COMMUNITY ACQUIRED PNEUMONIA - Important Points.pdf

This document is about community acquired pneumonia.

Included in this presentation are the definition , etiologic agents , pathophysiology and clinical features of pneumonia.

The role of sputum examination and blood culture is also mentioned.

1. COMMUNITY ACQUIRED
PNEUMONIA

2. Contents
●Definition
●Etiologic agents
●Pathophysiology
●Pathology
●Clinical features
●The role of sputum examination & blood cultures

3. What is pneumonia ?
Pneumonia is an infection of
the pulmonary parenchyma.


Pneumonia results from
●the proliferation of microbial
pathogens at the alveolar level and
●the host’s response to those
pathogens.

4. ETIOLOGIC AGENTS

6. Typical bacterial pathogens : Streptococcus pneumoniae,
Haemophilus influenzae, and (in selected patients)
Staphylococcus aureus and gram-negative bacilli such as
Klebsiella pneumoniae and Pseudomonas aeruginosa.

The “atypical” organisms : Mycoplasma pneumoniae,
Chlamydia pneumoniae, and Legionella species as well as
respiratory viruses such as influenza viruses, adenoviruses,
human metapneumovirus, and respiratory syncytial viruses.

7. Atypical organisms cannot be cultured on standard
media or seen on Gram’s stain.

Atypical organisms are intrinsically resistant to all
β-lactam agents and must be treated with a
macrolide, a fluoroquinolone, or a tetracycline.

8. CA-MRSA pneumonia is more likely in patients with skin colonization or infection
with CA-MRSA.
Enterobacteriaceae tend to infect patients who have recently been hospitalized
and/or received antibiotic therapy or who have comorbidities such as alcoholism,
heart failure, or renal failure.
Pseudomonas aeruginosa is a particular problem in patients with severe structural
lung disease, such as bronchiectasis, cystic fibrosis, or severe COPD
Risk factors for Legionella infection include diabetes, hematologic malignancy,
cancer, severe renal disease, HIV infection, smoking, male gender, and a recent
hotel stay or ship cruise.

9. Pneumonia due to Mycoplasma pneumoniae occurs more common in younger
people , but in older patients it may be cause of pneumonia severe enough to
necessitate hospitalisation.
Tuberculosis should be suspected in persons who have lived in countries where
TB is endemic , are homeless , are infected with HIV , have a history of latent
tuberculosis , or have been exposed to others with the disease.
Recent dental manipulations , sedative overdoses , seizures , alcoholism , or loss
of consciousness for any reason should raise the suspicion of anaerobic infection
caused by aspiration of oral contents.

10. PATHOPHYSIOLOGY
Pneumonia results from
●the proliferation of microbial pathogens at the alveolar
level and
●the host’s response to those pathogens.

11. How does microorganisms gain access to the lower
respiratory tract ?
➔Aspiration from the oropharynx ( Small-volume aspiration
occurs frequently during sleep ,especially in the elderly and in
patients with decreased levels of consciousness )
➔Hematogenous spread (e.g., from tricuspid endocarditis) or
➔Contiguous extension from an infected pleural or mediastinal
space.

12. The release of inflammatory markers such IL 1
and TNF
Fever
Chemokines, such as interleukin 8 and
granulocyte colony-stimulating factor, stimulate
the release of neutrophils and their attraction to
the lung
Peripheral leukocytosis and increased purulent
secretions
Inflammatory mediators released by
macrophages and the newly recruited
neutrophils create an alveolar capillary leak
resulting in alveolar filling

Radiographic infiltrate ;
Rales detectable on auscultation, and hypoxemia
Leakage of RBCS across the alveolar capillary
membrane
Hemoptysis

13. Alveolar filling
Absence of hypoxemic vasoconstriction
mediated by some bacterial pathogens
Hypoxemia
Decreased compliance due to capillary leak,
hypoxemia, increased respiratory drive,
increased secretions, and occasionally
infection-related bronchospasm
Dyspnoea

14. PATHOLOGY

15. Bacterial pneumonia has
two patterns of anatomic
distribution: lobular
bronchopneumonia and
lobar pneumonia .
Patchy consolidation of the
lung is the dominant
characteristic of
bronchopneumonia , while
fibrinosuppurative
consolidation of a large
portion of a lobe or of an
entire lobe defines lobar
pneumonia .

17. These anatomic but still classic categorizations are often difficult to apply
in individual cases because patterns overlap.
The patchy involvement may become confluent, producing virtually total
lobar consolidation; in contrast, effective antibiotic therapy for any form of
pneumonia may limit involvement to a subtotal consolidation.
Moreover, the same organisms may produce either pattern depending on
patient susceptibility.

Most important from the clinical standpoint are identification of the
causative agent and determination of the extent of disease.

19. In the first stage of
congestion the
lung is heavy,
boggy, and red.
It is characterized
by vascular
engorgement,
intra-alveolar
fluid with few
neutrophils, and
often the presence
of numerous
bacteria.

20. The stage of red
hepatization that follows
is characterized by
massive confluent
exudation with
neutrophils, red cells,
and fibrin filling the
alveolar spaces

On gross examination,
the lobe now appears
distinctly red, firm, and
airless, with a liver-like
consistency, hence the
term hepatization.

21. The stage of gray
hepatization follows
with progressive
disintegration of
red cells and the
persistence of a
fibrinosuppurative
exudate (giving the
gross appearance
of a grayish brown,
dry surface )

22. In the final stage of
resolution , the
consolidated
exudate within the
alveolar spaces
undergoes
progressive
enzymatic digestion
to produce granular,
semifluid debris that is
resorbed, ingested by
macrophages,
expectorated, or
organized by
fibroblasts growing
into it.

23. CLINICAL EVALUATION
History
Physical examination
Diagnostic testing
The probability of detecting pneumonia varies with the patient
population , the prevalence of pneumonia in that population , the
threshold values for defining a vital sign as abnormal , and the
ability of the clinician to detect abnormal physical findings.

24. SYMPTOMS
●Fever / chills / sweats
●Cough ( non productive or productive )
●Sputum production ( mucoid, purulent, or blood-tinged )
●Hemoptysis ( Gross hemoptysis is suggestive of CA-MRSA pneumonia )
●Dyspnoea
●Pleuritic chest pain
●GI symptoms ( Upto 20% of patients ; nausea , vomiting , diarrhoea )
●Fatigue / headache / myalgias / arthralgias
With increasing age , both respiratory
and non respiratory symptoms of
pneumonia become less frequent.

25. RISK FACTORS FOR CAP

-Alcoholism
-Asthma
-Immunosuppression
-Institutionalization
-Age more than or equal to
70 years
-Decreased cough and gag
reflexes in elderly
-Reduced antibody and Toll
like receptor responses in
elderly
RISK FACTORS FOR
PNEUMOCOCCAL PNEUMONIA

-Dementia
-Seizure disorders
-Heart failure
-Cerebrovascular disease
-Alcoholism
-Tobacco smoking
-COPD
-HIV infection

26. PHYSICAL EXAMINATION
Fever ( 65 - 95 % of patients with pneumonia can have fever )
Tachycardia
Tachypnoea
Cyanosis
Use of accessory muscles of respiration , chest retraction , nasal flaring
Splinting ( an inspiratory lag on the side of the lesion ) is highly
suggestive of bacterial pneumonia.

27. Palpation may reveal increased or decreased tactile fremitus, and the
percussion note can vary from dull to flat, reflecting underlying
consolidated lung and pleural fluid, respectively.

Crackles, bronchial breath sounds, and possibly a pleural friction rub may
be heard on auscultation.
Evidence of consolidation ( dullness on percussion , bronchial breath
sounds , aegophony ) is highly suggestive of bacterial pneumonia but
may be absent in two third of patients ill enough to be hospitalised and
may be absent more often in patients treated as outpatients.

28. Patients with mycoplasma , pneumocystis , tuberculosis or viral
infection may exhibit few abnormalities at physical examination despite
the presence of impressive images on chest imaging.
Rare findings such as egophony and asymmetrical chest movements
have a high predictive value for pneumonia , but occur so infrequently
that they are of limited usefulness.
The absence of any vital sign abnormalities has been associated with
less than 1% chance of a patient having pneumonia , assuming a
pneumonia prevalence of 5% in the population under study.

29. ATS / IDSA 2019 Clinical Practice Guidelines

In Adults with CAP, Should Gram Stain and Culture of
Lower Respiratory Secretions Be Obtained at the Time
of Diagnosis?

30. We recommend obtaining pretreatment Gram stain and culture of respiratory secretions in
adults with CAP managed in the hospital setting who:
1. are classified as severe CAP , especially if they are intubated; or
2.
a. are being empirically treated for MRSA or P. aeruginosa
b.were previously infected with MRSA or P. aeruginosa, especially those with prior
respiratory tract infection; or
c. were hospitalized and received parenteral antibiotics, whether during the hospitalization
event or not, in the last 90 days

We recommend not obtaining sputum Gram stain and culture routinely in adults with
CAP managed in the outpatient setting .

31. The main purpose of the sputum Gram’s stain is to ensure that a sample is
suitable for culture. However, Gram’s staining may also identify certain pathogens
(e.g., S. pneumoniae, S. aureus, and gram-negative bacteria) by their
characteristic appearance.

To be adequate for culture, a sputum sample must have >25
neutrophils and <10 squamous epithelial cells per low-power field.

32. ATS / IDSA 2019 Clinical Practice Guidelines



In Adults with CAP, Should Blood Cultures Be Obtained at the
Time of Diagnosis?
We recommend not obtaining blood cultures in adults with CAP
managed in the outpatient setting .


We suggest not routinely obtaining blood cultures in adults with CAP
managed in the hospital setting.

33. We recommend obtaining pretreatment blood cultures in adults
with CAP managed in the hospital setting who:

1. are classified as severe CAP ; or

2.
a. are being empirically treated for MRSA or P. aeruginosa ; or
b. were previously infected with MRSA or P. aeruginosa,
especially those with prior respiratory tract infection ; or
c.were hospitalized and received parenteral antibiotics, whether
during the hospitalization event or not, in the last 90 days

34. REFERENCE
1.Harrison’s Principles of Internal Medicine , 21st edition

2.Robbins & Cotran Pathologic Basis of Disease , 10th
edition

3.ATS IDSA CAP Guidelines 2019