Antimicrobial Resistance

Zone size
A. 35mm
B. 3.5 mm
C. 1.5 inches
D. 35 meters

The procedure that assures the most accurate detection of mecA-mediated oxacillin resistance in routine broth microdilution susceptibility testing against S aureus is:
A. addition of 4% NaCI
B. incubation at 30°C
C. incubation for 48 hours
D. testing with cefoxitin

You have tested B.lactamase production in a strain of H.influenzae. You go the results on the left (pink/red), that means that this strain is resistant to:
A. Chloramphenicol
B. Erythromycin
C. Penicillin
D. Trimetroprim sulfamethoxazole

The agar recommended by the Clinical and Laboratory Standard Institue for routine susceptibility testing of nonfastidious bacteria is
A. MacConkey agar
B. Middlebrook 7H10 agar
C. Mueller-Hinton agar
D. Trypticase soy agar

According to the Kirby–Bauer standard antimicrobial susceptibility testing method, what should be done when interpreting the zone size of a motile, swarming organism such as a Proteus species?
A. The swarming area should be ignored
B. The results of the disk diffusion method are invalid
C. The swarming area should be measured as the growth boundary
D. The isolate should be retested after diluting to a 0.05 McFarland standard

The minimum bactericidal concentration of an antimicrobial agent is defined as the lowest concentration of that antimicrobial agent that kills at least_____of the original inoculum
A. 95.5%
B. 97%
C. 99.9%
D. 100%

What is the MIC
A. .19 ug/ml
B. .125 ug/ml
C. .19 mg/ml
D. .125 mg/ml

Resistance to clindamycin can be induced in vitro by
A. Ampicillin
B. Erythromycin
C. Gentamicin
D. Penicillin

In disk diffusion susceptibility testing, as an antimicrobial agent diffuses away from the disk, the concentration of antibiotic is:
A. increased
B. decreased
C. unchanged
D. inoculum dependent

The most sensitive substrate for the detection of beta-lactamases is:
A. penicilin
B. ampicilin
C. cefoxitin
D. nitrocefin

Which one of the following organisms does not require susceptibility testing to the antimicrobial indicated when isolated from a clinically significant source?
A. Staphylococcus aureus clindamycin
B. Proteus mirabilis gentamicin
C. Streptococcus pyogenes penicillin
D. Escherichia coli levofloxacin

Penicillin is active against bacteria by
A. Inhibition of protein synthesis at the 30S ribosomal subunit
B. Reduction of dihydrofolic acid
C. Correct: Inhibition or peptidoglycan synthesis
D. Inhibition of nucleic acid function

The phenomenon of bacterial resistance to the bactericidal activity of penicillins and cephalosporins, with only inhibitions of organism's growth, is known as
A. High-level resistance
B. Intrinsic resistance
C. Inducible resistance
D. Tolerance

A patient is being treated with gentamicin for a Gram-negative bacterial infection. The chemistry department has repeating peak and trough orders on the patient. Which of the following antibiotic classes does gentamicin belong to?
A. Aminoglycosides
B. Beta-lactams
C. Fluoroquinolones
D. Polymyxins

The most sensitive method for the detection of β-lactamase in bacteria is by the use of:
A. Chromogenic cephalosporin
B. Penicillin
C. Oxidase
D. Chloramphenicol acetyltransferase

An Enterobacteriaceae organism will appear to be more resistant on a disk diffusion susceptibility test if the
A. depth of the agar is too thin
B. inoculum is too concentrated
C. the antimicrobial agent in disk is too concentrated
D. test interpretation occurs after 12 hours of ambient air incubation

Which of the following antimicrobial agents acts by inhibiting protein synthesis?
A. Gentamicin
B. Methicillin
C. Rifampin
D. Ampicillin

Which of the following media should be used for in vitro susceptibility testing of S. pnuemoniae?
A. Chocolate agar
B. Charcoal yeast extract agar
C. Mueller-Hinton base supplemented with 5% lysed horse blood
D. Mueller-Hinton base supplemented with 1% hemoglobin and 1% IsoVitaleX

Which of the following variables may change the results of an MIC?
A. Inoculum size
B. Incubation time
C. Growth rate of the bacteria
D. All of these options

Beta-lactamase-producing strains of Haemophilus influenzae are resistant to
A. Chloramphenicol
B. Erythromycin
C. Penicillin
D. Trimethoprim sulfamethoxazole

An antibiotic used to suppress or kill contaminating fungi in media is:
A. amphotericin B penicillin
B. chloramphenicol
C. cycloheximide
D. streptomycin

The amphotericin concentration of antibiotic that inhibits growth of a test organism is the:
A. minimum bactericidal concentration
B. minimum inhibitory concentration
C. serum bactericidal concentration
D. serum inhibitory concentration

Assume you perform microbiology for an institution submitting surveillance cultures for MRSA. Which isolate should receive further workup to rule out methicillin (oxacillin) resistance?
A. On Baird Parker agar, a gray brownish colony with no clear zone. Gram-positive cocci in clusters, catalase positive.
B. Black colonies on Chromagar. Catalase-positive, Gram-positive cocci in clusters.
C. Yellow colonies on Mannitol Salt agar; catalase-positive, coagulase-positive.
D. Clear colonies on Mannitol Salt agar; catalase-positive, coagulase-negative.

Which of the following organisms would not routinely undergo antimicrobial susceptibility testing?
A. Escherichia coli
B. Proteus mirabilis
C. Staphylococcus aureus
D. Streptococcus pyogenes

The breakpoint of an antimicrobial drug refers to
A. The amount needed to cause bacteriostasis
B. A minimum inhibitory concentration (MIC) of 16 μg/mL or greater
C. A MIC of 64 μg/mL or greater
D. The level of drug that is achievable in serum

The chemotherapeutic agents structurally similar to the vitamin p-aminobenzoic acid that act by inhibiting bacteria via inhibition of folic acid synthesis are
A. Aminoglycosides
B. Penicillins
C. Macrolides
D. Sulfonamides

Which of the following media should be used for in vitro susceptibility testing of S.pneumoniae?
A. Chocolate
B. Charcoal yeast extract agar
C. Mueller-Hinton base supplemented with 5% blood
D. Mueller-Hinton base supplemented with hematin, NAD and yeast extract

In multi-drug resistant tuberculosis (MDR-TB), which drugs normally used in first-line treatment of TB are ineffective?
A. Amikacin and kanamycin
B. Aminoglycosides
C. Fluoroquinolones
D. Isoniazid and rifampin

Which drug known to be active against parasitic infections has importance as a therapeutic agent in cases of disease caused by anaerobic bacteria?
A. Isoniazid
B. Metronidazole
C. Rifampin
D. Trimethoprim

Antibiotics routinely tested and reported for Pseudomonas aeruginosa isolates include:
A. clindamycin
B. erythromycin
C. gentamicin
D. penicillin

Oxacillin resistance in clinical strains of staphylococci is confirmed by the detection of the _______ gene.
A. vanA
B. vanB
C. mecA
D. mefA

Representative beta-lactam antibiotics and their mechanism of action include:
A. ampicillin, cefazolin and imipenem; and inhibition of cell wall synthesis
B. ampicillin, cefazolin and imipenem; and inhibition of DNA replication
C. Incorrect: ciprofloxacin, levofloxacin and aztreonam; and inhibition of cell wall synthesis
D. ciprofloxacin, levofloxacin and aztreonam; and inhibition of DNA replication

The minimum bactericidal concentration (MBC) of an antimicrobial agent is defined as the lowest concentration of that antimicrobial agent that kill at least ______ of the original inoculum.
A. 95.5%
B. 97%
C. 99.9%
D. 100%

A tech receives a call from the floor regarding antimicrobial therapy. The patient culture yielded an aerobic Gram-positive coccus and the physician would like to use an antibiotic that inhibits RNA synthesis. Which of the following antibiotics would be the best choice?
A. Ciprofloxacin
B. Ceftazidime
C. Vancomycin
D. Rifampin

Chloramphenicol is an important antimicrobial agent for the treatment of meningitis as well as several other serious infections. Unfortunately, chloramphenicol exhibits significant complications that limit its clinical usefulness. These effects include
A. Allergic reactions and anaphylaxis
B. Bone marrow suppression and aplastic anemia
C. Significant gastrointestinal manifestations
D. Photosensitivity

Which of the following is not one of the standard control organisms used for the weekly testing of antimicrobial disks?
A. Staphylococcus epidermidis(ATCC 25833)
B. Pseudomonas aeruginosa(ATCC 27853)
C. Escherichia coli(ATCC 25922)
D. Enterococcus faecalis(ATCC 29212)

When using the rapid chromogenic cephalosporin method for the detection of beta-lactamase production by an organism, a positive test is indicated by the color
A. Yellow
B. Green
C. Red
D. Blue

A tech receives a call from the floor regarding antimicrobial therapy. The patient culture yielded an aerobic Gram-negative bacillus and the physician would like to use an antibiotic that inhibits cell wall synthesis. Which of the following antibiotics would be the best choice?
A. Gentamycin
B. Tetracycline
C. Ciprofloxacin
D. Cefazolin

Clavulanic acid is classified as a
A. Beta lactam
B. Beta lactamase inhibitor
C. Macrolide
D. Aminoglycosisde

Susceptibility testing performed on quality control organisms using a new media lot number yielded zone sizes that were too large for all antibiotics tested. The testing was repeated using media from a previously used lot number, and all zone sizes were acceptable. The unacceptable zone sizes are best explained by the:
A. antibiotic disks were not stored with the proper desiccant
B. depth of the media was too thick
C. depth of the media was too thin
D. antibiotic disks were not properly applied to the media

Sulfonamides, such as sulfamethoxazole (SMZ), and trimethoprim (TMP), work by targeting:
A. Penicillin-binding proteins; disrupting bacterial cell wall synthesis
B. Tetrahydrofolate synthesis; preventing bacterial DNA synthesis
C. 30S ribosomal subunits; inhibiting bacterial protein translation
D. 50S ribosomal subunits; inhibiting bacterial protein translation

An example of bactericidal antibiotic is
A. Chloramphenicol
B. Erythromycin
C. Tetracycline
D. Tobramycin

Which of the following organisms would not routinely undergo antimicrobial susceptibility testing?
A. E.coli
B. P.mirabilis
C. S.aureus
D. S.pyogenes

Gene that encodes for Vancomycin resistance
A. MecA
B. VanC
C. ESBL
D. VanA

The following statement is true regarding hospital-associated methicillin-resistant Staphylococcus aureus (HA-MRSA) and community-associated MRSA (CA-MRSA)?
A. Resistance is conferred by the mecA gene for only the HA strains.
B. CA strains tend to demonstrate resistance to more drug classes than HA strains.
C. CA strains tend to be associated with the PVL gene and skin and soft tissue infections.
D. HA Strains are typically more susceptible to non-beta-lactam antibiotics.

A suspension of the test organism for use in broth dilution and disk diffusion testing is adjusted to match the turbidity of a
A. #0.5 McFarland Standard
B. #1.0 McFarland Standard
C. #2.0 McFarland Standard
D. #3.0 McFarland Standard

The supervisor of a microbiology laboratory has been asked to begin performing in vitro antimicrobial susceptibility testing of Mycobacterium tuberculosis because of an increase in reported resistance in his community. Which of the following methods would be appropriate for this testing?
A. Broth microdilution method using Mueller-Hinton brother
B. Kirby-Bauer method
C. BACTEC method
D. Schlichter method

When performing antimicrobial susceptibility testing on Enterobacteriaceae, first-generation cephalosporins can be adequately represented by:
A. cefuroxime
B. ceftriaxone
C. cefazolin
D. cefonicid

The extended-spectrum beta-lactamases confer resistance to
A. Amoxicillin
B. Ceftriaxone
C. Erythromycin
D. Rifampin

The extended spectrum beta lactamases (ESBL) confer resistance to
A. Erythromicin
B. Vancomycin
C. ceftriaxone
D. Gentamycin

Which of the following antimicrobial agents acts by inhibiting cell wall synthesis?
A. Clindamycin
B. Gentamicin
C. Naladixic acid
D. Vancomycin

A tech receives a request for VRE colonization testing on a patient in the hospital. Which of the following is an appropriate area of the body for culture for screening?
A. Anterior nares
B. Rectal area
C. Groin
D. Urine

A quality control procedure on a new batch of Mueller-Hinton agar plates using a Staphylococcus aureus ATCC strain and incubation in ambient air resulted in all the disk zone sizes measuring too small. The most likely reason for this is that the:
A. Mueller-Hinton plates were poured too thin
B. potency of the antibiotic disks is too high
C. bacterial suspension was not diluted to the proper concentration
D. incubation should have been in a 5-10% CO2 atmosphere

Which of the 2 different antimicrobial agents listed below are commonly used and may result in synergistic action in the treatment of endocarditis caused by Enterocolcus faecalis?
A. an aminoglycoside and a macrolide
B. a penicillin derivative and an aminoglycoside
C. a cell membrane active agent and nalidixic acid
D. a macrolide and a penicillin derivative

Which class of antibiotics is used for the treatment of serious gram-negative infections as well as infections with Mycobacterium tuberculosis?
A. Cephalosporins
B. Penicillins
C. Tetracyclines
D. Aminoglycosides

When performing a disk diffusion susceptibility test, the antibiotic disks are placed on the agar 30 minutes after organism inoculation and then incubated within 15 minutes of the disk placement. This procedure will result in:
A. the antibiotic not diffusing into the medium, resulting in no zone
B. decreased zone diameters
C. increased zone diameters
D. no effect on the final zone diameter

Which of the following media should be used for in vitro susceptibility testing of S.pneumoniae?
A. Chocolate
B. Charcoal yeast extract agar
C. Mueller-Hinton base supplemented with 5% blood
D. Mueller-Hinton base supplemented with hematin, NAD and yeast extract

When testing the antimicrobial susceptibilty of H.influenzae strains by disk-agar diffusion the recommended medium is
A. regular MH
B. Sheep blood MH
C. Chocolate
D. Haemophilus test medium

In this image is a quadrant plate containing brain heart infusion agar supplemented with 6 µg/mL of vancomycin. The right upper quadrant was inoculated with the test strain of Enterococcus faecium. The presence of growth in the inoculated quadrant indicates ___________?
A. The organism is susceptible to vancomycin
B. The organism is not E. faecium.
C. The organism is resistant to vancomycin
D. The plate is contaminated and a repeat should be performed.

According to the Kirby-bauer standard antimicrobial susceptibility testing method, what should be done when interpreting the zone size on a motile, swarming organism such as a Proteus species?
A. The swarming area should be ignored
B. The results o the disk diffusion method are invalid
C. The swarming area should be measured as the growth boundary
D. The isolate should be retested after diluting to a 0.05 McFarland standard

The extended spectrum beta lactamases (ESBL) confer resistance to :
A. Erythromycin
B. Vancomycin
C. Ceftriaxone
D. Chloramphenicol

The pH of the agar used for the Kirby-Bauer test should be
A. 7.0-7.2
B. 7.2-7.4
C. 7.4-7.6
D. 7.6-7.8

When testing the antimicrobial susceptibility of Haemophilus influenzae strains by disk-agar diffusion, the recommended medium is
A. Chocolate agar
B. Charcoal yeast extract agar
C. Mueller-Hinton base supplemented with 5% sheep blood
D. Mueller-Hinton base supplemented with hematin, NAD, and yeast extract

An antibiotic that inhibits cell wall synthesis is:
A. chloramphenicol
B. colistin
C. penicillin
D. sulfamethoxazole

The organisms Klebsiella pneumoniae, Enterobacter cloacae, and Escherichia coli can produce carbapenemases due to which of the following genes?
A. mec A
B. van A
C. blaKPC
D. van B

A Klebsiella pneumoniae isolate is known to produce carbapenemase; therefore, it therapeutically will not respond to the antibiotics:
A. amoxicillin, cefazolin and imipenem
B. colistin and rifampin
C. sulfamethoxazole and trimethoprim-sulfamethoxazole
D. tetracycline and doxycycline

The term that denotes a situation in which the effect of two antimicrobial agents together is greater than the sum of the effects of either drug alone is
A. Additivism
B. Antagonism
C. Sensitivity
D. Synergism

Metronidazole is most commonly recommended for treatments of infections caused by
A. Aerobic microorganisms
B. Microaerophilic microorganisms
C. Obligate anerobic microorganisms
D. Obligate intercellular microorganisms

Penicillin resistance in Neisseria gonorrhoeae can be due to the organism producing:
A. beta-D-galactosidase
B. beta-lactamase
C. butyrate esterase
D. DNase

Clavulanic acid is classified as
A. Beta-lactam
B. Beta-lactamase inhibitor
C. Macrolide
D. Aminoglycoside

Kirby bauer-disk diffusion test is:
A. qualitative
B. quantitative

Rapid testing for beta-lactamase production is recommended, before initiation of antimicrobial therapy, for isolates of
A. Serratia marcescens
B. Haemophilus influenzae
C. Staphylococcus epidermidis
D. Streptococcus pyogenes

A tech working in the laboratory receives a VRE screening culture. Which of the following agars should the tech use to set up the VRE screening culture?
A. Bile-esculin-azide (BEA) agar with vancomycin
B. Columbia Nalidixic acid (CNA) agar
C. MacConkey agar
D. Buffered Charcoal yeast extract (BYCE) agar