MICR 454L

1. MICR 454L Emerging and Re-Emerging Infectious Diseases Lecture 4: N. meningitidis (Chapter 8) Dr. Nancy McQueen & Dr. Edith Porter

2. Overview • N. meningitidis • Morphology • Growth and metabolic characteristics • Virulence factors • Diseases • Host defenses • Diagnosis • Culture and biochemical identification • Membrane-based dot immunoassay • Latex agglutination • PCR • Therapy and Prevention • Threats

3. Neisseria meningitidis

4. Neisseria meningitidis • Gram-negative aerobic diplococci • Capnophil • Capsule - only some serotypes are associated with epidemics • Serotypes A, B, C, W-135, Y • US: C, Y, and W-135 (infants: B) • 10% of people are healthy nasopharyngeal carriers • Humans only known host • Transmission via respiratory droplets

5. Major N. meningitidis Virulence Factors and Their Roles in Host-Pathogen Interaction http://zdsys.chgb.org.cn/cgi-bin/VFs/genus.cgi?Genus=Neisseria

6. N. meningitidis Virulence Factors: Surface Proteins • Pili - attachment to nonciliated columnar epithelial cells • Class 5 protein (Opa) - attachment and invasion • Opc protein - attachment and invasion • Class 1, 2 and 3 proteins (por) - porins; invasion; intracellular survival • Class 4 protein (rmp) - elicits formation of ineffective blocking antibodies • Proteins that detoxify NO Outer membrane proteins

7. Induced Uptake of N. meningitidis http://zdsys.chgb.org.cn/cgi-bin/VFs/genus.cgi?Genus=Neisseria

8. N. meningitidis: Virulence Factors (2) • Lipooligosaccharide (LOS) • Comparable to LPS of Gram negative bacilli: endotoxin, but limited sugar residues • Adherence and invasion • Molecular mimicry of host structures • Released in membrane blebs • Lipid moiety strongly induces TNF-a • Capsule - antiphagocytic; protection from antimicrobial peptides • Pili, Opa,LOS, and to a lesser extent, Opc, undergo antigenic variation • IgA1 protease

9. N. meningitidis Virulence Factors: Iron Acquisition and Uptake http://zdsys.chgb.org.cn/cgi-bin/VFs/vfs.cgi?VFID=VF0272#VF0272

10. Active learning exercise • There is a multivalent capsular polysaccharide vaccine currently available for types A, C, Y, and W-135. It has not been possible to develop a capsular vaccine for type B. If you were to try to develop a vaccine to protect individuals from type B infections, what would you target and why?

11. N. meningitidis: Pathogenesis and Diseases • Pathogenesis • Attachment to epithelial cells • Invasion - bacteria cross the mucosal barrier • Bacteria enter the bloodstream • ? Entrance into central nervous system • Most symptoms are due to the toxic effects of the LOS • Diseases • Meninogococcal sepsis • Abrupt onset • High fever • Shaking and chills • Nausea and vomiting • Myalgias and weakness • Petechial rash (hallmark of MGC infections).

12. N. meningitidis: Pathogenesis and Diseases • More severe skin lesions as the disease progresses • Headache • Disease may or may not be accompanied by meninigitis • Disease may be chronic, moderate, or fulminant • The fulminant form of the disease = Waterhouse Friderichsen Syndrome

13. Waterhouse-Friderichsen Syndrome • Disseminated intravascular coagulation and multiorgan failure (due to released blebs) • Septic Shock and bleeding into adrenal glands • Widespread purpuric and ecchymotic skin lesions (bleeding into skin and surrounding tissue) • Pulmonary insufficiency • Death usually within 12 – 48 hours • Patients that survive may lose their limbs from tissue necrosis (gangrene of the skin and soft tissues)

14. N. meningitidis: Pathogenesis and Diseases • Bacterial meningitis • Abrupt or insidious onset • High fever • Petechial rash • Headache and stiff neck • Followed by nausea and vomiting • In severe cases there  is severe cerebral hyperemia (accumulation of blood) and  tissue swelling. • May progress to convulsions and coma • 10%-14% of cases are fatal • For patients who recover 11%-19% have permanent hearing loss or mental retardation

15. N. meningitidis - Host Defenses • Systemic infections occur in individuals lacking serum bactericidal antibodies against the capsular or other outer membrane antigens (Opc). • Systemic infections occur in individuals lacking late-acting complement components (C5-C8) or individuals lacking a spleen. • Chronic irritation or damage to the respiratory mucosa may be predisposing factors.

16. N. meningitidis: Diagnosis • Plate immediately • Is sensitive to temperature extremes and drying • Gram stain • Often seen intracellularly • Identification • Culture and biochemicals • Plating on selective media • Incubation in increased CO2 • Oxidase + • Catalase + • Oxidative use of glucose and maltose • Nitrate - • Membrane-based dot immunoassay • Latex agglutination • PCR

17. Latex agglutination Specific antibody bound to latex particles + + Specific antigen Agglutination

18. N. meningitidis: Therapy and Prevention • Therapy • Ceftriaxon • Prophylaxis with rifampin, ciprofloxacin, or ceftriaxone for household and other close contacts • Prevention • A capsular polysaccharide vaccine to protect disease from groups A, C, Y and W135 is available. • A group B vaccine consisting of OM antigens has been developed, but is not available in the United States.

19. Threats by N. meningitidis • Massive epidemic outbreaks in sub-Saharan Africa in the 1990's • Emergence since 1995 of serogroups Y, W-135 and X • Risk groups • Infants and young children • Refugees • Household contacts of case patients • Military recruits • College freshmen who live in dormitories • microbiologists who work with isolates of N. meningitidis • Patients without spleens or with terminal complement component deficiencies

20. Meningitis Belt in Africa http://www.nathnac.org/ds/c_pages/documents/mening_belt.gif

21. Take Home Messages • N. meningitis is a pathogen that resists phagocytosis, is capable of intracellular survival, and can induce a major LOS mediated inflammatory response with a rapidly fatal outcome. • 10% of the populations are carriers. • Capsule serotypes A, B, C, W-135, Y can cause epidemics.

22. Resources • The Microbial Challenge, by Krasner, ASM Press, Washington DC, 2002. • Brock Biology of Microorganisms, by Madigan and Martinko, Pearson Prentice Hall, Upper Saddle River, NJ, 11th ed, 2006. • Microbiology: An Introduction, by Tortora, Funke and Case; Pearson Prentice Hall; 9th ed, 2007. • Immunobiology, by Janeway,, Travers, Walport, and Shlomchik, Garland Science, 6th ed, 2005. • Malak Kotb Genetics of Susceptibility to Infectious Diseases Volume 70, Number 10, 2004 / ASM News Y 457-463 • Bernard Dixon MicrobeLibrary Article: Microbe2005 • Tsai CM, 2001. Molecular mimicry of host structures by lipooligosaccharides of Neisseria meningitidis: characterization of sialylated and nonsialylated lacto-N-neotetraose (Galbeta1-4GlcNAcbeta1-3Galbeta1-4Glc) structures in lipooligosaccharides using monoclonal antibodies and specific lectins. Adv Exp Med Biol 491:525-542. • Gray-Owen SD, et al., 2001. Neisseria In Groisman EA (ed.), Principles of Bacterial pathogenesis. Academic Press. San Diego, Calif. pp. 559-618. • Bentley SD, et al., 2007. Meningococcal genetic variation mechanisms viewed through comparative analysis of serogroup C strain FAM18. PLoS Genet 3(2):e23.

23. Resources • Hauck CR, Meyer TF, 2003. 'Small' talk: Opa proteins as mediators of Neisseria-host-cell communication. Curr. Opin. Microbiol. 6(1):43-49. • Spinosa MR, Progida C, Talà A, Cogli L, Alifano P, Bucci C. (2007) The Neisseria meningitidis capsule is important for intracellular survival in human cells. Infect Immun. Jul;75(7):3594-603. Epub 2007 Apr 30.