29-Neisseriae Flashcards
Neisseria- morphology and gram stain
Gram (-) cocci
Neisseria- reservoir
Humans
N. meningitis- transmission
person-person by aerolization of respiratory tract secretions
N. gonnorrhoeae- transmission
STD, carriage can be in asymptomatic people
N. gonnorrhoeae- susceptible people
Blacks, ppl ages 15-24, residents of SE USA, ppl with multiple sexual partners (giggity)
N. meningitides- susceptible people
children <5, institutionalized ppl
Gonorrhea- clinical presentation
purulent discharge of involved site (urethra, cervix, epididymis, prostate, anus after 2-5 incubation days
Meningitis- clinical presentation
purulent inflammation of meninges- headache, meningeal signs, fever (high mortality if not treated appropriately and quickly)
Disseminated infections (from N. gonnorrhoeae)- clinical presentation
spread of infection from genitourinary tract through blood to skin or joints- pustular rash with erythromatus base and suppurative arthritis in joints
Opthalmia neunatorum (from N. gonnorrhoeae)- clinical presentation
purulent ocular infection acquired by neonate at birth (from vagina of infected mother)
Meningococcemia (from N. meningitides)- clinical presentation
disseminated infection- thrombosis of small blood vessels and multiorgan involvement- small petechial skin lesions which coalesce into larger hemorrhagic lesions
Pneumonia (from N. meningitides)- clinical presentation
milder form of meningococcal disease- bronchopneumonia in patients with underlying pulmonary disease
What is the main VF in Neisseria?
Pili
What is the function of Pili in Neisseria?
- mediate functions: attachment to host cells, transfer of genetic material, and motility
- composed of repeating protein subunits (pilins)- expression is controlled by the pil gene complex
- pili expression is associated with virulence because of involvement in host attachment to and provide resistance to killing by neutrophils
- lack of immunity to re-infection with N. gonorrhoeae results partially from antigenic variation among pilin proteins and from phase variation in pilin expression.
Neisseria- media
modified Thayer-Martin Agar chocolate agar
What is opa?
- opacity proteins
- membrane proteins that mediate intimate binding to epithelial and phagocytic cells and are important for cell to cell signaling
- N. gonorrhoeae- Opa proteins are opaque (not transparent)
- Opa associated with clinical disease
- Opaque colonies are in localized disease
- Transparent colonies associated with pelvic inflammatory disease and disseminated diseases
Why can’t you use penicillin for gonorrhea infections?
- historically, was the antibiotic of choice for gonorrhea
- not used today because the concentration needed to kill susceptible strains has increased and is now resistant.
- Resistance is caused by the ability of the membrane proteins and antigens to produce β-lactamase or by chromosomally mediated changes in penicillin-binding proteins and in cell wall permeability
- Resistance is also associated with resistance to tetracyclines, erythromycin and aminoglycosides.
Why is antigenic variation in Neisseria infections bad?
• the lack of immunity to re-infection by N. gonorrhoeae results partially from the antigenic variation among the pilin proteins and partially from the phase variation among the pilin gene expression. These factors complicate attempts to develop effective vaccines for gonorrhea.
What is the fxn of the capsule in Neisseria?
• The polysaccharide capsule also has antiphagocytic properties that protect N. meningitidis against phagocytic destruction. This allows the meningococci bacterium to penetrate through cells, avoid intracellular death while in a phagocytic vesicle, replicate, and then migrate into subepithelial spaces where the infection is established.
What is disseminated intravascular coagulation?
- associated with meningococcemia
- begins with thrombosis of small blood vessels and multiorgan involvement
- presents with small petechial skin lesions on trunk and lower extremities – may coalesce to form larger hemorrhagic lesions
- leads to overwhelming disseminated intravascular coagulation with shock along with bilateral destruction of adrenal glands (Waterhouse-Friderichsen syndrome)
