Micro Unit 4 Review -
A bacterial suspension of 1.5 × 108 colony-forming units (CFUs)/mL is comparable with which McFarland standard? 0.5 1.0 1.5 2.0
0.5
Match the antimicrobial agent with its mode of action. 1. Penicillin 2. Vancomycin 3. Polymyxin B 4. Gentamicin 5. Tetracycline 6. Rifampin 7. Ciprofloxacin A. DNA and ribonucleic acid (RNA) synthesis inhibition B. Cell wall synthesis inhibition C. Cell wall synthesis inhibition D. Protein synthesis inhibition E. Cell membrane function inhibition F. DNA and ribonucleic acid (RNA) synthesis inhibition G. Protein synthesis inhibition
1. B. 2. C. 3. E. 4. D 5. G. 6. A. 7. F.
Standardization of antimicrobial susceptibility testing optimizes bacterial growth so inhibition of growth can be attributed to the antimicrobial agents tested and results are accurate, reproducible, and consistent regardless of the microbiology laboratory performing the test. Which of the following incubation conditions are used for common (i.e., nonfastidious) bacterial isolates using manual techniques? 16 to 20 hours, 35°C, 5-8% CO2 16 to 20 hours, 35°C, ambient air 20 to 24 hours, 35°C, 5-8% CO2 20 to 24 hours, 35°C, ambient air **** the choices are something like this but not exact. The answer is correct though.
16 to 20 hours, 35°C, ambient air
Primary cultivation of most medically relevant organisms and colonial morphologic interpretations are completed at: 6 to 8 hours post inoculation. 16 to 18 hours post inoculation. 18 to 24 hours post inoculation. 16 to 24 hours post inoculation.
18 to 24 hours post inoculation.
Predict which of the following DNA oligonucleotide probes would have the highest melting temperature (Tm) when hybridizing to the target sequence 5'-GTGCCTGAATGCAATGTCA-3'. 3'-CACGGA-5' 3'-CATGGA-5' 3'-TTACAG-5' 3'-TTACTG-5'
3'-CACGGA-5'
The most medically important bacteria sought in the medical laboratory are cultivated using incubators with temperatures maintained in what range? 35°C to 37°C 30°C to 35°C 37°C to 39°C 25°C to 35°C
35°C to 37°C
Identify the appropriate DNA homolog, or complementary sequence, that could be used as a probe for in situ hybridization to the following target RNA: 5'-AUGCGAUUC-3' 5'-TACGCTAAG-3' 5'-ATGCGATTC-3' 5'-GAATCGCAT-3' 5'-AUGCGAUUC-3'
5'-GAATCGCAT-3'
If a patient sample contains 8 copies of viral DNA, predict how many DNA copies would be present following three rounds of PCR amplification. 16 24 32 64
64
The enzyme that is commonly used for primer extensions in the PCR method works best at what temperature? 25°C 56°C 72°C 94°C
72°C
Place the basic steps involved in a molecular hybridization assay in sequence from first to last in the order in which they would be performed. - Heating sample to obtain single-stranded target nucleic acid, hybridization of target to probe, detection of hybridization, labeling of probe - Labeling of probe, heating sample to obtain single-stranded target nucleic acid, hybridization of target to probe, detection of hybridization - Hybridization of target to probe, detection of hybridization, labeling of probe, heating sample to obtain single-stranded target nucleic acid - Hybridization of target to probe, labeling of probe, heating sample to obtain single-stranded target nucleic acid, detection of hybridization
Labeling of probe, heating sample to obtain single-stranded target nucleic acid, hybridization of target to probe, detection of hybridization
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? The oxidase reagent is most likely expired. The organisms are most likely old and therefore are not properly reacting. These organisms are poor choices for quality control purposes; both are oxidase-negative organisms. No discrepancy is present. The correct results are obtained.
No discrepancy is present. The correct results are obtained.
Antibiotic resistance resulting from altered cellular physiologic structure caused by changes in a microorganism's usual genetic makeup is known as __________ resistance. intrinsic inherent acquired environmentally mediated
acquired
Advantages of automated susceptibility tests (e.g., Vitek 2 and Microscan Walkaway) include but are not limited to: automated preparation of inoculum. resistance detection by molecular methods (e.g., real-time PCR). advanced (e.g., expert) software that recognizes and reports resistance patterns. testing of most aerobic and commonly isolated anaerobic bacterial species.
advanced (e.g., expert) software that recognizes and reports resistance patterns.
Interpretation of biochemical tests requires that the microbiologist: correlate the biochemical results with the suspect organism identification. correlate the biochemical results with the preliminary direct smear and staining characteristics. utilize quality control organisms during interpretation to insure proper functioning of the test protocol. all of the above are required.
all of the above are required.
Data review process for AST profiles: - requires susceptibility testing results only. - is the responsibility of a single individual in the laboratory. - can be done on "as needed" basis, no less frequently than weekly. - allows for troubleshooting of unusual profiles and results to be held until resolved.
allows for troubleshooting of unusual profiles and results to be held until resolved
Enterococcal high-level gentamicin resistance predicts resistance to: vancomycin. aminoglycosides. cephalosporins. levofloxacin.
aminoglycosides.
A Weil-Felix test was performed on serial dilutions from a patient bitten by a tick. The results obtained were positive for OX-19 and negative for OX-2 and OX-K. Based on these findings, the organism can be identified as: R. rickettsii. O. tsutsugamushi. Rickettsia prowazekii. Rickettsia typhi.
R. rickettsii
Binary fission within vacuoles divides which of the following forms of Chlamydia? RB EB Replicate body Initial body
RB
As a result of the organism going through several doubling generations of growth before inhibition, a haze of bacterial growth occurs on the agar around the disk. This phenomenon, which should be ignored, can be observed when testing which class of antibiotics? Aminoglycosides Sulfonamides Penicillins Cephalosporins
Sulfonamides
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? Enrichment Supportive Selective Differential
Supportive
A newly defined interpretive category termed "Susceptible-Dose Dependent" (SDD) implies susceptibility of an isolate is dependent on dosing regimen. Which of the following statements is correct? SDD is included within the susceptible category definition. SDD is assigned to therapeutic agents that are approved under investigational use only. The infecting organism may be effectively treated by using higher doses or more frequent doses or both of the drugs. Drugs in this category have narrow therapeutic indices and their use at nonconventional ways must be monitored closely.
The infecting organism may be effectively treated by using higher doses or more frequent doses or both of the drugs
Oxidative or fermentative media were set up on an organism suspected of being P. aeruginosa. What results would be expected? - Yellow in both tubes - Green in both tubes - Yellow in the open tube and green in the closed tube - Green in the open tube and yellow in the closed tube
Yellow in the open tube and green in the closed tube
Assaying bacterial isolates for resistance genes by molecular methods: can detect unknown resistance genes not yet defined. cannot detect phenotypic resistance due to a combination of mechanisms. means the resistance gene is expressed if found to be present. is currently part of the routine clinical microbiology workflow for all isolates.
cannot detect phenotypic resistance due to a combination of mechanisms.
Staphylococcus aureus is a gram-positive organism that produces the enzyme β-lactamase, which renders certain types of antibiotics inactive. The mode of action that is prevented in certain antibiotics sensitive to this enzyme is: cell wall synthesis. protein synthesis to the 30S ribosomal subunit. protein synthesis to the 50S ribosomal subunit. deoxyribonucleic acid (DNA) synthesis.
cell wall synthesis
Enterococcal resistance to ampicillin predicts resistance to: vancomycin. aminoglycosides. cephalosporins. linezolid.
cephalosporins
Staphylococcal resistance to oxacillin is used to determine and report resistance to: aminoglycosides. cephalosporins. vancomycin. amikacin.
cephalosporins
Escherichia coli, a member of the family Enterobacteriaceae, was resistant to the antibiotic vancomycin. Which of the following statements explains this discrepancy? - The vancomycin disk has most likely expired. - Vancomycin should only be used in viral infections, not bacterial infections. - The plate is most likely contaminated with another organism. - No discrepancy is present. E. coli is resistant to vancomycin.
No discrepancy is present. E. coli is resistant to vancomycin
In the microdilution broth dilution method, the interpretive criteria for the susceptible, intermediate, or resistant categories are based on the: - quantitative differences (i.e., CFU/mL) in the turbidity in the test well. - correlation of the MIC with serum-achievable levels of the common doses of the antimicrobial agent and therapeutic outcomes based on clinical studies. - either the presence or absence of zones of inhibition. - FDA's recommendations based on a national database of participating health care agencies providing antibiograms for review and publication as a summative report.
correlation of the MIC with serum-achievable levels of the common doses of the antimicrobial agent and therapeutic outcomes based on clinical studies.
Quality control results for disk diffusion AST using appropriate ATCC strains of bacteria showed zone size diameters decreasing over time for a few antimicrobials. Which of the following statements is a possible explanation? Antimicrobial disks were stored in a frost-free freezer. Concentration of the bacterial inoculum was 5 × 105 CFU/mL. Depth of Mueller-Hinton agar plates measured 3 mm. Plates were incubated less than 16 hours in ambient air.
Antimicrobial disks were stored in a frost-free freezer
The most common sexually transmitted bacterial pathogen and a major cause of pelvic inflammatory disease (PID) is: Rickettsia rickettsii. Chlamydia trachomatis. Klebsiella granulomatis. Coxiella burnetii.
Chlamydia trachomatis
Which medium can be described as containing hemoglobin, hemin (X factor), and the co-enzyme nicotinamide adenine dinucleotide (NAD) (V factor)? Chocolate CNA blood BHI Thioglycollate broth
Chocolate
The laboratory method of choice to identify Mycoplasma and Ureaplasma infections is: enzyme-linked immunosorbent assay (ELISA). direct fluorescent antibody (DFA). latex agglutination. real-time polymerase chain reaction (PCR).
real-time polymerase chain reaction (PCR)
Tropheryma whipplei is characterized by the presence of periodic acid-Schiff (PAS)-staining macrophages, which indicates mucopolysaccharide or glycoprotein, in almost every organ system. Without treatment, this disease is uniformly fatal. Identification is achieved using: enzyme-linked immunosorbent assay (ELISA). IFA. immunoblotting. real-time polymerase chain reaction (PCR).
real-time polymerase chain reaction (PCR).
Media prepared in the laboratory should be tested for quality using all of the following except: check test organism viability for expected growth. confirm identify of organism using Gram stain. check the pH of the media. record lot number.
record lot number
Media function testing should include all of the following except: check test organism viability for expected growth. confirm identity of organism using Gram stain. compare performance to previous lot number of media. reincubate for additional time period if no growth is evident.
reincubate for additional time period if no growth is evident.
Antimicrobial susceptibility testing should be performed when: - a single bacterial species grows from any body site. - an isolate has a predictable susceptibility profile to therapeutic drugs of choice. - reliable standardized methods for testing a clinically significant isolate exist. - administering intravenous or oral antibiotics to treat an infection.
reliable standardized methods for testing a clinically significant isolate exist
The enzyme that has the ability to synthesize DNA from ribonucleic acid (RNA) is called: DNA polymerase. RNAse. helicase. reverse transcriptase.
reverse transcriptase
For clinical decision-making carbapenemase production should be detected using: MALDI-TOF mass spectrometry. Modified Hodge test or Carba NP test. molecular methods for specific carbapenemases. routine AST methods using current CLSI interpretive criteria.
routine AST methods using current CLSI interpretive criteria.
The limit of detection in the microbiology laboratory is termed: specificity. sensitivity. precision. variation.
sensitivity.
Hybridization methods are based on: - the ability of two nucleic acid strands that have complementary base sequences to bond specifically with each other and form a double-stranded molecule. - detecting phenotypic traits not detectable by conventional strategies. - the principles of complementary nucleic acid hybridization with those of nucleic acid replication that are repeatedly applied through numerous cycles. - determining the exact nucleotide sequence of a gene or gene fragment obtained from an organism.
the ability of two nucleic acid strands that have complementary base sequences to bond specifically with each other and form a double-stranded molecule
A bacterial colony can be described as: - sufficiently large numbers of a bacterium that can be observable with the unaided eye. - derived from many different types of bacterial cells. - belonging to different genera and species. - having different genetic and phenotypic characteristics.
sufficiently large numbers of a bacterium that can be observable with the unaided eye
A staphylococcal isolate that gives a negative result using the Cefinase disk and tests resistant to penicillin by disk diffusion means that: the isolate may contain the mecA gene. the bacteria produce the β-lactamase enzyme. the isolate is also resistant to ampicillin, carbenicillin, ticarcillin, and imipenem. the isolate is also resistant to oxacillin, cefoxitin, and ticarcillin-clavulanate.
the isolate may contain the mecA gene.
Target nucleic acid amplification (polymerase chain reaction [PCR]) methods are based on: - the ability of two nucleic acid strands that have complementary base sequences to bond specifically with each other and form a double-stranded molecule. - detecting phenotypic traits not detectable by conventional strategies. - the principles of complementary nucleic acid hybridization with those of nucleic acid replication that are repeatedly applied through numerous cycles. - determining the exact nucleotide sequence of a gene or gene fragment obtained from an organism.
the principles of complementary nucleic acid hybridization with those of nucleic acid replication that are repeatedly applied through numerous cycles.
When streaking for isolation and utilizing semi-quantitative methods, the numbers of colonial growth in successive quadrants correlates directly with: - the microbiologist's streaking technique. - the relative amount of organism present in the original specimen. - the ability of the organism to grow on the media. - the type of incubation conditions.
the relative amount of organism present in the original specimen
When streaking for isolation and utilizing semi-quantitative methods, the numbers of colonial growth in successive quadrants correlates directly with: the microbiologist's streaking technique. the relative amount of organism present in the original specimen. the ability of the organism to grow on the media. the type of incubation conditions.
the relative amount of organism present in the original specimen
Generation time can be defined as the: - time required for a bacterial population to double. - time required for a bacterial population to triple. - time required for a bacterial population to quadruple. - half-life of bacteria.
time required for a bacterial population to double
Generation time can be defined as the: time required for a bacterial population to double. time required for a bacterial population to triple. time required for a bacterial population to quadruple. half-life of bacteria.
time required for a bacterial population to double.
Colonial morphology that appears as a "checker" or dipped in the middle with raised edges is termed: flat. convex. umbilicate. variable.
umbilicate
Match the antimicrobial agent with its mode of action. Penicillin Vancomycin Polymyxin B Gentamicin Tetracycline Rifampin Ciprofloxacin A. DNA and ribonucleic acid (RNA) synthesis inhibition B. Cell wall synthesis inhibition C. Cell wall synthesis inhibition D. Protein synthesis inhibition E. Cell membrane function inhibition F. DNA and ribonucleic acid (RNA) synthesis inhibition G. Protein synthesis inhibition
unsure. I got 1.4 out of 2 penicillin b vancomycin c polymyxin b e gentamicin g tetracycline d rifampin a ciprofloaxcin f
The serum bactericidal test (SBT) involves: - serial dilutions of antimicrobials in cation-adjusted Mueller-Hinton broth. - 99.9% reduction in CFU/mL, compared with the organism concentration in the original inoculum. - using the patient's serum to detect its bacteriostatic and bactericidal activity. - subculturing the tubes of a completed broth dilution test showing no visible growth.
using the patient's serum to detect its bacteriostatic and bactericidal activity
What name is given to the type of hemolysis that produces incomplete hemolysis and a greening discoloration of the medium? β γ α κ
α
What name is given to the type of hemolysis that produces complete hemolysis and a clearing of the medium? β γ α κ
β
Organisms that have nutritional needs that are relatively complex and require extra media components to be used for growth are called: fastidious. capnophiles. neutrophils. halophiles.
fastidious
Characteristic colonial morphology should include all of the following except: glistening. fermenter. pinpoint. entire.
fermenter.
Bactericidal tests should be performed: - for severe and life-threatening infections. - for every clinically significant organism isolated from a clinical specimen. - for evaluation of antimicrobial agents usually considered bacteriostatic. - for bacteria isolated from wounds, whether or not they are clinically significant.
for severe and life-threatening infections
The C. burnetii, an acute systemic infection, primarily affects the lungs and can exist in two antigenic states. The reference method that is both highly specific and sensitive and is recommended for identification is: immunofluorescent antibody (IFA). direct fluorescent antibody (DFA). Western blot. latex agglutination.
immunofluorescent antibody (IFA).
A D-test is set up on a S. aureus isolate. There was no zone around the Erythromycin disk and the zone of inhibition around the clindamycin disk adjacent to the erythromycin disk was interpreted as susceptible. Thus, the resistance mechanism for the erythromycin is due to: altered target. increased efflux. decreased porin channels. degradative enzymes.
increased efflux
Antimicrobial resistance resulting from the normal genetic, structural, or physiologic state of a microorganism is referred to as ________ resistance. intrinsic inherent microorganism-mediated clinical
intrinsic
The minimum inhibitory concentration (MIC) result recorded in antimicrobial testing can be defined as the: - lowest concentration of antimicrobial agent that should be used for optimal therapy. - highest concentration of antimicrobial agent that should be used for optimal therapy. - lowest antimicrobial agent concentration that completely inhibits visible bacterial growth. - highest antimicrobial agent concentration that completely inhibits visible bacterial growth.
lowest antimicrobial agent concentration that completely inhibits visible bacterial growth
The natural habitat of Mycoplasma spp., which causes infectious disease in humans, can best be described as the: mucous membranes of humans. aquatic environment. natural environment. genitourinary tract of animals.
mucous membranes of humans.
Media function testing should be performed on commercially prepared media when: organisms expected to grow on the media demonstrate growth. daily as required. on all new lots of media. only when the identity and growth characteristics appear abnormal.
only when the identity and growth characteristics appear abnormal
Colonies that appear white and shinny are also considered: translucent. transparent. mucoid. opaque.
opaque
The probe in the hybridization assay can be described as: originating from the unknown organism to be detected or identified. a reporter molecule that chemically forms a complex with the single-stranded probe deoxyribonucleic acid (DNA). originating from an organism of known identity with a known sequence. the enzyme needed to elongate the strand.
originating from an organism of known identity with a known sequence.
The target in the hybridization assay can be described as: - originating from the unknown organism to be detected or identified. - a reporter molecule that chemically forms a complex with the single-stranded probe DNA. - originating from an organism of known identity. - an enzyme that adds nucleotides during the replication process.
originating from the unknown organism to be detected or identified
The target in the hybridization assay can be described as: originating from the unknown organism to be detected or identified. a reporter molecule that chemically forms a complex with the single-stranded probe DNA. originating from an organism of known identity. an enzyme that adds nucleotides during the replication process.
originating from the unknown organism to be detected or identified.
Quality control from commercially prepared media includes all of the following except: - receipt and verification of storage or transportation conditions. - visual inspection for discoloration or contamination. - pH the media using litmus paper. - verification of lot numbers and expiration dates.
pH the media using litmus paper
Clinical sensitivity in the microbiology laboratory refers to: positive results from patients known to have an infection or disease. percentage of positive results from all patients tested. percentage of patient's that test negative known to have an infection or disease. none of the above answers are correct.
positive results from patients known to have an infection or disease
The mechanism of acquired, high-level resistance to vancomycin involves: - enzymatic destruction of the antibiotic. - altered antibiotic targets. - decreased intracellular uptake of the drug. - production of altered cell wall precursors that do not bind the antibiotic with sufficient avidity.
production of altered cell wall precursors that do not bind the antibiotic with sufficient avidity.
Chromogenic cephalosporins are used to test for: - degradative/hydrolytic action of β-lactamase inhibitors. - intrinsic resistance to β-lactam drugs by increased efflux of the drug. - production of β-lactamase by the infecting organism. - intrinsic resistance to β-lactam drugs by altered antibiotic targets.
production of β-lactamase by the infecting organism
Chromogenic cephalosporins are used to test for: degradative/hydrolytic action of β-lactamase inhibitors. intrinsic resistance to β-lactam drugs by increased efflux of the drug. production of β-lactamase by the infecting organism. intrinsic resistance to β-lactam drugs by altered antibiotic targets.
production of β-lactamase by the infecting organism
An important requirement for appropriate inoculum preparation in susceptibility testing includes the use of a(n): pure culture. single isolated colony. variety of colony morphotypes. inoculum equivalent to the bacterial burden at the site of infection.
pure culture
Which group of bacteria uses oxygen as a terminal electron acceptor and grows well in ambient air? Aerobes Anaerobes Capnophiles Microaerophiles
Aerobes
Which antimicrobial susceptibility testing method uses a series of plates with different antimicrobial concentrations inoculated with multiple bacterial isolates per plate? Agar dilution Automated broth dilution Disk Diffusion E-test
Agar dilution
Isothermal amplification techniques, such as NASBA, utilize a single temperature for nucleic acid amplification thereby eliminating the need for thermal cycling instruments to precisely and quickly alter the reaction temperature. This often reduces the cost associated with molecular testing and infrastructure requirements. In what settings could this be advantageous? - Developing countries with limited health care facilities - Field clinics during military operations - Small clinics or hospitals without centralized laboratory facilities - Urgent care clinics or pharmacies for point-of-care diagnosis - All of the above
All of the above
Complementary nucleic acid hybridization, which is coupled with nucleic acid replication and applied repeatedly through numerous cycles, is based on which of the following methods? Hybridization Sequencing Amplification (PCR) Genotypic
Amplification (PCR)
The optimal way to detect PCR amplicons is to use which stain? Methylene blue Malachite green Bromothymol blue Ethidium bromide
Ethidium bromide
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? Chocolate Colistin, nalidixic acid (CNA) blood Brain-heart infusion (BHI) Thioglycollate broth
Brain-heart infusion (BHI)
Of the following organisms, which has a unique developmental life cycle including a replicative form, the reticulate body (RB), and an extracellular, metabolically inert, infective form, the elementary body (EB)? Rickettsia Chlamydia Ehrlichia Coxiella
Chlamydia
Which medium can be described as suppressing the growth of most gram-negative organisms while allowing gram-positive bacteria to grow? Chocolate CNA blood BHI Thioglycollate broth
CNA blood
Which of the following organisms grows best at 42°C? Streptococcus pneumonia Haemophilus influenza Neisseria gonorrhoeae Campylobacter jejuni
Campylobacter jejuni
A candle jar is used to cultivate which type of bacteria? Aerobes Anaerobes Capnophiles Microaerophiles
Capnophiles
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? Aerobes Anaerobes Capnophiles Microaerophiles
Capnophiles
Which of the following vectors transmit scrub typhus? Lice Ticks Fleas Chiggers
Chiggers
Up-to-date tables that list potential antimicrobial agents to include in batteries for testing against particular organisms or organism groups are published by the: Centers for Disease Control and Prevention (CDC). U. S. Food and Drug Administration (FDA). Manual of Standard Operating Procedures (MSOP). Clinical and Laboratory Standards Institute (CLSI).
Clinical and Laboratory Standards Institute (CLSI).
The primary goal of antimicrobial susceptibility testing is to: - Determine whether the pathogen expresses resistance to the potential therapeutic antimicrobial agents. - Determine the spectrum of an organism's intrinsic resistance. - Determine whether the administered antibiotic is effective at killing the pathogen in vivo. - Identify toxins secreted by bacterial pathogens isolated from a clinical specime
Determine whether the pathogen expresses resistance to the potential therapeutic antimicrobial agents
In which category of media would blood agar best fit? Selective Differential Selective and differential Supportive only
Differential
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? Enrichment Supportive Selective Differential
Differential
S. pneumoniae was isolated from a spinal fluid sample from an inpatient. An oxacillin disk screening test was performed and the zone of inhibition measured 19 mm. Which action is most appropriate? Call patient's physician and report the isolate as oxacillin-resistant; no further work-up required. Repeat testing to confirm the identification of the isolate and qualitative susceptibility profile. Report the isolate as penicillin-resistant; inform infection control and patient's physician. Do E-test and report quantitative MIC result and interpretive category using meningitis MIC criteria.
Do E-test and report quantitative MIC result and interpretive category using meningitis MIC criteria.
Which enzyme recognizes a specific nucleotide sequence (~4 to 8 nucleotides in length) and catalyzes the digestion of the nucleic acid at that site, causing a break in the DNA strand? Ligase Gyrase Helicase Endonuclease
Endonuclease
Which category of media can be described as containing specific nutrients required for the growth of particular bacterial pathogens in a patient specimen? Enrichment Supportive Selective Differential
Enrichment
Which group of drugs is effective against M. pneumoniae infections? β-Lactams Sulfonamides Cephalosporins Fluoroquinolones
Fluoroquinolones
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? Thayer-Martin agar MacConkey agar Phenylethyl alcohol (PEA) Hektoen enteric agar
Hektoen enteric agar
The ability of two nucleic acid strands, a probe and a target, which have complementary base sequences that specifically bond with each other and form a double-stranded molecule, drives which of the following methods? Hybridization Sequencing Amplification (PCR) Genotypic
Hybridization
Which type of hybridization method would be the optimal choice to use to detect a lesion infected with a particular virus? Southern In situ Peptide nucleic acid Sandwich
In situ
While developing a new hybridization-based molecular test for Cryptosporidium, a protozoan parasite that causes diarrheal illness, a laboratory technician examines the hybridization ability with a closely related, but nontarget, protozoan and also gets a positive test result. In order to improve the stringency of the hybridization reaction for detection of Cryptosporidium only, the technician can do which of the following? Decrease the salt concentration in the hybridization buffer Increase the salt concentration in the hybridization buffer Reduce the reaction temperature during hybridization Remove destabilizing agents, such as formamide, from the hybridization buffer None of the above
Increase the salt concentration in the hybridization buffer
Analytical sensitivity is concerned primarily with which of the following PCR parameters? Target specificity Limit of detection Head-to-head comparison to a gold-standard test Gram staining
Limit of detection
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? Thayer-Martin agar MacConkey agar PEA Hektoen enteric agar
MacConkey agar
Reduced O2 (5% to 10%) and increased CO2 (8% to 10%) produce an environmental condition that best suits which type of organism? Aerobes Anaerobes Capnophiles Microaerophiles
Microaerophiles
In the disk diffusion method of antimicrobial susceptibility testing, what is the standard medium used for testing most bacterial organisms? Mueller-Hinton broth Mueller-Hinton agar Brain-heart infusion agar Brucella broth with 5% lysed horse blood
Mueller-Hinton agar
Which of the following agents lacks a cell wall and is the smallest known free-living form? Chlamydia Mycoplasma Rickettsia Coxiella
Mycoplasma
Which of the following Mycoplasma species is associated with individuals who are positive for human immunodeficiency virus (HIV), is capable of invading human cells, and can modulate the immune system? M. pneumoniae M. genitalium M. hominis Mycoplasma fermentans
Mycoplasma fermentans
The definitive identification of which of the following organisms is accomplished by hemadsorption techniques? Chlamydia trachomatis Mycoplasma hominis Mycoplasma pneumoniae Mycoplasma genitalium
Mycoplasma pneumoniae
Klebsiella spp. were isolated from a sputum sample, and susceptibility testing was performed. The isolates were sensitive to several antibiotics; however, they were resistant to ampicillin. Which one of the following statements explains this discrepancy? - The ampicillin disk is most likely expired. - Because Klebsiella spp. should be sensitive to ampicillin, a technical error is to blame. - Ampicillin inhibits cell wall synthesis. In addition, because Klebsiella spp. do not have a cell wall, they should not have been tested for ampicillin. - No discrepancy is present; Klebsiella spp. are normally resistant to ampicillin.
No discrepancy is present; Klebsiella spp. are normally resistant to ampicillin
Which of the following steps are crucial for the success of a nucleic acid amplification test, such as PCR? Nucleic acid purification Fluorescent resonance energy transfer (FRET) Melting temperature analysis Nucleic acid sequencing
Nucleic acid purification
What action should be taken for any isolate found to be nonsusceptible (NS) to a particular antimicrobial agent? No additional action is needed, as these results can occur with any organism. Organism's identification and susceptibility test results should be confirmed. The patient report should indicate the isolate is resistant to the antimicrobial. Patient's physician should be contacted and advised that effectiveness of this antimicrobial against the isolate cannot be judged by in vitro testing.
Organism's identification and susceptibility test results should be confirmed
Mycoplasmas are organisms without cell walls. Which antimicrobial agents would be ineffective in treating infections involving this bacterium? Tetracycline Aminoglycosides Penicillin Rifampin
Penicillin
What differentiates diagnostic techniques that employ phenotypic (culture-based) methods from those that employ molecular methods? - Phenotypic methods are highly sensitive and specific, while molecular methods are not. - Phenotypic methods examine the growth behavior of a microorganism and the proteins, enzymes, or toxins produced, while molecular methods examine the genetic makeup. - Phenotypic methods are quantitative while molecular methods are not. - Phenotypic methods are not limited to detection of live organisms as are molecular methods.
Phenotypic methods examine the growth behavior of a microorganism and the proteins, enzymes, or toxins produced, while molecular methods examine the genetic makeup
Daptomycin requires free calcium for its antibacterial action, is inhibited by pulmonary surfactant, and has activity against gram-positive bacteria. Gram-positive bacterial isolates can be tested for daptomycin susceptibility. For which type of infection should daptomycin susceptibility NOT be reported? Bacteremia Meningitis Pneumonia Skin/Soft tissue infection
Pneumonia
Which of the following molecular techniques, or combination of techniques, would be most appropriate for detection and quantitation of an RNA retrovirus, like HIV, in a blood sample in order to establish the patient's viral load? RT-PCR Real-time PCR Real-time RT-PCR Multiplex PCR
Real-time RT-PCR
A positive pyrrolidonyl arylamidase (PYR) test was observed on a species of Enterococcus. What color should be observed for this reaction? Purple Red Green Pink
Red
After PCR, the amplification control has failed to yield a product. What should you do? - Report out Indeterminate - Report out Negative because there was no amplification from the sample - Check the original DNA or RNA preparation. If it is adequate, repeat the amplification. If not, re-isolate the nucleic acid. - Repeat it using a higher concentration of amplification control in the reaction.
Repeat it using a higher concentration of amplification control in the reaction
After PCR, the amplification control has failed to yield a product. What should you do? Report out Indeterminate Report out Negative because there was no amplification from the sample Check the original DNA or RNA preparation. If it is adequate, repeat the amplification. If not, re-isolate the nucleic acid. Repeat it using a higher concentration of amplification control in the reaction.
Repeat it using a higher concentration of amplification control in the reaction
Of the following organisms, which can be described as a fastidious obligate intracellular parasite that multiplies by binary fission in the cytoplasm of host cells and infects humans as accidental hosts in most cases? Rickettsia Chlamydia Calymmatobacterium Coxiella
Rickettsia
A prokaryote that differs from most other bacteria with respect to its very small size and obligates intracellular parasitism is: Rickettsia. Bartonella. Calymmatobacterium. Coxiella.
Rickettsia.
Which category of media can be described as containing one or more agents that are inhibitory to all organisms except those being sought? Enrichment Supportive Selective Differential
Selective
In which category of media would MacConkey agar best fit? Selective Differential Selective and differential Supportive only
Selective and differential
Determining the exact nucleotide sequence of a gene or gene fragment obtained from an unknown organism is based on which of the following methods? Hybridization Sequencing Amplification (PCR) Genotypic
Sequencing
Gel electrophoresis is used to separate nucleic acid amplicons based upon what physical property? Sequence Duplex formation Size Secondary folding structure
Size
Caution should be taken when culturing blood in suspected cases of Mycoplasma infections since the organism is inhibited by which anticoagulant commonly found in commercial blood culture media? Ethylenediaminetetraacetic acid (EDTA) Sodium polyanethol sulfonate (SPS) Heparin Sodium citrate
Sodium polyanethol sulfonate (SPS)
AST was performed using Mueller-Hinton agar with 5% sheep blood, 35°C in 5% CO2 from 24 hours according to standard protocols, what is the most likely identity of the organism being tested? S. aureus Streptococcus pneumoniae Neisseria gonorrhoeae Moraxella catarrhalis
Streptococcus pneumoniae
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? Catalase is the inappropriate test to use on colonies of streptococci; therefore the results are invalid. The colony may have been contaminated with sheep red blood cells, causing a false-positive result. The colony was most likely enterococci, not streptococci. No discrepancy is present. Streptococcus is a catalase-positive colony.
The colony may have been contaminated with sheep red blood cells, causing a false-positive result
A sputum culture from a cystic fibrosis patient grew Stenotrophomonas maltophila. A broth microdilution panel was inoculated. Antimicrobials tested included: ceftazidime, imipenem, ticarcillin-clavulanate, levofloxacin, and trimethoprim-sulfamethoxazole. After 20-hour incubation at 35°C in ambient air, no growth was seen in any well of the microtiter plate. Which of the following statements is true? The isolate is susceptible to all antimicrobials tested. The microdilution plate was incubated under incorrect conditions. The test results are invalid and retesting would be recommended. A Cefinase test for β-lactamase activity should be done as an adjunct to MIC results.
The test results are invalid and retesting would be recommended
Quality control is set up to test urea agar. M. genitalium and M. hominis are used; however, both organisms are negative for urease activity. Which one of the following statements explains these findings? - The urea agar is most likely expired. - The incubation time is most likely abbreviated. - A technical error has occurred. - These two organisms are poor choices for quality control of urea agar.
These two organisms are poor choices for quality control of urea agar.
What key advantage do emerging technologies, such as MALDI-TOF and next generation sequencing, have over conventional hybridization and amplification techniques? They do not require selection of suspected pathogens prior to testing. They do not require expensive instrumentation or skilled technicians. They eliminate sample preparation steps, such as nucleic acid purification, prior to testing. They are readily available in most clinical laboratories. All of the above.
They do not require selection of suspected pathogens prior to testing
Incorporation of urea into media is used to enhance the detection of which organism? U. urealyticum M. pneumoniae M. hominis M. genitalium
U. urealyticum
Gen-Probe Mycobacterium tuberculosis direct test uses which type of nucleic acid amplification test? Nucleic acid sequence-based amplification (NASBA) Transcription-mediated amplification (TMA) Reverse transcriptase polymerase chain reaction (RT-PCR) Standard displacement amplification (SDA)
Transcription-mediated amplification (TMA)
Staphylococcus aureus was isolated from a patient's surgical wound. In a disk diffusion assay, the isolate was found to be resistant to cefoxitin (30 µg disk). With which antibiotic should this patient's infection be treated? Oxacillin Methicillin Vancomycin Cephalosporin
Vancomycin
The antibiotic nitrofurantoin is effective against both gram-positive and gram-negative bacteria. This antibiotic is effective against which type of specimen? Blood Cerebrospinal fluid (CSF) Sputum Urine
Urine
Antimicrobial agents that usually kill target organisms are said to be: bactericidal. antibiotic. bacteriostatic. antagonistic
bactericidal
Antimicrobial agents that inhibit bacterial growth but generally do not kill the organism are known as: bactericidal. antibiotic. bacteriostatic. antagonistic.
bacteriostatic.
Media that can be used for the isolation of Mycoplasma include: Thayer-Martin agar with vitamin K. 5% sheep blood and IsoVitaleX. beef or soybean protein with serum and fresh yeast extract. hemin and nicotinamide-adenine-dinucleotide (NAD) supplements.
beef or soybean protein with serum and fresh yeast extract.
Nucleic acid sequencing methods are based on: - the ability of two nucleic acid strands that have complementary base sequences to bond specifically with each other and form a double-stranded molecule. - detecting phenotypic traits not detectable by conventional strategies. - the principles of complementary nucleic acid hybridization with those of nucleic acid replication. - determining the exact nucleotide sequence of a gene or gene fragment obtained from an organism.
determining the exact nucleotide sequence of a gene or gene fragment obtained from an organism
MIC endpoints can be reported results obtained by the following conventional AST methods EXCEPT: agar dilution. automated broth dilution. disk Diffusion. E-test.
disk Diffusion
The drug of choice for the treatment of granuloma inguinale, which is a major cause of genital ulcers in India, New Guinea, and part of South America, is: clindamycin. doxycycline. imipenem. gentamycin.
doxycycline
An organism whose genetic makeup is 50% C-G bonds would have a(n) _________ melting temperature (Tm), compared with an organism with 20% C-G bonds. higher lower equal similar
higher
To read the hemolytic reaction accurately on a blood agar plate, the technologist must: hold the plate up to the light, and observe the plate with the light coming from behind. hold the plate under the light, and observe the plate with the light coming from the top. hold the plate over a white background. examine the plate using reflected and transmitted light.
hold the plate up to the light, and observe the plate with the light coming from behind.
Detection of the haze produced by some resistant staphylococci and enterococci against methicillin and vancomycin can best be accomplished by: - using fluorescent microscopy. - holding plate in front of reader and using transmitted light. - holding plate in front of reader and using reflected light. - placing plate on black background with a light directly above it.
holding plate in front of reader and using transmitted light.
Detection of the haze produced by some resistant staphylococci and enterococci against methicillin and vancomycin can best be accomplished by: using fluorescent microscopy. holding plate in front of reader and using transmitted light. holding plate in front of reader and using reflected light. placing plate on black background with a light directly above it.
holding plate in front of reader and using transmitted light.
The minimal bactericidal concentration (MBC) test: utilizes disks impregnated with series of concentrations (i.e., twofold dilutions) of each antimicrobial agent being tested against the bacterial isolate. will have an endpoint that is less than or equal to the MIC for each specific antimicrobial tested. is the antimicrobial concentration that yields a 99.9% reduction in CFU/mL, compared to concentration of the original bacterial inoculum. measures the ability of an antimicrobial to kill all bacteria in the endpoint MIC tube/well by planting an aliquot from it and incubating it overnight.
is the antimicrobial concentration that yields a 99.9% reduction in CFU/mL, compared to concentration of the original bacterial inoculum.
The role of the agar ingredient in culture medium is to: - provide a nutritional base for bacterial metabolism. - solidify the medium and provide a stable culture surface. - sterilize the medium and prevent contamination. - support the growth of only pathogenic organisms
solidify the medium and provide a stable culture surface
