Antimalarial Drugs Quiz: Antiparasitic and AntiTB Medications

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Questions and Answers

________ are semisynthetic derivatives that have replaced artemisinins, which are particularly well suited for the treatment of severe P. falciparum malaria and now play a key role in the combination therapy of drug-resistant infections.

Chloroquine, hydroxychloroquine, primaquine

Dihydroartemisinin, artemether, artesunate (correct)

Halofantrine, lumefantrine, mefloquine

Atovaquone, proguanil, pyrimethamine

Please match the following:

Resistance to isoniazid usually results from = an inactivating mutation in the mycobacterial enzyme catalase-peroxidase, which converts isoniazid into its antimycobacterial form Resistance to antimycobacterial agents in general = results from chromosomal mutations Resistance to pyrazinamide is generally due to = mutations in the pyrazinamidase gene, which result in the inability to convert the prodrug into its active form Ethambutol resistance most often results from = mutations in the arabinosyl transferase gene, some of which cause overexpression of the target enzyme

Arrange the following events of the mechanism of action of chloroquine (alphabetical) with respect to their sequential occurence (numerical).

Accumulation of unpolymerized heme metabolite leads to active oxidative membrane damage and is toxic to the parasite = 4 Chloroquine thus poisons the parasite by preventing the detoxification of a toxic product of hemoglobin catabolism = 5 As a result, protonated chloroquine accumulates to high concentrations inside the parasite’s food vacuole, where it binds to ferriprotoporphyrin IX and inhibits the polymerization of the heme metabolite = 3 Once inside the acidic environment of the parasite’s food vacuole, chloroquine is rapidly protonated, making it to unable to diffuse out of the vacuole = 2

Chloroquine is highly effective against which of the following erythrocytic forms of plasmodial species/strains?

P. vivax, P. ovale, P. malariae, and chloroquine-resistant strains of P. falciparum Signup and view all the answers

Chloroquine-resistant plasmodia accumulate less chloroquine inside food vacuoles than chloroquine-sensitive plasmodia do. Which of the following statements are correct? SATA

All of the above Signup and view all the answers

Each tuberculous lesion in an infected lung can contain 108 bacteria. The frequency of mutants resistant to any single antimycobacterial drug is about 1 in 106 bacteria. What would be the frequency of mutants resistant to the coadministration of four antimycobacterial drugs?

10^24 Signup and view all the answers

______ itself does not accumulate appreciably in tissues during long-term administration, except in erythrocytes, where its concentration is about three times that in plasma.

Proguanil Signup and view all the answers

Because of the protection conferred by their walls, the____________ of E histolytica or G lamblia can survive days to weeks in the external environment and are responsible for transmission

cysts Signup and view all the answers

Resistant mutants are present in all microbial populations at approximately 1 in 106 and are rapidly selected out if _____________ is used as a single drug, especially in a patient with active infection

rifampin Signup and view all the answers

The nitro group of ____ is reduced by ferredoxin and the resulting products are responsible for disrupting the DNA helical structure which leads to inhibition of nucleic acid synthesis and causing strand breakage; _is amebicidal, bactericidal, trichomonacidal.

Metronidazole Signup and view all the answers

Hypnozoites are formed in the life cycle of which of the following plasmodial species?

Plasmodium vivax, Plasmodium ovale Signup and view all the answers

It has been established that electrons required for metronidazole activation are released from pyruvate by the activity of __________________ and transferred to the drug by a low-redox-potential carrier, ferredoxin.

pyruvate:ferredoxin oxidoreductase Signup and view all the answers

Match the following antitubercular drugs (numerical) with their most common side or adverse effects (alphabetical) as given below (scroll down to see). Use only the UPPER CASE alphabet (A-D) for your answer

Ethambutol = Optic neuritis Isoniazid = Peripheral neuropathy Pyrazinamide = Hepatitis Rifampin = . Harmless orange discoloration of body fluids Signup and view all the answers

Metronidazole is indicated for the treatment of

Amoebic dysentery due to Entamoeba histolytica Signup and view all the answers

Excystation occurs in which of the following organs:

Small intestine Signup and view all the answers

When a malarial parasite infects a red blood cell, its presence can be detected by the existence of a parasite protein on the cell’s surface. The immune system can then learn to recognize this protein and develop weapons to eliminate the infected red blood cells. Which of the following statements are correct with regard to malarial parasites’ ability to fool our immune system in recognizing and eliminating the infected RBC? SELECT ALL THAT APPLY.

All of the above Signup and view all the answers

What is the mechanism of non-bloody diarrhea caused by Giardia Lamblia?

Inhibition of absorption by adherence of the parasite to the enterocyte glycocalyx epithelium Signup and view all the answers

Recurrent malaria due to immunodeficiency, such as from corticosteroids, stress, or chemotherapy differs from the type that is usually seen in the immunocompetents. It is because the organisms did not come from the hypnozoite stage, but rather from an erythrocytic stage. This type of malaria is which of the following?

Recrudescent Signup and view all the answers

Patients with active tuberculosis and without a history of prior therapy are started:

A and B only Signup and view all the answers

Peripheral neuropathy is due to competitive inhibition by INH of pyridoxine in neurotransmitter synthesis and can be prevented by ______________ supplementation

pyridoxine Signup and view all the answers

Prolonged medication with suppressive doses occasionally causes all the following side effects. Which of the following could lead to a medical emergency?

widening of the QRS interval, and T-wave abnormalities Signup and view all the answers

Pyrazinamide is a prodrug; it must be converted to its active form, pyrazinoic acid, by the enzyme pyrazinamidase. It acts by

inhibiting FAS1, the enzyme that synthesizes the fatty acid precursors of mycolic acid Signup and view all the answers

The mechanism of action of Isoniazid is to:

target the FAS2 complex and inhibit mycolic acid synthesis Signup and view all the answers

The mechanism of action of Ethambutol is to:

decrease arabinogalactan synthesis by inhibiting the arabinosyl transferase Signup and view all the answers

When initially introduced, chloroquine was a first-line drug used against all types of malaria; however, it is now ineffective against most strains of P. falciparum in Africa, Asia, and South America. This is predominantly because of the following reasons: SATA

All of the above Signup and view all the answers

Which are the five first-line agents used to treat tuberculosis?

Ethambutol, Pyrazinamide, Isoniazid (INH), Rifampin, and Streptomycin Signup and view all the answers

Which of the following statements are correct about Rifampin? SATA (select all four)

Human RNA polymerase does not bind rifampin and is not inhibited by it Signup and view all the answers

Which of the following statements are correct regarding Isoniazid? SATA (select all three)

All of the above Signup and view all the answers

Which of the following is the mechanism of action of chloroquine?

Inhibits the polymerization of heme metabolism Signup and view all the answers

Which of the following statements are correct about Atovaquone? SATA

All of the above Signup and view all the answers

Which of the following drugs is a tissue schizonticide used to prevent relapse of Pasmodium vivax infections?

Primaquine Signup and view all the answers

Match the following qualifying antimalarial drugs for prevention in travelers (numerical) with their corresponding situations (alphabetical) as given below (scroll down to see). Use only the UPPER CASE alphabet (A-D) for your answer

Chloroquine (weekly) remains an appropriate agent for prophylaxis = in regions without resistant P falciparum Mefloquine (weekly) = in regions with P falciparum resistance to chloroquine Either Doxycycline or Malarone (atovaquone plus proguanil); both drugs must be taken daily = in areas with multidrug-resistant malaria Primaquine (daily for 14 d) or tafenoquine (single dose) is recommended = for terminal prophylaxis of P vivax and P ovale infections and is an alternative in primary prevention Signup and view all the answers

Study Notes