimorphic yeast
- Aspergillus - fungus with hyphae
- Cryptococcus - encapsulated yeast
 
 
## Specific Causes 
 
COPD: 
 
- Pneumococcus still most common
- Haemophilus influenzae
- Morexella catarrhalis
 
Cystic Fibrosis:
 
 
- Staph aureus
- Pseudomonas aeruginosa
- Burkholderia cepacia
 
Causes in Homeless people: malnourished, alcohol or drug dependent, immunosuppressed:
 
 
- Mycobacterium tuberculosis
- Aspiration pneumonia (infection with normal flora of mouth and anaerobes, also consider in any patient with an unsafe swallow or with depressed consciousness)
- Klebsiella pneumoniae (causes 'red-current jelly' sputum, and commonly causes lung abscess formation and empyema)
 
 
Occupational/travel situations:
 
- Aerosols from humidifiers and airconditioning (e.g. at holiday resorts) - Legionella pneumophila.
- Patients can present with diarrhoea and vomiting, develop hepatorenal syndrome and have a low sodium. Severe pneumonia develops, with other rare complications such as:
- Pancreatitis
- Peritonitis
- Myocarditis, endocarditis, pericarditis
- Glomerulonephritis
 
 
Closed populations e.g. schools, offices
 
- Mycoplasma pneumoniae
- Extra respiratory symptoms:
- Erythema multiforme, erythema nodosum
- Guillain-Barre Syndrome (and rarely other neurological complications e.g. aseptic meningitis, cerebellar disease, transverse myelitis).
- Cold agglutinin production with haemolytic anaemia
- Chlamydia pneumoniae
 
 
Zoonotic Causes: 
 
- In Abattoir worker, farmer, vets
- Coxiella burnettii
- Brucella spp.
 
- Animal hide importers/sorters
- Bacillus anthracis
- Coxiella burnettii
 
 
- Following exposure to birds
- Chlamydia psittaci (causes psittacosis)
- Exposure to bats/bat droppings
- Histoplasma capsulatum (a fungus, classically affects cave-explorers)
 
 
## Investigations
 
 
- Bloods: including FBC, U+Es, CRP, WCC and blood cultures
- Sputum culture
- Urinary antigen tests for Legionella and pneumococcus
- Chest X-Ray
- Could assess pleural fluid aspirate in patients with pleural effusion
 
 
## CURB-65 
 
 
- Use the CURB-65 score to aid in deciding the severity of pneumonia and further management based on this
- Components (1 point for each if present):
- Confusion +/-
- Urea >7
- Respiratory Rate >30
- Blood pressure: systolic < 90 or diastolic <60
- More than 65 years old
 
 
CURB-65 mortality by score:
 
- 0 or 1 - 1.5%
- 2 - about 10%
- 3 or more - 10% or more 
 
 
 
 
## Management
 
If a patient is very unwell, adopt an A-E approach, initiate the sepsis six and seek early senior input.
 
- Management based on CURB-65 score:
- 0/1: home-based care, give oral amoxicillin for 5 days (macrolide e.g. clarithromycin, doxycycline or tetracycline if penicillin allergic).
- 2: hospital-based care, 7-10 day course of dual antibiotic therapy with amoxicillin (IV or oral) and a macrolide
- 3: Hospital/ITU-based care, 7-10 day course of dual antibiotic therapy with IV co-amoxiclav/ceftriaxone/tazocin and a macrolide.
 
 
- Atypical and typical community-acquired pneumonia are both managed in the same way initially.
- Liaise with microbiology to guide targeted antibiotics following culture results e.g. flucloxacillin for staph aureus pneumonia.
- A repeat chest x-ray is required after 6 weeks to assess for underlying pathology.
 
 
## Complications
 
 
- Pleural effusion
- Empyema (suspect if persistent, swinging fever with leucocytosis found after antibiotic therapy)
- Abscess (can be caused by S. pneumoniae, Klebsiella, staph aureus). Can develop pyopneumothorax.
- Pneumothorax
- Septicemia
- Atrial fibrillation
- Post-infective bronchiectasis
 
 
 
 
# Hospital Acquired Pneumonia
 
 
## Definition
 
 
Lower respiratory tract infection that develops more than 48 hours after admission to hospital
 
 
## Risk Factors
 
 
- Poor hand hygiene and hospital infection control
- Intubation and ventilation
 
 
## Causative Organisms
 
 
- Pseudomonas aeruginosa
- E. coli
- Klebsiella pneumoniae
- Acinetobacter species (can acquire high potency beta-lactamases, known as ESBLs)
- Serratia species (can acquire high potency beta-lactamases, known as ESBLs)
 
 
## Investigations
 
May include:
 
- Bloods: including FBC, U+Es, CRP, WCC and blood cultures
- Sputum culture
- Urinary antigen tests for Legionella and pneumococcus
- Chest X-Ray
- Could assess pleural fluid aspirate in patients with pleural effusion
 
 
## Management 
 
If a patient is very unwell, adopt an A-E approach, initiate the sepsis six and seek early senior input and discussion with microbiology. Empirical antibiotics are guided by severity and likelihood of resistant organisms:
 
- HAP within 5 days of admission: co-amoxiclav is usually first line for non-severe symptoms
- HAP more than 5 days after admission (associated with higher risk of resistance) or severe symptoms: tazocin or cephalosporin (e.g. ceftazidime) or quinolone first-line.
- If MRSA is suspected, add vancomycin
 
 
# Aspiration Pneumonia 
 
 
- Caused by any cause of depressed consciousness or impairment of the swallowing mechanism
- Infection caused by mixed aerobic and anaerobic mouth flora, which can cause cavitary pneumonia or empyema
- Same empirical therapy as for non-aspiration pneumonia, but later antibiotic choice made by pathogen and sensitivities. Metronidazole often added in to cover for anaerobic organisms. Local guidance should be sought.
 
 
# NICE Guidelines
 
 
[Click here for NICE CKS on chest infections](https://cks.nice.org.uk/topics/chest-infections-adult/)
 
[Click here for NICE guidance on antimicrobial prescribing in hospital-acqui
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264
Pneumonia (Infectious Diseases)
Topic
58
Infectious Diseases
6607
Patients who have undergone splenectomy are at increased risk of infections from encapsulated organisms, particularly Haemophilus influenzae.
A 32-year-old man presents to the emergency department with 3 days of shortness of breath, productive cough with green sputum, and pyrexia. 5 years ago, he underwent an emergency splenectomy following a road traffic collision.

Which of the following organisms is he at greater risk of infection?
a