Chapter 8 - Mahon Flashcards
Key ingredients of Anaerobic blood agar
intact sheep RBCs
vitamin K
yeast extract
Use of anaerobic blood agar
isolation and subculturing obligate anaerobes
key ingredients of CHOC agar
hemolyzed sheep RBC
hemoglobin
NAD
CHOC agar use
primary plating and subculture fastidious bacteria (Haemophilus, Neisseria)
key ingredients of Hektoen enteric agar
carbohydrates (lactose, salicin, sucrose)
bile salts (inhibits gram + and nonpathogenic enteric bacteria)
selective and differential medium for primary plating of stool spx to recover intestinal pathogens (Salmonella)
Hektoen enteric agar
MAC agar key ingredients
lactose
low conc. bile salts (inhibits gram + but permits growth of gram -)
selective and differential medium for isolation of gram - bacteria; used for primary plating and subculturing
MAC
modified thayer martin ingredients
choc agar base
antimicrobial agents (vancomycin, colistin, trimethoprim, nystatin)
selective primary plating medium for the recovery of Neisseria gonorrheae and N. meningitidis
MTM
SDA ingredients
dextrose (glu)
antimicrobials to inhibit bacteria
SBA ingredients
intact RBCs
primary plating and subculturing of most bacterial isolates
SBA
T/F
Organisms that grow on CHOC also grow on SBA. But not all organisms that grow on CHOC will grow on SBA.
T
CHOC allows growth of fastidious organisms (highly fastidious - Haemophilus, Neisseria)
These organisms will not grown on SBA
growth on SBA and CHOC but not on MAC
indicative of:
gram + or fastidious gram - bacillus or coccus
best used to characterize gram - rods because lactose fermenters can be differentiated from lactose nonfermenters
MAC
colonies of lactose fermenters in MAC
pink, dark pink, or red colonies
(as pH decreases)
colonies of nonlactose fermenters in MAC
colorless
differentiation of lactose to nonlactose fermenters screens for
enteric pathogens from stool culture (most are NON LACTOSE FERMENTERS)
partial lysing of RBCs in SBA around and under the colony that results in GREEN discoloration
a-hemolysis
ex of organisms that produce a-hemolysis
s. pneumoniae
viridans strep
complete clearing of RBCs in SBA
b-hemolysis
produces a wide, deep, clear zone of b-hemolysis
group A b-hemolytic strep
(S. pyogenes)
produces a narrow, diffuse zone of b-hemolysis close to the colony
group B b-hemolytic strep (S. agalactiae)
L. monocytogenes (gram + rod)
a visual comparison between genera and species
size of colonies
description of colony size
large
medium
small
pinpoint
description of colony margin
smooth
rough or rhizoid
filamentous
irregular
with filamentous appearance, described as Medusa heads
Bacillus anthracis colonies
ex of genera that may swarm in blood and CHOC agar
Proteus (esp. mirabilis)
hazy blanket of growth on the surface that extends well beyond the streak lines
swarming
produce colonies that have a dry appearance and umbonate center growing on SBA
diphtheroids
produce colonies that are creamy, white with dull surface, with feet/pedicles
yeasts
produce moist, creamy white to yellowish colonies
Staphylococci
description of colony elevation
raised
convex
flat
umbilicate (depressed center/concave)
umbonate (raised/bulging center)
bacteria typically produces umbilicate colonies
S. pneumoniae
bacteria typically produces convex colonies
S. aureus
produces flat colonies
b-hemolytic strep
description of colony density
transparent
translucent
opaque
have semi opaque colonies with the organism concentrated at the center of the colony
bull’s eye colony
group B (S. agalactiae)
shiny, similar to half-pearl colony in blood containing media
B. pertussis
term used to describe a particular GENUS in general
color
with white colonies
coagulase-neg staph
with yellow or off-white colonies
micrococcus
neisseria (non pathogenic)
with gray colonies on SBA
gram negative rods
detemined by touching the colony with sterile loop
consistency
description of colony consistency
brittle (splinters)
creamy (butyrous)
dry
waxy
sticky
with creamy colonies
S. aureus
with sticky colonies
certain Neisseria
with brittle, crumbly, and wrinkled colonies
Nocardia
with dry colonies (except for mucoid types) wherein when pushed by a loop, whole colony remains intact
beta hemolytic strep
inherent characteristics of a specific organism confined generally to the colony
pigment
how is pigment production enhanced
grow bacteria at ROOM TEMP
with green, sometimes metallic sheen pigment
P. aeruginosa
with brick red pigment, esp. at RT
Serratia rubidaea
with blue pigment
Kluyvera
with purple pigment
C. violaceum
with brown to black (anaerobic) pigment
P. melaninogenica
with old sock odor (evident when grown on mannitol salt agar)
S. aureus
with fruity or grapelike odor
P. aeruginosa
with putrid odor
P. mirabilis
with musty basement, mousy or mouse nest smell
Haemophilus spp.
with freshly plowed field odor
Nocardia spp.
forms a large, rough, greenish, hemolytic colonies on SBA
B. cereus
forms a small fuzzy edged colony with an umbonate center on SBA or choc
Eikenella corrodens
translucent, may resemble water droplet
umbilicate, or flat w/ “penny” edge
entire margin, wide and strong zone of alpha hemolysis
S. pneumoniae
translucent, grayer, rougher margin, umbonate center
a-hemolytic viridans strep
pinpoint brittle translucent
gray that may turn brownish on continued incubation
large deep zone of b-hemolysis
S. pyogenes
medium sized colony compared to S. pyogenes
creamy, gray, small, diffuse zone of b-hemolysis
often need to remove colony with a loop to see b-hemolysis
bull’s eye colony
S. agalactiae
large, flat, convex, or umbonate center after 24hr
shiny, moist, creamy, white to offwhite
Staphylococcus
smaller than staphylococci
convex, grows upward more than outward
creamy, white, dull surface
tiny projections at the base of colony after 24hr
Candida albicans (yeast)
exhibits vine or streamer (more prevalent toward the tube bottom) in liquid media
streptococci
exhibits puffed balls in liquid media
streptococcal spp
produce “scum” at the surface of thioglycollate
yeast
produce turbidity when growing in thioglycollate. gas bubbles at the surface and middle
enterics
produce “scum” at the sides of thioglycollate with diffusable green pigment and metallic sheen at the surface
pseudomonas spp
