Textbook of Diagnostic Microbiology 4th Edition – Test Bank

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Mahon: Textbook of Diagnostic Microbiology, 4th Edition

 

Chapter 05: Performance Improvement in the Microbiology Laboratory

 

Test Bank

 

MULTIPLE CHOICE

 

  1. Quality control is designed to:
a. Ensure the medical reliability of lab data
b. Check media
c. Check reagents
d. Monitor incubator and refrigerator temperatures

 

 

ANS:   A

Checking media, checking reagents, and monitoring incubator and refrigerator temperatures are all included in quality control. Each of these answers represents only a part of quality control, whereas the first answer encompasses all the activities one would do in a quality control program.

 

REF:    page 94           OBJ:    Level 1 – Recall

 

  1. Actual laboratory testing is called a(n):
a. Preanalytic activity
b. Analytic activity
c. Postanalytic activity
d. Research activity

 

 

ANS:   B

Preanalytic activity is what happens before a lab test is run. Postanalytic activity is what happens after a lab test is run. The analytic activity is the actual running of the laboratory test. Research is a term that applies to a series of focused experiments conducted to test a hypothesis.

 

REF:    page 94           OBJ:    Level 1 – Recall

 

  1. All of the following activities will directly affect the quality of a laboratory test EXCEPT:
a. Preanalytic
b. Analytic
c. Accreditation
d. Postanalytic

 

 

ANS:   C

Laboratory professionals have found that the preanalytic, analytic, and postanalytic activities directly affect the quality of a laboratory test. Accreditation is a peer review of the policies and procedures of a laboratory that may indirectly affect the quality of a laboratory test.

 

REF:    page 94           OBJ:    Level 1 – Recall

 

  1. In January 2004, The Joint Commission (TJC) implemented performance measurements for organizational systems that are critical to patient safety, quality of care, treatment, and services. This new initiative is called:
a. Performance improvement
b. Quality control
c. Quality assurance
d. Shared visions-new pathway

 

 

ANS:   D

Quality control consists of processes pertaining to the quality of analytic testing. Performance improvement is a process that consists of setting performance standards, measuring the standards again some criteria, then improving processes that fall short of the standards. Quality assurance is a comprehensive system that takes the preanalytic, analytic, and postanalytic processes into consideration when determining the quality of laboratory data. The new TJC initiative, Shared visions-new pathway, focuses on performance measurement of organizational systems that are critical to patient safety, quality of care, treatment, and services.

 

REF:    page 94           OBJ:    Level 1 – Recall

 

  1. All of the following activities are included in a laboratory quality control program EXCEPT:
a. Air quality
b. Temperatures
c. Media
d. Antimicrobial susceptibility testing

 

 

ANS:   A

The air quality in a laboratory is not routinely tested. A quality control program focuses on procedures, equipment, and policies that affect how well laboratory tests are performed, the quality of submitted specimens, and test results.

 

REF:    pages 95-100                                      OBJ:    Level 1 – Recall

 

  1. The morning tech arrives at the microbiology laboratory and goes around checking daily temperatures. This person will check temperatures daily on all of the following temperature-dependent equipment EXCEPT:
a. Centrifuges
b. Incubators
c. Heating blocks
d. Refrigerators

 

 

ANS:   A

A centrifuge is not typically a temperature-dependent piece of equipment.

 

REF:    page 95           OBJ:    Level 2 – Interpretation

 

  1. Thermometers used in the laboratory must be calibrated before they are put into use. This is accomplished by:
a. Sending to the National Institute of Standards and Technology (NIST) to determine its accuracy
b. Checking against an NIST thermometer
c. Measuring the grades to make sure they are the standard size and accuracy
d. Using a colored dye

 

 

ANS:   B

A thermometer calibration is conducted by comparison of the NIST thermometer reading to the laboratory thermometer’s reading. Any variation is noted on the certificate of calibration.

 

REF:    page 95           OBJ:    Level 1 – Recall

 

  1. Preventive maintenance on an instrument includes all the following EXCEPT:
a. Disinfecting the surface of the instrument
b. Oiling and cleaning the instrument
c. Replacing filters
d. Recalibrating instruments

 

 

ANS:   A

Disinfecting the surface of an instrument is usually done as a daily activity and is generally not considered preventive maintenance. All the other choices are preventive maintenance activities that will keep an instrument in top shape and functioning at the proper level so as to increase its lifetime and keep it producing quality results.

 

REF:    page 95           OBJ:    Level 1 – Recall

 

  1. Commercial media must have quality control testing performed by the manufacturer. Because of high failure rates, all of the following media must be retested by the hospital laboratory EXCEPT:
a. Campylobacter media
b. Selective media for pathogenic Neisseria
c. Trypticase soy agar with 5% sheep blood
d. Chocolate

 

 

ANS:   C

Trypticase soy agar with 5% sheep blood does not have a high failure rate, so the hospital laboratory need not retest it.

 

REF:    pages 96-97     OBJ:    Level 1 – Recall

 

  1. Media that do not need to be retested by the hospital laboratory must still undergo observation for all of the following EXCEPT:
a. Moisture
b. Sterility
c. Breakage
d. Organism colony characteristics

 

 

ANS:   D

When a laboratory is not required to retest prepared media, it still must observe media for moisture, sterility, breakage, and appearance. Results of media observation must be recorded and must include lot numbers.

 

REF:    page 97           OBJ:    Level 1 – Recall

 

  1. When a medium needs to be quality controlled because it was prepared in-house or because it is complex, all the following rules must be followed EXCEPT:
a. Only media not specified in Clinical and Laboratory Standards Institute (CLSI) guidelines should be tested.
b. The medium should be tested for sterility and pH.
c. The organism selected for quality control testing should represent most fastidious organisms for which the medium is designed.
d. Testing techniques should be different for primary plating media than for biochemical or subculturing media.

 

 

ANS:   A

All in-house media must be tested for pH, sterility, and positive and negative reacting organisms—that is, if a medium should inhibit a specific organism or group of organisms, it should be tested with those organisms to ensure it “works.” CLSI guidelines give specific guidance as to what type of quality control testing should be performed on media prepared in-house.

 

REF:    page 97           OBJ:    Level 1 – Recall

 

  1. Reagents that should undergo quality control in the microbiology laboratory include all the following EXCEPT:
a. Optochin
b. Immersion Oil
c. b-Lactamase
d. Nitrate

 

 

ANS:   B

All stains performed in a microbiology laboratory along with Optochin, b-lactamase, nitrate, bacitracin, catalase, coagulation, gelatin, germ tube, hippurate, Kovac’s, oxidase, PYR, typing sera, Voges-Proskauer, and X & V strips should undergo quality control testing in a microbiology laboratory. Immersion oil does not need QC testing.

 

REF:    pages 97-98     OBJ:    Level 1 – Recall

 

  1. Antimicrobial susceptibility is hard to control because many of the same species of organisms have a varied susceptibility to particular antibiotics. To reduce this variation, Clinical and Laboratory Standards Institute (CLSI) guidelines recommend the following:
a. Use in-house organisms isolated from past patients
b. Share strains between hospital laboratories
c. Use specific strains from American Type Culture Collection (ATCC)
d. Obtain test strains from Centers for Disease Control and Prevention (CDC)

 

 

ANS:   C

Specific ATCC strains of control organisms are recommended by CLSI. There is too much variation in organisms isolated from patients to use as quality control organisms. Hospital laboratories trying to share strains would find this a cumbersome process for routine quality control. CDC does not store routine strains of microbes for quality control testing.

 

REF:    page 98           OBJ:    Level 1 – Recall

 

  1. In any susceptibility system, variables that can affect the results include the following:
  2. Antibiotic potency
  3. Inoculum concentration
  4. Bactericidal level
  5. pH
  6. Anion content
a. 1, 2, and 3 are correct
b. 1, 3, 4, and 5 are correct
c. 1, 2, 3, 4, and 5 are correct
d. 1, 2, and 4 are correct

 

 

ANS:   D

The factors affecting results include antibiotic potency, inoculum, concentration, and pH. The bactericidal level of antibiotic and anion content does not affect susceptibility results. Other factors affecting results include agar depth, evaporation, cation content, thymidine content, instrument failure, temperature, moisture, and difficulty in determining endpoints.

 

REF:    pages 98,100                                      OBJ:    Level 2 – Interpretation

 

  1. Susceptibility testing of control organisms is usually conducted daily until precision can be demonstrated with _____ or _____ _____ days of susceptibility testing using Clinical and Laboratory Standards Institute (CLSI) guidelines.
a. 20, 30, consecutive
b. 15, 20, consecutive
c. 30, 40, nonconsecutive
d. 5, 10, consistent

 

 

ANS:   A

Once the 20- or 30-day evaluation has been accomplished, quality control organisms may be tested weekly instead of daily. All results should be kept as long as the antimicrobial agent is used or at least 2 years after discontinuing the agent.

 

REF:    page 100         OBJ:    Level 1 – Recall

 

  1. How can personnel competency be determined?
a. Asking an employee to explain how to do a test
b. Proficiency testing
c. Asking another employee to comment on someone’s competency
d. Assuming competency from one’s credentials

 

 

ANS:   B

Proficiency testing consists of carefully designing samples and giving them to techs as unknowns for the purpose of identifying them. This will show how competent a tech is at performing job tasks. Asking an employee how to do a test is not the same as having someone perform the test. Doing a test involves motor skills and coordination that cannot be measured by asking a person about how to do a test. Two things that are never done to evaluate a person’s competency are asking another employee to comment on someone’s competency and assuming one is competent from his or her credentials.

 

REF:    page 100         OBJ:    Level 1 – Recall

 

  1. The following are provisions of CLIA 88 EXCEPT:
a. Verify employee competency upon employment.
b. Determine an employee’s competency.
c. Reverify the employee’s competency monthly.
d. Reverify the employee’s competency annually.

 

 

ANS:   C

To maintain quality in the laboratory, CLIA 88 mandated that an employee’s competency must be verified upon employment, an employer must determine an employee’s competency, and the employee’s competency must be reverified annually. It did not mandate reverifying an employee’s competency monthly because this would be an impossible task—the time frame is too short.

 

REF:    page 100         OBJ:    Level 1 – Recall

 

  1. Quality control stock cultures are available from all of the following EXCEPT:
a. American Type Culture Collection (ATCC)
b. Commercial sources
c. Proficiency testing isolates
d. Centers for Disease Control and Prevention (CDC)

 

 

ANS:   D

CDC is a clearinghouse for knowledge concerning infectious diseases, but CDC does not provide stock cultures to hospital laboratories.

 

REF:    page 100         OBJ:    Level 1 – Recall

 

  1. Popular media choices for maintaining stock cultures include:
a. TSA deeps
b. Cornmeal
c. Sabouraud dextrose
d. CTA with glucose

 

 

ANS:   A

For best results, a stock culture should be grown in a large volume of broth, then divided among enough small freezer vials to last a year. Media selection for freezing is at the discretion of individual laboratory, but it should not contain sugars. If organisms use sugars while being maintained, acid by-products could kill the organism over time. CTA, Sabouraud dextrose, and cornmeal all have sugar. TSA deeps is the only choice that is sugar-free.

 

REF:    page 100         OBJ:    Level 1 – Recall

 

  1. Which of the following is an example of a mission statement for an institution?
a. “The AFMS Flagship—Comprehensive Healthcare…On Time…On Target”
b. “Working Together for a Healthy America”
c. “Your Total eLearning Solution”
d. “Will Answer Questions Correctly 95% of the Time”

 

 

ANS:   B

An organization’s vision and mission statements must be clearly emphasized so that all employees become involved and understand that each one of them has a role in the mission, and that they must strive to make performance improvement part of their everyday life to achieve the organization’s mission. Answers a and c are vision statements, whereas d is an objective.

 

REF:    page 102         OBJ:    Level 2 – Interpretation

 

  1. All the following are components of JCAHO recommendations for establishing performance monitors EXCEPT:
a. Plan
b. Design
c. Do
d. Assess

 

 

ANS:   C

The components of the recommendations are plan, design, measure, and assess.

 

REF:    page 102         OBJ:    Level 1 – Recall

 

  1. Customers of a laboratory include all the following EXCEPT:
a. Patients
b. Insurers
c. Doctors
d. Accrediting organizations

 

 

ANS:   D

Anyone who looks to the laboratory for service is a customer. Doctors, nurses, insurers, and patients are all customers. Accrediting organizations are not expecting services from a laboratory, so they cannot be considered a customer.

 

REF:    page 102         OBJ:    Level 1 – Recall

 

  1. An unlabeled specimen is sent from the intensive care unit to the laboratory. When the specimen arrives in the laboratory, the laboratory manager decides that correct action needs to occur. What can be constructed to evaluate and correct the problem?
a. Find fault with the nurse causing the problem.
b. Provide training for the nurse responsible for the problem.
c. Empower a facilitator.
d. Make a cross-functional team.

 

 

ANS:   D

When patient outcome is less than desirable, the process must be evaluated and corrected. The focus is on the process, not the individual. The primary rule to follow is to refrain from finger pointing or fault finding. Preanalytic and postanalytic activities usually take place outside the laboratory and require a cross-functional team to evaluate and correct the problem.

 

REF:    page 103         OBJ:    Level 3 – Synthesis

 

  1. When is a broken process fixed?
a. When the problem is prevented from happening again.
b. When everyone is happy with the process.
c. When the process becomes seamless.
d. When the hospital administrator determines that the cross-functional team is no longer needed.

 

 

ANS:   A

A process is not fixed just because the reason something went wrong is explained. It is fixed only when the problem is prevented from happening again.

 

REF:    page 103         OBJ:    Level 1 – Recall

 

  1. What is benchmarking?
a. Identifying a problem to be fixed
b. Seeking an industry’s or profession’s best practices to imitate and improve
c. Explaining why a problem occurred
d. Asking the CEO’s opinion and going with his or her idea

 

 

ANS:   B

Benchmarking is seeking an industry’s or profession’s best practice to imitate and improve. Benchmarking was initially practiced in business and industry, but it has now become an important part of the hospital quality management program.

 

REF:    page 103         OBJ:    Level 1 – Recall

 

  1. When performing tests in the microbiology laboratory, the detection limit of a test refers to the _____ of that test.
a. Analytic specificity
b. Analytic sensitivity
c. Clinical sensitivity
d. Clinical specificity

 

 

ANS:   B

The analytic sensitivity of a test refers to its ability to detect a particular analyte or a small change in its concentration. Analytic sensitivity is usually defined as the 0.95 confidence level (+/– 2 SD) and may be referred to as the detection limit. Analytic specificity is a test’s ability not to react with substances other than the one of interest. Clinical sensitivity is the proportion of specimens that test positive from people who are known to have the disease. Clinical specificity is the population of specimens that test negative from people who are known to be disease free.

 

REF:    page 105         OBJ:    Level 1 – Recall

 

  1. A technician is performing a chemistry test on a control sample. The technician gets the following values for the control: 4.3, 4.3, 4.3, 4.2, 4.4, 4.3, 4.2, and 4.4. The actual value is 4.3. These results are said to be:
a. Systematically inaccurate
b. Sensitive
c. Accurate
d. Bias

 

 

ANS:   C

The degree of conformity of a measurement to a standard or true value is accuracy. Bias is the mean difference of test results from an accepted reference method caused by systematic errors.

 

REF:    pages 105-106                                    OBJ:    Level 3 – Synthesis

 

  1. A test is performed on a group of 10 patients. Six patients have a disease, and four are free of the disease. If six patients (all known to have the disease) of this group test positive for the disease, we say that the clinical sensitivity of this test is:
a. 60%
b. 40%
c. 50%
d. 100%

 

 

ANS:   D

Clinical sensitivity is the proportion of positive test results obtained when a test is applied to patients known to have the disease. Thus it is the frequency of positive test results in patients with the disease. If six patients in our group are known to have the disease and all six test positive, then the clinical sensitivity of the test is 100%.

 

REF:    page 106         OBJ:    Level 3 – Synthesis

 

  1. A group of 10 patients are to be tested: six are known to have a disease and four are disease free. If the four disease-free patients tested negative for this disease, what would the clinical specificity of this test be?
a. 100%
b. 60%
c. 40%
d. 50%

 

 

ANS:   A

Clinical specificity is the proportion of negative results obtained when a test is applied to patients known to be free of disease. Thus it is the frequency of negative test results in patients without the disease. So if there are four patients in this group and they all test negative with this test, then the clinical specificity is 100%—all negative individuals tested negative with this test.

 

REF:    page 106         OBJ:    Level 3 – Synthesis

 

  1. Incidence is:
a. The frequency of a disease at a designated single point in time in the population being tested
b. The number of new cases of disease over a period of time
c. Proportion of negative test results in a population known to be free of disease
d. Positive results in patients with the disease

 

 

ANS:   B

Incidence is defined as the number of new cases of disease over a period of time. Prevalence is the frequency of a disease at a designated single point in time in the population being tested. Clinical specificity is the proportion of negative test results in a population known to be free of the disease. Clinical sensitivity is the positive results in patients with the disease.

 

REF:    page 106         OBJ:    Level 1 – Recall

 

  1. A test can have both a positive and negative predictive value. All the following elements are needed to compute the positive and negative predictive value of a test EXCEPT:
a. Sensitivity of a test
b. Specificity of a test
c. Incidence of the disease being tested
d. Prevalence of the disease being tested

 

 

ANS:   C

The predictive value of a test is the probability that a positive result (positive predictive value) accurately indicates the presence of an analyte or a specific disease. The formula is:

where PPV = positive predictive value

P = prevalence of disease being tested

Se = sensitivity of test

Sp = specificity of test

 

REF:    page 107         OBJ:    Level 1 – Recall

 

  1. Assume that a certain test for group A Streptococcus has reported sensitivity and specificity of 90% and 98%, respectively, and the estimated prevalence for group A Streptococcus infection in acute pharyngitis is 5%. What is the positive predictive value of this test?
a. 99.5%
b. 30%
c. 90%
d. 70.3%

 

 

ANS:   D

where PPV = positive predictive value

P = prevalence of disease being tested

Se = sensitivity of test

Sp = specificity of test

 

REF:    page 107         OBJ:    Level 3 – Synthesis

 

  1. Usually, negative test results are more reliable in predicting:
a. The absence of disease
b. The presence of disease
c. The sensitivity of a test
d. The specificity of a test

 

 

ANS:   A

Usually, with tests, the negative predictive value (NPV) is higher than the positive predictive value (PPV). This shows that tests can more accurately predict the absence of disease. The sensitivity and specificity of a test do not predict the presence or absence of a disease.

 

REF:    page 107         OBJ:    Level 1 – Recall

 

  1. The efficiency of a test indicates:
a. The percentage of patients who test positive for the disease
b. The percentage of patients who are correctly identified as having or not having the disease
c. The percentage of patients who test negative for the disease
d. The number of patients tested for a disease

 

 

ANS:   B

Test efficiency =

TP = number of patients with true positive

TN = number of patients with true negative

FP = number of patients with false positive

FN = number of patients with false negative

 

REF:    page 108         OBJ:    Level 1 – Recall

 

  1. Screening is:
a. Used for only particular test analytes
b. Not practical in a hospital laboratory
c. Used for testing large populations of patients
d. When a high incidence of a disease is found in a population

 

 

ANS:   C

Screening is used for testing large populations of patients. Generally, screening tests have high clinical sensitivity and negative predictive value. Positive results with such tests generally require confirmation with a more specific test.

 

REF:    page 108         OBJ:    Level 1 – Recall

 

  1. Confirmation is used after:
a. Careful consideration by the doctor to do the test
b. A test that has a low predictive value
c. A test that has a low specificity
d. Obtaining a positive screening result

 

 

ANS:   D

Confirmation is the process of repeating a screening test using a test that is more sensitive and specific to ensure accuracy for the initial screening result. Confirmatory tests help seek out false-positive screening tests.

 

REF:    page 108         OBJ:    Level 1 – Recall

 

  1. When choosing a test to perform in your laboratory, an in-house verification is always performed. Verification of a test:
a. Serves to establish that the performance parameters of the test are satisfactory
b. Lets techs actually perform the test
c. Lets physicians perform the test
d. Allows laboratory management to view positive results

 

 

ANS:   A

A test must be verified by a laboratory to ensure that it will work as described on the package. A test must perform up to specifications in a lab or it is not worth using. Although having techs perform the test in-house shortens the turnaround time for results, the test is evaluated for its performance. Physicians are not allowed to perform tests in a clinical laboratory. Laboratory management does not need to see positive test results. Laboratory management will evaluate the test on its in-house performance.

 

REF:    page 109         OBJ:    Level 1 – Recall

 

  1. Test validation is the ongoing process providing information that a test is performing correctly. The components of validation include all the following EXCEPT:
a. Quality control
b. Specimen requirements
c. Proficiency testing
d. Instrument calibration

 

 

ANS:   B

Specimen requirements do not assess the functioning of a test. Quality control, proficiency testing, and instrument calibration evaluate test functioning on a continual basis.

 

REF:    pages 109-110                                    OBJ:    Level 1 – Recall

 

  1. All of the following provide guidelines to ensure the continual correct performance of tests EXCEPT:
a. Accrediting agencies
b. Regulatory agencies
c. Centers for Disease Control and Prevention (CDC)
d. Manufacturers

 

 

ANS:   C

CDC does not publish recommendations in regard to continual test validation. CDC is a clearinghouse for infectious disease knowledge.

 

REF:    pages 109-110                                    OBJ:    Level 1 – Recall

 

 

 

 

Mahon: Textbook of Diagnostic Microbiology, 4th Edition

 

Chapter 28: Diagnostic Parasitology

 

Test Bank

 

MULTIPLE CHOICE

 

  1. Identify the following:

(Courtesy CDC Public Health Image Library (PHIL); http://phil.cdc.gov/phil/home.asp.)

a. Ascaris lumbricoides
b. Strongyloides stercoralis
c. Hookworm
d. Schistosoma haematobium

 

 

ANS:   A

The usual diagnostic stage is the egg. Fertile Ascaris eggs are oval, measure 45 to 75 by 35 to 50 mm, and have thick hyaline walls surrounding a one-cell-stage embryo. Most eggs have a brown, bile-stained mammillated outer layer. CDC PHIL #10584

 

REF:    page 694         OBJ:    Level 3 – Synthesis

 

  1. Identify the following:

(Courtesy CDC Public Health Image Library (PHIL); http://phil.cdc.gov/phil/home.asp.)

a. Plasmodium ovale
b. Babesia microti
c. Plasmodium malariae
d. Trypanosoma cruzi

 

 

ANS:   B

The diagnosis of babesiosis is made from a Wright- or Giemsa-stained thin blood smear. The organisms appear as small, delicate, ring-form trophozoites, about 1 to 2 mm, with a prominent chromatin dot and faintly staining cytoplasm. More mature trophozoites may appear as pyriform organisms in single, double, or the classic tetrad (Maltese cross) formation within the red blood cells. CDC PHIL #5944

 

REF:    page 674         OBJ:    Level 3 – Synthesis

 

  1. Identify the following:

(Courtesy CDC Public Health Image Library (PHIL); http://phil.cdc.gov/phil/home.asp.)

a. Brugia malayi
b. Loa loa
c. Wucheria bancrofti
d. Onchocerca volvulus

 

 

ANS:   C

Diagnosis of W. bancrofti should include the examination of a blood specimen obtained at night (10 p.m. to 2 a.m.) for the presence of microfilariae. The blood may be examined immediately for live microfilariae. If examined on a Wright-stained smear, the microfilariae of W. bancrofti are sheathed, and the nuclei do not extend to the tip of the tail. CDC PHIL # 3010

 

REF:    page 699         OBJ:    Level 3 – Synthesis

 

  1. Identify the following:

(Courtesy CDC Public Health Image Library (PHIL); http://phil.cdc.gov/phil/home.asp.)

a. Schistosoma mansoni
b. Opisthorchis sinensis
c. Fasciola hepatica
d. Heterophyes heterophyes

 

 

ANS:   B

The diagnosis is made by finding the egg in a stool specimen or, occasionally, in duodenal aspirates. Adults are thin, tapered at both ends, and 1 to 2.5 cm long. The egg is 29 to 35 mm long, embryonated when passed, flash shaped, and operculated with prominent shoulders at the operculum and a knob at the opposite end. CDC PHIL # 5248

 

REF:    page 682         OBJ:    Level 3 – Synthesis

 

  1. Identify the following:

(Courtesy CDC Public Health Image Library (PHIL); http://phil.cdc.gov/phil/home.asp.)

a. Leishmania donovani
b. Babesia microti
c. Plasmodium falciparum
d. Trypanosoma cruzi

 

 

ANS:   D

The primary diagnostic stage in the blood is the trypomastigote. It is an elongated structure 15 to 20 mm long that often appears in a C or U shape. Like the other trypomastigotes, it shows a single large nucleus midbody and a posterior kinetoplast to which is attached the undulating membrane. The morphology of all trypomastigotes is similar; therefore a complete patient history is necessary to determine the species present. CDC PHIL #3013

 

REF:    page 666         OBJ:    Level 3 – Synthesis

 

  1. Identify the following:

(Courtesy CDC Public Health Image Library (PHIL); http://phil.cdc.gov/phil/home.asp.)

a. Cryptosporidium parvum
b. Isospora belli
c. Cyclospora cayetanensis
d. Encephalitozoon intestinalis

 

 

ANS:   A

The recommended detection methods when Cryptosporidium infection is suspected are the modified Ziehl-Nielsen acid-fast stain and an immunofluorescent antibody test using a monoclonal antibody directed against Cryptosporidium. With the acid-fast stain, the organism stains as a bright red sphere that distinguishes it from yeasts, which stain green. CDC PHIL #5242

 

REF:    page 678         OBJ:    Level 3 – Synthesis

 

  1. Identify the following:

(Courtesy CDC Public Health Image Library (PHIL); http://phil.cdc.gov/phil/home.asp.)

a. Hymenolepis nana
b. Taenia saginata
c. Diphyllobothrium latum
d. Taenia solium

 

 

ANS:   C

The scolex, proglottid, or egg are diagnostic findings in a fecal specimen. The egg is unembryonated when passed, operculated, and yellow-brown. It is about 58 to 76 mm by 40 to 50 mm and has a small, knoblike protuberance at the end opposite the operculum. The knob may not be seen on all eggs, so size and lack of shoulders must be used to distinguish the egg from that of Paragonimus westermani. CDC PHIL # 1541

 

REF:    page 687         OBJ:    Level 3 – Synthesis

 

  1. Identify the following:

(Courtesy CDC Public Health Image Library (PHIL); http://phil.cdc.gov/phil/home.asp.)

a. Entamoeba histolytica/E. dispar
b. E. hartmanni
c. Giardia lamblia
d. E. coli

 

 

ANS:   A

The average size of the E. histolytica/dispar cyst is 10 to 20 mm. Cysts of the organism may have one to four nuclei each with a small central karyosome and fine, evenly distributed peripheral chromatin. The cytoplasm may contain cigar-shaped chromatoidal bars with rounded ends. These bars are composed of ribonucleic acid. CDC PHIL #7831

 

REF:    page 654         OBJ:    Level 3 – Synthesis

 

  1. Identify the following:

(Courtesy CDC Public Health Image Library (PHIL); http://phil.cdc.gov/phil/home.asp.)

a. Trichuris trichiura
b. Enterobius vermicularis
c. Ascaris lumbricoides
d. Hookworm

 

 

ANS:   B

The adult Enterobius vermicularis female measures 8 to 13 mm long and has a long, pointed tail and three cuticle lips with alae at the anterior end. The egg is oval, colorless, and slightly flattened on one side. It measures approximately 50 to 60 mm by 20 to 30 mm. The egg is usually seen embryonated and containing a C-shaped larvae. CDC PHIL #5229

 

REF:    page 692         OBJ:    Level 3 – Synthesis

 

  1. Identify the following:

(Courtesy CDC Public Health Image Library (PHIL); http://phil.cdc.gov/phil/home.asp.)

a. Plasmodium ovale
b. P. malariae
c. P. falciparum
d. P. vivax

 

 

ANS:   C

The ring forms of P. falciparum are more delicate than those of other species and often have two chromatin dots. Applique forms, parasites on the edge of the red blood cells (RBC), and multiple ring forms in a single RBC are common. The mature trophozoite is small and compact and may have dark brown pigment. The schizont has 8 to 36 merozoites, with an average of 20 to 24. Gametocytes have a characteristic banana or crescent shape. CDC PHIL # 5941

 

REF:    page 673         OBJ:    Level 3 – Synthesis

 

  1. Identify the following:

(Courtesy CDC Public Health Image Library (PHIL); http://phil.cdc.gov/phil/home.asp.)

a. Wucheria bancrofti
b. Brugia malayi
c. Loa loa
d. Fasciola hepatica

 

 

ANS:   D

The unembryonated and operculated eggs of Fasciola hepatica are carried in the bile to the intestinal tract and are passed in the feces. The size range is 130 to 150 mm by 60 to 90 mm. They are virtually indistinguishable from eggs of F. buski. CDC PHIL #4846

 

REF:    page 682         OBJ:    Level 3 – Synthesis

 

  1. Identify the following:

(Courtesy CDC Public Health Image Library (PHIL); http://phil.cdc.gov/phil/home.asp.)

a. Plasmodium ovale
b. P. vivax
c. P. falciparum
d. P. malariae

 

 

ANS:   D

The trophozoite of P. malariae is compact and may assume a characteristic “band” appearance, in which it stretches across the diameter of the red blood cells (RBCs). Dark, coarse brown-black pigment is present. Occasionally, a few pink cytoplasmic dots, called Ziemann’s dots, may be seen. The mature schizont contains 6 to 12 merozoites with an average of 8. Merozoites may be arranged in a characteristic loose daisy petal arrangement around the clumped pigment. CDC PHIL # 5130

 

REF:    page 672         OBJ:    Level 3 – Synthesis

 

  1. Identify the following:

(Courtesy CDC Public Health Image Library (PHIL); http://phil.cdc.gov/phil/home.asp.)

a. Schistosoma mansoni
b. S. japonicum
c. S. haematobium
d. S. madurella

 

 

ANS:   C

Diagnosis is made by finding embryonated eggs in the feces of S. mansoni and S. japonicum or in the urine (S. haematobium). S. haematobium eggs are elongated and 110 to 170 mm by 40 to 70 mm, and have a terminal spine. The best time to collect the eggs in urinary schistosomiasis is during peak excretion time in early afternoon (12 p.m. to 2 p.m.). CDC PHIL # 4843

 

REF:    page 685         OBJ:    Level 3 – Synthesis

 

  1. Identify the following:

(Courtesy CDC Public Health Image Library (PHIL); http://phil.cdc.gov/phil/home.asp.)

a. Schistosoma mansoni
b. S. japonicum
c. S. haematobium
d. S. madurella

 

 

ANS:   B

  1. japonicum eggs are round and 60 to 95 mm by 40 to 60 mm; they have a small, curved, rudimentary spine. CDC PHIL # 4842

 

REF:    page 685         OBJ:    Level 3 – Synthesis

 

  1. Identify the following:

(Courtesy CDC Public Health Image Library (PHIL); http://phil.cdc.gov/phil/home.asp.)

a. Schistosoma mansoni
b. S. japonicum
c. S. haematobium
d. S. madurella

 

 

ANS:   A

The egg of S. mansoni is yellowish, elongated and 115 to 175 mm by 45 to 75 mm, and has a prominent lateral spine. CDC PHIL # 4841

 

REF:    page 685         OBJ:    Level 3 – Synthesis

 

  1. Identify the following:

(Courtesy CDC Public Health Image Library (PHIL); http://phil.cdc.gov/phil/home.asp.)

a. Hymenolepis nana
b. Taenia spp.
c. Diphyllobothrium latum
d. Paragonimus westermani

 

 

ANS:   B

Laboratory diagnosis of Taenia spp. infection can be made by finding the egg, scolex, or proglottid in the feces. The egg is yellow-brown and surrounded by a thick wall with radial striations; it measures 30 to 43 mm. The egg is embryonated with a six-hook oncosphere when passed in the feces. Eggs of this species are indistinguishable and must be reported as “Taenia spp.” eggs. CDC PHIL #4832

 

REF:    page 688         OBJ:    Level 3 – Synthesis

 

  1. Identify the following:

(Courtesy CDC Public Health Image Library (PHIL); http://phil.cdc.gov/phil/home.asp.)

a. Leishmania donovani
b. Wucheria bancrofti
c. Trichinella spiralis
d. Loa loa

 

 

ANS:   C

Because it is difficult to recover adults or larvae in a stool sample, the diagnosis is often based on clinical symptoms and the patient’s history. Biopsy of muscle tissue and identification of encapsulated, coiled larva is the definitive diagnostic method. CDC PHIL #10142

 

REF:    page 697         OBJ:    Level 3 – Synthesis

 

  1. Identify the following:

(Courtesy CDC Public Health Image Library (PHIL); http://phil.cdc.gov/phil/home.asp.)

a. Trypanosoma spp.
b. Leishmania spp.
c. Wucheria bancrofti
d. Loa loa

 

 

ANS:   A

The diagnostic stage of trypanosomes in humans is the trypomastigote, which is usually seen in a Wright-stained blood smear. The trypomastigote is 15 to 20 mm with a single large nucleus and a posterior kinetoplast to which is attached the flagellum of the undulating membrane. Trypanosoma spp. cannot be differentiated on a blood smear; therefore the organism is reported as Trypanosoma spp. CDC PHIL #3017

 

REF:    page 666         OBJ:    Level 3 – Synthesis

 

  1. Identify the following:

(Courtesy CDC Public Health Image Library (PHIL); http://phil.cdc.gov/phil/home.asp.)

a. Plasmodium malariae
b. P. ovale
c. P. falciparum
d. P. vivax

 

 

ANS:   D

A fine pink stippling known as Schüffner’s stippling may be present in the cell. The young trophozoite of P. vivax is characterized by its amoeboid appearance; by maturity, it usually fills the red blood cell, and golden brown malarial pigment is present. The mature schizont contains 12 to 24 merozoites, with an average of 16. Gametocytes are rounded and fill the cell. Macrogametocytes are often difficult to differentiate from mature trophozoites. CDC PHIL #5927

 

REF:    page 672         OBJ:    Level 3 – Synthesis

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