in this ppt you will know more about the bacterial causes of meningitis this include its stain ,describtion on culture special media& biochemical reactions
4. Most Common Bacterial Causes Of Meningitis
1. Neisseria meningitidis
2. Streptococcus pneumoniae
3. Streptococcus agalactiae (Streptococcus Group B)
4. Escherichia coli
5. Hemophilus influenza
6. There are four reagents used in gram staining:
1-A primary ( basic) stain: crystal violet.
2-a trapping agent (mordant): gram’s iodine.
3-a decolorizing agent: 95% alcohol or acetone-alcohol
4-a counterstain: safranin.
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9. CULTURE MEDIA:
• Name : chocolate agar
• Type: enriched medium
• Use: culture of fastidious organisms e.g.
Neisseria spp &
Haemophilus spp.
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On chocolate agar : Neisseria meningitidis appear as greyish white ,glistening ,
convex colonies
12. Composition:
• Chocolate agar has been modified to be selective for neisseria spp by
adding of antibiotics:
Colistin : inhibition of gram negative bacteria
Vancomycin : inhibition of gram positive bacteria
Nystatin: inhibition of fungi
• Modified Thayer martin : trimethoprim to inhibit proteus
• Nitrogenous nutrients such as casein to neutralize toxic fatty acids .
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19. Streptococcus pneumoniae
• Microscopic appearance: gram-positive, lancet-shaped, diplococci (arranged
in pairs), but they may also occur in short chains
20. • Culture media :
● Blood agar :
colonies grow on blood agar and
surrounded by αlpha - haemolysis.
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21. QUELLUNG TEST
(CAPSULE SWELLING TEST)
This method involves testing a pneumococcal cell suspension with specific antisera directed against
the capsular polysaccharide
The antigen-antibody reactions are observed microscopically
A positive quellung reaction is the result of the binding of the capsular polysaccharide of pneumococci
with type specific antibody contained in the typing antiserum (Strept.pneumoniae)
A positive quellung reaction is observed when the capsule appears as a halo (swollen capsule) around
the bacterial cell
30. MaCconkey agar
• Type: differential selective medium
• Use: cultivation of enteric bacteria and
differentiation between two major groups of
enteric bacteria:
(1) lactose fermenting bacteria:
• Give pink colonies.
• E.G. E. Coli, klebsiella.
(2) lactose non-fermenting bacteria:
• Give pale colonies.
• E.G. Salmonella, shigella, and proteus.
31. 2) INDOLE TEST
Principle:
The test determines the ability of the
organism to produce indole from the
breakdown of the amino acid tryptophan.
Addition of Kovac’s reagent which acts
with indole gives a red color
Results and interpretation:
A positive result is indicated by the
presence of a red color in the layer on the
surface of the broth. A negative
result appears in yellow.
Example:
E.coli
Example:
Shigella
33. • Culture on chocolate agar
• Type: enriched media
• Use: culture of fastidious organisms as
neisseria and haemophilus
34. • CULTURAL CHARACTERS:
• H.influenza is a fastidious, facultative anaerobic organism which grows best at
35-37°C with ~5% CO2 (or in a candle-jar) and requires hemin (X factor) and
nicotinamide-adenine-dinucleotide (NAD, also known as V factor) for growth.
• The standard medium used for growth of h. Influenzae is a chocolate agar plate
which can be prepared with heat-lysed horse blood, a good source of both hemin
and NAD.
• Growth occurs on a chocolate agar because NAD is released from the blood during
the heating process of chocolate agar preparation (the heating process also
inactivates growth inhibitors) and hemin is available from non-hemolyzed as well
as hemolyzed blood cells.
35.
36. • H.INFLUENZA REQUIRES BOTH X AND V FACTORS FOR GROWTH.
• In this culture, H.Influenza has only
Grown around the paper disc that has
been impregnated with both
X and V factors.
• There is no bacterial growth
Around the discs that only
contain either X or V factor
40. Bacteriological Loop
• Use: inoculation of bacteria on
culture media
• Method of sterilization:
dry heat (red heat) by heating
in the bunsen flame till it turns
red hot.