Advanced Antibacterial Agents: Mechanisms, Resistance, and Clinical Applications Quiz

1. Which two antibiotics inhibit cell membrane synthesis by blocking Peptidoglycan Synthesis (not just cross-linking)?

Azithromycin and Doxycycline

Gentamicin and Levofloxacin

Penicillin and Cephalexin

Vancomycin and Bacitracin specifically target cell membrane synthesis by inhibiting Peptidoglycan synthesis, making them effective against a variety of bacteria. Penicillin, Cephalexin, Azithromycin, Doxycycline, Gentamicin, and Levofloxacin have different mechanisms of action and do not inhibit Peptidoglycan synthesis in the same way.

Explanation

Vancomycin and Bacitracin specifically target cell membrane synthesis by inhibiting Peptidoglycan synthesis, making them effective against a variety of bacteria. Penicillin, Cephalexin, Azithromycin, Doxycycline, Gentamicin, and Levofloxacin have different mechanisms of action and do not inhibit Peptidoglycan synthesis in the same way.

2. Guy developed diffuse flushing, thrombophlebitis after being treated for MRSA/C.difficile (after metronidazole failed in latter case) what are 2 other feared complications and how bugs become resistant to this antibiotic?

A: Vancomycin can cause hypertension and hypokalemia as complications

B: Bugs become resistant to vancomycin by increasing their uptake of the drug

C: Red-man syndrome can be prevented by increasing the dose of vancomycin

Explanation: Vancomycin is associated with nephrotoxicity and ototoxicity as feared complications. Bugs can become resistant to vancomycin by altering their binding site. Red-man syndrome can be prevented by pre-treatment with antihistamines and slow infusion rate.

Explanation

Explanation: Vancomycin is associated with nephrotoxicity and ototoxicity as feared complications. Bugs can become resistant to vancomycin by altering their binding site. Red-man syndrome can be prevented by pre-treatment with antihistamines and slow infusion rate.

3. Which antibiotic and in what form is used to treat a draining sinus tract in the cervicofacial region that discharges yellow-sulfur granules to kill the organism?

Ciprofloxacin in liquid form.

Azithromycin in intravenous form.

Amoxicillin in tablet form.

Penicillin is the antibiotic of choice for treating Actinomyces infections, which can cause draining sinus tracts in the cervicofacial region. It is important to use the correct form (Penicillin G(IV,IM) or Penicillin V(Oral)) for effective treatment.

Explanation

Penicillin is the antibiotic of choice for treating Actinomyces infections, which can cause draining sinus tracts in the cervicofacial region. It is important to use the correct form (Penicillin G(IV,IM) or Penicillin V(Oral)) for effective treatment.

4. How do penicillin G/V work and what are possible complications?

They disrupt the bacterial cell membrane causing lysis

They interfere with bacterial DNA replication by binding to DNA gyrase

They inhibit protein synthesis in bacteria by targeting ribosomes

Penicillin G/V specifically target the cell wall synthesis process in bacteria, rather than protein synthesis, cell membrane disruption, or DNA replication. The correct answer explains their mechanism of action and possible complications associated with their use.

Explanation

Penicillin G/V specifically target the cell wall synthesis process in bacteria, rather than protein synthesis, cell membrane disruption, or DNA replication. The correct answer explains their mechanism of action and possible complications associated with their use.

5. How do aminopenicilins work and are they B-lactamase sensitive?

Aminopenicilins are not associated with pseudomembranous colitis

Aminopenicilins do not cause any rashes

Aminopenicilins are not sensitive to B-lactamase

Aminopenicilins are a subgroup of penicillins that are susceptible to B-lactamase enzymes. They are commonly associated with the development of Ampicilin rash, hypersensitivity reactions, and pseudomembranous colitis. It is important to be aware of these side effects when prescribing aminopenicilins.

Explanation

Aminopenicilins are a subgroup of penicillins that are susceptible to B-lactamase enzymes. They are commonly associated with the development of Ampicilin rash, hypersensitivity reactions, and pseudomembranous colitis. It is important to be aware of these side effects when prescribing aminopenicilins.

6. A patient with Gram+ cocci was given an antibiotic with Bulky R groups that block access of B-lactamase to B-lactam and inhibits cross-linking of Peptidoglycans in bacterial cell-wall, but instead of getting better symptoms, he only got worse and developed interstitial nephritis as a side effect of this drug. What happened?

The antibiotic caused excessive growth of Gram+ bacteria leading to worsening symptoms

The antibiotic had a direct toxic effect on the kidneys causing interstitial nephritis

The patient developed an allergic reaction to the antibiotic

The correct answer explains that the specific antibiotic given was not effective due to MRSA resistance, leading to worsening symptoms and the development of interstitial nephritis as a side effect.

Explanation

The correct answer explains that the specific antibiotic given was not effective due to MRSA resistance, leading to worsening symptoms and the development of interstitial nephritis as a side effect.

7. Which generation of cephalosporins is usually given for serious gram-negative infections resistant to other B-lactams?

4th generation cephalosporins like Cefepime

1st generation cephalosporins like Cephazolin

2nd generation cephalosporins like Cefuroxime

Ceftriaxone, a 3rd generation cephalosporin, is the preferred choice for serious gram-negative infections resistant to other B-lactams such as penicillins. It is commonly used in the treatment of various infections including Meningitis, Gonorrhea, and Disseminated Lyme disease.

Explanation

Ceftriaxone, a 3rd generation cephalosporin, is the preferred choice for serious gram-negative infections resistant to other B-lactams such as penicillins. It is commonly used in the treatment of various infections including Meningitis, Gonorrhea, and Disseminated Lyme disease.

8. Why is it generally not recommended to use Aminoglycosides with Cephalosporins due to their synergistic toxic effect on the kidney?

Aminoglycosides and Cephalosporins are known to cancel out each other's antimicrobial effects.

*Due to their SYNERGISTIC toxic effect on Kidney.(so modify doses and try to avoid combination in someone with renal problems).

Because the combination leads to a lower efficacy in treating streptococcal infections.

The combination of these two types of drugs often results in significant drug resistance development.

9. What can happen if a patient mixes alcohol with cephalosporin antibiotics for a UTI caused by Enterobacter?

Mixing alcohol with cephalosporin antibiotics can improve the antibiotic's efficacy against Enterobacter.

The patient may develop resistance to the antibiotic due to the alcohol interaction.

The patient may experience an allergic reaction to the cephalosporin antibiotic.

The correct answer explains the potential Disulfiram-like reaction due to the interaction between cephalosporins and alcohol, highlighting the importance of avoiding such combination to prevent adverse effects.

Explanation

The correct answer explains the potential Disulfiram-like reaction due to the interaction between cephalosporins and alcohol, highlighting the importance of avoiding such combination to prevent adverse effects.

10. Your patient developed hives+Autoimmune hemolytic anemia when he was treated with penicillin a while ago, now he has severe gram-negative rod infection which is aerobe like Pseudomonas, EnteroBacter (NOT Enterococcus), Klebsiella, and has severe renal failure. As the patient can't tolerate aminoglycosides, what is the drug of choice that works by binding to PBP3 and preventing peptidoglycan cross-linking?

Cephalexin

Amoxicillin

Levofloxacin

Aztreonam, from the Monobactam group, specifically targets Gram-negative, aerobic rods like Pseudomonas, EnteroBacter, and Klebsiella by binding to PBP3 and inhibiting peptidoglycan cross-linking. It is less susceptible to B-lactamases and has no cross-allergenicity with penicillins or cephalosporins. Cephalexin and amoxicillin are both B-lactam antibiotics and can trigger similar allergic reactions in patients with penicillin allergies. Levofloxacin, a fluoroquinolone, may not be the optimal choice for this specific infection.

Explanation

Aztreonam, from the Monobactam group, specifically targets Gram-negative, aerobic rods like Pseudomonas, EnteroBacter, and Klebsiella by binding to PBP3 and inhibiting peptidoglycan cross-linking. It is less susceptible to B-lactamases and has no cross-allergenicity with penicillins or cephalosporins. Cephalexin and amoxicillin are both B-lactam antibiotics and can trigger similar allergic reactions in patients with penicillin allergies. Levofloxacin, a fluoroquinolone, may not be the optimal choice for this specific infection.

11. Why would you administer Imipenem with Cilastatin and what is a safer alternative?

Ceftriaxone is a safer alternative to Imipenem for treating Gram-negative infections.

Vancomycin is a safer alternative to Imipenem for treating Gram-positive infections.

Trimethoprim-sulfamethoxazole is a safer alternative to Imipenem for treating anaerobic bacterial infections.

12. Why is aminoglycoside unique compared to other protein synthesis inhibitors?

Because it has fewer side effects compared to other antibiotics.

Because it is less effective in treating bacterial infections.

Because it targets DNA replication instead of protein synthesis.

Aminoglycosides are unique in that they directly kill bacteria, making them bactericidal, while other protein synthesis inhibitors only halt bacterial growth and division, known as being bacteriostatic.

Explanation

Aminoglycosides are unique in that they directly kill bacteria, making them bactericidal, while other protein synthesis inhibitors only halt bacterial growth and division, known as being bacteriostatic.

13. Why is it important to know that neomycin is not well-absorbed in the gastrointestinal tract?

It increases the risk of gastrointestinal bleeding.

It can lead to allergic reactions in the skin.

It can cause an increase in ammonia production in the intestines.

Neomycin not being well-absorbed in the GI tract is important because it allows for targeted treatment of hepatic encephalopathy and reduces infection risk in bowel surgery.

Explanation

Neomycin not being well-absorbed in the GI tract is important because it allows for targeted treatment of hepatic encephalopathy and reduces infection risk in bowel surgery.

14. You gave your patient Penicillin+X (For synergism) drug for treatment of severe gram-negative bacteria and your patient hasn't told you that she has been on Loop diuretics for a while and that she is pregnant, what is the possible complications and what is the mechanism of action of drug X?

The correct answer discusses the possible complications of giving Aminoglycoside as drug X, the mechanism of action, and the potential risks for both the patient and the unborn child who can be deaf. The incorrect answers are provided to test the understanding of different antibiotic classes and their potential side effects on pregnant patients.

Explanation

The correct answer discusses the possible complications of giving Aminoglycoside as drug X, the mechanism of action, and the potential risks for both the patient and the unborn child who can be deaf. The incorrect answers are provided to test the understanding of different antibiotic classes and their potential side effects on pregnant patients.

15. Drug X is very effective for treatment of Ricketsia/Chlamydia due to its ability to accumulate intracellularly, you also know that you don't give this drug pregnant women(Teratogen that causes teeth discoloration)+it can inhibit bone growth in babies under 8, your patient is 50 year old male with renal failure and you are giving him drug X to treat Lyme disease(Borrelia Burgdorferi), what is possible mechanism of resistance?

Alteration of ribosomal target sites by mutation

Decreased cell permeability to the drug

Activation of drug metabolizing enzymes

This question involves knowledge of the mechanism of action of Doxycycline and the possible resistance mechanisms that bacteria may develop against it. The correct answer relates to the role of plasmid-encoded transport pumps in increasing efflux or decreasing influx of Tetracyclines, making the bacteria resistant to the drug.

Explanation

This question involves knowledge of the mechanism of action of Doxycycline and the possible resistance mechanisms that bacteria may develop against it. The correct answer relates to the role of plasmid-encoded transport pumps in increasing efflux or decreasing influx of Tetracyclines, making the bacteria resistant to the drug.

16. Why would the doctor give mommy chloramphenicol and what is the mode of resistance/action of this drug?

Because chloramphenicol is known to boost the immune system of newborns.

Due to its ability to rapidly eliminate any drug interactions in the baby's system.

Because it is a widely accepted antibiotic for treating viral infections in infants.

17. What are the differences in mechanisms of actions between drug X and drug Y used to treat aspiration pneumonia and Pseudomembranous colitis, respectively?

Drug X, clindamycin, primarily targets gram-positive bacteria, while Drug Y, metronidazole, is more effective against gram-negative bacteria.

Drug X works by inhibiting cell wall synthesis in bacteria, while Drug Y disrupts bacterial cell membranes.

18. A patient with MRSA/VRE was given a drug that inhibits initiation complex formation by binding to the 50S subunit, causing them to develop restlessness, diarrhea, heavy sweating, tachycardia, and dilated pupils. What is another characteristic side effect of this drug and how do bugs become resistant?

The patient was given Vancomycin which can cause Red Man Syndrome. Bugs become resistant through altering cell wall components.

The correct answer details the specific drug (Linezolid), its characteristic side effects, and the resistance mechanism of bugs. The incorrect answers provide alternative scenarios with different drugs, side effects, and resistance mechanisms to test understanding.

Explanation

The correct answer details the specific drug (Linezolid), its characteristic side effects, and the resistance mechanism of bugs. The incorrect answers provide alternative scenarios with different drugs, side effects, and resistance mechanisms to test understanding.

19. If a patient with diarrhea, high fever, hyponatremia, and increased LFT is given macrolide for the treatment of legionella, what is the expected effect on PTT if the patient is on warfarin?

There will be no effect on PTT regardless of the macrolide used.

The PTT will increase only if the patient is also taking aspirin along with warfarin.

The PTT will decrease due to the interaction between macrolide and warfarin.

Macrolides can interact with warfarin by inhibiting P450 enzymes, leading to altered metabolism of warfarin and increased anticoagulant effect.

Explanation

Macrolides can interact with warfarin by inhibiting P450 enzymes, leading to altered metabolism of warfarin and increased anticoagulant effect.

20. HIV+ patient with multiple lung and brain abscesses due to Urease+, Aerobe which is gram+ acid fast bacteria, you give him therapy, his PTT increased and now he has uncontrolled bleeding, what happened?

You gave fluconazole for Candida, causing direct damage to the vascular endothelium leading to uncontrolled bleeding.

You gave vancomycin for MRSA, causing direct toxicity to the platelets leading to uncontrolled bleeding.

21. An HIV+ male with a CD4+ count below 100 developed ring-enhancing brain lesions and is being treated with pyrimethamine+Sulfadiazine, and receiving TMP/SMX for prophylaxis. What hematologic conditions is he likely to develop?

Hemolytic Anemia

Iron-deficiency Anemia

Thrombocytopenia

The patient is being given drugs that inhibit Folic acid synthesis, leading to disruptions in DNA synthesis which can result in Macrocytic Megaloblastic Anemia, leukopenia, and granulocytopenia.

Explanation

The patient is being given drugs that inhibit Folic acid synthesis, leading to disruptions in DNA synthesis which can result in Macrocytic Megaloblastic Anemia, leukopenia, and granulocytopenia.

22. Patient with UTI caused by P.Aeruginosa was given drug X and developed superinfection, ruptured his Achilles tendon, developed skin rash, headache, and muscle cramps. What can you tell about the age of the patient and what medications did he receive?

Patient is likely

Patient is likely >70 years old and was taking an antifungal medication.

Patient is likely between 50-60 years old and was taking a beta-blocker medication.

23. Why is Daptomycin not suitable for treating pneumonia and what are its other uses?

Daptomycin is known to cause liver toxicity as a side effect.

Daptomycin can only be administered intravenously.

Daptomycin is not effective against gram-negative bacteria.

Daptomycin is ineffective against gram-negative bacteria, does not cause liver toxicity, and can be administered intravenously. The main reason for not using it in pneumonia is its inactivation by surfactant.

Explanation

Daptomycin is ineffective against gram-negative bacteria, does not cause liver toxicity, and can be administered intravenously. The main reason for not using it in pneumonia is its inactivation by surfactant.

24. How would you treat a patient with Mycobacterium TB and what would you do for prophylaxis?

You would give Ciprofloxacin and Amoxicillin for treatment, and Rifampin for prophylaxis.

You would administer Vancomycin and Linezolid for treatment, and Pyrazinamide for prophylaxis.

You would use Azithromycin and Doxycycline for treatment, and Ethambutol for prophylaxis.

Correct treatment for Mycobacterium TB includes a combination of Rifampin, Isoniazid, Pyrazinamide, and Ethambutol (RIPE) while isoniazid is commonly used for prophylaxis in high-risk individuals.

Explanation

Correct treatment for Mycobacterium TB includes a combination of Rifampin, Isoniazid, Pyrazinamide, and Ethambutol (RIPE) while isoniazid is commonly used for prophylaxis in high-risk individuals.

25. What side effects could have been prevented by giving the patient B6 along with isoniazid for prophylaxis of TB?

Hepatotoxicity and increased drug concentrations

Microcytic Anemia with iron accumulation

Increased risk of Drug induced SLE

26. Why would you give rifabutin over rifampin to a guy who is HIV+?

Because rifampin is known to have a better safety profile in HIV+ individuals.

*Because Rifampin is potent inducer of P450>Less concentraiton(effect) of Other drugs(like HAART), rifabutin is less potent inducer of P450.

Because rifampin has fewer side effects compared to rifabutin.

Because rifabutin has a higher risk of drug interactions in HIV+ patients.

When treating HIV+ individuals, the choice between rifabutin and rifampin is based on their effects on P450 enzymes and drug interactions, not on side effects or safety profiles.

Explanation

When treating HIV+ individuals, the choice between rifabutin and rifampin is based on their effects on P450 enzymes and drug interactions, not on side effects or safety profiles.

27. Which side effect should you not worry about in a baby who is given a drug for prophylaxis of H.influenzae type B meningitis and in his family members who were given this drug for chemoprophylaxis?

Nausea and vomiting

Allergic reactions such as skin rash or itching

Headaches and dizziness

It is important to distinguish between harmless side effects like red-orange body fluids and more serious side effects like hepatotoxicity, P450 induction, and rapid resistance of the bug to the drug in question.

Explanation

It is important to distinguish between harmless side effects like red-orange body fluids and more serious side effects like hepatotoxicity, P450 induction, and rapid resistance of the bug to the drug in question.