7. Neisseria spp

Question 1

what are they?

Answer 1

gram -ve diplococci

Question 2

what are the pathogenic / non-pathogenic Neisseriae spp?

Answer 2

Pathogenic:
-Neisseria meningitidis 
-Neisseriae gonorrhoeae 
Non- pathogenic 
- Commensals in nasopharynx

Question 3

Neisseria gonorrhoeae?

Answer 3

• fastidious gram -ve diplococci (bean-shaped)
• grow at 37C lysed blood & chocolate agar in 5-10% CO2
• oxidase positive
• identication: glucose utlitization—> acid
  ( test: sugars added to agar Neisseria gonnorhoea only uses glucose (bc of acid production))

Question 4

Neisseria gonorrhoeae pathogenicity?

Answer 4

• fimbriae or type IV pili attachment to mucosal surface (target site for pili attachment for entrance point of pathogen into cells causing disease)
• resistance to intracellular killing by phagocytic cells by production of catalase that protect the organism from effect of toxic O2 radicals
• Antigen variation of fimbriae and outer memebranw protien II (mutation during DNA replication) (of the mutation, whenever the m.o. enters the body it’s as if it’s a new m.o.)

Question 5

Clinical features of Neisseria gonorrhoeae?

Answer 5

• never normal flora
• Local infections
  ~ acute urethirits in males
  ~ 95% symptomatic (male) ( 50% females)
  ~ dysuria, urethral discharge
  ~ local spread: epididymitis, prostatitis, urethral stricture

Question 6

Clinical features of Neisseria gonorrhoeae?

Answer 6

• Acute vaginitis & endocervicitis
• 50% of females symptomatic
• pelvic inflammatory disease
• salpangitis
• infertility
• opthalamia neonatorum

Question 7

Clinical features of Neisseria gonorrhoeae?

Answer 7

• disseminated gonococcal infection
  ~ common in female
  ~ fever, arthritis, septic skin lesions on extermities
  ~ RARELY: mebingitis, infective endocarditis

Question 8

Clinical features of Neisseria gonorrhoeae?

Answer 8

• vulvovaginitis in prepubertal girl

~ child abuse

Question 9

Neisseria gonorrhoeae diagnosis?

Answer 9

~ urethral (male), endocervical (female) swabs
~ culture & sensitivity
~ non culture methods: detect nucleic acid by PCR

Question 10

Neisseria gonorrhoeae Treatment?

Answer 10

~ both patient & partner
~ ceftriaxone or spectinomycin
~ ciprofloxacin: resistance

Question 11

Neisseria gonorrhoeae Control?

Answer 11

• adequate diagnosis, treatment
• contact tracing
• prevention: condom, barriers methods
• screening for high-risk indivitual
• prevent opthalmia neonatorum: 1% silver nitrate in eyes of all newborn in high prevalence area

Question 12

Neisseria meningitidis?

Answer 12

• Fastidious aerobic gram -ve diplococci (bean- shaped)
• grows on 37C on blood & chocolate agar
• oxidase positive
• identification: glucose & maltose = positive
• viability: organism die quickly at room temperature outside human host

Question 13

Neisseria meningitidis?

Answer 13

• it produces polysaccharide capsule which is the base for serogroup typing system
• 13 serogroup: commonest A, B,C, X, Y,Z,W-135
• typing: slide aggulination with specific antisera

Question 14

Neisseria meningitidis epidemiology?

Answer 14

• reservoir: human nasopharynx
• carriers (20%), 50% non capsulated i.e. non-pathogenic
• epidemics: carriers 90%
• risk factors
  ~ lack of bactericidal antibodies
  ~ age: 3 months — 3 yrs, 18-23 yrs
  ~ travel to edemic areas ( africa, mecca)
  ~ complement deficieny
  ~ splenectomy

Question 15

Neisseria meningitidis pathogenesis?

Answer 15

• type IV pilus: mucosal colonization of nasopharynx
• organism cross nasopharynx —> circulation
• polysaccharide capsule resist host immune defense

Question 16

Neisseria meningitidis clinical features?

Answer 16

• meningitis, septicemia

- conjunctivitis, artheritis, infective endocarditis

Question 17

Neisseria meningitidis virulence factors?

Answer 17

• polysaccharide capsule: prevent phagocytosis
• LOS endotoxin: present in the outer membrane of N. mengitidis, damage to blood vessels associated w/ meningococcal infection
• lipooligosacchride: stimulates TNF-alpha results in host cell damage

Question 18

Neisseria meningitidis laboratory diagnosis?

Answer 18

• CBC
• blood culture
• CSF
  ~ cell count: WBC (PMN)
  ~ glucose (less), protein (more)
  ~ culture
  ~ direct antigen detection
  *serogrouping: slide agglutination test
  *PCR: blood or CSF

Question 19

Neisseria meningitidis treatment?

Answer 19

• treatment
• penicillin
• ceftriaxone
• chemoprophylaxis
• rifampicin or ciprofloxacin for both patient & contacts
• notification to public health department
• Immunoprophylaxis: serogroups A,B,C,Y, W-135
• infection control
• isolation of patient for 2 days

Question 20

Moraxella catarrhalis?

Answer 20

• Aerobic gram -ve diplococci
• grow at 37C on blood agar & chocolate agar
• oxidase: positive
• DNase: positive
• Commensals in upper resp tract

Question 21

Moraxella catarrhalis clinical features?

Answer 21

• Otitis media
• sinusitis
• lower resp tract infections in chronic obstructive pulmonory disease especially elderly
• bacteraemia esp. immuno-compromised patients

Question 22

Moraxella catarrhalis virulence factors?

Answer 22

• outer membrane proteins (OMPs)
• Lipo-oligosacharide (LOS): initial stage of attachment to nasopharynx
• pilli

Question 23

Moraxella catarrhalis treatment?

Answer 23

• amoxicillin-clavulanic acid (beta-lactamase +ve)

- cephalosporins