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Question 1
Correct
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What is the mechanism of action of penicillin antibiotics:
Your Answer: Inhibition of bacterial cell wall synthesis
Explanation:Penicillins and the other ß-lactam antibiotics are bactericidal. They produce their antimicrobial action by preventing cross-linkage between the linear peptidoglycan polymer chains that make up the bacterial cell wall. They, therefore, inhibit cell wall synthesis.The integrity of the ß-lactam ring is essential for antimicrobial activity. Many bacteria (including most Staphylococci) are resistant to benzylpenicillin and phenoxymethylpenicillin because they produce enzymes (penicillinases, ß-lactamases) that open the ß-lactam ring.
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This question is part of the following fields:
- Infections
- Pharmacology
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Question 2
Correct
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For which of the following infections is phenoxymethylpenicillin (penicillin V) primarily used?
Your Answer: Streptococcal tonsillitis
Explanation:Phenoxymethylpenicillin (penicillin V) is less active than benzylpenicillin but both have similar antibacterial spectrum. Because penicillin V is gastric-acid stable, it is suitable for oral administration, but should not be used for serious infections as absorption can be unpredictable and plasma concentrations can be variable. Its uses are:1. mainly for respiratory tract infections in children2. for streptococcal tonsillitis 3. for continuing treatment after one or more injections of benzylpenicillin when clinical response has begun. 4. for prophylaxis against streptococcal infections following rheumatic fever and against pneumococcal infections following splenectomy or in sickle-cell disease. It should not be used for meningococcal or gonococcal infections.
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This question is part of the following fields:
- Infections
- Pharmacology
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Question 3
Correct
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Dysuria and urinary frequency are symptoms of a 29-year-old woman. A urine dipstick is used to detect the presence of blood, protein, leucocytes, and nitrites in the urine. You diagnose a urinary tract infection and give antibiotics to the patient.In the United Kingdom, which of the following antibiotics has the highest percentage of E.coli resistance?
Your Answer: Trimethoprim
Explanation:In the United Kingdom, antibiotic resistance is becoming a significant factor in the treatment of urinary tract infections and pyelonephritis. E. coli (the main causative organism of both urinary tract infections and acute pyelonephritis) resistance to the following antibiotics in laboratory-processed urine specimens is:30.3 percent trimethoprim (varies by area from 27.1 to 33.4 percent )19.8 percent co-amoxiclav (varies by area from 10.8 to 30.7 percent )Ciprofloxacin (Cipro): 10.6% (varies by area from 7.8 to 13.7 percent )Cefalexin has a concentration of 9.9%. (varies by area from 8.1 to 11.4 percent )
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This question is part of the following fields:
- Infections
- Pharmacology
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Question 4
Incorrect
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In a ward round, you come across a patient's treatment chart prescribed an antibiotic to fight his infection. This antibiotic is a protein synthesis inhibitor.Which of the following antimicrobial drugs is prescribed to this patient?
Your Answer: Metronidazole
Correct Answer: Gentamicin
Explanation:Gentamicin, an aminoglycoside antibiotic, acts by binding to the 30S subunit of the bacterial ribosome inhibiting the binding of aminoacyl-tRNA and thus preventing initiation of protein synthesis.Vancomycin inhibits cell wall peptidoglycan formation by binding the D-Ala-D-Ala portion of cell wall precursors. Penicillins and cephalosporins are the major antibiotics that inhibit bacterial cell wall synthesis. They inactivate transpeptidases that help cross-link peptidoglycans in cell walls. Metronidazole and the other 5-nitroimidazole agents inhibit nucleic acid synthesis by forming toxic free radical metabolites in the bacterial cell that damage DNA. Ciprofloxacin inhibits prokaryotic enzymes topoisomerase II (DNA gyrase) and topoisomerase IV.
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This question is part of the following fields:
- Infections
- Pharmacology
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Question 5
Correct
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Question 6
Incorrect
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A 60-year-old male presents to the genitourinary clinic with dysuria and urinary frequency complaints. He has a past medical history of benign prostate enlargement, for which he has been taking tamsulosin. There is blood, protein, leucocytes, and nitrites on a urine dipstick. Fresh blood tests were sent, and his estimated GFR is calculated to be >60 ml/minute. A urinary tract infection (UTI) diagnosis is made, and he is prescribed antibiotics. Out of the following, which antibiotic is most appropriate to be prescribed to this patient?
Your Answer: Cefalexin
Correct Answer: Nitrofurantoin
Explanation:The NICE guidelines for men with lower UTIs are:1. Prescribe an antibiotic immediately, taking into account the previous urine culture and susceptibility results or avoiding antibiotics used previously that may have caused resistance 2. Obtain a midstream urine sample before starting antibiotics and send for urine culture and susceptibility – Review the choice of antibiotic when the results are available AND- change the antibiotic according to susceptibility results if the bacteria are resistant and symptoms are not improving, using a narrow-spectrum antibiotic wherever possibleThe first choice of antibiotics for men with lower UTIs is:1. Trimethoprim200 mg PO BD for seven days2. Nitrofurantoin100 mg modified-release PO BD for 3 days – if eGFR >45 ml/minuteIn men whose symptoms have not responded to a first-choice antibiotic, alternative diagnoses (such as acute pyelonephritis or acute prostatitis) should be considered. Second-choice antibiotics should be based on recent culture and susceptibility results.
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This question is part of the following fields:
- Infections
- Pharmacology
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Question 7
Correct
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In a ward round, you come across a patient's treatment chart prescribed an antibiotic to fight his infection. This antibiotic disrupts cell membrane function.Which of the following antimicrobial drugs is prescribed to this patient?
Your Answer: Nystatin
Explanation:Nystatin binds ergosterol (unique to the fungi cell membrane) and forms membrane pores that allow K+ leakage, acidification, and subsequent death of the fungus.Vancomycin inhibits cell wall peptidoglycan formation by binding the D-Ala-D-Ala portion of cell wall precursors. Flucloxacillin inhibits the synthesis of bacterial cell walls. It inhibits cross-linkage between the linear peptidoglycan polymer chains that make up a major component of the cell wall of Gram-positive bacteria. Trimethoprim inhibits bacterial dihydrofolate reductase.Isoniazid decreases the synthesis of mycolic acids in mycobacteria.
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This question is part of the following fields:
- Infections
- Pharmacology
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Question 8
Correct
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A patient presents with a cough, productive of green sputum and fever. He was commenced on antibiotics 4 days earlier, but his condition has worsened. There is a documented history of penicillin allergy, and the GP prescribed erythromycin.Erythromycin exert its pharmacological effect by binding to?
Your Answer: The 50S subunit of the bacterial ribosome
Explanation:Macrolides are bacteriostatic antibiotics. They act by binding to the 50S subunit of the bacterial ribosome and inhibit translocation, therefore, inhibiting protein synthesis.
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This question is part of the following fields:
- Infections
- Pharmacology
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Question 9
Correct
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You're currently treating an infection in a patient and trying to figure out which antibiotic would be best.Which of the following antimicrobial drugs inhibits the formation of cell walls?
Your Answer: Cefuroxime
Explanation:Cefuroxime and other cephalosporin antibiotics are bactericidal ß-lactam antibiotics. They work similarly to penicillins in that they prevent cross-linking between the linear peptidoglycan polymer chains that make up the bacterial cell wall. As a result, they prevent the formation of cell walls.The following is a summary of the various mechanisms of action of various types of antimicrobial agents:1) Inhibition of cell wall synthesisPenicillinsCephalosporinsVancomycin2) Disruption of cell membrane functionPolymyxinsNystatinAmphotericin B3) Inhibition of protein synthesisMacrolidesAminoglycosidesTetracyclinesChloramphenicol4) Inhibition of nucleic acid synthesisQuinolonesTrimethoprim5-nitroimidazolesRifampicin5) Anti-metabolic activitySulphonamidesIsoniazid
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This question is part of the following fields:
- Infections
- Pharmacology
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Question 10
Incorrect
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Herpes simplex encephalitis has a predilection for which of the following sites:
Your Answer: Limbic lobe
Correct Answer: Temporal lobe
Explanation:Herpes simplex virus is the most common cause of infective encephalitis and has a predilection for the temporal lobes. Herpes simplex is transmitted through direct contact. It invades skin locally producing skin vesicles by its cytolytic activity.
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This question is part of the following fields:
- Infections
- Microbiology
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Question 11
Correct
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Regarding aciclovir, which of the following statements is INCORRECT:
Your Answer: Aciclovir eradicates herpes simplex virus from the body.
Explanation:Aciclovir is active against herpesviruses but does not eradicate latent virus.
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This question is part of the following fields:
- Infections
- Pharmacology
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Question 12
Correct
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Flucloxacillin is used first line for all of the following infections EXCEPT for:
Your Answer: Otitis media
Explanation:Flucloxacillin is used first line for treatment of widespread impetigo infection, cellulitis, mastitis, osteomyelitis, septic arthritis, severe erysipelas, severe/spreading otitis externa and infective endocarditis caused by staphylococci. Amoxicillin is first line for acute otitis media.
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This question is part of the following fields:
- Infections
- Pharmacology
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Question 13
Incorrect
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Which of the following statements is correct regarding gentamicin?
Your Answer: Hepatotoxicity is the most common adverse effect at toxic doses.
Correct Answer: Gentamicin is ineffective against anaerobic bacteria.
Explanation:Gentamicin is the aminoglycoside of choice in the UK and is a parenterally administered, broad spectrum antibiotic typically used for moderate to severe gram negative infections. However, it is inactive against anaerobes. There is poor activity against haemolytic streptococci and pneumococci. It is usually given in conjunction with a penicillin or metronidazole (or both) when used for the blind treatment of undiagnosed serious infections. Nephrotoxicity and ototoxicity are the main toxic effects due to damage to the vestibulocochlear nerve (CN VIII).It is contraindicated in myasthenia gravis and should be used with great care in renal disease as it may result in accumulation and a higher risk of toxic side effects.
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This question is part of the following fields:
- Infections
- Pharmacology
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Question 14
Correct
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Aldin is a 24-year-old male patient who arrives at the emergency department diagnosed with psittacosis based on his symptoms and history of being a pigeon enthusiast. Which of the following is the causative bacteria of psittacosis?
Your Answer: Chlamydia psittaci
Explanation:Chlamydia psittaci is a microorganism that is commonly found in birds. These bacteria can infect people and cause psittacosis. Psittacosis is an infectious disease that may cause high fever and pneumonia associated with headaches, altered mental state, and hepatosplenomegaly.
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This question is part of the following fields:
- Infections
- Microbiology
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Question 15
Incorrect
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Regarding drug interactions with erythromycin, which of the following statements is INCORRECT:
Your Answer: Erythromycin increases the risk of QT-interval prolongation in patients taking drugs that increase the QT interval.
Correct Answer: Erythromycin decreases plasma levels of warfarin.
Explanation:Erythromycin and clarithromycin inhibit cytochrome P450-mediated metabolism of warfarin, phenytoin and carbamazepine and may lead to accumulation of these drugs. There is an increased risk of myopathy (due to cytochrome P450 enzyme CYP3A4 inhibition) if erythromycin or clarithromycin is taken with atorvastatin or simvastatin. Erythromycin increases plasma concentrations of theophylline, and theophylline may also reduce absorption of oral erythromycin. All macrolides can prolong the QT-interval and concomitant use of drugs that prolong the QT interval is not recommended.
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This question is part of the following fields:
- Infections
- Pharmacology
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Question 16
Incorrect
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A young female was diagnosed with a urinary tract infection and was sent home with medications. However, after 48 hours of discharge, she returned to the hospital because there had been no relief from her symptoms. She is pregnant in her second trimester. The urine sensitivity test report is still unavailable. Fresh blood tests were sent, and her estimated GFR is calculated to be >60 ml/minute. She was prescribed nitrofurantoin 100 mg modified-release orally twice a day for two days.Out of the following, which antibiotic is most appropriate to be prescribed to this patient?
Your Answer: Co-amoxiclav
Correct Answer: Cefalexin
Explanation:The NICE guidelines for pregnant women with lower UTIs are:1. Prescribe an antibiotic immediately, taking into account the previous urine culture and susceptibility results or avoiding past antibiotics that may have caused resistance2. Obtain a midstream urine sample before starting antibiotics and send for urine culture and susceptibility – Review the choice of antibiotic when the results are available – change the antibiotic according to susceptibility results if the bacteria are resistant, using a narrow-spectrum antibiotic wherever possibleThe first choice of antibiotics for pregnant women aged 12 years and over is:1. Nitrofurantoin100 mg modified-release PO BD for 3 days – if eGFR >45 ml/minuteThe second-choice (no improvement in lower UTI symptoms on first-choice for at least 48 hours, or when first-choice is not suitable) are:1. Amoxicillin 500 mg PO TDS for seven days (ONLY if culture results available and susceptible)2. Cefalexin500 mg BD for seven daysAlternative second-choices – consult local microbiologist, choose antibiotics based on culture and sensitivity results
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This question is part of the following fields:
- Infections
- Pharmacology
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Question 17
Correct
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Regarding gentamicin, which of the following statements is INCORRECT:
Your Answer: Gentamicin typically causes acute glomerulonephritis in toxicity.
Explanation:Gentamicin is the aminoglycoside of choice in the UK and is used widely for the treatment of serious infections. It has a broad spectrum but is inactive against anaerobes and has poor activity against haemolytic streptococci and pneumococci. When used for the blind therapy of undiagnosed serious infections it is usually given in conjunction with a penicillin or metronidazole (or both). The main toxic effects are nephrotoxicity and ototoxicity due to damage to the vestibulocochlear nerve (CN VIII).Gentamicin is contraindicated in myasthenia gravis and should be used with caution in renal disease which may result in accumulation and a greater risk of toxic side effects.
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This question is part of the following fields:
- Infections
- Pharmacology
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Question 18
Incorrect
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A 6-year-old girl is brought into the paediatric emergency room by her mother in a state of high-grade fever and extreme irritability. She is also reluctant to urinate as it is associated with lower abdominal pain and stinging. She has no history of any UTIs requiring antibiotics in the past 12 months. The urine sensitivity test report is still unavailable. A clean catch urine sample is taken for urine dipstick, which reveals the presence of blood, protein, leukocytes and nitrites. Fresh blood tests were sent, and her estimated GFR is calculated to be 40 ml/minute. Out of the following, which antibiotic is most appropriate to be prescribed to this patient?
Your Answer: Cefalexin
Correct Answer: Trimethoprim
Explanation:The NICE guidelines for children and young people under 16 years lower UTIs are:1. Get a urine sample before antibiotics are taken, and do a dipstick test OR send for culture and susceptibility2. Assess and manage children under 5 with lower UTI with fever as recommended in the NICE guideline on fever in under 5s.3. Prescribe an immediate antibiotic prescription and take into account the previous urine culture and susceptibility results, previous antibiotic use, which may have led to resistant bacteria4. If urine culture and susceptibility report is sent- Review the choice of antibiotic when the results are available AND- change the antibiotic according to susceptibility results if the bacteria are resistant and symptoms are not improving, using a narrow-spectrum antibiotic wherever possibleThe choice of antibiotics for non-pregnant young people under 16 years with lower UTI is summarised below:1. Children under 3 months:- Refer to paediatric specialist and treat with intravenous antibiotic in line with NICE guideline on fever in under 5s2. Children over 3 months: – First-choice Nitrofurantoin – if eGFR >45 ml/minuteTrimethoprim – (if low risk of resistance*)- Second-choice (no improvement in lower UTI symptoms on first-choice for at least 48 hours, or when first-choice not suitable)Nitrofurantoin – if eGFR >45 ml/minute and not used as first-choiceAmoxicillin (only if culture results available and susceptible)Cefalexin
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This question is part of the following fields:
- Infections
- Pharmacology
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Question 19
Correct
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A patient allergic to penicillin and with marked cellulitis presents and you decide to start him on erythromycin.Which statement about macrolide antibiotics is true?
Your Answer: They are actively concentrated within leukocytes
Explanation:Macrolide antibiotics are bacteriostatic. They act by binding to the 50S subunit of the bacterial ribosome inhibit protein synthesis. Macrolide antibiotics are actively concentrated within leukocytes, because of this, they are transported into the site of infection.Macrolide antibiotics are not effective in meningitis as they do not penetrate the central nervous system well. They are mainly against Gram-positive organisms and can be used as an alternative in patients with penicillin allergy.
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This question is part of the following fields:
- Infections
- Pharmacology
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Question 20
Incorrect
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Amoxicillin is used first line for all of the following infections EXCEPT for:
Your Answer:
Correct Answer: Cellulitis
Explanation:Amoxicillin is used first line for low to moderate severity community acquired pneumonia, exacerbations of chronic bronchitis, for acute otitis media, for acute sinusitis, for oral infections/dental abscess, for Listeria meningitis (in combination with another antibiotic), for infective endocarditis (in combination with another antibiotic) and for H. Pylori eradication (in combination with metronidazole/clarithromycin and a PPI). Flucloxacillin is used first line for acute cellulitis.
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This question is part of the following fields:
- Infections
- Pharmacology
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SESSION STATS - PERFORMANCE PER SPECIALTY
