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Course: Clinical Analysis
Lecturer: Dr. Weam Saad
Lecture: Sputum Analysis
Sputum
Analysis
Sputum is the matter that coughed up from the airways through
the mouth, containing mainly saliva mixed with mucus or discharge;
the best sputum samples contain very little saliva in order to avoid
contamination with oral normal flora. Sputum sample is used for the
diagnosis of respiratory tract infections like pneumonia. It is
obtained by coughing deeply and expelling the material that comes
from the lungs into a sterile cup.
The sputum may have a thick consistency (viscous), appear
discolored, yellow, green, gray, rarely rusty or bloody, and may have
an unpleasant odor (especially during bacterial respiratory
infections). Moreover pus, it may contain WBCs, cellular debris,
epithelial cells from mouth.
Types of sputum:
1- Bloody sputum: occurs when sputum mixed with blood e.g.
cases of tuberculosis, lung abscess and lung cancer.
2- Rusty sputum: usually caused by pneumococcal bacteria.
3- Purulent sputum: containing pus. The color can be yellow,
green or pink depending on the causative pathogen.
There are only two tests ordered for this sample:
1. Sputum smear
2. Sputum culture
1. Sputum smear
Sputum smears examining after staining with Gram stain, Acid
fast stain and others. The pathogenic microorganisms will be
diagnosed. Gram stain and acid fast stain methods are most
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common used after doing thin smear and stained with gram stain
just like any bacterial smear.
2. Sputum culture
A sputum culture is ordered when a doctor suspects that a
person has a bacterial infection of the lungs or airways, such
as bacterial pneumonia, which may show as changes in the lungs as
seen on a chest x-ray. The sputum sample is taken and placed in a
medium and incubated to let organisms grow. A positive culture
may identify disease causative organisms that may help diagnose
bronchitis, tuberculosis, a lung abscess, or pneumonia. If pathogenic
bacterial growth identified during a sputum culture, then
antimicrobial susceptibility test is usually performed so that the
appropriate antibiotics can be prescribed.
The most common pathogens isolated from respiratory tract
infections sputum culture include:
Bacteria
Mycobacterium tuberculosis (tuberculosis)
Streptococcus pneumoniae (pneumococcus).
Staphylococcus aureus
Haemophilus influenzae
Moraxella catarrhalis
Klebsiella pneumoniae
Streptococcus pyogenes
Chlamydia pneumonia
Legionella species
Fungi
Cryptococcus neoformans
Viruses and parasites cannot be isolated during routine
culture for sputum samples.
The Normal flora that can contaminate sputum culture may be
bacteria e.g. Streptococcus viridans, Staphylococcus epidermidis and
fungi e.g. Actinomycetes.