Pneumonia

 Definition & classification  Clinical features

 Community-acquired  Investigations & diagnosis
 Hospital-acquired  CRB-65 & CURB-65
 Aspiration  Management
 Immunocompromised
 Organisms

Definition & classification

Pneumonia is the inflammation of the parenchyma of the lung.
Pneumonia is a common type of infection affecting the lung tissue (i.e.
parenchyma). In pneumonia, the air sacs (i.e. alveoli) become filled with
microorganisms and inflammatory cells leading to poor lung function with
features of cough, fever, and shortness of breath. Pneumonia can be
life-threatening, particularly in frail, elderly patients or those who are
immunosuppressed. Pneumonia is one of several types of respiratory
infections, which include:

 Upper respiratory tract infection (URTI): inflammation of the

mucosa of the nostrils, nasal cavity, mouth, throat (i.e. pharynx),
and larynx. Colloquially known as the ‘common cold’
 Lower respiratory tract infection (LRTI): refers to inflammation of
the lower airways. This includes bronchitis, pneumonia and
exacerbation of COPD.
 Pneumonia: inflammation of the lung parenchyma with the normal
air-filled lungs becoming filled with infective liquid (known as
consolidation)

The most common cause of pneumonia is infection and the majority of

these are bacterial in nature. Viruses, fungi, and parasites may also
cause pneumonia.
Bacteria may reach the lungs via one of three routes:

 Inhalation
 Aspiration
 Haematogenous

These infections may result in both pulmonary and extrapulmonary

symptoms. Diagnosis often involves demonstrating acute consolidation
on a chest radiograph but may require testing for a specific organism.

Pneumonia may be divided into groups based on the location it was

contracted, comorbidities, and the immune status of the patient. This
helps to identify the likely causative organism and guide management.

Community-acquired
CAP is a pneumonia that is contracted in the
community. It has as traditionally been
divided into typical and atypical pneumonia.
In essence, CAP refers to pneumonia
contracted outside of the hospital setting and
includes those developing the condition in a
nursing home.

Typical pneumonias
These tend to present with features 'typical' of pneumonia; a productive
cough, fever and pleuritic chest pain. Likely infecting organisms include:

 Streptococcus pneumoniae (most commonly)

 Haemophilus influenzae
 Moraxella catarrhalis
Atypical pneumonias
These tend to have a more insidious, subacute onset. They often
present with a combination of pulmonary and extrapulmonary symptoms.
Likely infecting organisms may be divided into nonzoonotic and zoonotic
causes:

 Nonzoonotic: Mycoplasma pneumoniae, Legionella pneumophila,

Chlamydophila pneumoniae
 Zoonotic: Chlamydophila psittaci (psittacosis), Coxiella burnetii (Q
fever), Francisella tularensis (tularemia).

Hospital-acquired
HAP is defined by NICE as a pneumonia contracted > 48 hrs after
hospital admission that was not incubating at the time of admission.
Patients in hospital adopt the local bacterial environment, one that differs
from what is encountered in the community. This is known to persist for
a number of weeks following discharge. Likely organisms include:

 Gram-negative bacilli (e.g. Pseudomonas aeruginosa)

 Staphylococcus aureus
 Legionella pneumophila

Aspiration
Aspiration pneumonias are caused by the inhalation of oropharyngeal or
gastric contents. This brings bacteria found in these environments into
the lungs.
Aspiration pneumonias have typically been associated with patients who
are unable to adequately protect their airway, it may be seen in patients
with:

 Reduced conscious level

 Neuromuscular disorders
  Oesophageal conditions
 Mechanical interventions such as endotracheal tubes.

It is increasingly recognised that many CAPs and HAPs may result from
an otherwise inconsequential aspiration event. Studies have shown
hospitalised patients on proton-pump inhibitors are more at risk of
developing HAP than those who are not, implicating aspiration in the
aetiology.

Infective organisms include Streptococcus pneumoniae, Staphylococcus

aureus, Haemophilus influenzae, and Enterobacteriaceae, in the hospital
Gram-negative bacilli (e.g. pseudomonas aeruginosa) is more likely to
be implicated.

NOTE: Mendelson’s syndrome is a related condition, It is defined as a

chemical pneumonitis caused by aspiration of acidic gastric contents
classically seen by obstetric anaesthetists.

Immunocompromised
Patients with pathological and iatrogenic immunosuppression are at risk
of infective organisms not usually seen in other patient groups.
We consider a wider range of likely causative organisms in
immunocompromised patients:

 Bacterial pathogens: as discussed as well as the mycobacterium

complex and non-tuberculosis mycobacterium.
 Fungal pathogens: such as Pneumocystis jirovecii, Aspergillus
fumigatus and Cryptococcus neoformans.
 Viral pathogens: such as varicella zoster virus and cytomegalovirus
should be considered.
 Parasitic pathogens: parasitic pneumonias are very rare and seen
almost exclusively in the immunocompromised.
Organisms- Numerous organisms may be responsible for a
pneumonia, below a few common organisms are discussed.

Streptococcus pneumoniae
Streptococcus pneumoniae is a gram-positive alpha-haemolytic
streptococci. It is the most common cause of CAP (classically lobar),
presenting with a cough, pleuritic pain and pyrexia. It frequently causes a
significant leucocytosis and a raised CRP.

It classically gives rust coloured sputum and may be accompanied by

the reactivation of cold sores. Urinary antigen tests may be used to
diagnose the infection and is unaffected by antibiotics.

Mycoplasma pneumoniae
Mycoplasma pneumoniae is a rod-shaped bacterium that lacks a cell
wall. It tends to affect a younger demographic and occurs in cyclical
epidemics.

It causes a pneumonia with a prolonged, insidious onset that may exhibit

extrapulmonary features. Extrapulmonary features include:

 Erythema multiforme
 Arthralgia
 Myocarditis, pericarditis
 Haemolytic anaemia

Diagnosis can be made with serology.

Legionella pneumophila
L. pneumophila is a gram-negative coccobacillus that may cause the
atypical CAP (typically lobar) Legionnaire’s disease. It is encountered in
those exposed to contaminated cooling systems, humidifiers and
showers. Chest symptoms may be preceded by several days of myalgia,
headache and fever.
Hyponatraemia, secondary to SIADH, is a classical finding in
Legionnaire’s disease but is not always present. Other biochemical
abnormalities include hypophosphataemia and raised serum ferritin.

Diagnosis may be made with urinary antigen testing (for serogroup 1).
Cultures of respiratory secretions and PCR may also be used.

Pseudomonas aeruginosa
P. aeruginosa is a gram-negative bacillus that typically HAP. In patients
with bronchiectasis (e.g. cystic fibrosis) is may cause CAP. It is often
described as an opportunistic pathogen, rarely causing disease in
healthy individuals. Typically it causes pneumonia in immunosuppressed
patients and those with chronic lung disease. It should be remembered it
may affect many of the bodies systems independent of the lungs and
can lead to a bacteraemia.

It tends to cause the symptoms classically associated with pneumonia.

Sputum is characteristically green. Delineating between active infection
and incidental airway colonisation can be difficult. Bronchoalveolar
lavage may be used to obtain samples. Treatment often involves a
cephalosporin and aminoglycoside. Aerosolised antibiotics may be used
in patients with cystic fibrosis.

Klebsiella pneumophila
K. pneumophila is a gram-negative bacillus that classically causes CAP
classically seen in alcoholics. It causes a fast moving lobar pneumonia.
Symptoms include a cough, fever and flu-like features. Sputum may
have the characteristic ‘red-currant jelly’ appearance.

K. pneumophila shows resistance to beta-lactams. Beta-lactamase

stable beta-lactams, cephalosporins and aminoglycosides may be used
to treat the infection.

Pneumocystis jirovecii
Pneumocystis jirovecii (formerly PCP/ pneumocystis carinii), a fungi, is
an AIDS-defining illness that may cause a life-threatening pneumonia. It
causes fever, cough (frequently non-productive) and exertional
dyspnoea. Hypoxia and a raised LDH are also common findings.

It may be diagnosed with sputum stains though bronchoalveolar lavage

may be required to obtain samples. It is now classified as a fungi though
was previously described as a protozoa. It does not respond to
antifungals and is instead treated with co-trimoxazole (trimethoprim-
sulfamethoxazole).

Clinical features
Pneumonia is often characterised by cough, SOB, and the signs of
consolidation. In atypical pneumonias extrapulmonary features may
predominate.

Symptoms
 Fever
 Malaise
 Cough (purulent sputum)
 Dyspnoea
 Pleuritic pain

Signs
 Dull percussion note
 Reduced breath sounds
 Bronchial breathing (transmission of bronchial sounds to
peripheries due to consolidation)
 Coarse crepitations
 Increased vocal fremitus (increased transmission of ’99' through
consolidated lung)
 Tachycardia
 Hypotension
  Confusion
 Cyanosis

Complications
The course of a pneumonia may be interrupted by any of a number of
complications.

 Pulmonary complications:

 Parapneumonic effusion
 Pneumothorax
 Abscess
 Empyema
 Extrapulmonary complications:
 Sepsis
 Atrial fibrillation

Investigations & diagnosis

Investigations should not delay antibiotic treatment which should be
administered within 4 hours of admission or diagnosis (and < 1 hour
where sepsis is suspected).

Bedside
 Observations
 Sputum sample
 Urinary sample:

 Microscopy, Culture and Sensitivity (MC&S): Consider to

exclude urinary source of infection
 Urinary antigens: Consider pneumococcal and legionella
urinary antigen tests to help guide antibiotics
  ECG

Bloods
 Full blood count (FBC)
 Urea & electrolytes (U&Es)
 CRP
 Blood cultures

For patients presenting to their GP, NICE (NG 191) advise considering a
point of care CRP where diagnosis is uncertain or unclear whether
antibiotics are indicated.

Imaging
 Chest x-ray: often diagnostic showing consolidation though
findings may lag behind onset and remain following resolution. May
also show parapneumonic effusions, pneumothorax, abscess and
empyema.

CRB-65 & CURB-65

CRB-65 and CURB-65 are scoring systems that help stratify patients risk
of mortality and determine the best place of care.
Each category is worth one point when present. Confusion may be
defined as an AMT < 8 (abbreviated mental test) or new-onset
disorientation in time, place or person.

CRB-65
The CRB-65 is an aid to clinical judgement
that helps to assess the need for hospital
admission. It may be calculated in primary
care to stratify th severity of the infection.
0 - Low risk (mortality <1%), 1-2 - intermediate risk (mortality 1-10%), 3-4
- high risk (mortality >10%).

Clinical judgement must be used to determine who needs hospital

assessment (+/- admission), however, the CRB-65 can be used to help
guide this decision. Patients should be considered for home-based care
if they score 0, whilst hospital assessment should be considered for all
other patients (especially if ≥ 2)

CURB-65
CURB-65 is calculated when a patient presents to hospital, it includes a
urea measurement and helps establish the best place of care.

0-1 - Low risk (mortality <3%), 2 - intermediate risk (mortality 3-15%), 3-5
- high risk (mortality >15%).

As with the CRB-65 clinical judgement is key, however, as a general rule

consider outpatient care for a score of 0-1, inpatient care for a score of 2
and ICU care for a score of 3 or more.

Management -Management is dependent on severity, type

of infecting organism, & local hospital guidelines. Below we discuss
options for empirical antibiotic treatment, this may vary depending on
local guidelines.
General measures - Patients may present with pneumonia of
varying degrees of severity. In those who are acutely unwell physicians
should adopt an ABC approach. A number of general measures should
be considered in the treatment of a patient hospitalised with pneumonia.

 Oxygen titrated to saturations: Aim for saturation of 94-98% in

patients without underlying lung disease. In patients at risk of type
II respiratory failure (e.g. COPD) aim for saturations of 88-92%.
 IV fluids: patients may be dehydrated, correct any deficit and
prescribe maintenance fluids as appropriate.
 Appropriate analgesia: Paracetamol may be sufficient. NSAIDs
may be used with appropriate consideration and care. In cases of
more severe pain consider opiate analgesics. Care should be
taken due to respiratory depressant effects.


Antibiotics
Treatment should follow local antibiotic guidelines with input from
microbiology as required. For those seeking detailed guidance, NICE
have guidelines covering management of both CAPs and HAPs:

 NG 138: Pneumonia (community- acquired): antimicrobial

prescribing (published 2019)
 NG 139: Pneumonia (hospital-acquired): antimicrobial prescribing
(published 2019)
Community-acquired:

Low severity:

 Oral therapy with a broad spectrum beta-lactam (e.g. amoxicillin).

 A tetracycline or macrolide may be used in those with a penicillin
allergy (doxycycline or clarithromycin).
 A typical antibiotic course would be 5-7 days.

Intermediate severity:

 Most can be treated adequately with oral therapy.

 Dual therapy with a beta-lactam (e.g. amoxicillin) and a macrolide
(e.g. clarithromycin).
 Doxycycline may be used as an alternative in those with a penicillin
allergy.
 A typical antibiotic course would be 7-10 days.

High severity:

 IV beta-lactamase stable beta-lactam (e.g co-amoxiclav) and a

macrolide (e.g. clarithromycin).
 An antibiotic course of 7-10 days may be extended to 14 or 21
days depending on clinical circumstance.

Hospital-acquired:

 Should follow local guidelines based upon local microbial

knowledge.
 Co-amoxiclav 625mg orally TDS may be used in mild infections.
 Tazocin (piperacillin/tazobactam) 4.5g IV TDS may be used in
severe infections.

Follow-up CXR
Research indicates that 11% of smokers over the age of 50 who have pneumonia have lung
cancer. This may be incidental or causative, tumours may block parts of the bronchial tree
increasing the risk of infective events. A CXR at 6-8 weeks post-event should be used to
screen for underlying lung cancers in this age group.