lab exam
Please choose all correct responses. Which of the following statements are true regarding Antiseptics and Disinfectants?
Antiseptics are used on living tissues to remove potential pathogens Disinfectants are used on non-living surfaces to remove potential pathogens
A 37 year old male was admitted to the hospital with chest and back pain. On examination, his chest was dull to percussion. A chest x-ray shows lower right lung infiltrates. A sputum culture is obtained and the following results are displayed on a blood agar plate. What tests will you set up next? Select all that apply.
Bile Esculin Salt Tolerance 6.5% NaCl Optochin Test
Based on this example class data, which bacterium was more resistant and which was less resistant and why? (Select all that apply)
B. megaterium were more resistant because they form endospores S. aureus were less resistant because they do not form endospores
Which bacterium was positive for starch hydrolysis?
B. subtilis
You recover the following results from a wound culture submitted to the laboratory. What tests will you inoculate?
Bacitracin Disc CAMP test SXT Susceptibility
Select all of the answers that are correct with regards to the picture above:
Bacteria A is positive for phenylalanine deaminase Bacteria B is negative for phenylalanine deaminase The end products of pheynylalanine deamination test are phenylpyruvic acid and ammonia
A patient complains of a sore throat and difficulty swallowing. On examination, her throat is red and contains white patches near and around the tonsils. You suspect streptococcal pharyngitis. What type of hemolysis would you expect to see on a blood agar plate?
Beta hemolysis
If a bacterial isolate shows intermediate to moderate resistance (i.e. Dose Dependent) to an antibiotic or antimicrobial, how might this drug still be successfully used in the treatment of this microbe?
The drug may be used in combination with other drugs to treat the infection The drug can possibly be used at a higher dose (if selective toxicity is still possible) to treat the infection
All tube caps for all inoculated tests should be kept loose so the bacteria can get oxygen during incubation.
False
Alpha-toxin is a protein that causes the reduction of the red blood cell hemoglobin to methemoglobin producing alpha hemolysis of blood agar.
False
An antiseptic or disinfectant chemical or process will work on all bacteria or Fungi regardless of species or structural adaptations.
False
For the Gelatin Hydrolysis Test, results can and should be read when bacteria have been taken straight from the 37C incubator.
False
If a bacterium breaks down DNA, the end products- nucleotides and phosphate, react with the hydrochloric acid reagent causing a cloudiness around the bacteria.
False
If bacteria are able to utilize citrate as a sole carbon source they will produce ammonia as a by-product, turning the citrate agar green.
False
If penicillin produces a larger zone of inhibition than tetracycline on the Kirby-Bauer disk diffusion test, penicillin should always be prescribed.
False
If the needle was moved sideways in the motility media during inoculation it may result in a false negative.
False
In the specific carbohydrate fermentation test, if a bacterium is positive for fermentation of the sugar, then it has to have both acid and gas.
False
It doesn't matter how many microorganisms are present on a surface, it will still take the same amount of time to disinfect or decontaminate the surface whether there is only a few or there is abundant amounts of microbes present.
False
Just as in the Quadrant Streak Plate method, the Lawn Streak Plate method also has the user apply bacteria in a concertation gradient fashion on the agar plate. That means that not every part of the plate will receive the same theoretical concentration of bacteria.
False
The indole test is used to determine if a bacterium breaks down indole.
False
A Glucose Fermentation test is performed and the following results were obtained. Correctly interpret the results.
Fermenter with acid and gas production
The following results are obtained on a blood agar plate. What is your interpretation of hemolysis?
Gamma hemolysis
If a bacterium produced during fermentation, then the durham tube in the specific carbohydrate fermentation test will have a bubble in it. Also, the Kligler iron agar slant may show bubbles and cracks in the agar, or the agar may even be pushed up towards the top of the tube.
Gas
Interpret the small bacterial colonies present in the zone of inhibition below.
There are colonies that are resistant to this antibiotic
What is a ultraviolet germicidal irradiation?
This is a method of disinfecting that uses short-wave UV light to kill bacteria by disrupting their DNA
Which of the following accurately describes a Thymine-Thymine dimer?
Thymine binding to another Thymine on the same DNA strand
Based on your interpretation of the the above Blood agar plate, you will inoculate the following tests. Check all that apply.
Salt Tolerance in 6.5 NaCl Bile Esculin Optochin Disc
Both the Methyl Red and the Voges-Proskauer tests are performed from one inoculated MRVP broth. However, to perform both tests, one will need to remove and place broth into new test tubes to perform each test separately as they require different reagents to perform each test.
True
Endospore producers such as Bacillus and Clostridium species and acid-fast bacteria like Mycobacterium tuberculosis are harder to eliminate with the use of antiseptics and disinfectants.
True
Generally speaking, the shorter the wavelength the more harmful the radiation
True
If a bacterium breaks down urea, then the end products (ammonia and carbon dioxide) create an alkaline pH that turns the phenol red pH indicator a fuchsia pink color.
True
If a bacterium is able to utilize glucose oxidatively the tube without mineral oil will turn yellow, either fully or partially.
True
Only one of the inoculated O/F Glucose tubes will be overlaid with mineral oil. Correct!
True
Several species of bacteria, including Staphylococci and Streptococci, are normal inhabitants of the pharynx
True
Some bacteria produce the exoenzyme amylase to break down starch into its glucose building blocks.
True
Some tests will be incubated for only 24 hours, others for 24 to 48 hours, while others will remain in the incubator for 5 to 7 days.
True
Staphylokinase is a enzyme that dissolves blood clots
True
The O/F tube with mineral oil on it is the tube used to demonstrate fermentation by creating an anaerobic environment in the tube.
True
The majority of bacteria do not produce a pigment.
True
The motility deep tube should be inoculated with a heavy inoculum.
True
The phenylalanine deamination test is used to determine if the bacterium can break down the amino acid phenylalanine.
True
The plates that had the lids left on showed that UV light cannot penetrate through the clear plastic of the petri plate lid.
True
There are three possible results for the O/F Glucose test
True
There are two rapid tests in this lab exercise. "Rapid tests" mean these will give us test results immediately with no need for incubation.
True
There are very specific procedures that should be followed in order to inoculate each test correctly.
True
UVA radiation penetrates deeper into human skin when compared to UVB
True
The media used for the Indole test is called?
Tryptophan
Which type of Ultraviolet Light (Radiation) is the most harmful to microorganisms and is used to disinfect food, air, water and surfaces?
UVC
Which type of electromagnetic radiation listed has the shortest wave length?
Ultraviolet
Please choose all correct responses. Which of the following factors are considered by the CLSI when evaluating a novel antibiotic/antimicrobial drug therapeutic?
Uniform inoculating protocols Concentration of plated bacteria Agar type and nutrient supplement
The substrate in this test is ____ . The enzyme is ______
Urea; urease
The standard method required by the EPA for testing disinfectants chemicals is called the __________ method.
Use-Dilution
Motility can be evaluated by two methods: Motility media and .
Wet mount
Streptococci are similar to Staphylococci in that they are both facultative anaerobes, and both produce the enzyme catalase.
false
If gelatin tubes are evaluated prior to the tubes being chilled in the refrigerator a _____ ______ may result.
false positive
Matching phenylalanine deaminase to its reagent
ferric chloride
A positive result means that bacterium is capable of break down ___ and producing ______?
glucose and methyl red
What is Staphylococcus aureus?
gram positive, non spore former
Some bacteria produce [ Select ] which are exoenzymes that lyse [ Select ] and degrade hemoglobin.
hemolysins; red blood cells
The dark color on the plate results when ______ is added to the plate and combines with ______ that is in the agar.
iodine; starch
Matching Starch hydrolysis to its reagent
lugol's iodine
What unit of measurement is used when measuring the zone of inhibition for antibiotic sensitivity testing?
millimeters
E. coli is ______ and P. vulgaris is _____ ? positive or negative
negative; postive
Choose all of the characteristics that correctly describe the bacterial growth on the slant.
opaque yellow pigment filiform
In the O/F test, the "O" and "F" stand for:
oxidative and fermentative
What is alpha hemolysis?
partial hemolysis, greenish/brownish around colonies
The pH indicator in the Mannitol Salt Agar plate test is
phenol red
Is tube A positive or negative?
positive
What is a obligate aerobe?
requires oxygen, grows at top at the tube
which of the following terms most accurately describes the sensitivity of the bacteria to the antibiotic in the red circle below?
sensitive
The larger the zone size, the more ____________ the bacterium is to that antibiotic.
sensitive or susceptible
What is a germicidal UV?
short range UV (UVC), is mutagenic to bacteria, viruses, and other microbes
Which of the following are uses for UV light? (Select all that apply)
sterilize equipment air sanitization sterilize drinking water and wastewater sterilize work areas
How are the DNA, starch, and skim milk plates being inoculated?
straight line plate method
In the disc-diffusion assay, a large zone of inhibition around a disk to which a chemical antiseptic/disinfectant has been applied indicates ______________ of the test microbe to the chemical antiseptic/disinfectant.
susceptibility
Interpret the following Coagulase Test result
top positive bottom negative
In the presence of acid the pH indicator turns?
yellow
Streptococci are gram-positive spherical bacteria that divide on more than one plane to form irregular clusters of cells.
False
The TSA plate will be inoculated using the Quadrant Streak Plate Method, while the blood agar plate will be inoculated with a Lawn Streak Plate Method.
False
A durham tube is used in the carbohydrate fermentation broth to show if a bacterium produces gas byproducts as part of fermentation.
True
A positive indole test is indicated by a cherry red ring after addition of the Kovac's reagent.
True
What is bacillus megaterium?
gram positive, spore former
Which tube shows a positive result for the butanediol pathway?
B
match the tube to the description of the predominant growth pattern seen in the tube: A, B, or C pellicle?
B
Any visible zone of inhibition surrounding Novobiocin is considered sensitive
False
Blood agar is used to separate the Streptococci into two groups based on the ability to cause lysing of red blood cells when grown on blood agar.
False
Facultative anaerobes grow better without oxygen.
False
What is gamma hemolysis?
no hemolysis
Refer to the picture of the Starch hydrolysis plate above. Which bacterium is positive for production of amylase?
A
Which tube contains alkaline end products, such as putrescine and cadaverine?
A
match the tube to the description of the predominant growth pattern seen in the tube: A, B, or C turbid?
A
What is a thymine dimer?
A molecule consisting of two linked thymine subunits that are formed in DNA by a covalent linkage, in response to ultraviolet radiation
What is Hemolysins?
A substance that destroys red blood cells
Which tube above contains a bacterium that possesses the enzyme tryptophanase?
B
Which of the following can effectively destroy Covid-19 on hands or surfaces?
Alcohol hand sanitizers Bleach based cleaners Hydrogen peroxide or hydrogen peroxide based cleaners Quaternary ammonia compounds (Quats)
Which of the following can be an active agent in an antiseptic?
All of above
Choose all of the tubes that show pigment production.
All of the above except A
What is a sanitizer?
An agent that reduces, but may not eliminate, microbial numbers to a safe level
What is Coagulase?
An enzyme that converts fibrinogen to fibrin causing plasma to clot
What is Nosocomial?
An infection that is acquired in the hospital or other healthcare facility
Which of the following statements most accurately describes the microbiology term opportunistic?
An organism that is not normally pathogenic, but can become pathogenic under certain conditions
match the tube to the description of the predominant growth pattern seen in the tube: A, B, or C sediment?
C
A urine culture is sent to the lab and a Gram positive cocci is grown. You are unsure if the Gram positive cocci is a staphylococci or a streptococci. There is no hemolysis on the plate. Which one of the following two tests will you perform next?
Catalase
Which sugar will not be tested in the specific carbohydrate fermentation test?
Cellulose
When reading the Casein hydrolysis test which of the following is true:
Clearing around the bacteria is a positive result
When reading the Casein hydrolysis test, which of the following is true?
Clearing around the bacteria is a positive result
Is Blood Agar considered selective or differential?
Differential
Which tube shows the following results- positive for glucose fermentation, negative for lactose fermentation and positive for hydrogen sulfide production?
E
Why was half of the plate covered with an index card? (Select all that apply)
Half of the plate was covered to provide an area of comparison to see the amount of bacteria growth when not exposed to UV light and the effects of UV light on the growth Half of the plate was covered to serve as a control to show that the bacteria were viable before exposure to UV light
What must be added to the DNA agar plate in order to determine if the bacterium broke down the DNA?
Hydrochloric Acid (HCL)
Which description below most accurately describes an obligate aerobe?
Requires oxygen, cannot grow without oxygen.
which of the following terms most accurately describes the sensitivity of the bacteria to the antibiotic in the red circle below?
Intermediate
What must be added to the starch agar plate in order to determine if the bacterium broke down the starch?
Iodine
Matching indole test to its reagent
Kovac's reagent
Which type of bacterial plating method will be used in this lab exercise?
Lawn streak plate method
The red/pink colored substance at the top of the test tubes is ?
Resazurin
What is MRSA?
Methicillin resistant Staphylococcus aureus
The following results are obtained on the Bile Esculin tube. What is your interpretation?
Negative
The following result was obtained on the Nitrate Reduction test after the addition of zinc. What is the correct interpretation?
Negative for reduction of nitrate
Please interpret the following motility agar deep with TTC indicator.
Non-motile
Matching casein hydrolysis to its reagent
None
if you tested the bacterium Pseudomonas aeruginosa and observed a 13 mm zone of inhibition for tetracycline on your Kirby-Bauer plate, how would you rate Pseudomonas aeruginosa to tetracycline?
Resistant
which of the following terms most accurately describes the sensitivity of the bacteria to the antibiotic in the red circle below?
Resistant
A Fluid Thioglycollate Medium (FTM) Broth Tube will be inoculated in order to determine a bacterium's requirement.
Oxygen
What is Pyogenic?
Pus-forming
Staphylococci and Streptococci bacteria are referred to as or pus-forming Gram-positive cocci which cause boils, abscesses, carbuncles, and fatal septicemias.
Pyogenic
If a Staph test came back as positive (+) for Coagulase, which specific strain of Staph would you be able to choose as the infecting strain?
Staphylococcus aureus
In the presence of acid the pH indicator in the mannitol salt agar plate turns
Yellow
The end product that is detected in a positive O/F test is?
acidic end products
The end product that is detected in a positive citrate test is
alkaline end products
What is the mechanism by which disinfectant agents show their actions?
all of the above
What is a sterilant?
an agent that destroys all microbial life
What is a antiseptic?
an agent that kills or inhibits growth of pathogenic microbes and is suffiicently nontoxic to be applied to living tissues
What is a disinfectant?
an agent that kills or inhibits pathogenic microbes and is only used on inatimate objects
In the Kligler iron agar slant, if a bacterium is positive for hydrogen sulfide production, then the tube will be .
black with a black precipitate
Which specific biochemical test must be interpreted before I am able to conduct additional testing in the Streptococcus lab?
blood agar plate
In alkaline conditions the pH indicator turns?
blue
What is Mannitol Salt Agar?
both differential and selective
The pH indicator in both the oxidative/fermentative (O/F) test and the utilization of citrate test is ?
bromothymol blue
The Kligler Iron agar slant is inoculated using a double inoculating procedure; this entails performing a stab inoculation to the _____ of the tube, and a streak inoculation to the _____ of the tube.
butt; slant
what is a facultative anaerobe?
can live with or without oxygen; heavier on top of tube but will grow throughout
What is a obligate anaerobe?
cannot live in oxygen; grows at bottom of tube
What is a mutation?
changes to DNA that are not repaired and may lead to death of the organism
What is beta hemolysis?
complete hemolysis, clearing around colonies
We measure the ____________________ of the zone of inhibition in ________________.
diameter, millimeters
