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Sputum Culture. Aim of the test. An etiological diagnosis of lower respiratory tract infection by microscopic examination and culture with identification and susceptibility test of the isolated organism.
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Aim of the test An etiological diagnosis of lower respiratory tract infection by microscopic examination and culture with identification and susceptibility test of the isolated organism. Types of specimen: Sputum, Transtracheal aspirates, translaryngeal aspiration, bronchoalveolar lavage .
Specimen collection Patient preparing: patient is asked to wash oral cavity by gargling (normal saline) with water 3-4 times. Deep cough and collect sputum in a wide mouth sterile container. All expectorated sputum is contaminated to some degree with secretion of the oropharyngeal cavity, which contains a wide variety of commensal bacteria, some of which are potential pathogens of the lower respiratory tract (S. pneumonia, H. influenzae). Contamination oropharyngeal secretion should be kept to a minimum
Early morning sputum is preferred because they contain pooled overnight secretion in which, pathogenic bacteria are more likely to be concentrated. The specimen should be collected in a sterile, wide-mouth container with tightly fitted screw-cap.
Aim of the test • Isolate and identify group A beta-hemolytic streptococci; establish the diagnosis of strep throat infection. • Types of specimen • Material from posterior pharynx, tonsils, or other inflamed area.
Specimen collection • Both tonsillar pillars and the oropharynx should be swabbed. • Do not allow the to touch the tongue. • The patient is instructed to tilt his/her head back and breath deeply. • The tongue is gently depressed with a tongue blade to visualize the tonsillar fossa and posterior pharynx. • The swab is extended between the tonsillar pillars and behind the uvula, care should b taken not to touch the lateral walls of the buccal cavity or the tongue to minimize contamination with commensal bacteria. • After collection, the swab should be placed immediately into sterile tube or other suitable container for transport to the laboratory.
Specimen processing • Media • Blood Agar • Columbia CNA • Selective media which selects for Gram-positive bacteria. • It contains two antibiotics, colistin and naladixic acid which inhibit the growth of gram-negative bacteria, thus selecting for Gram-positive organisms • Culturing procedure • Streak the swab across blood agar plate and Columbia CNA to make a line that divide the plate into two halves, and using a sterile loop, streak by crossing the line to produce isolated colonies. Make few stabs in the agar. • Do a gram stain from the swab noting the predominant organism.
Turn around time • Gram stain results should be available 1 hour after specimen receipt. • Isolation of a possible pathogen can be expected after 2-3 days. • Negative culture will be reported out 1-2 days after the receipt of the specimen.