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Meningococcus;Diplococcus intracellularis meningitidis It causes meningococcal meningitis(cerebrospinal fever) Morphology ;
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Gram NegativeAerobicNonsporulatingNonmotitileOxidase-negativePaired cocci
NEISSERIA
Two important pathogens,
Neisseria meningitidisNeisseria gonorrhoeae andNeisseria lactamica(rare speceis)
Neisseria meningitidis
Meningococcus;Diplococcus intracellularis meningitidis
It causes meningococcal meningitis(cerebrospinal fever)
Morphology;
Do not grow on ordinary media Media enriched with blood,serum or ascitic
fluid which promote growth by neutralising inhibiting substances
No growth occurs anaerobically Optimum temp;35-36degrees Optimum ph;7.4-7.6 Growth is facilitated by 5-10% CO2 &high
humidity
Cultural characteristics
On solid media colonies are Small, Translucent, Round, Convex, Bluish grey
with glistening surface and entire edgesWeak hemolysis on blood agar
Commonly used media,a. Blood agarb. Chocolate agarc. Muller-Hinton starch casein hydrolysate
agar. Selective medium;Modified Theyer-
Martin(with vancomycin,colistin and nystatin)
Catalase-positiveOxidase-positiveIn kovac’s method-deep purple colour
appears immediately.Indole &Hydrogen sulphide-Not Produced,Nitrates-not reduced
BIOCHEMICAL REACTIONS
Sugar fermentation
Based on capsular polysaccharide antigens,classified into 13 serogroups……
A,B&C-Most important.groupA-EPIDEMICSgroupB-LOCALISED OUTBREAKSgroupC-BOTHGroups 29-E,W-135 &Y:causes MENINGITIS
ANTIGENIC PROPERTIES & CLASSIFICATION
Very delicate organismsHighly susceptibleSensitive to penicillin &other antibioticsBut resistant strains have emerged
RESISTANCE
Two main types of meningococcal diseases, 1.cerebrospinal meningitis& 2.meningococcal septicemia.Strict human parasites inhabiting the
nasopharynxAsymptomatic infectionLocal inflammation-rhinitis&pharyngitis
PATHOGENICITY
cocci from nasopharynx cribriform plate to subarachanoid space meninges suppurative lesions
surface of spinal cord,
base&cortex of the brain spinal fluid
Cocci are found both free & with in leucocytes
in the spinal fluid.Fatality high in untreated cases(80%)Survivors may have blindness&deafnessChronic or reccurent meningitis
MENINGOCOCCEMIAAcute fever with chillsMalaise &Prostration.Metastatic involvement of joints, ears, eyes, lungs & adrenals may
occur10%-pneumonia.
Fatal condition,ShockDisseminated intravascular coagulation&
Multisystem failurePathogenic agent-ENDOTOXIN released by autolysis
Vascular endothelium is sensitive to endotoxin
FULMINANT MENINGOCOCCEMIA(Waterhouse-Friderichsen syndrome)
Specimens collected, 1.spinal fluid 2.blood 3.swabs from nasopharynx.1.Examination of CSF:-collected csf is devided
into 3 parts. a)1st portion-centrifuged & gram stained
smears are prepared from deposits, supernatant-meningococcal antigens
LABORATORY DIAGNOSIS
B)2nd portion-inoculated on blood or chocolate agar
imp note-morphologically similar organisms.c)3rd portion-over night incubation, subcultured on chocolate agar.2.BLOOD CULTURE3.NASOPHARYNGEAL SWAB4.PETECHIAL LESIONS5.AUTOPSY6.RETROSPECTIVE EVIDENCE7.MOLECULAR DIAGNOSIS.
SulphonamidesIv penicillinGChloramphenicolCephalosporinsEradicative therapy-Rifampicin or
ciprofloxacin
TREATMENT
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