1. Illustrate the microscopic morphology of corynebacteria:

Coli Blood Agar

2. Describe the appearance of a Corynebacterium species on blood agar.

3. Describe the appearance of E.coli and of a Corynebacterium species on blood tellurite agar.

4. Complete the following table.

Name of Organism




C. xerosis

C. pseudodiphtheriticum

C. diphtheriae

Morello-Mizer-Granato: I III. Diagnostic I 8. Microbiology of the I I © The McGraw-Hill

Laboratory Manual and Microbiology in Action Respiratory Tract Companies, 2003 Workbook in Microbiology, 7/e

EXPERIMENT 22.3 Bordetella

Bordetella pertussis is the etiologic agent of whooping cough. This very fastidious organism grows best on special media. The two most common are Bordet-Gengou (BG) agar, which is enriched with glycerin, potato, and 30% defibrinated sheep blood, and Regan-Lowe (RL) agar, which consists of charcoal agar, defibrinated horse blood, and an antimicrobial agent to inhibit growth of normal respiratory flora. The charcoal is present to adsorb toxic substances that might be present in the agar. Visible colonies are produced only after three to five days incubation in a microaerophilic atmosphere. On BG medium, the colonies are raised, rounded, and glistening (resembling mercury droplets or a bisected pearl), and usually have a hazy zone of hemolysis. On RL medium, the colonies are round, domed, shiny, and may run together slightly.

B. pertussis is a gram-negative bacillus resembling Haemophilus species, with which it was once classified. When whooping cough is suspected, the best specimen for laboratory diagnosis is a nasopharyngeal swab, but throat swabs may be used in addition.


To observe Bordetella pertussis in demonstration and to examine a throat culture on Bordet-Gengou (BG) and Regan-Lowe (RL) media


Prepared Gram stains of B. pertussis

Projection slides, if available

Bordet-Gengou and Regan-Lowe agar plates

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  • Erik
    What is the appearance of escherichia coli?
    8 years ago

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