Bailey And Scotts Diagnostic Microbiology 13th Edition By Patricia M. – Test Bank A+

Description

1. In microscopy, resolution can be defined as the:

a.	magnification power.
b.	extent to which detail in the magnified object is maintained.
c.	ability of objects to stand out from the background.
d.	ability to see objects against a black background.

ANS: B

The extent to which detail in the magnified object is maintained is called resolution.

REF: 69 OBJ: Level: Knowledge

1. Contrast in microscopy is most commonly achieved by:

a.	changing objectives for various specimens.
b.	increasing the resolution or resolving power.
c.	staining techniques.
d.	adding a blue filter to the light path.

ANS: C

Various staining techniques are used to increase contrast and make objects appear more visible.

REF: 70 OBJ: Level: Knowledge

1. The first step in the Gram-stain sequence is the application of _______, which is the primary stain.

a.	safranin
b.	crystal violet
c.	Gram’s iodine
d.	Gram’s decolorizer

ANS: B

Crystal violet is the primary stain used in the Gram-stain sequence.

REF: 71 OBJ: Level: Knowledge

1. A mordant that is applied after the primary stain to bond chemically the alkaline dye to the bacterial cell wall is:

a.	safranin.
b.	crystal violet.
c.	Gram’s iodine.
d.	Gram’s decolorizer.

ANS: C

Gram’s iodine serves to stabilize the crystal violet in the cell wall of gram-positive bacteria.

REF: 71 OBJ: Level: Knowledge

1. After which step in the Gram-stain procedure are gram-positive bacteria first distinguished from gram-negative bacteria?

a.	Crystal violet
b.	Iodine mordant
c.	Gram’s decolorizer
d.	Safranin

ANS: C

Up until the decolorizer step, all bacteria and cells appear the same during the Gram-stain procedure.

REF: 71 OBJ: Level: Application

1. The acid-fast stain is specifically designed for bacteria whose cell walls contain:

a.	teichoic acids.
b.	mycolic acids.
c.	peptidoglycan.
d.	disaccharide-pentapeptide subunits.

ANS: B

Mycolic acids render the bacterial cells resistant to decolorization and thus cause acid-fast organisms to maintain the primary stain in the acid-fast staining procedure.

REF: 73 OBJ: Level: Knowledge

1. In the Kinyoun acid-fast staining method, ______ replaces _____ in the primary stain solution.

a.	increased phenol; heat
b.	heat; increased phenol
c.	mycolic acid; heat
d.	carbolfuchsin; phenol

ANS: A

The Kinyoun method is one in which the heat step of the traditional acid-fast staining method is replaced by increased phenol.

REF: 76 OBJ: Level: Knowledge

1. Of the different types of staining and microscopic techniques, which one of the following is basically the most sensitive?

a.	Chromogenic
b.	Fluorescence
c.	Phase contrast
d.	Light field

ANS: B

Fluorescence makes the object appear bright against a dark background, making it easier to see on low magnifications.

REF: 76 OBJ: Level: Application

1. The fluorochrome stain that can be used to detect mycobacteria is:

a.	calcofluor white.
b.	acridine orange.
c.	auramine.
d.	immunofluorescence.

ANS: C

The mycolic acids in the cell walls of mycobacteria have an affinity for auramine and rhodamine.

REF: 78–79 OBJ: Level: Knowledge

1. The fluorochrome stain used to study a fungus is:

a.	calcofluor white.
b.	acridine orange.
c.	auramine.
d.	immunofluorescence.

ANS: A

The cell walls of a fungus will bind calcofluor white.

REF: 79 OBJ: Level: Knowledge

1. Which of the following statements is true concerning dark-field microscopy?

a.	This type of microscopy uses specific stains to enhance the contrast of certain bacteria.
b.	The condenser does not allow light to pass directly through the specimen but directs the light to hit the specimen at an oblique angle.
c.	Dark-field microscopy allows the visualization of larger viruses.
d.	Dark-field microscopy can differentiate various difficult-to-grow organisms by using immunofluorescence.

ANS: B

Dark-field microscopy does not allow light to pass directly through the specimen but directs light to hit at an oblique angle thus making the background a dark field.

REF: 79 OBJ: Level: Knowledge

1. Magnifications in excess of 100,000 ´ are achieved by ________ microscopy?

a.	bright-field
b.	electron
c.	dark-field
d.	phase-contrast

ANS: B

Electron microscopy uses magnifications in excess of 100,000 times.

REF: 80 OBJ: Level: Knowledge

1. Bacterial cells with thick peptidoglycan and numerous teichoic acid cross-linkages are Gram stained. The organisms stain pink. Which one of the following statements explains this discrepancy?

a.	The bacterial cells were most likely not heat-fixed to the slide.
b.	The bacterial cells were subjected to the decolorizer too long and were overdecolorized.
c.	The lot of Gram-stain reagent is most likely expired.
d.	No discrepancy exists; cells with this composition stain pink on Gram stain.

ANS: B

Bacteria with thick peptidoglycan and numerous teichoic acid cross-linkages are gram-positive cells. If the bacteria are staining gram-negative, then the cells were overdecolorized.

REF: 71 OBJ: Level: Problem Solving

1. The most critical step in the Gram stain is the application of the:

a.	safranin.
b.	crystal violet.
c.	Gram’s iodine.
d.	Gram’s decolorizer.

ANS: D

Decolorizer is the most critical step; overdecolorization or underdecolorization can occur, causing false results.

REF: 71 (71.e1) OBJ: Level: Application

1. An organism such as Mycobacterium tuberculosis would absorb which stain in its cell wall?

a.	Crystal violet
b.	Methylene blue
c.	Carbolfuchsin
d.	Malachite green

ANS: C

1. tuberculosis contains mycolic acids in its cell wall and will stain acid-fast positive. Carbolfuchsin is absorbed into the cell wall, which stains the cells pink to red. The primary stain is also in the Kinyoun acid-fast staining procedure.

REF: 73 OBJ: Level: Application

Chapter 07: Traditional Cultivation and Identification

Test Bank

MULTIPLE CHOICE

1. Organisms that have nutritional needs that are relatively complex and require extra media components to be used for growth are called:

a.	fastidious.
b.	capnophiles.
c.	neutrophils.
d.	halophiles.

ANS: A

Fastidious organisms require special nutrients to grow in the laboratory.

REF: 81 OBJ: Level: Knowledge

1. The role of the agar ingredient in culture medium is to:

a.	provide a nutritional base for bacterial metabolism.
b.	solidify the medium and provide a stable culture surface.
c.	sterilize the medium and prevent contamination.
d.	support the growth of only pathogenic organisms.

ANS: B

Agarose is a solidifying agent used to make bacterial medium solid for the growth of colonies of bacteria.

REF: 82 OBJ: Level: Knowledge

1. A bacterial colony can be described as:

a.	sufficiently large numbers of a bacterium that can be observable with the unaided eye.
b.	derived from many different types of bacterial cells.
c.	belonging to different genera and species.
d.	having different genetic and phenotypic characteristics.

ANS: A

The multiplication of a single bacterial cell into a heap of cells large enough to be observed with the naked eye results in a colony.

REF: 81 OBJ: Level: Knowledge

1. Which category of media can be described as containing specific nutrients required for the growth of particular bacterial pathogens in a patient specimen?

a.	Enrichment
b.	Supportive
c.	Selective
d.	Differential

ANS: A

Enrichment media are used to enhance the growth of a particular pathogen from a mixture of organisms.

REF: 82 OBJ: Level: Knowledge

1. Which category of media can be described as containing nutrients that support the growth of the most nonfastidious organisms without giving any particular organism a growth advantage?

a.	Enrichment
b.	Supportive
c.	Selective
d.	Differential

ANS: B

Many different types of media exist and serve different purposes in clinical microbiology. Some types are basically nutritive and support the growth of many different types of microorganisms.

REF: 83 OBJ: Level: Knowledge

1. Which category of media can be described as containing some factor or factors that allow colonies of one bacterial species or type to exhibit certain metabolic or culture characteristics that can be used to distinguish them from other bacteria growing on the same agar plate?

a.	Enrichment
b.	Supportive
c.	Selective
d.	Differential

ANS: D

Many different types of media exist and serve different purposes in clinical microbiology. Some types are differential in that they allow the discrimination of microorganisms on the basis of certain growth characteristics.

REF: 83 OBJ: Level: Knowledge

1. Which category of media can be described as containing one or more agents that are inhibitory to all organisms except those being sought?

a.	Enrichment
b.	Supportive
c.	Selective
d.	Differential

ANS: C

Many different types of media exist and serve different purposes in clinical microbiology. Some types are selective in that they contain antimicrobials, dyes, or alcohol that support the growth of one group of organisms but not another.

REF: 83 OBJ: Level: Knowledge

1. In which category of media would MacConkey agar best fit?

a.	Selective
b.	Differential
c.	Selective and differential
d.	Supportive only

ANS: C

MacConkey agar contains crystal violet to inhibit gram-positive bacteria and fungi, allowing gram-negative bacilli to grow.

REF: 86 OBJ: Level: Application

1. In which category of media would blood agar best fit?

a.	Selective
b.	Differential
c.	Selective and differential
d.	Supportive only

ANS: B

Blood agar allows the differentiation of various bacteria on the basis of the type of hemolysis present.

REF: 87 OBJ: Level: Application

1. In which category of media would Löwenstein-Jensen medium best fit?

a.	Selective
b.	Differential
c.	Selective and differential
d.	Supportive only

ANS: A

Löwenstein-Jensen medium contains malachite green to inhibit most bacteria and allow mycobacteria to grow. Factors in the media allow the mycobacteria to grow while other bacteria are inhibited. The media however does not differentiate between the various species in the mycobacteria genera. Biochemical testing is required for speciation.

REF: 83 OBJ: Level: Application

1. Which medium can be described as a nutritionally rich medium used to grow various microorganisms, either as a broth or as an agar, with or without added blood?

a.	Chocolate
b.	Colistin, nalidixic acid (CNA) blood
c.	Brain-heart infusion (BHI)
d.	Thioglycollate

ANS: C

BHI is a nutritionally rich medium that is used as both a broth and as an agar and comes with or without added blood.

REF: 86 OBJ: Level: Knowledge

1. Which medium can be described as containing hemoglobin, hemin (X factor), and the co-enzyme nicotinamide adenine dinucleotide (NAD) (V factor)?

a.	Chocolate
b.	CNA blood
c.	BHI
d.	Thioglycollate

ANS: A

Chocolate agar contains extra nutrients that are released into the agar by the lysis of the blood additive. These nutrients include hemoglobin, hemin, and NAD.

REF: 86 OBJ: Level: Knowledge

1. Which medium can be described as suppressing the growth of most gram-negative organisms while allowing gram-positive bacteria to grow?

a.	Chocolate
b.	CNA blood
c.	BHI
d.	Thioglycollate

ANS: B

CNA blood agar contains colistin and nalidixic acid, which inhibit most gram-negative organisms while allowing gram-positive bacteria to grow.

REF: 86 OBJ: Level: Knowledge

1. Which medium can be described as containing bile salts and dyes (e.g., bromothymol blue, acid fuchsin) to slow selectively the growth of most nonpathogenic gram-negative bacilli found in the gastrointestinal tract and allow Salmonella spp. and Shigella spp. to grow?

a.	Thayer-Martin agar
b.	MacConkey agar
c.	Phenylethyl alcohol (PEA)
d.	Hektoen enteric agar

ANS: D

Hektoen enteric agar contains bile salts, bromothymol blue, and acid fuchsin to inhibit the growth of nonpathogenic, gram-negative bacilli and allows Salmonella spp. and Shigella spp. to grow.

REF: 86 OBJ: Level: Knowledge

1. Which medium can be described as containing crystal violet dye to inhibit the growth of gram-positive bacteria and fungi and allows many types of gram-negative bacilli to grow?

a.	Thayer-Martin agar
b.	MacConkey agar
c.	PEA
d.	Hektoen enteric agar

ANS: B

MacConkey agar contains crystal violet dye to inhibit the growth of gram-positive bacteria and fungi and allows many types of gram-negative bacilli to grow.

REF: 86–87 OBJ: Level: Knowledge

1. What name is given to the type of hemolysis that produces incomplete hemolysis and a greening discoloration of the medium?

a.	Beta
b.	Gamma
c.	Alpha
d.	Kappa

ANS: C

The type of hemolysis described is alpha. Partial lysis of erythrocytes causes the greening of the agar.

REF: 87 OBJ: Level: Knowledge

1. What name is given to the type of hemolysis that produces complete hemolysis and a clearing of the medium?

a.	Beta
b.	Gamma
c.	Alpha
d.	Kappa

ANS: A

The type of hemolysis described is beta. Complete lysis of erythrocytes causes clearing of the agar.

REF: 87 OBJ: Level: Knowledge

1. To read the hemolytic reaction accurately on a blood agar plate, the technologist must:

a.	hold the plate up to the light, and observe the plate with the light coming from behind.
b.	hold the plate under the light, and observe the plate with the light coming from the top.
c.	hold the plate over a white background.
d.	examine the plate using reflected and transmitted light.

ANS: A

Transmitted light (i.e., passing through the agar) is required to interpret the hemolytic reaction properly on blood agar.

REF: 87 OBJ: Level: Knowledge

1. Which group of bacteria uses oxygen as a terminal electron acceptor and grows well in ambient air?

a.	Aerobes
b.	Anaerobes
c.	Capnophiles
d.	Microaerophiles

ANS: A

Various types of microorganisms require different atmospheric conditions. Aerobes grow best in the presence of ambient air.

REF: 89 OBJ: Level: Knowledge

1. Increased concentrations of carbon dioxide (CO₂) (5% to 10%) and approximately 15% oxygen (O₂) produce an environmental condition that best suits which type of organism?

a.	Aerobes
b.	Anaerobes
c.	Capnophiles
d.	Microaerophiles

ANS: C

Various types of microorganisms require different atmospheric conditions. Capnophiles grow best in the presence of increased levels of CO₂.

REF: 89 OBJ: Level: Knowledge

1. Reduced O₂ (5% to 10%) and increased CO₂ (8% to 10%) produce an environmental condition that best suits which type of organism?

a.	Aerobes
b.	Anaerobes
c.	Capnophiles
d.	Microaerophiles

ANS: D

Various types of microorganisms require different atmospheric conditions. Microaerophiles grow best in the presence of reduced of O₂ and increased CO₂.

REF: 89 OBJ: Level: Knowledge

1. A candle jar is used to cultivate which type of bacteria?

a.	Aerobes
b.	Anaerobes
c.	Capnophiles
d.	Microaerophiles

ANS: C

The burning candle in the jar lowers the O₂ level and raises the CO₂ level, allowing capnophiles to grow.

REF: 90 OBJ: Level: Application

1. The most medically important bacteria sought in the medical laboratory are cultivated using incubators with temperatures maintained in what range?

a.	35° to 37° C
b.	30° to 35° C
c.	37° to 39° C
d.	25° to 35° C

ANS: A

Temperatures of 35° to 37° C simulate those found in the body and best allow pathogens to grow.

REF: 89 OBJ: Level: Knowledge

1. An oxidase test was performed on two organisms for quality control purposes. Pseudomonas aeruginosa and Stenotrophomonas maltophilia tested positive and negative, respectively. Which of the following statements explains this discrepancy?

a.	The oxidase reagent is most likely expired.
b.	The organisms are most likely old and therefore are not properly reacting.
c.	These organisms are poor choices for quality control purposes; both are oxidase-negative organisms.
d.	No discrepancy is present. The correct results are obtained.

ANS: D

1. aeruginosa and S. maltophilia are oxidase-positive and oxidase-negative organisms, respectively; therefore the results are accurate.

REF: 97 OBJ: Level: Problem Solving

1. A positive pyrrolidonyl arylamidase (PYR) test was observed on a species of Enterococcus. What color should be observed for this reaction?

a.	Purple
b.	Red
c.	Green
d.	Pink

ANS: B

A positive PYR test produces a red color. Enterococcus spp. are PYR positive; therefore a red color would result.

REF: 97 OBJ: Level: Application

1. Oxidative or fermentative media were set up on an organism suspected of being Pseudomonas aeruginosa. What results would be expected?

a.	Yellow in both tubes
b.	Green in both tubes
c.	Yellow in the open tube and green in the closed tube
d.	Green in the open tube and yellow in the closed tube

ANS: C

1. aeruginosa is an oxidative organism; therefore only the open tube (i.e., oxidative tube) reacts and produces a yellow color. The fermentative tube (i.e., anaerobic) remains green.

REF: 98 OBJ: Level: Application

1. Generation time can be defined as the:

a.	time required for a bacterial population to double.
b.	time required for a bacterial population to triple.
c.	time required for a bacterial population to quadruple.
d.	half-life of bacteria.

ANS: A

Generation time is the time required for a bacterial population to double.

REF: 101 OBJ: Level: Knowledge

1. A catalase test was performed from a sheep blood agar plate on a colony of streptococci, and bubbling was observed. Which of the following statements explains this discrepancy?

a.	Catalase is the inappropriate test to use on colonies of streptococci; therefore the results are invalid.
b.	The colony may have been contaminated with sheep red blood cells, causing a false-positive result.
c.	The colony was most likely enterococci, not streptococci.
d.	No discrepancy is present. Streptococcus is a catalase-positive colony.

ANS: B

Sheep red blood cells produce catalase; therefore if some of the media was incorporated into the colony, a false-positive result would occur, because streptococci are catalase-negative colonies.

REF: 97 OBJ: Level: Problem Solving

1. Which of the following organisms grows best at 42º C?

a.	Streptococcus pneumonia
b.	Haemophilus influenza
c.	Neisseria gonorrhoeae
d.	Campylobacter jejuni

ANS: D

Campylobacter jejuni grows best at 42º C. The remaining organisms are fastidious and require increased oxygen concentrations at 35º to 37º C.

REF: 96 OBJ: Level: Application

1. Escherichia coli, a member of the family Enterobacteriaceae, was resistant to the antibiotic vancomycin. Which of the following statements explains this discrepancy?

a.	The vancomycin disk has most likely expired.
b.	Vancomycin should only be used in viral infections, not bacterial infections.
c.	The plate is most likely contaminated with another organism.
d.	No discrepancy is present. E. coli is resistant to vancomycin.

ANS: D

Vancomycin works best on gram-positive organisms. E. coli is a gram-negative bacterium and therefore is resistant to vancomycin; most clinically relevant gram-negative bacteria are resistant to vancomycin.

REF: 96 OBJ: Level: Problem Solving