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Neisseria Meningitides
Neisseria Meningitides
-One of the most commonly caused Bacterial meningitis.
-Neisseria group are part of the normal flora of the oropharynx, nasopharynx and genitourinary tract.
-Meningitis is spread by direct contact and droplet infection through secretions of the upper respiratory tract.
-It is most common among children 3 months – 5 years old and among adolescents and young adults.
There is a three step process before meningitis is acquired:
-First the meningococci multiplies in the nasal passage and throat which gives no painful symptoms.
-Then it invades the blood introducing toxins which causes fever and sometimes rashes (meningococcemia).
– Lastly the meninges are infected causing intense inflammation and exudation of pus.
Signs & symptoms of meningitis include:
1-neck rigidity . 2-severe headache 3-cerebrospinal fever 4-irritability 5-hyperreflexia .6-photophopia .7- increase in cerebrospinal fluid cause increase in intracranial pressure that leads to : Diplopia ,nausea & vomiting.
The disease can be mild or sever (patient in coma ).
specimen:
CSF taken by lumber puncture using sterile needles because the subarachnoid space is sterile .
Then 3-5 ml of CSF is taken .before taking CSF, we examine the fundus that indicate the intracranial pressure if the intracranial pressure is high we avoid rapid decrease in it. in meningitis the CSF is turbid .
in some viral meningitis it is clear . its normally clear .
diagnosis:
meningitidis is a Gram-negative, coffee-bean shaped diplococcus. –
– microscopy
:
In CSF we count WBCs total& differential .in meningococcal meningitis , the WBCs are 500-10,000 cell/cu ml ,mostly are polymorph s .where as in viral meningitis are mostly lymphocyte.
Then we centrifuge the CSF (because the organisms are few ). We tack the deposit & make smears and stain by gram stain .we see( gram – ve )diplococcic inside the polymorph . normally ,no polymorphs are present in the CSF.
-from the deposit we do culture . CSF can grow in chocolate agar .incubate at 37° C in 5-10% co2 .after 18-24 hours we examine the shape the colonies are very smooth .
– API NH is used for identification
– oxidase test (+ve) & sugar utilization (glucose & maltose +ve ).
– we can do serogrouping by specific antiserum . in epidemics we do serotyping & serogrouping.
Twelve serogroups, based on capsular polysaccharides, are currently recognized: A, B, C, H, I, K, L, W135, X, Y, Z, and Z’ (29E).
*Important complication:
Waterhouse Frederickson syndrome a fatal form of meningococcemia characterized by DIC & hemorrhage .the pt die due to acute circulatory collapse due to adrenal hemorrhage .
Neisseria Meningitides
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