Quiz Answers
- Each of the following parasites is transmitted by eating inadequately cooked fish or seafood EXCEPT:
- a. Clonorchis sinensis
- b. Ancylostoma duodenale ✅
- c. Paragonimus westermani
- d. Diphyllobothrium latum
- Each of the following parasites is transmitted by eating inadequately cooked fish or seafood EXCEPT:
- a. Clonorchis sinensis
- b. Ancylostoma duodenale
- c. Paragonimus westermani ✅
- d. Diphyllobothrium latum
- Each of the following statements concerning neisseriae is correct EXCEPT:
- a. They produce IgA protease as a virulence factor.
- b. They are oxidase-positive.
- c. They are gram-negative diplococci.
- d. They grow best under anaerobic conditions. ✅
- Several pathogens are transmitted either during gestation or at birth. Which one of the following is LEAST likely to be transmitted at these times?
- a. Haemophilus influenzae ✅
- b. Treponema pallidum
- c. Neisseria gonorrhoeae
- d. Chlamydia trachomatis
- A 30-year-old woman with systemic lupus erythematosus is found to have a positive serologic test for syphilis (VDRL test). She denies having had sexual contact with a partner who had symptoms of a venereal disease. The next best step would be to:
- a. Perform a fluorescent treponemal antibody-absorbed (FTA-ABS) test on a specimen of her serum ✅
- b. Reassure her that the test is a false-positive reaction related to her autoimmune disorder
- c. Trace her sexual contacts for serologic testing
- d. Treat her with penicillin
- Each of the following is associated with the Lancefield group B streptococci (S. agalactiae) EXCEPT:
- a. Vaginal carriage in 5% to 25% of normal women of childbearing age
- b. Neonatal sepsis and meningitis
- c. Pyoderma (impetigo) ✅
- d. Beta-hemolysis
- Each of the following statements concerning gonorrhea is correct EXCEPT:
- a. Gonococcal conjunctivitis of the newborn rarely occurs in the United States, because silver nitrate or erythromycin is commonly used as prophylaxis.
- b. A presumptive diagnosis can be made by finding gram-negative kidney bean-shaped diplococci within neutrophils in a urethral discharge.
- c. Infection in men is more frequently symptomatic than in women.
- d. The definitive diagnosis can be made by detecting antibodies to Neisseria gonorrhoeae in the patient’s serum. ✅
- Each of the following statements concerning chlamydial genital tract infections is correct EXCEPT:
- a. There is no vaccine against these infections.
- b. Infection can persist after administration of penicillin.
- c. Symptomatic infections can be associated with urethral or cervical discharge containing many polymorphonuclear leukocytes.
- d. Infection can be diagnosed by finding antichlamydial antibody in a serum specimen. ✅
- Each of the following statements concerning Actinomyces and Nocardia is correct EXCEPT:
- a. A. israelii is an anaerobic rod found as part of the normal flora in the mouth.
- b. Infections are usually diagnosed by detecting a significant rise in antibody titer. ✅
- c. Both Actinomyces and Nocardia are branching, filamentous rods.
- d. N. asteroides causes infections primarily in immunocompromised patients.
- Each of the following statements concerning the fluorescent treponemal antibody-absorbed (FTA-ABS) test for syphilis is correct EXCEPT:
- a. The patient’s serum is absorbed with saprophytic treponemes.
- b. The test is rarely positive in primary syphilis. ✅
- c. Once positive, the test remains so despite appropriate therapy.
- d. The test is specific for Treponema pallidum.
- Regarding Chlamydiae, which one of the following is MOST accurate?
- a. They replicate in the nucleus of infected cells, where they form inclusions that are useful diagnostically.
- b. Their life cycle consists of a metabolically inactive particle in the extracellular phase. ✅
- c. They exhibit swarming motility on a blood agar plate.
- d. They are gram-positive rods that do not form spores.
- e. They can replicate only within cells because they lack the ability to produce certain essential mRNAs.
- Regarding human papillomavirus (HPV), which one of the following is MOST accurate?
- a. HPV induces the formation of koilocytes in the skin that are an important diagnostic feature of HPV infection. ✅
- b. Amantadine is a chain-terminating drug that inhibits HPV replication by blocking DNA synthesis.
- c. HPV is an enveloped virus with a genome composed of double-stranded RNA.
- d. The P2 capsid protein of HPV activates the c-sarc oncogene in human cells, which is the process by which HPV predisposes to malignancy.
- e. Blood and blood products are an important mode of transmission of HPV.
- A 30-year-old woman presents to her gynecologist with complaints of vaginal itching and a frothy, yellow discharge. She also complains of painful urination. She admits to being sexually active with several men in the past two weeks. Cultures are negative for bacterial growth, but organisms are visible via a wet preparation on low power. The most likely causal agent is
- a. Trichomonas vaginalis ✅
- b. Candida albicans
- c. Chlamydia trachomatis
- d. Trichophyton rubrum
- e. Giardia lamblia
- Each of the following statements concerning Chlamydia trachomatis is correct EXCEPT:
- a. It is an important cause of nongonococcal urethritis.
- b. It is an important cause of subacute bacterial endocarditis. ✅
- c. It is the cause of lymphogranuloma venereum.
- d. It is an important cause of conjunctivitis.
- A 20-year-old woman presents with a history of vaginal discharge for the past 3 days. On pelvic examination, you see a mucopurulent exudate at the cervical os, and there is tenderness on palpation of the right fallopian tube. You do a Gram stain and culture on the cervical discharge. The culture is done on Thayer-Martin medium. Of the following, which findings are the MOST likely to be found?
- a. A Gram stain reveals many neutrophils and gram-variable rods, and culture on Thayer-Martin medium reveals ß-hemolytic colonies.
- b. A Gram stain reveals many neutrophils but no gram-negative diplococci are seen, and culture on Thayer-Martin medium reveals coagulase-positive colonies.
- c. A Gram stain reveals many neutrophils and spirochetes, and culture on Thayer-Martin medium reveals no colonies.
- d. A Gram stain reveals many neutrophils and gram-negative diplococci, and culture on Thayer-Martin medium reveals oxidase-positive colonies. ✅
- Regarding human immunodeficiency virus (HIV), which one of the following is MOST accurate?
- a. Both zidovudine and lamivudine block HIV replication by inhibiting cleavage of the precursor polypeptide by the virion-encoded protease.
- b. The Western blot test for antibodies to HIV has more false-positive results than the ELISA test.
- c. The antigenicity of the GAG protein of HIV is highly variable, which is a significant impediment to the development of a vaccine against HIV.
- d. The term viral load refers to the concentration of HIV RNA in the patient’s blood plasma. ✅
- Each of the following statements concerning chlamydiae is correct EXCEPT:
- a. Chlamydia trachomatis has multiple serotypes that can cause different diseases.
- b. Chlamydiae are strict intracellular parasites because they cannot synthesize sufficient adenosine triphosphate (ATP).
- c. Most chlamydiae are transmitted by arthropods. ✅
- d. Chlamydiae possess both DNA and RNA and are bounded by a cell wall.
- Which of the following statements about Transmission Electron Microscopy is not true.
- a. The beam is focused by electromagnetic lenses.
- b. The specimen must be stained with osmium or other heavy metal. ✅
- c. The specimens are placed in a high vacuum for viewing.
- d. The specimens must be sliced very thin, 20-100 nm in thickness.
- Phase Contrast microscopy
- a. Continuously changes the phase of the incident light from the condenser to improve contrast in the specimen.
- b. Uses circular filters in the condenser and objective to give contrast to parts of the cell with different refractive indices. ✅
- c. Uses special lenses to change the color of light passing through them.
- d. Uses special lenses to distinguish between solid and liquid phases of the cell.
- Place the structures of the compound light microscope in the order that light passes through them on the way to the observer’s eyes: (1) condenser, (2) ocular lens, (3) illuminator, (4) specimen, (5) objective lens.
- a. 2-1-4-5-3
- b. 3-5-4-1-2
- c. 2-5-4-1-3
- d. 3-1-4-5-2 ✅
- e. 3-4-1-5-2
- Most light microscope contain a/an…. that converges the light beam so that it passes through the specimen
- a. objective lens
- b. mechanical stage
- c. ocular lens
- d. condenser ✅
- e. iris diaphragm
- Light of… wavelength typically will result in…. resolving power.
- a. shorter, worse
- b. any, poor
- c. longer, better
- d. shorter, better ✅
- “Parfocal” refers to microscopes with multiple objectives where
- a. objectives are used in pairs for stereoscopic effects.
- b. sequential objectives increase power by a factor of two.
- c. each objective is positioned to be in focus at the same stage height. ✅
- d. each objective has the same working distance above the specimen.
- Regarding the Gram stain, which one of the following is the MOST accurate?
- a. If you forget to stain with the red dye (safranin or basic fuchsin), both gram-positive bacteria and gram-negative bacteria will appear blue.
- b. One reason why bacteria have a different color in this stain is because the gram-positive bacteria have lipid in their membrane, whereas gram-negative bacteria do not.
- c. After adding crystal violet and Gram’s iodine, both gram-positive bacteria and gram-negative bacteria will appear blue. ✅
- d. If you forget to heat-fix, both gram-positive bacteria and gram-negative bacteria will appear blue.
- Negative staining is useful for observing the presence of ..
- a. Endospores
- b. Motility
- c. Mycolic acid
- d. Flagella
- e. Capsule ✅
- In this type of microscopy, surface of a specimen is bombarded with electrons during sample preparation step.
- a. Phase-contrast Microscope
- b. Scanning Electron Microscope ✅
- c. Transmission Electron Microscope
- d. Bright-light Microscope
- e. Dark field Microscope
- When a microscopic image is brightly illuminated, but is surrounded by a black field, what type of microscope is being used?
- a. Dark-field ✅
- b. Bright-field
- c. Fluorescence
- d. Phase-contrast
- e. Electron
- Monochromatic light is sometimes used to increase the resolution of light microscopes. Light of which color below would give you the best resolution?
- a. Green
- b. Blue ✅
- c. Orange
- d. Red
- While viewing the stained slides in 100x, a drop of oil is placed between the tip of the oil immersion lens and the specimen on a glass slide. What is the purpose of using the oil.
- a. The oil increases the degree of refraction.
- b. The oil prevents light from bending as it passes through the specimen. ✅
- c. The oil increases the total power of magnification.
- d. The oil decreases the numerical aperture.
- e. The oil helps to illuminate the specimen.
- Differential Interference Contrast microscopy
- a. compares two identical specimens on the same microscope.
- b. illuminates the specimen with light of two different colors.
- c. illuminates the specimen with both reflected and transmitted light.
- d. illuminates the specimen with light of two different phases. ✅
- Each of the following statements concerning malaria is correct EXCEPT:
- a. Early in infection, sporozoites enter hepatocytes.
- b. Release of merozoites from red blood cells causes periodic fever and chills.
- c. The female Anopheles mosquito is the vector.
- d. The principal site of gametocyte formation is the human gastrointestinal tract. ✅
- Black water fever is a special manifestation of malaria caused by;
- a. P. falciparum ✅
- b. P. malariae
- c. P. vivax
- d. P. ovale
- All of the following statements about mosquitoes are true except:
- a. Only female mosquitoes suck human blood.
- b. They are definitive host in Filaria ✅
- c. Its life cycle is completed in 3 weeks
- d. They are definitive host in Malaria
- Malaria is transmitted by a bite of female Anopheles mosquito, but what causes the disease?
- a. A Bacteria
- b. A parasite ✅
- c. An yeast
- d. A virus
- Which one of the following agents can be used to prevent malaria?
- a. Chloroquine ✅
- b. Praziquantel
- c. Mebendazole
- d. Inactivated vaccine
- Which of the following mosquito is responsible for malaria transmission?
- a. Anopheles ✅
- b. Culex tritaeniorhynchus
- c. Aedes albopictus
- d. Aedes aegypti
- Which of the following statement(s) regarding Plasmodium falciparum are true?
- a. causes benign tertian malaria
- b. is associated with recurrent relapses after initial treatment because of liver hypnozoites
- c. is the only malarial parasite causing greater than 20% parasitaemia ✅
- d. is the only cause of cerebral malaria
- The word “malaria” comes from which two medieval Italian words?
- a. Evil insect
- b. Painful breathing
- c. Bad air ✅
- d. Dirty water
- Can malaria be transmitted from person to person?
- a. Yes, you can get malaria touching a person with malaria
- b. Yes, you can get malaria sharing space with malaria patients
- c. No, except from mother to child during pregnancy ✅
- d. Yes, you can get malaria through kissing
- After sporozoite gain entrance to human body it undergoes developmental cycle first in liver than in RBC, only after which fever is seen. This incubation period varies between plasmodium species, and ………….. species has longest incubation period.
- a. P. ovale
- b. P. vivax
- c. P. falciparum ✅
- d. P. malariae
- In malaria, the form of plasmodia that is transmitted from mosquito to human is the:
- a. Hypnozoite
- b. Merozoite
- c. Sporozoite ✅
- d. Gametocyte
- A 35-year-old man comes to the emergency department complaining of high fever, chills, severe headache, and confusion. He has recently returned from Africa. A peripheral blood smear reveals multiple ring structures and crescent-shaped gametes. Which of the following organisms is the most likely cause?
- a. Plasmodium falciparum ✅
- b. Plasmodium vivax
- c. Plasmodium malariae
- d. Plasmodium ovale
- e. Leishmania species
- Children at day care centers in the United States have a high rate of infection with which one of the following?
- a. Enterobius vermicularis ✅
- b. Necator americanus
- c. Entamoeba histolytica
- d. Ascaris lumbricoides
- Each of the following statements concerning Strongyloides stercoralis is correct EXCEPT:
- a. S. stercoralis produces filariform larvae.
- b. Migrating larvae of S. stercoralis induce a marked eosinophilia.
- c. S. stercoralis is acquired by ingestion of eggs. ✅
- d. S. stercoralis undergoes a free-living life cycle in soil.
- Each of the following statements concerning hydatid cyst disease is correct EXCEPT:
- a. The disease is caused by Echinococcus granulosus.
- b. The disease is caused by a parasite whose adult form lives in dogs’ intestines.
- c. The disease occurs primarily in tropical Africa. ✅
- d. The cysts occur primarily in the liver.
- The skin test used for the diagnosis of Hydatid cyst is known as:
- a. Schick test
- b. Casoni test ✅
- c. Montenegro test
- d. Dick test
- A 13-year-old boy from India was brought to the emergency room with a prolapsed rectum. Examination of the rectum reveals small worms that resemble whips attached to the mucosa. A stool sample reveals eggs that are barrel shaped, with bipolar plugs. Which of the following is the most likely cause?
- a. Ascaris lumbricoides
- b. Entamoeba histolytica
- c. Echinococcus granulosus
- d. Trichuris trichiura ✅
- e. Enterobius vermicularis
- f. Giardia lamblia
- Each of the following parasites passes through the lung during human infection EXCEPT:
- a. Strongyloides stercoralis
- b. Wuchereria bancrofti ✅
- c. Ascaris lumbricoides
- d. Necator americanus
- Larval stage of Taenia solium is called
- a. cysticercus cellulosae ✅
- b. hydatid cyst
- c. cysticercus bovis
- d. cysticercoid
- At a school nurse’s request, a clinic in rural South Carolina sees a 9-year-old girl who appears listless and inattentive, although hearing and visual testing has been within normal limits. The physician finds the child thin, with the “potbelly” of malnutrition, and orders a fecal exam and CBC. The CBC reveals a microcytic, hypochrornic anemia, and the fecal exam detects brown, oval nematode eggs approximately 65 microns in size, too numerous to count. What was the most likely means by which this child was infected?
- a. Ingestion of ova
- b. Ingestion of cysts in muscle
- c. Skin penetration by larvae ✅
- d. Ingestion of larvae
- e. Mosquito transmission of sporozoites
