Final – 1913L – Flashcards
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Unlock answers| What is the purpose of using Phenol Red Broth |
| Differentiates Enterobacteriaceae. Tests for carbohydrate fermentation and gas production. |
| How to determine carbohydrate fermentation in Phenol Red Broth |
| uninoculated = red (from Phenol Red pH indicator) (+) for fermentation = yellow (-) for fermentation = red |
| How to determine gas production in Phenol Red Broth |
| Gas in durham tube = (+) for gas production No gas in durham tube = (-) for gas production |
| How to read TSI slant results |
| Acidic (A) = yellow Alkaline (K) = red Results are read Slant/Butt (ex. K/A = Alkaline slant and acidic butt) |
| How to determine number of sugars fermented in TSI |
| Glucose-only fermenters will be K/A (one sugar fermented) Glucose, lactose &/OR sucrose will be A/A (at least two sugars fermented) Non-fermenters will be K/K (no sugars fermented) |
| How to determine gas production in TSI |
| Agar lifts form bottom of tube Fissure or crack forms in the agar Bubble visible in the agar |
| How to determine H2S production in TSI |
H2S indicator = ferrous sulfate Black precipitate = positive reaction A positive reaction requires acidic conditions, so if you only see black, it MUST BE acidic (ex. K/Black = K/A H2S (+) |
| Tool for inoculating TSI |
| Needle |
| Gram reaction of organisms differentiated by TSI |
| Gram-negative |
| Family of organisms differentiated by TSI |
| Enterobacteriaceae |
| Organisms Bile Esculin Agar differntiates |
| Inhibits Gram-positive except for Group D Streptococcus, including Enterococcus |
| What are the selective and differential agents in Bile Esculin Agar |
| selective = bile differential = Esculin Indicator = Ferric Citrate |
| How to read Bile Esculin media |
| Black precipitate forms if the organism is Bile Esculin-positive. An organism that doesn't darken the media, is negative. |
| Two main families are differentiated in O-F tubes |
| Differentiates Enterobacteriaceae from Pseudomonadaceae |
| Number of tubes used in O-F test |
| 2 tubes Oxidative tube - no mineral oil added Fermentative tube - mineral oil added |
| How to read O-F media |
| pH indicator - Bromthymol Blue Yellow = acidic pH Green = neutral pH (See slide #15 in PowerPoint #6 for further clarity) |
| Tests involved in SIM media |
Sulfur reduction - H2S reacts with ferrous sulfate for form black precipitate = positive Indole production - Add Kovac's reagent, if you see red = positive Motility - Growth radiating away from stab line = positive (See slide #17 on PowerPoint #6 for further clarity) |
| Family of organisms differentiated by SIM |
| Enterobacteriaceae |
| MIC stands for |
| Minimum Inhibitory Concentration - Minimum amount of antibiotic/disinfectant needed to inhibit bacterial growth |
| How to determine MIC from dilution procedure |
| 1) The antibiotic/disinfectant is serially diluted 2) A standard amount of bacteria is added to each tube (i.e. 100ul) 3) Tubes are incubated overnight and then examined for lack of growth (no turbidity) the following day 4) To find the MIC, look for the greatest dilution with no turbidity |
| MBC stands for |
| Minimum Bactericidal Concentration - Minimum amount of antibiotic/disinfectant needed to kill or eliminate all bacteria |
| How to determine MBC from dilution procedure |
| To find the MBC, subculture non-turbid tubes from the MIC test, and find the greatest dilution with no growth on the plate |
| Name of the antibiotic sensitivity method |
| Kirby-Bauer Assay |
| Media used for Kirby-Bauer Assay (and standards) |
| Mueller-Hinton Agar (4mm thickness; pH 7.2-7.4) |
| Incubation time and temperature for Kirby-Bauer Assay |
37 °C 16-18 hours |
| McFarland standard and its purpose |
| 0.5 McFarland turbidity standard is ~1.5 x 108 cells per ML standard used to match the turbidity of bacterial saline culture for MIC/MBC testing |
| Zone of inhibition |
| Area devoid of growth around a disc The zone is measured in mm and compared to reference ranges (Know how to read a table of antibiotic sensitivity standards as well) |
| Purpose of hand washing |
| To not be gross Also, It's the most effective means of controlling spread of bacteria and nosocomial infections |
| Group of organisms eliminated by proper hand washing technique |
| Transient microbes - organisms picked up in our daily activities |
| Top 3 organisms responsible for nosocomial infections |
| E. coli S. aureus P. aeruginosa |
| Know the process of determining an unknown organism and the media that could be used. |
| You're on your own with this one. |
| Purpose of Rapid Strep Test |
| These tests can be performed in the clinic (or at home) for point-of-care diagnosis and treatment (Also known as lateral flow assays) |
| Organism Rapid Strep Test detects |
| Group A Streptococcus (specifically, Streptococcus pyogenes) |
| Purpose of using Enteropluri tubes and organisms detected |
| 18-24 hour identification of Enterobacteriacae and other Gram negative, oxidase negative bacteria from non-clinical specimens |
| How to inoculate, complete tests, and read results for Enteropluri tubes |
| Includes 12 distinct chambers Requires a pure culture of the organism to be tested The test contains a needle that is used to pick up a colony, then is pulled through to inoculate all tests The test is incubated at 37°C After incubation the results are recorded and a numeric code is assigned based on a score sheet The code is entered into a database to identify the unknown organism |
| Bacteriophage |
| A virus that infects bacteria. Usually specific "phages" infect specific stains or species of bacteria (ex. Coliphages infect E. coli) |
| Coliphage |
| A virus that infects E. coli |
| Plaque |
| Clear area on a bacterial lawn produced when phage infect and lyse bacterial cells |
| How to determine page specificity to a bacterial culture |
| Streak each organism onto a TSA plate utilizing the method used for the UV experiment Apply 10?L of phage to each quadrant Plates will be incubated @ 37°C Examine results for phage specificity |
| Two major reasons scientists classify viruses as non-living |
| Viruses are not cellular and they have no metabolism |
| Purpose of DNA extraction |
| To obtain DNA in a relatively purified form, so it can then be used for further investigations (e.g. PCR, sequencing, electrophoresis, etc.) |
| Materials required to perform DNA extraction |
| Detergent (for lysing) Table salt (for dissolving proteins) Ice-cold ethanol (for precipitating DNA) Stick (for spooling DNA for collection) |
| Know the steps and purpose of each step in the DNA extraction procedure |
| 1) Add 10 ml DNA Extraction Buffer (soapy salty water) to squished strawberries and squish for a few more minutes. (Cell lysing and removal of protein contamination) 2) Filter through a moistened paper towel set in a funnel, and collect the liquid in a clear tube. 3) Add 2 volumes ice cold ethanol alcohol to the strawberry liquid in the tube. Pour the ethanol alcohol carefully down the side of the tube so that it forms a separate layer on top of the strawberry liquid. (DNA precipitation) 4) Watch for a few seconds. You should see a white fluffy cloud at the interface between the two liquids. That’s DNA! 5) Spin and stir the coffee stirrer in the tangle of DNA, wrapping the DNA around the stirrer. |
| Purpose of Polymerase Chain Reaction (PCR) |
| Series of enzymatic reactions used to amplify (copy) small pieces of DNA |
| Basic materials needed to perform a PCR |
| Reaction components aka "master mix" include: Sterile water Appropriate buffer Salts (MgCl2) Nucelotides (dNTPs) Primers (designed for target region) Polymerase (Taq) TEMPLATE DNA |
| Produces Taq polymerase |
| The bacterium Thermus aquaticus |
| Piece of equipment used to perform a PCR reaction |
| Thermocycler |
| PCR Summary |
| Denaturing stage ~94°C - Separate template DNA Annealing stage ~54°C - Primers bind to target sequences Extension stage ~72°C - Complimentary DNA strand is synthesized using DNA polymerase and free dNTPs Repeat for 30-40 cycles Analyze PCR products using electrophoresis |
| Purpose of gel electrophoresis |
| Separate DNA pieces out by size |
| Basic materials needed for gel electrophoresis |
| Electric current Agarose or polyacrylamide gel Stains such as Ethidium Bromide or SyBr Gold (to visualize DNA in the gel) A base pair ladder (size ladder) to compare and identify correctly sized fragments |
| Aspects of the Gram-stain procedure |
| 1) Flood slide with crystal violet (primary stain) 2) Flood slide with Gram's iodine (mordant) 3) Decolorize with acetone a few seconds 4) Flood slide with Safranin (secondary stain) (*Rinse with water following each step*) |
| Catalase test |
| Used for Gram-positive organisms Identifies organisms that produce the enzyme catalase Differentiates families of Gram positive cocci -Catalase (+) Micrococcaceae from -Catalase (-) Streptococcaceae Substrate: hydrogen peroxide (+) test: bubbles form immediately (-) test: no bubbles |
| Oxidase test |
| Used for Gram-negative organisms |
| Protozoan life cycles |
Sometimes include trophozoite and/or cyst stages along with other forms. Cyst - dormant, survival stage. May be infective form and/or helpful in diagnosis. Trophozoite - Vegetative or actively growing form. |
| Vector |
| Organism that carries and transmits pathogen |
| Host |
| Organism that harbors pathogen May be required to complete a particular part of organism’s life cycle and/or spread the organism May show signs of disease |
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Balantidium coli Contracted via fecal-oral route Animal reservoir - pig Disease - Balantidiasis |
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Entamoeba histolytica Contracted via fecal-oral route Disease - amoebic dysentery |
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Giardia lamblia Contracted via fecal-oral route Disease - Giardiasis |
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Trichomonas vaginalis Contracted via sexual contact Disease - Trichomoniasis |
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| Trypanosoma spp. |
| Trypanosoma brucei |
| Disease: African Sleeping Sickness (African trypanosomiasis) Vector: Tsetse Fly Location: Africa |
| Trypanosoma cruzi |
| Disease: Chagas’Disease (American trypanosomiasis) Vector: Cone-nosed “Kissing” Bug Location: Central & South America |
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Plasmodium spp. Disease - Malaria Vector - Anopheles mosquito Location - Africa, Asia, and South America
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| Toxoplasma gondii |
Disease - Toxoplasmosis Host - Cat |
| Fungi general points |
| Cell wall usually composed of chitin Informally divided into unicellular yeasts and filamentous molds General purpose media high sugar, low pH (~5.6) (e.g. Sabouraud Dextrose Agar & Potato Dextrose Agar) |
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| Candida albicans |
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| Pneumocystis jirovecii |
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Rhizopus spp. Disease - Zygomycosis |
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| Penicillium spp. |
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Aspergillus spp. Disease - Aspergillosis |
| Nematodes |
| Round worms: roundworms with tapered ends |
| Trematodes |
| Flukes: flat, leaf-like bodies |
| Cestodes |
| Tapeworms: flatworms made of sections called proglottids with a scolex head |
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Enterobius vermicularis egg Nematode Human pinworm Fecal-oral transmission or inhalation of the eggs |
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Enterobius vermicularis adult Nematode Human pinworm Fecal-oral transmission or inhalation of the eggs |
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Trichinella spiralis Nematode Disease - Trichinosis Usually comes form pork or game animals |
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Ascaris lumbricoides egg Nematode Most common helminthic infection Female adult worms can reach length of 49 cm Disease - Ascariasis |
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Necator/Ancylostoma egg Nematode Hookworms Soil-transmitted 2nd most common helminthic infection Necator americanus - worldwide; most common human-specifc hookworm Ancylostoma duodenale - more geographically restricted
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Necator/Ancylostoma adult Nematode Hookworms Soil-transmitted 2nd most common helminthic infection Necator americanus - worldwide; most common human-specifc hookworm Ancylostoma duodenale - more geographically restricted |
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Necator/Ancylostoma head Nematode Hookworms Soil-transmitted 2nd most common helminthic infection Necator americanus - worldwide; most common human-specifc hookworm Ancylostoma duodenale - more geographically restricted |
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Fasciola hepatica Trematode Liver fluke Disease - Fascioliasis Host - herbivores, esp. sheep and cattle Humans exposed when infective metacercariae residing on fresh water plants are ingested |
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Clonorchis sinensis Trematode Chinese liver fluke/Oriental liver fluke Location - Asia Disease - Clonorchiasis Host - fish |
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Schistosoma spp. eggs (figure on left will be on the exam) Trematode Disease - Schistosomiasis Intermediate host - snail |
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Schistosoma spp. adults (figure on left will be on the exam) Trematode Disease - Schistosomiasis Intermediate host - snail |
| Schistosoma mansoni |
| Location: Brazil & Caribbean Adults reside in veins of the hepatic portal system |
| Schistosoma haematobium |
| Location: Africa & Middle East Adults reside in the veins associated with the urinary bladder |
| Schistosoma japonicum |
| Location: Southeast Asia Adults reside in the veins of the small intestines |
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Taenia solium egg Cestode Pork tapeworm Disease - Taeniasis Host - Pork |
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Taenia solium adult Cestode Pork tapeworm Disease - Taeniasis Host - Pork |
