pneumococci, Neisseria, meningitis

1. By
Dr /Eman A. Abd Alrahman

2.  Pneumococci are members of upper respiratory
tract normal flora. They can cause lobar
pneumonia and its complications.
 Gram positive cocci slightly elongated and arranged in
pairs, not motile and capsulated.
 Capsules appear as unstained
hallow around the organism
in Gram stained film.
Strept pneumoniae in tissue

3.  The polysaccharide capsule is the main
virulence factor of the organism.
Cultural Characters:
 Require enriched medium e.g. blood agar.
On blood agar, gives
alpha haemolysis
or greenish discolouration due
to partial haemolysis of RBCs,
(similar to S.viridans)
Alpha hemolysis by S.
pneumoniae on blood agar

4. Strept.viridans
Pneumococci
-
+
Bile solubility
Difference between Pneumococci & Strept.viridans

5. Strept.viridans
Pneumococci
-
+
Optochin
sensitivity

6. Strept.viridans
Pneumococci
-
+
Quellung test
Quellung reaction
(Streptococcus pneumoniae)

7. Strept.viridans
Pneumococci
-
+
Inulin
fermentation
-
+
Animal
pathogenicity

8. ENTEROCOCCI
• Gram positive cocci, arranged in short chains or in pairs.
• Non motile, non-capsulated.
• No haemolysis on blood agar.
• Ferment lactose, give rose pink colonies
on MacConkey’s medium.
• Normal flora of intestine.
• It may cause urinary tract infection, endocarditis and
abdominal infection.
Strept faecalis in culture

9. The genus Neisseria includes:
1-Pathogenic: two species:
•N. gonorrhoeae Gonorrhea.
•N. meningitidis Epidemic cerebrospinal meningitis.
2- Commensals: include N.Sicca, N.subflava,…etc, are found in
mouth, throat, pharynx and vagina.
GRAM NEGATIVE COCCI
Neisseria

10. GRAM NEGATIVE COCCI
Neisseria
Morphology:
Gram negative cocci arranged in pairs with flattened adjacent
sides, (kidney shaped appearance).
Detected intracellularly in the pathological specimens
Gram stained film of pathogenic Neisseria

11. Cultural Characters:
- N.gonorrhoeae and meningitidis are fastidious organisms; grow
only on enriched media e.g. chocolate, Thayer- Martin and
modified Thayer- Martin media at 37°C, in the presence of 5-10%
Co2, Its colony is smooth, translucent and non-pigmented.
Neisseria culture on chocolate agar

12. Biochemical reactions:
•Oxidase test: All Neisseria give a positive
oxidase reaction.
•Sugar fermentation:
•N. gonorrhoeae ferments glucose only.
•N. meningitidis ferments glucose and maltose
Oxidase test

13. Laboratory diagnosis of N. meningitidis infections:
Cerebrospinal meningitis cases:
•Specimen: CSF is obtained by lumber puncture, centrifuged and
the deposit is used.
Spinal needle

14. •Direct detection:
•Gram-stained smears: showing Gram-negative diplococci
intracellular, in some pus cells.
•Direct detection of meningococcal antigen in body fluids
by latex agglutination or fluorescent antibody test.
ve ve

15. •Cultivation:
Culture on chocolate, Thayer- Martin and modified Thayer- Martin
media, incubated at 37°C in 10 -20%CO2.

16. Diagnosis of meningococcal carriers:-
•Nasopharyngeal swab is obtained and cultured on chocolate agar and
the isolated Gram negative diplococcic should be differentiated from
commensal Neisseria by using meningococcal antisera.
•Diagnosis of N.gonorrhoeae infection:
i.Specimen: urethral discharge in males and cervical swab in
females.
ii.Gram stained film showing gram negative diplococcic
intracellularly in pus cells is diagnostic in acute cases.
iii.Culture on chocolate agar, the growth is identified by oxidase
test and sugar fermentation.