Neisseria

Neisseria:

The genus N. is G –ve diplcocci, non motile, oxidase +ve, grow well at aerobic conditions and some spp. are facultative anaerobes. 5% CO2 enhance the growth of N., catalase –ve, some spp. are capsulated and others are not. N. spp. are very fastidious in their growth, the pathogenic N. of 2 main spp.:
1. Neisseria gonorrhoeae (Gonococcus) causes “gonorrhoea”.
2. Neisseria meningitidis (Meningicoccus) causes “Meningitis”.
Both of them associated with or inside poly morphonuclear cells (Neutrophils).
Lab. Diagnosis:
1. Specimens: Include material from genital sources like uretheral, vaginal discharge [creamy yellowish color] and extra genital eg. skin, blood.
2. Direct stain: Gram stain is made to the specimens above and will show G –ve, diplococcic, non capsulated by (capsular stain).
3. Culture: N. is fastidious grows on enriched media like chocolate agar and the selective one is Thayer Martin medium which comprises of the following:
- Chocolate agar (heated blood agar).
- Antibiotics:
1. Vancomycin inhibit the growth of G +ve.
2. Colistin inhibit the growth of G –ve.
3. Nystatin yeast inhibit the growth of yeasts.
4. Trimethoprim may be added to Thayer Martin medium to inhibit the swarming of Proteus. This is called “modified Thayer Martin”, incubation at 35-37?C for 24-48 hr., 5% CO2 will enhance the growth. Growth culture can not grow at temp. below 22?C, the colonies are non hemolytic, gray to white in color.
Lab. Diagnosis of Neisseria meningitidis:
1. Specimens: Meningitis is the infection of meninges which may be due to bacteria N. meningitidis (Streptococcus pneumonia and H. influenzae) or viral (polio, Herpes simplex) or may be fungal (candida).