AntiM

A 35-year-old woman with a history of type 2 diabetes presents to her primary care physician with fever and dysuria (low urine production). She is started on a medication that has the potential to cause tendon rupture. What is the mechanism of action for the drug that was started?

• Inhibition of bacterial cell wall synthesis

• Inhibition of DNA gyrase

• Inhibition of RNA synthesis

• Inhibition of the 30s ribosome

Which one of the following pairs of "drug mechanism" is most accurate?

• Streptomycin: miscoding in bacterial protein synthesis

• Ritonavir: inhibition of reverse transcriptase in HIV

• Nystatin: decreased synthesis of ergosterol in fungal cell membranes
  
  

• Tetracycline:inhibits the activity of peptidyltransferasein bacterial protein synthesis
  
  

• Vancomycin: inhibits cross-linking of peptidoglycan chains in cell-wall synthesis

Answer explanation

Answer: A. Aminoglycosides (gentamicin, streptomycin) are bactericidal inhibitors of
protein synthesis. They bind to the 30s ribosomal subunit to block initiation, cause miscoding, and may prevent elongation. Ritonavir inhibits HIV protease (1101 reverse transcriptase); nystatin interacts with ergosterol to form artifical membrane "pores" (azole antifungals inhibit ergosterol synthesis); tetracyclines prevent binding of aminoacyltRNA (chloramphenicol inhibits peptidyltransferase); beta-lactams inhibit cross-linking of peptidoglycan chains in bacterial cell-wall synthesis

Highly active antiretroviral therapy (HAART) in HIV infection is associated with which
of the following?

• A decrease in viral mRNA copies in blood
  
  

• A decrease in the rate of emergence of drug resistance

• A decrease in the rate of emergence of drug resistance

• A reduced incidence of opportunistic infections

• All of the above

Answer explanation

Answer: E. HAART in the management of HIV infection is reported in many but not all
patients to decrease viral load, increase CD4 cells, slow disease progression, and reduce
opportunistic infections. However, in terms of the chemotherapy of AIDS, the word cure
has little meaning. Discontinuance of HAART, after suppression of viral RNA copies
below the sensitivity of the best current methods of analysis, is followed by the reemergence of detectable viral RNA in the blood within a few months.

Which of the following are considered an expected side effect of  reactions to the medications used to treat TB disease?

• Vomiting

• Orange urine, saliva, sweat, or tears  

• Fever for 3 or more days

• Skin Rash

Answer explanation

A. Vomiting
Vomiting is not usually an expected side effect but can occur as a sign of medication intolerance or toxicity. Persistent vomiting should be reported to a healthcare provider because it may indicate a serious reaction or liver problems.

B. Orange urine, saliva, sweat, or tears
This is a well-known and expected side effect of rifampin, one of the primary drugs used to treat TB. Rifampin causes bodily fluids to turn an orange-red color. Although it looks alarming, it is harmless and temporary.

C. Fever for 3 or more days
A prolonged fever is not a typical side effect and may suggest an infection or an adverse reaction to the medication. This requires prompt medical evaluation.

D. Skin rash
A rash can indicate an allergic reaction to TB medications, which can be mild or severe. Any rash should be evaluated by a healthcare provider because it may require stopping or changing the treatment.

An infectious disease is defined as an illness due to a pathogen or its toxic product that arises through transmission from which of the following sources?

• An infected person only

• An infected person or an infected animal only

• A contaminated inanimate object only

• An infected person, an infected animal, or a contaminated inanimate object

Answer explanation

An infectious disease arises from a pathogen or its toxic product transmitted from various sources, including infected people (human-to-human transmission), infected animals (zoonotic transmission), and contaminated inanimate objects (fomites). All these sources can play a role in spreading infectious diseases.

An infectious disease is defined as an illness due to a pathogen or its toxic product that arises through transmission from which of the following sources?

• An infected person only.

• An infected person or an infected animal only.

• A contaminated inanimate object only.

• An infected person, an infected animal, or a contaminated inanimate object.

Answer explanation

An infectious disease is defined as an illness due to a pathogen or its toxic product, which arises through transmission from an infected person, an infected animal, or a contaminated inanimate object to a susceptible host

In the context of antimicrobial activity measurements, if an antibiotic concentration results in a 1,000-fold reduction in bacterial density at 24 hours, this measurement corresponds to the:

• Minimum Inhibitory Concentration (MIC)

• Minimum Bactericidal Concentration (MBC)

• Time above Minimum Inhibitory Concentration (T>MIC)

• Post-Antibiotic Effect (PAE)

Answer explanation

The Minimum Bactericidal Concentration (MBC) is the concentration of a drug that results in a 1,000-fold reduction in bacterial density at 24 hours (bacteriocidality). The MIC is the lowest concentration that inhibits visible growth (bacteriostasis)

A 65-year-old female presents to the clinic with signs and symptoms consistent with community-acquired pneumonia (CAP). She has no known comorbidities or recent antibiotic use. Local pneumococcal resistance rates are reported as low (<25%). Which of the following would be an appropriate first-line empiric treatment option for CAP in this patient?

• Amoxicillin

• Aztreonam

• Doxycycline

• Ceftriaxone

Answer explanation

For empiric treatment of Community Acquired Pneumonia (CAP) in patients with no comorbidities or recent use of macrolides/doxycycline, doxycycline or a macrolide (if local resistance is low) are considered drugs of first choice

Beta-lactam antibiotics, such as penicillin, exert their bactericidal effect primarily by mimicking the D-Ala-D-Ala terminus of the peptidoglycan precursor and covalently binding to which essential bacterial enzyme?

• Dihydrofolate reductase

• DNA gyrase

• Penicillin-Binding Proteins (PBPs)/Transpeptidases

• Pyruvyl transferase (MurA)

Answer explanation

Beta-lactam antibiotics inhibit the transpeptidase enzymes, also known as Penicillin-Binding Proteins (PBPs), which catalyze cross-links between adjacent glycan chains during cell wall synthesis

Methicillin-resistant Staphylococcus aureus (MRSA) often achieves resistance to beta-lactams (e.g., methicillin, cephalosporins) primarily through which mechanism?

• Overexpression of the ABC efflux pumps

• Production of extended-spectrum beta-lactamases (ESBLs)

• Acquisition of a mutated PBP (PBP2a) which prohibits beta-lactam access to its active site.

• Decreased permeability due to porin mutations.

Answer explanation

MRSA strains have a mutated PBP (PBP2a, coded by the mecA gene) that prohibits beta-lactam antibiotics from accessing its active site, conferring resistance