for mbbs 2nd prof

1. NEISSERIA MENINGITIDIS
(MENINGOCOCCUS DIPLOCOCCI)
MORPHOLOGY –
- Gram negative
- Spherical or oval cocci
- 0.6 to 0.8 um in size
- Non motile
- Arranged in pair with adjacent sides flattened
CULTURE –
- Growth occur in media enriched with blood or serum
- Strict aerobes
- Temp – 35 – 36 degree
- pH – 7.4 – 7.6
- Colony – small (1mm), round, convex, grey, translucent with entire edges
- Chocolate agar is commonly used
- used for isolation.
BIOCHEMICAL REACTION –
- Catalase – Positive
- Oxidase – Positive
- Glucose & Maltose r fermented with acid production but no gas.
- H2S or idole are not produced
- Nitrates are not reduced
PATHOGENESIS –
- It causes pyogenic meningitis in all ages but is most common in children and young
adults.
- Meningococcaemia presets as acute fever with petechial rash.

2. LAB DIAGNOSIS –
- Specimen – CSF, blood, nasopharyngeal swab, petechial lesion.
- Collection & transport – collect under sterile container & transport immediately.
- Direct microscopy & antigen detection – see morphology (puss cell seen)
- Culture, morphology, gram staining, colony – see above
- Biochemical reaction – see above
- Slide agglutination
- Serological diagnosis
- PCR
TREATMENT – Penicilin, chloramphenicol.
NEISSERIA GONORRHOEAE
It causes the sexually transmitted disease, Gonorrhoeae.
MORPHOLOGY –
- Gram negative
- Diplococci (pear or bean shaped)
- Non motile
CULTURE –
- Aerobic may grow anaerobic as well.
- Temp – 35 – 36 degree
- pH – 7.4 – 7.6
- Require enriched media to grow
- Selective media – Thayer martin media
- Chocolate agar is used
- Colony – small, round, convex, grey, translucent.
- Produce few type of colonies – T1 ,T2 , T3, T4, T5.

3. BIOCHEMICAL REACTION –
- Oxidase – Positive
- Ferment glucose not maltose
- Acid production without gase
ANTIGENIC STRUCTURE –
- Capsule
- Pili
- Lipooligosaccharide
- Proteins
PATHOGENESIS –
- Gonorrhoea – it is a sexually transmitted disease involving urethra in both sexes but
in females, the endocervix is the primary site of infection. The incubation period is 2
– 8 days. It is an acute urethritis characterized by purulent urethral discharge.
Asymptomatic infection is common in women. In males, the acute urethritis may
extend to the prostate, testes, seminal vesicles and epididymis. If untreated it may
lead to fibrosis and stricture.
- Ophthalmia Neonatorum – it is gonococcal conjunctivitis in the newborn through
infected birth canal.
- Gonococcal vulvovaginitis – Adult women vagina is usually resistant to gonococcal
infection because of acidic pH but vulvovaginitis can occur in prepubertal girls.
- Other infections – Rectum or oropharynx is involved.
LAB DIAGNOSIS –
- Specimen – Urethral discharge, cervical discharge
- Transport - immediately or In stuart’s transport medium
- Direct microscopy – see above
- Detection of antigen or nucleic acid – ELISA
- Culture – chocolate agar or Thayer marti medium
- Colony morphology & gram staining
- Superoxol test
- Biochemical reaction
- Serology – complement fixation test, immunofluorscense & ELISA