COMMUNITY ACQUIRED PNEUMONIA &

ATYPICAL PNEUMONIA

Dr. M. A. Sofi MD; FRCP; FRCPEdin; FRCSEdinAl Maarefa College of Science & Technology

Community Acquired Pneumonia

Definition:◦… an acute infection of the pulmonary

parenchyma with an intense infiltration of neutrophils in and around the alveoli and the terminal bronchioles. The affected bronchopulmonary segment or the entire lobe may be consolidated by the resulting inflammation and oedema. Presence of an acute infiltrate on a chest radiograph, or auscultatory findings consistent with pneumonia, in a patient not hospitalized or residing in a long term care facility for > 14 days before onset of symptoms.

Age: especially infants, young children and the elderly.

Lifestyle: smoking, alcohol.Preceding viral infections -

e.g., influenza predisposing to Streptococcus pneumoniae infection.

Respiratory: asthma, chronic obstructive

pulmonary disease (COPD), malignancy, bronchiectasis, cystic fibrosis.

Immunosuppression: AIDS, cytotoxic therapy -

increased risk of infection with staph. spp., tuberculosis, Gram-negative bacilli and P. jirovecii.

Intravenous drug abuse: often associated with

Staphylococcus aureus infection.

Hospitalization: often Gram-negative

organisms.Aspiration pneumonia: patients with impaired

consciousness or patients with oesophageal obstruction are at risk of aspiration pneumonia which usually affects the right lung and is caused by anaerobes from the oropharynx.

Underlying predisposing disease: diabetes mellitus, cardiovascular disease

Risk factors

Community Acquired Pneumonia

Epidemiology: Community-acquired pneumonia (CAP) is one of the most

common infectious diseases. It is an important cause of mortality and morbidity

worldwide. 8th leading cause of death in US. The mortality rate is between 5% and 14%. Usually acquired via inhalation or aspiration of pulmonary

pathogenic organisms into a lung segment or lobe.

4-5 million cases annually 500,000 hospitalizations 45,000 deaths Mortality 2-30%

<1% for those not requiring hospitalization

Bacterial pathogens that cause the condition include: Streptococcus pneumoniae Haemophilus influenzae Moraxella catarrhalis (all strains penicillin-

resistant). These 3 pathogens account for approximately 85%

of CAP cases.

“Atypical” - 20-28% CAP worldwide Legionella spp, Mycoplasma pneumoniae,

Chlamydophila (formerly Chlamydia) pneumoniae, and C. psittaci

Mainly distinguished from typical by not being detectable on Gram stain or cultivable on standard media

Microbiology

MicrobiologyS. pneumoniae: 20-

60%H. influenzae: 3-

10%Chlamydia

pneumoniae: 4-6%Mycoplasma

pneumonaie: 1-6%

Legionella spp. 2-8%

S. aureus: 3-5%Gram negative

bacilli: 3-5%Viruses: 2-13%

40-60% - NO CAUSE IDENTIFIED

2-5% - TWO OR MORE CAUSES

Community Acquired Pneumonia

Symptoms: cough, purulent sputum which may be blood-stained or rust- coloured, breathlessness, fever, malaise.

Diagnosis is unlikely if there are no focal chest signs and heart rate, respiratory rate and temperature are normal.

The elderly may present with mainly systemic complaints of malaise, fatigue, anorexia and myalgia.

Young children may present with nonspecific symptoms or abdominal pain.

Signs: tachypnoea, bronchial breathing, crepitations, pleural rub, dullness with percussion.

Presentation

Pleural effusion is usually sterile; a reactive effusion can occur but is trivial.

Empyema is potentially more serious and presents as the persistence of fever and leukocytosis after 4-5 days of appropriate antibiotic therapy.

Lung abscess: can occur in disease due to S. pneumoniae and is classically seen in patients with klebsiella or staphylococcal pneumonia.

Pneumatocele.

Pneumothorax Pyopneumothorax - e.g.,

following rupture of a staphylococcal lung abscess in the pleural cavity.

Deep vein thrombosis. Septicaemia, pericarditis,

endocarditis, osteomyelitis, septic arthritis, cerebral abscess, meningitis (particularly in pneumococcal pneumonia).

Postinfective bronchiectasis.

Acute kidney injury.

CAP-associated complications: Complications depend on the infecting pathogen and patient health

Empyema can occur with Streptococcus pneumoniae, Klebsiella pneumoniae, and group A streptococcal CAP.

Cavitation is not a feature of pneumococcal pneumonia, but is a normal part of the disease process in K pneumoniae infections.

Myocardial infarction can be precipitated by fever due to community-acquired pneumonia (CAP).

Patients with CAP who have impaired splenic function may develop overwhelming pneumococcal sepsis, potentially leading to death within12-24 hours.

CAP-associated complications: Complications depend on the infecting pathogen and patient health

Morbidity and mortality

CAP morbidity and mortality are highest in elderly patients and in immunocompromised hosts.

Other factors that predict an increased risk of mortality in patients with CAP include the presence of significant comorbidities:

increased respiratory rate hypotension fever multilobar involvement anemia hypoxia

CAP-associated complications

Pathogenesis Formally known as

'atypical pneumonias', these are most commonly due to pulmonary infection with:

M. pneumoniae C. pneumoniae Legionella pneumophila

Epidemiology It is thought that the three

main atypical organisms might be implicated in up to 30% of CAP.

Other micro-organisms that cause similar patterns of presentation via pulmonary infection include: Chlamydophila

psittaci (exposure to birds, particularly ill ones, is a useful clue in the history).

Coxiella burnetii (presenting as Q fever).

Viral pneumonias including influenza A, severe acute respiratory syndrome (SARS), respiratory syncytial virus (RSV), adenoviridae and pneumonitis due to varicella (chickenpox pneumonitis).

Pneumonias due to atypical pathogens

Patient History:

The clinical presentation of atypical CAP is often sub- acute.

CAP due to atypical pathogens has 1 or more extrapulmonary features, which is a clue to the etiology.

Patients with Legionella pneumonia may have a productive or nonproductive cough.

Patients due to M pneumoniae or Chlamydophila pneumoniae present with a nonproductive cough.

With the exception of Legionella pneumonia, pleuritic chest pain is typically not a feature of CAP due to nonzoonotic atypical pathogens.

M. pneumoniae:  Vague and slow-onset

history over a few days or weeks of constitutional upset, fever, headache, dry cough with tracheitic ± pleuritic pain, myalgia, malaise and sore throat.

This is like many of the common viral illnesses but the persistence and progression of symptoms is what helps to mark it out.

In otherwise healthy individuals, it usually resolves spontaneously over a few weeks.

The hacking, dry cough can be very persistent.

Presentation:

Extra-respiratory features include:

Dermatological: Erythema multiforme Erythema nodosum Urticaria; Neurological: Guillain-Barré

syndrome, Transverse myelitis, Cerebellar ataxia and Aseptic meningitis

Hematological: Cold agglutinin disease Hemolytic anaemia; Joint symptoms: Arthralgia Arthritis; Cardiac: Pericarditis and Myocarditis; Rarely, may cause

pancreatitis.

Presentation:

C. pneumoniae:Gradual onset, which may show improvement before worsening again; incubation period is 3-4 weeks. Initial nonspecific upper

respiratory tract infection symptoms lead on to bronchitic or pneumonic features.

Most of those infected remain quite well or are asymptomatic.

Cough with scanty sputum is a prominent feature.

Hoarseness is a common feature.

Headache affects the majority of symptomatic sufferers.

Fever is relatively unusual.

Symptoms may drag on for weeks or months, despite a course of appropriate antibiotics.

Where it causes significant problems, this may be due to secondary infection or co-existing illness - e.g., diabetes.

Presentation:

L. pneumophila: This tends to be the

most severe of the pneumonias due to atypical pathogens.

Focal outbreaks centered around poorly maintained air-conditioning or humidification systems (although this is often noted retrospectively by public health physicians).

2-10 days' incubation period.

Initial mild headache and myalgia leading to high fever, chills and repeated rigors; non-chest symptoms often predominate early on.

Presentation:

L. pneumophila: Cough is nearly always

present, initially unproductive but may lead to expectoration later.

Dyspnoea, pleuritic pain and haemoptysis are not uncommon.

GIT upset, such as diarrhea, nausea and vomiting or loss of appetite/anorexia, may occur.

Neurological complications such as confusion, disorientation and focal neurological deficit may occur.

Arthralgia and myalgia are often reported.

Severe complications include pancreatitis, peritonitis, pericarditis, myocarditis, endocarditis and glomerulonephritis.

Presentation:

Physical Examination Purulent sputum is

caused by typical bacterial CAP pathogens.

Blood-tinged sputum may be found in patients with:• Pneumococcal

pneumonia. • Klebsiella

pneumonia. • Legionella

pneumonia.

Rales are heard over the involved lobe or segment.

If consolidation is present, an increase in tactile fremitus, bronchial breathing may be present.

Legionella pneumonia, Q fever, and psittacosis are atypical pneumonias that may present with signs of consolidation.

Consolidation is not a feature of pneumonia caused by M pneumoniae or Chlamydophila pneumoniae.

Pleural effusion Pleural effusion(usually

due to H influenzae infection), if large enough, is detectable on physical examination.

Patients with pleural effusion have decreased tactile fremitus and dullness on chest percussion.

Pleural effusion in a patient with CAP and extrapulmonary manifestations should suggest Legionella infection.

Empyema

On physical examination, empyema has the same findings as pleural effusion

Empyema is most often associated with Klebsiella, group A streptococci, and S pneumoniae.

Physical examination

Acute bronchitis Myocardial infarction Congestive heart

failure and pulmonary edema

Pulmonary fibrosis Sarcoidosis SLE pneumonitis Pulmonary drug

hypersensitivity reactions (nitrofurantoin)

Drug-induced pulmonary disease

Pulmonary embolus or infarction

Bronchogenic carcinoma

Radiation pneumonitis

Wegener’s granulomatosis

Lymphomas Tracheobronchitis

Differential Diagnosis in CAPDifferential diagnosis of (CAP) include the following:

Laboratory Tests: CXR CBC with differential BUN/Cr glucose liver enzymes electrolytes Gram stain/culture of sputum pre-treatment blood cultures oxygen saturation/Pulse oximetrey Pneumococcal and legionella urinary

antigen tests.

Community Acquired Pneumonia

Sputum for Gram stain and/or culture.

Sputum Gram stain is reliable and diagnostic if performed on a well collected specimen.

Gram stain shows few or no predominant organisms in patients with atypical CAPS.

Do not send the sputum of patients with COPD (e.g., AECB) for Gram stain or culture, because these patients invariably demonstrate a mixed or normal flora.

Blood Culture Blood cultures from all

patients with CAP upon admission, bacterial pathogens, S pneumoniae and H influenzae, are frequently positive cultures.

Immunological Studies (IgM) & (IgG)

immunoglobulin titers for C pneumoniae and M. pneumoniae if suspected.

Legionella serology if Legionella pneumonia if extrapulmonary finding is present.

Sputum Studies and Blood Culture

Chest Radiography and CT ScanningChest X-Ray

Obtain chest radiographs in all patients with suspected community-acquired pneumonia (CAP).

Patients presenting very early with CAP may have

negative findings on chest radiography.

CT Scan Obtain a computed tomography (CT) scan of the chest when an underlying bronchogenic carcinoma is suggested or

Abnormalities are not consistent with the diagnosis of pneumonia only.

Bilateral lower lobe opacities on CXR in a patient with Mycoplasma pneumoniae

Legionella Pneumonia

Chest X-Ray Atypical Pneumonia

Diagnosis: Other testingUrinary antigen tests

S. pneumoniae & L. pneumophila serogroup 1

50-80% sensitive, >90% specific in adults

Pros: rapid (15 min), simple, can detect Pneumococcus after abx started

Cons: cost, no susceptibility data, not helpful in patients with recent CAP (prior 3 months)

Severity of CAP RR > 30 PaO2/FiO2 < 250, or PO2 < 60 on room air Need for mechanical ventilation Mulitlobar involvement Hypotension Need for vasopressors Oliguria Altered mental status

Community Acquired Pneumonia

Mild(CAP) may be treated in an ambulatory setting.

Patients with CAP who are moderately to severely ill should be hospitalized.

Direct medical efforts at supporting cardiopulmonary function while administering antibiotics for CAP.

Empiric Treatment: Monotherapy of typical

and atypical pathogens in CAP is preferred.

Avoid empiric macrolide monotherapy, because approximately 25% of S pneumoniae strains are naturally resistant .

Preferred monotherapy includes doxycycline or a respiratory quinolone.

No increased resistance is noted with extensive use.

Management CAP

Mortality from CAP is less than 1% in those well enough to be managed in the community.

The mortality rate in patients admitted to hospital is 5-10% in those not requiring intensive care unit admission, as high as

25% in intubated patients

50% in intensive care unit patients requiring administration of vasopressor

Legionella has the most severe course and may cause significant morbidity if not treated early.

A meta-analysis of patients on two different treatment regimes reported that those taking quinolones had a mortality rate of 4% and those taking macrolides had a mortality rate of 10.9%

Prognosis: