Medical Microbiology test 1
An indirect smear from a blood agar plate was Gram stained and reported as "gram-positive cocci in clus-ters." However, the Gram stain of the thioglycollate broth demonstrated gram-positive cocci in chains. How would the microbiologist resolve this discrep-ancy, and what should be reported?
The smears prepared from each media are the same organism. When preparing a smear from solid media, it is important to make the smear is thin enough and to look to the outer edges to find the true morphologic characteristics and arrangement; all organisms tend to clump together when improperly emulsified. The broth culture allows the microbiologist to view organisms in their native states, including correct cellular morphologic characteristics and arrangement; they are not clumped together but are free floating in the liquid medium.
How is contrast achieved in light microscopy?
Use of special dyes and stains.
Bacterial cells genetically evolve by: a . Recombination with plasmids, transposons, and other bacterial chromosomes b . Mutation and recombination c . Use of the mechanisms of transduction, transformation, and conjugation d . All of the above
d . All of the above
In liquid hybridization, what methods are used to elimi-nate background noise? a . Enzymatic destruction b . Hydroxyapatite or charged magnetic microparticles c . Chemical destruction d . All of the above
d . All of the above
Stringency in a hybridization assay is affected by what factor(s)? a . Salt concentration b . Temperature c . Concentration of destabilizing agents d . All of the above
d . All of the above
What substance added to the antigen in the RPR test al-lows for more macroscopically visible flocculation? a . Latex particles b . Extracellular antigens c . Heparin-magnesium chloride particles d . Charcoal particles
d . Charcoal particles
Which type of enrichment media is used to isolate Neisseria and Haemophilus organisms? a. Hektoen enteric (HE) agar b . Todd-Hewitt broth c . Regan Lowe agar d . Chocolate agar
d . Chocolate agar
An example of a precipitation test able to detect antigen in a soluble solution is: a . Particle agglutination test b . Coagglutination test c . Liposome-enhanced latex agglutination test d . None of the above
d . None of the above
Dark-fi eld microscopy is used for the microscopic ex-amination of these types of bacteria: a. Gram-positive cocci such as Staphylococcus aureus b . Yeast such as Candida tropicalis c . Gram-negative bacilli such as Escherichia coli d . Spirochetes such as Treponema pallidum
d . Spirochetes such as Treponema pallidum
The following are all bacterial phenotypic characteristics except: a. Microscopic morphology and staining characteristics b . Environmental requirements for growth c . Nutritional requirements and metabolic capabilities d . The presence of a particular nucleic acid sequence
d . The presence of a particular nucleic acid sequence
Microorganisms that live in or on the human body without causing damage include: a . Colonizers b . Normal flora c . Microbiota d . Human microbiome e . All of the above
e . All of the above
The reasons immunochemical tests are important in diagnostic testing are: a . The inability to grow organisms on artificial media b . Th e failure of organisms to survive transport to the laboratory c . Th e fastidious nature of organisms and the long incu-bation time for growth in culture d . Antibiotic therapy started before specimen collection e . All of the above
e . All of the above
Calculate the total viewing magnification of an ob-ject when using the 40 objective lens.
10X of ocular lens times 40Xobjective = 400X magnification.
Most clinically relevant bacteria can be divided into four groups based on their Gram stain appear-ance; what are these four groups? What does the term pleomorphic mean?
(1) Gram-positive cocci, (2) gram-negative cocci, (3) gram-positive bacilli, (4) gram-negative bacilli. The term pleomorphic means exhibiting various shapes, gram-negative coccobacilli, or gram-variable bacilli.
Which of the following is not a correct use of the bino-mial nomenclature system? (Select all that apply.) a. Staphylococcus Aureus (ALL ITALICIZED) b . S. aureus (ALL ITALICIZED) c . Staphylococcus aureus (NONE ITALICIZED) d . Staphylococcus aureus (ALL ITALICIZED)
A
What is a biphasic medium, and how is it used?
A bacterial culture growth media consisting of both a solid (agar) and liquid (broth) phase; often used in blood cultures.
Provide an explanation for why bacteria are capable of rapidly responding to changes in their environment based on molecular and cellular structure. Bacteria are prokaryotes; the genetic material is not contained within a nucleus, allowing replication transcription and translation to occur simultaneously.
Bacteria are prokaryotes; the genetic material is not contained within a nucleus, allowing replication, transcription, and translation to occur simultaneously.
What two methods of microscopy are most widely used in clinical laboratories?
Bright field (light) and fluorescent microscopy.
What is an example of bacterial pathogens that are classifi ed as obligate intracellular parasites, requir-ing viable host cells for propagation?
Chlamydiae and Rickettsia organisms.
Bacterial endotoxins are: a. All the same b . Part of the gram-negative cell wall c . Capable of causing a systemic shock response D. ALL OF THE ABOVE
D. ALL OF THE ABOVE
What is the main purpose for using a culture medium that will meet the bacterial cell growth requirements?
Ensuring that the cell will multiply to sufficient numbers to allow visualization by the unaided eye to aid in the identification of the bacteria.
True or False _____ The ocular lens is the lens closest to the specimen. _____ Resolution is the extent at which detail in a mag-nified image is defined. _____ Fungi stain gram-negative. _____ Acid-fast bacteria are resistant to decolorization. _____ A fluorescent dye coupled with specific antibodies is called fluorochroming.
F T F T F
True or False _____ All bacteria are considered competent. _____ Conjugation requires cell-to-cell contact. _____ Oxidative phosphorylation occurs across the cell membrane in bacteria.
F T T
For what reason would the Gram stain of a specimen stain gram-variable, and how should that Gram stain be reported?
Gram-positive organisms that have lost cell wall integrity as a result of antibiotic treatment, old age, or other reasons will decolorize; report as gram-positive.
The process consisting of a series of methods designed to provide the microbiologist with relevant and useful clinical information about a microorganism is a. Classification b . Identification c . Organization d . Taxonomy
Identification
Compare and contrast the components of the specifi c and nonspecifi c immune defenses, including the occurrence and process of infl ammation; phago-cytic cells; antibody production; cellular response; and natural physical or chemical properties of the human body.
Inflammation occurs in both the nonspecific and specific immune response. However, inflammation begins as an activated process in the nonspecific. Any break in a tissue provides for the release of chemicals that attract immune cells. PMNs are 80% of the white blood cells in the circulation and respond to the signals. This results in an activation cascade of multiple immune factors. This increases blood flow to the site. The result is warm, red and swelling due to the influx of white cells and fluid.
What is the first and most important step for bac-terial identification and characterization?
Less water is available for essential bacterial metabolic pathways; and (2) an increase in the solute concentration of the media as a result of the loss of water can osmotically shock the bacterial cell and cause lysis
__________ is inhibitory or lethal for strictly anaerobic bacteria.
Oxygen.
Label each of the following characteristics as either a phenotypic (P) or a genotypic (G) characteristic. _____ Color of growth on artificial media _____ The presence of an antibiotic-resistance DNA sequence _____ The shape of the bacterial cell _____ The arrangement of the bacterial cells on a microscope slide _____ The ability of the organism to ferment lactose
P G P P P
What is the first and most important step for bac-terial identification and characterization?
Selection of a pure colony derived from a single bacterial cell.
_____ Selective media contain one or more agents that are inhibitory to most organisms except those be-ing sought. _____ Thayer-Martin media support exclusive growth of the two pathogenic organisms, Neisseria men-ingitidis and Haemophilus infl uenza. _____ Most clinically signifi cant gram-negative bacteria are susceptible to the antibiotic vancomycin. _____ Any zone of bacterial growth inhibition around a vancomycin-impregnated disk indicates that the bacteria are resistant to the drug.
T F F F
A short-lived infection that manifests with a short incu-bation period and serious illness is considered to be: a. Persistent b . Chronic c . Latent d . Acute
d . Acute
Which chemical or physical property is essential for the conservation of genetic information? a . Complementation between base pairs b . Double-stranded c . Antiparallel structure d . All are equally important
b . Double-stranded
Immunochemical tests are based on what molecular in-teraction? a . Antibody/antigen reaction b . Epitope/antigen reaction c . Myeloma cell/B-cell reaction d . Monoclonal/polyclonal antibody reaction
a . Antibody/antigen reaction
Transcription is the: a . Copying of DNA to RNA b . Changing of DNA to RNA c . Production of a complementary DNA d . Completion of a protein sequence
a . Copying of DNA to RNA
All of the following are involved in humoral immunity except : a . Cytotoxic T cells b . Complement proteins c . Plasma cells d . Glycoproteins
a . Cytotoxic T cells
A widely used hemagglutination test for detecting anti-body to T. pallidum is: a . MHA-TP test b . FTA-ABS test c . VDRL test d . Hemagglutination inhibition assay
a . MHA-TP test
In the FA test, the antigen is labeled with a compound that fluoresces. What determines the presence of anti-body? a . Measurement of fluorescence is a direct measurement of antigen-antibody binding and the presence of anti-body. b . Th e lack of fluorescence is a measurement of the anti-gen-antibody binding and the presence of antibody. c . Neutralization of the antigen by the antibody indi-cates that antibody is present. d . Neutralization of the antigen so that no cytopathic effect (CPE) is seen indicates the presence of anti-body.
a . Measurement of fluorescence is a direct measurement of antigen-antibody binding and the presence of anti-body.
In filter hybridization, the membrane is made of what material? a . Nitrocellulose or nylon fiber b . Agarose c . Ethidium bromide d . FITC
a . Nitrocellulose or nylon fiber
Which of the following is considered an indirect mode of transmission? a. A cut with a dirty knife b . Ingesting contaminated potato salad c . Inhaling a droplet containing a bacterium d . Drinking water from a contaminated source
a. A cut with a dirty knife
BCYE is an example of which type of media a. Enrichment media b . Supportive media c . Combination of selective and enrichment media d . Differential media
a. Enrichment media
A fluorescent dye coupled with specific antibodies is called: a. Immunofluorescence b . Fluorochroming c . Acridine orange d . Electron microscopy
a. Immunofluorescence
XLD (xylose-lysine-deoxycholate) agar: a. Inhibits many gram-negative bacilli that are not enteric pathogens b . Inhibits gram-positive organisms c . Contains a phenol red indicator that detects increased acidity from carbohydrate d . Causes fermentation e . All of the above
a. Inhibits many gram-negative bacilli that are not enteric pathogens
In amplification PCR-based testing, each cycle in the re-action does what to the amount of nucleic acid? a . Decreases it b . Doubles it c . Triples it d . Quadruples it
b . Doubles it
Humoral immunity: a. Is activated for all infectious agents b . Is specific for any organism c . Is specifically targeted to an antigen d . Provides a broad immune response to any microor-ganism
c . Is specifically targeted to an antigen
What CO 2 concentration is achieved when using a candle jar? a. 1 % b . 3 % c . 6 % d . 9 %
b . 3 %
Prokaryotic chromosomes: a . Are double-stranded RNA molecules b . Are single-copy, double-stranded DNA molecules c . Are linear double-stranded DNA molecules d . Are unable to replicate independently of plasmids
b . Are single-copy, double-stranded DNA molecules
The complete clearing of media around bacterial colonies on a blood agar plate is referred to as: a. Alpha-hemolysis b . Beta-hemolysis c . Gamma-hemolysis d . Delta-hemolysis
b . Beta-hemolysis
The periplasmic space is required for: a . Nutrient collection in both gram-positive and gram-negative bacteria b . Collection and enzymatic degradation of nutrients in gram-negative bacteria c . Nutrient detoxification and enzymatic degradation in all bacteria d . None of the above
b . Collection and enzymatic degradation of nutrients in gram-negative bacteria
The step in the Gram stain process that distinguishes be-tween gram-positive and gram-negative organisms is: a. Fixing of the cells to the slide using heat or methanol b . Decolorization using alcohol or acetone c . Counterstain of the Gram stain using safranin d . Application of the mordant, Gram's iodine
b . Decolorization using alcohol or acetone
A clinical isolate was plated to sheep blood, MacConk-ey, and chocolate agars and incubated at 37°C for 24 hours. The initial plate reading identifi ed medium sized, gamma-hemolytic, shiny gray colonies on sheep blood agar; small pink colonies on MacConkey agar; and me-dium sized, tan, shiny colonies on chocolate agar. Th e most likely next action for the microbiologist is: a. Identify the two diff erent organisms that are grow-ing on the plates as indicated by the size diff erences on the agar. b . Identify the single likely gram-negative lactose fermenter as evident by the combined colonial morphology. c . Report as normal microbiota without a further bio-chemical identifi cation. d . Reinoculate the isolate from the blood and the MacConkey agar plates to two more sets of primary media to provide a better preliminary identifi cation of the isolate.
b . Identify the single likely gram-negative lactose fermenter as evident by the combined colonial morphology.
A sign is different from a symptom in all of the following ways except: a. It provides measurable data. b . It is believed to be associated with the etiology of the disease. c . It is clearly visible. d . It includes the temperature, respiratory rate, and pulse.
b . It is believed to be associated with the etiology of the disease.
Classification and naming of organisms is useful in diag-nostic microbiology for all of the following except: a. Providing standardized groupings for identification b . Standardized groupings are always genotypically similar at .98% c . Standardized groupings share similar phenotypic traits d . The ability of organisms within a standard group may be identified using similar methods
b . Standardized groupings are always genotypically similar at .98%
Electron microscopy allows for what magnifi cation of an organism? a. 1000x b . 10,000x c . 100,000,000x d . 1,000,000x
c . 100,000,000x
What is the number of bacteria needed to cause turbidity in broth culture and to be seen with an unaided eye? a. 102 organisms b . 104 organisms c . 106 organisms d . 108 organisms
c . 106 organisms
What temperature is typically used to achieve DNA de-naturation from a double-stranded molecule to a single-stranded pair of molecules? a . 74°C b . 92°C c . 94°C d . 102°C
c . 94°C
An infection acquired from working with an animal reservoir is: a. Acquired from a vehicle b . Transmitted by a vector c . A zoonotic infection d . An example of indirect transmission
c . A zoonotic infection
Nonspecific immunity includes all of the following except: a. Inflammation b . Phagocytosis by neutrophils c . B-cell activation to produce antibodies d . Resident normal microbiota
c . B-cell activation to produce antibodies
CNA media with blood is an example of which type(s) of media? a. Enrichment only b . Supportive only c . Combination of supportive and differential d . Combination of selective and supportive
c . Combination of supportive and differential
A eukaryotic cell: a . Is smaller and less complex than a prokaryotic cell b . Is able to grow only in aerobic conditions c . Contains membrane-bound organelles d . Is unable to grow outside of another cell
c . Contains membrane-bound organelles
Biofilm formation within a host results in: a . Easy clearance of bacterial pathogens b . Availability of organic nutrients to the host c . Inability of the immune system to remove the pathogen d . Starvation of the microorganisms
c . Inability of the immune system to remove the pathogen
What is the acceptable protocol for testing for Lyme dis-ease, as recommended by the CDC? a . Screen for the presence of antibody using the ELISA test; no further testing is required. b . Screen for the presence of antibody using the hemag-glutination test; confi rm positive results with the Western blot test. c . Screen for the presence of antibody using the ELISA test; confirm positive results with the Western blot test. d . Screen for the presence of antibody using only the Western blot test.
c . Screen for the presence of antibody using the ELISA test; confirm positive results with the Western blot test.
The laboratory scientist observed an opaque, beta-hemo-lytic colony on a sheep blood agar plate of a throat cul-ture from a patient. To identify the isolate, the technolo-gist retrieved the streptococci typing kit from the refrigerator. Th e technologist used the controls included in the kit and determined the isolate to be positive for group A beta-hemolytic streptococci. In reviewing this information: a . Th e technologist used the improper controls and should have used live organisms for the test. b . Th e technologist properly performed the test and identifi ed the organism. c . Th e technologist failed to bring the kit to room tem-perature, resulting in a false positive reaction. d . Th e technologist should have completed additional biochemical tests for the identifi cation of the or-ganism.
c . Th e technologist failed to bring the kit to room tem-perature, resulting in a false positive reaction.
Expression of a biochemical molecule in an organism requires: a . Replication only b . Transcription only c . Transcription and translation of a protein d . All of the above
c . Transcription and translation of a protein
The most specific and exclusive taxon used in the classification of microorganisms is: a. Family b . Order c . Species d . Genus
c.species DEAR KING PHILLIP CAME OVER FOR GOOD SOUP -domain -kingdom -phylum -class -order -family -genus -species
A microorganism that colonizes the skin but is capable of causing infection under the appropriate conditions is referred to as: a. A pathogenic organism b . An opportunistic pathogen c . Normal microbiota d . A nosocomial pathogen
d . A nosocomial pathogen
The stain that binds to the nucleic acid of organisms but does not discriminate between gram-positive or gram-negative organisms is called: a. Ziehl-Neelsen stain b . Auramine-rhodamine stain c . Gram stain d . Acridine orange stain
d . Acridine orange stain
