Intro Flashcards
What does a gram stain test for
Cell wall
Gram positive
cell wall is thick and made of peptidoglycans, inner cell membrane that is lipid bilayer ( no sterol).
- stains purple
- has acids that are virulence factors
Gram negative
- cell wall is thin peptidoglycan layer
- 2 cell membranes (inner and outer) made of lipid bilayer (no sterol)
- stains pink
- very impermeable due to double bilayer, has porin channels
- LPS-causes symptoms distally and locally (fever, platelets)
Peptidoglycans
Form cell walls and cross-link to each other
Colonization v. Infection
Colonization=things are present
Infection=things present & cause symptoms either due to tissue damage or due to immune response to the toxin/bacteria
Skin bacteria
Normal: staphylococcus epidermis
Transient: staphylococcus aureus
Upper Respiratory Tract bacteria
Normal: viridans streptococci & anaerobes
Transient: neisseria, streptococcus pneumonia, haemophilus influenza
GI bacteria
anaerobes, enterococci
Genitourinary bacteria
lactobacillus
Bacterial Pathogenicity depends on…
host, environment & virulence factors
Virulence factors
slimes/biofilms, ability to evade phagocytosis & proteases, toxins, adhesions, flagella
Virulent v. opportunistic pathogens
Virulent–have virulence factors that cause disease
Opportunistic–lack classic virulence and only cause disease in immunocompromised ppl
Bacterial metabolism (4 kinds)
- anaerobic
- aerobic-make superoxide dismutase and catalase to eliminate toxic O2 byproducts
- facultative
- -microaerophilic–need a little O2
What can bacteria synthesize that we only get from our diet?
Folate
Cell replication in bacteria (2 enzymes)
DNA gyrase and topoisomerase allow chromosomes to unwind during replication
