MICROBIOLOGY 101 LABORATORY MANUAL

EXERCISE #19: NEISSERIA

NAME, ID #:_______________________________________________.

REVISED: 08/04/99

INTRODUCTION

The Neisseria are a group of small G-, aerobic, oxidase positive, elongated diplococci (coffee-bean shaped) that include a number of important pathogens as well as numerous harmless forms usually found in the human respiratory tract. They are generally difficult to grow, needing rich medium and an atmosphere rich in carbon dioxide. Among the important diseases they cause are N. gonorrhocea (the STD, gonorrhea) and N. meningitidis (epidemic meningitis). The nasopharynx forms are spread by water droplets between hosts, but they are generally easily killed outside their hosts.

PURPOSE OF LABORATORY:

1. To isolate Neisseria bacteria from the human body.
2. To learn about the Neisseria normally found on/in the human body.

RELATIONSHIP TO LECTURE MATERIAL

• NetText: CHAP. XIV

GENERAL INSTRUCTIONS:

1. Please place all appropriately labeled drawings in the circles so the instructor can identify them.

PROCEDURE:

1. Read pg. 25, 71 & 134 in A Photographic Atlas for the Microbiology Laboratory.
2. Obtain a plate chocolate blood agar (CBA). It is called that because during its preparation the blood is lysed and its reaction with the air produces a brown, chocolate-like pigmentation.
3. Obtain a sterile tongue depressors and swabs.
4. Each partner will swab the back of the other partner's throat while holding down the tongue.
5. Swab the sample on a corner of the appropriate chocolate agar plate and spread for isolation.
6. Incubate the pates at 37^oC until the next lab.
7. Examine the CBA plates for the following colony types:
   1. Yellow or gray = N. sica and mucosa
   2. Yellow, wrinkled colonies = N. subflava
   3. Pinkish gray = N. catarrhalis
   4. Mucoid and raised = N. meningococci.
8. Carry out the gram stains on suspected colonies. Remember to run your G+ and G- controls. Draw what you see.
9. Carry out the oxidase test on the same suspected colonies.
10. Flood the plate with the oxidase reagent (DANGER: TOXIC). Look for colonies that turn maroon to dark red to black. The oxidase test measures the presence of an enzyme system (indole-phenol oxidase) that is the final electron acceptor to oxygen.
11. Prepare a table indicating your results of the various observations and your conclusion as to the identity of each of the colonies. Indicate the results of the oxidase test. The Pseudomonads are also common oxidase positive bacteria, but they are G- rods .
12. Click here to see a discussion of this bacterial group.

ADDITIONAL INFORMATION ON NEISSERIA AND THE DISEASES THEY CAUSE

http://129.109.136.65/microbook/ch014.htm; Excellent medical information on GC and NM.

SAMPLE QUESTIONS: You should be able to answer these questions at the conclusion of this laboratory.

• What is the gram reaction of the Neisseria.
• Name two important diseases caused by Neisseria species. Hint: the NW has had several deadly cases of one type recently.
• Describe how the nasopharynx strains are passed between hosts.
• How does the oxidase test work and what does it detect?
• What is "chocolate agar"?

Copyright © Dr. R. E. Hurlbert, 1999.
This material may be used for educational purposes only and may not be duplicated for commercial purposes.
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E-mail address: hurlbert@wsu.edu or hurlbert@pullman.com 

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