Bacterial Basics - structure, staining patterns, genetics Flashcards
Gram staining challenges of mycobacteria
patchy - high lipid resists stain
cell wall of mycolic acid
gram staining challenges of mycoplasma
no cell wall - sterols for plasma membrane
gram staining challenges of treponema
gram -
corkscrew
need darkfield micro
gram staining challenges of Legionella pneumophila
branch chained fatty acids cell wall
Gram + vs Gram - cell walls
Gram +:
Lipoteichoic acids: contain lipids and telchoic acid, induces IL1 and TNFa
Thick peptidoglycan cell wall
Gram -:
Outer membrane - site of endotoxin (LPS), induces IL1, TNFa
Thin peptidoglycan layer w/in periplasmic space (site of b-lactamase)
Conjugation
pilus transfers DNA to another bacterium
“Conjugal visit”
Virulence factor
makes it stronger
capsule
Quellung reaction
anti-capsule serum added causes capsule swelling under microscope
Encapsulated bacteria
“Even Some Pretty Nasty Killers Have Shiny Bodies”
E coli S. pneumo Pseudomonas aeruginosa Neisseria meningitidis Haemophilus influenzae type B Salmonella typhi Group B strep
organisms causing sepsis and death in splenectomy patients w/ overwhelming infection
"SHiN" Strep pneumo Haemophilus influenza Neisseria meningitidis
Vaccines available
Capsules virulence factor
Glycocalyx
gelatonous, polysaccharide coating
aids attachment to foreign material - indwelling cathether
when organized and firmly adherent –> capsule
When loosely adherent and less organized –> slime/biofilm
- resistent to abx
- difficult to remove
Encapsulated yeast
cryptococcus neoformans
- -> meningitis in AIDS
- India ink stain
Prokaryote ribosomes
70S - 50S, 30S
Eukaryote ribosomes
80S - 60s, 40S
Plasmids
genetic material separate form DNA
carry genes for abx resistance or toxin production
transferred in conjugation
Transformation
lysed cell DNA taken up by living bacterium
incorporated into chromosomal DNA
Transposons
small DNA segment that can self excise and relocate toa nother section of DNA or to a plasmid
can carry abx resistance or virulence factor
Transduction
phage dependent
phage attaches to bacterium, injects its DNA
Some bacterial DNA can be packaged inside viral capsid
-released when bacteria ruptures –> new bacteria
Pigment producing bacteria
S. aureus - large golden colonies
Actinomyces isreali - yellow (sulfur) granules
Pseudomonas aeruginosa - blue-green pigment
Serratia marcescens - red pigment
Obligate anaerobes
clostridium sp
Actinomyces
Bacteroides
Use Metronidazole, clindamycin for anaerobes
