Pneumonia is an inflammation of the lower air passages and air sacs of the lungs resulting from infection of the parenchyma of the lungs. It is very common and most of the infections are in elderly patients. The mortality rate is up to 50%.
Pneumonitis is an acute inflammatory process that can be difficult to differentiate from pneumonia and can arise from infection, such as cytomegalovirus, or from non-infective processes such as inhalation of vomit or smoke. In this context ‘pneumonitis’ will be used for non-infective inflammatory processes of the lung.
Risk
factors for pneumonia in the immunocompetent adult
Most community-acquired
pneumonias are bacterial and the predominant pathogen is
Streptococcus pneumoniae.
Up to 13% of community-acquired pneumonias are viral in origin. Influenza A and B viruses are the predominant viral pathogens. Viral pneumonia is more common in the autumn and winter.
It is not possible to distinguish the causative organisms of pneumonia other
than by microbiology as no pathogen leads to a clinical, laboratory or radiological
pattern sufficiently characteristic to be the basis of a confident diagnosis,
but clinical
symptoms and epidemiological features
may provide clues to the aetiology as some differences in presentation do occur.
The distinction between typical and atypical pneumonia, although previously widely used, is not useful today. It is, however, helpful to distinguish between typical and atypical pathogens in pneumonia. Although these can only be determined by microbiology, not by clinical signs and symptoms, atypical pathogens are less common in patients aged 75 years and over.
Clinical assessment of disease severity is important for patient management, particularly in deciding which tests to use, where the patient should be treated (community, hospital ward or ICU), and which antibiotic regimens to use. The key issue in patient management is distinguishing those with severe pneumonia, who are at high risk of death, from those with non-severe pneumonia. Defining severe pneumonia accurately also has the added benefit of reducing over-prescribing.
The British Thoracic Society guidelines recommend that the following core adverse prognostic features should be assessed for all patients (CURB score):
Patient stratification based on CURB score
BTS
Guidelines for the management of community acquired pneumonia in adults
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Chest x-ray.
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The advantages and disadvantages of imaging are discussed in the new British Thoracic Society guidelines for the management of community-acquired pneumonia.
BTS
Guidelines for the management of community acquired pneumonia in adults
The choice of antibiotic, route of administration, and dose depend on the severity of the disease, probable pathogens and local resistance patterns.
(although it is often not possible to distinguish atypical pathogens clinically
and Legionnaires’ disease is often diagnosed in retrospect).The antibiotics chosen should be able to penetrate into alveolar tissue and fluid, and if the suspected pathogen is intracellular, such as Legionella or Mycoplasma spp., then the antibiotics chosen should also be capable of penetration into cells.
Glycopeptides are ineffective in treating pneumonia, because levels in alveolar
tissue are below the MICs for most Gram-positive organisms despite high plasma
levels.
If the patient is severely ill, unconscious or vomiting, intravenous therapy will be required.
Treatment durations should be at least five days, or longer if the patient
is slow
to respond,
with at least two to three weeks of treatment for staphylococcal pneumonia and
Legionnaires’ disease.
The following suggestions are suitable empirical antibiotic choices but do not replace local guidelines. Refer to local guidelines.
In non-severe pneumonia:
Amoxicillin monotherapy can be used if patients with non-severe pneumonia;
For all other patients with non-severe pneumonia, add a macrolide.
:
high-doses of a newer quinolone with good activity against Streptococcus
pneumoniae, or a newer macrolide, such as clarithromycin,
or an azalide, such as azithromycin.Severe pneumonia of unknown aetiology:
An alternative regimen for those allergic
to beta-lactams
is:
Once culture results are known, treatment can be adjusted accordingly. Your microbiologist will advise on suitable treatments. If the pathogen shows sensitivity to penicillin, there is an opportunity to change antibiotic therapy to one of the penicillins, thereby using minimal effective therapy and reducing the potential for antibiotic resistance.
Staphylococcus aureus, and especially MRSA,
is a rare cause of community-acquired pneumonia, but must be considered during
influenza epidemics or if the patient presents with a history suggesting recent
pneumonia. When treating Staphylococcus aureus, the duration
of treatment needs to be sufficiently long to minimise the possibility of systemic
embolic complications. Treatment may need to continue for 2–3 weeks. The following
antibiotics may be useful:
Methicillin-sensitive strains:
Treatment will depend on local sensitivities. Consult your local microbiologist.
Treatment may include:
In order to adequately cover atypical pathogens including: Chlamydia psittaci, Chlamydia pneumoniae, Q fever, or Mycoplasma pneumoniae, it is important to choose antibiotics with good penetration into lung tissues and fluids and high intracellular activity. Atypical organisms lack a conventional cell wall so beta-lactam antibiotics are inappropriate. Macrolides and tetracyclines are suitable first choices. Quinolones such as ciprofloxacin achieve very high concentrations in lung tissue (many times the plasma concentration), and have good activity against atypical pathogens so make good alternatives to macrolides or tetracyclines. If used as empirical therapy, a newer quinolone with enhanced activity against the Pneumococcus would be preferable. Treatment options include:
Patients who fail
to respond
to appropriate antibiotic therapy should be reassessed
and re-evaluated
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for other conditions or possible complications.
