Lab Content Quize – Flashcards
Unlock all answers in this set
Unlock answersquestion
| The Gelatin Hydrolysis Test tests for what? |
answer
| Presence of gelatinases that hydrolyze proteins found found in host connective tissue. (Collagen and Gelatin) |
question
| The Gelatin Hydrolysis Test that consists of a liquid after culture of a bacterium indicates what? |
answer
| The presence of gelatinases in the bacterium. |
question
| What growth media is used for the Gelatin Hydrolysis Test? |
answer
| Nutrient Gelatin - beef extract, peptone and gelatin |
question
| Cultures of S. Aureus and E. Aeroginosa are incubated in a Nutrient Gelatin media. What will be the consistency of the test tube? |
answer
| Solid |
question
| Of S. aureus, S. epidermidis, S. marcescans and E. aerogenosa, which media will be liquid after incubation in Nutrient Gelatin growth media? |
answer
| S. aureus and S. marcescans |
question
| What type of bacteria produce hemolysins? |
answer
| Gram positive pathogenic bacteria |
question
| What are hemolysins? |
answer
| Exotoxins that damage RBCS |
question
| What media is used for the hemolysis test? |
answer
| Blood agar - Tryptic soy agar and 5% sheep blood |
question
| What are three examples of hemolytic bacteria? |
answer
| Staphylococcus, streptococcus and listeria |
question
| The partial destruction of RBC's and a greenish discoloration in the media indicates the presence of what? |
answer
| alpha-hemolysins |
question
| The complete destruction of RBC's and a clearing in the media indicates the presence of what? |
answer
| Beta-hemolysins |
question
| What are DNases? |
answer
| Produced by bacteria to degrade neutrophil DNA and break down NET's to escape phagocytosis |
question
| What does the DNA Hydrolysis Test test for? |
answer
| The presence of DNases |
question
| Clearing around bacterial colonies in a DNA Hydrolysis test indicates what? |
answer
| The presence of DNAses |
question
| A negative DNA Hydrolysis test will look like what? |
answer
| The blue-green dye media without clearing |
question
| What are the predominant causes of dental caries? |
answer
| Lactobacillus and streptococcus |
question
| What are dental caries? |
answer
| Fermentation of dietary sugars by microbes that lead to acid production that wear away tooth enamel and promote decay |
question
| What does the Snyder test test for? |
answer
| A persons' susceptibility to forming dental caries as a result of the presence of lactobacilli or streptococci |
question
| How does the Snyder test select for lactobacilli? |
answer
| The pH is reduced to 4.8 - the bacteria are acid-tolerant |
question
| A media that changes green to yellow in the Snyder test indicates what? |
answer
| The presence of lactobacilli or streptococci. |
question
| A change in color after 24 hours indicates what in the snyder test? |
answer
| A high susceptibility to dental caries |
question
| A change in color after 48 to 72 hours indicates what in the snyder test? |
answer
| Moderate to slight susceptibility to dental caries |
question
| What does the Kirby-Bauer test test for? |
answer
| A microbes susceptibility to an antibiotic. |
question
| Which media is used for the Kirby-Bauer test? |
answer
| The Mueller-Hinton (MH) agar - pH 7.2-7.4 - beef extract, milk protein, starch. |
question
| Why is MH used in the Kirby-Bauer test? |
answer
| Has low variation, allows growth of a variety of organisms. |
question
| What variables can affect the zone of inhibition in the kirby-bauer test? |
answer
| Number of bacterial cells, thickness of the agar and the growth phase of the microorganism. |
question
| What phase of growth must the microbe be in during the kirby-bauer test? Why? |
answer
| Logarithmic - because this is when they are the most susceptible to antimicrobial agents. |
question
| p. aeroginosa is a __________ __________ and is resistant to all antibiotics tested except for ______________ |
answer
| Gram - Rod, Streptomycin |
question
| B. cereus is a ____________ ____________ and is resistant to only ___________ and _____________. |
answer
| Gram + Rod, penicillin and trimethoprim |
question
| S. aureus is a ________________ _____________ and is resistant to only ______________. |
answer
| Gram + rod, chloremphenicol |
question
| Where does S. aureus live? |
answer
| In the nares of humans |
question
| MRSA is resistant to many __________ antibiotics? |
answer
| beta-lactam |
question
| What does the femB gene encode for? |
answer
| The S. aureus-specific enzyme |
question
| If MRSA is present in a gel electrophoresis, what will be observed? |
answer
| A mark at the femB gene, and mark at the mecA gene and a mark at the 16s rRNA gene |
question
| How does a PEA plate inhibit gram negatives? |
answer
| Phenylethyl alcohol breaks down the outer membrane and cytoplasmic membrane of gram negatives. |
question
| On an MSA plate if the colonies are clear and the background is pink -red. |
answer
| Microbes don't ferment mannitol |
question
| On an MSA plate if the colonies are clear and the medium turns from red to yellow. |
answer
| Microbe ferments mannitol |
question
| If a microbe doesn't grow on a PEA plate it is.... |
answer
| Gram Negative |
question
| What is the selective agent in MacConkey Agar? |
answer
| Crystal violet and bile salts that inhibit growth of gram pos microorganisms |
question
| What are the differential agents in macConkey Agar? |
answer
| lactose and PH natural red |
question
| On macConkey agar the colonies are mauve on a mauve medium |
answer
| Gram negative that doesn't ferment lactose |
question
| If a microbe doesn't grow on MacConkey Agar it is.... |
answer
| gram positive |
question
| On macConkey agar, the media color is yellow.. |
answer
| Ferments lactose |
question
| What is the selective agent in HEA? |
answer
| Bile salts- prevent gram + |
question
| What are the differential agents in HEA? |
answer
| carbs and bromophenol blue and ferric ammonium citrate and sodium thiosulfate |
question
| If the media is yellow on HEA agar? |
answer
| enteric microbe that ferments carbs |
question
| If the colonies are black on HEA agar? |
answer
| salmonella!! - produces ferrous sulfide |
question
| If a microbe doesn't grow on HE... |
answer
| Gram pos |
question
| If both OF tubes are yellow.. |
answer
| The microbe is a facultative aerobe |
question
| If an OF tube turns blue |
answer
| The microbe may use protein as a fermentation source |
question
| An MR test is yellow |
answer
| negative for mixed acid fermentation |
question
| A MR test is red. |
answer
| Positive for mixed acid fermentation - enteric |
question
| A VP tube has a little violet at the top |
answer
| Positive for butanediol pathway. |
question
| A microbe that hydrolyzes starch will look like what? |
answer
| zone of clearing around growth- where microbe has eaten at starch |
question
| Which antibiotics target protein synthesis? |
answer
| chloramphenicol and tetracycline |
question
| Which antibiotics prevents bacteria from synthesizing folic acid? |
answer
| trimethoprim |
