Neisseria
- List the characteristics of Neisseria meningitidis
- Gram negative diplococci
- Kidney bean shaped in pairs (adjacent sides flat)
- Oxidase positive
- Catalase positive
- Immotile
- Non-spore forming
- Fimbriated/ piliated
- Prominent Polysaccharide capsule (determines serogroup)
- Expresses PorA and PorB proteins
- Facultative intracellular
- Aerobe
- Maltose and glucose fermenter
- Fastidious (Cultured on Thayer-Martin/ VCN, CBA)
- Extremely sensitive to temperature (optimum 37*C)
- Briefly describe the epidemiology of Neisseria meningitidis
- Obligate pathogen, High carrier rates in individuals living in close vicinity to one another (college students or soldiers)
- Transmission: Respiratory droplets and throat secretions
- Predominant strains in Menigitidis belt: A,B,C,W,X,and Y – vaccines
- Importance of serogroup W135: responsible for the epidemic of W135 meningococcal disease in 2000 which was associated with the Hajj pilgrimage in Saudi Arabia
- Strains causing epidemics in developing countries: A
- Strains causing epidemics in developed countries: B, C, Y and W-135
- List the Virulence factors of Neisseria meningitidis
- IgA1 protease
- Capsular polysaccharides
- Lipooligosaccharide (LOS) endotoxin
- Serum levels correlate with symptom severity
- Aid in penetrating the CNS
- Adhesins: pili and opacity proteins (allow cell adherence and impair lymphocyte activation)
- Facilitate nasal colonization → systemic infection
- Lab diagnosis
- Specimen: CSF, swabs from haemorrhagic skin lesions, blood, nasopharyngeal swabs in Stuart’s media (for carrier survey)
- CSF: leukocytosis (neutrophilia), increased protein, decreased glucose
- Culture: CSF on BA/ Thayer-Martin media, Blood into castenada bottles first, if colonies transfered to BA/ Thayer-Martin
- Colonies: mucoid and shiny
- Gram stain: GN diplococci (smear: most will be within the cytoplasm of the neutrophils)
- Biochemical test: Oxidave positive, Glucose and maltose fermentation, DNAse negative, OPNG/beta-galactosidase negative
- Serology: Latex agglutination to detect capsular polysaccharides e.g A, B
- Molecular test: PCR
- CBC: Elevetad WBC
- Antibiotic of choice and Vaccines
- 3rd gen cephalosporins (e.g. ceftriaxone)
- Penicillin G (if penicillin susceptible)
- Prophylaxis (only close contacts: ciprofloxacin, rifampin, or ceftriaxone)
- Polysaccharide vaccine
- Polysaccharide-protein conjugate vaccine (recommended for all adolescents 11 or 12 yeas)
- List the diseases caused by Neisseria meningitidis
- Meningitis
- Waterhouse-Friedrischen syndrome
- Meningococcimea with petechial bleeding and purpuric rash
- High fever, shock DIC, Thrombocytopenia, adrenal insufficiency, rash
- Nonsuppurative arthritis – commonly of the knee joint
- Meningococcal pneumonia
- Septic arthritis
- Purulent pericarditis
- Endopthalmitis
- Briefly describe Neisseria meningitidis under the following subheadings: Virulence factors and Laboratory features
- Virulence factors
- IgA protease: cleaves mucosal IgA to allow adherance and colonization of mucous membrane
- Capsular polysaccharide: Antiphagocytic; classification into serogroups is based on capsular antigens (e.g. A,B,C,W,X,and Y)
- Lipooligosaccharide: Induces TNFa and IL-1 leading to septic shock, serum LOS levels correlate with symptom severity, interferes with C3b deposition (w/sialic acid)
- Adhesins: fimbriae and opacity proteins – allow cell adherence and impair lymphocyte activation to facilitate nasal colonization and systemic infection
- Lab Features
- Specimen: blood, CSF, swabs from hemorrhagic skin lesions, Nasopharyngeal swabs in Stuart’s media (for carrier survey)
- CSF findings: centrifuge first: Increased leukocyte (mainly neutrophils), increased protein, decreased glucose
- Culture (CSF on CBA or Thayer Martin (VCN) media; Blood into castenada bottles first before transfer to CBA or VCN): , transparent, grey, mucoid and shiny 1-2mm colonies after incubation in CO2 (CBA)
- Gram stain smear: Gram negative diplococci, most within the cytoplasm of neutrophils
- Biochemical tests: Oxidase positive, Glucose and maltose fermenter, sucrose and lactose non-fermenters, DNAse negative, OPNG (beta galactosidase) negative
- Serology: Latex agglutination to detect capsular polysaccharides e.g. A and B
- PCR
- Elevated peripheral WBC
- Virulence factors
- What is the Antibiotic of choice for Neisseria meningitidis infection
- 3rd generation cephalosporin e.g. ceftriaxone PLUS azithromycin OR doxycycline
Differentiate between Neisseria meningitidis and Neisseria gonorrhoeae.
| Characteristics | Neisseria meningitidis | Neisseria gonorrhoeae |
|---|---|---|
| Capsulation | Capsulated | Non- capsulated |
| Mode of transmission | Respiratory droplets | Sexual contact, during birth, and handling specimens aseptically |
| Diseases caused | Meningitis, meningococcemia | Gonorrhea (STI), conjunctivitis, acute perihepatitis in adults, and Opthalamic neonatorum and bacteremia with arthritis in babies |
| Complications | Waterhouse-Friderichsen syndrome, neurologic defects | Infertility, Disseminated gonococcal infection |
| Maltose fermentation | Yes | No |
| Glucose fermentation | Yes | No |
| Diagnosis | CSF: direct microscopy, culture on CBA or TMM, Gram stain GN diplococci, Biochemical tests sugar utilisation, DNAse nrg, OPNG neg, NAAT | Culture on TMM or CBA, Gram stain of colonies shows GN intracellular diplococci, Biochemical test only utilises glucose, serology for gonococcal Ags, NAAT |
| Vaccine | Two tetravalent vaccines available: Polysaccharide vaccine and Polysaccharide protein conjugate vaccine | None |
- Describe the lab features of Neisseria gonorrhoeae and state the associated complications in women and children
- Lab features:
- Microscopy: GN intracellular diplococci
- Culture: small, raised, grey colonies
- Isolation: Enrichment media (BA, CBA)
- Selective enrichment media: Modifid New York City (MNCY)
- Biochemical tests:
- Oxidase positive
- Sugar utilisation: oxidises glucose
- Complications
- Women: infertility, Disseminated gonococcal infection (DGI)
- Children: Gonococcal conjunctivitis
- Lab features:
