Clinical Microbiology Flashcards
What is a Virus?
- Noncellular
- May not be living
- Contains DNA & RNA + Protein coat
- No independent reproduction
What is Bacteria?
- Prokaryotic microbes
- Unicellular
- Pore size
- Reproduced with binary fission
- Live independently in soil, water, plants, etc..
- Normal flora in humans
- Cause disease
Fungi, Yeasts, Molds has?
Hyphae (fuzz)
What is “Protozoa and Amoeba”
- Mostly single celled
- Eukaryotic
- Can be free living or in human hosts
What is Rickettsia, Chlamydia, Spirochetes?
Can adapt inside the human body
Structures: Capsule
- Slime layer
- Makes phagocytosis harder (WBC defense)
- Increases virulence
Structures: Cell Wall
Contains peptidoglycan (gram+, gram-)
Structures: Flagella
Motility
Structures: Plasmid
- Extra set of external circle DNA
- Allows microorganism to replicate independently (antibiotic resistance)
Temperature Classifications: Cold to Hot
- Cryophiles
- Psychrotrophs
- Mesophiles
- Thermophiles
- Hyperthermophlies
Gas Classifications: Obligate
Specific conditions
Gas Classifications: Facultative
Flexible conditions
Temperature Classifications: Aerobic
Needs O2
Temperature Classifications: Anaerobic
Doesn’t need O2
Temperature Classifications: Microaerophilic
Low O2 (campylobacter)
Temperature Classifications: Capnophile
Needs CO2
Temperature Classifications: Facultative Anaerobe
Prefers O2; can survive without
Temperature Classifications: Fastidious
Requires specific nutrition
Media: Thioglycollate Broth
Allows bacteria to choose it’s own conditions to tell you if it’s aerobic, anaerobic, microaerophilic etc.
Media: Blood Agar
- Enriched
- Non selective
- Differentiates hemolytic reactions (THROAT SWAB)
Media: Chocolate Agar
Enriched for fastidious organisms
Media: Thayer Martin
- Selective
- Contains antibiotics to isolate for neisseria
Media: Modified Thayer Martin
- Selective
- Additional antibiotic to inhibit proteus
Media: Macconkey
- Selective for gram-
- Differential for lactose fermenters
Media: Salmonella Shigella
- Selective for salmonella, shigella
- Differential lactose fermenter
Media: Sodium Thiosulphate
- Selective for salmonella, shigella
- Differential sulphur reducers
Media: Hektoen Enteric Agar
- Selective for gram-
- Differential sulphur reducers
Media: Phenylethyl Agar (PEA)
Selective for gram+
Media: CLED Agar
Differential for urinary microbes
Media: Sheep Blood Agar
Heated to 75-80C to make chocolate agar
Catalase Test
- Hydrogen peroxide bubbles
- Differentiates staph and strep (+staph, -strep)
Coagulase Test
- s.auerus produces coagulase
- (+staph aureus, -another staph)
Incubation: Aerobic
- Upside down
- 35C ~ 24-48hrs (35C mimics temp of human host)
Incubation: Anaerobic - Gaspak Jar
Catalyst combines with residual oxygen with hydrogen to make water, removing oxygen
Incubation: Anaerobic - Candle Jar
- Candle burns remaining oxygen
- Creating reduced O2
- Increased CO2 environment - 5%
Incubation: Anaerobic - Campypak
Requires 42C
Microbe Shapes: Coccus
- Sphere, ball
- Cluster = staphylo
- Chain = Strepo
Microbe Shapes: Bacillus
- Rod
- Single, pair, chain, random (endospores)
Microbe Shapes: Spiral
- Coil
- Motile
Staining: Positive Stain
Cells stained
Staining: Negative Stain
Background stained (India ink)
Staining: Differential Stain
- Gram stain
- Acid Fast stain
Gram Stain: Chemicals
Crystal violet - iodine - acetone - safranin
What does Gram+ Peptidoglycan do?
Traps crystal violet inside, making it purple
What does Gram- Peptidoglycan do?
Crystal violet gets flushed out; safranin dyes it pink
Blue Stain used in Acid Fast Stain (Ziehl-neelson)
Carbol-fuchsin/methylene blue
Kirby Bauer Test for Antibiotic Susceptibility
Muller Hinton Agar:
- Streak lawn
- Add antibiotic discs
- incubate
- Measure zone of inhibition
Swabs: Sterile
- Blood
- Body fluids
- Tissues
- Bone marrow
Swabs: Non-sterile
- Throat
- Skin
- Wound
- Feces
Swabs: Wounds
Deep = anaerobic
Surface = aerobic
Swabs: GI (Gastrointestinal)
- Gram-like Enterobacteriaceae
- Salmonella, shigella
- Campylobacter
- E. Coli
Swabs: V Swab
Polyester Tip:
- Cotton toxic to gonorrhea
- Wooden stick toxic to chlamydia
Swabs: Names
- Amie’s transport media
- Stuart’s transport media
- Cary-Blair transport media (GI parasites)
Inoculating Plates
- Start with non-selective
- Move towards selective
- ANA, BA, CA, Mac
UTI - Clean Catch Specimen: Normal Range
100 - 1000 colony forming
UTI - Clean Catch Specimen: Contaminated
- More than 1000
- Less than 10,000
UTI - Clean Catch Specimen: UTI
10,000 - 100,000+
Mycology: Mycoplasma
Does not have cell wall
Mycobacterium Stains: Acridine Orange
Confirms bacteria in blood (then gram stained)
Mycobacterium Stains: Auramine-Rhodamine
Acid fast mycobacterium (mycolic acid has affinity for stain)
PCR - Polymerase Chain Reaction: Step 1
Denaturation:
- Break down DNA double helix @ 94C
PCR - Polymerase Chain Reaction: Step 2
Annealing/Priming:
- Small fragments of new DNA strands built @ 55-65C
PCR - Polymerase Chain Reaction: Step 3
Extensions:
- Enzyme; polymerase catalyzes new strands @ 72C
RNA Virus
RNA must be built into DNA before denaturation step can take place
Assorted Terminology from Review: Thermolabile
Sensitive to heat; damaged by heat
Assorted Terminology from Review: EDC or EDD
Medical acronym for pregnancy due date
Assorted Terminology from Review: TLV
Threshold Limit Value
Assorted Terminology from Review: Fomite
Inanimate object; can be contaminated with infectious agent
Gram’s Staining Steps
- Heat fix
- Primary stain - Crystal violet; 1 min
- Rinse with water; back of slide
- Mordant - iodine; 1 min
- Rinse with water; back of slide
- Decolorizer - Acetone alcohol; 3-5 sec
- Rinse with water; back of slide
- Counterstain - Safranin; 1 min
- Rinse with water; back of slide
- Anaerobes/aerobes
Gram Staining Results if Steps Missed
Pink = Negative
Blue = Positive
Zeihl-Neilson Staining Steps
- Heat fix
- Flood slide; Carbol Fuchsin
- Heat slide slowly; maintain steam; 5 min
- Rinse with water; back of slide
- Flood slide; 3% acid-alcohol; 5 mins; allow to decolorize
- Rinse with water; back of slide
- Flood slide; methylene blue; 1 min
- Rinse with water; back of slide
Human Virus Size
20-200 nm; diameter
Bacteria Virus Size
2-3 um; length
What Causes Strep Throat?
Group A Streptococcus:
- Spread through contact with droplets with infected person
Culture Media: Alpha-Hemolysis
- Damaged RBC in blood (not lysis)
- Media translucent; green-ish tinge around colonies
Culture Media: Beta-Hemolysis
- Lysis of RBC
- Media looks completely transparent around colonies
Rickettsia: Found in
- Ticks
- Lice
- Fleas
- Mites
- Chiggers
- Mammals
What is Saponin?
- Detergent-like substances showing antibacterial
- Anticancer potential
How to do Lake Staining?
Dye + Mordant
What causes results of Gram Staining?
Gram positive = Higher peptidoglycan
Gram negative = Higher lipid
Agar melts around what Temperature?
85C
Agar Solidifies around what Temperature?
34-42C