محاضره Niesseria

GRAM NEGATIVE DIPLOCOCCI
GENUS: NEISSERIA
Characteristics:
. They are none-motile, gram-negative intracellular diplococcic
. Rapidly killed by drying, sunlight, heat, and disinfectants
. Ferment carbohydrate producing acid but not gas
. Each cocci is kidney-shaped with adjacent concave sides
. Grow best on complex media under aerobic conditions containing
5%co2
. Oxidase positive.
. The main species of medical importance are:
N. meningitidis
N.gonorrhoea.
N. gonorrhoea
Characteristics:
An obligate parasite of the human urogenital tract.



Neisseria gonorrhoea



Laboratory diagnosis:
Specimen: Urethral swab, cervical swab, eye swab
Smear: Gram-negative intracellular diplococci
Culture: Requires an enriched media like chocolate agar or thayer-martin agar.
. Grows best in CO2 enriched aerobic atmosphere with optimal temperature of 35-37Oc.
.Fastidious- Dies with exposure to sunlight, room temperature and drying.
. Small glistening colonies.
.Culture of urethral exudate from men are not necessary when the gram stain is positive but culture should be done for women

Biochemical reaction:
Oxidase positive.
Ferment only glucose in carbohydrate utilization test

Neisseria meningitidis
Characteristics:
• Gram-negative intra cellular diplococci.
• Present in the nasopharynx in 5-10% of healthy people.











Neisseria meningitidis


Laboratory diagnosis:
Specimen: Cerebrospinal fluid, blood
Smear: Gram-negative intracellular diplococci
Culture: Transparent or grey, shiny, mucoid colonies in chocolate
agar after incubation at 35-37Oc in a CO2 enriched atmosphere.

Biochemical reaction:
Oxidase positive.
Ferment glucose and maltose in carbohydrate utilization test.



Comparison features of N.gonorrhea and N.meningitidis
Features N.gonorrhea N.meningitides
. Site of infection . Urethra/cervix . Meninges
. Route of infection . Sexual . Inhalation
.Disease . cervicitis. . Meningococcemia
. Specimen of choice .Urethral/Cervical swab .Cerebrospinal fluid
. Biochemical reaction .Oxidase positive .Oxidase positive
. Ferment glucose only . Ferment glucose
and maltose