Gram Negative Aerobic Nonsporulating Nonmotitile Oxidase-negative Paired cocci

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