Chapter 8 - Mahon Flashcards by LEDESMA, Anne Gelika

Key ingredients of Anaerobic blood agar

intact sheep RBCs
vitamin K
yeast extract

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Use of anaerobic blood agar

isolation and subculturing obligate anaerobes

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key ingredients of CHOC agar

hemolyzed sheep RBC
hemoglobin
NAD

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CHOC agar use

primary plating and subculture fastidious bacteria (Haemophilus, Neisseria)

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key ingredients of Hektoen enteric agar

carbohydrates (lactose, salicin, sucrose)
bile salts (inhibits gram + and nonpathogenic enteric bacteria)

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selective and differential medium for primary plating of stool spx to recover intestinal pathogens (Salmonella)

Hektoen enteric agar

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MAC agar key ingredients

lactose
low conc. bile salts (inhibits gram + but permits growth of gram -)

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selective and differential medium for isolation of gram - bacteria; used for primary plating and subculturing

MAC

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modified thayer martin ingredients

choc agar base
antimicrobial agents (vancomycin, colistin, trimethoprim, nystatin)

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selective primary plating medium for the recovery of Neisseria gonorrheae and N. meningitidis

MTM

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SDA ingredients

dextrose (glu)
antimicrobials to inhibit bacteria

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SBA ingredients

intact RBCs

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primary plating and subculturing of most bacterial isolates

SBA

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T/F

Organisms that grow on CHOC also grow on SBA. But not all organisms that grow on CHOC will grow on SBA.

CHOC allows growth of fastidious organisms (highly fastidious - Haemophilus, Neisseria)

These organisms will not grown on SBA

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growth on SBA and CHOC but not on MAC

indicative of:

gram + or fastidious gram - bacillus or coccus

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best used to characterize gram - rods because lactose fermenters can be differentiated from lactose nonfermenters

MAC

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colonies of lactose fermenters in MAC

pink, dark pink, or red colonies
(as pH decreases)

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colonies of nonlactose fermenters in MAC

colorless

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differentiation of lactose to nonlactose fermenters screens for

enteric pathogens from stool culture (most are NON LACTOSE FERMENTERS)

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partial lysing of RBCs in SBA around and under the colony that results in GREEN discoloration

a-hemolysis

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ex of organisms that produce a-hemolysis

s. pneumoniae
viridans strep

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complete clearing of RBCs in SBA

b-hemolysis

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produces a wide, deep, clear zone of b-hemolysis

group A b-hemolytic strep
(S. pyogenes)

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produces a narrow, diffuse zone of b-hemolysis close to the colony

group B b-hemolytic strep (S. agalactiae)
L. monocytogenes (gram + rod)

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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