Greenish tint implies Pseudomonas as the etiologic agent.

Rust colored sputum is due to decomposed hemoglobin

and is seen in pneumococcal pneumonia or pulmonary

gangrene, whereas a bright red sputum is found in recent

hemorrhage which can follow acute cardiac infarction,

pulmonary infarction, neoplasm invasion and rupture of

a vessel.

Odor: Normal sputum is odorless. Suppurative pulmonary

disorders such as lung abscesses, cavitary tuberculosis

or gangrene produce most putrid odors. A ruptured

subphrenic or liver abscess may impart a fecal odor.

Other Findings

1. Cheesy masses: Fragments of necrotic pulmonary

tissue seen in pulmonary gangrene or tuberculosis.

2. Bronchial casts: These are branching tree-like casts

of bronchi and their size depends upon the size of

bronchi from which they have been expectorated.

These can be seen in untreated lobar pneumonias,

fibrinous bronchitis. To recognize these casts, they

have to be floated on water against a black background.

3. Broncholiths (lung stones): These are formed due to

calcification of necrotic/infected tissue within a larger

bronchus or cavity. The central core of these may be

a foreign body or a fungus growth. Though rare, but

when seen, chronic tuberculosis should be kept in

mind.

4. Dittrich’s plugs: They are seen in putrid bronchitis and

bronchiectasis. When expectorated, they are usually

solitary of a variable size. When crushed, they are

found to be made of cellular debris, fatty acid crystals,

fat globules, and bacteria. These plugs are seen most

commonly in chronic bronchitis, bronchiectasis and

bronchial asthma.

5. Foreign bodies: These are usually objects inhaled by

a child. Usually, substances inhaled are peanuts and

buttons. Radiologically, they are difficult to see.

6. Parasites: Various parasites that can be seen in sputum

are Ascaris lumbricoides, Echinococcus granulosus,

Toxocara canis and Paragonimus westermani.

Microscopic Examination

Having done the macroscopic examination, transfer

the suspicious looking particles to a clear slide and

examine unstained if necessary (one may come across

Curschmann’s spirals, elastic fibers, fungus and myelin

globules). The remaining portion of the sputum is cultured.

Smears made on clear slides should be air dried, fixed

over a flame and then stained with Gram’s stain/ZiehlNeelsen stain. Wright’s stain can be done for blood cells

and buffered crystal violet for epithelial cells. Pap’s stain is

best for studying cytology of sputum (Fig. 14.1).

If cells characteristic of the bronchopulmonary tree

are not seen—consider the specimen as inadequate and

discard it even for culture. The presence of squamous cells

signifies the specimen as being more representative of the

oral cavity than the bronchopulmonary tree.

The basal cells are about the size of a lymphocyte with

scanty cytoplasm. Columnar bronchial epithelial cells

may or may not be ciliated, the nonciliated ones are of

the goblet type. The presence of alveolar macrophage is

the best indication that the material being examined has

arisen from the lower respiratory tract, these cells often

show anthracotic pigment which is not of any significance.

Blood cells are best seen by the usual peripheral

smear stains. Neutrophils predominating imply an acute

pyogenic infection, lymphocytes are predominant in

tuberculosis and eosinophils are usually seen in bronchial

asthma. Erythrocytes in large numbers indicate exudation

or hemorrhage.

Sputum Culture

Each specimen received should be plated on blood agar,

chocolate agar, MacConkey’s agar and thioglycollate broth.

COMMON RESPIRATORY DISORDERS

Mycobacteria

A culture should always be performed in a previously

undiagnosed case of respiratory tuberculosis. In a

fulminant form, the sputum is mucopurulent and shows

RBCs, caseous and necrotic materials. Elastic fibers in the

necrotic tissue indicate pulmonary tissue destruction (e.g.

blood vessels; alveoli and bronchi from which they can be

derived) and can be seen in abscesses, bronchiectasis, or

malignancy. Most often, they are seen in advanced cases of

tuberculosis. Within the caseous material, acid-fast bacilli

(AFB) can usually be demonstrated. Sputum induction

gives a higher recovery rate of tubercle bacilli. The slides

can be stained with auramine-rhodamine (AR) stain and/

or Ziehl-Neelsen (ZN) stain. AR stain shows nonviable

Sputum Examination 407

bacilli also (ZN does not); so for prognostic evaluation, all

AR positive specimens should be stained with ZN also. AR

staining is superior to ZN because:

a. AFB have more affinity for AR dye

b. The entire smear can be screened as the low power

(X 10) objective is used, and

FIG. 14.1: Microscopic structures that may be seen in sputum

408 Concise Book of Medical Laboratory Technology: Methods and Interpretations c. The black background in fluorescent microscopy

makes the bacilli stand out sharper to allow more rapid

and accurate slide screening.

Mycotic (Fungal) Disease

Respiratory fungal disease often mimics either

inflammatory or neoplastic disease in clinical symptoms

and X-ray findings. A first morning specimen is

preferred as it represents the overnight secretions of the

tracheobronchial tree. Place the specimen in a sterile

container and view against a dark background. Fungi are

usually seen as tiny flecks or particles, which appear yellow

or gray in color and more dense than the surrounding

sputum.

Make a direct mount with 10% sodium hydroxide and

examine under low and high power. If no fungi are seen,

the specimen can be concentrated by using 4% NaOH or

the enzyme pancreatin. Confirm microscopic finding by

cultures.

Pathological Fungi

Actinomyces israelii

Not a true fungus,