Usmle First Aid Flashcards
(T/F) The outer membrane
for G+ and the cell
membrane for G- act as
major surface antigens.
FALSE: they DO act a major
surface antigens BUT the
outer mb for G- and the cell
membrane for G+
Are endotoxins heat stable?
yes, stable at 100C for 1 hr.
Are endotoxins secreted from
cells?
NO
Are endotoxins used as
antigens in vaccines?
no, they don’t produce
protective immune response
Are exotoxins heat stable?
no, destroyed rapidly at 60C
(exception: Staphylococcal
enterotoxin)
Are exotoxins secreted from
cells?
YES
Are exotoxins used as
antigens in vaccines?
Yes, TOXOIDS are used as
vaccines
Describe the chemical
composition of
peptidoglycan.
Sugar backbone with crosslinked
peptide side chains.
Describe the major
components of a G- cell wall.
inner and outer lipid bilayer membranes - thin layer of peptidoglycan - periplasmic space - contains lipopolysaccharide, lipoprotein and phospholipid
Describe the major
components of a G+ cell wall.
one lipid bilayer membrane -
thick layer of peptidoglycan -
contains teichoic acid
Describe the process of
conjugation.
DNA transfer from one
bacterium to another.
Describe the process of
transduction.
DNA transfer by a virus from
one cell to another
Describe the process of
transformation.
purified DNA is taken up by a
cell
Does endotoxin induce and
antigenic response?
no, not well
Does exotoxin induce and
antigenic response?
Yes, induces high-titer
antibodies called antitoxins
Give two general functions of
peptidoglycan
Gives rigid support - protects
against osmotic pressure
How are Group A and Group B
Strep primarily differentiated?
Group A are Bacitracin
sensitive - Group B are
Bacitracin resistant
How are the pathogenic
Neisseria species
differentiated?
on the basis of sugar
fermentation
How are the species of
Streptococcus primarily
differentiated?
on the basis of their
HEMOLYTIC capabilities
List the four phases of the
bacterial growth curve.
Lag phase - log (exponential)
phase - stationary phase -
death phase
Name 2 G- rods that are
considered slow lactose
fermenters.
Citrobacter and Serratia
Name 3 G- rods that are
considered fast lactose
fermenters.
1) Klebsiella 2) E. coli 3)
Enterobacter
Name 3 G- rods which are
lactose nonfermenters and
Oxidase(-)?
Shigella, Salmonella, Proteus
Name 4 bacteria that use IgA
protease to colonize mucosal
surfaces.
1) Strep. pneumoniae 2)
Neisseria meningitidis 3)
Neisseria gonorrhea 4) H. flu
