Question | Answer |
Define titer | The highest dilution of a sample that tests positive for an antibody. |
Which immunoglobulin appears first when someone has an infection? | IgM |
Define Prozone. | During antibody precipitation tests, its the period of time when antibody concentrations are high and no precipitates are formed, leading to false negatives. |
How is a positive Western blot for HIV determined? | There will be two or more dark bands. |
what are the reagents in gram staining? | Crystal violet, Grams iodine, acetone-alcohol, safranin. |
In gram staining, what does crystal violet do? | stains all gram + and - bacteria. |
In gram staining, what does grams iodine do? | its a mordant that forms violet-iodine complex that binds more. |
In gram staining, what does acetone-alcohol do? | It decolorizes gram - bacteria. But only if not done for too long. |
In gram staining, what does safranin do? | counterstains gram - bacteria. |
What color are gram positive bacteria? | Purple |
What color are gram negative bacteria? | pink |
How do gram stains and wet mounts vary? | Gram can determine gram +/-. Wet mounts can tell motility. |
How are gram stains and wet mounts similar? | They both can see arrangement, size, and shape. |
What is the KOH test to differentiate gram positive from gram negative bacteria? | Mix KOH with a colony for 20 seconds. Stringy=negative. Not stringy=positive. |
Define ubiquity | Microorganisms everywhere. |
What are 3 spore forming bacteria that cause disease? | Bacillus Anthracis, Clostridium tetani, Clostridium botulinum. |
What bacteria causes anthrax? | Bacillus Anthracis |
WHat bacteria causes Lock jaw | Clostridium tetani |
What bacteria causes botulism | Clostridium botulinum |
Define alpha hemolysis and what does it look like? | Bacteria that can partiatlly break down heme pigment (green halo) |
Define beta hemolysis and what does it look like? | bacteria that can break down heme pigment fully. (clear zone) |
Define gamma hemolysis and what does it look like? | bacteria that show no change to a blood agar plate. |
Which hemolysis is a lab looking for in diagnosing strept throat? | beta hemolysis |
What is the importance of a capsule? | It protects against microphages in lungs. |
What stain shows a capsule? | gin stain. |
what is the name of the acid-fast stain and what is it used for? | Ziehl-Neelson procedure uses carbol fushsin. It detects bacteria with cell walls rich in lipids and waxes. LIke Mycobacterium and Nocardia. Leprosy, TB, |
Define selective media? | Isolates/cultivates for specific bacteria |
Define differential media? | Shows chemical reactions of bacteria |
Is MacConkeys selective or Differential? | Selective |
Is blood agar selective or differential? | Differential |
What is the catalase test for and what reagent does it use? | H2O2. Catalase breaks H2O2 into H2O and O2. Differentiates streptococci (cat-) from staphlococci (cat+) |
What is the coagulase test for? | Coagulase enzyme that breaks fibrinogen to fibrin. Staph aureus (coag+). Other staphs (coag-) |
How is carbohydrate differentiation determined? | Phenol red is used to determine a pH change. Red=no change, Yellow= pH drops and fermentation of carbohydrate has happened. CO2 gas may also be produced |
HOw does a positive hydrogen sulfide test appear? | Dark precipitate forms with Iron when hydrogen sulfide is present. |
How does a positive urease test appear? | Pos=bright pink. Neg=salmon->yellow |
How does positive citrate test appear? | Pos=blue. Neg=green |
Given a bacterial plate count from a urine culture be able to decide if there is a UTI. | (#colonies)x (_mL urine)= colonies/mL.
1K-10K = probable contaminated sample.
10K-100K=possible UTI.
>100K= UTI. |
Which 3 bacteria does the FDA recommend for disinfectant testing? | S.Aureus (gram +, infection of wounds), P.aeriginosa (gram -, often fatal), Solmonella typhi(gram -, hard to disinfect). |
Given results from antibiotic testing be able to determine resistance of susceptibility to antibiotics | Measure zone of inhibition and compare to reference chart to determine resistant, intermediate, or senstive(suceptable) |
Where does teh yeast cryptococcus cause serious infection? | Spinal fluid. |
Define dimorphic fungi. | They exist as yeasts and molds |
Define budding in yeast. | Yeast makes a small copy of itself that will grow into a new yeast cell. |
How would a gram stain be used with fungi | Fungi appear gram + but larger than bacteria |
HOw would a KOH stain be used with fungi? | KOH when mixed with tissue will digest tissue, but not fungus. A wet mount can be used to see hyphae. |
How would an india ink stain be used with fungi? | Cryptococcus which causes meningitis can have a clear capsule. |
What is the scotch tape test for? | Pinworm infections |
What is the disease or condition called cysticercosis and what parasite causes it? | When humans are intermediate hosts for the pork tapeworm. |
Infective stage and how diagnosed for giardia.. | ingest cysts. Stool sample for cysts or trophozoites |
Infective stage and how diagnosed for Hookworm (necator americanus) | Direct skin penetration. Stool for ova. |
Infective stage and how diagnosed for Ascaris. | Ingestion of ova. Stool for ova. |
Infective stage and how diagnosed for beef/pork tapeworm (Taenia saginata or Solium) | Ingest larva. Stool for ova and proglottids. |
Infective stage and how diagnosed for Trichomonas | Sexual transmission of trophozoite. Wet mount of genital secretions for trophozoite. |
What the insect vector for Trypanosoma brucei? | Tsetse fly |
What the insect vector for Trypanosoma cruzi | Reduviid bug |
What the insect vector for Leismania | Sandfly |
What the insect vector for Plasmodia? | Mosquito. |
What two roundworms or nematodes have a larval stage migrating through the host lungs? | Ascaris lumbricoides, Necator americanus. |
What two parasites use direct skin penetration as the way to enter the host? | Hookworms (necator americanus) and Blood fluke (Schistosoma). |
What stage of plasmodia in the mosquito is the infective stage for humans? | Sporozoite |
What stage of the plasmodia in the human host is the infective stage for mosquitoes? | Gamatocytes |
What stage in the plasmodia life cycle is occuring when the human host experiences fevers and chills? | Erythrocytic cycle when merozoites are released |
In which host does the asexual reproductive life cycle of plasmodia take place? | Human |
In which host does the sexual reproductive life cycle of plasmodia take place? | Mosquito |
Where in the human host does Toxoplamsa gondii infect? | CNS, heart and skel muscle. |
In what host does teh sexual reproductive cycle of toxoplasma gondii occur? | Cats |
What parasite causes african sleeping sickness? | Trypanosoma brucei |
What parasite causes changas disease? | Trypanosoma cruzi |
How would an individual get a Trichinella infection? | Ingestion of larva in skeletal muscle. |
What have molecular techniques to identify pathogens replaced some of the traditional methods? | They've become cheaper. They can identify bacteria that doesn't grow well on media. |
What is 16S rDNA and how is it used to identify bacteria? | A small subunit of ribosomal DNA. Species have unique 16S rDNA sequences. |
What is PCR? | It marks a region of DNA and replicates it. |
What are the 3 steps in PCR? | Separate the DNA strands, Annealing the primer to the template, synthesis of new DNA strands. |
What are primers? | Small pieces of DNA that bind to specific sequences. Signals DNA polymerase to copy the region. |
What is meant by conserved and variable regions of DNA? | Conserved=regions that are similar across species. Variable=regions are more species specific. |
How is cycle sequencing different from PCR? | In cycle sequencing, copies are made of target DNA but each copy terminates randomly with special nucleotides. |
What is BLAST? | A database for matching DNA sequences and ranks them based on level of similarity. |