Lec . 7 Gram-negative cocci - PowerPoint Presentation

1. Lec. 7Gram-negative cocciNeissereaeMedical MicrobiologyBy:Asst. Prof. Dr. Shaima’a Al-Salihy

2. NeisseriaeNeisseriae:The most important species are:Neisseria gonorrhoea (gonococci)Neisseria meningitidis (meningococci) both of them are strict human pathogenfound inside polymprphnuclear cells. Others are normal flora of human respiratory tract.

3. Gram Negative cocciNeisseriaeMorphology:Gram negative cocci arranged in pairs.Kidney or coffee bean shape (the flat or concave sides are adjacent). Non-sporing, non-motileOxidase-positive that differentiate them from streptococci.Most are catalase-positive.

4. Gram Negative cocciNeisseriaeCulture:fastidious bacteria grow on enriched media; Mullar-Hinton, Modified Thayer-Martin or Heated blood agar (Chocolate agar). They produce convex glistening, non-pigmented, non-hemolytic colonies.They required 5% CO2 (Candle jar).Ferment sugars producing acid but not gas.

5. There are two pathogenic species for humans:Neisseria gonorrhoeae (Gonococci) GCNeisseria meningitidis (Meningococci) MCNon pathogenic e. g. Moraxella catarrhalis was previously named Branhamella catarrhalis (Neisseria catarrhalis).

6. Neisseria gonorrhoea:The causative agent of gonorrhea, ophthalmia neonatorum, and pelvic inflammatory disease (PID). Biotypes: - (T1, T2) virulent small brown colonies (piliated gonococci) posses pili which are adherence factors.- (T3, T4) a virulent large non pigmented colonies (no piliated gonococci). Virulence factors

7. Virulence factors:1.Pili : Pilin protein. Attachment to host cell and resist phagocytosis.2-IgA protease: split the IgA, major mucosal immunoglobulin.3.Cell wall components:Por: preventing phago-lysosome fusion Opa (Opacity): enhance adherence of gonococci within coloniesRmp (Reduction Modifiable protein)Lipooligosaccharide: possess endotoxic activity.Virulence factors

8. Pathogenesis:Gonorrhea:Transmitted by sexual contact.Gonoccocci attach themselves to the mucosal cells by pili and protein II (Opa)Invasion of cell.pass through the cells into the subepithelial space, thereby establishing the infection.Lipopolysaccharide: endotoxinIgA Protease: destroys immunoglobulin IgA

9. Clinical findings:In male:symptoms: urethra, purulent discharge, dysuriaincubation period:2-7 days after infectionComplication: epididymitis, prostatitis, periurethral abscessesIn female:symptoms: frequently asymptomatic. When symptomatic: cervicitis, vaginal discharge, dysuria, abdominal pain,Complication: ascending genital infection, salpingitis, tubo-ovarian abscess, pelvic inflammatory disease (PID)

10. Post-gonococcal urithritis (PGU): is common chronic sequelae of untreated or badly managed gonorrhoea, usually caused by different pathogens. Gonococcal ophthalmia neonatorum: An infection of the eye of newborn acquired during passage through infected birth canal.Disseminated gonococci infections (DGI) arthritis, skin lesion.

11. Lab. Diagnosis :- Specimens: pus, secretion from urethra, cervix, conjunctiva, throat and rectum. Gram stained smear: intracellular Gram-negative diplococci in PMNs (polymorphoneuclear cells) from urethral discharge, in men is sufficient for diagnosis while in women false positive because of the normal flora interference

12. Lab. Diagnosis :- 3. Culture: Chocolate agar. Thayer-Martin agar. (selective medium) which is chocolate agar containing antibiotics (vancomycin, colistin and nystatin to suppress the normal flora found in the specimen. Modified Thayer-Martin agar. same as(Thayer-Martin agar plus trimethoprim) The culture is incubated in an atmosphere containing 5% COZ (candle extinction jar) at 37°c. 4. Oxidase test positive. 5. Sugar fermentation the differentiation between GC and MC is made on the bases glucose and maltose. Ferment glucose only 6. Nucleic acid amplification test.

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14. Immunity: Antibody against Opa proteins and LOS.No protection against reinfection. due to the antigenic changes of the pili and outer membrane proteins.Treatment:PPNG have increased in prevalenceCefitriaxone, and Doxycycline for concomitant chlamydial infection substituted by erythromycin in pregnant women.

15. Neisseria meningitidis:The causative agent of meningitis, meningococcemia ( life-threatening form is Waterhouse-friderichsen syndrome ).Serogroups A, B, C, Y and W- 135. 5-30% of the normal population carrierVirulence factors: Polysaccharide capsule: antiphagocyticIgA proteaseLPS*Streptococcus pneumonia and Neisseria meningitides (more than 80% of cases bacterial meningitis in persons over 2 months of age).

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17. Pathogenesis and clinical findings: - portal of entry: nasopharynx and gain acsess to CNS:Invasion of blood stream: causing bacteremia.Direct contiguous spreadMeningitis is the most common complication of meningococcemia.Headache, vomiting and stiff neck.Waterhouse-Friderichsen syndrome: high fever, hemorrhagic rash, disseminated intravascular coagulation, and circulatory collapse

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19. Lab. Diagnosis :- 1. Specimens: blood, CSf and nasopharyngeal swap. 2. Direct-Gram stain smear of centrifuged CSF shows MC as typical Neisseria within polymorphonuclear leukocyte or extracellularly. 3. Culture: Choclate agar and incubated at 37oC with 5% CO2, or Thayer martin agar and modified TM. 4. Biochemical test :- --Oxidase test-positive. --Sugar fermentation test, ferment maltose and glucose. 5. Serology, antibodies to meningococcal polysaccharides can be measure by latex agglutination test or by measuring the bactericidal activity.

20. Immunity: - the immunizing antigen is capsular polysaccharideThere are 2 types of vaccine:Non conjuated tetravalent vaccine (Vaccine contains capsular polysaccharide of strains A, C, Y and W-135)Conjugated Treatment:- Penicillin G

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