Bacteriology- Neisseria | Quick Revision Notes for NEET-PG

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Morphology- Gram -ve diplococci,strict aerobs,catalse & oxidase +ve,capnophilic-require CO2,some-commensals in oral cavity and genito-urinary tract 

Pathogens-

    1. Meningitidis/meningococcus
    1. Gonorrhoea/Gonococcus

Capsulated,lens shaped

Non-capsulated, kidney shaped

(media-chocolate agar)

 

Causes meningitis

Causes gonorrhoea

Utilises both glucose and maltose

Only glucose

Rarely have plasmids

Usually possess plasmids

Habitat-nasopharynx

Habitat-genital tract

Beta-lactamases is less common

More common

Drug resistence less common

More common

 

Meningococcus

Out of 13 serogroups ,disease in humans is cause by 5(A,B,C, W-135,Y)

Site of carriage-nasopharynx(of 5-10% indivisulas). During epidemic carrier rates increase upto 90%

Virulence factors-

 

  1. Capsular polysaccharide-anti-phagocytic
  2. Pilli-anti-phagocytic,helps in adhesion
  3. OMP/outer membrane protein-helps in adhesion
  4. Endotoxin-
  5. IgA1 protease-cleaves subclass IgA 1 and inactivates it.

 

Diseases/ Clinical manifestation-

  1. Pyogenic Meningitis-causes fever,vomitting,headache,neck stiffness,no rashes
  2. Meningococcemia
  3. Whaterhouse friderichsen syndrome-1)It is a fatal disease 2) hall mark on autopsy-bilateral adrenal haemorrhage
  4. Non-blanching rashes

 

Dx(diagnoisis)-

  1. Specimen collection- CSF,blood,nasopharyngeal swab
  2. CSF examination-
    1.  1st portion used for-CAD,biochemical analysis showing increase in CSF pressure and protein,decrease in glucose
    2. 2nd portion used for- culture on blood agar and chocolate agar
    3. 3rd portion-enriched in BHI broth
  3. Nasopharyngeal swab culture-on Thayer Martin medium
  4. Biochemical test- Oxidase and catalse +ve , fermentor of glucose and maltose but not sucrose
  5. ELISA
  6. PCR

Commensal Neisseria species- harmless, non fastidious, can grow on basal media like nutrient agar,not capnophilic

Examples-N. elongata(rod-shaped), N. mucosa(capsulated),N. flava & N. flavescens (pigmented)

 

Non-meningococcal meningitis

Stre. Pneumoniae

haemphilus

Gonococcus

 

Culture-

Virulence factors-

  1. Pilli(most important virulence factor)-anti-phagocytic,helps in adhesion to urethral and endocervical epithelium
  2. OMP(Outer Membrane Protein)- It is of 3 types-Protein 1,2,3

        Protein 1- forms pores and help in exchange of molecule across gonococcal surface.

        Protein 2-helps in adhesion,responsible for opacity of gonococcal colonies.

  1. LOS(Lipo-oligosaccharide)-endotoxin in nature
  2. IgA1 protease-cleaves mucosal IgA

 

      CLINICAL FEATURES

 

In males                                                                               In females

Cause urethritis                                                                           cause endocervicitis

                                          (asymptomatic and act as reservior of Infection)

  • Urethral discharge                                                                                                                                                                
  • Burning micturation

 

COMPLICATIONS

MALES

FEMALES

Periurethral abscess leading to stricture formation

Acute PID( Pelvic Inflammatory Disease-fallopian tube disease)

This causes infertility and ectopic pregnancy.

Watercan perineum(multiple discarging sinuses)

Fitz-Hugh-Curtis syndrome

Characterised by

  • Peritonitis
  • Peri-hepatic inflammation

Disseminated gonococcal infection/DGI(due to deficiency of late complement proteins)

 

 

 

 

Ophthalmia neonatorum-in  neonates

Caracterised by

  • Purulent discharge from eyes
  • Onset-2 to 5 days after birth

due to transmission of org. (in mother genital flora)from mother to baby dring normal vaginal delivery

 

DGI

 

 

Diagnosis(specimen to be collected)

 

Males

Females

Urethral discharge(best)

Endocervical swab

Periurethral swab

(never vaginal swab)

 

  1. Collect specimen
  2. Transport media to be used- Stuart’s/amies transport media
  3. Microscopy- Gram negative kidney shaped diplococci
  4. Culture- Fastidious organism chocolate agar medium,Thayer Martin medium,Modified New York City medium
  5. Biochemical test- Oxidase and catalse +ve,ferments glucose but not maltose

 

Non-Gonococcal Uretheritis

Cuastaive agent of uretheritis is not N. gonorrohea

Causative agents-

  • Bacteria-Mycoplasma hominis
  • Virus – Herpes simplex virus, cytomegalovirus
  • Fungi-Candida albicans
  • Parasites – Trichomonas vaginalis
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