Practical 3 Flashcards
Define obligate intracellular parasite
Must go inside a living host organism to replicate
A virus that infects bacteria
Bacteriophage
Must go inside a living host organism to replicate
Obligate intracellular parasite
How does a medium used for bacterial growth differ from media used for bacteriophage growth?
Ordinary agar or broth media is suitable for growing bacterial cultures. Bacteria growing in lab media can serve as the host cell for growing viruses that infect bacteria.
What is the purpose of making serial dilutions of the T4 phage?
To obtain a countable plate in which 30-300 individual plaques
What is a viral plaque and what does it represent?
A plaque is an area of clearing in a confluent lawn of bacterial growth. A plaque represents the spot where a virus has landed, infected the bacteria it encountered, and lysed them.
What purpose does the E. coli serve in this procedure (Viral Plaque Assay)?
E.coli serves as the host cell for the T4 bacteriophage
The purpose of a viral plaque assay is to determine the number of bacteriophage in a sample. True or false?
True
A plaque represents where the E. coli have replicated from one cell into millions of cells
False
PFU stands for “plaque forming units”.
True
PFU
Plaque forming units
What is considered a countable # of plaques
30-300
Viruses that burst the host cell and kill them are called
Lytic viruses
Lytic viruses burst open their bacterial host cell once the appropriate number of viruses has been synthesized
True
Study of fungus
Mycology
What kind of organisms are fungi?
Eukaryotic organism
Dimorphic fungi
Grows as yeast or mold depending on the environment
What type of media is used to grow fungi?
Sabouraud’s Agar
What is speical about Sabouraud’s Agar?
Simple nutrients (gluocose and peptone)
pH of 4.5-5.6
What pH inhibits bacterial growth?
4.5-5.6
Microscopically, yeast cells are
unicellular and round to oval
Fungi that grow as mold produce
Multicellular filaments called hyphae
Asexual spores produced by molds
Sporangiospores
Conidiospores
Explain why Coccidioides immitis is a dimorphic fungus?
It can grow as a yeast or mold depending on environmental conditions
What are the growth differences between fungus and bacteria?
Fungi grow slower, at a lower temperature, and a lower pH
Define blastospore
Asexual reproductive forms of yeast that bud from parent cell
Define pseudohyphae
Successive blastospores remaining attached to the original parent cell
Successive blastospores remaining attached to the original parent cell
Pseuodohyphae
Asexual reproductive forms of yeast that bud from parent cell
Blastospore
Define septate hyphae
Fungal hyphae filaments separated by a cross wall
Fungal hyphae filaments separated by a cross wall
Define septate hyphae
Explain the difference between vegetative hyphae and aerial hyphae
Vegetative hyphae grow on or down into the agar surface to extract nutrients from the medium. Aerial hyphae grow above the agar surface
grow on or down into the agar surface to extract nutrients from the medium.
Vegetative hyphae
grow above the agar surface
Aerial hyphae
inside a sac-like structure.
Sporangiospores
are formed on hyphae and may be single or multicelled.
Conidiospores
Difference between sporangiospores and conidiospores
Sporangiospores are inside a sac-like structure. Conidiospores are formed on hyphae and may be single or multicelled.
Asexual reproductive spores are produced by ____ hyphae
Aerial hyphae
Two types of asexual spores are
Sporangiospores and Conidiospores
Saccharomyces and Candidia are ____ while
Penicillium, Rhizopus, and Aspergillus are _____
Yeast
Mold
What is the plaque equation?
Plaque count X Plate Dilution x 10 (if you plated 0.1 ml)
Staphylococcus and Micrococcus are catalase positive
True
Staphylococcus and Micrococcus are Gram (Blank)
Positive
Staphylococcus epidermidis can be an opportunist
True
Staphylococcus and Micrococcus grow in
Clusters
Streptococcus pneumoniae mostly causes
Middle ear infections
Group A Streptococcus
cause ninety percent of acute streptococcal infections in humans. It is the cause of “strep throat”
Streptococcus mutans is
another viridans streptococcus associated with dental caries and plaque.
Streptococcus can/cannot produce catalse?
Cannot (negative)
Streptococcus grows in
pairs or chains
- Alpha Hemolysis
a partial damage of the red blood cells which reduces the hemoglobin to methemoglobin. This partial damage is shown as an olive green to brown discoloration in the media surrounding the bacterial colony on the blood agar.
-
Beta Hemolysis
ex: S. pyogenes + Group C Strep.
a complete lysing of the red blood cells. This is demonstrated by a complete clearing of the red blood cells in the media around a colony leaving only the color of the base (TSA) media.
- Gamma Hemolysis
the lack of hemolysis. There is no damage to the red blood cells in the media.
Rhizopus mold looks
White on top and bottom
Cottony
Like a tootsie pop
Identifiy this mold
Aspergillus
-Black on top
-Reverse pigment is yellow
-Velvetty (medium)
-Aerial Hyphae
-Dandelion
Identify this mold
Penicillium
-Green on top
-Reverse pigment is yellow
-Wooly texture (low)
-Skeleton hands
Yeast from macro looks
Moist, white, creamy, pearl-like colonies
Mold from macro looks
Fuzzy
Mold from micro looks
Hyphae + Spores
Yeast microscopically are
Oval shaped and bigger than bacteria
People who harbor a pathogen but exhibit no symptoms
Define carrier
Define MRSA
Methicillin resistant Staphylococcus aureus
Which genus and species of staphylococcus or micrococcus is coagulase positive?
Staphylococcus aureus
The strains of Staph and Micro:
Staphylococcus: auereus + epidermidis
Micrococcus: roseus + luteus
What Staph bacteria are SALT TOLERANT on mannitol salt
(Staph + Micro)
Staphylococcus aureus
Staphylococcus epidermidis
What bacteria are positive for MANNITOL FERMENTATION (turned yellow)?
(Staph + Micro)
ONLY Staphylococcus aureus
What bacteria are SALT TOLERANT?
Staphylococcus auereus
Staphylococcus epidermidis
What bacteria produce a + in NITRATE REDUCTION? (red color change)
Staphyloccocus aureus
Staphyloccous epidermidis
Micrococcus roseus
Virulent
Extreme disease causing
3 diseases that Staphyloccocus aureus can cause are
Toxic shock syndrome
Wound infections
Food poisoning
st
Coagulase is an enzyme produced by both Staphylococcus aureus and Staphylococcus epidermidis
False, only S. aureus
A mannitol positive colony on mannitol salt agar is indicated by the presence of a pink color around the colony
False
Micrococcus and Staphylococcus can grow equally well on media that contains 7.5% salt
False
Streptococcaceae family includes:
Streptococcus: sanguinis + pneumoniae + pyogenes + Group C
Enterococcus: faecalis
They are differentiated from Staphylococcus and Micrococcus by the _____ reaction. The Streptococcaceae cannot produce ________.
Catalase; catalase
Streptococcus and Enterococcus are Gram-positive cocci in ______ or ______ when stained from a broth.
Pairs; chains
Some bacteria produce hemolysins that damage the membrane of red blood cells.
Hemolysis
________________ colonies are larger, convex, opaque, and frequently pigmented.
________________ colonies are smaller, often translucent to semi-opaque.
Staphylococcus; Streptococcus
________________ colonies are larger, convex, opaque, and frequently pigmented.
________________ colonies are smaller, often translucent to semi-opaque.
Staphylococcus; Streptococcus
Which enzyme helps differentiate all Staph from Strep
Catalase
The principle and reagant used in catalase and coagulse test?
Principle: does the bacteria produce the enzyme?
Catalse reagant: hydrogen peroxide
Coagulase reagent: rabbit plasma
Staphylococcus aureus + epidermidis COAGULASE test result:
Aureus: +
Epidermidis: -
Staphylococcus aureus + epidermidis MANNITOAL SALT and FERMENTATION test result:
Growth on salt: aureus + epidermidis
Fermentation of Mannitol: aureus
Nitrate + or -
Staph and Micro microbes
+: aureus, epidermidis, roseus
-: Micrococcus luteus
Do Enterobacteriacieae Ferment Glucose?
Yes
Enterobacteriaceae do not ferment glucose. T or F?
False
MacConkey Agar is…
is a selective and differential media
It is used to grow Gram-negative bacilli and differentiate their ability to ferment lactose.
Has Bile Salts + Crystal Violet Dye
Are Enterobacteriaceae are gram + or -
Gram negative bacilli
What organisms are Alpha Streptoccocus and Optochin Sensitive?
Alpha: S. sanguinis + S. pneumoniae
Resistant: S. sanguinis (negative)
Sensitive: S. pneumoniae (positive)
What organisms are Beta Streptococcus and A or C Group
Beta: S. pyogenes + Group C Strep.
A: Streptococcus Pyogenes
C: Group C Streptococcus
Test results for ability to hydrolyze Bile Esculin
ex: Enterococcus faecalis
+: brown/black media
-: no color change
What does glucos fermenation look like?
Yellow: + positive
Red: - negative (no color change)
Identify this macroscopically and describe it
Aspergillus mold
-Black
-Velvetty
-AERIAL hyphae
-YELLOW reverse pigment
Identify this microscopically
Aspergillus mold
Identify this macroscopically and describe it
Penicillium mold
-Green on top
-WOOLY texture
-YELLOW reverse pigment
Identify this microscopically
Penicillium mold
Identify this macroscopically and describe it
Rhizopus
-White on top + bottom (reverse pigment)
-COTTONY
Identify this microscopically
Rhizopus
-Looks like tootsie roll or tootsie pop
What is an “enteric” organism?
Normal flora of the gastrointestinal tract
Motility media is inoculated with an inoculating loop
False, inoculating wire
In an organism can use citrate as its sole carbon source the media will appear what color?
Blue
Enterobacteriaceae are the most frequently encountered microbes in the clinical microbiology laboratory
True
This enzyme catabolized tryptone into indole and pyruvic acid
tryptophanase.
If urease is present the pH of the culture media will decrease
False
Which organisms must be stored in a candle jar because they’re microaerophiles?
Some Streptococcus
Only grows Gram + bacteria:
Determines Hemolytic Properties
Contains: Antibiotic + Acid
CNA (blood) Agar
Test results of MacConkey Agar:
Growth on media = Gram-negative bacilli
***Determine the ability to ferment lactose:
Hot Pink colonies= Positive for lactose fermentation
Clear colonies = Negative for lactose fermentation
How does MacConkey Agar Select for Gram- bacteria
Inhibiting growth by using bile salts and CV dye
Fermentation of lactose will be pink
The truly enteric pathogens in the Enterobacteriaceae family include:
Salmonella: typhoid fever
Shigella: bacterial dysentery
How are culture media designed to detect if bacteria can produce a specific enzyme?
Substrates are incorporsted into the media along with an indicator system to detect products
What is the substrate of the MRVP test?
Glucose
What is the substrate of the indole test?
Tryptone
Name three Enterobacteriaceae normally found in the gastrointestinal tract
Escherichia coli, Enterobacter, Klebsiella
Name one of many commercial test systems used to identify Gram negative bacilli in clinical labs
API20E
Enterotube
What are the two major groups of Gram-negative bacilli and what are the common characteristics of each group?
Enterobacteriaceae ferment glucose and do not produce oxidase. Nonenterobacteriaceae (non fermenters) do not ferment glucose and many are oxidase positive
What carbohydrates are in the Kligler Iron Agar media?
Glucose and lactose
Why is MacConkey agar considered a selective and differential media?
It contains bile salts and crystal violet that inhibit the growth of Gram positive bacteria therefore selecting for Gram negative bacteria. It contain lactose and differentiates based on lactose fermentation
Nitrate broth is used to determine
an organism can reduce nitrate
How did Lancefield divide the beta-hemolytic streptococci into groups?
Based on the C polysaccharide extracted from the cell walls
What is the species name of Lancefield Group B streptococci?
Streptococcus agalactiae
Define VRE
vancomycin resistant Enterococcus
Has been recognized as potentially dangerousfor newborn Babies
Beta-hemolytic Group B Streptococcus
The cause of “strep throat” “ach”
Beta-hemolytic Group A Streptococcus
