Meningitis

Bacterial meningitis is a devastating disease, if left untreated it results in death. Essentially it is an inflammation of the meninges. There are different types of bacteria that cause meningitis in neonates, elderly, and infants and children. Meningitis is rare between the ages of 20-60.

1. Neonates – Group B Strep, E. coli K1

2. Infants and children – H. influenza, Neisseria Meningitis, S. pneumoniae

3. Children and adolescents – N. meningitis

4. Elderly – S. pneumonaie

H. influenza also causes ottitis, and S. pneumonaie also causes pneumonia, but the rest of the bacteria listed above only cause meningitis.

Infection starts with the respiratory tract  adhesion  bloodstream  meninges. There is often no clinical manifestation before onset of the meningitis.

N. MENINGITIS

This is the most important one because it can infect infants thorugh adults. It’s a Gram – cocci and is closely related to N. gonorrhea. It has a huge antiphagocytic capsule. IgA may actually protect the bacteria because it can block IgE or IgM binding and it can’t activate compliment.

1. Droplet Infection 

2. URTI 

3. Pilli adhesion 

4. Colonize nasopharynx (can stay here for a long time because it’s favorite host is human) 

5. Growth 

6. Get into deep tissue 

7. If have predisposing factors like viral infection, excess IgA, or compliment deficiency, disease develops 

8. If multiplies in blood can have menigococcemia – the release of LPS leading to toxic shock syndrome.

The best way to protect people would be to have an antibody against the capsule. There are 13 different serotypes with distinct polysaccharides, but there is one problematic capsule, it’s made of sialic acid, which is a self-antigen.

HAEMOPHILUS

Unique to infants. H. influenza is the leading cause of ottitis media and meningitis. It is a Gram – rod and has a crescent shape. There are several species. H. ducrei causes an STD. The bacterium needs the growth factors hematin and NAD. There are 6 types of factors A-F. B is the most prevalent, so we vaccinate against it. Same mechanism of infection as N. meningitis.

The mother gives antibodies to the newborn, but they decrease and eventually the baby builds up her own resistance because of colonization. However there is a period between the ages of 1 and 5 where there is little antibody. That is when this bacteria comes acallin.

There is a vaccine vs. the capsule. It is usually conjugated with the diphtheria toxoid. All babies get this vaccine.

GROUP B STREP

S. agalactia looks a lot like GAS. It has an antiphagocytic capsule with sialic acid (a self-protein). There are 6 serotypes. Lipoteichoic acid is used for adhesion. The difference is that it has no toxins.

E. coli K1 also has polysialic acid. Hey wait a minute!!!! H. influenza, N. menigitidis group B, and Group B Strep all have some form of sialic acid! Maybe there are receptors in the meninges for this acid and that’s why these bacteria cause meningitis.

How does Group B Strep cause meningitis and why in newborns?

1. Group B normally colonizes the vagina, but doesn’t cause disease because it is normal flora 

2. Newborn goes through birth canal 

3. Bacteria can go straight to the meninges if the mother is very heavily colonized (early onset meningitis, usually type I or II capsule). Predisposing factors are premature ruptured membrane, prolonged labor, and pre-term delivery. But we can prevent the problem by giving antibiotics. We could also give a vaccine, but that’s not on the market yet. This bacterium a problem in poor southern areas like Alabama, but these mothers don’t tend to go for swabs to see if they are carrying the bacteria. 

4. Late onset meningitis is within the first month of life from p2p contact like breast-feeding. Usually this bacterium has type III capsule. 

5. Rapid diagnosis is essential, and can be done with latex particles coated with anti-group B polysaccharide.

Ok, so we know that the bacteria go pharynx q GALT w lymph nodes e blood rspleen or liver . Meninges, but how do they do that?

They must leak out of the capillary to the arachnoid space.

1. Gram – cocci do this by passing through endothelial cells.

2. H. influenza is so skinny it can between cells.

3. S, pneumoniae and Group B Strep get phagocitized by monocytes and through chemotaxis are brought to the arachnoid space.

Antiobiotics are the most effective way to prevent permanent damage to neurons!!!

Category: Medicine Notes