MICR 454L

Emerging and Re-EmergingInfectious Diseases

Lecture 4:N. meningitidis

(Chapter 8)Dr. Nancy McQueen & Dr. Edith Porter

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

Neisseria meningitidis

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

Major N. meningitidis Virulence Factors and Their Roles in Host-Pathogen Interaction

http://zdsys.chgb.org.cn/cgi-bin/VFs/genus.cgi?Genus=Neisseria

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

Induced Uptake of N. meningitidis

http://zdsys.chgb.org.cn/cgi-bin/VFs/genus.cgi?Genus=Neisseria

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- Capsule - antiphagocytic;

protection from antimicrobial peptides

Pili, Opa,LOS, and to a lesser extent, Opc, undergo antigenic variation

IgA1 protease

N. meningitidis Virulence Factors: Iron Acquisition and Uptake

http://zdsys.chgb.org.cn/cgi-bin/VFs/vfs.cgi?VFID=VF0272#VF0272

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?

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).

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

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)

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

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.

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

Latex agglutination

+

Specific antibody bound to latex particles

+

Specific antigen

Agglutination

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.

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

Meningitis Belt in Africa

http://www.nathnac.org/ds/c_pages/documents/mening_belt.gif

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.

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: Microbe

2005 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.

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.