STUDY GUIDE EXAM 1 Flashcards
Bacillus cereus
Gm +
Bacillus subtilis
Gm +
Clostridium spp.
Gm+
Corynebacterium xerosis
Gm +
Enterobacteria aerogenes
Gm -
Enterococcus faecalis
Gm -
Escherichia coli
Gm -
Pseudomonas aeruginosa (BSL2)
Gm-
Micrococcus luteus
Gm+
Mycobacterium smegmatis
Gm +
Salmonella typhymurium
Gm+
Serratia marcescens
Gm-
Staph aureus (BSL2)
Gm+
Staph epidermidis
Gm+
Strep mitis
Gm+
Strep mutans
Gm+
Strep salivarius
Gm+
Strep sanguis
Gm+
special methods used to minimize contamination when handling microorganisms
aseptic technique
microorganisms are transferred from one medium to another for fresh growth
subculturing
GRAM STAIN: what is the primary stain?
crystal violet
GRAM STAIN: what is the mordant?
iodine
GRAM STAIN: what is the destain?
alcohol wash
GRAM STAIN: what is the counterstain?
safranin
GRAM STAIN: what species are used?
Staph aureus +
E. coli -
B. cereus +
ACID FAST STAIN: what is the primary stain?
carbol fuchsin + triton X detergent
ACID FAST STAIN: what is the destain?
acid alcohol
ACID FAST STAIN: what is the counterstain?
methylene blue
ACID FAST STAIN: species
M. smegmatis
staph aureus
ACID FAST STAIN: what color do acid-fast organisms stain?
red/pink
ACID FAST STAIN: what color do non-acid fast organisms stain?
blue
SPORE STAIN: primary stain
malachite green
SPORE STAIN: destain
heat/water
SPORE STAIN: counterstain
safranin
SPORE STAIN: species
clostridium & bacillus
SPORE STAIN: what color do the spores remain with heat?
malachite green
CAPSULE STAIN: primary
crystal violet
CAPSULE STAIN: counterstain
copper sulfate
CAPSULE STAIN: species
Klebsiella pneuonia
The properties of the bacterial cell wall determine how the bacterial cell will retain different _____
stains
inhibits the growth of one type of bacteria while allowing the growth of another.
facilitates bacterial isolation
selective media
examples of selective media
phenylethyl alcohol agar
distinguishes among morphologically & biochemically related organisms
may change bacteria phenotype, or the appearance of the media may change as a result of bacterial metabolism
differential media
PEA: what makes it selective?
gram + species grow well
PEA: selective for
S aureus (gm + organisms)
PEA: inhibits
E. coli (gm -)
PEA: what species grows?
S. aureus
PEA: what species is inhibited?
E. coli
PEA: genus & species
E. coli, E. faecalis, S. aureus
MANNITOL SALT: what makes it selective?
Salt concentration
MANNITOL SALT: selective for
halophiles & staph
MANNITOL SALT: inhibits
bacterial growth (besides staph)
MANNITOL SALT: carbohydrate
mannitol
MANNITOL SALT: indicator
phenol red
MANNITOL SALT: appearance for pH
pH below 6.8 = yellow (fermenters)
pH at 6.8 - 8.2 = red (non-fermenters)
pH 8.2 and above = fuschia
MacConkey: what makes it selective?
contains crystal violet- inhibits cell redox
MacConkey: selective for
gm - bacteria
MacConkey: inhibits
growth of gm +
MacConkey: carbohydrate
lactose
MacConkey: indicator
neutral red
MacConkey: appearance
fermenters = pink (bile salts ppt out, neutral red absorbed onto colony: E. coli)
non-fermenters = tan (salmonella typhi)
EMB: what makes it selective?
lactose fermentation
EMB: selective for
gm - bacteria
EMB: inhibits
growth of gm + bacteria
EMB: carbohydrate
lactose
EMB: indicator
methylene blue
EMB: appearance
E. coli is metallic green: high lactic acid dyes into surface of colony
lactose fermenter are thick & pink (enterobacter aerogens)
non-lactose fermenters are colorless (S. typhi)
complete lysis, media is color depleted
beta
example of beta
Strep lancefield
Staph aureus
incomplete lysis, results in greenish halo around bacteria
alpha
example of alpha
Strep mitis
Strep pneumonia
no lysis, no change in media
gamma
example of gamma
Strep salivarius
E. faecalis
Known ingredients in carefully measured concentrations, typically a single sugar as the carbon and
energy source, maybe an inorganic nitrogen source, various mineral salts and/or growth factors.
The exact chemical composition of the medium is known. Example: Glucose salt broth
defined
Protein: partially digested organic material from soy, yeast, or animal proteins (peptone and
tryptone) from milk or meat. Glucose or other sugars are the main carbon and energy source. The
combination of peptides + sugar creates a medium rich in organic nutrients and minerals. The exact
chemical composition is unknown. Example: TS (Tryptic Soy), Beef heart infusion broth
complex
Can be complex or chemically defined but is supplemented with growth-promoting or growth-
inhibiting additives to encourage or suppress growth. The additives may be species- or organism-
selective. Example: PEA agar, Crystal Violet Agar
selective
Contains a dye or indicator that can be used to distinguish one organism from another on the same
plate. Examples: Mannitol Salt, MacConkey, EMB (all are Selective and Differential)
differential
Contains added components (like RBCs or Fetal Calf Serum) to encourage the growth of fastidious
organisms needing a rich nutritional environment. Example: Blood Agar (Enriched and Differential)
enriched
species that is an example of gamma hemolysis
enterobacter aerogenes (klebsiella aerogenes)
species that is an example of beta hemolysis
enterococcus faecalis (BSL2)
species that is an example of alpha hemolysis
alcaligenes faecalis
what species forms beta hemolysis around the colonies of streptococci grown under routine aerobic positions
streptolysin S
what species is oxygen-labile (O2 kills it)
streptolysin O
what species is oxygen stable?
streptolysin S
(Gm+ cocci) excretes an enzyme called
dextransucrase (glycosyl transferase), which
polymerizes sucrose into a large polymer, dextran
(dental plaque), plus fructose.
S. mutans
clings to the teeth and forms dental plaque,
in which bacteria reside and ferment fructose with
the formation of lactic acid = Dental caries
dextran
(Gm+ rod) produces lactic acid and
other organic acids that reduce the oral acid
concentration to a pH of less than 5. At this pH,
decalcification occurs and dental decay begins
L. acidophilus
SNYDER AGAR: is it selective, differential, enriched?
differential
SNYDER AGAR: what is it selective for?
lactobacillus in saliva
SNYDER AGAR: inhibits
growth of other bacteria
SNYDER AGAR: species
S. mutans
L. acidophilus
what does MSAT metabolize?
sucrose & glucose
MSAT: produces gummy mucoid colonies
strep salivarius
produces undulate colonies, with a granular
“Frosted-glass/Blue crystal”
appearance due to dextran synthesis
Strep mutans
MSAT: metabolize glucose only
strep mitis
enterococcus
are small, flat,
light blue.
strep mitis
are small,
and reduce tellurite to
produce dark, blue-black
colonies
enterococcus
Streptococcus mutans results in glucose and fructose. The glucose is then converted into dextran by Streptococcus mutans, while the fructose is converted into lactic acid by Lactobacilli. The Oxidase test is used to detect the presence of cytochrome c oxidase.
degradation of sucrose
