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Neisseria-
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- 3. Neisseria Meningitidis General characteristics •Gram-negative,bean-shaped,diplococci •Donotpossessflagellaorspores •Capsulatedandpossesspili. •Strictparasites,donotsurvivelongoutsideofthe host •Aerobic •Oxidativemetabolism •Producecatalaseandoxidase •Pathogenicspecies require enriched complex mediaandCO2
- 4. Morphology • Gram-negative,bean-shaped,diplococci • Donotpossessflagellaorspores. •Capsulatedandpossesspili. • 0.8x0.6µmindiameter. Cultural characteristics • Cangrowinbloodagar,Chocolateagar. • Growthisimprovedbyadditionofbloodorserum. • Growth is also improved by incubation in the presenceof2- 8%CO2 • Growthtemperatureis36-39⁰CandpHrangesof6-8. • Coloniesare1-2mmindiameter,convex,greyand transparent.No hemolysisinbloodagar.
- 5. Biochemical properties •Oxidase-positive; i.e.,they possess the enzyme cytochrome and produce oxidase. •N.Meningitidisismaltosefermenter. •N.Meningitidis produces no beta lactamases.
- 6. Ithasthreeimportantvirulencefactors: 1. Polysaccharride capsule.It is antiphagocytic innature. 2. The endotoxin of N. Meningitidis is a lipopolysaccharide (LPS). It induces septic shockbycausingreleaseofcytokines. 3. IgA protease. It cleaves the IgA antibodies presentin respiratorymucosa.
- 7. by airborne Pathogenesis • Humansaretheonlynaturalhosts •The organisms are transmitted droplets • Colonizethenasopharynxandbecometransient floraofthe upperrespiratorytract. • From the nasopharynx, the organism can enter the bloodstream and spread to meninges and grow in the cerebrospinalfluid.
- 8. Diseases • N.Meningitidisisthemostcommoncause ofmeningitisin personsbetweentheagesof2and 18years. • Outbreaks of meningitis are most common in winter and early spring, and favored by close contact between individuals. 1. Meningitis 2. Meningococcemia (multiplication of bacteria in the blood stream)
- 9. Laboratory diagnosis •Itis frequentlyisolatedfromsamplessuchas blood,CSF . •Differentmethods for laboratory diagnosis are: Gramstaining Culture Oxidasetest Fermentationtests Latexagglutinationtest
- 10. Gram staining The diagnosisis suggested by the finding of gram negativebacteriabeanshaped capsular diplococci.
- 11. Culture The organism iscultured on blood agar or chocolate agar incubatedat37°C ina5%CO2 atmosphere. Coloniesare1-2 mmin diameter, convex,greyandtransparent.Nohemolysis
- 12. Oxidase test: Determinesthepresenceofcytochromeoxidase. ItisPositiveinN.Meningitidis. Growthe isolate(s) to be tested for 18-24 hours on a blood agar plate at 35-37°C with ~5% CO2. Dispense a few drops of Kovac's oxidase reagent. Tilt the plate and observe colonies for a color change to purple. Positive reactions will develop within 10 secondsintheformofa purplecolor.
- 13. fermentation: N. Meningitidisferment fermentation: N. Meningitidis ferment Manitol manitol. Maltose maltose. Latex agglutination test, which detects capsular polysaccharideinthespinalfluid.
- 14. Treatment and Prevention •PenicillinGorsulphonamidesarethedrugsof choice. or third generation such as cefotaxime or • Cholramphenicol cephalosporin ceftriaxone are recommended for patients whoareallergictopenicillin. • M eningococcal vaccine, is available which containsthecapsularpolysaccharide.
- 15. Neisseria Gonorrhoeae •N. Gonorrhoeaecauses gonorrhea, neonatal conjunctivitis (ophthalmia neonatorum) and pelvicinflammatorydisease(PID). Morphology • Ovalshaped • Gramnegativediplococci • Sizeis0.6to0.8µm. • Occursinpair • Nonmotile • Capsulatedandhavepilli
- 16. Cultural characteristics •Cangrowin enrichedmediasuchaschocolate agar. •Growthisalso improved by incubation in the presenceof5- 10%CO2 •Growth temperature is 37⁰C and no growth if thetemperatureis lessthan25⁰Cormore than 38.5⁰C •pHrangesof 7.2-7.6.
- 17. Biochemical properties Thevirulencefactorsare. 1. Pili:Mostimportantvirulencefactors. Piliatedgonococciareusuallyvirulent,whereas non piliatedstrainsareavirulent. 2. Twovirulencefactorsinthecellwall a) Lipooligosaccharride (LOS) (amodifiedform of endotoxin).Endotoxinofgonococciisweakerthan thatofmeningococci. b) Outer membrane proteins(OMP) :OMPcause attachmentofbacteriatoepithelialcellsofthe urethra, rectum,cervix,pharynx,orconjunctiva,like pilli.
- 18. 3. IgAprotease • Themain host defenses against gonococci are antibodies (IgA and IgG), complement, and neutrophils. •IgA protease degrades one of these antibodies. Other biochemical properties are; • They ferment glucose • They are oxidase positive
- 19. Pathogenesis • Humans areonly reservoir, not part of normal flora. • Causes disease only in humans. • Transmitted sexually both in males and females. • N. gonorrhea causes following infections. 1. Gonorrhea 2. Neonatal conjunctivitis (ophthalmia neonatorum) 3. Pelvic inflammatory disease (PID).
- 20. Laboratory diagnosis • Itis frequently isolated from samples such as blood, urethral discharge in men, cervical discharge in females. • Different methods for laboratory diagnosis are: Gram staining Culture Oxidase test Fermentation tests
- 21. Gram staining The diagnosisis suggested by the finding of gram negativebacteriabeanshapedcapsular diplococci.
- 22. Culture The organism iscultured on Thayar - Martin Agar or Mueller-Hintonagar(chocolateAgar) incubatedat37°Cina5%CO2 atmosphere.Colonies are1-2mmindiameter,greyandtransparent.N. gonorrheagrowsrapidly producingsmall,Nohemolysis.
- 23. Oxidase Test • Testonfilterpaperordirectlyonplate •Oxidasereagent=Dimethylortetramethyl oxidasereagent • Violet-purple color indicates a positive result.
- 24. Manitol fermentation: N.Gonorrheafermentmanitol. Maltosefermentation: N. Gonorrhea do not ferment maltose.
- 25. Treatment and Prevention Treatment •Penicillin • Tetracycline if beta-lactamase positive strain. Canalso use cephalosporinsand flouroquinolones. Prevention • The prevention of gonorrhea involves the use of safety measures and the immediate treatment of symptomatic patientsandtheir contacts.