Antimicrobial and Antiviral Agents Quiz

Overview of Antimicrobial and Antiviral Agents

• Protozoal diseases are difficult to treat, especially in underdeveloped tropical and subtropical countries.
• Mixed amebicides, such as metronidazole, are used to treat dysentery and work by damaging microbial DNA.
• Luminal amebicides, such as iodoquinol, are effective against the luminal trophozoite and cyst forms of asymptomatic amebiasis.
• Systemic amebicides, such as chloroquine, are used to treat intestinal wall infections and liver abscesses caused by amebas.
• Visceral type amebicides, such as sodium stibogluconate, are used to treat the most serious form of amebiasis (bloodstream) and are given parenterally.
• Antiviral agents, such as oseltamivir and zanamivir, are used to treat influenza A and B by inhibiting neuraminidase.
• Interferon and tenofovir are used to treat chronic hepatitis B and C by inhibiting viral replication.
• Acyclovir is used to treat herpes simplex virus and varicella-zoster virus infections by incorporating into viral DNA and causing chain termination.
• Highly active antiretroviral therapy (HAART) is used to decrease opportunistic infections in HIV patients.
• Vaccination against human papillomavirus (HPV) is the best protection from cervical cancer.
• Salicylic acid, TCA, and cryotherapy are used to remove warts caused by some types of HPV infection.
• Remdesivir is an antiviral agent used to treat COVID-19 by inhibiting SARS-CoV-2 RNA-dependent RNA polymerase, which is essential for viral replication.

Antitubercular Drugs and their Mechanisms of Action

• Mycobacteria are slender, rod-shaped bacteria that cause intracellular infections resulting in granulomatous lesions responsible for tissue destruction.
• Tuberculosis is the most common mycobacterial infection and is the leading cause of death worldwide from infection.
• Antitubercular drugs include ethambutol, isoniazid, pyrazinamide, and rifampicin, among others.
• Streptomycin, capreomycin, cycloserine, fluoroquinolones, and macrolides are second-line drugs used to treat tuberculosis.
• Dapsone, clofazimine, and rifampicin are drugs used to treat leprosy.
• Isoniazid is a potent antitubercular drug that is activated by a mycobacterial catalase-peroxidase and inhibits the enzymes enoyl acyl carrier protein reductase and β 3-ketoacyl-ACP synthase, which are essential for the synthesis of mycolic acid.
• Resistance to isoniazid is associated with mutations or deletions of mycobacterial catalase-peroxidase or varying mutations or overexpression of enoyl acyl carrier protein reductase.
• Adverse effects of isoniazid include mild increase in liver function test, hepatitis, idiosyncratic hepatotoxicity, peripheral neuropathy, loss of appetite, nausea, vomiting, stomach pain, mental abnormalities, convulsions, and optic neuritis.
• Rifampicin blocks transcription by interacting with the β subunit of bacterial DNA-dependent RNA polymerase and can cause elevated liver function tests, rash, epigastric distress, anorexia, nausea, vomiting, and diarrhea.
• Resistance to rifampicin can be caused by a mutation in the bacterial DNA-dependent RNA polymerase or decreased permeability.
• Pyrazinamide is a bactericidal antitubercular agent that inhibits fatty acid synthesis, and resistance to it can occur in strains lacking pyrazinamidase.
• Ethambutol is bacteriostatic and specific for most strains of M. tuberculosis, inhibiting arabinosyl transferase, an enzyme important for the synthesis of the mycobacterial arabinogalactan cell wall, and can cause optic neuritis and decreased urate excretion.