microbial chapter 3

Bacteria that have simple cell walls with much peptidoglycan.

Bacteria that have complex cell walls with less peptidoglycan but with lipopolysaccharides. Very toxic and hard to treat.

Usually unique in an important aspect of cell classification.
Chlamydia, Mycobacteria, Legionella

90% genetically
identical
- Produce very similar virulence factors
- 700,000 new infections reported a year in U.S. alone
- Both infect à remain asymptomatic à spread efficiently

- inflammation of the cervix (female) and urethra (both)
- pelvic inflammatory diseases
- eye infections in babies

- Target upper respiratory tract initially (throat, lungs)
- Capsule allows for resistance of host defenses - multiply to
high numbers in blood and cause damage (e.g. RBCs)

sexual contact, birth

Direct contact and droplet
- High infectious dose - not enough in casual contact

Require a complex medium called chocolate agar (heated blood, Fe, vitamins)
and higher CO2 levels for optimal growth

1) Gram stain of secretions/microscopy
2) MUST CONFIRM with a second test
- Culturing: Grow on choc. agar w/ antibiotics
- Test for oxidase - all Neisseria are oxidase positive
- Sugar tests - Narrows down species
- PCR: Can use species specific primers in order to amplify Neisseria DNA
- If get a product of expected size à Infected!

- gram negative cocci
- aerobic
- affects humans

mucosal epithelial cells upon entering the body

1) Type IV pilli
2)Other membrane adhesins
3) LOS

- Composed of mostly pilin
- Capable of retraction and twitching à movement!

no repeating O antigen (Neisseria spp., Haemophilus spp.)

While attached to the outside nonciliated cells, bacteria multiply rapidly

- Pili twitching helps them move deeper into to
reproductive/respiratory tracts
- Menses, fluid movement, muscle contractions
helps spread locally

- Involves crossing the epithelial barrier
- Steps:
1) Ciliary stasis - Bacteria stop movement of
cilia on nearby cells
2) Kill ciliated cells - LOS and peptidoglycan kill them, slough off
3) Internalization of the bacteria - Epithelial cells confused, microvilli engulf
bacteria and bring into a vesicle à Multiply rapidly

1) Alter surface proteins
- Most are recognized well by the immune system - change those expressed,
acquire new ones via a trade, change when they are expressed
2) Produce IgA protease - prevents neutralization and opsonization
3) Opa proteins bind to T cell CD4 and blocks activation
4) Add sialic acid to LOS on surface
look like the host
5) Capsule production

terminal sugar on many eukaryotic cell surface proteins, Nisseria add sialic acid to LOS on surface - camouflages to make
look like the hos

proteins bind to T cell CD4 and blocks activation

blocks complement
lysis and phagocytosis by neutrophils (allows for blood multiplication)

N. meningitis

mostly due to endotoxin (LOS) and peptidoglycan

- Relatively poor immunity (due to evasion strategies) = no vaccine
- Antibiotics - most are resistant to penicillin (cipro or cephalosporins)

- Antibiotics if already infected
- Prevention: Subunit vaccine available against capsular polysaccharides

High levels of endotoxin à TNF-α production à Inflammation à Damage

N. meningitis)