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Pneumonia

Table of contents
Key points ⚡
Succinct notes to superpower your revision
Pneumonia\: acute infection of lung parenchyma caused by various pathogens; annual incidence in UK\: 5-10 per 1000
adults; hospitalisation rate\: 22-42%; mortality rate\: 5-14%.
Community-acquired pneumonia (CAP)\: occurs outside hospital; most common pathogens\:
Bacterial\: S t r e p t o c o c c u s p n e u m o n i a e (most common), H a e m o p h i l u s i n
c a t a r r h a l i s .
Atypical\: M y c o p l a s m a p n e u m o n i a e , C h l a m y d o p h i l a p n e u m o n i a e , L e g i o n e l l a p n e u m o p h i l a .
Viral\: in
Fungal\: C r y p t o c o c c u s n e o f o r m a n s , candida, A s p e r g i l l u s , H i s t o p l a s m a c a p s u l a t u m , P n e u m o c y s t i s j i r o v e c i i .
Hospital-acquired pneumonia (HAP)\: infection after 48 hours of hospital admission; common pathogens\: P s e u d o m o n a s
a e r u g i n o s a , E s c h e r i c h i a c o l i , K l e b s i e l l a p n e u m o n i a e , S t r e p t o c o c c u s p n e u m o n i a e , S t a p h y l o c o c c u s a u r e u s (including MRSA).
Ventilator-associated pneumonia\: occurs 48-72 hours after tracheal intubation; pathogens similar to HAP.
Aspiration pneumonia\: inhalation of oropharyngeal contents; common in swallowing dysfunction, general anaesthesia,
delayed gastric emptying, poor cough; microbiology similar to non-aspiration pneumonia.
Risk factors\: age (infants, elderly), smoking, alcohol use, pre-existing respiratory conditions (COPD, asthma, lung cancer,
bronchiectasis), IV drug use, hospitalisation, PPIs, poor oral hygiene, child contacts.
Symptoms\: productive cough, dyspnoea, pleuritic chest pain, fevers/rigors, confusion (elderly), lethargy, malaise, myalgia,
anorexia, headache.
Clinical examination\:
Vital signs\: tachypnoea, hypoxia, tachycardia.
Chest examination\: coarse crackles, decreased breath sounds, dullness to percussion, wheeze.
Investigations\:
Bedside\: basic observations, PCR test.
Laboratory\: FBC, CRP, U&Es, LFTs, sputum culture, blood cultures, ABG, Legionella and pneumococcal urinary antigen.
Imaging\: chest X-ray (diagnostic), CT thorax (if needed).
Diagnosis\: based on history, clinical examination, and radiological evidence (chest X-ray).
CURB-65 score\:
Confusion, Urea >7 mmol/L, Respiratory rate ≥30, Blood pressure \<90 systolic or ≤60 diastolic, Age ≥65.
Score 0-1\: low risk (outpatient treatment).
Score 2\: moderate risk (consider inpatient or supervised outpatient treatment).
Score 3-5\: high risk (inpatient treatment, consider critical care).
Management\:
Supportive\: rest, oral hydration.
Medical\: antibiotics (according to local guidelines), oxygen, IV
Antibiotics for CAP\:
Low severity\: amoxicillin, doxycycline, or clarithromycin.
Moderate severity\: amoxicillin + clarithromycin, or doxycycline.
High severity\: co-amoxiclav + clarithromycin.
Antibiotics for HAP\:
Non-severe\: co-amoxiclav, co-trimoxazole, or doxycycline.
Severe\: piperacillin with tazobactam, meropenem, or ceftriaxone.
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Vaccination\:
Pneumococcal (PPV, PCV) for infants, elderly, and at-risk groups.
Haemophilus in
Complications\: septic shock, ARDS, pleural e
Article 🔍
A comprehensive topic overview

Introduction

Pneumonia is de
includes several clinical syndromes caused by various organisms or pathological insults.
1
The annual incidence of community-acquired pneumonia in the UK is estimated at 5-10 per thousand adults. The
proportion of UK adults requiring hospitalisation due to community-acquired pneumonia is between 22-42%, with a
mortality rate of 5-14%.
2
This article will focus on the aetiology, risk factors, clinical features, diagnosis and management of pneumonia, including
the CURB-65 score.

Aetiology

Pneumonia can be classi
appearance. This article will focus on the most commonly used classi

Community-acquired pneumonia

Community-acquired pneumonia (CAP) is de
infection associated with new radiographic shadowing for which there is no other explanation, occurring outside of the
hospital or healthcare setting.
3
CAP is then generally subclassi
Bacterial
Bacterial cases of pneumonia have traditionally been divided into ‘typical’ and ‘atypical’ pneumonia, with the term now
outdating its historical usefulness.
Atypical pathogens are often challenging to diagnose early in the illness as they may not be detectable on gram stain or
cannot be cultured using standard methods. They are also usually sensitive to antibiotics other than β-lactams.
3,4
Typical
Typical bacterial pneumonia is caused by the most common organisms associated with pneumonia. S t r e p t o c o c c u s
p n e u m o n i a e is the leading bacterial cause of CAP across a range of age groups.
5
Other bacterial causes include H a e m o p h i l u s i n 6
c a t a r r h a l i s . However, mixed pathogens are not uncommon.
S t a p h y l o c o c c u s a u r e u s (including MRSA), and M o r a x e l l a
Atypical
Atypical bacterial pneumonia is caused by less common organisms that may be more challenging to diagnose or may be
associated with speci
C h l a m y d o p h i l a p n e u m o n i a e , and L e g i o n e l l a p n e u m o p h i l a .
4
Speci
Exam questions typically test the aetiology in speci
Table 1. Common causative organisms in speci
7
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Patient group/condition Pathogen(s)
Chronic obstructive pulmonary
disease (COPD)
Alcoholism
Post-in
H a e m o p h i l u s i n
P s e u d o m o n a s a e r u g i n o s a
K l e b s i e l l a p n e u m o n i a e ,
S t r e p t o c o c c u s p n e u m o n i a e
S t a p h y l o c o c c u s a u r e u s ,
S t r e p t o c o c c u s p n e u m o n i a e
C h l a m y d o p h i l a p n e u m o n i a e
Exposure to birds Hotel or cruise ship stay in the
previous two weeks
Intravenous drug use L e g i o n e l l a p n e u m o p h i l a
S t a p h y l o c o c c u s a u r e u s
Viral
Viral respiratory tract infections can lead to primary viral pneumonia and predispose to secondary bacterial pneumonia. The
most common viruses detected in cases of CAP are in
8
Other causes are severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), rhinoviruses, parain viruses,
adenoviruses, respiratory syncytial virus and other coronaviruses (e.g., Middle East respiratory syndrome CoV).
8
Fungi
Fungal pneumonia is rare and primarily seen in immunocompromised patients and endemic areas. These include
C r y p t o c o c c u s n e o f o r m a n s , candida species, A s p e r g i l l u s species, H i s t o p l a s m a c a p s u l a t u m and P n e u m o c y s t i s j i r o v e c i i .
9

Hospital-acquired pneumonia

There is considerable overlap between community and hospital-acquired pneumonia (HAP). However, HAP is de
lower respiratory tract infection acquired after 48 hours of hospital admission, which was not incubating at the time of
admission.
10
The causative organisms in HAP are typically more prevalent in the hospital environment and have increased rates of
antimicrobial resistance. These K l e b s i e l l a p n e u m o n i a ) and usually gram-positive include cocci gram-negative bacilli (P s e u d o m o n a s a e r u g i n o s a , E s c h e r i c h i a c o l i ,
(S t r e p t o c o c c u s p n e u m o n i a e , S t a p h y l o c o c c u s a u r e u s (including MRSA)).
11
S . p n e u m o n i a e is the most prominent bacteria in infections occurring within the
11
Ventilator-associated pneumonia
This represents a sub-set of hospital-acquired pneumonia, typically occurring in the critical care setting. Ventilator-
associated pneumonia is de
to those of HAP.
11

Aspiration pneumonia

Aspiration pneumonia results from inhaling oropharyngeal contents, which can predispose to bacterial infection, chemical
pneumonitis (secondary to acidic gastric secretions) and lung injury.
This is more common in those with swallowing dysfunction (e.g. after a stroke), undergoing general anaesthesia, delayed
gastric emptying (e.g. obesity, pregnancy), and those with a poor cough (e.g. neuromuscular disorders, nerve palsies).
Microbiological aetiology varies depending on the source of the aspirate and individual factors. However, recent studies
have shown that bacteriology remains similar to non-aspiration pneumonia.
12

Risk factors

Risk factors for pneumonia include\:
6,13
Age\: particularly infants/young children and those >65 years old
Smoking\: particularly pneumococcal pneumonia
Alcohol use\: there is a strong correlation between increased alcohol use and pneumonia
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Pre-existing respiratory conditions\: COPD, asthma, malignancy, bronchiectasis
Intravenous drug use\: often associated with S t a p h y l o c o c c u s a u r e u s
Hospitalisation or residence in a healthcare setting (e.g. nursing homes)
Proton-pump inhibitors\: thought to be secondary to increased upper airway colonisation due to reduced gastric acid
secretion
Poor oral hygiene\: particularly in aspiration pneumonia
Child contacts\: likely due to increased rates of transmission

Clinical features

History

Typical symptoms of pneumonia include\:
11
Productive cough\: with mucopurulent sputum in bacterial pneumonia
Dyspnoea\: shortness of breath, particularly on exertion
Pleuritic chest pain\: pain exacerbated on deep inspiration
Fevers and rigors\: feeling hot and sweaty with cold chills
Confusion\: typically seen in the older population
Constitutional features\: including lethargy, malaise, myalgia, anorexia, and headache
For more information, see the Geeky Medics guide to respiratory history taking.
Atypical pneumonia may present with a characteristic history and features depending on the organism.
Table 2. Characteristic features of atypical pneumonia.
6,13
Organism Characteristic features
M y c o p l a s m a
p n e u m o n i a e
Slow-onset history over a few days or weeks
May present as a sore throat, lethargy, headache,
nausea, abdominal pain and diarrhoea in young
adults
Persistent dry and hacking cough
Typically resolves spontaneously over a few
weeks in healthy patients
C h l a m y d o p h i l a
p n e u m o n i a e
Gradual onset, which may show improvement
before worsening again
Incubation period can be 3-4 weeks
Non-speci
including cough and wheezing
Productive cough with scanty, watery sputum
Most remain well or are asymptomatic
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L e g i o n e l l a p n e u m o p h i l a
Typically associated with a contaminated water
supply, i.e., poorly maintained air-conditioning or
humi
Incubation period 2-10 days
Cough is prominent, with dyspnoea and pleuritic
chest pain common
Gastrointestinal upset with diarrhoea and
vomiting is also seen
Neurological disruption, including confusion, is
more common than with other pneumonia
Arthralgia and myalgia are often reported
Can precipitate
hyponatraemia

Clinical examination

A complete respiratory examination is required in all cases of suspected pneumonia.
Typical clinical
6
Vital signs\: tachypnoea, hypoxia, and tachycardia may all be present
Course crackles and/or decreased breath sounds\: on auscultation of the chest
Dullness to percussion\: over the a
Wheeze\: particularly in those with associated respiratory conditions, i.e., asthma/COPD

Di

Di
6
Upper respiratory tract infection
Exacerbation of COPD
Exacerbation of asthma
Congestive heart failure
Coronavirus disease 2019
Tuberculosis
Lung cancer
Empyema
Pulmonary embolism

Investigations

Investigations beyond basic observations are typically unnecessary for most patients in the community setting. For patients
admitted to the hospital, all of the following should be considered.
6,11,13

Bedside investigations

Relevant bedside investigations include\:
Basic observations\: to assess for hypoxia, fever, tachypnoea, tachycardia and hypotension (in septic shock)
Polymerase chain reaction (PCR) test\: this allows for the rapid identi
test, i.e., an extended viral screen including SARS-CoV-2

Laboratory investigations

Relevant laboratory investigations include\:
Full blood count\: may demonstrate a raised white cell count.
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C-reactive protein (CRP)\: elevated in infection and can be used to aid prognosis.
Urea and electrolytes\: urea is part of the CURB-65 severity score, and patients may present with a comorbid acute
kidney injury. Hyponatraemia may be seen in L e g i o n e l l a .
Liver function tests\: baseline hepatic function for antibiotic treatment. These may be deranged in L e g i o n e l l a
Sputum culture\: ideally taken before starting antibiotics, with antibiotics optimised based on sensitivities. The sample
should be expedited to microbiology to prevent degradation.
Blood cultures\: should be requested in all patients with moderate or high-severity pneumonia. Ideally, cultures should
be taken before antibiotics are given. Antibiotics should then be optimised based on sensitivities.
Arterial blood gas\: recommended in hypoxic patients, those at risk of hypercapnia or who are graded as high-risk
pneumonia, depending on the patient it may show type 1 or type 2 respiratory failure.
Legionella and pneumococcal urinary antigen\: this should be requested in those with moderate or high-severity CAP
or where other risk factors exist.

Imaging

Relevant imaging investigations include\:
Chest X-ray\: the diagnostic investigation for pneumonia. Evidence of consolidation is seen.
CT thorax\: this is only considered where there is diagnostic doubt or if a chest X-ray suggests abnormalities which
require further imaging.
Figure 1. Chest X-ray showing a right
sided area of consolidation, representing
a segmental pneumonia

Diagnosis

A diagnosis of pneumonia can be reached with typical features in the history and on clinical examination, alongside
radiological evidence on a chest X-ray.

CURB-65

The severity of community-acquired pneumonia can then be calculated using the CURB-65 score.
6
Confusion\: new onset, which may be de≤8
Urea\: of >7 mmol/L
Respiratory rate\: ≥30 breaths/minute
Blood pressure\: \<90 mmHg systolic or ≤60 mmHg diastolic
Age\: ≥65 years
Each criterion scores one point, with the total used to guide hospital admission, treatment, critical care escalation and
mortality. However, CURB-65 is an arbitrary scoring system and should complement clinical judgment.
Score 0-1\: low risk
Consider outpatient treatment
Score 2\: moderate risk
Consider inpatient or hospital-supervised outpatient treatment
Score 3-5\: high risk
Admission for inpatient treatment with consideration for discussion with critical care if achieving the higher end of the
range
In the community setting, urea may be removed, with CRB-65 utilised instead.
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Management

Acute management

The acute management of pneumonia consists of supportive measures, such as rest and oral hydration, alongside
medical management, such as antibiotics. Acutely unwell patients should be assessed with an ABCDE approach.
Patients well enough to remain in the community can generally be managed with supportive measures and oral antibiotics.
Those who require hospital admission may require more intense medical management alongside antibiotics\:
Oxygen\: to maintain appropriate oxygen saturations.
Intravenous
Medics article on IV )
Analgesia and antipyretics\: simple analgesia such as paracetamol and non-steroidal anti-in
no contraindications) or a weak opioid (e.g., codeine), if required.
Venous thromboembolism (VTE) prophylaxis\: all hospitalised patients should undergo a VTE risk assessment and
receive appropriate prophylaxis.

Antibiotic prescribing

Local guidelines should be followed for antibiotic prescribing due to local resistance and sensitivities. NICE recommends
initial antibiotic treatment based on pneumonia severity, typically lasting
All antibiotics should be reviewed at 48-72 hours in conjunction with culture sensitivities, in
patient’s clinical signs. The antimicrobial of choice, dose and route should be considered. Speak to a senior clinician or
microbiologist if you have concerns.
Intravenous antibiotics should be prescribed in patients with clinical features of severe infection or sepsis or where
gastrointestinal absorption is not reliable (i.e., vomiting, severe diarrhoea).
Community-acquired pneumonia
These are some antimicrobial options based on NICE guidelines for CAP in adults. 14
local guidelines.
As mentioned above, always consult
Low severity
First choice oral antibiotic\:
Amoxicillin\: 500 mg – 1 g three times a day
Alternative oral antibiotics\:
Doxycycline\: 200 mg on day one, then 100 mg a day
Clarithromycin\: 500 mg twice a day
Moderate severity
First choice combination of\:
Amoxicillin\: 500 mg – 1 g three times a day
Clarithromycin\: 500 mg twice a day
Alternative oral antibiotics\:
Doxycycline\: 200 mg on day one, then 100 mg a day
Clarithromycin\: 500 mg twice a day
Erythromycin (in pregnancy)\: 500 mg four times a day
High severity
First choice combination of\:
Co-amoxiclav\: 500/125 mg three times a day orally, or 1.2 g three times a day IV
Clarithromycin\: 500 mg twice a day
Hospital-acquired pneumonia
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These are some antimicrobial options based on NICE guidelines for HAP in adults. 15
As mentioned above, always consult
local guidelines.
Non-severe
First choice oral antibiotic\:
Co-amoxiclav\: 500/125 mg three times a day orally
Alternative oral antibiotics\:
Co-trimoxazole\: 960 mg twice a day
Doxycycline\: 200 mg on day one, then 100 mg a day
Severe
First choice IV antibiotics\:
Piperacillin with tazobactam\: 4.5 g three times a day (four times a day if severe infection)
Meropenem\: 0.5 g – 1 g three times a day
Ceftriaxone\: 2 g once a day

Vaccination

There are also vaccinations available to protect against various causes of pneumonia. See the Geeky Medics childhood
immunisations article for more information on the childhood vaccine schedule.
Pneumococcal
Two forms of pneumococcal vaccine are currently used in the UK; the pneumococcal polysaccharide vaccine (PPV) and the
pneumococcal conjugate vaccine (PCV). Both are inactivated vaccines.
16
The pneumococcal conjugate vaccine (PCV) is o
are required for those with asplenia, splenic dysfunction, complement disorder, or severe immunocompromise.
The pneumococcal polysaccharide vaccine (PPV) is o
clinical risk groups, including\:
Asplenia or splenic dysfunction
Chronic respiratory disease
Chronic heart disease
Chronic kidney disease
Chronic liver disease
Diabetes (medication or insulin-dependent)
Immunosuppression
Cochlear implants
Cerebrospinal
Occupational risk
Haemophilus in
A polysaccharide conjugate vaccine is o
one year. Hib is typically combined with other vaccines.
17

Complications

6,13
Complications of pneumonia include \:
Septic shock\: pneumonia can lead to sepsis, which can rapidly progress to multi-organ failure and shock.
Acute respiratory distress syndrome (ARDS)\: consists of non-cardiogenic pulmonary oedema and severe lung
in
Pleural e\: associated with increased pneumonia severity and risk of treatment failure.
Empyema\: a collection of pus within the pleural space.
Lung abscesses\: rare but more commonly seen in K l e b s i e l l a or S t a p h y l o c o c c a l pneumonia.
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Post-infective bronchiectasis\: permanent dilation and thickening of the airways.

References

Mackenzie G. The de
NICE. Pneumonia in adults\: diagnosis and management. Published online 2014. Available from\: [LINK]
Lim WS, Baudouin SV, George RC, et al. BTS guidelines for the management of community acquired pneumonia in adults\:
update 2009. T h o r a x . 2009;64(Suppl 3)\:iii1-iii55.
BMJ Best Practice. Atypical pneumonia (non-COVID-19). Published 2021. Available from\: [LINK]
Chapman SJ, Robinson GV, Shrimanker R, Turnbull CD, Wrightson JM. Respiratory infection—bacterial. In\: Chapman SJ,
Robinson GV, Shrimanker R, Turnbull CD, Wrightson JM, eds. O x f o r d H a n d b o o k o f R e s p i r a t o r y M e d i c i n e . Oxford University
Press; 2021\:517-558.
BMJ Best Practice. Community-acquired pneumonia (non-COVID-19). Published 2023. Available from\: [LINK]
File TM. Community-Acquired Pneumonia, Bacterial. In\: N e t t e r’ s I n f e c t i o u s D i s e a s e s . Elsevier; 2012\:127-136.
Ramirez J. Overview of community-acquired pneumonia in adults. UpToDate. Published 2023. Available from\: [LINK]
Li Z, Lu G, Meng G. Pathogenic Fungal Infection in the Lung. F r o n t I m m u n o l . 2019;10\:1524.
BMJ Best Practice. Hospital-acquired pneumonia (non-COVID-19). Published 2023. Available from\: [LINK]
Shebl E, Gulick PG. Nosocomial Pneumonia. In\: S t a t P e a r l s . StatPearls Publishing; 2023. Available from\: [LINK]
BMJ Best Practice. Aspiration pneumonia. Published 2023. Available from\: [LINK]
Knott L. Pneumonia. Patient.info. Published 2020. Available from\: [LINK]
NICE. Pneumonia (community-acquired)\: antimicrobial prescribing. Published online 2019. Available from\: [LINK]
NICE. Pneumonia (hospital-acquired)\: antimicrobial prescribing. Published online 2019. Available from\: [LINK]

Related notes

Public Health England. Chapter 25\: Pneumococcal. In\: I m m u n i s a t i o n a g a i n s t I n f e c t i o u s D i s e a s e . ; 2023.
Public Health England. Chapter 16\: Haemophilus in
Asthma

Image references

Bronchiectasis
Figure 1. Pneumonia right side segmental X-ray 1. theSimTech. Available from\: [LINK]
Chronic Obstructive Pulmonary Disease (COPD)
Croup

Reviewer

Cystic Fibrosis
Dr Ahmed Abou-Haggar
Respiratory Consultant

Test yourself

Contents

Introduction
Aetiology
Risk factors
Clinical features
Di
Investigations
Diagnosis
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